Then awhile later, as I sat in the hot humid air, I saw what looked like a wide column that extended from the forest into the cloud (pic below). This was not a hovering cloud, but a set of vertical pathways from hill to cloud. Was that transpiration going up ?

It evolved in shape - a while later it was like a column or plume..

Then that column disappeared, and I was just watching the clouds roll over the mountain. I’ve been lately doing more analyzing of the small water cycle from satellite data generated by others, looking for interesting patterns. It would be cool, I thought to do some more observational research to see what phenomena I might stumble upon. So I sat there much longer than I normally would - watching the clouds.

As I continued to munch on some exotically marine flavored snacks, nothing happened for awhile. Then another cloud popped up in between the forest and the higher clouds above. Then it disappeared, blowing up the slope to join the higher up clouds. I watched the landscape for awhile. And then another cloud again formed before my eyes between the higher clouds and the forests.

This didn’t fit my existing ideas how things worked. I had imagined that the trees transpire and create clouds above them. But I hadn’t thought there cloud pulsing effect. It seemed every once in awhile, a cloud suddenly emerge into form.

My guess as to what was happening is that the forest is putting out a lot of moisture, and there is also humidity fluctuations. And just when there are places where the relative humidity goes over 100% then some of the water will condense. They start growing in size, and then turbulence in the air blows them around, so they can run into other growing droplets and get much bigger, enough to then be stable. At smaller sizes, they can evaporate again. And so this bumping around causes a local area to have suddenly a lot of condensed water vapor, while around that the water vapor is still in vapor form.

I am curious has anyone run across a description of this ‘transpirational cloud pulsing’ phenomenon before.? Has anyone else seen it? Have scientists studied it?

I watched longer, and I then began to realize that it looked like the transpirational clouds would move upwards, and get spread out in front of the mountain. It looked in fact as if this transpiration would over time form these plumes, that would then spread out into the clouds before me. It looked like how smoke from a forest fire gets blown up into air and then the wind spreads it out into this wide expanse of smoke. Is that cloud that takes up most of the picture below, have a really large part coming from that plume arising from the forest. It was moving slowly enough, that it might be made up of a hundred transpirational pulses.

When I scanned mountains further away in another direction, it seemed that maybe that is what was happening, although I couldn’t be sure. It looked like the forests were exhaling a transpiration plumes that would turn into clouds spread out. In the picture below, it seems the whiter clouds just above the mountains are coming from the exhalation. The diagonal slant of the clouds might be the wind spreading out that plume.

I made a short video, where you can see the transpiration rising https://youtube.com/shorts/e-LcGaEEjhI . Or see the video on the Climate Water Project Instagram account.

Curious if any readers have interpretations of what I saw. And also has anyone else noticed these transpirational plumes, when looking at forests and mountains in your area, and whether they then turn into an expanse of clouds?

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[Aboriginal painting of water and rain]

If an organism’s brain tried to run the whole organism it would run into problems, too many things to coordinate. To function it needs modularity, autonomy at different size scales.

The body is a good example. A cell is a small autonomous system inside the larger body. It produces its own energy, builds proteins, transports materials, removes waste, repairs damage, responds to signals, and maintains its internal conditions. There are thousands of processes happening inside a cell at any given moment, and most of them never need to be coordinated by the brain. The brain does not tell a mitochondrion when to produce ATP, or a ribosome when to make a protein, or every cell membrane when to open and close an ion channel. The cell handles these things itself. It receives information from the rest of the body, but it has its own machinery for interpreting that information and responding to it.

This creates a division of responsibility. The body deals with some problems at the multiple levels of both organs and cells. Each level has its own autonomy and some ability to self-maintain and self-repair.

Complex systems function better with modularity. Manlio De Domenico’s recent article in Complexity Thoughts goes into the importance of modularity to living architectures. Modularity gives the system autonomy at different size scales. Each part has the ability to self-adjust, self-repair, and function on its own. It doesn’t have to wait for some global brain to tell it what to do. That would become impossible anyway. There is simply too much to coordinate at the larger level. As a system becomes more complex, the amount of information grows, the number of interactions grows, and the problem of controlling everything from one place becomes enormous. A complex system therefore needs organization at multiple levels, with each level capable of handling some of the problems that arise within it. Autonomy is nested.

Modularity allows a large system to contain smaller systems that can manage their own complexity. Without that, every level would have to constantly communicate with every other level, and the amount of coordination would explode. The system would spend more and more of its energy trying to coordinate itself rather than actually doing anything.

Water, modularly

The water cycle has something similar going on. There is a global water cycle involving the oceans, atmosphere, land, rivers, groundwater, ice, soil, and living organisms, but there isn’t just one water cycle operating at one scale. There are countless smaller water cycles nested inside it. A forest has its own movement of water between soil, vegetation, groundwater, and atmosphere. A watershed has its own dynamics. A wetland has its own dynamics. A groundwater basin has its own dynamics. These smaller cycles are not separate from the global water cycle. They are modules within it.

What makes them modules is not simply that they occupy different places. It is that they have some degree of autonomy. A forest can regulate some of its own water conditions. Soil can retain and release water without the entire watershed having to coordinate every movement. Groundwater can store water and release it according to its own slower dynamics. Vegetation can capture water, move it through roots, and return it to the atmosphere. Each system has its own processes and feedback loops, even though it remains connected to the systems around it.

This is important because a complex water system would be extremely difficult to coordinate if every movement of water had to be determined at the global level. The global water cycle doesn’t tell every plant when to open its stomata or every soil particle when to absorb water. It doesn’t have to. Local systems handle local water problems themselves, while the larger system provides the conditions within which those smaller systems operate and the smaller systems continuously modify the larger one.

The small water cycle and groundwater cycle are an interesting example of how modules can become partnered. The small water cycle moves water between vegetation, soil, and atmosphere. The groundwater system stores water below the surface and moves it through a much slower cycle. They have different structures and different timescales, but they can support one another. Groundwater can sustain vegetation during dry periods, while vegetation and soil processes help water infiltrate and recharge groundwater during wet periods. The groundwater cycle can feed water into the small water cycle, and vice versa.

Their autonomy makes the partnership possible. Groundwater doesn’t need to immediately respond to every change in atmospheric conditions. It can operate on a slower timescale. The small water cycle can respond much more quickly to local conditions. Because the two systems have different dynamics, they can divide the problem between them. One can handle some of the variation while the other handles another part.

This is why a large storm does not necessarily have to become a large flood, and why a drought does not necessarily have to immediately become an ecological collapse. A healthy landscape contains modules that operate at different scales and timescales. Vegetation, soil, wetlands, streams, and groundwater each respond differently to the same event. The water is redistributed among these modules, and the system as a whole becomes less dependent on any single process.

The important point is that redistribution is a consequence of modularity. Water can be stored in groundwater because groundwater is a semi-autonomous subsystem. Water can remain in soil because soil has its own storage dynamics. A forest can retain and recycle moisture because vegetation has its own internal organization. These modules don’t eliminate extremes in the global water cycle, but they prevent every fluctuation at the global or regional level from being transmitted directly through the entire system.

This also gives the water cycle memory. A storm may happen in a few hours, but the groundwater module can retain some of its effects for years. A drought may last for several seasons, but water stored previously in the ground can continue to support vegetation. Different modules therefore take events occurring at one timescale and transform them into processes occurring at another. The system is organizing not just space, but time.

Life is deeply involved in creating these modules. Plants change the soil. Roots create pathways for water. Microbes change soil chemistry and structure. Vegetation changes evaporation and transpiration. Animals dig, move nutrients, create ponds, alter vegetation, and change where water can move. Over long periods of time, these biological processes can create increasingly distinct local water systems with their own feedback loops.

This suggests that modularity itself can evolve. A plant that can access groundwater has a different relationship with drought from a plant that depends entirely on rainfall. A forest that can maintain its own local moisture has a different relationship with the surrounding climate from bare ground. An ecosystem with deep soils and groundwater connections has a different degree of autonomy from one in which rainfall immediately becomes runoff. The more an organism participates in creating and maintaining a local water module, the more its evolutionary trajectory becomes tied to that module.

This creates the feedback between modularity and evolution. Organisms modify water flows. Those modified flows create local environments. Those environments change selection pressures. Organisms then adapt to those conditions and modify them further. Over generations, the biological and hydrological systems become increasingly coupled.

I believe theres a gap in current evolutionary theory in that it misses the co-evolution of life and the regional small water cycle-groundwater cycle-river cycle system. Life is affecting that local water cycle. The local water cycle affects life. Evolution selects certain life forms that then affects that co-evolution of the life-local water cycle. Evolution is not happening against a fixed water cycle. It is happening within water systems that organisms are continually helping to construct. A plant changes its environment, that environment changes the conditions for the next generation, and the next generation inherits not only genes but a modified ecological context.

Over millions of years, life and water may have coevolved toward greater modularity, with more organization and autonomy appearing at different spatial and temporal scales. The global water cycle contains regional cycles. Regional cycles contain watersheds. Watersheds contain ecosystems. Ecosystems contain soil, groundwater, plants, and microbial systems. Each has its own dynamics, while remaining connected to the others.

The same pattern exists in time. A storm operates over hours. Soil moisture operates over weeks and months. Groundwater can operate over years or centuries. Forests change over decades. Evolution operates over generations. Geological systems operate over millions of years. Each timescale can absorb, transform, and pass information from the timescales around it, so that an event occurring quickly can have effects that persist for much longer.

The system becomes a kind of nested temporal machine. A fast event does not necessarily have to remain a fast event. A storm can become groundwater. Groundwater can become plant growth. Plant growth can become soil. Soil can affect future water infiltration. Those changes can persist into future generations. In this way, the different modules don’t just move water around. They transform the effects of events as those effects pass between scales.

The resilience of the planetary life and water system emerges from the fact that water has been organized into many partially autonomous subsystems, each with its own storage, flows, feedbacks, and timescales. And life may have played a larger role in facilitating that organization.

Relating societally to water, modularly

People change rivers, groundwater, irrigation, floodplains, vegetation, and watersheds, while those changing water systems in turn change where people live, what they grow, how they organize, and what kinds of institutions they develop. These are hydrosocial systems.

Modularity can be a lens to understand these systems. Instead of looking only at the feedback between one large social system and one large hydrological system, we can ask how those feedbacks operate at different scales. A household interacts with its immediate water environment. A neighborhood interacts with a local drainage system. A farming community interacts with soil moisture and groundwater. A city interacts with a watershed, while a region interacts with river basins that cross many communities. Each social system is connected to a corresponding hydrological system, and each can have some degree of autonomy while still being nested inside larger systems.

A complex water system wants to be more modular. Our approach to water management should reflect it. We often try to manage water at the largest practical scale, through national or state policy, centralized agencies, large infrastructure, and enormous engineering projects. Some of this is necessary. Rivers cross political boundaries, groundwater basins span communities, and major infrastructure requires resources and coordination that a single community cannot provide. But it does not follow that the larger level should be responsible for everything.

A community knows things that a state government cannot easily know. It knows which parts of the neighborhood flood first, which drainage channels have become blocked, which gardens are drying out, where water tends to pool, which soils hold moisture, and which people are willing to organize around a particular problem. A gardener knows something different from a shopkeeper. A school knows something different from a farmer. Someone maintaining a local stream may see subtle changes that never appear in a government report.

This is where modularity becomes useful as an organizing principle. The community can become a module within the larger watershed, with enough autonomy to respond to its own conditions while remaining connected to neighboring communities and larger institutions. It doesn’t have to wait for a distant state agency to notice that a particular drainage channel is failing. It can respond locally, experiment, learn, and then communicate what it has learned to the larger system.

This connects closely to the work of Elinor Ostrom, the political economist who studied how communities around the world manage shared resources such as forests, fisheries, grazing land, and water. She challenged the idea that common resources must either be privatized or controlled by a centralized government. Communities can create their own rules and institutions for managing a commons, often in ways that are closely adapted to local conditions. Her idea of polycentricity extends this further: complex problems can be governed through multiple centers of organization operating at different scales rather than through one central authority.

A household can manage some things. A neighborhood can manage others. A watershed organization can deal with problems that cross neighborhoods. A regional or national government can handle problems that require still larger coordination. These levels are connected, but they can retain their own autonomy. The larger system doesn’t have to know everything because the smaller systems are capable of sensing and responding for themselves.

A community knows things that a state government cannot easily know. It knows which parts of the neighborhood flood first, which drainage channels have become blocked, which gardens are drying out, where water tends to pool, which soils hold moisture, and which people are willing to organize around a particular problem. A gardener knows something different from a shopkeeper. A school knows something different from a farmer. Someone maintaining a local stream may see subtle changes that never appear in a government report.

Rob Hopkins, one of the founders of the Transition movement, brings this idea of modularity into the question of community resilience. He argues that resilience is not simply about recovering from shocks, but about how a system is organized before the shock occurs. As he puts it, “Resilience runs much deeper: it is about building modularity”, describing the need to build “surge breakers” into the basic systems that support us. A community becomes more resilient when it has local capacities that can respond to problems without everything having to be coordinated from the center.

Facilitation can be helpful here. Facilitation helps to bring different parts of a community connected together, the various sectors to hear each other, understand each others language and work together.

One of the things we can build from the ground-up is a network of water nodes around the world, with ability to work autonomously on its own issues, while also coordinating and learning from each other. Michel Bauwen’s calls this organization structure cosmo-local.

Our society has made water systems more centralized and less modular. Huge dams, channels, levees, and drainage systems can take water that once moved through many connected pathways and force it into a smaller number of controlled pathways. A river that once overflowed onto a floodplain could recharge groundwater, support wetlands, refill soils, and provide water for plants whose roots then fed back into the small water cycle. When those connections are cut off, the different modules of the water system become less connected and less able to support one another. The result can be a system that is more efficient at moving water in one particular direction, but less capable of adapting to extremes.

Part of the task of water management now is to make these systems more modular again, so both the larger whole and smaller parts function better. We can restore groundwater cycles, reconnect rivers with floodplains, rebuild wetlands and soils, and restore the small water cycle through vegetation and landscape management. Instead of seeing these as separate environmental projects, we can see them as ways of rebuilding the modular structure of the water cycle, giving water more pathways to store, move, and recycle itself. Humans have already reshaped the water system enormously. We can use that same capacity to help restore the connections between its smaller modules.

This also means thinking about the economics surrounding water management. We have overdone globalization in the same way that we have overdone centralized water management. Global markets in our current extreme form disconnect economic activity from the ecological systems that sustain it. A community can make decisions about land and water according to prices coming from somewhere else, while the actual consequences are experienced locally.

If we are reorganizing around water, we therefore need community economics as well as community water management. A watershed is not only a hydrological system. It is an economic system. People farm there, build there, run businesses there, maintain forests there, use water there, and depend on the condition of the land around them. The economic organization should reflect some of that local interdependence.

We want more economic activity rooted in the communities and ecosystems where the consequences occur. A community might have businesses, farms, schools, cooperatives, land trusts, and community gardens that have a direct interest in maintaining the health of the local commons. The economy becomes connected to the ecological system rather than existing as something separate from it.

This is where the community commons becomes important. Land, water, forests, grazing areas, and community gardens can sometimes be managed as commons rather than being treated simply as commodities or resources controlled entirely by distant institutions. Community land management gives people an ongoing relationship with the places they depend on. They have a reason to maintain the soil, preserve groundwater, manage vegetation, and think about what the landscape will look like decades from now.

The commons also introduces another timescale into the economic system. A business concerned only with the next quarter has little reason to care about an aquifer fifty years from now. A community that expects its children and grandchildren to remain on the land has a different calculation. It has a reason to preserve the resource because it expects to live with the consequences.

A community economy can become a module within the larger economy. It has some autonomy, but it is not isolated. It trades with other communities and participates in regional, national, and global markets, while retaining enough local organization to respond to local conditions and maintain some of the commons on which its economy depends.

There is also an advantage to having many communities experimenting at once. One might develop a better way of managing groundwater, another a successful community land trust, another a system for coordinating farmers around watershed restoration. They can learn from one another without every community having to follow exactly the same model. The larger system becomes more adaptive because it contains many smaller places where experimentation can happen. This is the cosmo-local network of water nodes learning from each other, and adapting together at multiple scales, evolving hydrosocially into the future.

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For related article : Living architecture - slow it, sink it, spread it, sap it, sweat it, sky it

Sometimes people are disbelieving that trees could transpire enough to create clouds. Well, this is the visual evidence. We can see transpiration in action. It’s the forest’s transpiration and the soil moisture evaporating, all combining to generate so much moisture that it condenses right above the trees.

[photo: David Clode}

Here is a picture of this transpiration in action happening in Mt Whitfield in Queensland, Australia.

[from Matthew Abeler’s website].

Here’s a picture of transpiration in action in the Amazon. The Amazon transpires a mighty 20 billion tons daily.

Its not always the case though that we can tell where clouds come from. How much of it is caused by ocean moisture, how much from the land, from the small water cycle?

In this photo above, how do we figure out how much of that cloud comes from ocean moisture blowing inland, and how much from evapotranspiration from vegetation and soil?

Well, scientists have been coming up with a lot of clever tricks. They use statistical techniques to correlate rain with ocean temperatures and with how land-based precipitation recycling works. The amount that doesn’t correlate with the ocean is suggestive of another process at work. To do this, though, scientists first have to understand how oceans create rain.

Oceans create rain on land primarily through evaporation and atmospheric transport. When the sun heats up vast expanses of ocean water, massive amounts of moisture evaporate into the air. Prevailing winds and global weather patterns then pick up this water vapor and carry it across coastlines and continents. As these moisture-laden air masses move inland, they can be forced upward by rising topography like mountains (orographic lift), or they can collide with cooler air masses, causing the water vapor to cool, condense into clouds, and eventually fall as rain or snow far from where it originally evaporated.

It turned out that ocean basins were connected all across the world, with different patterns that would propagate via wind currents, etc. Amazingly, the sea surface temp in a particular ocean would often correlate with rainfall on other continents far away, whether it be Africa, the Americas, or Europe or Australasia. For instance, ENSO (composed of El Niño and La Niña) showed how changes in sea surface temperature in the Indian, Atlantic, or Pacific Ocean would ripple out via wind shifts across to all the different continents. To picture how it works: normally, steady trade winds blow from east to west, pushing warm water toward Asia and Australia while pulling up cold water off the coast of South America. During an El Niño, those trade winds weaken, and the pool of warm water sloshes back eastward across the Pacific, deepening the warm layer of water (the thermocline) in the east. Because that warm layer is now so deep, the ocean stops bringing up cold water, making the eastern Pacific unusually warm. The winds shift ocean temperatures over a period of time, the ocean warm waters move to one side, and these changes move across the globe, which then shift ocean temperatures in other ocean basins and ultimately shift rain on the land.

To make sense of the complexity of climate, scientists started identifying other quasiperiodic climate modes, such as the Indian Ocean Dipole, the Tropical North Atlantic, and the Madden-Julian Oscillation. By checking whether their quasi-periods matched, scientists could determine which rain was caused by which mode. They ran correlations between sea surface temperatures and rainfall; if the correlations matched and fit dynamical system models, they could track the cause.

So if we were to say try to understand what is happening to rain in the Sahel, we can look at how it correlates with sea surface temperatures in different ocean basin. Winds are generated when land warms up in the Sahel and Sahara, creating a low-pressure heat engine that draws ocean winds blowing in. The temperature difference between the North and South Atlantic oceans helps determine how that wind blows, and how strong and fast. These affect what are called mesoscale circulation systems. There are then these jets called African Low Level Jets and Tropical Easterly Jet, which are fast moving bands of air in the Sahel that intersect with the mesoscale system circulations to create rain. There are also winds blowing down from the Mediterranean Sea. When the Mediterranean heats up, more evaporation rises, and some of that water vapor gets blown down to the Sahara and Sahel.

Scientists look at the way these sea surface temperatures change then correlate it with patterns of rain in the Sahel. And the patterns of rain they create are different than those from the land recycling that water back up to the air, the small water cycle. So statistically they can look at these things. There’s been a wide variety of these statistical techniques to unravel these correlations.

[rain storm in Sahel]

Yan Yu was a postdoc at Madison, Wisconsin, when she was trying to figure out how to tell whether changes in Sahel rainfall were coming from the ocean or from the land. What she used was a particular spatial temporal correlation technique (something called GEFA, or Generalized Equilibrium Feedback Assessment). Basically, the ocean and the land affect rainfall in different ways, so they leave different patterns in the climate system.

Land–atmosphere feedbacks have a different pattern. Vegetation and soil moisture can increase evapotranspiration, putting more water vapor into the atmosphere. That moisture can then be transported and contribute to rainfall. Because the land and ocean vary in different places and on different timescales, GEFA can statistically separate their contributions.

What she found was that during the peak monsoon season, oceanic forcing was more important for Sahel rainfall. But toward the end of the monsoon, the influence of the land became much more important. Terrestrial forcing explained about 8% of annual-mean precipitation variance, but this increased to roughly 18% during the late-to-post-monsoon season, when land-surface effects became comparable to or larger than oceanic effects.

And there is an interesting complication. The evapotranspiration (ET) from vegetation does two things at once. First, it puts more water vapor into the atmosphere, which can promote convection and rainfall which is the moisture-recycling pathway. But evapotranspiration also cools the surface. That cooling makes the atmosphere more stable, which can suppress the upward motion needed for convection and rainfall.

So there are actually two competing effects: ET to more atmospheric moisture to more rainfall versus ET to surface cooling to greater atmospheric stability to less convection to less rainfall.

At lower levels, turbulence in the air can mix and heat air near the surface. If a parcel of this warmed air rises high enough, it can continue rising because it is warmer and less dense than the surrounding air. Evaporative cooling reduces this warming, making it less likely that warmed air will continue rising. (Technically speaking, evaporative cooling can keep the boundary layer below the level of free convection, making it harder for air parcels to reach the height where they can rise freely and potentially form rain.)

They could see evidence for both effects in the observations. But Yu found that the moisture-recycling effect was stronger than the suppressive effect, so the net effect of increased vegetation was an increase in rainfall.

Rain does not arrive the same way everywhere on Earth. Different regions have developed different ways of pulling, carrying, and recycling water through the atmosphere.

In South Asia, for example, the Tibetan Plateau acts like a giant seasonal heat engine. As the land heats up in summer, it helps draw moist air northward from the Indian Ocean, contributing to the powerful Indian monsoon.

In the southwestern United States, a smaller-scale summer monsoon brings moisture northward into Arizona and surrounding regions. South America has a very different system. The Amazon rainforest is part of a vast network of “flying rivers,” where trees continually pump water from the ground into the atmosphere through transpiration. Winds then carry some of that moisture across the continent, allowing rain to fall, be recycled by forests, and travel onward again. The forest is not simply receiving rain—it is helping move the rain.

Europe has yet another arrangement. Its rainfall is shaped by the meeting of oceanic and continental influences: moisture-laden westerly winds arrive from the Atlantic, while seasonal heating of the European landmass and the Mediterranean helps shape where and when that moisture falls.

North America has another rhythm separate from the Arizona monsoons. In winter, storms carry enormous amounts of Pacific moisture into California and Oregon and then across the continent. Rather than being driven primarily by a sudden seasonal “suck” of air, as in a classic monsoon, this system involves a succession of atmospheric rivers, storms, and moisture transfers across the landscape.

It’s actually a common puzzle in different fields from economics, sociology, hydrology, planetary science, to ecology, to figure out what causes what. One field will develop a statistical technique, and then it will get appropriated by another field to use for its own studies. For instance, Principal Component Analysis (PCA) was originally developed in psychology to simplify complex webs of mental test scores and uncover underlying traits like general intelligence, before getting appropriated into climate science as EOF (Empirical Orthogonal Functions). In climate science, EOFs act like an analytical lens: scientists use them to break down massive grids of global weather data into dominant spatial maps and temporal time series. By running EOF analyses on both sea surface temperatures and regional rainfall, researchers can match the patterns and see if an ocean anomaly marches to the same drumbeat as land rainfall thousands of miles away. Economics has also been a leader in developing statistical techniques that then get borrowed by other fields, such as Granger causality - which was originally created by Clive Granger to figure out if one economic time series (like money supply) could reliably forecast another (like inflation or GDP). Climate scientists and hydrologists now use Granger causality to test whether land-surface conditions like soil moisture actively drive and predict subsequent rainfall. Statistics can sometimes be a bit of a shaky subject and easily misleading, so researchers have to be careful. Granger causality is sometimes misleading in economics, and there are ways it can miss things in climate science; however, it can still be a useful tool to help give us a sense of what is going on.

So by comparing the sea surface temp of different basins and understanding the ways these climate modes propagate around the world (teleconnections) and then studying them statistically, you can decompose precipitation into a land-atmosphere component versus an ocean-to-rain component. Then researchers run computer models to see if they get the same result. Sometimes the numbers are close to each other. But sometimes the numbers don’t always agree. In those cases there is more digging to do to understand what is going on. Even though the exact ratio of sea-rain coupling to land-rain coupling remains a puzzle waiting to be fully solved, what we do know is that global rainfall is a deeply interconnected dance: distant ocean temperatures steer atmospheric rivers and winds across entire planets, while local vegetation and soil moisture actively recycle water back into the sky to help fuel subsequent rainfall.

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Yu, Yan, Michael Notaro, Fuyao Wang, Jiafu Mao, Xiaoying Shi, and Yaxing Wei. "Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism." Nature Communications 8, no. 1 (2017): 1873.

Instead, “slow it, sink it, spread it” is about working with the landscape to keep water moving through living systems. Vegetation, richer soils, earthworks, swales, rain infiltration ponds, beaver dam analogs, leaky weirs, gabions, zai pits, half-moon crescents, johads, and other techniques all help rainfall infiltrate the ground, recharge aquifers, and restore natural water cycles.

[Photo of Brock Dolman leading tour at OAEC by David McConville, Spherical CC BY-NC-SA 4.0]

We visited Brock Dolman at the Occidental Arts and Ecology Center and its Water Institute. Someone in our group called it the Mecca for permaculturists, a place people come from around the world to learn and be inspired. Our visit was part of our recent Rehydrate the West multi-town tour of California, where we were listening to communities and facilitating conversations about what is happening with water across the state (more to come on this). At the center, we saw beautiful examples of guiding water flow across the landscape and designing with ecological processes rather than against them.

As we went to dinner, I shared with Brock my extension of his slogan: “Slow it, sink it, spread it, lift it, hop it.”

In this expanded version, “lift it” refers to the way vegetation draws water upward through plants, while “hop it” refers to the small water cycle - the movement of moisture through evapotranspiration and atmospheric processes that allows water to travel across landscapes and even continents. It also comes with an accompanying lemma: “lift it < sink it.” If we lift water through vegetation without first restoring the soil’s ability to hold water, we risk drying out the land.

Brock liked the idea. He is a poet with words, and even in everyday conversation, he often speaks in alliteration, rhythm, and memorable phrases. Later, he built on the idea, and suggested an alliterative variation : “Slow it, sink it, spread it, suck it, skywater it.”

Nik Bertulis, an eloquent speaker on ecology and water (interviewed here previously), joined the brainstorming. Nik speaks eloquently about ecology and water, and together we all came up with another variation we liked:

“Slow it, sink it, spread it, sap it, sweat it, sky it.”

“Sap it” refers to vegetation drawing water upward through living systems. “Sweat it” points to transpiration and transpirational cooling. “Sky it” describes evapotranspiration moving water into the atmosphere, where it can eventually return as rain.

We might also include the way water helps generate more vegetation:

“Slow it, sink it, spread it, sprout it, sap it, sweat it, sky it.”

The vegetation itself becomes part of the water cycle as it is absorbing, redistributing, cooling, and returning water to the atmosphere.

One of the reasons the “Slow it, sink it, spread it” mantra was so useful was that it suggested water should not simply leave the system through runoff and rivers, but that we can also direct it into the groundwater cycle (see figure above)

The addition of “sap it, sweat it, sky it” expands the picture by including the dew cycle and the small water cycle (precipitation recycling). The extended slogan helps connect these different water pathways.

As I pondered it further, I realized we could also connect it to the large water cycle, the movement of ocean moisture inland that helps create rainfall.

Large forests like the Amazon, the Congo rainforest, and the Indonesian rainforests can influence the large-scale water cycle. The Biotic Pump hypothesis proposed by Gorshkov and Makarieva argues that the vacuum created by water condensation acts as a suction force, drawing in ocean air. A related, more conventional mechanism for large-scale atmospheric moisture transport has been proposed by UCLA meteorologist Rong Fu, who suggests that latent heat release from condensation in he Amazon and Congo rainforests causes this sucking of ocean air towards itself (see previous article on this).

So we can add “suction it,” giving us:

“Slow it, sink it, spread it, sprout it, sap it, sweat it, sky it, suction it.”

These actions help activate the living architecture of the Earth, to activate the connection of the four water cycles.

Manlio De Domenico writes a newsletter called Complexity Thoughts. In his article, he discusses the complexity science behind living architectures and the importance of loops:

“The simplest use of a loop is to preserve reachability, since if one route is blocked then another route may still connect two parts of the system… In metabolism, this can mean that flux can be ‘rerouted’ after a specific reaction is disrupted for some reason. In signaling, it can mean that partially overlapping pathways transmit similar information. In ecological networks, matter or energy may continue to move through alternative species interactions when one link weakens.”

What our slogan describes is the process that enables multiple pathways for water to move through a system. If we experience several years of drought, vegetation has alternative pathways to access water. The system can shift water from the wet season into the dry season.

A familiar challenge to hydrologists are: flooding during the wet season and water scarcity during the dry season. You can tackle this issue with nature based solutions. Slowing the water with beaver dam analogs, richer soils, and other landscape interventions allows the system to function more like a living system, rerouting and storing water. The system becomes more adaptable. It shifts water from the wet season to the dry season via the lower groundwater cycle loop, instead of it all escaping sooner via runoff and river loop. It delays the system to fit the ecosystems needs.

Now, by adding the upper loop, the small water cycle, we are connecting another pathway into this living system. It enables the landscape to adjust by creating additional ways to bring moisture back into the ecosystem. The land can generate more rainfall through precipitation recycling, creating a different way of transporting water across landscapes.

If ecosystems depended only on ocean moisture, rainfall would exponentially decline as distance from the ocean increased because moisture would continuously drop out. Instead, healthy landscapes act more like relay stations, continually recycling and redistributing water.

De Domenico also writes:

“A feedback loop exists when a variable affects its own future through the system.”

He describes loops as processes of production:

“A process is closed when its outputs help regenerate the components or conditions that make the process possible… Kauffman’s autocatalytic-set idea made catalytic closure central: a set of molecules can collectively catalyze reactions that generate members of the same set.”

What we are doing is further linking together and restoring multiple water cycles. This allows the system to better respond to its own future by creating multiple pathways for hydration.

Water can arrive through the atmosphere, be stored in the ground, and be shifted through time. The system can better handle drought, store excess water from floods, and maintain hydration that reduces vulnerability to large fires. With this increased hydration, vegetation grows more abundantly, soils become richer, and the landscape becomes better at running its own water cycle.

As soil stores more water, trees can help move water deeper into the ground during wet periods and draw it upward during dry periods.

The system also develops its own climate regulation mechanisms. It can adjust temperature by bringing water upward through evapotranspiration, the sweating and perspiring function of the living landscape. The dew cycle acts as a humidity system. I have noticed in old-growth forests that they can remain cool and humid even while surrounding environments are dry and hot. Soil also helps regulate temperature, holding heat during colder seasons, while water supports the microbiome and organisms that create richer soils.

An autocatalytic set is one that catalyzes itself into being. Vegetation, soil, fungi, bacteria, and water together create a system that can autocatalyze itself into a more complex and living architecture.

I have always been fascinated by the idea of autocatalysis. I think it may be one of the bridge concepts that integrates hydrology, climate science, ecology, permaculture, regenerative agriculture, and ecological restoration. It suggests how we can nudge the Earth into a phase space where it can more easily reshape its own water cycles and ecosystems, allowing the exponential potential of regeneration to emerge.

“Slow it, sink it, spread it, sprout it, sap it, sweat it, sky it, suction it” is a set of guiding principles for transforming the Earth into a more living, autocatalytic architecture. It helps create a circulatory system with more interconnected water loops, enabling the planetary system to better self-organize, adapt, and regenerate.

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For a follow up article “Autonomy at all scales : life, water, and society”

Vegetation and rain

The mystery of the biotic pump experiment that rotated the wrong way

Plants drink water from the air: hydrologist Sieger Burger interview

The solution to stop the expansion of the Sahara no one is talking about

The forest-water connection: ecologist Douglas Sheil

An intriguing behavior of global rain

The planetary boundaries of green water : Lan Wang-Erlandsson

Water and Fire

Taming the hot dry winds that cause wildfires; sponging up freak storms

Lessening LA wildfires : The water solution - A dialog with Didi Pershouse

Halting our drought-fire-flood path to desertification:Zach Weiss

Groundwater lessens wildfires

Groundwater

The unsung linchpin : groundwater helps stabilize the climate

Green water, blue water, silvergreen water, silverblue water

The dance of groundwater and vegetation

The big groundwater crisis - food, water, pollution, and social unrest : John Cherry interview Part I

Groundwater & climate crisis solutions: regenerative ag, rainwater harvesting and interdisciplinary collaborations - John Cherry Part II

The 2014-2016 water drop

The plan to replenish our groundwater : Helen Dahlke

A dramatic rise in groundwater in the Sahel

Bacteria and fungi seed rain

Bacteria make rain : Bioprecipitation part I

Snow, hail, bacteria and nucleating ice: bioprecipitation part II

Hormonal metaphors for rain and climate : Bioprecipitation III

Is the earth microbiome regulating our climate?

How bacteria, fungi and plants evolved paleo-rain

Eco-restoration and Practitioners

Absorbing rains to bring landscapes back to life : Neal Spackman

Halting our drought-fire-flood path to desertification:Zach Weiss

Regreening the Sinai : Ties van der Hoeven

The joy of restoring water cycles : Nick Steiner

Natural Sequence Farming : Stuart Andrews

How much land do we have to restore to bring back the rain?

Rivers of land and sky: project restoration

Activating a global network of water restorers and advocates : Zach Weiss

Top 100 ways to restore the water cycle

Ways to use the permaculture network to accelerate the water movement

‘Our Blue World’ documentary : Paul O’Callaghan

Slow water

Beavers, biology and slow water : Brock Dolman

Slowing our waters : Erica Gies

Putting rocks in rivers to lessen drought, fire & flood: Laura Norman, physical scientist

Green and grey infrastructure for water : Angelina Cook

also a lot of the articles/interviews in the Ecorestoration and Practitioners section using slow water techniques

Beavers and other animals

Beaverland : Leila Philips

Rewilding, beavers, and water restoration : Derek Gow

Beavers brought rain to North America

Beavers, biology and slow water : Brock Dolman

Animals are helping our water cycle : Judith Schwarz

Agriculture

Natural Sequence Farming : Stuart Andrew

Natural Sequence Farming, climate change and water : David Maher

Regenerating a farm and a semi-arid region : Sylvia Quarta

Soil

The laws of water part I : How water moves through soil

Bread and museums : Didi Pershouse

Finance, Insurance, Business

Investing in regen ag : Koen van Seijin

The regenerative economy

Supply chains & insurance: the secret levers to restore water - Stephanie Betts

Of floods, droughts, land cover, aquifers and insurance

How eco-tourism can help the regenerative water movement

Small water cycle/ precipitation recycling

Map of the small water cycle

Land use and climate change

What would happen to the rain if the whole world was a desert?

Restoring Iberian Rain

The quest to figure out the origin of rain part I

The quest to figure out the origin of rain part II

Biotic Pump : Anastasia Makarieva

What causes the rainy season to start in the Amazon and Congo?

What implementing agroforest on farms would do to the rain

The hidden langauge of water and matter : The water trackers part I

Measuring the small water cycle part: The water trackers part II

Making the map of the small water cycle : van der Ent

Precipitationsheds and the socio-economics of rain: Patrick Keys

How forests create the rain : Francina Dominguez

The small water cycle papers

The solution to stop the expansion of the Sahara no one is talking about

Seminal papers on water

Whole earth thinking, systems thinking

Web of water

Biodiversity regulates the climate: Adventures in Daisyland

Unifying ecology and climate with fourth law of thermodynamics: Part II Biodiversity regulates climate

Energy flows and matter cycles : Part III Biodiversity regulates climate

A pattern language for eco and water restoration

The hedgehog and the fox : on unifying ecology, climate, and water

New terms for the small water cycle

Water Ecology Principles

The planetary boundaries of green water : Lan Wang-Erlandsson

The coupled planet: how forests, groundwater, rain, & climate shape each other. A complex systems approach

The algebra of the earth that reveals its multifunctional genius

Charles Eisenstein : water and the living earth

Integral science : how evolving consciousness changes our view of water, life and climate

Water quality

Pee, poo, and wastewater as nutrient water : Nik Bertulis

Bringing our lakes and oceans back to life: how to deal with algae blooms and polluted waters

The big groundwater crisis - food, water, pollution, and social unrest : John Cherry interview Part I

Bioregional

Communities can protect themselves against floods and droughts : Minni Jain

How to activate your community around water

India’s regenerative water movement : Andrew Millison

Regenerating a farm and a semi-arid region : Sylvia Quarta

Research problems

A more exciting set of unsolved problems of hydrology

A research programme for water cycle restoration

The 23 unsolved problems of hydrology

Art

The art of water : Charlotte Qin

The water tale : a rap song

Portraits of water

Philosphical

Water and the living earth : Charles Eisenstein

The hedgehog and the fox : on unifying ecology, climate, and water

Integral Science: how evolving consciousness changes our view of water, life, and climate

On the nature of water and its stewardship

Lakes

Bringing our lakes and oceans back to life: how to deal with algae blooms and polluted waters

Yearly review

2022 in review : Climate water project

2023 in watery review

Watery 2024 review & 2025 launchpad

A 2025 review, aqua-ly

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This above data is from Chad, at 13.5N 17E. I looked around at other places along the same latitude in the Sahel, and they were all increasing faster. So I worked on some Python code, pulled all the satellite data, and looked across the 13.5N transect from Senegal to Mali to Burkina Faso to Niger to Chad to Sudan. Lo and behold, they were all increasing faster. It was increasing fastest towards the middle of the continent, in Chad.

[The x-axis here is the longtitude, so imagine you are going across the Sahel. The y-axis is the terrestrial water storage increase acceleration]

The increase in terrestrial water storage means the groundwater is increasing too, which is a big deal since it has a big effect on society’s water supply. All around the world we are experiencing a lot of over extraction of groundwater. So it’s particularly interesting when there are areas with huge increases in groundwater.

So I started looking around to see why this terrestrial water storage was shifting.

One might think that terrestrial water storage is increasing because the rain is increasing. But Susanna Werth, a geodesist who tracks the planet's water mass budget using remote sensing data, studied the Niger basin from 2003 to 2013 and found something puzzling: terrestrial water storage was rising significantly across the Niger River basin and most of its subbasins, yet there was no sufficient increase in rainfall quantity over the same period to explain it [Werth 2017]. Her explanation pointed instead to the behavior of water after it falls: a great deal of rain flows into low-lying areas and from there percolates slowly down to recharge aquifers, a mechanism a number of hydrologists have highlighted for the region.

My own first idea for why there was this massive jump in terrestrial water storage was that it was because of all the restoration work done under the Great Green Wall across the Sahel, and how areas like Burkina Faso, Niger and Chad have undertaken massive rain infiltration projects that has led to the terrestrial water storage increase. And I still think this is the primary reason, coupled with other factors.

In Niger and Chad villagers are digging half-moon crescents and growing vegetation at large scale, which results in more infiltration, less runoff, more water finding its way underground.

[Yacouba Sawadogo]

A farmer named Yacouba Sawadogo brought back this ancient indigenous technique called zai pits in Burkina Faso. Villagers mocked him at first, but with persistence over decades he began to convince fellow villagers of its power. He was eventually called the Man Who Stopped the Desert, and worked with NGOs and government programs to train and mobilize farmers to dig by the millions.

[Zai pits]

The massive water recycling and eco-restoration projects in the Sahel are really quite astonishing in scale. Andrew Millison’s inspiring videos captures the scale and power of these projects.

Having noted this extraordinary rise of terrestrial water storage in the Sahel I was curious what groundwater state around the world was. I looked around for a map of groundwater depths and found the work of Ying Fan, a hydrologist at Rutgers. On her website she writes ‘I am a hydrologist not interested in water per se, but in what water does to shape our landscape through the ages. Water connects all. Little happens without water." She took information from well data around the world and put it into groundwater models to measure how water moves underground, producing a map of groundwater depths across the globe. In that map the Sahel is colored green, indicating that much of the water table there sits at about 5 to 10 meters depth.

[Simulated groundwater tables from Fan’s work]

So zai pits, half moon crescents, and low lying recharge areas are increasing the terrestrial water storage. What about the role of rain? It has been increasing and so is also a factor. Why has Sahel rain been increasing ?

One cause is that rainfall is rising because of changes in the ocean. Climate scientists figured out some time ago that changes in ocean temperature drive climate modes like ENSO, which then affect rain patterns around the world. It turns out that the temperature gradient between sea surface temperatures in the Tropical North Atlantic (TNA) and the Gulf of Guinea drives the ITCZ, the band of intense convection near the equator that migrates north and south with the seasons, and which in turn brings more or less rain to the Sahel depending on how far north it travels. Whether the ITCZ penetrates to 15 or 20 degrees north, deep into the Sahel, or stalls at 10 degrees, watering only the Guinean coast, is the difference between a good year and a failed harvest.

[NOAA data, you can see TNA rising recently]

It turns out that tropical North Atlantic sea surface temperatures have been rising over recent decades, driven by a combination of greenhouse warming and the cleaning up of industrial sulfur aerosols that had been seeding clouds and cooling that stretch of ocean for much of the twentieth century.

But ocean temperatures are not the only reason for the Sahel's wetter recent decades, there is also precipitation recycling. A group at the University of Wisconsin-Madison, led by climate scientist Michael Notaro and graduate student Yan Yu, working with collaborators at Oak Ridge National Laboratory, turned to three decades of satellite observations of vegetation cover across the Sahel, combined with on-the-ground rainfall records and measurements of temperature, humidity and wind [Yu 2017]. What they found was observational evidence for a positive vegetation-rainfall feedback. As plants draw moisture up from the ground through their roots, they release it back into the atmosphere through their leaves. That moisture drifts downwind and falls again as rain somewhere else in the Sahel, growing more plants, which transpire more moisture, which falls as more rain. Vegetation greenness during the late and post-monsoon periods favours enhanced evapotranspiration, precipitable water, convective activity and rainfall, with the precipitation recycling response of comparable magnitude to the evapotranspiration response itself. Notaro described the finding as demonstrating "an elusive feedback mechanism that's been hypothesized for the Sahel for decades."

The satellite remote sensing photos, leveraging gravitational anomalies, tell the powerful story of this dramatic rise in terrestrial water storage, the rise of this source of water for the millions of people in the area. It is important we figure out why its rising, scientifically. All the different factors are probably contributing to some degree: zai pits and half-moon crescents increasing infiltration, large scale eco-restoration, low-lying areas recharging aquifers, rising sea surface temperatures pulling the monsoon northward, declining industrial aerosol emissions warming the tropical North Atlantic, increased precipitation recycling through vegetation, and global warming. I believe the zai pits and half-moon crescents are a key aspect we should be focusing on scientifically, to document better hydrologically and to put into the climate and hydrological models. If we can track hydrologically what millions of small holes in the ground are doing to the water cycle of an entire region, we help develop our scientific understanding of how zai pits, earthworks, and permaculture processes like swales can restore water cycles, watersheds and degraded drylands all over the world.

What has also become even clearer to me through this investigation, is that to document the success of slow water movements around the world, and to convince the public and policy makers of their importance, we can leverage the power of remote sensing satellites.

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References

Fan, Ying, H. Li, and Gonzalo Miguez-Macho. "Global patterns of groundwater table depth." Science 339, no. 6122 (2013): 940-943.

Werth, Susanna, Dave White, and D. W. Bliss. "GRACE detected rise of groundwater in the Sahelian Niger River basin." Journal of Geophysical Research: Solid Earth 122, no. 12 (2017): 10-459.

Yu, Y., Notaro, M., Wang, F. et al. Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism. Nat Commun 8, 1873 (2017). https://doi.org/10.1038/s41467-017-02021-1

He found this very curious phenomena with water. When he put salts into the water and then diluted them out, at a high dilution these micron sized solid-like water clusters would form. These nano structures float inside the liquid water. If you then evaporate all the liquid water you are left with these small solid-like water structures. He gave these structures the name IE crystals and also stable water clusters. These structures have many important implications for many fields beyond water.

[nano structure water pictures, from this paper Lo, Shui-Yin. “Anomalous state of ice.” Modern Physics Letters B 10, no. 19 (1996): 909-919.]

He published these results in a mainstream physics journal with the title “Evidence for the existence of stable-water-clusters at room temperature and normal pressure”.

It goes on in paper ‘We report the finding of isolated stable-water-clusters of tens of nanometers to micron size from the evaporation of very dilute sodium chloride solution at room temperature and normal atmospheric pressure. The stable-water-clusters are found to be electrically charged by examination via an Electric Force Microscope (EFM). Raman scattering and infrared spectrum of residues from the evaporation show similar but not identical characteristics of liquid water.

One of the greatest advances on our understanding of water comes from the study of water-clusters. Most water-cluster studies have been focused on smaller water-clusters, below 100 water molecules. There exists a few studies on stable-water-clusters from tens of nanometers to micron size. These water-clusters are reported to be stable at room temperature at normal atmospheric pressures. These clusters are reported to be created from very dilute solutions made from a variety of different materials.

Here we report further evidence of these stable-water-clusters created from diluting minute amounts of NaCl in ultra-pure water.

In dilute solution of NaCl, sodium and chlorine ions coexist with water molecules, which have permanent electric dipole moment. The electric interactions of the dilute solution consist of those among ions and dipoles. When the density of ions is high, the dominant interactions are those among ions. As the concentration of NaCl decreases, there are less and less ions per unit volume. The interaction among ions becomes less and less. The interaction among dipoles becomes more and more important. There comes a point when the dipole–dipole interactions dominate. The transition point when this occurs is found experimentally to be at the concentration about 10⁻⁴ M(mol/liter). At concentration below this transition point, water molecules will attract to one another to form clusters that have permanent electric dipole moment, much like small magnets stick together to form a big magnet.”

More pictures of the water structures:

I wanted to record a podcast with my dad but was a bit hesistant. Someone suggested I could do it with a more limited distribution by putting it behind a paywall, so that’s what I did here with the podcast.

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The biologist Lynn Margulis, who made a key discovery on the origin of eukaryotes and the important role of symbiosis in evolution, spent much of her career arguing that bacteria were not merely early life, later superseded by more complex forms. They were, and remain, the foundational layer on which everything else runs, something closer to an operating system than a set of primitive ancestors. Bacteria are everywhere: in soils, in oceans, in the tissues of plants and animals, in the air above continents and the ice of glaciers. They worked their way into the cells of early eukaryotes and became the mitochondria that now power almost all complex life. They thread through the roots of plants, line the guts of animals, and cycle through the atmosphere in quantities we are only now beginning to measure. To understand how Earth’s atmosphere and climate evolved, Margulis argued, you had to understand how microbes co-evolved with them, not as passengers on a physical planet but as active participants shaping its chemistry, its gases, its climate, its conditions for life. The planet and its microbiome, in her view, were not separable things. They had been making each other for billions of years.

The atmosphere we breathe is, in large part, a microbial construction. The Great Oxygenation Event, the transformation of Earth’s atmosphere by photosynthetic bacteria some 2.4 billion years ago, made aerobic life possible and remains the most dramatic single intervention any life form has made on a planetary scale. But the microbial shaping of the atmosphere did not stop there. Nitrogen cycles through denitrifying bacteria in soils; the nitrogen-to-oxygen ratio in the air is the outcome of billions of years of microbial fixation and denitrification running in metabolic counterpoint. Methane, which should not persist in an oxygen-rich atmosphere since it reacts and disappears within a decade, is continuously replenished by methane-producing archaea in ocean sediments, wetlands, and animal guts. Bacteria cycle carbon in and out of the atmosphere, influencing Earth’s temperature across geological time. Each of these processes reflects the same underlying reality that Margulis identified: microbes do not merely inhabit the Earth’s chemical systems, they drive them.

Water is part of the atmosphere too, and here as well, bacteria and fungi, joined eventually by plants, have played a foundational and still underappreciated role.

[Proterozoic Eon]

During the Proterozoic Eon, roughly 2,500 to 541 million years ago, and into the early Ordovician Period, land was almost entirely lifeless to the naked eye. Microbial mats clung to certain wet surfaces, but the continents were bare: rock, wind, and light. When rain fell, it struck mostly unweathered mineral surfaces, pooled briefly, and sheeted off. Without roots or biological structure to interrupt the flow, water followed the nearest gradient to the sea. Very little soaked in.

Without plants, there was no transpiration, no mechanism for recycling water vapor back into the atmosphere from continental surfaces. As a moisture-laden air mass moves inland from the ocean, it loses water each time it rains. Without anything to return that water to the atmosphere, each successive rainfall event has less moisture to work with than the last. This results in exponential decay: heavy rain near the coasts, thinning rapidly as the air mass travels inland, until the continental interior receives almost nothing. The hydrological cycle over land was shallow and simple: ocean evaporation, inland delivery, surface runoff, return to sea.

Geologists reconstructed this ancient hydrology from the rock itself. Evaporites are sedimentary deposits formed when water evaporates and leaves dissolved salts behind, and they are among the most useful witnesses to ancient hydrology. When a lake or shallow sea evaporates completely, it leaves a chemical signature: sequences of gypsum, halite, and other minerals that precipitate in a specific order as salinity increases. Their presence and position tell geologists where standing water existed and how long it stayed. River geomorphology and floodplain sediments extend the picture further. Together they sketch a hydrological map of the ancient world.

Then life began to move onto land, and bacteria and fungi paved the way. After the microbial mats came fungi with their hyphae: threads so thin they could slip into microscopic cracks in rock. Lichens followed, ancient partnerships between fungi and photosynthetic algae or cyanobacteria that dissolve rock with acid and anchor to surfaces nothing else can colonize. These were road-builders, crumbling mineral surfaces into particles, creating the first rough substrate that something else might root in.

The first primitive plants, mosses and liverworts, appeared across damp margins and coastal flats. They had no deep roots, no leaves in the modern sense. They clung close to the ground, vulnerable to drying out. But they were connected, through mycorrhizal partnerships, to fungal networks that extended their reach into the mineral world, scavenging phosphorus, tracing faint films of water, dissolving rock with chemical persistence. In return, the plant fed the fungi carbon captured from sunlight. Energy flowed downward; water and nutrients flowed up. A small, fragile plant became, in effect, a distributed organism, one that threaded itself through the ground so completely that the boundary between plant and fungus lost meaning.

What this consortium was building, slowly, patch by patch, across millions of years, was the soil sponge. A soil with intact fungal networks and microbial communities is structured, porous, biologically active material with a fundamentally different relationship to water than bare rock. Rain that falls on it infiltrates rather than runs off. It is held in pore spaces, made available to roots over days and weeks. The building of the soil sponge enabled more precipitation recycling, allowing water to travel further inland.

. [vascular plants in Devonian period 419-359 million years ago]

The geomorphic signature of this transition is readable in the rock. Sedimentary sequences from the Silurian-Devonian Terrestrial Revolution, the period from roughly 428 to 359 million years ago when vascular plants first spread across coastal lowlands, show the braided, episodic channel patterns of bare-land drainage beginning to give way, first patchily then more broadly, to the finer-grained, more organized deposits that indicate stabilized banks and sustained flow. Evaporite deposition in continental interiors began to shift, becoming less extreme at the margins, consistent with slightly longer water residence times and modest increases in inland rainfall. Early vascular plants, drawing water from soil and releasing it through transpiration, began extending the reach of ocean moisture a little further inland. They were creating precipitation recycling.

Dan Ibarra, while a postdoc at Stanford, modeled this, demonstrating that the evolution of land plants and the expansion of their transpiration flux produced measurable increases in continental interior rainfall consistent with the geological record [Ibarra 2019]. The effect was limited though. Without deep roots or large leaf surfaces, these early plant communities could intercept and return only modest amounts of water to the atmosphere. They slowed the exponential decay of moisture slightly, nudging rain a little further inland, but not all the way to the interior.

The real transformation came in the late Devonian and into the Carboniferous Period, approximately 359 to 299 million years ago, when the first forests spread across the continents. Now Earth had tall trees with deep roots, dense canopies, and vast swampy ecosystems, and with them came more biological control of the water cycle at continental scale.

. [Carboniferous period 359-299 million years ago]

The geomorphic record captures this transition. The shift from braided to meandering river systems, a fingerprint of vegetation stabilizing floodplains and moderating flow, occurs broadly across this interval in multiple continental sequences. Evaporite deposition in continental interiors declined dramatically through the Carboniferous, consistent with rainfall now penetrating far inland, water residence times lengthening substantially, and basins becoming well connected to drainage networks. This was a different order of change from what early vascular plants had produced. Where those earlier communities had only slowed the inland decay of moisture, forests broke it. A single large tree can transpire hundreds of liters of water a day across multiple layers of leaves, returning that water to the atmosphere to fall again further inland. A forest does this across millions of trees simultaneously, passing moisture from canopy to cloud to rain in a relay that can carry ocean water deep into continental interiors that had previously been hydrological dead zones.

Forests help make rain. But forests do not exist in isolation. They grow out of a foundational layer of bacteria and fungi that has been here far longer, and that layer is not merely supporting the forest. It is actively involved in making the rain alongside it.

Over the past half century, a convergence of ideas across biology, ecology, and Earth science has led some portion of scientists to see life not so much as made of individuals but as assemblies, layered systems in which microbes and fungi are not supporting actors but foundational ones. Plants and animals are not separate from this microbial world. They are built within it, and sustained by it.

Lynn Margulis’s work on endosymbiosis showed that the cells of every plant and animal are themselves mergers of once-independent bacteria. The mitochondria that power our cells, and the chloroplasts that enable plants to photosynthesize, were not invented from scratch. They were absorbed. If the most basic units of complex life are already symbiotic, then the idea of a clean, autonomous organism begins to unravel.

In soils, where most terrestrial life begins, the visible world of roots and stems is embedded in a dense, dynamic microbial matrix. Bacteria and fungi break down rock, recycle nutrients, and structure the physical environment in which plants grow. Plants do not simply draw nutrients from this world. They are entangled with it. Through their roots, they trade carbon for minerals, shaping the microbial communities around them even as those communities shape what the plant can access. The forest ecologist Suzanne Simard demonstrated that trees linked by mycorrhizal fungi transfer carbon and nutrients between one another, sometimes sustaining younger or stressed neighbors [Simard 1997, 2004]. A forest viewed this way is not a collection of competing individuals but a connected network, its members linked by flows of matter moving through fungal pathways. Competition and conflict still exist, but the unit of life is larger and more entangled than it appears at first glance.

The biologist Scott Gilbert has helped formalize this thinking through the concept of the holobiont: an organism together with all of its associated microorganisms, functioning as a single ecological and evolutionary unit. A tree is not just tree tissue. It is tree plus fungi plus microbiome, inseparable in practice even if distinguishable in theory.

This reframing matters when we ask who is making the rain. If the unit of life is the holobiont, then transpiration is not simply something a tree does. It is something the assembly does: plant tissue providing the leaf surface and vascular architecture, mycorrhizal fungi regulating how water moves through roots and how stomata respond to moisture stress, bacteria influencing the molecular signals that govern when pores open and close. Mohanned Abdalla, a soil physicist, and Mutez Ali Ahmed, a horticulture researcher measured how arbuscular mycorrhizal fungi affect the transpiration rates of tomatoes under varying moisture conditions [Mohanned 2012]. Robert Augé, Heather Toler, and Arnold Saxton at the University of Tennessee found that these fungi weave themselves into plant roots and exert a controlling influence over stomatal conductance, the process by which a plant opens its leaf pores to breathe and transpire [2015]. University of California Riverside’s Shushu Jiang and collaborators found that bacteria affect transpiration through protein signaling pathways [2013]. These research groups were not asking what this means for rainfall. But the mechanism they identified operates at every scale. Across millions of trees, fungal and bacterial regulation of stomatal behavior shapes the timing and volume of transpiration. Transpiration thus is not a purely botanical process, its also a microbial and fungal one.

[Transmission Electron Microscope picture of Pseudomonas Syringae]

Cloud drops do not form simply because humidity is high enough. They also require a small particle, called an aerosol, on which to nucleate. Meteorologists have tended to focus on inorganic material seeding rain, but microbes and fungal spores can also seed rain. The ability of bacteria to seed rain was first discovered by Gabor Vali and Russell Schnell in the 1970s, then rediscovered by plant pathologist David Sands in the 1980s, as he hung out of biplanes with a Petri dish to capture bacteria from clouds. A particular bacterium, Pseudomonas syringae, had a protein pattern on its surface that helped reorganize water molecules into ice structures. Proteins on the bacterial outer membrane act as physical templates that force water molecules into a crystalline ice lattice at temperatures as warm as -2°C, far warmer than the -15°C typically required for inorganic dust to trigger freezing. The idea that bacteria and fungal spores could seed rain was considered outlandish at first, but as decades passed it has become increasingly mainstream in climate science. Atmospheric scientist Kim Prather, flying collection missions over parts of the United States, found that a third of rain-seeding particles were of biological origin. Christian Pöhlker and colleagues going into remote parts of the Amazon found that bioaerosols, organic matter including fungal spores, bacteria, and forest terpenes that seed rain, were even more prevalent in pristine forest air, where the ratio of biological to inorganic nucleators was far higher than in polluted or degraded regions [2012]. In prehistoric times, before industrial pollution and large-scale deforestation, we can expect that bacteria and fungal spores played a considerably larger role in creating rain than they do today. [For more info see my articles on the science and discovery of bioaerosols Part I, Part II, and Part III]

[Scanning Electron Microscope pictures of fungal spores]

Forests also exhale tiny organic particles of their own. Conifers, broad-leaved trees, and many other plants release volatile organic compounds, terpenes, the molecules responsible for the resinous smell of pine forests, that react in the atmosphere with ozone and hydroxyl radicals to form secondary organic aerosols in the right size range to act as cloud condensation nuclei. Forests continuously manufacture the seeds around which cloud droplets form, chemically altering the atmosphere above them to make rainfall more probable over the very terrain that produced the aerosols.

The microbiologist Cindy Morris has studied the evolution of the bacterial bioaerosol capacities from a deep-time perspective [Morris 2012]. The rise of flowering plants and vast forests created thermal plumes that lifted bacteria high into the atmosphere, while the breakup of Pangaea created new coastlines and the cool, moist mixed-phase clouds that bacteria need to trigger precipitation. In this environment, selection favored ice-nucleating ability as a solution to long-distance dispersal: bacteria that could seed clouds and trigger their own descent via rain were more likely to reach fresh plant hosts. Once on the ground, the moisture from the rain they helped create facilitates a population explosion, often increasing bacterial numbers a thousandfold in 48 hours, while frost from ice nucleation ruptures plant cells to release nutrients. Through this feedback loop, these microbes have co-evolved with land plants to help manufacture the humid, temperate conditions they both require.

A similar logic applies to fungal spores. Spore lineages that are efficient ice nucleators would be selected for, since triggering rain increases the chance of landing on moist, receptive ground where germination is possible. The diversity of spore types in any given air mass is not noise in the system but functional variety, with rain-seeding specialists doing one job and other lineages doing others. Some are optimized for long atmospheric journeys; others for rapid germination once they land; others for establishing mycorrhizal networks quickly in disturbed soil. The ecosystem benefits from both the seeders and the settlers.

The question of how such a system assembled itself points toward selection operating at multiple levels simultaneously. At the level of the individual organism, a bacterium capable of nucleating ice in clouds is more likely to be carried down in precipitation onto a moist plant surface where it can reproduce. A fungal spore that efficiently seeds rain is more likely to land on receptive, wet ground where germination is possible. A mycorrhizal network that regulates transpiration in ways that sustain local humidity is more likely to persist in a living, productive forest than one that allows its host to desiccate. Each organism is selected for traits that incidentally contribute to moisture cycling. No individual needs to intend the larger effect. Cindy Morris has made precisely this argument for ice-nucleating bacteria: their rain-seeding capacity is not an accident but a dispersal strategy, refined by selection over hundreds of millions of years.

But individual selection alone does not fully account for the integration we observe. Group selection, largely dismissed after George Williams’s critiques in the 1960s, has been substantially rehabilitated in recent decades through evolutionist David Sloan Wilson’s multilevel selection framework and through the study of major evolutionary transitions. In ecological systems especially, the community is increasingly recognized as a genuine unit on which selection can act.

A forest-soil community with tightly integrated microbe-fungi-plant relationships, one whose mycorrhizal networks efficiently regulate transpiration, whose bacterial populations actively seed rain, whose fungal spores and terpene aerosols prime the atmosphere above it, will maintain and colonize new territory more successfully than a community lacking that integration. It will draw more moisture inland, sustain productivity through dry periods, recover more quickly from disturbance, and push its margins further into previously arid continental interiors. Selection at the individual level and selection at the community level are not competing explanations here. They are mutually reinforcing. Individual bacteria, spores, and fungal networks are selected for traits that benefit the community water cycle, and communities with more of those traits outcompete and displace those without them.

The deep history of rain on land is a story about what bacteria and fungi made possible, about how they broke the rock and built the soil, how they impacted transpiration and primed the clouds, and how they co-evolved with plants across hundreds of millions of years into communities capable of carrying rain deep into continental interiors that would otherwise receive almost none.

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If you are interested in reading more on this topic, see my article “Is the earth microbiome regulating our climate?”

References

Abdalla, Mohanned, and Mutez Ali Ahmed. “Arbuscular mycorrhiza symbiosis enhances water status and soil-plant hydraulic conductance under drought.” Frontiers in Plant Science 12 (2021): 722954.

Augé, Robert M., Heather D. Toler, and Arnold M. Saxton. "Arbuscular mycorrhizal symbiosis alters stomatal conductance of host plants more under drought than under amply watered conditions: a meta-analysis." Mycorrhiza 25, no. 1 (2015): 13-24.

Ibarra, Daniel E., Jeremy K. Caves Rugenstein, Aviv Bachan, Andrés Baresch, Kimberly V. Lau, Dana L. Thomas, Jung-Eun Lee, C. Kevin Boyce, and C. Page Chamberlain. “Modeling the consequences of land plant evolution on silicate weathering.” American Journal of Science 319, no. 1 (2019): 1-43.

Jiang, Shushu, Jian Yao, Ka-Wai Ma, Huanbin Zhou, Jikui Song, Sheng Yang He, and Wenbo Ma. “Bacterial effector activates jasmonate signaling by directly targeting JAZ transcriptional repressors.” PLoS pathogens 9, no. 10 (2013): e1003715.

Morris, Cindy E., Franz Conen, J. Alex Huffman, Vaughan Phillips, Ulrich Pöschl, and David C. Sands. “Bioprecipitation: a feedback cycle linking Earth history, ecosystem dynamics and land use through biological ice nucleators in the atmosphere.” Global change biology 20, no. 2 (2014): 341-351.

Pöhlker, Christopher, Kenia T. Wiedemann, Bärbel Sinha, Manabu Shiraiwa, Sachin S. Gunthe, Mackenzie Smith, Hang Su et al. “Biogenic potassium salt particles as seeds for secondary organic aerosol in the Amazon.” Science 337, no. 6098 (2012): 1075-1078 https://www.science.org/doi/abs/10.1126/science.1223264

DC Sands, VE Langhans, AL Scharen, G de Smet, The association between bacteria and rain and possible resultant meteorological implications. J Hungarian Meteorol Serv 86, 148–152 (1982)

Schnell, Russell C., and Gabor Vali. “Looking back: An account of how ice nucleation by bacteria was discovered (1963 to about mid-1980s). Part II: Broadening the scope.” Bulletin of the American Meteorological Society 105, no. 6 (2024): E1004-E1014. https://journals.ametsoc.org/view/journals/bams/105/6/BAMS-D-23-0115.1.xml

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Suzanne W Simard and Daniel M Durall. 2004. Mycorrhizal networks: a review of their extent, function, and importance. Canadian Journal of Botany. 82(8): 1140-1165. https://doi.org/10.1139/b04-116

Vali, Gabor, and Russell C. Schnell. “Looking back: An account of how ice nucleation by bacteria was discovered (1963 to about mid-1980s). Part I: The basics.” Bulletin of the American Meteorological Society 105, no. 4 (2024): E778-E788. https://journals.ametsoc.org/view/journals/bams/105/4/BAMS-D-23-0114.1.xml

My journey into water began in the permaculture and ecorestoration world, where people were talking about how trees can create rain through transpiration, and how, somehow, scientists had overlooked this important phenomenon. With a background in physics, I was intrigued by the idea of vegetation-generated rainfall and wanted to understand the science behind it.

To my surprise, the deeper I looked, the more I realized that scientists had, in fact, been studying this phenomenon extensively. There is a vast body of research on the subject, it’s just been siloed from practitioners. Scientists in turn did not know there were a lot of eco and water restoration people very interested in this topic. I began to see how important it was to connect the ecorestoration and water cycle restoration communities with scientists, and for both groups to engage more closely with governance and policy makers.

With that in mind, I’ve compiled what I believe are some of the most important papers in the evolution of this precipitation recycling/small water cycle field.

As you read through the titles, you may notice the wide range of themes on this topic. Arranged chronologically, the papers reveal how different lines of inquiry into precipitation recycling have developed in parallel over time, which I find fascinating. I’ve marked what I personally think are the coolest papers with a * . There are papers about the use of stable isotopes, various observational studies, and climate models to show precipitation recycling. There is work showing how land degradation and deforestation affects rain, work reviewing how land use change in general affects precipitation, and how to understand the forests total role to the water cycle. There is work on teleconnections, how deforestation on one continent affects rain on another. There is work on how soil moisture can improve weather forecasts of rain. There are various papers on how different scientists worked to define precipitation recycling and what numbers to put on it. I’ve included research on how bacteria and fungi can help seed rainfall, since land use directly affects the abundance of these organisms.

I’m fascinated by how a scientific field evolves. Through my podcast, I’ve had the honor to interview several researchers who have helped shape our understanding of precipitation recycling, and whose numerous papers are to be found below. These include Millan Millan, who investigated how much land needs to be restored to bring back rainfall and proposed a rough benchmark of 6×6 miles (10×10 km). His work with the European Union explored why Spain was losing rainfall, linking it to deforestation, wetland drainage, and land paving, all of which disrupt evapotranspiration. I’ve spoken with Anastasia Makarieva, who, along with the late Victor Gorshkov, developed the biotic pump theory. This theory describes how forests draw in ocean moisture by transpiring enough water to influence large-scale atmospheric circulation. I’ve interviewed Francina Dominguez, who has mapped out the movement of precipitation recycling across South America and the United States, Ruud van der Ent who came up with the global map of where evapotranspiration was rising and where it came down, Wang Lan Erlandsson who developed the idea of planetary green water boundaries which is connected with how much water our vegetation has to transpire to create rain, when we cross those boundaries it lessens our rains, and Patrick Keys, who developed with van der Ent the idea of precipitationsheds, which is the range of area where water evapotranspires to provide rain for a particular local area. Patrick Keys also mapped out how much different cities depend on precipitation recycling and the quality of land in nearby areas to generate that rain.

You can explore these papers through Google Scholar, where links to full texts are sometimes available. You can also use DOI numbers, which you can get from Google Scholar, to locate papers through other repositories like sci-hub.su where you can then read them for free.

The papers:

Holzman, Benjamin. Sources of moisture for precipitation in the United States. No. 1488-2016-124521. 1937

Budyko, M. I., and O. A. Drozdov. “Characteristics of the moisture circulation in the atmosphere.” Izv. Akad. Nauk SSSR Ser. Geogr. Geofiz 4 (1953)

*Manabe, Syukuro. "Climate and the ocean circulation: I. The atmospheric circulation and the hydrology of the earth's surface." Monthly weather review 97, no. 11 (1969): 739-774.

Vali, Gabor, and Russell Schnell. "Contribuition of natural feezing nuclei to precipitation development” In Preprints of Papers Presented at the Conference on Cloud Physics: August 24-27, 1970, Ft. Collins, Colorado, p. 41. American Meteorological Society, 1970

*Schnell, R., Vali, G. Atmospheric Ice Nuclei from Decomposing Vegetation. Nature 236, 163–165 (1972). https://doi.org/10.1038/236163a0

*Charney, Jules G. "Dynamics of deserts and drought in the Sahel." Quarterly Journal of the Royal Meteorological Society 101, no. 428 (1975): 193-202.

Charney, Jule, Peter H. Stone, and William J. Quirk. “Drought in the Sahara: a biogeophysical feedback mechanism.” Science 187, no. 4175 (1975)”

Walker, Julia, and P. R. Rowntree. "The effect of soil moisture on circulation and rainfall in a tropical model." Quarterly Journal of the Royal Meteorological Society 103, no. 435 (1977)

*Salati, Eneas, Attilio Dall'Olio, Eiichi Matsui, and Joel R. Gat. "Recycling of water in the Amazon Basin: An isotopic study." Water resources research 15, no. 5 (1979): 1250-1258

Kurbatkin, G. P., S. Manabe, and D. G. Hahn. "Moisture content of the continents and the intensity of the summer monsoon circulation” Soviet meteorology and hydrology 11 (1979) https://disk.yandex.ru/i/V3WdQq5-uf8Oag

Lettau, H., K. Lettau, and L. C. B. Molion, 1979: Amazonia’s Hydrologic Cycle and the Role of Atmospheric Recycling in Assessing Deforestation Effects. Mon. Wea. Rev., 107, 227–238, https://doi.org/10.1175/1520-0493(1979)107<0227:AHCATR>2.0.CO;2

*Meher-Homji, V. M. "Repercussions of deforestation on precipitation in Western Karnataka, India." Theoretical and Applied Climatology 28, no. 4 (1980): 385-400

Charney, J. G., and J. Shukla. "Monsoon Dynamics: Predictability of Monsoons, edited by: Lighthill, J. and Pearce, R." (1981).

*Shukla, Jagdish, and Yale Mintz. "Influence of land-surface evapotranspiration on the earth's climate." Science 215, no. 4539 (1982): 1498-1501.

DC Sands, VE Langhans, AL Scharen, G de Smet, The association between bacteria and rain and possible resultant meteorological implications. J Hungarian Meteorol Serv 86, 148–152 (1982)

Salati, Eneas, T. E. Lovejoy, and P. B. Vose. "Precipitation and water recycling in tropical rain forests with special reference to the amazon basim." Environmentalist 3, no. 1 (1983): 67-72.

Salati, Eneas, and Peter B. Vose. "Amazon basin: a system in equilibrium." Science 225, no. 4658 (1984): 129-138.

Yeh, T., R. T. Wetherald, and S. Manabe, 1984: The Effect of Soil Moisture on the Short-Term Climate and Hydrology Change—A Numerical Experiment. Mon. Wea. Rev., 112, 474–490, https://doi.org/10.1175/1520-0493(1984)112<0474:TEOSMO>2.0.CO;2

Delworth, Thomas L., and Syukuro Manabe. "The influence of potential evaporation on the variabilities of simulated soil wetness and climate." Journal of Climate 1, no. 5 (1988): 523-547.

Delworth, Thomas, and Syukuro Manabe. "The influence of soil wetness on near-surface atmospheric variability." Journal of Climate 2, no. 12 (1989): 1447-1462.

Otterman, J., A. Manes, S. Rubin, P. Alpert, and D. O'C. Starr. "An increase of early rains in southern Israel following land-use change?" Boundary-Layer Meteorology 53 (1990): 333-351

Constantinidou HA, Hirano SS, Baker LS, & Upper CD (1990). Atmospheric Dispersal of Ice Nucleation-Active Bacteria: The Role of Rain Phytopathology (80), 934-937 DOI: 10.1094/Phyto-80-934

Salati, Eneas, and Carlos A. Nobre. "Possible climatic impacts of tropical deforestation." Climatic change 19, no. 1 (1991): 177-196.

Meher-Homji, V. M. “Probable impact of deforestation on hydrological processes.” Climatic Change 19, no. 1-2 (1991): 163-173

Nobre, Carlos A., Piers J. Sellers, and Jagadish Shukla. "Amazonian deforestation and regional climate change." Journal of climate 4, no. 10 (1991): 957-988.

Entekhabi, D., I. Rodriguez-Iturbe, and R. L. Bras, 1992: Variability in Large-Scale Water Balance with Land Surface-Atmosphere Interaction. J. Climate, 5, 798–813,

Milly, P. C. D., and K. A. Dunne, 1994: Sensitivity of the Global Water Cycle to the Water-Holding Capacity of Land. J. Climate, 7, 506–526

Chen F, Avissar R. 1994. Impact of land-surface moisture variability on local shallow convective cumulus and precipitation in large-scale models. Journal of Applied Meteorology 33

*Savenije, Hubert HG. “Does moisture feedback affect rainfall significantly?.” Physics and Chemistry of the Earth 20, no. 5-6 (1995): 507-513 https://www.sciencedirect.com/science/article/abs/pii/S0079194696000146

*Savenije, Hubert HG. "New definitions for moisture recycling and the relationship with land-use changes in the Sahel." Journal of Hydrology 167, no. 1-4 (1995): 57-78.

Xue, Yongkang, and Jagadish Shukla. "The influence of land surface properties on Sahel climate. Part II: Afforestation." Journal of Climate (1996): 3260-3275.

*Eltahir, Elfatih AB, and Rafael L. Bras. "Precipitation recycling." (1996) https://doi.org/10.1029/96RG01927

Savenije, Hubert HG. "New definitions for moisture recycling and the relationship with land-use changes in the Sahel." Journal of Hydrology 167, no. 1-4 (1995): 57-78.

*Findell, Kirsten L., and Elfatih A. B. Eltahir. “An Analysis of the Soil Moisture‐rainfall Feedback, Based on Direct Observations from Illinois.” Water Resources Research, ahead of print, 1997. https://doi.org/10.1029/96WR03756.

Andreae, Meinrat O., and Paul J. Crutzen. "Atmospheric aerosols: Biogeochemical sources and role in atmospheric chemistry." Science 276, no. 5315 (1997): 1052-1058 https://sci-hub.ru/10.1126/science.276.5315.1052

Brovkin, V., Claussen, M., Petoukhov, V., and Ganopolski, A. (1998), On the stability of the atmosphere-vegetation system in the Sahara/Sahel region, J. Geophys. Res., 103( D24), 31613– 31624, doi:10.1029/1998JD200006

Segal M, Avissar R, McCumber MC, Pielke RA. 1988. Evaluation of vegetation effects on the generation and modification of mesoscale circulations. Journal of the Atmospheric Sciences 45

*Claussen, M. (1998). On multiple solutions of the atmosphere-vegetation system in present-day climate. Global Change Biology, 4(5), 549-559. doi:10.1046/j.1365-2486.1998.00122.x

Fraedrich K, Kleidon A, Lunkeit F. A green planet versus a desert world: estimating the effect of vegetation extremes on the atmosphere. J Clim (1999)

Wang G, Eltahir EAB. Ecosystem dynamics and the Sahel drought. Geophys Res Lett 2000

Doherty, Ruth, J. Kutzbach, J. Foley, and D. Pollard. "Fully coupled climate/dynamical vegetation model simulations over Northern Africa during the mid-Holocene." Climate Dynamics 16 (2000)

Burde, G. I., and A. Zangvil. "The estimation of regional precipitation recycling. Part I: Review of recycling models." Journal of climate 14, no. 12 (2001): 2497-2508.

*Fu, Rong, and Wenhong Li. "The influence of the land surface on the transition from dry to wet season in Amazonia." Theoretical and applied climatology 78 (2004)

*Millán, M. M., and Coauthors, 2005: Climatic Feedbacks and Desertification: The Mediterranean Model. J. Climate, 18, 684–701

Pielke Sr, Roger A. "Land use and climate change." Science 310, no. 5754 (2005): 1625-1626

Jung-Eun Lee, Rafael Oliveira, Todd E Dawson, Inez Fung “Root functioning modifies seasonal climate” November 21, 2005 102 (49) 17576-17581 https://doi.org/10.1073/pnas.0508785102

Koster, R. D., and Coauthors, 2006: GLACE: The Global Land–Atmosphere Coupling Experiment. Part I: Overview. J. Hydrometeor., 7, 590–610, https://doi.org/10.1175/JHM510.1

Guo, Zhichang, Paul A. Dirmeyer, Randal D. Koster, Y. C. Sud, Gordon Bonan, Keith W. Oleson, Edmond Chan et al. “GLACE: the global land–atmosphere coupling experiment. Part II: analysis.” Journal of Hydrometeorology 7, no. 4 (2006)

Cook, Benjamin I., Gordon B. Bonan, and Samuel Levis. "Soil moisture feedbacks to precipitation in southern Africa." Journal of Climate 19, no. 17 (2006): 4198-4206.

Donohue, R. J., M. L. Roderick, and T. R. McVicar. “On the Importance of Including Vegetation Dynamics in Budyko’s Hydrological Model.” Hydrol. Earth Syst. Sci., 2007.

*Makarieva, A. M., & Gorshkov, V. G. (2007). Biotic pump of atmospheric moisture as driver of the hydrological cycle on land. Hydrology and earth system sciences

*Trenberth, Kevin E., Lesley Smith, Taotao Qian, Aiguo Dai, and John Fasullo. “Estimates of the global water budget and its annual cycle using observational and model data.” Journal of Hydrometeorology 8, no. 4 (2007): 758-769.

Schneider, N., Eugster, W. Climatic impacts of historical wetland drainage in Switzerland. Climatic Change 80, 301–321 (2007). https://doi.org/10.1007/s10584-006-9120-8

Pielke Sr, Roger A., Jimmy Adegoke, A. BeltraáN-Przekurat, Christopher A. Hiemstra, John Lin, Udaysankar S. Nair, Dev Niyogi, and Timothy E. Nobis. "An overview of regional land-use and land-cover impacts on rainfall." Tellus B: Chemical and Physical Meteorology 59, no. 3 (2007): 587-601.

Bonan, Gordon B. "Forests and climate change: forcings, feedbacks, and the climate benefits of forests." science 320, no. 5882 (2008): 1444-1449.

*Christner, Brent C., Cindy E. Morris, Christine M. Foreman, Rongman Cai, and David C. Sands. "Ubiquity of biological ice nucleators in snowfall." Science 319, no. 5867 (2008): 1214-1214.

B. Bisselink and A. J. Dolman, “Precipitation Recycling: Moisture Sources over Europe using ERA-40 Data,” Journal of Hydrometeorology, vol. 9, no. 5, pp. 1073–1083, Oct. 2008, doi: 10.1175/2008JHM962.1

Makarieva, Anastassia M., Victor G. Gorshkov, and Bai-Lian Li. "Precipitation on land versus distance from the ocean: evidence for a forest pump of atmospheric moisture." Ecological complexity 6, no. 3 (2009): 302-307.

Junkermann, W., Jorg Hacker, T. Lyons, and Udaysankar Nair. "Land use change suppresses precipitation." Atmospheric Chemistry and Physics 9, no. 17 (2009): 6531-6539.

Hoose C, Kristjánsson JE, & Burrows SM (2010). How important is biological ice nucleation in clouds on a global scale? Environmental Research Letters, 5 (2) DOI: 10.1088/1748-9326/5/2/024009

Makarieva, Anastassia M., and Victor G. Gorshkov. "The Biotic Pump: Condensation, atmospheric dynamics and climate." International Journal of Water 5, no. 4 (2010): 365-385.

*Van der Ent, Rudi J., Hubert HG Savenije, Bettina Schaefli, and Susan C. Steele‐Dunne. "Origin and fate of atmospheric moisture over continents." Water Resources Research 46, no. 9 (2010)

Li, L., Jiang, X., Chahine, M. T., Olsen, E. T., Fetzer, E. J., Chen, L., & Yung, Y. L. (2011). The recycling rate of atmospheric moisture over the past two decades (1988-2009). Environmental Research Letters, 6(3), 034018. https://doi.org/10.1088/1748-9326/6/3/034018

Sesartic A., Lohmann U., & Storelvmo T. (2011). Bacteria in the ECHAM5-HAM global climate model Atmos. Chem. Phys. Discuss., 11, 1457-1488 DOI: 10.5194/acpd-11-1457-2011

Taylor, Christopher M., Richard A. M. de Jeu, Françoise Guichard, Phil P. Harris, and Al Et. “Afternoon Rain More Likely over Drier Soils.” Nature, ahead of print, 2012. https://doi.org/10.1038/nature11377.

Keys, Patrick W., R. J. Van der Ent, Line J. Gordon, Holger Hoff, R. Nikoli, and H. H. G. Savenije. "Analyzing precipitationsheds to understand the vulnerability of rainfall dependent regions." Biogeosciences 9, no. 2 (2012): 733-746.

*Ellison, David, Martyn N. Futter, and Kevin Bishop. "On the forest cover–water yield debate: from demand‐to supply‐side thinking." Global change biology 18, no. 3 (2012): 806-820.

Gimeno, Luis, Andreas Stohl, Ricardo M. Trigo, Francina Dominguez, Kei Yoshimura, Lisan Yu, Anita Drumond, Ana María Durán‐Quesada, and Raquel Nieto. "Oceanic and terrestrial sources of continental precipitation." Reviews of Geophysics 50, no. 4 (2012).

Woldemichael, Abel T., Faisal Hossain, Roger Pielke Sr, and Adriana Beltrán‐Przekurat. "Understanding the impact of dam‐triggered land use/land cover change on the modification of extreme precipitation." Water Resources Research 48, no. 9 (2012).

*Swann, Abigail LS, Inez Y. Fung, and John CH Chiang. "Mid-latitude afforestation shifts general circulation and tropical precipitation." Proceedings of the National Academy of Sciences 109, no. 3 (2012): 712-716.

D’Odorico, Paolo, Abinash Bhattachan, Kyle F. Davis, Sujith Ravi, and Christiane W. Runyan. "Global desertification: Drivers and feedbacks." Advances in water resources 51 (2013)

Makarieva, Anastassia M., Victor G. Gorshkov, and Bai-Lian Li. "Revisiting forest impact on atmospheric water vapor transport and precipitation." Theoretical and Applied Climatology 111, no. 1 (2013): 79-96.

Morris C, Monteil C, Berge O “The Life History of Pseudomonas syringae: Linking Agriculture to Earth System Processes” Annual Review of Phytopathology Vol. 51:85-104 (August 2013) https://doi.org/10.1146/annurev-phyto-082712-102402

Creamean, Jessie M., Kaitlyn J. Suski, Daniel Rosenfeld, Alberto Cazorla, Paul J. DeMott, Ryan C. Sullivan, Allen B. White et al. "Dust and biological aerosols from the Sahara and Asia influence precipitation in the western US." science 339, no. 6127 (2013): 1572-1578.

Millán, Millán M. "Extreme hydrometeorological events and climate change predictions in Europe." Journal of Hydrology 518 (2014): 206-224.

Meng, Lei, Di Long, Steven M. Quiring, and Yanjun Shen. "Statistical analysis of the relationship between spring soil moisture and summer precipitation in East China." International Journal of Climatology 34, no. 5 (2014

Martinez, J. Alejandro, and Francina Dominguez. "Sources of atmospheric moisture for the La Plata River basin." Journal of Climate 27, no. 17 (2014): 6737-6753.

Spracklen, D. V. and Heald, C. L.: The contribution of fungal spores and bacteria to regional and global aerosol number and ice nucleation immersion freezing rates, Atmos. Chem. Phys., 14, 9051–9059, https://doi.org/10.5194/acp-14-9051-2014, 2014.

Keys, Patrick W., E. A. Barnes, R. J. Van Der Ent, and Line J. Gordon. "Variability of moisture recycling using a precipitationshed framework." Hydrology and Earth System Sciences 18, no. 10 (2014): 3937-3950.

Bagley, J. E., A. R. Desai, K. J. Harding, P. K. Snyder, and J. A. Foley, 2014: Drought and Deforestation: Has Land Cover Change Influenced Recent Precipitation Extremes in the Amazon?. J. Climate, 27, 345–361, https://doi.org/10.1175/JCLI-D-12-00369.1

Gloor, M., Jonathan Barichivich, Guy Ziv, R. Brienen, Jochen Schöngart, Philippe Peylin, B. Barcante Ladvocat Cintra, T. Feldpausch, O. Phillips, and J. Baker. “Recent Amazon climate as background for possible ongoing and future changes of Amazon humid forests.” Global Biogeochemical Cycles 29, no. 9 (2015)

Swann, Abigail LS, Marcos Longo, Ryan G. Knox, Eunjee Lee, and Paul R. Moorcroft. "Future deforestation in the Amazon and consequences for South American climate." Agricultural and Forest Meteorology 214 (2015): 12-24.

Bigg, E. Keith, Samuel Soubeyrand, and Cindy E. Morris. "Persistent after-effects of heavy rain on concentrations of ice nuclei and rainfall suggest a biological cause." Atmospheric Chemistry and Physics 15, no. 5 (2015): 2313-2326.

Martinez, J. Alejandro, Francina Dominguez, and Gonzalo Miguez-Macho. "Impacts of a groundwater scheme on hydroclimatological conditions over southern South America." Journal of Hydrometeorology 17, no. 11 (2016): 2959-2978. https://doi.org/10.1175/JHM-D-16-0052.1

Laguë, Marysa M., and Abigail LS Swann. "Progressive midlatitude afforestation: Impacts on clouds, global energy transport, and precipitation." Journal of Climate 29, no. 15 (2016): 5561-5573.

*Martinez, J. Alejandro, Francina Dominguez, and Gonzalo Miguez-Macho. "Impacts of a groundwater scheme on hydroclimatological conditions over southern South America." Journal of Hydrometeorology 17, no. 11 (2016): 2959-2978

Daniels, Emma, Geert Lenderink, Ronald Hutjes, and Albert Holtslag. "Relative impacts of land use and climate change on summer precipitation in the Netherlands." Hydrology and Earth System Sciences 20, no. 10 (2016): 4129-4142.

*Keys, Patrick W. "The precipitationshed: Concepts, methods, and applications." PhD diss., Stockholm Resilience Centre, Stockholm University, 2016.

Yu, Y., Notaro, M., Wang, F. et al. Observed positive vegetation-rainfall feedbacks in the Sahel dominated by a moisture recycling mechanism. Nat Commun 8, 1873 (2017). https://doi.org/10.1038/s41467-017-02021-1

Ellison, David, Cindy E. Morris, Bruno Locatelli, Douglas Sheil, Jane Cohen, Daniel Murdiyarso, Victoria Gutierrez et al. "Trees, forests and water: Cool insights for a hot world." Global environmental change 43 (2017): 51-61.

Takahashi, Atsuhiro, Tomo’omi Kumagai, Hironari Kanamori, Hatsuki Fujinami, Tetsuya Hiyama, and Masayuki Hara. "Impact of tropical deforestation and forest degradation on precipitation over Borneo Island." Journal of Hydrometeorology 18, no. 11 (2017): 2907-2922.

Marengo, Jose A., Gilberto F. Fisch, Lincoln M. Alves, Natanael V. Sousa, Rong Fu, and Yizhou Zhuang. "Meteorological context of the onset and end of the rainy season in Central Amazonia during the GoAmazon2014/5." Atmospheric Chemistry and Physics 17, no. 12 (2017): 7671-7681.

*Duerinck, Hyo Mee, R. J. Van der Ent, N. C. Van de Giesen, Gerrit Schoups, V. Babovic, and Pat J-F. Yeh. "Observed soil moisture–precipitation feedback in Illinois: A systematic analysis over different scales." Journal of Hydrometeorology 17, no. 6 (2016): 1645-1660. https://doi.org/10.1175/JHM-D-15-0032.1

Tuttle, Samuel E., and Guido D. Salvucci. “Confounding Factors in Determining Causal Soil Moisture‐precipitation Feedback.” Water Resources Research 53, no. 7 (2017): 5531–44. https://doi.org/10.1002/2016WR019869.

*Wright, J.S., Fu, R., Worden, J.R., Chakraborty, S., Clinton, N.E., Risi, C., Sun, Y. and Yin, L., 2017. Rainforest-initiated wet season onset over the southern Amazon. Proceedings of the National Academy of Sciences, 114(32)

Yu, Yan, Michael Notaro, Fuyao Wang, Jiafu Mao, Xiaoying Shi, and Yaxing Wei. “Observed Positive Vegetation-Rainfall Feedbacks in the Sahel Dominated by a Moisture Recycling Mechanism.” Nature Communications 8, no. 1 (2017): 1873. https://doi.org/10.1038/s41467-017-02021-1.

* Keys, Patrick W., Lan Wang-Erlandsson, and Line J. Gordon. "Megacity precipitationsheds reveal tele-connected water security challenges." PLoS One 13, no. 3 (2018): e0194311.

Herrera-Estrada, J. E., Martinez, J. A., Dominguez, F., Findell, K. L., Wood, E. F., & Sheffield, J. (2019). Reduced moisture transport linked to drought propagation across North America. Geophysical Research Letters, 46, 5243– 5253

Yang, Zhao, and Francina Dominguez. "Investigating land surface effects on the moisture transport over South America with a moisture tagging model." Journal of Climate 32, no. 19 (2019): 6627-6644.

Messori, Gabriele, Marco Gaetani, Qiang Zhang, Qiong Zhang, and Francesco SR Pausata. "The water cycle of the mid‐Holocene West African monsoon: The role of vegetation and dust emission changes." International Journal of Climatology 39, no. 4 (2019)

*Sporre, Moa K., Sara M. Blichner, Inger HH Karset, Risto Makkonen, and Terje K. Berntsen. "BVOC–aerosol–climate feedbacks investigated using NorESM." Atmospheric Chemistry and Physics 19, no. 7 (2019): 4763-4782. https://acp.copernicus.org/articles/19/4763/2019/

*O. Branch,V. Wulfmeyer ‘Deliberate enhancement of rainfall using desert plantations’, Proc. Natl. Acad. Sci. U.S.A. 116 (38) 18841-18847, https://doi.org/10.1073/pnas.1904754116 (2019).

Sehler, Robin, Jingjing Li, J. T. Reager, and Hengchun Ye. "Investigating relationship between soil moisture and precipitation globally using remote sensing observations." Journal of Contemporary Water Research & Education 168, no. 1 (2019): 106-118.

Ampuero, A., Nicola M. Stríkis, James Apaéstegui, Mathias Vuille, Valdir F. Novello, Jhan Carlo Espinoza, Francisco W. Cruz et al. "The forest effects on the isotopic composition of rainfall in the northwestern Amazon Basin." Journal of Geophysical Research: Atmospheres 125, no. 4 (2020)

Eiras‐Barca, J., Dominguez, F., Yang, Z., Chug, D., Nieto, R., Gimeno, L., & Miguez‐Macho, G. (2020). Changes in South American hydroclimate under projected Amazonian deforestation. Annals of the New York Academy of Sciences, 1472(1), 104-122.

O'Connor, J. C., Dekker, S. C., Staal, A., Tuinenburg, O. A., Rebel, K. T., & Santos, M. J. (2021). Forests buffer against variations in precipitation. Global Change Biology, 27, 4686– 4696. https://doi.org/10.1111/gcb.15763

Meier, R., Schwaab, J., Seneviratne, S.I. et al. Empirical estimate of forestation-induced precipitation changes in Europe. Nat. Geosci. 14, 473–478 (2021). https://doi.org/10.1038/s41561-021-00773-6

* te Wierik, Sofie A., Erik LH Cammeraat, Joyeeta Gupta, and Yael A. Artzy‐Randrup. "Reviewing the impact of land use and land‐use change on moisture recycling and precipitation patterns." Water Resources Research 57, no. 7 (2021): e2020WR029234.

*Barlage, Michael, Fei Chen, Roy Rasmussen, Zhe Zhang, and Gonzalo Miguez‐Macho. "The importance of scale‐dependent groundwater processes in land‐atmosphere interactions over the central United States." Geophysical Research Letters 48, no. 5 (2021): e2020GL092171.

Zhang, B., Tian, L., Zhao, X. et al. Feedbacks between vegetation restoration and local precipitation over the Loess Plateau in China. Sci. China Earth Sci. 64, 920–931 (2021). https://doi.org/10.1007/s11430-020-9751-8 doi.org/10.1007/s11430-020-9751-8

*Wang-Erlandsson, Lan, Arne Tobian, Ruud J. Van der Ent, Ingo Fetzer, Sofie te Wierik, Miina Porkka, Arie Staal et al. "A planetary boundary for green water." Nature Reviews Earth & Environment 3, no. 6 (2022): 380-392.

*Makarieva, Anastassia M., Andrei V. Nefiodov, Antonio Donato Nobre, Mara Baudena, Ugo Bardi, Douglas Sheil, Scott R. Saleska, Ruben D. Molina, and Anja Rammig. "The role of ecosystem transpiration in creating alternate moisture regimes by influencing atmospheric moisture convergence." Global Change Biology 29, no. 9 (2023): 2536-2556.

Liu, Y., Ge, J., Guo, W., Cao, Y., Chen, C., Luo, X., et al. (2023). Revisiting biophysical impacts of greening on precipitation over the Loess Plateau of China using WRF with water https://doi.org/10.1029/2023GL102809

Staal, Arie, Jolanda JE Theeuwen, Lan Wang‐Erlandsson, Nico Wunderling, and Stefan C. Dekker. "Targeted rainfall enhancement as an objective of forestation." Global Change Biology 30, no. 1 (2024): e17096

*Vali, Gabor, and Russell C. Schnell. “Looking back: An account of how ice nucleation by bacteria was discovered (1963 to about mid-1980s). Part I: The basics.” Bulletin of the American Meteorological Society 105, no. 4 (2024): E778-E788. https://journals.ametsoc.org/view/journals/bams/105/4/BAMS-D-23-0114.1.xml

Sun, Jing, Kun Yang, Xiaogang He, et al. “Causal Pathways Underlying Global Soil Moisture–Precipitation Coupling.” Nature Communications 16 (October 2025): 8935. https://doi.org/10.1038/s41467-025-63999-7.

Gao, Yifu, Runze Li, Efi Foufoula-Georgiou, and Jasper A. Vrugt. “Functional Data Decomposition Reveals Unexpectedly Strong Soil Moisture-Precipitation Coupling over the Great Plains.” arXiv:2506.13939. Preprint, arXiv, June 16, 2025. https://doi.org/10.48550/arXiv.2506.13939.

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*Shukla, Jagadish. A Billion Butterflies: A Life in Climate and Chaos Theory. St. Martin's Press, 2025.

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References

Just kidding. This whole article was references.

First, though, let us clarify what a law is in earth science. It is different from the fundamental laws of nature you find in physics. At the Earth level, laws are emergent. They arise from the interaction of many variables and describe patterns of behavior. These laws are more statistical in nature; they tell us what is most likely to happen given a set of parameters.

Like learning about many laws, this one is built on a number of concepts that one must first understand. Some of these concepts might be unfamiliar, but do not worry, take your time, chew on them, and apply them to different situations. Learning a new concept is like learning new vocabulary. It gives you new ways to talk about phenomena, in this case the water cycle, climate, and eco-restoration.

At the turn of the 20th century, the French geographer De Martonne was trying to understand the world’s biomes and how they relate to climate. He wanted to know why one region is grassland while another is forest, why one is scrubland while another is desert. The first idea might be to think of water availability and rainfall. Consider California and Germany: they have similar rainfall, but rainfall alone does not determine vegetation or biome. Temperature also matters. California is hotter than Germany, and so the air “sucks up” more water. Or consider Senegal and Scotland: both receive similar rainfall, but in Senegal the sun is ferocious, leaving the landscape parched, while Scotland is boggy and marshy. The sun reduces water availability in Senegal more than in Scotland. So De Martonne divided rainfall by temperature. This metric, his dryness index, helped determine which biome occurs where. It worked well enough to produce climate maps approximating actual vegetation.

But De Martonne’s equation had a problem. It assumed a linear relationship: double the temperature, double the drying effect. That was not what the data showed. As temperatures rise, evaporation does not just increase proportionally; it accelerates. The atmosphere’s ability to extract water from soil and plants grows faster than temperature alone predicts, especially at higher heats. The linear equation was an approximation, and in hot climates, it broke down.

In the 1940s, American climatologist Thornthwaite also studied how climate affected biomes. He wanted something that captured the atmosphere’s actual “sucking power” more precisely. He called it potential evapotranspiration (PET), which directly quantified how much water the atmosphere would pull out if water were freely available. Consider a cloth periodically sprayed with water and left under a heat lamp. The amount of water sprayed divided by the potential evapotranspiration the lamp can induce gives a dryness index. If the lamp can evaporate more water than is in the cloth, the system is arid; if not, it is humid. In Senegal, potential evapotranspiration is high, whereas in Scotland, it is low. Dividing rainfall by potential evapotranspiration gives an aridity index, providing a better sense of water availability. This improved upon De Martonne’s method.

Mikhail Budyko, from the Soviet Union, was a pioneer of modern climate science. He helped us understand Earth’s heat balance and climate. He was curious about what drove rainfall and evaporation worldwide. Budyko was interested in “energy limits” as a universal principle, not just for Earth’s water cycle but as a way to understand ecosystems on other planets. He also was not just a climate scientist; he had a deep interest in long-term human adaptation to climate and in the 1970s, he developed one of the earliest models estimating how global warming could affect human settlements, agriculture, and freshwater availability, decades before climate change became a mainstream concern.

Budyko took Thornwaithe’s ideas to the next stage. He defined the idea of water-limited landscapes and energy-limited landscapes. Consider a terrarium where you can vary the water supply and the heat lamp shining on it. If you have little water, the system is water-limited because the heat lamp can evaporate more than is available. If it is a cold room, the lamp is weak, and there is plenty of water, the system is energy-limited because circulation is constrained by energy. Senegal is water-limited, Scotland is energy-limited, the Amazon is energy-limited, and Arizona is water-limited. Budyko sought a universal law of how the sun drives water around the world. Using the terrarium analogy, he wanted to understand how water behaves as you vary the heat lamp temperature and water quantity.

He took the evaporative index (actual evapotranspiration divided by precipitation) and utilized it in his theory. This evaporative index gives you a sense of how much evapotranspiration is happening in an area relative to the rain that falls in the area. In Scotland, this index is low; in Senegal, it is high.

He then plotted this evaporative index vs the aridity index. And saw it had a pattern. So in the plot below each red dot is a place in the world, and the x-axis is the aridity index and the y-axis is the evaporative index. To the left hand side is where aridity index is below one, so the climate is more arid, it is water limited. To the right hand side is where the aridity index is above one, so the climate is more humid, it is energy limited.

The red dots in the plot below are not just scattered randomly. There is a pattern to them. This is an emergent law of behavior of the water cycle. Now if you are interested in a puzzle before reading on, try to figure out why the red dots are distributed this way. What is the connection of the aridity (in the x axis) with the evaporative index, the ratio of evaporatranspiration to rain (in the y axis)?

Budyko’s curve shows that Scotland, with low aridity, is energy-limited, while Senegal, with high aridity, is water-limited and has a higher evaporative index. In essence, the climate’s “thirst,” captured by the aridity index, largely controls how much water evaporates. So you don’t see lower red dots on right hand side, because when you have more ‘sucking power’ then there will be more evaporation and a higher evaporative index. When you have a lower aridity index, meaning a lower sucking power, on the left hand side of the plot, the red dots will be have a lesser y axis value because the lower sucking power leads to a lower evaporative index. In a terrarium with higher heat lamp but lesser water you would be on the right hand side of the diagram, with a higher sucking power (higher aridity index) leading to a higher evaporation (higher evaporative index). In a terrarium with lower heat lamp to water availabity ratio, you would be on the left hand side, and have lower aridity and sucking power leading to lower evaporative index. The x-axis determines the y-axis, providing a universal framework linking global climate dryness to the fraction of rainfall cycling back into the atmosphere. This is the law of the global water cycle.

Budyko viewed the Earth as a self-regulating system, where diverse ecosystems, from the Sahara to the Amazon, emerge from a balance of energy. If you crank up the heat on a stove without adding water, the pan dries and becomes scorching, which represents the water-limited regime of a desert. If you flood the pan, the temperature is capped by how fast water turns to steam, which represents the energy-limited regime of a rainforest. Budyko’s insight was realizing the Earth constantly seeks a balance between these extremes.

Budyko’s curve impacted hydrology and climate science. Before Budyko, hydrology was site-specific. After him, hydrologists recognized universal patterns: runoff and water budgets could be inferred from the aridity and evaporative indices alone. In climate science, the curve helped categorize regions as water-limited or energy-limited. It helped scientists determine evapotranspiration and precipitation based on more general principles.

As important, and as universal as Budkyo’s curve turned out to be, it wasn’t done evolving. As more research was done on this curve, researchers realized there were actually many curves. Soil and vegetation influence water storage and evapotranspiration, represented by a parameter w. Well-restored forests and soils increase w, degraded landscapes reduce it. This allows finer predictions of how landscapes respond to precipitation. So curves with higher w are higher up in Budyko’s curve plot.

This framework is useful for ecorestoration. Seasonal shifts can move a site from water-limited (dry season) to energy-limited (wet season). Reducing floods in the wet season involves moving an energy-limited landscape rightward on the curve, enhancing evapotranspiration through planting trees, expanding wetlands, and increasing vegetation cover. Mitigating drought involves moving water-limited landscapes leftward, restoring soil structure, increasing organic matter, and creating retention features like ponds and swales.

Here is the Budyko curve for the Okefenokee swamp area in Georgia [Corak 2026] which experienced fire. The AET/P is actual evapotranspiration divided by precipitation which is the evaporative index. The PET/P is the potential evapotranspiration divided by precipitation which is the aridity index. The blue triangles are pre-fire. After the fire you can see they move to a lower curve. If we want to stop the drought-fire-flood fire cycle its important that we move lower points back up to higher curves through restoring soil and the water cycle.

The Budyko curve clarifies which restoration actions are most important where. In arid areas like the Sahel, capturing rainfall with zai pits (which are indentations in the land) and planting grasses is critical before tree planting. As areas become less arid, tree planting can proceed with less concern about water capture. Restoration gradually moves landscapes toward curves with higher water retention and evapotranspiration, increasing resilience to drought and floods.

The Budyko curve can track eco-restoration progress worldwide, monitoring individual sites and observing global shifts in the constellation of points on the plot. It is a unifying law of water, bridging eco-restorers, permaculturists, regenerative agriculture practitioners, ecologists, hydrologists, and climate scientists.

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References

A video about Budyko curve

Berghuijs, W., and P. Greve. "A review of the Budyko water balance framework." Proceedings of the EGU General Assembly, Vienna, Austria (2015): 12-17.

Nicholas K. Corak, Ana P. Barros, Lauren E.L. Lowman, Budyko scatter reveals interactions between wildfire, land cover change, and climate, Journal of Hydrology, Volume 669, Part A,2026,135096,ISSN 0022-1694,https://doi.org/10.1016/j.jhydrol.2026.135096

Reaver, Nathan George Frederick, David Kaplan, Harald Klammler, and James Jawitz. "Explicit Analytical Inversion of the Parametric Budyko Equations." Available at SSRN 4949309 (2024)

Wang, Cong, Shuai Wang, Bojie Fu, and Lu Zhang. "Advances in hydrological modelling with the Budyko framework: A review." Progress in Physical Geography 40, no. 3 (2016): 409-430.

Zhang, L., Dawes, W. R., and Walker, G. R.: Response of mean annual evapotranspiration to vegetation changes at catchment scale, Water Resour. Res., 37, 701–708, 2001.

Actual catchments have points moving around curves, as shown in diagram below. Explained in this video

[Reaver 2022]

Restoring the world’s water cycles is a craft, one that takes time to learn, and a community to grow within. That community is being built.

Water Stories is an education platform, community network, and hands-on career pathway dedicated to restoring the world’s water. It has been quietly growing, building a network of extraordinary people, advocating for landscape-scale change, and educating a new generation of practitioners in the art of working with water.

Water Stories is following a similar path. It is a learning, training, and action platform focused entirely on water cycle restoration, offering a community-centered approach to some of the most pressing environmental crises we face: drought, flood, fire, and polluted water. Its award-winning films tell the stories of people who have raised their communities out of extreme environmental crises, and are available free to its online community. That community now numbers over 3,000 people from around the world, concerned about the future of fresh water, learning from one another across different landscapes and contexts, and supporting each other toward a better common future. Founded by Zach Weiss, Water Stories was created with a bold vision: to train a global force of water cycle restoration practitioners, equipped to heal landscapes wherever they are needed.

Zach Weiss spent years learning to restore the water cycle from the ground up, studying under mentors including the legendary Austrian farmer Sepp Holzer, who urged him to take what he had learned and teach it to as many people as possible. That call to multiply the work is what drives Water Stories today.

The methods Zach developed are focused on helping the land receive rainfall more effectively, slowing water down, guiding it into the ground, and recharging aquifers so they can feed springs and streams throughout the dry season. They are rooted in reading the landscape, observing where water flows, how slopes behave, where it pools or rushes away, and then working with those patterns rather than against them. In practice this means building terraces, planting strategically, putting in check dams, and creating water retention features that follow the land’s natural contours (in title picture above, are terraces leading into a water retention pond, that helps recharge groundwater, that Zach helped create in Montana USA). It is about restoring soil, restoring vegetation, and restoring the slow, generous movement of water through living landscapes.

Farmers using these methods have withstood wildfires while neighboring properties burned, because their land was deeply hydrated going into summer. Others have seen vegetation flourish as rising groundwater reaches plant roots. The core idea is simple but profound: get the earth to receive water better, and life follows.

Now, rather than doing that work alone, Zach is focused on training others to do it too, spreading these skills as widely and as fast as possible across the world.

A groundswell takes hold when networks begin to form, when decentralized centers of activity emerge around the world, when people step into leadership, and when knowledge spreads person to person. Permaculture did exactly this through its Permacultue Design Courses, which perhaps half a million people have now completed, with many millions more practicing its principles worldwide. It spread like an octopus reaching into every nook and cranny of the globe, quietly shifting paradigms and transforming both landscapes and lives.

The groundswell that Water Stories is one of the forces helping to build is beginning to feel like that.

Yoga offers another useful parallel. It took off in the 1980s when enough teachers had been trained to make a living from their practice, creating a self-sustaining wave of growth. That is exactly what the Water Stories platform makes possible, a genuine career path in watershed restoration. Practitioners already report having more projects than they can handle, more land asking for attention than there are trained hands to tend it.

Across the world, a broader awakening around water is underway. Scientists, farmers, indigenous communities, and restoration practitioners are all converging on the same understanding: that healing the water cycle is one of the most powerful things we can do for the planet. Water Stories sits right at the heart of that, with the tools, the community, and the vision to become one of its many central forces carrying that groundswell forward.

Here is a lightly edited, abridged version of of our interview:

Alpha: Cool, I’m excited to have on here again. You came on two years ago….. Maybe you could just start out by saying a little bit about the larger global water problem, and then how you came upon this path of actually trying to help the whole water situation in the world.

Zach: When we look globally, I think the easiest, most succinct way to look at the challenges we’re facing is that right now, we’ve built landscapes that reject the rain, and what we’re seeking to do is help those landscapes receive the rain. The greater picture is of water cycle restoration, of rebalancing the full cycling of water through living ecosystems, of water retaining on the lands, of being circulated in the small water cycle, of being circulated slowly through the larger water cycle. But in daily practice, it really is just helping landscapes receive the rain instead of reject them.

There’s just so much need for this around the world, there’s so much interest and demand for this work, way more than I could ever service on my own, and so we really started looking at — and Sepp Holzer pushed me towards doing this — how do we give capacity to people to do this work all around the world? I took my 5-year journey to getting where I am, and tried to condense it into 6 months, and we basically give people all of the essentials with none of the unnecessary stuff, so that by the end of that, they’re further along in activating these changes in their community. And it’s different for different types of people, you know, it’s really not a course where it’s like, come in and you’re gonna leave being an earth mover. That might be one route that you take, and that’s a route that we need lots of, but we need advocates, we need stewards, we need all these different people helping out in all of these different roles to make the changes that we’re really trying to make globally, around the world. And so we really try and just help people in that journey.

The way I look at it is it’s one thing to get a map and say, okay, I can kind of figure out where I’m going here. It’s another to get a map and then have someone grab your hand and drag you along the trail, and teach you how to orient, and teach you how to read the map. And then you’ve already started that journey by the time something like the course is finished. And it’s just amazing — we just had a webinar earlier today, and within one year, people are making real changes in their communities. They’re becoming an expert in the field in their communities, because they’re actually practicing and engaging with it every day, and have this really great community of support to lean on and learn from one another as well.

Alpha: One of your central teachings is this idea of the Watershed Death Spiral, and then also how we can restore it via the Revived Water Cycle. For instance, all the wildfires around the world are, in part, tied to this problem with hydration. Could you say a little bit about the wildfires, and also this idea of Revived Water Cycles and the Watershed Death Spiral?

Zach: Yeah, definitely. I oftentimes joke that Australia and California are in this race to the bottom of the Watershed Death Spiral. Those two places are getting so severe, the fires are getting so crazy, and it frustrates me to no end that people aren’t even addressing the root problem of the issue.

When everything’s drying out, all of the organic matter is oxidizing and turning into fuel for fire, rather than being broken down by life and becoming food for fungi. And so you very quickly get to this pattern of drought, fire, flood, drought, fire, flood — and they each beget each other. This is where we see just a huge potential to change things. The number of projects I’ve seen where drought’s no longer an issue, and flood’s no longer an issue, and they’re fire resilient — within a couple of years to a decade at most — it really just shows how clearly we have the solutions; we’re just not implementing them.

You see places that have really revived the water cycle over huge areas. We were recently in India where rivers are flowing now, it’s cooler in the summer, the rains are coming, and the communities are back on the landscape. It’s just like, wow, why aren’t we doing this? This is so simple, the benefits are so extreme. And so this is really where we’re trying to lead people: how do we restore some kind of balance to our water household, so that water is slowly moving through the ecosystem again and again? And people are able to do it all over the world. This is one of the great things — it’s not something we need to wait for governments to act logically on, or for big businesses to develop some conscience. People on the ground, living on those landscapes, can do it today and see the results after the next rains.

Alpha: Could say a little bit more about the drought-fire-flood cycle. Why exactly does fire lead to more floods, and why do floods lead to more droughts?

Zach: So after a fire — and the temperature of the fire becomes really important too — the type of char that’s created actually changes. When it gets really hot, that char can become hydrophobic, actually repelling water. So in the extreme case, when a landscape burns very hot and the rains come, it’s rejecting the water both because it lost all its organic matter and because that organic matter has been turned into something that repels water. And even if you’re not getting that effect, all of the channels that water used to move through and be absorbed by are now broken. So you get all that water moving downstream more quickly than before, creating floods downstream, but because the water didn’t infiltrate, you’re also creating drought on that landscape.

And the long-term drought leads back to fire. We’ve generally destroyed all the water-holding capacity of the landscape, then hardened it, plowed it, created hard surfaces that send water downstream, cut roads across it, dredged the waterways. We’ve done all these things to speed up water moving downhill, which creates floods downstream. But because that water is moving fast through the system instead of slowly, it creates persistent drought, which leads to fire. For example, woody matter that doesn’t have basic hydration to break down into the soil just petrifies and forms a nice fuel bundle. So you get all these effects acting collectively in the same direction.

Alpha: You’re saying there’s this Revived Water Cycle, where certain intervention points help build the land’s capacity to hold water, rebuild the soil, and rebuild vegetation. And I think to some people it might not be obvious that making certain indentations in the earth. these earthworks, can actually do a big part in restoring this important cycle that could affect the whole global water cycle and climate.

Zach: Yeah, it’s so simple. When you intervene in the right places and do the right things, you start this never-ending cycle, this perpetual motion machine that is nature. If you help slow down water, it creates more life, and that life creates more water, and it feeds into this smooth, steady cycling. There’s a really nice saying we picked up in India: where water runs, help it to walk. Where it walks, help it to crawl. And where it crawls, give it rest and allow it to enter into the womb of the earth.

This is actually the recharge of the groundwater that then supplies so much of the downstream landscape. This is another neglected mega-crisis of our times — the overextraction of groundwater, mostly without monitoring. We all know what happens to a bank account if we just take out and never put anything back in: we go broke, and it gets ugly very quickly. That’s currently happening with groundwater in a lot of our planet. So by helping water slow down and go into the landscape where it’s concentrating and moving quickly, we’re also helping reverse groundwater depletion — actually charging up those groundwater sources. The big thing is just reading the landscape and making the right interventions at the right points, because the earth has a tremendous capacity to hold water. We want to hold water not in our built infrastructure, but in the earth’s womb, where it has an incredible ability to do so.

Alpha: Do you want to say a little bit about some specifics of how you intervene? I know you did some work in Spain with the dehesas — to get agriculture going again in those degraded landscapes, your first step was restoring the water, right?

Zach: Yeah, for me it always starts with water, though it’s water as part of a whole. Water, soil, vegetation — they’re all part of the same system. But looking at how a landscape is managing water is really the first step. What we were just talking about made me think of some students of ours in Chile. They had a really tough landscape almost all silt with almost no clay — and we were thinking, you’ve got a really tough go of it down there, but apply these same principles. They built crater gardens and retention ponds and retention features on their landscape, and they already have a spring that’s formed from the work they’ve done.

By digging these little holes that collect water from the road and send it into the ground instead of downstream, they’re charging up the ground, making greenery, and even creating new water downstream as a result of that process. And the great part is you dig the water body once, and if you do it right, every time it rains after that it’s doing work. And even between the rains, it’s doing work — that’s why it’s so effective. It’s like a one-time investment for an era of nature doing its own work from that point forward. Th retention ponds are maybe a couple hundred square feet, with the biggest one around a thousand square feet or so. They really don’t need to be large; they need to be at the right points within the land, where they interact with the natural skin of the earth.

Alpha: And just a couple of these help recharge the groundwater, which then affects the hydrological cycle?

Zach: Yep, exactly. And the wonderful part is that water is also grabbing clay higher on the landscape and depositing it into their system, so they’re actually harvesting that process to improve their system over time with the clay the water is delivering.

Alpha: Can you give some examples of what happens when the water table does rise? What are some examples you’ve seen in different places?

Zach: Yeah, I think the most striking example I’ve seen was in India, where we recently visited. Rivers are flowing now because the groundwater has risen. In this area, 9 rivers are now flowing throughout the year as a result of groundwater recharge. 250,000 wells that were dry now have water again. But perhaps the most striking thing: in one of these areas, 6,000 violent bandits handed over their weapons and became peaceful farmers, because they have water again. When you talk about the impacts of recharging groundwater, it touches the waterways, the agriculture, the ecology, and even the way of life for people on that landscape. This was in Shambhal, in Rajasthan, in northwestern India — a very dry region. That’s where a lot of their projects are concentrated, though they’ve also done work in other parts of India.

Alpha: I know that Sepp told you that you were doing great work on your own with all this water retention, but what you really needed was thousands of people doing it. And so that caused you to think about starting a school to train more people. Since I last talked to you, that school has probably grown quite a bit.

Zach: Good mentors always push you to the next step. Sepp said probably the nicest thing he’s ever said to me, calling me his best student — but immediately followed it with, “but one of you is nothing! We need hundreds or thousands!” Really good mentors will just keep pushing you forward, and that led us to create Water Stories. We’ve now had around 400 students go through our training over the last couple of years, and it’s just incredible to see all of the changes they’re making around the world. It’s already dwarfed what I could ever hope to do within my lifetime, and we’re just at the beginning.

Because for each one of these people, what they’re accomplishing within one year is just the start of a career path that’s going to span the next decade or two for many of them. Imagine the change they’re going to create over such a long period of time. It really gives you a lot of hope — wow, we really can do this. People really are good; they do want to do good things when they’re given the opportunity. That’s what they execute upon, and that’s why we built the course in a very strategic manner.

We designed a course that is online, but it’s really at home in the sense that you need to go out onto the landscape and actually do all of these things. And if you do them, it will lead you to the next step. For example, we ask people to give a presentation in their community about water cycle restoration. That’s not primarily for the sake of spreading water cycle restoration — though that’s a nice byproduct — it’s because if they do that, that’s where their first client is going to come from: someone in the audience of that presentation. And then it leads to the network and the growth that people actually need to build a career around this. I think that’s why our program has been so successful: we give students a roadmap, all the steps needed to become a practitioner, and a community of hundreds of other people willing and able to support them on that journey. It makes it a lot easier. It’s one thing for visionary mavericks like Sepp Holzer or Rajendra Singh to accomplish all this, but for an average person like me or you, it’s a lot easier with some support, some people to help along the way, and some experienced mentors to draw upon — and that’s what we’ve set up our program to provide.

Alpha: Cool. I was wondering if we could talk a little bit and tell the stories of a couple of your students. Maybe we could start with Nick Steiner, who I also know and who’s also come on this podcast. He was one of your earliest students.

Zach: Yep, so Nick was in our first class, which I think was back in 2022 — the first time we ever ran the program — and a lot of incredible students came out of that, Nick being one of them. He went from being interested in these things and having quite a good skill set, but not having it be a full-time job, or a way of life, or a vocation, or a real cohesive business that earns his livelihood, to having a full-time water job.

And for me, this was a very important part of the course. A lot of trainings teach you one little skill set and then ignore everything around that skill set that’s important to actually delivering it. So, for example, how do you manage clients? How do you set up your contracts? Do you hire people or not? How do you do estimates? We give the framework in the course for how I do all of those things, so that people can really easily move on to doing that themselves.

And now Nick’s doing it full-time. He’s passing projects off to our other students because he has so many. It’s just really incredible to see that switch happen within a year, where it goes from something I’m interested in to something I’m working in full-time. And he’s doing really great projects for all sorts of farmers throughout Europe. He’s currently on an earth-moving project somewhere in Spain

[Nick Steiner building a water body].

Alpha: I know he does it with so much joy, too. What does he do on these farms?

Zach: Yeah, the approach that we teach first looks at how do you understand the landscape — what’s on it, what features it has, what capacity it has. Then how do you understand the goals of the people there: what they’re trying to create, both their long-term goals and their immediate pressing challenges. And then how do you harmonize those two elements? In Spain and Portugal, water scarcity is a real limiting factor for most agriculture in the region. And yet, when the rains do come, all of that water just flows downstream away, where it can’t benefit that farmer or that landscape. So a lot of it is: where do we find the intervention points where we can do a relatively small amount of earthmoving? Now, sometimes it might be a big earthmoving project, but we want the maximum hydration outcome per amount of earth moved. For example, today he’s building a water body in an area where they found clay and some underground seams of water. He’s on the excavator, opening up the key, compacting it very diligently, creating a vessel within the earth that will receive the waters when they come and allow them to enter the ground, recharge, and rehydrate that space. Basically, they have this dying landscape that they’re trying to put back on life support and get going in the right direction.

Alpha: So the idea is that when you build these retention ponds, or features that capture rainwater, they recharge the groundwater, and then vegetation can reach that groundwater, and that’s why the land becomes more alive. Is that the basic principle?

Zach: Yeah, and it varies depending on the geology. In some areas, you might make a water body that specifically rehydrates a deeper aquifer, or a spring, or a waterway downstream. In some areas, you might make a water body that holds water all the way through the year, creating surface tension that wicks moisture out all around it and produces this beautiful green, hydrated zone. You might also use that water for irrigation on certain crops. So there’s a kind of spectrum between a very ephemeral water body that recharges the ground and a perennial water body that supplies surface water — from the water itself to the habitat — with a lot of things in between. The specifics of the landscape tell you what’s possible, and the goals of the people tell you whether it makes financial sense and is viable. Together, those things make it pretty clear what kind of project to move forward with.

Alpha: Other students you want to mention?

Zach: Yeah, one of my favorite students is from Japan. He’s been doing amazing work. They’re actually just starting a course tomorrow for Japanese speakers on food forestry and water cycle restoration. And they have a whole project now designed around the question: how do we lower the temperature of our city by a degree and a half through water cycle restoration? He’s also using it as a way to connect with the indigenous cultural heritage around water in Japan, which is very strong and very vibrant. Basically every culture in the world, if you go back far enough, has a deep reverence for water.

They’ve been doing all sorts of really cool projects. One of my favorites: he started a food forest for a man who had been diagnosed with cancer and wasn’t expected to live very long. This man wanted to leave something for his children and grandchildren, so he started the project with Jun Omura, the student. And then he started enjoying it so much — it was going really well — and he just kept getting more and more full of life. He’s now far outlived his expected life expectancy. He created this garden to die in, but it’s actually become a garden to live in, giving him so much energy, and it will provide for his kids and grandkids. That was just a really special story — knowing that people are making such a big impact on people’s day-to-day lives. And then it begets itself, because that client tells his friends, and before you know it, Jun has this roadmap of projects and needs help because there are too many for just him. That’s the really powerful thing about this kind of work.

Alpha: Cool. And what are some of the strategies he had to lower the city temperature? What are some of the projects?

Zach: Yeah, basically making green spaces again, getting water staying in a living earth and circulating through vegetation. In their context, that means making green pockets to break up the heat island. They’re in a very industrial city, so the strategy is: how do we start to break up the concrete mass and add a bunch of cooling pockets? You know, a liter of water moving through a tree absorbs about as much energy in the form of latent heat as a regular car battery holds — about two-thirds of a kilowatt hour. So the more water you have moving through vegetation, the more localized and regionalized cooling you’re providing, breaking up those heat islands. They’ll actually be presenting on this next week on the 24th in a webinar we’re hosting — their whole strategy for how to lower the temperature a degree and a half in their city.

Alpha: It is quite amazing, because every student you have creates all these ripple effects — just like when Sepp had you. So 400 people doing projects all around the world is remarkable. You have some students in Africa too?

Zach: Yeah, we have a handful of students in Africa. One that comes to mind is Gonzalo, who’s been doing projects there. He was an architect who didn’t like being in such a corporate, sterile setting, wanted to find his way back to nature, came and volunteered on a project, and has since been working in South Africa on his own project and on projects for clients, building water bodies. And another student of ours, Stenbergen, in Kenya, is actually starting a project with a university — still in planning phases, but on university grounds as an education resource for people at Nairobi University. Natalie Topa is doing all sorts of amazing work throughout Africa. In many ways, I think Africa and South America are the best places to potentially lead the way here, in that they have a more direct relationship with the land and a real desire to do a little bit of work to improve their own quality of life.

To give you a sense of this: we did one training in a very remote village in Mozambique. We trained 15 people — we called them water MVPs — and built one water body together. The next day, people in the community were already using that water to water their gardens, do their laundry, and meet their daily needs. But then we left, and with the help of 50 villagers, they built 26 water bodies in the two weeks that followed. So from a 5-day training with the local people, they went on to create all these little water bodies all around their village — a place where they have huge water scarcity issues in the summer and real challenges growing enough food, especially with animals coming through from the nature reserve. To have that kind of impact on people’s way of life in just a few days — there aren’t too many things where you can really do that.

Alpha: Other students you want to mention?

Zach: In Australia, Claire Vanderplank comes to mind. She had a big event there, and she started the Western Australia Water Alliance. She’s been doing water projects for clients and friends, but is also very focused on advocacy, because the reality is that so many people who need to know what’s possible have no idea, and so many policymakers who need to make different decisions have no idea either. This goes back to the point that we need storytellers, authors, artists, musicians — it’s not just about getting in the machines and digging the holes. That’s a critically important piece; without it, there’s nothing. But we need all these other layers around it to create real change. Claire is doing a really good job activating local communities and building community support that will make it easier and easier for her and others in the area to do projects year after year — more interest from clients, more support from regulatory bodies.

.Alpha: And Claire was the person who felt the river was asking her — “how come you don’t drink me?”

Zach: Yeah, exactly. That’s a big part of developing a relationship with place: spending the time to let your monkey mind go quiet and receive information. She mentioned sitting next to a water body and it asking her, why don’t you drink me? And that’s a great question, because water used to be drinkable everywhere. There are entire watersheds now where it’s not even swimmable or fishable anymore, and that is shocking. That is a bad state of affairs.

So this idea of being a voice for the voiceless is really important. You know, imagine the earthworm in the soil — it has no voice to say, hey, stop spraying chemicals on me, but it still suffers from them, and it has no doctor to go to for relief. So how do we each, as humans, start to be that voice? Whether it’s for the river, the forest, the earthworm, or the fish.

Alpha: You provide support for your students to actually host workshops, right?

Zach: Exactly, and I can’t tell you how many times we’ve heard from students: they say, well, I put together the presentation, and only 3 people showed up. But I figured I’d just give them my full attention, and they really loved it. And then they put on the next event, and it’s 12 people. And then the next one, it’s 20 people! Because this is something that just has so much potential, it’s so exciting, that it just grows and grows. There’s so much opportunity. And so, yeah, that’s exactly it — how do we make this groundswell of community activation happen?

We’re trying to build community, foster networks. In a very practical sense, we’ve had a lot of situations where students from the course end up starting businesses or efforts together with other students, because they can each contribute where they have skills and capacity, and lean on others where they’re more deficient. And it’s just a lot more fun and enjoyable for everyone to push that boulder uphill together, rather than each person trying to push their own boulder alone.

Alpha: And in your education platform, you have some different tracks, too, right? One for people who really want to work the land and help clients, one for people who want to work their own land, and one for advocates working on policy. And I know you have someone in Oregon who’s pushing some policy around water?

Zach: Yeah, absolutely. Actually, a group of several students banded together and formed PLUG Oregon — Permaculture Land Users Group Oregon. Last I talked to them, they were getting very close to pushing through some exemptions that would allow farmers to create water retention features and hold rainwater. Because the reality is water law in the western US is so broken — it’s just a total mess — and it actually makes it very difficult for people to do meaningful projects. And so this group of students said, let’s fix this in our state.

And the reality is, when you speak with confidence, clarity, and a pure heart, people listen. So, yeah, we have these three different archetypes. The person who wants to do it professionally and earn their livelihood doing this. The steward who wants to do it on their own place. And the advocate who’s going to share this with the world. They all have a really important role. We have a lot of retirement-age people do our course through the advocate track, and they’re the ones who, in many ways, create the opportunities for young professionals.

Alpha: And over the last two and a half years since I last talked to you, how would you say this whole water movement has been evolving?

Zach: You know, it’s been really interesting to see it start to get a lot more mainstream traction than I ever would have imagined. Since we last spoke, I’ve worked on a job for the Department of Defense. The Water Conference had a whole segment on the power of green water for climate stability. The Global Commission for the Economics of Water has released a series of reports. A European Union Commission released reports saying, basically, we need to do decentralized water retention all throughout Europe to solve these challenges. So it’s definitely starting to get a lot more mainstream attention.

But the big thing I keep coming back to is: give all of my time and energy to the people who are the future practitioners. They do so much in one year’s time, and they give so much inspiration to each other and help support each other. When we have events, it’s like this little village forms of the best people in the world — these amazing little experiences. So I’ve really come to see: these are the people who are going to do it, and I should do everything in my power to support them, get them off and running, and be there for them over the years as they need it. The webinar we just did today — I left so inspired. It’s crazy, because I started all of this about 4 years ago, and now I look at it and think, wow, these people are so inspiring. How are they doing so much so quickly?

It’s like we’re all part of this superorganism, each getting to push in a little bit and contribute what we have. And it honestly restores a lot of my faith in humanity. I often tell people, I live in this tiny little bubble, and in my bubble, everyone wants to help, everyone is an altruistic person — and I love my tiny little bubble. I want to stay in it. And this bubble is just slowly growing. When people enter it, they’re like, oh, it’s really nice in here, this is really fun, everyone’s really supportive — and that just helps it grow a little bit at a time.

Alpha: Cool. Yeah, it sounds like getting in on the ground floor of a whole movement. Do you want to say a bit about your upcoming course — when it is, how long it runs, and how people can sign up?

Zach: Yeah, so we have a live and a self-paced version. It’s the same basic content, but the live version is a cohort of students from around the world, with live sessions with me and a whole bunch of extras if you’re able to participate in real time. People like both versions, but they say it’s well worth it to do the live — the live sessions alone are worth it. Registration is open now through March 27th, and then the program starts and runs for 6 months as we go through all the content together. But it really is also a long-term thing. After the 6 months, it moves into an alumni membership, which people are welcome to join. We have people still meeting each month who started with us at the very beginning, years ago, and you can come and go as you like.

And that’s the other big thing I’ve found: for some people, 6 months and they’re off and running — great. For others, that journey might take a year or two, or even five years. So how do we build a community of support so that all these different journeys can reach their destination? So it’s a 6-month program, then open-ended. There are sessions and new videos every week, and it’s all set up so everything is asynchronous except for the live sessions. It’s not a case of joining a call and sitting through a lecture you could have watched as a recording. It’s all built around watching the produced content beforehand, and then getting together to discuss it — so we can really dive deep into each topic and each module together. It opens once a year in the spring, runs through the end of September or October, and then the self-paced option is available anytime.

Alpha: Cool. And this is the Water Stories course. How people can find it?

Zach: WaterStories.com. The Water Stories Core Course is what we call the program. And for people who aren’t sure yet, we have a lot of free content — films, animations. If you’re not ready to jump in, we say spend a year just digesting all of it so you can really get the maximum out of the program when you do. A lot of people spend years learning from the free content, and then when they’re really ready to make that big leap, they enter the program. We just released a new film last week and will be releasing another one next week, because we really just want to get this information out there. So check out the stories section of WaterStories.com. We also have a Mighty Network community, a great place to meet other people and learn from one another. There are a lot of next steps you can take even if you’re not ready to jump into the course.

Alpha: And what’s the time commitment for the course?

Zach: It depends how much you want out of it, but I tell people to expect 5 to 10 hours per week if you want to become a professional by the end of 6 months. Some people may even want more. It’s basically 2 hours of content, 2 hours of live sessions, and then 2 to 6 hours of outdoor activities, because the course really is what you make of it. We lead you toward all the actions, but if you don’t do them, you’re going to learn half as much. So it’s definitely worth making sure you have enough time when you sign on.

Alpha: Okay, cool. Thanks, that sounds great. Well, it’s been great having you on, and I’m excited to be part of this water movement with you. Any concluding words?

Zach: I’m just excited for your forthcoming book — I can’t wait to read it.

I think the biggest thing I’d say is: just get out there and do it. Sepp Holzer always told me, do something and something happens. Go outside in the rain. The water will teach you everything you need to know — where to intervene, where not to intervene, all of it. Just get out there and start reading from the Book of Nature, and you’ll be really surprised what it tells you.

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The Water Stories course begins this Friday Mar 27th, 2026 if you are interested in signing up. https://www.waterstories.com/core-course. If you enter the code ‘CLIMATEWATERPROJECT’ you can get $100 off the course.

Course Intro video

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The idea of bringing back the beaver to the UK was an idea that was scoffed as too eccentric, even by environmentalists. But Derek Gow, against a lot of opposition, has pioneered bringing the beaver back, so that they are now once again part of the UK landscape, restoring the wetlands and rivers.

Born in Dundee in 1965, Gow left school at seventeen and spent his early years in agriculture. He was inspired by the writing of Gerald Durrell, and jumped at the chance to manage a European wildlife park in central Scotland before moving on to develop two nature centres in England. That early immersion in wildlife conservation set him on a path that would eventually make him, in the words of George Monbiot the person who has done more to restore Britain's missing fauna than anyone else in the country (words written in the blurb for Gow’s memoir).

Gow was the first to import and quarantine beavers for projects in the UK, sourcing animals from Poland, Bavaria, and Norway. It was the opening salvo in what would become a long and often maddening battle against institutional resistance. Since the early 1990s, in the face of outright opposition from government, landowning elites, and even some conservation professionals, Gow imported, quarantined, and assisted the reestablishment of beavers in waterways across England and Scotland, while responding to the opposition with characteristic bluntness, charm, and what his supporters describe as an almost reckless willingness to keep pushing when anyone else would have given up.

Beavers were once common throughout England, Wales, and Scotland but became extinct in the sixteenth century, hunted for their fur, meat, and castoreum - a secretion used in perfumes, food, and medicine. Their disappearance was the removal of a keystone engineer from the landscape. Beaver dams create wetlands, slow water flows, filter pollutants, and provide habitat for an extraordinary range of species. Through gnawing on stems and coppicing trees, beavers stimulate regrowth that provides homes for more insects and birds, while also enabling more constant water flows and better water retention during droughts.

In 2015, several families of beavers were reintroduced in Devon, in the UK, as part of the River Otter Beaver Trial - the first legally sanctioned reintroduction of an extinct native mammal in the country. Over the following five years, the two original breeding pairs expanded to at least eight, and researchers found 28 dams built across the catchment, impounding water across nearly two kilometres of watercourse. Findings from the trial showed that beavers reduced flood flows by up to 60%, even during very wet weather, by holding back water in newly created wetlands and allowing it to trickle out slowly rather than surge downstream. In the flood-prone village of East Budleigh, a family of beavers constructed six dams upstream, with the measurable result that peak flood flows through the village were significantly reduced. The animals were also found to clean water supplies, removing large quantities of soil, manure, slurry, and fertilisers from rivers and streams.

Beavers have been steadily increasing their numbers over the years. There are now over 2000 in Scotland, and around 500 in England. Wildlife trusts are looking to release more this year.

Today, Gow farms a 300-acre property on the Devon-Cornwall border that he is transforming into a rewilding haven, while continuing to be influential in the reintroduction of the Eurasian beaver, the water vole, and the white stork in England. He has written about the whole extraordinary saga in his book Bringing Back the Beaver.

Here is an edited, abridged section of our interview

Alpha: This whole field of water restoration and rewilding - how did you get into it?

Derek: I started working with water voles which are a very small animal in Britain. Water voles are one of the characters in Kenneth Graham’s book The Wind in the Willows. The character of Ratty, sculling up and down the idyllic English River with his friends, used to represent a very common animal. They were incredibly common in British waterways from the beginning of the twentieth century, and writers at the time referred to their overwhelming presence.

Around 100 years ago water voles prospered. But by the 1960s and 70s, canalization of rivers, concrete banks, pollution, and the introduction of North American mink from fur farms caused massive declines. The animals once lived in chains of colonies along waterways. When those chains break and populations fragment, they can’t find unrelated mates and they disappear.

Today the species has lost around 97% of its British range. The remarkable thing is that they are extremely robust. If you reintroduce them correctly with the right gene base and numbers, they recover easily. Their decline shows how harshly we’ve treated the Earth.

I began working on water vole reintroductions about thirty years ago. We’ve learned a lot, though we haven’t saved them entirely. Early in that work, digging ponds and cutting trees to create wetlands, we began to realize something else must once have been doing this before us. And somebody eventually asked: do you understand what beavers do? At the time, I really didn’t.

So in the early 1990s I went to Poland and spent a month visiting wetlands where beavers had been reintroduced in the 1960s. Wading through these incredible ponds with floating islands of vegetation, orchids flowering, frogs jumping away, dragonflies landing on your head—you reach the great beaver lodges in the middle of this living world.

You quickly realize the animal that created habitat for water voles and many other species is the beaver. People call them a keystone species, but beavers are bigger than that. They are a function of nature itself. Apart from humans and elephants, they may be the third most impactful species on the planet in terms of habitat creation. That was my first journey into understanding beavers.

Alpha: So you were a farmer when you started introducing the voles?

Derek: Yes, on and off. I was also working on conservation projects. And water voles and beavers became central to those.

When I started talking about bringing beavers back to Britain in the mid-1990s, people laughed. Most conservationists thought it was ridiculous.

Yet when I traveled to Poland, Germany, Russia, and the United States where beavers had been reintroduced, I realized it was perfectly feasible. Much of Britain still has the trees beavers need. The problem wasn’t ecology—it was misunderstanding and inertia. Historically beavers were heavily hunted for fur and for a substance called castoreum in their scent glands, which contains salicylic acid, related to pain relief compounds. Because of hunting, their populations collapsed. By the early twentieth century only about two thousand remained in Eurasia. Governments eventually protected them, and slowly populations began recovering.

Alpha: And there are two species of beavers, right? The North American and the European?

Derek: Yes. When Europeans arrived in North America there may have been about 100 million beavers. The fur trade reduced them to around 2.5 million. In Eurasia the collapse happened over a longer period but was just as catastrophic.

Ecologists studying North America have been able to track the environmental impact of removing beavers. Rivers eroded, floods increased, soils washed away, chemicals flowed into waterways, and ecosystems collapsed. Our pursuit of beavers was ruthless.

Yet ancient cultures understood their importance. Leaders of the Zoroastrian religion in Iran over two thousand years ago forbade killing the “water dogs,” warning that deserts would advance if they were destroyed.

Alpha: Wow. They figured that out that long ago?

Derek: Yes. But modern societies largely forgot.

Alpha: So when beavers build dams, how does that affect rivers and floodplains?

Derek: Beavers are lazy animals. When they first arrive in a landscape with wetlands, they live easily—floating around eating reeds and plants. But they are territorial. As populations grow, younger animals move upstream into smaller creeks where they build dams.

These dams create wetlands that act like giant sponges. During heavy rainfall the wetlands absorb water and slow its movement. Water can take ten times longer to pass through the system than it otherwise would. That breaks flood peaks for communities downstream.

A great example is the Bridge Creek project on the John Day River in Oregon. Conservationists built structures to help beavers rebuild dams. The beavers reinforced them, slowing water flow and reducing flood damage dramatically. Beavers can have enormous effects, but only if we allow them enough space.

Alpha: So many rivers today are straightened and engineered, but naturally they would be braided and slow-moving?

Derek: Exactly. Nature never produced anything that flows in a straight line. Humans did that. For centuries we drained wetlands, built pumps, and tried to enslave water. Now climate change brings heavier rainfall and the water pushes back into places where we built our towns. We call that a disaster. But really it’s nature reclaiming what was always hers. The sooner we reshape landscapes to work with water again, the sooner we’ll realize the beaver may be one of our best allies.

Alpha: So how is the rewilding effort going in the UK and Europe?

Derek: So the rewilding movement in the UK… There’s a huge amount of talk about rewilding. The most famous rewilding project in the UK is a place called Knepp Castle in Sussex, and that is the home of a couple called Charlie Burrell and Izzy Tree. They have effectively rewilded their estate over the last quarter century for nature, and the results of what they’ve done, the cessation of farming, the use of big old breeds of domestic animals as proxies for extinct animals, has just been remarkable.

The response of all the other wild species that live there is incredible. Bird numbers have risen with much greater diversity and abundance, and it really shows that if you approach even meat production in a different way — lower densities of animals, feeding them no extra supplements — you can create a landscape that is very rich in other life while still keeping some cattle.

Elsewhere in Britain you’ve got other people talking about rewilding. There are all sorts of shapes and forms that it takes, from managed landscapes with very low densities of domestic animals to places where perhaps some wild ungulates are present — though there are very few of those left in Britain. Maybe a few wild boar and a few red deer.

Different organizations and individuals are doing this for different reasons, so it is slowly growing in Britain as a way of approaching land use. But our government is incredibly hesitant about it, and our nature conservation authorities can be very difficult when it comes to moving this process forward quickly.

To be brutally frank, things like the beavers, the reintroduction of the beaver , has been a thirty-year battle with all sorts of obstacles. The nature conservation organizations really did not help much at all until about the last five years. Even now, when it comes to government organizations, the bureaucracy involved with removing a few beavers into a new river system — it would be easier to move nuclear missiles and point them at the Irish than it would be to move the beavers.

Europe is much more advanced. There’s been a huge degree of liberal thinking and action there, again for possibly about thirty years. One of the best parts of Europe to visit if you want to look at initial rewilding is the Netherlands. There have been large projects like the Oostvaardersplassen above Amsterdam where they’ve taken six thousand hectares of what was going to be industrial land reclaimed from the bed of the North Sea and allowed wild herds of large herbivores to live there and regulate themselves. This allowed the plant landscapes to develop and drew much other wildlife to it.

Now all the way through Europe you see different projects of different sorts, with different species and habitats forming, and it is incredibly encouraging.

When you look at responses to wolf reintroduction — for example in places like Yellowstone and Colorado in the United States — and then compare it with the Netherlands, which people imagine as windmills and tulips, the wolves are right the way through that landscape now. They are in people’s back gardens eating pygmy goats. People encounter them on walks while Nordic walking or walking their dogs.

In the main everybody regards their presence quite rationally. A few weeks ago a wolf attacked and bit a child and it was shot, but nobody is jumping up and down about it or making a huge fuss that the wolf is back.

If you look at that over time, we do evolve as a species in our relationship with nature. If wolves had returned to the Netherlands fifty years ago the main response would have been to kill them all. Now the vast majority of people are prepared to tolerate them.

Alpha: Do you want to say a bit about your efforts to reintroduce the beaver — where you introduce them and what you had to fight through?

Derek: My efforts to reintroduce the beaver… well, now we’re reintroducing them into habitats that are suitable. In the last few weeks the first licenses have come through to put more beavers out in England, and to reach the point where we had that official permission has taken nearly a quarter of a century.

When the beavers first came, I imported them for areas where landowners were putting up large fences and keeping them in enclosed areas. But sooner or later beavers — which are basically made by God with bolt cutters on their faces — got through the fences and out into the surrounding wetlands and simply started living there.

So there have been illegal colonies of beavers living free in England without licenses for maybe twenty years or more.

My role was importing these animals and giving them to people. Nobody broke the law initially; some of the beavers simply escaped.

Now we hold beavers for projects that are going to release them into wetlands. We have big buildings on the farm designed for this. Beaver families come here and stay for a couple of weeks where we feed and look after them before they move on to their final destination. It’s like a beaver hotel.

Initially there was a lot of advocacy — film work, media, talking to organizations about beavers. I don’t do much of that anymore. I think no human being can do that for their entire life and remain balanced. You have to move on to other interests.

My interests now are restoring other species that depend on beavers, such as water voles, or species that benefit from beaver wetlands like white storks. Because not many people are working on those creatures, that’s where I focus now.

The whole thing has changed greatly from being a lonely guerrilla war to something where many organizations and individuals are involved with restoring beavers.

I have beavers living free on my farm, and in the summer evenings my greatest pleasure is to get a bottle of cider, sit outside with binoculars, and watch them doing whatever they’re doing and watch all the other life that revolves around them.

I don’t want to fill in any more forms on their behalf or fight any more political battles. Those days are done.

Alpha: Thank you so much for getting the whole movement going. Do you want to say a bit about the white storks and what you’re doing with them?

Derek: When the beaver disappeared and we destroyed the wetlands, we also destroyed everything that lived in them — fish, waterfowl, cranes, white storks, black storks, bitterns, everything.

White storks were once recorded nesting in Britain in the 1400s and again after the Second World War. From the time of the ancient Greeks and Aesop they were seen as symbols of joy, recovery, hope, and rebirth.

But in Britain when they sat on the roofs of people’s houses we simply thought: there’s lunch. So we killed them.

As the species recovered in Europe they sometimes passed over Britain, but they would not breed here because birds have to be born somewhere to think of it as home. If no young storks are born in Britain, none will return here to nest.

So our project began with a feasibility study in 2017. With funding from Knepp Estate we imported orphaned storks from a wildlife hospital in Warsaw Zoo.

Some could fly and some could not. The ones that could fly eventually left, but over time birds in the enclosures and the free-flying birds started breeding.

They built nests high in oak trees around Knepp. Last year there were around forty-seven nests and the numbers grow every year. The aim is to restore the stork as a breeding bird in Britain.

Britain is a very conservative country, and some conservationists argue there are not enough historical records to prove they belong here. You can spend years arguing with people about that.

But when ordinary people see these great birds spiraling into the sky or landing on their chimneys, they realize how spectacular nature can be. In a time when Britain is one of the most nature-depleted countries in the world, we need symbols of hope.

The white stork has become one of those symbols.

Alpha: So nature itself can regenerate quite fast if we get it started again?

Derek: Nature can regenerate if we help it. We’re very good at cultivating animals we want to eat — billions of chickens, millions of cattle.

But if we decide to help other creatures as well, there can be a different future for us as a species. We don’t have to be the plague we’ve become; we can be something benevolent.

Around the world there are remarkable people who devote their lives to the creatures they love.

Governments rarely save species. Often governments initially support industries destroying them. But small groups of committed people can change everything.

When North American bison were reduced to fewer than a thousand animals, a handful of people protected small herds. Those herds became the foundation for the hundreds of thousands of bison that exist today.

Alpha: On your farm you’ve turned it into a sanctuary for wildlife. Can you say a bit about that?

Derek: I originally accumulated about four hundred acres of land near Dartmoor. I used to farm here.

Now there are a few cows, but they are here as lawnmowers and to provide dung and hair for insects and birds. They are not here for meat or milk.

The grasses and herbs grow tall like hayfields. Voles live beneath them, insects burrow into the roots, dung beetles roll the manure into balls and take it underground.

We have opened perhaps a hundred ponds. The beavers create more wetlands every year. Birds like skylarks that once were absent are now breeding here.

Soon white storks will fly here and build nests on the farm buildings. We’ve reintroduced wild geese, water voles, water frogs, and many other species. Tomorrow we’re even moving ants to restore anthills that were plowed away decades ago.

We’re not saving the planet, but we are creating a place where people can see what is possible and be inspired.

Alpha: Do you have any advice for people who want to get into rewilding?

Derek: My advice is simple — bloody do it. This is not a rehearsal.

It’s easy to sit in an armchair and assume someone else will take responsibility. If something truly matters to you, look at what you can do and do it.

If you wait too long, age will catch up and the opportunity will pass.

Do it quickly and enjoy the rewards and the fun and satisfaction that come from helping life prosper.

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NASA scientist Matthew Rodell and colleauges figured this out using the help of some remarkable instruments. Two satellites with the name GRACE, flying in formation about 220 kilometers apart to meausure gravitational shifts. As the two satellites chase each other around the planet, tiny variations in Earth’s gravitational pull cause the distance between them to shift by as little as a micron, a fraction of the width of a human hair. And it is in those almost impossibly small changes that the story of the world’s water is written.

The principle of its operation its based on the concept that water has mass, and mass has gravity. When a region holds more water, whether in a swollen aquifer, a flooded plain, or saturated soil, it becomes fractionally heavier, and its gravitational pull increases ever so slightly. The lead satellite feels that extra tug first, pulling it ahead. By measuring the changing gap between the two spacecraft with extraordinary precision, scientists can essentially weigh entire regions of the Earth from space.

The resolution is about 300 square kilometers, meaning GRACE can’t tell you about a single lake or river, but it can tell you, with striking accuracy, whether a of about 300 square kilometer is gaining or losing water. Rodell’s team used this tool to find that between 2014 and 2016, land water dropped by the equivalent of 22 millimeters spread across the entire planet. Nearly a decade later, the water still hasn’t returned.

Their paper on this was called “An Abrupt Decline in Global Terrestrial Water Storage and Its Relationship with Sea Level Change. Here is the graph of their data. TWS is the total continental terrestrial water storage.

We usually think of droughts as local events, but the 2014-2016 crisis showed they can spread like a disease. It started with a record-setting drought in northeastern South America, which on its own would have been a manageable blip. But it happened during a period of extreme climatic instability, and the dryness didn’t just sit there. It cascaded across Africa, then Australia, then the Northern Hemisphere. By the end, 52% of the world’s land had hit record-low water levels, all at the same time.

Did this happen in the past? Well we are not sure as we only got the GRACE satellites in the early 2000s, and there’s no equivalent record before that. It’s possible the planet has experienced sudden losses like this in the past. But if it had, you’d expect the water to return once the rains picked up again. That’s what makes 2014-2016 different: the rains did return, in many places heavier than before, and the water still didn’t come back.

One reason for the sudden loss seems to be heat. A warmer atmosphere acts like a thirstier sponge, pulling more water back into the air before it can sink into the ground. Even when rain returned to drought-hit regions, it evaporated before it could recharge underground reserves. On top of that, we’ve cleared forests and paved over wetlands that used to hold water in the soil. Without them, the land has lost its ability to save water. The result is a new reality where the Earth’s water supply is running at a permanent deficit, and the old rules of recovery no longer apply.

But as we try to understand why the water isn’t coming back, our own water systems come under scrutiny. And here, a concept from network science offers an insight: explosive percolation.

In network theory, percolation describes how a system becomes connected. Normally this happens gradually, new links form one by one, and the network grows slowly. But under certain conditions, something different happens. The connections build quietly beneath the surface, and then all at once, the whole system snaps into a single giant network in one sudden jump. This is explosive percolation, and it has a troubling mirror in the way we manage water

As we’ve built more dams, pipelines, and irrigation systems, we’ve quietly been stitching the world’s water sources together. On the surface, this looks like good management: a more integrated system should be more resilient, more efficient, more controllable. But integration has a hidden cost. The more connected the nodes become, the more a failure in one place spreads to all the others. We have been, without quite realizing it, engineering the conditions for explosive percolation in our water systems.

Historically, water was stored across a vast, decentralized network, countless lakes of all sizes, wetlands, and underground aquifers spread across the landscape. If one failed, the others could compensate. A drought in one region would draw down local reserves, but the damage would be contained. The system had natural firebreaks. Iran’s ancient qanat system is a good example of how this once worked. Qanats are networks of gently sloping underground channels, some thousands of years old, that carry groundwater from mountain aquifers down to villages and farms across the desert. Because the water travels underground, it loses almost nothing to evaporation. And because the system is spread across thousands of small, independent channels rather than stored in one place, a failure in one part of the network has little effect on the rest.

We’ve been replacing that kind of network with something far more fragile: large centralized reservoirs. Iran itself made this switch over the past several decades, building large modern dams in place of its qanats. The result was a significant increase in water lost to evaporation, as vast open surfaces of reservoir water bake under the Middle Eastern sun. What the qanat kept cool and hidden underground, the reservoir exposes to the sky. This is the decentralization versus centralization problem in its clearest form: a thousand small, protected stores versus one large, exposed one.

Think of it like the difference between keeping your savings spread across many small community banks versus putting everything into one giant vault. If the small banks have a bad year, you still have most of your money. But if the giant vault gets overwhelmed, you lose everything at once.

This leads to an interesting hypothesis: could centralization, and the explosive percolation it enables, be partly responsible for the scale of the 2014-2016 drop and the failure to recover? In a decentralized system, water losses would have been absorbed gradually across thousands of smaller stores. But with so much water concentrated in large reservoirs, and those reservoirs increasingly connected to one another, a synchronized drought could drain the system far faster than before, crossing a threshold suddenly rather than declining gradually. And when the rains return, reservoir operators are often forced to release the water straight back to the ocean to prevent flooding, rather than letting it slowly percolate back into the ground. The land never gets the chance to refill.

The connections run deeper still. When we pump aquifers heavily for irrigation and urban use, we lower the water table, and rivers that once relied on their own local groundwater begin competing for baseflow from the same diminishing underground reserves. Problems cascade quickly across what once seemed like separate systems. And evaporation itself isn’t the enemy. In the Amazon, water that evaporates cycles back as rain and keeps the whole system alive. The problem is when water isn’t given the chance to sink slowly into the ground and return to the atmosphere on its own terms. That slow, patient cycling is what keeps water supplies healthy over time.

Some practitioners have been pointing toward a different path. Zach Weiss and Brock Dolman are among those who have been advocating for the decentralization of water. Their work focuses on slowing water down and spreading it across the landscape rather than channeling it into large central stores. The idea is to restore the land’s natural ability to absorb and hold water, through techniques like rebuilding wetlands, restoring floodplains, creating small ponds, and working with the contours of the land to keep rain where it falls for as long as possible. It is, in essence, an attempt to rebuild the thousands of small nodes that the old system once had, and that we’ve spent the last century dismantling.

Is the GRACE satellites measuring not just a climate problem, but also a water engineering one? The very act of trying to manage water more efficiently, connecting it, consolidating it, controlling it, may have made the whole system more brittle. Like a network on the edge of explosive percolation, it held together quietly for decades, and then in 2014, it snapped. The work of people like Weiss and Dolman suggests that the answer may not be better central management, but less of it. We haven’t just changed the climate. We’ve changed the plumbing. A centralized pipe, it turns out, is makes for easier for the large sudden loss of water.

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When it rains in a bioregion, we want to know: how does that affect the soil moisture? How long does the water stick around in the ground, and how does it seep through to the aquifers below?

To find out, we use watershed modeling. These models rely on what you might call water laws, equations for how the water behaves. Two of the main equations for how water moves through the soil and ground are Darcy’s equation and Richards’ equation. The results from the watershed models can be visualized on what’s essentially an ‘internet of maps’ called GIS (Geographic Information Systems). Through software like ArcGIS or QGIS, you can zoom into your own region on your laptop and see exactly what the soil moisture levels look like.

Imagine the soil is a sponge under a dripping tap. Richards’ Equation is the story of the first few minutes: the dry sponge greedily sucking up droplets through capillary action (suction). Darcy’s Law is the story of what happens an hour later: the sponge is heavy and dripping, and the water just flows through the saturated holes because gravity is pushing it.

Now imagine we’re engaging in ecological and water restoration across a bioregion, like what is happening with the Alvelal project in Spain, the Maharashtra Paani Cup project in India, the zaï pit projects in Burkina Faso, or the half-moon crescent projects in Chad. All of these interventions change how water filters downward through soil. How is that water moving? How much stays in the soil over time? This is where Darcy’s and Richards’ equations earn their keep. We can actually calculate what changes in soil structure and flow rates mean for water movement.

I could write this essay without any math, but for an essay about water laws, the equations themselves can give a little oompf. Feel free to skip the math part, but you might also want to give it a go. Once you stop being intimidated by the math part, you start seeing how cool the math is. For instance, the equation E=mc² packs a punch. When you see an equation, you can translate each symbol into English, then turn that sentence into something even more intuitive. Take E=mc²: E is energy, m is mass, c is speed of light. Translation: “energy equals mass times the speed of light squared.” More intuitive translation: “energy and mass are two forms of the same thing and can convert into each other.” Do this with any equation in any field, and suddenly they’re not so scary. You start to see them for what they really are: elegant abbreviations that pack entire ideas into a few symbols.

At the end of this essay I will show my initial attempt at turning ‘Slow it, spread it, sink it” into math, which will help us begin to calculate how much we need to slow, spread, and sink to restore a watershed.

Water underground

When water arrives as rain you can see and measure, but what happens next, whether it soaks into the soil or sheets away as runoff, how long moisture lingers in the root zone, whether aquifers slowly recharge or remain depleted, at what rate water moves through different soil layers, all of this occurs in darkness, beneath your feet, operating on timescales ranging from hours to decades. Yet these hidden dynamics are key. A permaculture designer planning swale placement needs to know where water naturally accumulates and how long it will persist after storms. An ecorestoration team revegetating a degraded watershed needs to understand whether their site can actually retain enough moisture through dry seasons to keep seedlings alive. A land manager trying to restore groundwater levels needs to predict recharge rates under different scenarios: current compacted conditions versus improved soil structure, native grasses versus bare ground, various rainfall patterns playing out over years. The questions are practical, where to intervene, what techniques will actually work, how to sequence restoration phases, but the answers require peering into processes you cannot directly observe.

This is not a new problem, the fundamental physics governing water’s movement through soil was discovered well over a century ago. Henry Darcy discovered in 1856 that saturated flow through porous media follows a simple law relating flow rate to pressure gradient and the material’s permeability. Lorenzo Richards extended this in 1931 to unsaturated conditions (the vastly more complicated zone where most plants live and die), capturing how water moves through partially wet soil where conductivity itself changes with moisture content, creating nonlinear feedbacks that can lock landscapes into either virtuous or vicious hydrological cycles. These equations (Darcy’s law and Richards’ equation) are the operating instructions for the underground water economy, describing with mathematical precision exactly the processes restoration practitioners need to understand: infiltration capacity, moisture redistribution, the difference between soil that welcomes rain and soil that sheds it like a broken roof. With modern computational power and Geographic Information Systems, these equations can now be used to model entire watersheds and visualize predicted outcomes for restoration interventions.

Darcy’s Law

Darcy’s Law is the rulebook for understanding how water seeps through sand, soil, and rock (the underground plumbing beneath our feet). Think of drinking a thick milkshake through a narrow straw versus sipping water through a wide one: the effort and flow are completely different. French engineer Henry Darcy cracked the math behind this in 1856 while studying sand filters for Dijon’s water supply. He discovered that water flowing through sand behaves predictably based on three things: how hard you’re pushing it (pressure or slope), how much space it has to flow through (cross-sectional area), and how easily the material lets water pass, called hydraulic conductivity.

[ Water moves at different rates through clay, silt and sand, which each has a different K, conductivity, a measure of how well it passes water through. Picture from this video]

Darcy’s insight mirrors Ohm’s law in electricity: just as electrons flow through conductors in response to voltage, water flows through soil in response to pressure gradients. Soil acts like a resistor network - well-connected pores are low-resistance pathways, while compacted soil creates bottlenecks. Transport through complex media depends on the interaction between the material and the driving force.

What emerged from Dijon’s need for clean drinking water became a window into how underground fluids move. Darcy measured flow through sand columns with patient precision and found that the relationship between pressure, flow, and resistance followed a crisp rule. Push water twice as hard, get twice the flow. Double the area, double the flow. Switch the material, and seepage slows.

Lets look at the math here. You have to unpack it slower than how you approach understanding a normal English sentence. The power of equations lies in their ability to capture relationships. Darcy’s equation does exactly this: Q = -KA(dh/dl). Take your time with it. Slowly translate what each letter means in English. On the left is Q, the rate of volume of water flowing through the soil. On the right, the terms that determine it: K is hydraulic conductivity (how easily water passes through that particular material). Don’t let the fancy term intimidate you. It’s just like electrical conductivity, except instead of measuring how well electrons flow through copper or rubber, it measures how well water flows through sand or clay. A is the cross-sectional area the water flows through, and dh/dl is the hydraulic gradient (the change in pressure or elevation driving the flow). Think of it as the slope of the water table. Steeper slope, faster flow, just like a ball rolling down a hill.

Now read your translated sentence: The rate of volume of water flowing through the soil equals how easily water passes through that particular material, multiplied by the cross-sectional area, multiplied by the change in pressure or elevation driving the flow.

You can translate it into even simpler terms: faster flow = larger area + more permeable + steeper slope.

This general approach can help you feel less intimidated by equations in any field of knowledge. Translate what each symbol means, then write out the sentence. Then translate again into something more intuitive.

The beauty is that K, the measure of how easily water passes through the material, varies wildly depending on what you’re dealing with - coarse beach sand might conduct water 10,000 times faster than dense clay. But once you measure K in the field for your specific soil, you can plug it into the equation alongside your gradient and area, and suddenly you have a quantitative approximation for how fast water is actually moving underground. The equation transforms scattered observations into predictions.

The law’s power lies in what it reveals about the invisible architecture beneath us. Every aquifer is a vast dark river flowing at geological patience through pores smaller than pinheads. Ecologists see how wetlands filter nutrients, their saturated soils acting as natural kidneys for entire watersheds. Foresters see why hillside springs appear where they do, why some slopes stay green through drought while others parch. Every contaminated site is a slow-motion catastrophe: invisible plumes of gasoline or solvents spreading through soil at feet per year, not miles per hour, following Darcy’s arithmetic.

Darcy stumbled onto something cool: an organizing principle connecting how rain soaks into a forest floor to how coastal marshes buffer storm surges, how desert playas trap fleeting moisture to how mountain snowmelt feeds valley streams months later. The equation has held for over 165 years showing the pattern of how viscosity, pressure, and geometry work together to move fluids through the hidden spaces of our world.

Richard’s equation

Richards came along in 1931. Lorenzo Richards, a soil physicist working in the arid landscapes of the American West, confronted a problem that had bedeviled hydrologists for decades: water moving through unsaturated soil refuses to behave politely. Darcy’s law worked beautifully when every pore space was filled with water, when the underground was a saturated sponge. But what about the vast zones above the water table, where soil is only partially wet, where water clings to particles in films and threads, where air pockets interrupt the flow?

Richards saw that this wasn’t just a technical problem but a conceptual challenge. He needed to marry Darcy’s elegant linearity with the fact that water is flowing from places where it isn’t to places where it is, while accounting for the fact that a soil’s ability to conduct water changes continuously as it wets or dries. The math describes how moisture content changes through space and time, how water creeps downward through gravity while simultaneously being sucked sideways and upward by capillary forces, how the hydraulic conductivity itself depends on how wet the soil is at any given moment.

Start by imagining what soil actually is. It’s not a solid block. It’s more like a chaotic sponge made of particles of different sizes jumbled together. Sand grains the size of beach sand. Silt particles smaller than table salt. Clay flakes microscopic and flat like tiny playing cards. Now add in the living stuff: root exudates (sticky sugars that plants ooze out), dead organic matter, microbial goo, all of which glue particles together into clumps called aggregates. The result is a three-dimensional maze of pore spaces (some wide enough to see with a magnifying glass, others so narrow that water molecules barely squeeze through single-file).

Now picture water moving through this. When the soil is completely saturated (every nook and cranny filled), water flows relatively smoothly, like traffic on an open highway. But most of the time, soil isn’t saturated. There’s water and air sharing the pore space. Water doesn’t fill pores evenly; it clings to particle surfaces in thin films, bridges across narrow gaps by surface tension, pools in tiny pockets. Imagine trying to pour water through a sponge that’s only half-wet: some pathways are open rivers, others are dead-ends where water has to creep along grain surfaces, and air bubbles block what would otherwise be shortcuts. Water gets stuck at constrictions, has to detour around air pockets, clings stubbornly to clay surfaces because of electrostatic attraction. The soil’s “willingness” to let water through (its hydraulic conductivity) isn’t a fixed number anymore. It changes depending on how wet the soil is at that exact moment. Dry soil conducts water miserably because there are so few connected pathways; as it wets up, more pores link together and flow accelerates. But even that process isn’t straightforward. Wetting soil behaves differently than drying soil, because water invades pores differently than it retreats from them. It’s like the soil has a memory of where it’s been.

To get to the law, the equation let’s start with the core idea in plain English: A patch of soil gets wetter or drier over time depending on whether more water is flowing into it from above than is flowing out of it below, and how fast water flows depends on how wet the soil already is, plus gravity always pulling downward.

Here’s what Richards did: He took Darcy’s equation (which works beautifully for saturated soil) and modified it in two crucial ways. First, he made the hydraulic conductivity K variable instead of constant, since it changes dramatically as soil wets and dries. Second, he combined it with the idea that water moves from place to place : water flowing into a layer minus water flowing out equals the change in how much water that layer is storing.

Why does this matter? Picture pouring water onto a dry kitchen sponge. Darcy’s equation would treat the sponge’s conductivity as fixed (measure it once, use that number forever). But when you first pour water on the dry sponge, it barely penetrates. The conductivity is terrible because water is clinging to scattered points with hardly any connected pathways. But as more water accumulates, suddenly it starts flowing faster. Pathways link up, the sponge darkens from the top down, and conductivity skyrockets, maybe 100-fold. If you tried to predict how fast water would reach the bottom using Darcy with a single K value, you’d be wildly wrong. Richards’ equation captures this: at every moment, it recalculates how easily water flows based on how wet the sponge is right now, then uses conservation of mass to figure out how the wetness changes in the next instant. The conductivity and the moisture content are locked in a feedback loop, constantly chasing each other.

Now picture a farmer’s field (two versions). In the first, the farmer has tilled for decades, applied synthetic fertilizer, and the soil structure has collapsed into a compacted mass with uniform, tiny pores. Rain hits this field and either pools on the surface or races straight down through a few cracks. Most of it becomes runoff. The hydraulic conductivity K is low and doesn’t vary much because there’s not much structural diversity.

In the second field, the farmer stopped tilling years ago, built soil organic matter, and let earthworms and roots create a chaotic architecture of aggregates (clumps ranging from sand-grain size to golf-ball size, with air pockets scattered throughout). When rain falls here, something different happens. Water first clings to the surfaces of these aggregates, held by surface tension and the stickiness of organic coatings. The small pores between and within aggregates fill first, and K is still relatively low. But as moisture builds, the larger pores between clumps start conducting water, and suddenly K jumps (maybe 10-fold, 100-fold). The soil can hold more water in temporary storage (higher moisture content at any given pressure) and the varying pore sizes mean water moves through the profile more gradually rather than all at once.

Regenerative farming practices (no-till, cover crops, compost additions) are literally reengineering this K(θ) function. You’re changing the shape of the curve that relates moisture content to conductivity, making it so the soil can absorb more water, hold it longer, and release it more gradually.

Now we translate this into mathematical symbols: ∂θ/∂t = ∂/∂z[K(θ)(∂h/∂z + 1)]

Here’s what each symbol means: θ (theta) is the moisture content (the fraction of soil that’s water). The ∂θ/∂t on the left is “how fast moisture content changes over time” at one spot. That’s the conservation of mass part, tracking whether water is accumulating or draining. On the right, ∂/∂z means “how things change with depth going downward.” K(θ) is hydraulic conductivity as a function of moisture. This is Darcy’s law with variable conductivity. The (∂h/∂z + 1) term captures both the pressure gradient (∂h/∂z) and gravity (the +1, always pulling down). The whole right side describes how flow changes with depth. If more water flows in from above than flows out below, that spot gets wetter.

Let’s look at the full equation again and connect it to “slow it, spread it, sink it”:

“Slow it” refers to interventions like swales, zaï pits, and terraces that change the surface conditions and keep water in contact with soil longer. Without these structures, rain runs off immediately and ∂θ/∂t (the rate moisture accumulates) stays near zero. With them, water is held on the surface, giving it time to infiltrate, so ∂θ/∂t becomes positive. The soil actually gets wetter instead of staying dry while water sheets away. In math terms, the earthworks help establish the boundary conditions.

“Spread it” means creating conditions for lateral water movement. When you build soil structure with varying pore sizes and add organic matter unevenly across a field, you create spatial variation in both moisture content and conductivity. This generates lateral pressure gradients. Water doesn’t just plunge straight down; it redistributes horizontally from wetter zones to drier ones. While this specific version of the equation tracks water moving down,, the same logic applies sideways. By creating different soil textures, we create side-to-side 'pulls' that spread water horizontally across the landscape.

“Sink it” is about increasing K(θ), the hydraulic conductivity at different moisture levels. Practices like adding compost, eliminating tillage, and growing deep-rooted cover crops create macropores and improve soil structure, which increases K. Higher K means the flow rate (the K(θ)(∂h/∂z + 1) term on the right side) is larger, so water penetrates faster and deeper into the soil profile. You get positive ∂θ/∂t deeper in the soil column. Water sinks into storage rather than running off the surface or evaporating from the top few inches.

Richards’ equation lets us quantify exactly how much you need to slow, spread, and sink. If you measure K(θ) before and after implementing regenerative practices, you can model how a 2-inch rainstorm will distribute itself through the new soil structure versus the old. Will that rain mostly run off, or will 80% of it infiltrate and be available to plants a week later? The equation gives you numbers. It gives you some idea whether your interventions are enough to prevent erosion on a 5% slope during spring storms, or whether you need more cover crop biomass to hit your infiltration targets.

This is where regenerative practice meets computational power to create a feedback loop for restoration. As communities around the world engage in bioregional regeneration of the water cycle (digging swales and terraces that reshape topography and slow surface flow, building soil organic matter that increases aeration and aggregate stability, planting deep-rooted perennials that create macropore networks), each intervention changes the physical parameters in Richards’ equation. Measure the new K(θ) curves after adding compost. Survey the altered slopes and water table depths after installing earthworks. Plug these updated values into watershed models, and the equations calculate how water will actually move through your transformed landscape during the next monsoon or spring melt.

These predictions can be visualized on GIS platforms: interactive maps showing where moisture will accumulate, where erosion risk drops, where groundwater recharge increases. Farmers, land managers, and communities can see projected outcomes, adjust their designs, implement changes, then measure again and refine the models. The equations become a feedback mechanism: practice informs measurement, measurement refines models, models guide better practice. Richards’ equation becomes a tool for collective learning, a way to track, quantify, and accelerate the healing of landscapes one watershed at a time.

By viewing our soil as a giant, responsive sponge, we can use Richards’ Equation to model the soak and Darcy’s Law to model the seep. When we feed these rules into a GIS, we turn invisible underground flows into a digital ‘weather map’ for soil. This allows us to see exactly how our restoration efforts (like swales or cover crops) are physically changing the way our bioregion holds onto life-giving water.

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I met Stephanie Betts a couple of months ago and was struck by her dynamic and enthusiastic energy. She had launched a pioneering, ambitious, and viable project to restoring the water cycle in a large scale systems way. Last week we sat down and talked about her project and her life.

Stephanie Betts had worked in law and investment banking and was leading meetings between M&G (global investment manager) , the Bank of England and NGOs like Client Earth, looking at best practice governance for climate. Then came her first aha moment: the CEO of AXA, a major French multinational insurance company, declared to her that a world at plus four degrees would no longer be insurable. Insurance, she realized, wasn’t just a financial instrument. It was the key to dealing with climate change.

She pivoted into insurance, becoming Head of Climate Alliances, Coalitions & Reporting for Aon - an insurance broker, that matches risk with capital, clients with underwriters, and counts major corporations and governments as clients.

Insurance, at its core, is about understanding and pricing risk. The industry runs on calculating probabilities and turning them into prices. Stephanie started looking at something more fundamental than individual premiums. She was seeing entire sectors, entire geographic regions, becoming uninsurable. When water systems fail, it’s not just one farm or one business that becomes too risky to cover. It’s everyone who depends on that watershed. The insurance industry had been tracking this for years through their payouts: floods and droughts accounted for a large proportion of their disaster claims. But what Stephanie realized was that this wasn’t just about paying out more claims. It was about approaching a threshold where the risk becomes so high, so unpredictable, that insurance itself breaks down. Whole classes of people, whole industries, would simply have no coverage available at any price. The system only works if risks are manageable and calculable.

Even before joining Aon, she had realized that water was important. But now it was getting clearer it was the fundamental risk underlying everything. Water runs through so many industries, from agriculture and technology to manufacturing and energy. It is the foundation of our society and the basis of our food security. As she puts it: “The risk isn’t just to the individual crop; it’s the dependency of our entire society on water. If the watershed fails, the entire economic system becomes uninsurable. We have to treat the water cycle as the ultimate infrastructure.” From within Aon, who initially just saw Stephanie’s interest in water as a hobby, she started to educate and convince the network around her of the importance of water.

Then came her next aha moment: she realized farming was key to the whole water issue. Agriculture uses a large percentage of our total water supply, and the water footprint of regenerative agriculture was much smaller than industrial farming. Regenerative agriculture was the way to deal with water. She began to focus intensely on this connection.

She saw that insurance could be a way to unlock investments, to get money flowing toward solutions. For the food industry, a switch to regenerative agriculture would make them less risky to insure. As she explains: “Insurance is the seed of resilience. By leveraging risk analytics, we can move from simply paying for a disaster to incentivizing the prevention of one. We are matching risk capital to the transition.”

In other words: instead of just writing checks after disasters happen, insurance companies could lower premiums for farmers who prevent disasters from happening in the first place. But more importantly, by fixing the underlying water risk, they could keep entire sectors and regions insurable.

The claims data said that regenerative farmers filed far fewer insurance claims than industrial farmers. They were more resilient. Through decades of heavy machinery and chemicals, industrial soil had become compacted and lifeless. When heavy rain hit, the ground acted like concrete. The water ran off, taking the topsoil and crops with it, leading to massive flood claims.

Regenerative farmers, using cover crops and avoiding tilling, had rebuilt the organic matter in their soil, creating a sponge effect. High-carbon, aerated soil can hold up to ten times its volume in water. In a flood, the soil sponge absorbs the excess. In a drought, that same sponge slowly releases stored moisture back to the plants. Regenerative crops often stay green for weeks longer than neighboring industrial crops during heatwaves.

For an insurer, it was key that a single farming practice lowered the probability of having to pay out claims on both ends of the extreme weather spectrum. Both floods and droughts. As Stephanie explains: “When we restore the soil sponge, we aren’t just fixing a farm; we are protecting the collateral. Healthy soil is an appreciating asset because it builds its own resilience against both flood and drought.”

In financial terms, collateral is what backs up a loan. If a farmer borrows money to operate, the land is the collateral. If that land becomes degraded and can’t produce crops reliably, it becomes worthless as collateral. But healthy soil that can weather both floods and droughts? That becomes more valuable over time, not less.

Industrial plants had “tiny little roots” because they were “spoon-fed” fertilizers at the surface. They didn’t need to work for their food. During extreme weather events, these shallow-rooted plants were easily uprooted. In healthy soil, plants had to reach deep into the earth to find nutrients and interact with fungi. Some of these roots could be a meter long, creating a massive underground anchor system. When storms hit, these plants stayed put.

Industrial farming also created economic volatility. Wild swings in costs and income. It depends heavily on expensive, energy-intensive inputs like fertilizers and pesticides. If gas prices spiked or supply chains broke, the industrial farmer’s costs skyrocketed. If they couldn’t afford the inputs, the crop failed. Regenerative farmers used the soil’s natural biochemistry to provide nutrients, creating more stable, predictable business models. For an insurer, a farmer with lower, more stable costs is less likely to go bankrupt during a bad year.

Stephanie applied this to what she calls the earth’s “first mile.” The beginning of the supply chain, where raw materials are actually grown in the soil. Industrial farming had turned fields into a toxic cocktail of compacted dirt. “Industrial farming has created a toxic cocktail of soil degradation,” she says. “From a financial perspective, this turns the land into a depreciating asset. It’s essentially mining the future to pay for the present.”

A depreciating asset is something that loses value over time, like a car. Industrial farmland, stripped of its nutrients and ability to hold water, becomes less and less productive. It’s like slowly destroying the machine that makes your money.

When rain hit these degraded fields, it ran off like it would from a parking lot, causing the downstream floods that insurance programs struggled to cover. The realization was that they needed to pay farmers to deal with flood and food security. To fix the problem at its source.

Then came the next step: to shift this system, we needed to focus on supply chains.

To understand why this matters, you have to step back and look at the fundamental question: what are the levers for large-scale change to restore water on this planet? Economics is one of the fundamental driving forces of societal behavior. And supply chains (the networks that move commodities from soil to shelf) are the basis of how the economic system actually works. They’re not just logistics; they’re the invisible architecture that determines what gets grown, how it gets grown, and who profits from it. If you’re looking for an innovative leverage point to shift the whole system, supply chains provide exactly that. Change the rules at the chokepoints (the handful of massive companies that sit between millions of farmers and billions of consumers) and the entire system has to adapt.

A few key companies control the flow of massive amounts of commodities. Change the rules at those chokepoints, and the entire system shifts. A powerful real-world example of this is the Flood Re model in the UK. Historically, insurance companies viewed floodplains simply as high risk. But as one-in-a-hundred-year floods began happening every decade, the industry reached a breaking point. They realized they couldn’t just keep raising premiums or building higher concrete walls. They had to manage the risk at its source. This led to a key moment for the industry, where they became advocates for nature-based solutions, recognizing that floodplains act as natural relief valves. They impacted where development occurred by refusing to give insurance to people who built on floodplains.

For the food industry operating on just-in-time logistics (where ingredients arrive exactly when needed with no excess inventory), any break in the supply chain is a massive financial hit. A drought in Brazil means no cocoa. A flood in Vietnam means no rice. Studies show that during drought years, regenerative fields can maintain yields up to 90% better than conventional neighbors. For corporations, that would mean consistent raw materials and protection against the price spikes that happen when harvests fail.

As Stephanie points out: “Investors and banks are looking for stability. In a world of volatile climate ‘fat-tails,’ nature-based solutions aren’t just ‘nice to have.’ They are a strategic hedge against systemic collapse.” (Fat-tails refers to extreme events that are supposed to be rare but are becoming more common.)

She used this argument, showing insurance companies and investment banks how to lower their risk and depreciation, and enlightening food corporations how valuable regenerative agriculture could be for protecting their businesses, to begin building a global partnership. After leaving Aon, she’s launched a project which has been assembling major food corporations, investment banks, and insurance agencies to incentivize and help finance the shift from industrial agriculture to regenerative agriculture. Their goal is to redirect several billion a year to create this shift.

“De-risking the first mile of the supply chain will help scale food production sustainably to feed a growing global population, while limiting supply chains’ impact on nature,” she explains. “Producers will benefit from lower raw material volatility. They will also have access to crop data on a real-time basis, allowing for transparency, risk management, and reporting.” They are initially focusing on cocoa, coffee, cotton, soy, and palm oil, water-intensive crops, for which a switch to regenerative agriculture will have a huge impact on the global water and soil footprint.

By making regenerative agriculture the new standardized requirement for these commodities, she’s working to use the leverage of global supply chains. The transformation is similar to what happened with the palm oil industry. For decades, activists and governments struggled to stop deforestation through treaties and local laws, with little success. The real tipping point will occur will when a handful of global traders (the chokepoint companies sitting between millions of farmers and billions of consumers) realize deforestation had become a massive financial and reputational liability. A regional example of this shift began in 2013 when Wilmar International, the world’s largest palm oil trader, adopted a “No Deforestation, No Peat, No Exploitation” policy. Within just one year, nearly all major global traders followed suit, bringing over 90 percent of the world’s palm oil trade under similar sustainability commitments. By setting these requirements at the refinery and trading level, the industry created a powerful market signal: if a producer’s methods didn’t meet the new standard, they risked losing access to the global market entirely. Once satellite monitoring caught up to these corporate pledges, palm oil-linked deforestation in Indonesia and Malaysia plummeted, eventually dropping by over 90 percent from its peak.

By proving to insurers, investment banks and corporations that regenerative agriculture protects their concerns of food stability and supply chain reliability, Stephanie's working to turn the insurance industry and global supply chains into engines for water and soil restoration.

Below is edited version of segments our interview. In the full audio version, you might find the final third particularly intriguing if you are interested in finding out more about how supply chains can be such a leverage for restoring water and soil.

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Alpha: Hi, it’s great to be here. I have with me today Stephanie Betts. Welcome.

Stephanie: Thanks, Alpha, it is really nice to meet you again. I’m really excited to be on the podcast. A lot of people used to say water was my hobby. I’m glad to see that it’s not just mine. It’s a real topic that many people are spending a lot of time thinking about now, which is great.

Alpha: Yeah, great to have you. You’re going to bring a different dimension to this whole water topic that we don’t talk about as much, which is the insurance and some of the finance side.

Stephanie: Yes. My background is a bit different from a lot of people you’ve interviewed because I spent a bit of time looking at the archive to make sure we brought something that was a bit different. It’s not so much about the science of water and what happens—really gaining a deep understanding of the water cycle, which is fascinating and something we learn about all the time—but it’s really about how we move forward. It’s about solutions, action, and how we handle the risk that we’re facing now. We have increasing dependencies that we’re more aware of in terms of business and the global economies and the way they work.

In a way, that’s not linear. We’re facing risks that are starting to be multi-layered and nonlinear, and how do you deal with that? I think the goal is to think in systems because if you look at water, it’s a very layered system. You have transportation, rain, cloud seeding, plants, and roots—all sorts of ways in which water connects to other parts of the system. I think that if we want to address the large-scale problems we’re facing on the planetary level, we need to start thinking in layered systems as well.

On planet Earth we have enough water so far for most people to live comfortably (if we set aside the 2 billion plus people who actually do not have access to safe water already) means we’ve been lucky to have these “pale blue dots.” What do we do next to make sure we can stay, and that the next 50 years do not see us disappearing? Because if you run out of water, you run out of life. It’s a pretty urgent situation.

Alpha: I’m excited to dive into these solutions with you, but how about we first get into how you got into water and your background?

Stephanie: My background is actually law. I started as a disclosure lawyer working for a law firm called Sullivan & Cromwell, which is a well-known Wall Street law firm.

That had a profound influence on me because I’ve always had this idea that you need transparent information; investors need to make the right decision. If you do not have the right level of information, you cannot make the right decision and you end up with financial markets that are not working optimally.

From there, I went to investment banking and brokering for nearly 20 years where I worked for Lehman Brothers first, then JP Morgan and Citigroup. I’ve done my “tour of duty” in the big funds in the financial system.

From there, I set up a sustainable business which brought me a bit more forward as to what is happening outside of finance. I realized people didn’t know very much. I realized that finance knew enough to take action, but they were not yet taking the right action. So I decided after 10 years of setting up this business—which involved cotton, hence why the water footprint became important for me—to go back to the City like an activist hiding in plain sight, trying to find the levers for change.

I decided not to go back to my old world because I knew that investment banking world. I decided to go into asset management because they were my former clients and I wanted to see how people who manage huge amounts of money embed climate risk. I joined M&G for about four years, ended up working with the Bank of England and engaging with their climate unit to see how we could improve our practices as a firm to disclose more on climate.

How are we going to hook financial systems to the right level of disclosure so we can get to the right outcomes? After that, I realized that finance is good, but it’s not really where the big lever is. I know it sounds odd, but actually what I found out is that it was insurance. I decided to join insurance just to get under the skin of it all, so I joined AON, the global insurance broker. That was phenomenal because there I had a first-hand view of what clients are thinking about when looking at risk, what kind of risk they are looking at, and what insurers are able or not able to do.

That was the beginning of my thinking around water, which led me to set up my own business about two years ago to tackle that problem. I’m happy to delve more into the issues we’ve seen and how we’ve designed a platform and a solution to hopefully start. It’s a complicated thing, but I’m thinking again in terms of engineering: how we kickstart change and make sure we can hook the best solutions that already exist to better outcomes. We do not have the time to reinvent the wheel. We do not have the time to totally change capitalism, but we can rewire certain areas of it and that alone will give us the levers to get better outcomes.

Alpha: Well, you have a fascinating background coming in from this with investment banking and the sustainable business side. A lot of people do think finance is the leverage and are worried about how economics and money fit together. It’s interesting that your insight was that it was insurance that was the lever. Do you want to explain a little bit more?

Stephanie: Yes, there were two levers. It was really interesting. I remember the precise moment. I was always concerned about climate. When I left the City 20 years ago and I told my clients, “Guys, I’m going to be away. I’m having children. I don’t know when I’m back, but watch out for clean air and clean water. We’re going to be running out of all of that, and keep an eye on commodities.” That was my farewell to them.

I could see that India and China were expanding and industrializing at a fast rate. In Europe—I’m speaking from England, but I’m French (and half Haitian, which is interesting for topics like water problems, erosion, and deforestation)—you could see it took the developed world 200 years to get there while China and India were doing this over 50 years. You can see the strain it brings on the systems and the entire population, which is exploding worldwide. We’ve gone from 5 or 7 billion to looking at 10 billion very shortly. Suddenly we’ve doubled the population, but the resources have shrunk. We need to manage that, and water is at the absolute nexus of all of that.

One day, I was sitting next to an elevator doing some research for a presentation, and I came across a quote from the then CEO of AXA who said that a world at +4 degrees would no longer be insurable. That was that. There was a before and after. As a lawyer, you think an uninsurable world is a very scary world. As a young adult, I did an internship in Haiti where the rule of law was non-existent. I could really see what an uninsurable world looks like. You buy a house and someone says it’s not your house. You try to sell it and they say no. People come and seize your property. You’re not insured for anything. If you cannot insure your car, you’re not going to get in your car. If you cannot insure a project, that project is not going ahead. Interestingly, you can have the money from finance, but if insurance doesn’t want to insure a program or an asset, your asset is now valueless. You’re starting to see that in pockets of California where people are struggling to get insurance for their homes. Insurance has a huge role to play as a lever.

Then a very good friend of mine, who was a very senior underwriter at Munich Re, and I used to chat about work. The more I talked about it, the more I thought what they were doing was interesting. They were insuring everything. I thought, “Is there anything you do not insure?” and he said, “No, because if the world has to go around, you need insurance.” When I put the two together, I knew I had to go into insurance. That’s when I went to AON. It was clear that for many clients, especially in the food and beverage area, climate change was the biggest issue. They didn’t necessarily know how to handle it and the long-term structural problems like yield attrition and lack of water.

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Alpha: Say more on AON.

Stephanie: AON is one of the largest brokers worldwide for insurance. They match risk and capital. They find companies that need insurance and find the right underwriters to insure that particular risk.

Alpha: Can you explain more about your perspective? You said as a lawyer you looked at this situation being uninsurable. What are the legal ramifications for that? My friends were trying to buy houses in California and had problems with insurance due to wildfires.

Stephanie: The problem is that a bank will only lend you money for a mortgage if they know they have an asset they can eventually repossess. That’s the guarantee. But if that asset is not insured—especially in a high-risk region like California—the banks can’t give you a mortgage. It’s that little grain of sand that can stop everything from moving.

Imagine you have a huge project and need to invest hundreds of millions in building infrastructure. Banks are not going to lend hundreds of millions for a big project unless it’s insured. And insurance is not going to play ball if they don’t have data that proves they’re not going to lose their shirt on that investment. Interestingly, large parts of the world like Africa are almost entirely uninsured. There is almost no insurance in Africa. Why? Because insurance doesn’t have enough data to be able to run the right calculations. Insurance is a numbers game.

But what’s been fascinating recently is even the numbers game is changing. Right now, the problem is—and you’ll need a climatologist to tell you more about this—you have these fat-tailed risks that are coming more often than they used to. The calculation you had based on previous cycles is not necessarily applicable to the world going forward. That’s a big break for insurance. How do you handle that when the frequency and intensity of extreme weather events is accelerating?

If we don’t deal right now with the underlying cause of those extreme climate events, insurance is going to become irrelevant because premiums will become so expensive people can’t afford them, or there will be events that you can no longer insure for. We still have a window, but we need to move.

In Phoenix, Arizona, you can no longer build a development unless you can confirm you will have water supply for the next 100 years. It’s getting harder to prove. Local governments can’t issue permits if they think people will be stranded with no water. They’ve been relying on groundwater, but they have drought, hotter temperatures, and pressure on the Colorado River.

I see a conflict coming between finance and population. You have hedge funds saying water is “the next oil” or “the next gold” and buying water rights, and then you have farmers and populations. Finance, business, and industry all need access to water—from energy to data centers. Then you still have to feed the population. How do local governments allocate water to these different constituents? Phoenix is a huge hub for data centers, which use millions of gallons of water, creating competition with agriculture.

Alpha: You have a timeline of how you came to the realization of it. You were a lawyer, then in investment banking, then you had a realization about insurance. At what point did you have a realization about water and the soil?

Stephanie: Good question. I always have a visual moment of when the penny dropped. I was at Aon and I thought, “If insurers are grappling with these big problems, what do we do to calm things down and rewind a little bit? What is the lever of change?”

I realized the biggest issue was that in a warming world, we’re going to have less water available. Then I looked up the biggest influence on water. It was so simple: 70% of the world’s fresh water goes straight to agriculture. When you think about the water in your shower, that isn’t it. It’s what you eat and what you wear.

I knew that regenerative agriculture was able to reduce your needs in fresh water by about 50%. If on a global basis you could move from 70% to 35%, that gives you a huge margin. We can’t move the whole planet to regenerative systems right now, but we can try because that’s when we’re going to reduce the pressure on water.

Alpha: I don’t think a lot of people connect that. They realize agriculture uses a lot of water, but they don’t say the solution is “regen,” at least in the insurance business.

Stephanie: It’s coming. People are getting serious about this because it’s happening. We’ve seen the ground collapse in places like Turkey because people have taken too much water out of the ground. When yields are down by 50% because of drought and the soil is unable to cope, or when floods take away the topsoil, you realize you’re trapped in a negative loop.

For me, it was straightforward: we need to look at soil. A healthy soil is very open and aerated. You have the worms and the fungi interacting. When the rain comes, it acts like a sponge and can hold up to 10 times its volume in water. When you look at the roots of plants in healthy soil, they can be a meter long. But in poor soil, you have tiny little roots.

When an extreme weather event like a storm or flood arrives, the crops with short roots get pulled away because the topsoil gets washed away. The plants with deep roots don’t get pulled away because the soil is elastic. When the event is over, they recover and they have plenty of water because they are saving it. When the next event arrives, like a drought, they can access water deep under which the others can’t. What’s happened is over 50 years of intense agriculture with tractors compacting the soil, but also with a lot of fertilizers that have killed the unique biochemistry of the soil. All that good soil infrastructure has been lost. That is what regenerative farmers are trying to rebuild. People like Gabe Brown, for instance, are at the forefront of this. There is a massive movement in America and a “Groundswell”—which is also the name of an amazing conference here in the UK—of regenerative farming.

What gives me hope is that insurers are smart; they follow the money. In all these conversations, we need to follow the money, because that is the only way you get solutions that people will adopt and keep. Insurers are starting to notice they have two types of farmers. Traditional farmers who use heavy pesticides, chemicals, and heavy machinery are hit very hard by extreme weather events. They are always putting their hands up for a payout. The other pool—the regenerative farmers—actually don’t need payouts because their crops survive the events.

Suddenly, insurers are looking at these two pools much like they did with smokers and non-smokers in the 1980s. They are starting to give them very different insurance costs. It is becoming more financially beneficial to move to regenerative agriculture than to stay with existing protocols.

Then there is the nutrient element. I tell my children, “I’m trying to save your bacon here.” Most food in shops is made using products that weren’t “good enough to get in my car,” because fertilizers are often toxic byproducts of the chemical industry. People naively think pesticides just mean bigger fruit; they don’t realize that what goes into the soil goes into the plant, then the animal, and eventually into us. That is why we have escalating issues with chronic illnesses. We need to make good food accessible to all, but that requires a major system change.

People often ask, “How can we be running out of water when it rains so much and there are floods?” I tell them, “Do you want to drink the water on the road?” That water damages aging infrastructure and carries topsoil runoff. A friend of mine farming in Devon recently had a “one-in-a-hundred-year” flood. Farms all around them were wiped away, but because they have practiced regenerative farming on their estate for years, their water was running clear. The water sank into the ground, and they didn’t lose any crops. It’s very concrete.

If we can harness governments and insurance to move to regenerative practices at scale, it will make a massive difference. Our supply chains were set up 200 years ago for a very different world. We are operating under different constraints now. A big part of preserving water is looking at your diet—the water footprint of your food. I looked up the footprint of a simple lunch sandwich: it’s about 200 gallons. If you add a bag of chips, it gets “spicy.” The water used to irrigate the potato is one thing, but then it goes to a factory to be washed, processed, and packaged. Each step adds to the water and carbon footprint.

In my perfect world, you eat flavorful, seasonal food from a regenerative supply chain. We need to make people dream about this possibility, not just scare them. A brilliant example is Louise Mabulo and The Cacao Project in the Philippines. She created the “Napa Valley of Cacao” by helping farmers move to regenerative practices. These farmers are now making money, buying cars, and improving their lives.

We have a planetary problem, so we need a planetary solution. I decided to focus on five “worst” supply chains: cacao, coffee, palm, rice, and cotton. Cacao, coffee, and palm are linked to deforestation that disrupts the water cycle, while rice and cotton use extreme amounts of water. Our project creates a “plug-and-play” program for corporates to transform their supply chains from depleted to regenerative.

Supply chains are engines that go all around the world. Instead of making them engines of destruction, we make them engines of regeneration. We’ve brought insurance and finance into the mix, creating a big insurance pool for each commodity. We’re working with partners like Aon, ERM, and Fauna & Flora.

Alpha: Are your working with all insurance companies?

Stephanie: It’s a mix of insurance, finance, and organizations that work on the ground with farmers. If you are a company like Nestlé or Mars and you want to ensure your beans are free from deforestation, how do you know? There is a massive gap between the head office in Switzerland or the US and the “first mile” of the supply chain.

We are bridging that gap with technology. Five years ago, it didn’t exist, but now with AI and satellite data, we have transparency. You can see a chicken run from space! But data isn’t enough; you need infrastructure on the ground. You need agronomy, village champions, and investment in tools. We are giving corporates a “sweetener” with insurance to work across the entire arc of the supply chain. This creates better livelihoods for farmers, lower volatility for corporates, and higher GDP for governments.

Alpha: You saw that agriculture is the key thing, and that regenerative agriculture is more resilient to “fat-tail” risks. You’re leveraging the companies downstream that have the money to help the farmers upstream switch. It’s a key to the whole system.

Stephanie: Exactly. We are losing between 25 and 75 billion tons of fertile topsoil every year. It takes 100 to 1,000 years to rebuild just one centimeter of that soil. At this rate, 90% of the world’s soil will be degraded by 2050. It’s like an office where nine out of ten employees don’t show up for work; nature is hanging on by a thread.

Indigenous populations have this right; 80% of remaining biodiversity is under their control. We need to go back to that old wisdom. It’s not a corporation’s job to worry about planetary boundaries—their job is to make chocolate or coffee. That’s why we stepped in. We are running pilots in Africa and Latin America to “test the plumbing” of this architecture. Once we are up and running, we are talking about a billion dollars at work in each supply chain.

It isn’t even that expensive because, once engineered properly, the program pays for itself. If you take a tiny sliver of the $500 billion coffee trade and invest it in a concerted way, the impact is enormous. AI enables us to exchange information and monitor protocols across different landscapes. There is a small window of time, but a massive opportunity.

Alpha: This is mind-blowing. In finance and insurance, everything is about incentives. You started with insurance because they have a direct incentive to address water risk.

Stephanie: The main game for me is water. Nobody wants to pay for water because it’s a common good—the “tragedy of the commons.” But if you hook it to a value people do care about, like a smooth supply chain or protecting their assets and bonuses, you hook it to capitalism. Depleted supply chains work for no one. Once farmers make money through these practices, they become a brand new market for insurance. Remember, the protection gap is 70% worldwide. Insurance has 70% to gain by helping the world become more resilient.

Stephanie: There is plenty of room to grow, but we need to do a few steps first. You have to make sure people have better livelihoods so they do the right thing to support those livelihoods. It’s all about how you hook it and how you organize it. Depleted supply chains serve no one, but regenerative supply chains serve everybody. They serve the head office, the customers, the farmers, the government, and the insurers.

The challenge was moving from depleted to regenerative. That transformation is difficult because no company can do it on its own. But if you do it at the supply chain and country level, with the support of government and policy, it suddenly becomes a new norm. Think about seatbelts. Nobody cared about seatbelts in the 70s; kids were just driving around. Then, suddenly, you had to have them, and now everybody wears one. You needed policy for that.

Things like that can happen overnight, but we don’t have policy at the planetary level yet. So, we had to go via the market. Once it happens in the market and people see the benefits, we’re hoping other supply chains will have “FOMO”—they’ll want to do the same.

Alpha: This is a really interesting point. Last year, we were looking for the trigger points to tip the water cycle into better systems. We talked about different places to push, but none of us were thinking about supply chains. It’s a foundational economic idea. Since supply chains are the engine of the whole system, revamping them shifts the incentives to align with the water cycle.

Stephanie: To get there, we just need a shift in those supply chains because they are the only things big enough and efficient enough to give us the fast transformation we need. Policy is one thing, but if policy isn’t moving, we go to the market. When I was a kid, I remember Superman going around the globe so many times you could see the lines of his travel. That’s how I see supply chains in my mind. They are “Supermanning” the globe in cars and trucks; they are everywhere and impacting everything. If we can make them supportive of a better life and water, we win.

Water is my real mission—my not-so-secret mission. But we needed to embed it into something financially relevant for companies. That’s how you hook it to insurance and the financial system to create a chain reaction.

Alpha: How much is the idea of water discussed in the insurance and finance sectors right now?

Stephanie: I’ll be honest with you: water and insurance is a complicated one. The Green Climate Fund has a smart water expert who is looking at infrastructure projects worth $12 billion a year. But water is challenging because it’s a common good. That’s why you see people buying land for water rights and digging deeper to grab more water. You see it in California with thirsty crops like almonds; a farm turns on the tap and nothing comes out because a hedge fund next door had the money to dig deeper.

Alpha: You’re pushing the economic side, which influences policy. If a corporation is whispering to the government that they need to restore the water cycle, policy becomes easier.

Stephanie: And they’ll want a reward for it! When they show investors they are looking after nature, it’s a benefit. We also have sovereign wealth funds like Norges Bank and the Japanese pension funds making big moves. Norges Bank issued a report stating that 96% of their assets were exposed to “nature risk.” They told companies: “If you do not report on your impact on nature and show us a direction of travel, we will dump the stock.” These are funds worth two trillion dollars.

I think the next step is the stock exchange requiring disclosure on nature. Nature underpins our financial system; everything we trade, eat, or fly comes from the ground. If the ground is depleted, we cannot continue to create economic growth.

There was an enormous report by the CFTC (Commodities Futures Trading Commission) called How to Manage Climate Risk in the U.S. Financial System. They said the prices in the options market are no longer real because nobody knows how climate will affect the “underlying asset.” We have no idea what orange prices will be in five years. We are working on very thin ice, and that is a “zone of danger” for the global financial system.

Once you ask people to disclose a risk, they naturally start to manage it. Managing it means reducing our footprint on natural capital and water. It’s about resilience—not just because I love beavers and keystone species, but because the resilience of our financial system is intricately linked to nature.

Alpha: This has been amazing—seeing how to use supply chains for a massive shift in regen ag to help the water cycle. Any closing words?

Stephanie: Just thank you for listening and for your interest in water. People often forget they have agency. As citizens and communities, we have the power to buy the right products and support the right supply chains. Never forget you’ve got agency—whether you work in policy, investment, or just as a consumer. We have the power.

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In Bolivia, farmers wait anxiously for rains. Meanwhile, Bolivian consumers buy beef and soy from Brazilian suppliers whose operations are clearing the very Amazonian forests that generate Bolivia's rainfall. The atmospheric connection is real but the economic feedback loop is invisible. If Bolivian businesses and policymakers could see this connection as clearly as they see a map of trade routes, would they make different choices about whom to buy from? Would Brazil negotiate differently if it understood that the forests it's clearing don't just affect its own climate, but control a neighboring country's water supply, a country that happens to supply a significant percentage of Brazil's natural gas?

These are the questions that the work of Patrick Keys, a professor at Boston University, raises. He is taking the work of moisture recycling (aka the small water cycle, aka precipitation recycling) in exciting and pioneering directions. He is making the geographical sinks and sources of rain clearer, and then transforming moisture recycling from atmospheric physics into something socio-politico-economic: maps that show which upwind regions supply a location's rainfall, and frameworks for understanding how economic decisions in those distant regions create invisible dependencies. He's building the conceptual infrastructure for embedding atmospheric connections into the social and economic systems that actually shape land use.

Working with Ruud van der Ent (interviewed here previously), he developed the precipitationshed framework, which maps how much rain falling in a particular location comes from which upwind regions. A city might receive portions of its rainfall from countries A, B, and C, or provinces D, E, and F. By making these connections spatially explicit, the framework transforms vague atmospheric dependencies into actionable geographic information.

This required inventing new vocabulary - terms like precipitationshed and evaporationshed had to be coined to discuss atmospheric source regions, linguistic innovations necessary for thinking clearly about phenomena that previous frameworks couldn’t adequately describe. From their paper, precipitationshed is ‘defined as the upwind atmosphere and surface that contributes evaporation to a specific location’s precipitation (e.g. rainfall). We apply the precipitationshed as a tool for better understanding the vulnerability of rainfall dependent regions (e.g. dryland rainfed agriculture).” [Keys 2012]. The precipitationshed gave moisture recycling the same kind of geographical grounding that watersheds gave to rivers.

Keys then applied this framework to map mega-cities worldwide, identifying which might be most vulnerable to land-use change in their precipitationsheds. His 2018 paper combined precipitationshed boundaries, rates of land-use change in source regions, reliance on terrestrial versus oceanic moisture, and robustness of municipal water infrastructure to create a vulnerability index. It was the beginnings of a translation exercise of sorts: how to convert land and atmospheric physics into the kind of comparative risk analysis that could sit alongside assessments of aging pipes or aquifer depletion in a city planning document.

The mapping of atmospheric vulnerabilities built the platform for his next stage of work. Together with Lan Wang-Erlandsson (also interviewed here previously), Keys pushed the framework into new territory: moisture recycling as an ecosystem service embedded in social and economic systems. Places downwind buy from businesses upwind that affect the land. Economic behavior affects how businesses treat the land, which then affects the rain downwind. It’s a feedback loop where economic behavior is integrated into the hydrometeorological flow.

In their 2017 paper “On the social dynamics of moisture recycling,” they propose a new field: socio-meteorology. And they write: “this paper provides insights for resource managers, particularly land and water managers, who are searching for new leverage points within their dynamic social–ecological systems. Understanding where key feedbacks, bottlenecks, and potential cascades are located within a system can provide managers with better information about the consequences of direct or indirect intervention within their systems.”

Keys and Wang-Erlandsson analyzed three countries with different social-ecological configurations. Mongolia recycles 13% of its own moisture and receives 29% from Russia. Its precipitationshed is geographically vast but socially isolated - the moisture comes from remote Siberian forests and Kazakh steppes with little economic or political connection to Mongolia. Niger generates only 9% of its own rain, depending on moisture from Nigeria, Chad, Sudan, and across the Sahel. Here, multiple neighboring countries with active trade relationships, migration flows, and shared resources all influence each other’s rainfall through land-use change, creating a regionally interconnected system.

Bolivia recycles 18% of its own moisture and receives 28% from Brazil. Brazil’s soy and beef production drives Amazonian deforestation, reducing moisture available to Bolivia. Yet Bolivia supplies a signficant percentage of Brazil’s natural gas imports, creating economic interdependence. Global commodity markets, international conservation programs and distant financial actors all influence land-use decisions in Bolivia’s precipitationshed - what Keys calls a tele-coupled system, where spatially disconnected actors drive local change while experiencing no feedback from the atmospheric consequences.

Through these case studies, Keys and Wang-Erlandsson mapped the complex networks of interactions, categorizing different network topologies as isolated, regional, or tele-coupled, and showing how each creates distinct governance challenges. Their work sits at the intersection of economic geography, which examines how location shapes economics; spatial economics, which studies the role of distance and place in economic systems; and ecological economics, which constrains economic analysis by biophysical realities.

The rain falling on your city isn’t just a weather event. It’s the downstream consequence of land-use decisions made by people you’ve never met, influenced by market forces you don’t control, mediated by institutions that don’t know you exist. And your economic choices -where you buy your food, what you consume - are propagating back through that same system, affecting rainfall patterns elsewhere in ways you can’t see.

Economic activity in one location, such as deforestation for cattle ranching, reduces moisture available to another location through reduced rainfall for agriculture, creating invisible water transfers mediated by the atmosphere rather than by shipping containers. Every economic transaction that changes land use is simultaneously shifting hydrometeorological patterns - a causal chain that conventional economics typically ignores.

Keys describes his vision for a coupled model that could simulate these systems dynamically - tracking not just moisture flows but also economic networks, political institutions, social dynamics, and climate change, all interacting in real time. “If you think it’s actually a social ecological system, some sort of complex adaptive system with feedbacks, then you have to be able to do that,” he explains. “You have to be able to kind of have the other part of that connection. Otherwise, it’s like only it’s like half of a simulator, right?” Building such a model would require bringing together network scientists, economists, political scientists, and climate modelers together to connect the dots.

Here is an abridged, edited version of our interview into the exciting fields of precipitationsheds and the socio-economic-political dimensions of rain

Pat: I’m an assistant professor in the Department of Earth and Environment at Boston University and I have been doing moisture recycling research since 2010. My background is kind of a real mixed bag. I have an undergraduate degree in biology from Willamette University. I have a master’s of science and civil engineering from the University of Washington with a focus on kind of water resources and climate change. Then I started an environmental consulting company called Keys Consulting Incorporated, super creative name, and we focused on climate change, impacts, adaptation, resilience with clients all over the place, with projects all over the world. Then I realized I was still really curious about the world and I had a chance to go back to get my PhD and so I took it and I got my PhD in sustainability science at Stockholm University. I was a research scientist at Colorado State and then I moved into an assistant professor role. Then I recently moved to Boston University. That’s like a real quick snap.

Alpha: Cool. Moisture recycling also goes by other names, precipitation recycling and small water cycle. You want to just say briefly what it is?

Pat: My research is quite a bit broader than moisture recycling but I spend a lot of time in that world. For me, the idea of moisture recycling is just a atmospheric water cycle. It’s thinking about the sources of water on the surface of the earth. That’s evaporation, transpiration. It can be either from an ocean or a land surface. The moisture recycling part is understanding where it arises, where it travels through the atmosphere and then where it falls out later as precipitation of some sort. I know some people define moisture recycling on a much more local scale or a regional scale or only on land or all sorts of things. For me though, I take a pretty broad view and it’s just this idea if you’re tracking and understanding the sources and sinks of atmospheric moisture, you are probably thinking about moisture recycling in my mind.

Alpha: Okay, cool. Did you get first get interested in this when you were doing your PhD at Stockholm?

Pat: I went out to the Stockholm Resilience Center and worked with a whole bunch of different people thinking about surface water. I upgraded a surface watershed model for that fellowship. Right at the very end, Line Gordon and I started talking about this other project idea, which was instigated by a conversation Line had had with a colleague of hers, Huberts Savenije in the Netherlands. Line said, hey, I know this guy and he has a master’s student that had just come out with this really cool paper on moisture recycling.

And so we had this big plan to try and build a research team with me and the Stockholm group and with Hubert Savnije and Ruud van der Ent in the Netherlands. So I’ve known Ruud since 2010. I know you had him on your show.

The first paper we sort of cooked up was this idea of precipitationsheds, essentian analogy to surface watersheds - how can we think about sort of airborne sources of moisture, sources and sinks.

I actually still have a notebook somewhere where at the time Ruud and I were trying to talk about what would be the best name for this sort of unit, names like skyshed and rainshed. The other day I found this notebook and I saw all these names crossed out.

Alpha: That’s cool. I like hearing stories about how words came into being because basically you’re defining a lexicon for a new kind of field. I have heard people talking about the precipitation shed.

Pat: Well honestly its I think the most important thing in looking back at that body of work the idea of this unit. Let’s work with this unit in a spatial sense, because it permits talking more specifically about an area on the surface of the earth that might be connected to some other place downwind.

The purpose was to try and see whether or not that was a reasonable thing to do. Like, and that’s actually what my PhD was really all about was like, how reasonable is this approach? How useful is this idea? That’s what my PhD ended up being on.

Alpha: And the ‘shed’ part is to make you think about the watershed to kind of analogize that idea.

Pat: Sort of that. And also that it’s shedding, it’s shedding moisture.

And so we want to understand what was the kind of upwind area, the upwind catchment, so to speak, that supported precipitation in a particular location. I am interested in are people using the source and sink idea more now? And I think they are.

Alpha: So the precipitationshed tells you the source of where you’re waiting for comes from. There’s also one a word for where it goes

Pat: That is something that Ruud coined in a paper that he wrote, I think in 2013 which was the evaporationshed. So that’s where does a region’s evaporation go?

Let’s take Colorado, for example. So you can think of all the places that contribute moisture to Colorado. So that sort of set if you drew a circle around it, that would be its precipitationshed, the place that supplies Colorado precipitation.

The tricky question is how do you draw a line? Or how do you weigh the importance of regions that are contributing moisture? Because ultimately, a lot of regions could be contributing tiny, small fractions of moisture. So at some point, you want to say, Well, we’re not really talking about those places.

So which places are we talking about? That gets to be pretty tricky. And I think that’s also where this very hydrology oriented subject sort of butts right into sustainability science, which is a very problem oriented thing. We’re talking about land use change, we want to understand the consequences of land use change in this particular place. Well, then maybe whatever lines that you draw in terms of upwind and downwind source and sink regions might have to correspond in some way to that would that would matter to this problem that you’re focusing on.

Alpha: So for Colorado, what would you say the precipitationshed for Colorado and what is the evaporationshed for Colorado?

Pat: My master’s student that just graduated just did that. So, so what her work shows, her name is Katherine Humphries. She just finished her master’s degree at Colorado State. And what she found is that the sources of moisture for Colorado, for Eastern Colorado, and especially the northeastern part of Colorado - lot of it actually comes from kind of regional sources. When I say regional, I mean, within Colorado, and adjacent states, there’s a pretty substantial contribution from the Gulf of Mexico, the Pacific Ocean, also from the Gulf of Baja California, so that body of water. There’s also substantial continental sources as well. And how much? I would actually like cite the paper, but she’s submitting the paper sort of like this week, so I can’t cite it yet.

Alpha: How much does California contribute to Colorado’s rain?

Pat: A little bit, some. And I should say again, this is, I’m really speaking primarily about northeastern Colorado right now. But California would some, if only by virtue of the fact that it’s evaporating and it’s sort of, if the Pacific Ocean is making its way to Colorado, California is sort of in the way. And there was a cool study that was done years ago - they looked at the Colorado River and how the moisture that arises from much of the irrigation and the lower watershed of the Colorado River, which is sort of this mass of canals and irrigation. A lot of that moisture then transports, or some of it, transports back up to the headwaters of the Colorado River. So there’s this circularity in the water cycle for the Colorado River to a certain degree, not completely by any means, but to a certain degree.

Alpha: And what about Utah? Is there a lot of evaporation from Utah that ends up in Colorado

Pat: But Utah is a pretty dry place, as you know. So there’s some evaporation from some of the bodies of water and also from some of the higher altitude mountainous areas with forests and so forth. And that’s true of the entire sort of quote unquote, desert southwest. Is there are still lots of mountains, lots of forests at higher altitudes, and those end up kind of showing up pretty clearly as sources of moisture. They’re not dominant by any means, but they do represent sources of moisture. When tracing moisture cycling remember that for a given location, in Northeastern Colorado, Boston, wherever, Oregon, you could draw a line of where this is the moisture coming from, but all those places are also contributing elsewhere.

So it’s not a one to one relationship. You have some moisture is arising in Boston, and it’s going to travel elsewhere. Some fraction will go to a particular place, and maybe you care about that place, but we can’t forget that it’s also contributing to lots of places. So the diffuse character of this quantity makes it a little bit trickier in some ways than say a watershed where there is a more of a one to one relationship.

There was some fantastic work that really dug into the archetypes of landscapes and how they partition evaporation precipitation and runoff as a way to sort of way to understand that water challenges are going to manifest in wildly different ways depending on the kind of which archetype you’re in. If you are in a system where actually you’re dominated by runoff versus evaporation, you’re going to have a different set of challenges for the most part than a place that’s dominated by evaporation with very little runoff.

There was a really cool paper that was based on CESM isotope-based water tracking, a series of papers, Harrington et al. I want to say, that used the isotope-enabled version of the Community Earth System Model that’s developed primarily out of NCAR and Boulder, the National Center for Atmospheric Research. And this isotope-enabled version allows essentially online water tracking while the model is running. They can sort of track the moisture in different ways. And so there was some cool work that looked at North America and parceled it off into these different segments and looked at sort of the exchange of moisture among those segments, as well as disaggregating it from evaporation, interception, and transpiration to really tease out, well, what flux part of the evaporative flux is actually connected, connecting these two places that are transpiration dominated, which tells you something about the importance of land use.

Alpha: There’s seven states in the US that depend on the Colorado river water for their water.It’s a huge problem because it looks like we’re draining the Colorado River, and there won’t be enough water in two decades or three decades. And it’s, officials are at a loss of what to do. So, my question is like, can we restore some more of the rain in the precipitation shed to kind of increase the Colorado River?

Pat: This is such a tricky question. I would say that that level of intervention would presume a way better understanding of the system than we actually have. And by that, I mean, you know, we’re just starting to, I feel like we’re just starting to get a handle on a sense of the variability, etc., associated with some of these kind of the flows of moisture. Atmospheric rivers as a research topic is not that old. Now, I mean, to some people, you’d be like, oh, it’s been around for decades.

And it’s like, that’s still not that old. And that’s a critical component for understanding the major sort of sources, the major events that inject moisture into parts of the Colorado River basin, if not, you know, parts of basins around the world. And so that’s one part. Another part is the fact that a major part is that we now have a moving target with climate change. So almost all of the phenomena that we’re talking about from an atmospheric science perspective that are going to matter for moisture cycling, changes in humidity, changes in prevailing wind pattern, storm tracks, etc., changes in temperature gradients, the fact that the land is drying out more quickly in the ocean, all this stuff is happening and matters for understanding moisture cycling. And depending on the decisions that society makes around its carbon, we could either be a lot warmer or a little warmer. And I would say we’re just now starting to get good comprehensive studies on climate change, the way that different climate change scenarios will have different types of moisture recycling.

Alpha: You have looked at mega cities and how much they can restore their water systems and rain.

Pat: That was something I did during my PhD. In a paper we tried to figure out, is there a way to talk about, in a way like the way we talk about the vulnerability of municipal water supplies, for these mega cities that could arise from the rate of land use change, the amount of land use change in their sort of upwind source areas and their precipitation sheds.

Some cities are pretty resistant to upwind effects in part because they’re coming from the ocean for the most part. Their sources are coming from the ocean. So like humans can only really affect that through global climate change for the most part.

But some places are intensely reliant on terrestrial sources of moisture wehre those terrestrial sources are experiencing pretty dramatic types of land use change. So there are places on the world that could be ppretty vulnerable. There are mega cities whose domestic water, municipal water supply are pretty exposed to upwind change. If I was in one of those highly vulnerable cities, and I was in charge of water, I would probably say, oh gosh, I should make sure I’m aware of this and thinking about this and maybe do our own studies, right?

Alpha: So this is where the land use in the surrounding area upwind, like if you cut down the trees, will affect the rain in that city downwind.

Pat: The amount of how much it affects, how it affects is all, it’s so variable in the sense that it depends on where you are on the planet. It depends on when you get your precipitation. It depends on what is your municipal water storage system.

So that’s something we actually considered in that mega city paper was on a city by city basis, we sort of looked into, well, how robust is their kind of municipal infrastructure for storing, transporting the water for their city? Is it a run of pipe that they’re just sticking a pipe in the river? And it’s like, if the river’s low, they’re low? Or do they have the good work of reservoirs?

Alpha: So which were the major cities you found that the rain did depend on the surrounding area the most?

Pat: The four cities were Karachi, Shanghai, Wuhan, and ChongQing. And so those four cities stood out as being particularly vulnerable across all of the different metrics.

It’s not a surprise to me in part because there is a lot of land use change across Asia. And part that’s part of the analysis is what’s the rate of land use change in some of these places. On that side of the Eurasian continent, the terrestrial sources are very high.

On governance

The FAO, the UN Food Agricultural Orginizaton has a strong interest in this, they’re producing a report as we speak about the benefits of forests to agriculture, and a chapter on that in that report is looking at the kind of say the climate side and a big part of that is thinking about moisture cycling.

That’s a really good example of a pretty high level governance institution that is interested in this topic. I should mention that the one of the funders for Kat’s (Katherine Humphries) work I mentioned earlier. She had done this moisture cycling analysis for northeastern Colorado, for a very extreme year in 2023 where we had the record breaking precipitation events. And so the Colorado Water Conservation Board, a state level agency wanted to understand more about that that extreme year and partially funded Kat’s thesis. And so one of the deliverables for that thesis was essentially, you know, where did that extreme rain come from. How can we understand that extreme rain in the context of, and it was all rain I should say or it was, you know, rain and hail.

So that’s another example of an institution that I think became aware of the possibility to ask this kind of question, in part because one of the faculty in the Department of Atmospheric Science at Colorado State. His name is Russ Schumacher. He’s also the state climatologist. So he is having very much on the ground discussions with producers or like agricultural producers in Colorado about Colorado’s climate. And he’s engaged with policymakers at the state level, talking about Colorado’s climate, not just climate change but you know climate, you know variability, etc.

Agriculture is a huge part of Colorado’s economy, especially some local economies. And so putting that so this is something that he I think he shared this with that agency and they said, oh wow, should be interesting to understand. So I think you’re right that there’s a certain amount of if you can share this, the fact that there is this kind of scientific possibility to understand this phenomena a little bit more broadly.

Ecosystem service

Alpha: You’ve been doing work to frame vegetation generating rain as an ecosystem service.

Pat: One of the papers in my PhD was asking this question, sort of can we frame moisture cycling as an ecosystem service and if so what does that look like what would that mean how would we do that. And it’s good you mentioned Lan Wang-Erlandsson because as part of her PhD she had developed this evaporation model that simulated evaporation partitioning at the land surface. So evaporation is moisture turning from liquid phase to gas phase, but there’s lots of different ways that can happen. If it water can fall on say a leaf that’s called interception and if it re evaporates from the surface of that leaf that’s been intercepted and then re evaporated. If water falls to the soil and gets taken up by the tissues of the plant and then evaporated up a still motto that’s called transpiration. It functions differently you can sort of so you can simulate that so you can if you have land use data soil data precipitation climate data, etc.

I think it was really useful providing kind of a first order estimate, a conservative estimate for the effect of vegetation on moisture recycling. If you wanted to get more detailed you’d use a dynamic model like an earth system model with different land surfaces. Then you could get at a lot more of the dynamic processes, you know, changes in that diurnal cycle changes in seasonality.

And so another scientist, Becky Chaplin Kramer, who has led a ton of ecosystem service work, she invited me to contribute sort of this data and a little bit more analysis to some work where she was trying to combine multiple index of critical natural assets around the planet with moisture cycling being one of those sort of critical natural assets ecosystem services. And so that idea has gotten a little bit more traction and is still sort of ricocheting around. It’s probably what has motivated the FAO to be more interested.

Social-economics of rain

Alpha: Cool. Yeah, I think ecosystem services framework helps certain organizations, and governmental groups too… And then you and Lan also did some work on social ecological modeling?

Pat: We wanted to try and do this idea of how land use can affect precipitation in a different place, and Lan and I wanted to see if there’s a back loop. Is there anything that connects the place that’s receiving precipitation back to that upwind source region? To really investigate that we wanted to think about sort of social dynamics, economic dynamics, political dynamics. And when you start using that language in the context of an ecosystem service, you bump right into this concept of social ecological systems, SES, which are a way to study coupled human and natural environments. It draws a lot from the complexity science community, thinking about how there are feedbacks that exist within these systems that lead to emergent phenomena, all sorts of stuff. If we think about moisture cycling in the context of a social ecological system, then the moisture cycling side is sort of part of the kind of ecological connection, a main feedback in some ways that ecosystems upwind are connected to the ecosystems downwind via the atmospheric water cycle.

We did a deep dive into a couple of case studies like in Bolivia, Niger and Mongolia.

What we tried to do is we said let’s map the precipitationsheds for these locations. And that gives us the boundary in which to sort of consider the spatial scope of these social connections, economic connections, policy connections. And this was really an exploratory paper in some ways that was an attempt to sort of open up this conversation that was already, there were already other kind of spokes into the conversation, but from different communities. So there’s a couple other communities, one’s called sociohydrology and one’s called hydrosociology (they sound the same, but they’re different).

I’d say there’s still a ton to do there. Lan has a PhD student who’s working on this still that’s really starting to dig into some of these social dynamics. I’ve got a couple of grant proposals that have been submitted to try and dig into this phenomenon more in part because if there are, if some places do have much stronger social kind of back loops to their upwind areas. Those are levers of change, right. So those that those are ways that those places are potentially tied into affecting their own precipitation, albeit through totally different mechanisms, policy mechanisms, economic mechanisms, trade mechanisms. I’m really excited about that work. I think there’s a ton left to do so many questions and almost all of them rely on, aside from funding, but rely on really deep interdisciplinary work to understand those systems, which me sort of waiting into initially is good for generating an initial question or set of questions, but beyond that, you really have to start working with experts in their respective disciplines.

Alpha: Could you give an example what you mean by the social back loop?

Pat: Let’s say there is a patch of land upwind that is a mosaic of forest and range lands and croplands. It evaporates water, which falls down, downwind to a city, let’s say Montevideo, in Uruguay. Well does Uruguay buy product from that area upwind? Is its economy locally dependent in any way on the products generated upwind? Is its economic activity would be promoting or discouraging certain land use decisions which are then affecting it.

Alpha: Oh, wow.

Pat: Trying to disentangle that question is complex. A lot of different ways of thinking about the connectivity. There’s network science from there. There’s economics in there. There’s policy sciences in there. Institutional science is even like history involves. And so that’s why it’s a really it’s not an easy question to ask in some ways.

The biological side is simple by comparison, right? We take this grid-ed climate data. We ask this question. We answer it. We write a paper. But then we want to talk about what are the connections that are poorly documented, which do not fit any sort of grid structure. They don’t follow physical laws. How do we study that question to then connect it back?

A dream scenario would be to build a cool simulator to say this is how we could simulate change in an upwind area and its effects downwind. But if you think it’s actually a social ecological system, some sort of complex adaptive system with feedbacks, then you have to be able to do that. You have to be able to have the other part of that connection. Otherwise, it’s like only it’s like half of a simulator, right? Like you’re only simulating half of the system, not simulating all of the other stuff. And if there are some really important slow or fast feedbacks, reinforcing feedbacks, especially you could get some really surprising outcomes.

Alpha: Yeah, that’s good. So yeah, so it’s kind of cool how you’re bridging the people part with the ecological part. Usually people decide to study one or the other, right?

Economists, they treat nature almost as a separate physical process, but economics really is a subset of nature because people are subset of nature.

Pat: You’re going to need a whole other podcast series for that one.

Alpha: It’s interesting that you’re using a complexity theory lens to write so a system and right and you actually have a fondness for looking at things from a systems perspective, right?

Pat: I don’t do a ton of work through that lens but I think actually most of my work is implicitly through a systems lens.

I got my PhD at the Stockholm Resilience Center resilience. And that institute has a deep connection to something called systems ecology, which really came out of systems thinking complexity, complexity science. And so a lot of my academic training, especially my formative PhD training was infused with that sort of lens that systems thinking lens. I actually taught a class on systems thinking, sort of a one shot systems thinking course at CSU, which was a ton of fun to teach. It was such a cool class to teach really asking questions, asking these undergrads to think deeply about sort of the systems that were embedded in what kinds of leverage points exist, etc. We use a book called thinking and systems that was written by Donella Meadows.

Alpha: In economics you have emergence like the invisible hand. So it’s interesting when you’re trying to tie ecosystems with the sociology and then seeing what emergent things arise, and seeing what complexity arises. You change the rules a little bit and you get really different emergences. Maybe you just change a little bit how the ecosystem connects to the sociology. You get very different behavior, maybe more favorable behavior.

Pat: I think almost all the ingredients are out there scattered or different disciplines. I think a really strong big opportunity is some of the advances in, I would say, like complex network science is probably a really good entry point for starting to wrap our heads around some of the social processes. So you could think about networks, social networks, political networks, economic networks, and from those networks, you can actually distill almost rules or kind of governing principles that make that network work, mathematical rules, I should say. And that’s what would permit you to start to develop something like a simulator is if you had, you could translate what you observe in the data in the networks that you find into something that can be represented in numbers. And that’s how then you can really connect that into some sort of simulation. And so there’s a ton of work on complex networks. I mean, that’s a whole massive field with sub fields. And there’s even been some work on complex networks related to moisture cycling to distill the moisture tracking findings into a complex network and then use that network to then ask and answer questions. And then the people have done similar things for people and it’s really just a matter of like, which networks do we need to develop and understand and sort of glue together to make the sort of representation of something that we can simulate and explore change and. So I mean, it’s not for I don’t think it’s for a lack of data per se. It’s a lack of essentially finding the right people to work together to connect the dots that are already there.

Alpha: Yeah, that’s really interesting. The social system is a network and the moisture recycling is a network. You can think about each tree as a node in the water network where the tree decides whether to transpire water up or not, whether to bring water from the groundwater. Basically you’re moving water between these nodes.

Pat: The other thing that I’m really interested in is exploring how ecosystem stress, say from drought can propagate through moisture recycling to affect other places.

So if you’re in Gabon in in Africa, it gets a lot of moisture from the ocean, but also from East and Central Africa, from Kenya and from the Congo Basin. If you’re in Gabon, your precipitation sensitive to the evaporative stress in East Africa. Are you seeing a signal in your variability or seasonality, the actual magnitude of the amount of water that you’re getting? Are you seeing any sort of signature signal of evaporative stress or changes in evaporative stress as a result of that being transmitted through moisture cycling? And the reason I’m interested in that is in part it’s getting at a different aspect of sort of the kind of the complex and the kind of network connectivity of these ecosystems to one another.

I want to understand the teleconnected aspect over land mediated by the ecosystems in multiple ways. This is motivated in part because then it permits talking about the dependence of one place on the governance of another, where you can say this place is actually dependent in some ways on the way this place over here chooses to govern its land. I’ve done a little bit of work on governance of moisture cycling, and this is another way to sort of continue deepening that work through a slightly different lens, not just saying hey these places exchange moisture with one another which is interesting in itself, but saying this place is actually somewhat dependent or sensitive to exposed to the policy decisions in this place in this specific measurable way.

Alpha: Right, yeah. So the ecological stress in one location affects another location, then you would be interested in perhaps helping that other place have less ecological stress.

Pat: In my opinion it’s honestly a route to cooperation right. It’s also something that would lend itself more to sort of trans boundary connections trans boundary cooperation. It’s rare that you would just have two countries next to each other. Canada and the United States are an exception of two giant countries that are next to each other with few other countries sort of involved in their moisture cycling. Most countries at the total mess. And so as a result you have to think about these sort of like consortiums of countries with transboundary relationships.

Alpha: And this opens the door to bring in negotiation and game theory.

Pat: All sorts of other dimensions for sure.

Tipping points and planetary boundaries

Pat: Tipping points is an idea that’s been around for ages. And that idea has been incorporated into the planetary boundaries framing. The planetary boundaries framing is this suggestion that there are specific thresholds within the Earth system that to cross those thresholds would begin the transition to a new Earth system system.

Alpha: Moisture recycling could play into the planetary boundary.

Pat: In the initial framing of the planetary boundaries it was based on surface water and thresholds in surface water related to environmental flows - the flows that are necessary for the ecosystems in a particular river to be sustained and to last and be resistant to change. That was adjusted in the last decade to include quote unquote green water, to look at the evaporative side, the atmospheric side of water, thinking about all the landscapes that are not really where runoff is pretty marginal and where it’s much more about precipitation and the evaporation and really that exchange. So there is now a green water planetary boundary, essentially that other half of the water cycle dominated by precipitation evaporation versus precipitation runoff. And that green water boundary has attempted to fold moisture recycling. I’m a co-author on a green water planetary boundary paper. I will say that the planetary boundaries are still a really evolving concept and I think even the people that are in on the inside would acknowledge that that, you know, every year, there’s new insight about what the details of this or that planetary boundary are.

Alpha: Did you have any final thing you might want to say?

Pat: I think one thing that has guided my research, for moisture cycling especially but I would say it’s true across the board, and is to find the questions that are really interesting to me personally. And then in some ways chasing them even if some of the people that are around me are less excited. I think if I can leave you with one thing something that would be valuable in my view is if you’re excited about chasing something keep chasing it you know because I think that there’s so many more questions out there than we realize to even that we haven’t even realized we should be asking them. I think we have the sense that we’ve discovered everything right that every rock has been turned over scraped clean that there’s nothing left to do and that’s like hilariously not true. Especially in this thorny challenging area of thinking about the intersection of anything physical natural earth system ecosystem hydrologically related and people we still think that we’ve scraped the rock clean we haven’t.

If you’re interested and curious and excited about something keep chasing it even if you have to put it on like not even the back burner like the warming section of your of your stove top that’s like barely keeping it warm. Don’t lose it, right. I’ve had to do that multiple times in my career where I have to set something aside to work on something else for whatever reason but don’t forget that that’s there because that could be the biggest thing that you contribute to like our understanding of the world.

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References

Keys, Patrick W., R. J. Van der Ent, Line J. Gordon, Holger Hoff, R. Nikoli, and H. H. G. Savenije. "Analyzing precipitationsheds to understand the vulnerability of rainfall dependent regions." Biogeosciences 9, no. 2 (2012): 733-746.

Keys, Patrick W., and Lan Wang-Erlandsson. "On the social dynamics of moisture recycling." Earth System Dynamics 9, no. 2 (2018): 829-847.

Keys, Patrick W., E. A. Barnes, R. J. Van Der Ent, and Line J. Gordon. "Variability of moisture recycling using a precipitationshed framework." Hydrology and Earth System Sciences 18, no. 10 (2014): 3937-3950.

Wang-Erlandsson, Lan, Ruud van der Ent, Arie Staal, Miina Porkka, Arne Tobian, Sofie te Wierik, Ingo Fetzer et al. Towards a green water planetary boundary. No. EGU21-13583. Copernicus Meetings, 2021.

[Van Gogh painting]

It’s a blessing to have a newsletter that explores the many dimensions of water and its multiple connections to ecology and climate, while engaging with an audience. Thank you for your readership, comments, feedback, and help spreading the word. I am happy that many of you have found it to be an enlightening read. I am gratified that the newsletter seems to be making an impact on many different sectors based on many conversations I have been having.

I began writing in the latter part of 2021, having come from a permaculture and physics background, and while organizing a water networking and education group. I’ve interviewed practitioners and scientists from various areas of the water field, exploring many aspects of the water cycle and how it integrates with ecosystems and climate. One of the key themes throughout has been that we can restore the water cycle, and that this has many positive implications for our planet. I’ve read hundreds of scientific papers in the process of seeking to develop a more comprehensive understanding of water, and I’ve distilled the key findings into the essays featured here. This year, I dove further into academia and have been working to better integrate practitioners and academics.

2025 opened with huge fires in LA, which deeply resonated with me as I had lived there for many years. The recurring fires in California during the 2010s and 2020s were what initially got me into this water field, as I wondered how permaculture solutions might work for the fires. I also wondered why no one seemed to talk about restoring water to the land, instead focusing primarily on fuel reduction by cutting down vegetation. Because Didi Pershouse and Walter Jehne had launched Rehydrate California project a while back, I contacted Didi to do a second podcast together as a dialog - “Lessening LA wildfires: The water solution”. I further explored ideas of restoring the water cycle to lessen wildfires “Taming the hot dry winds that cause wildfires; sponging up freak storms”.

I looked at harmful algae blooms, discussing the work of John Todd, who had pioneered using plants and microbes to clean up lakes and rivers. He facilitated the restoration of the lake’s natural microbiome, which then in turn cleaned up lake toxicity and algae blooms (amazing that these tiny creatures we often forget about are so powerful) : “Bringing our lakes and oceans back to life: how to deal with algae blooms and polluted waters”. This was my first article writing it as a dialog between different people. People seem to enjoy the dialog format.

[Australian aborigine painting of water holes and groundwater]

It was a year of bringing more and more focus to groundwater and exploring various hypothesis of its importance in how it connects with the rest of the water cycle and with the carbon cycle - “The dance of vegetation and groundwater”, “Green water, blue water, silvergreen water, silverblue water”, and “The unsung linchpin : groundwater helps stabilize the climate”. After those articles, I had an interview with John Cherry, a groundwater pioneer, whose groundwater textbook trained a generation of hydrologists. The interview rocked me, and oriented me even more to the importance of groundwater. Here it is in a two part series “The big groundwater crisis - food, water, pollution, and social unrest” and “Groundwater & climate crisis solutions: regenerative ag, rainwater harvesting and interdisciplinary collaborations”. His calculations show 70% of our food depends on groundwater, which makes the widespread depletion of groundwater a major issue we need to be talking about a lot more. It was nice that he was appreciative of all my efforts to build conceptual bridges between groundwater and other aspects of the earth system.

I had a chance to view first hand a river restoration project and and see the salmon in the wild (so cool to see them wiggling thru the water) - “Rivers of land and sky: project restoration”, which also made me ponder analogies to the restoration of atmospheric rivers.

I talked to a lot of interesting people this year. One was Douglas Sheil, who is an ecologist with a hydrological bent : “The forest-water connection”. Our interview became the most downloaded Climate Water Project podcast on this channel.

Stuart Andrews, son of Peter Andrews who had founded Natural Sequence Farming in Australia, a water restoration based approach to farming and land management, came on to discuss the philosophy and techniques of the approach, as well as on carrying on his dad’s legacy - “Natural Sequence Farming”.

I had the honor of interviewing hydrologist Ruud van der Ent. A previous article I had written on his work “Map of the small water cycle”, about precipitation recycling, was one of the most read articles in this newsletter. Our interview : “Making the map of the small water cycle”. Kind of like how after a movie, there is also the making of the movie interview.

I also talked with van der Ent’s scientist colleague, Lan Wang-Erlandsson, who was working on planetary boundaries and the importance of moisture-recycling/small-water-cycle to the planet : “The planetary boundaries of green water”.

The planetary boundaries are a type of negative tipping point. There are also positive tipping points. I had a meeting with eco-oriented folk in October where we discussed building a map of how to ‘nudge’ the global water cycle to positive tipping points.

Hydrologist Sieger Burger and I discussed many aspects of the water cycle in a fun dialog : Plants drink water from the air.

Charlotte Qin paints powerful water paintings and does reciprocal performances where the audience engages in a connection with water. I love performances where the artists gets the audience to participate. As an artist myself I was really happy to chat with her: “The art of water”.

[from Charlotte Qin’s reciprocal performance piece about glaciers melting]

United States Geological Survey’s (USGS) scientist, Laura Norman has been a key person in bridging academia and practitioners. She has worked to quantify how much slowing water impacts the hydrological cycle and ecosystem: “Putting rocks in rivers to lessen drought, fire & flood”

Producer Paul O’Callaghan came on to discuss his movie which looked at many groups from around the world working to restore the water cycle in their country: “Our blue planet”.

The Climate Water Project takes a lot of work to produce. Just like water feedback loops are key to running the global water cycle, the feedback loop of paid subscribers and me writing/interviewing has been an important one in running and growing the Climate Water Project newsletter and podcast. If you have found reading these articles and listening to the podcasts valuable please consider becoming a paid subscriber.

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Here are some research problems in water to help bridge academia and the world of practitioners : “A research program for hydrology”. Here are some more interesting questions “A more exciting set of unsolved problems of hydrology”

I asked Ali Bin Shahid if he might be able to calculate the biotic pump effect, and that got us engaged with looking at the problem, and seeing if we might be able to contribute further to its understanding. I wrote The Mystery of the Biotic Pump that rotated the wrong way, and he wrote some articles too.

A different paradigm was posited in “Is the earth microbiome regulating the climate?”, an article which a lot of people liked. One of the way science advances is by positing bold hypothesis, and then going about testing them. This was my boldest hypothesis of the year.

I wrote about viewing the earth as a coupled system “The coupled planet: how forests, groundwater, rain, & climate shape each other. A complex systems approach”, and thru a group theory approach “The algebra of the earth that reveals its multifunctional genius”

The Water Ecology Principles , a distillation of the many aspects of the eco-hydro-climatological system, was a hit with quite a few people.

A more philosphical essay “On the nature of water and its stewardship”, that came during a time I was reading about critical philosophers like Foucault.

I peered at rain moving around the world and noticed something curious. I wrote about it in “An intriguing behavior of global rain”.

And the most popular article this year, based on the question a lot of people were asking was “How much land do we have to restore to bring back the rain?”. In it, I distilled the research of a lot of different scientists, and observations of many on this topic. One of the most enlightening research studies (which most people don’t know about) was done by atmospheric scientists Ronny Meier and company, who tracked 7x11km neighboring cells in Europe that differed by more than 20% vegetation, and found that more vegetation meant noticeably more rain, which indicates eco-restoration on the range of 7x11km range of in climates like Europe could impact rain.

.Two years ago Nick Steiner, of Water Stories, and I discussed how we didn’t really see anyone much on social media discussing restoring the water cycle, but felt the world was about to wake up to this soon. Then last year we saw an explosion of interest as a lot of people started talking about these issues. The small water cycle and precipitation recycling became a topic of interest, as well as many other aspects like rain infiltration, slow water, the drought-fire-flood cycle, bioaerosols, and the soil sponge.

This year I saw a lot of leaders in different sectors like insurance, governance, banking, and philantropy began to get curious about topics like how we might restore water cycles to help ensure the future of our planet, and what role they might play to help. There is momentum building. I sense we are going to phase transition to another stage. 2026 is going to be an exciting one!

Top viewed posts this year

1. How much land do we have to restore to bring back the rain?

2. The big groundwater crisis - food, water, pollution, and social unrest : John Cherry interview Part I

3. Lessening LA wildfires : The water solution - A dialog with Didi Pershouse

4. Is the earth microbiome regulating our climate?

5. Green water, blue water, silvergreen water, silverblue water

6. Water ecology principles

Top downloaded podcast : The forest-water connection : ecologist Douglas Sheil

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Appendix:

To try and figure out how some metrics for the water cycle restoration movement, I looked at google trends:

This shows amount of people in the US, googling “Does deforestation cause drought” each month.

The idea of multifunctionality is a wonderful concept. Its key to understanding how a system functions integrally.

A tree has many different roles. For instance, it plays a role in both the carbon cycle and the water cycle. It breathes in carbon dioxide, turns it into complex carbohydrates, and then it decays and that carbon gets used in soil. It also takes in water, uses water in photosynthesis which helps with making the complex carbohydrates, it transpires water, which plays a role in clouds, transpiration cooling, greenhouse gas, and it pushes down water during wet season and draws it up during dry season.

Each of these roles supports the others. The carbon the tree captures gets built into biomass using water. That biomass becomes leaves that shade the soil, keeping it moist. The moist soil hosts bacteria that help the tree access nutrients. The tree’s transpiration helps create the rain that refills the soil moisture. It’s a web where every function makes every other function work better.

A floodplain likewise plays many roles. It slows water, where the soil and plants can cleanse the water. That water can filter down into aquifers, which can be brought up by trees during dry season to hydrate the landscape. It creates wetlands which support insects and fish. And here again, each role reinforces the others: the cleaner water creates better habitat, the insects support the plants that slow the next flood, the recharged aquifer keeps the system resilient through droughts.

Soil is likewise multifunctional. It’s a sponge for rainwater, a filter for toxins, a habitat for rich microbial and insect life, a pharmacy for antibiotics, a nutrient provider for plants. The microbes create the sponge structure, the sponge structure enables the filtration, the filtration protects the microbes. Each function depends on and strengthens the others.

Permaculture has made multifunctionality one of its key tenets. It looks for solutions that have multiple purposes, e.g., placing logs or branches in the landscape in a process called hugelkultur, a process which can work to slow water and which also decays over a long time, providing a habitat for fungi and decomposing to provide carbon to enrich the soil. One intervention, multiple benefits, each benefit supporting the next.

This kind of design, where one element does many jobs and the jobs reinforce each other, seems to be nature’s signature approach. It’s how healthy systems work. And increasingly, it’s how the most successful ecological restoration works. When you restore a degraded landscape by reintroducing the right elements, trees, soil bacteria, water flows, you’re not just fixing one problem. You’re restoring multifunctionality, and that multifunctionality creates cascading benefits that spread through the system.

Rewilding efforts demonstrate multifunctionality. When wolves were reintroduced to Yellowstone, they reduced deer populations that had been overgrazing young trees. With more trees able to grow, beavers had the materials to build natural dams. Those dams created wetlands that recharged aquifers and changed the course of rivers, providing more water for the whole forest system. The wolves weren’t just controlling deer, they were part of a chain of operations affecting trees, water, soil, and the entire landscape. These animals and plants are playing multiple roles in the functioning of the Earth system.

Which raises an interesting question: is there a way to develop a more formal language for this multifunctionality? Is there a way to mathematicize it so we can understand it more precisely, predict it, and design with it intentionally?

The reason a mathematical framework is helpful isn’t necessarily just academic. It’s that our minds have trouble tracking multiple simultaneous effects. We can easily think “the tree captures carbon” or “the tree moves water.” But thinking about how the tree simultaneously affects carbon AND water AND soil AND climate, with each effect influencing the others, that’s much harder to hold in your head.

And when we can’t see all the connections at once, we make decisions as if they don’t exist. We need a way to see the whole web of effects at once.

Mathematics gives us that. Not because math is better than intuition, but because it forces us to write everything down. It makes the invisible visible. And once you can see all the connections on paper, you can start to design solutions that work with them instead of against them.

Representing more formally

Here’s one way to think about it. First, we need to represent the state of a system. I’ll start with a simplified example.

Imagine we want to track the carbon cycle. We could break it into components: the carbon dioxide in the air, the carbon in trees, and the carbon in the soil. Let’s call these three components our “carbon values.” Similarly, for the water cycle, we might track: water in the air, water in trees, water in soil, and water in underground aquifers. These are our “water values.”

Now imagine a row of mail slots in an office. In the first slot, we put the current amount of atmospheric carbon. In the second slot, the carbon in trees. In the third, the carbon in soil. In the fourth slot, water in the air. Fifth slot, water in trees. Sixth, water in soil. Seventh, water in aquifers.

This row of slots with all their values, that’s what mathematicians call a vector. It’s just a way of representing the state of a system at any given moment. All the important values, lined up so you can see them at once.

Now think about what happens when a tree grows. It doesn’t just change one slot, it changes multiple slots at once.

The tree pulls carbon dioxide from the air, so the atmospheric carbon slot decreases. The carbon in the tree slot increases as it builds biomass. When leaves fall and decay, the soil carbon slot increases. At the same time, during dry season, the tree draws water up from the aquifer and soil, so those slots decrease while the tree water slot increases. Then the tree transpires, so the atmospheric water slot increases.

The tree is operating on the entire row of slots simultaneously. It’s transforming the whole state of the system.

We can represent this transformation as a set of rules, what mathematicians call a matrix. The matrix is just a systematic way of writing down: “When a tree acts on the system, here’s what happens to each slot.” It’s the recipe for how the tree transforms the state.

This might seem like a complicated way to describe something simple. But here’s why it’s powerful: once you write it down this way, you can see something crucial. The tree doesn’t just affect carbon and water separately. It couples them together. You can’t change the carbon slots without changing the water slots, because photosynthesis uses both. You can’t change the water slots without changing the carbon slots, because the tree needs its carbon-built structure to move water.

The mathematical framework makes this coupling visible. It shows you that the carbon cycle and water cycle aren’t separate systems. They’re interlocked, and the tree is the mechanism that interlocks them.

We can see this coupling principle at work in other contexts too. Consider what happens when you slow water using earthworks like swales or check dams. Fast water rushing across the landscape operates primarily on the water slots in our vector: it moves water from soil to rivers to ocean, but it leaves the system before much else can happen. But when you slow that water down, the operation changes. Now the slow-water matrix operates on both water and carbon slots simultaneously. The water has time to infiltrate, so the soil water slot increases. That water is now available for plants and soil microbes to use in photosynthesis and biological processes, so the tree carbon slot and soil carbon slot increase. The slow water is enabling the coupling between water and carbon that fast water prevents. It’s creating the conditions for the two cycles to work together. This is matrix formulation makes these couplings explicit. You can see that the slow-water operation isn’t just moving water around, it’s changing how water and carbon interact with each other.

Now we can use this same framework to look at human interventions. Let’s take desalinization and aqueducts as an example.

Usually, we think about these technologies only in terms of water. Desalination takes ocean water and produces fresh water. Aqueducts move that water to where it’s needed. We consider them as operating only on the water cycle.

But that’s not the full picture. Desalinization requires enormous amounts of energy. That energy comes from burning fuel, which means releasing carbon into the atmosphere. Aqueducts require massive pumps running continuously to move water uphill over mountain ranges. In California, 20% of the state’s energy goes to cleaning and moving water around. That’s a lot of carbon emissions. Those emissions can lead to global warming, which in turn causes more droughts in some areas.

So when we write down what desalinization actually does to our system, when we look at all the slots, not just the water ones, we see it’s also increasing the atmospheric carbon slot. It’s operating on both the water cycle and the carbon cycle simultaneously.

This is what we mean by looking at the “full vector space” that a solution operates on. Instead of only asking “what does this do to water?” we ask “what does this do to water and carbon and energy?” We’re forced to see the whole transformation, not just the part we’re focused on.

But there’s something even more important the mathematical framework reveals: ripple effects through time.

Let’s say we extract groundwater. That decreases the aquifer slot in our system state. Now we have a new state, one where the aquifer is lower.

When the tree operates on this new state, something different happens. There’s not enough water for the tree to draw up during dry season, so the tree water slot stays lower. The tree becomes stressed.

Now lightning strikes, something that happens naturally all the time. Lightning might hit dry grass or a dead branch, starting a fire that spreads through the landscape. When fire encounters a healthy, well-hydrated forest, it might burn slowly as a small fire that clears underbrush. But when fire encounters stressed, dried-out trees in a degraded landscape, you get a major conflagration. The fire operation now decreases the tree carbon slot dramatically as the forest burns.

We can keep tracing forward: each operation creates a new state, and that new state determines what the next operation will do. This is what we mean by a chain of operations. The groundwater extraction operation acts on the original state. The tree operation acts on that result. The lightning operation acts on that result. The fire operation acts on that result. Each operation in the sequence acts on the state created by the previous operation. This is how ripple effects propagate through a system.

The mathematical framework can help clarify: one might think groundwater extraction only affects the water cycle. But when you trace through the chain of operations, you see it ultimately affects the carbon cycle too. The connections aren’t always direct, but they’re there, and the math helps you trace them.

The Deep Structure: Groups and Ripple Effects

These operations, tree, bacteria, rain, fire, lightning, they don’t just act in sequences. They have relationships with each other. They form what mathematicians call a group structure.

To understand what a group is, think about the seasonal water cycle. In wet season, rain pushes water down into the soil and aquifers. In dry season, trees pull that water back up from the aquifers and release it into the air through transpiration. The wet season operation and the dry season operation are inverses of each other, they undo what the other does. If you go through four seasons (wet, dry, wet, dry), the water has cycled through the system and returned to a similar state as where it began. These seasonal transformations, the set of operations that cycle the water through the system, form a group.

Different ecosystems have different group structures. A tropical rainforest has different seasonal water operations than a desert. A forest that burns every 50 years has a different fire-succession group than grassland that burns every 3 years. The structure of possible transformations is different.

Now, the operations in an ecosystem also form a group structure. But instead of being just about cycles that return to the same state, it’s about the structure of how transformations can combine and propagate.

When you combine bacteria operation with tree operation, you get soil-building. When you combine tree operation with rain operation, you get hydraulic redistribution. These combinations follow rules. Some operations can be reversed: deforestation undoes what forest-building does. Some operations, when combined in different orders, lead to the same final state. Some operations amplify each other, some cancel each other out.

The group structure captures all of these relationships. It’s the deep mathematical pattern underlying how these operations relate to each other.

And here’s why the group structure matters for understanding Earth systems: it tells you how far ripples can spread.

When you cut down a forest in one watershed, you’re applying a deforestation operation. That operation can combine with a drought operation (less water because no trees to cycle it). The drought operation can combine with a fire operation (dry landscape burns). The fire operation can combine with an erosion operation (nothing holding soil). The erosion operation can combine with a sedimentation operation (rivers clog with soil). The sedimentation operation affects river temperatures, which affects fish populations, which affects ocean ecosystems.

Each operation creates a state that the next operation acts upon. The effects cascade through the system, potentially spreading across continents and oceans.

The group structure is the mathematical description of all possible cascades. It tells you: given these basic operations (tree, bacteria, rain, fire, drought, etc.), what are all the possible ways they can combine? What are the full set of states you can reach by chaining operations together? How far can a local change propagate through the planetary system?

This is what we mean by “the structure of ripple effects.” The group is the pattern of how transformations propagate through Earth systems, the web of possible consequences.

Understanding this structure helps us see that local actions and planetary processes aren’t separate. They’re connected through chains of operations. A decision about land use in one place combines with climate operations, with ocean operations, with atmospheric operations, cascading across the whole Earth system according to the rules of the group structure.

Here’s what makes the group structure perspective particularly illuminating for geoengineering: it reveals why these interventions so often create problems even when they “work.”

Natural operations form what mathematicians call a closed group. You can combine them (Tree · Bacteria · Rain) and they create states that other natural operations can work with effectively. The operations compose well together. But geoengineering operations often don’t fit cleanly into this structure. Not only do levees create more flooding down stream as it causes rivers to speed up, but a levee blocks floodplains from spreading water across the landscape. This stops the aquifer from being recharged during floods. The levee creates a degraded state with depleted aquifer and poor soil that’s incompatible with what natural operations expect. When rain then falls on this degraded state, it can’t recharge aquifers properly because the floodplain pathway is blocked. When trees operate on this state, they can’t access enough water and become stressed. The natural operators are designed to work with floodplains; remove the floodplain and the whole chain breaks down.

This is why geoengineering solutions often seem to solve one problem while creating several others. They’re introducing operations that don’t compose well with the natural group structure. They create states that make subsequent natural operations (drought, fire, rain) more destructive rather than regenerative. Understanding the group structure helps us see this incompatibility mathematically, rather than discovering it through costly trial and error.

Ecological restoration that works with multifunctionality takes the opposite approach. When you restore a floodplain, you’re not just solving flooding, you’re reintroducing an operation that composes well with the natural group structure. The floodplain operation creates a state (recharged aquifer, enriched soil, thriving biodiversity) that makes subsequent natural operations more effective. Rain on a restored floodplain recharges aquifers. Trees on a restored floodplain access deep water during droughts. The restoration creates beneficial cascades rather than destructive ones. This is why ecological restoration often produces multiple benefits that weren’t explicitly planned for, the restored operations naturally compose with other operations in the system to create healthy states that propagate forward through time.

So I believe these ideas, vectors to represent states, matrices to represent operations, chains to represent ripple effects, and groups to represent the deep structure of how operations relate, give us the beginnings of a way to more formally talk about multifunctionality.

But we can also use these concepts informally, without needing to do the actual mathematics. We can ask: Are we looking at the full state space that a solution operates on? Are we considering all the slots it affects, not just the one we’re focused on? Are we thinking about the chain of operations that will follow? Are we asking how this operation will combine with other operations in the system?

These questions come naturally within this framework. It helps us see that multifunctional solutions aren’t just doing more things. They’re operating in ways that fit the group structure of natural systems. They’re creating states that make subsequent operations more beneficial rather than more destructive. They’re working with the deep patterns of how transformations propagate, rather than against them.

I think these group structure ideas, combined with coupled system concepts (introduced two essays back) and other frameworks from complex systems theory (to be discussed in future issues), can help us develop a more integral and holistic way of understanding the Earth system and how better to restore it.

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I started thinking about these group structure ideas earlier this year, and found out during the summer, when we both published something on it within hours of each other, that Ali Bin Shahid had also been thinking about these group ideas applied to nature and our planetary systems.

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A lot can come out of collaborations between academics, eco-practitioners, and regenerative agriculturists. If you are in academia or engaged in research, here are some water-related issues that could benefit from a more rigorous hydrological and ecological modeling approach.

These problems draw on observations and techniques from practitioners, regenerative farmers, and indigenous water-harvesting traditions. Field experience shows how interventions influence water flow, soil moisture, and vegetation, but we need to test whether these insights hold true and quantify their effects. Using high-resolution models, remote sensing, and other scientific tools can provide clearer guidance on what works, where, and at what scale. More scientific rigor can make it easier to change laws and governance strategies on these issues.

1. Slowing Water to Recharge the Land

Brock Dolman’s catchy slogan, “Slow it, sink it, spread it,” captures the essence of interventions that slow runoff, allow water to sink into the soil, and spread it across the landscape to maximize retention. A critical question is: how much should water be slowed, sunk, and spread to achieve measurable benefits, and what thresholds of intervention trigger ecological and hydrological regime shifts in a bioregion?

Slow water draws on centuries of indigenous and traditional water-harvesting practices, as well as modern permaculture innovations. Techniques include zai pits in the Sahel, half-moons in arid landscapes, swales and keyline designs on hillsides, and terraces, leaky weirs, and infiltration basins on farms. Communities report improved soil moisture, groundwater recharge, streamflow, and vegetation health, yet these effects have rarely been rigorously quantified.

Laura Norman of the United States Geological Survey (USGS) and colleagues [Norman 2020, 2022, 2025] have been pioneers in slow water research, they have shown that strategically placed rocks and leaky weirs can increase late-season streamflow by 20 to 30 percent, directly boosting watershed hydrology. These results demonstrate how modifying physical flow can store water and sustain baseflow, providing a foundation for more resilient ecosystems.

Beyond streams, slow water interventions help landscapes retain wet-season rainfall into the dry season. By storing water in soils, small dams, and aquifers, landscapes maintain higher moisture levels when the rains stop. This retained water supports dry-season evapotranspiration, helps trees and plants access water, sustains local humidity, and can contribute to increased localized convective rainfall through the small water cycle.

The research question is this: Can different slow water techniques, individually and in combination, increase groundwater levels, enhance local precipitation recycling, and sustain plant water availability during dry periods? How much slowing, sinking, and spreading triggers significant regime shifts in watershed hydrology and ecosystem productivity? Addressing this requires hydrological and micrometeorological modeling coupled with field validation to capture how stored water modifies energy partitioning, moisture flux, and atmospheric feedbacks.

A movement around slow water has been promoted by Brock Dolman, Erica Gies, author of Water Always Wins, permaculture, agroecology, and regenerative agriculture. Rigorous research can help quantify exactly how much water should be slowed, sunk, and spread to achieve these benefits at scale.

2. How Do Groundwater Levels Impact Wildfire Risk?

Wildfires are commonly associated with heat waves or short-term rainfall deficits, but long-term groundwater depletion may also play a critical role. NASA remote sensing studies have observed correlations between low soil moisture and increased wildfire incidence [Sazib 2021], indicating that regions with depleted subsurface water can remain flammable even when rainfall is moderate.

The research question is this: To what extent does widespread groundwater extraction drive higher wildfire risk, and how does hydrological drought influence forest fuel dryness? If it is possible, how much do we have to restore our groundwater , via techniques like slow water, rainwater harvesting, and managed aquifer recharge, to lessen wildfire risk signficantly? Integrating water table depth, root-zone soil moisture, and fuel moisture content could help develop predictive models that go beyond conventional atmospheric drought indicators. Understanding this mechanism could pinpoint areas where aquifer and soil restoration would most effectively reduce flammability.

3. Regenerative Agriculture and Aquifer Health

Agriculture contributes heavily to both groundwater depletion and pollution. Regenerative agriculture improves soil structure, builds soil organic matter, boosts infiltration, and reduces nitrate leaching, providing a potential pathway to restore aquifers while improving water quality.

John Cherry, a pioneer in hydrogeology, framed a key question during our recent interview: What scale and duration of regenerative agriculture adoption could measurably raise groundwater tables while lowering nitrate concentrations to safer ranges? Answering this requires a coupled hydrology-solute transport model that captures how improved soil structure, microbial activity, and denitrification enhance both water quantity and quality. Success would demonstrate that agriculture can restore aquifers rather than degrade them.

4. Land Restoration’s Impact on Precipitation Recycling and the Small Water Cycle

Field research by Ronny Meier [Meier 2021], Millán Millán [Millán 2014], and others shows that even relatively small-scale restoration - 10 kilometers by 10 kilometers - can measurably increase rain. Millán Millán’s experiments in Spain revealed how soil moisture, groundwater, and fog contribute to localized rainfall.

These observations challenge conventional climate models, which suggest that larger areas must be restored to influence rainfall. Models may fail to capture intense, localized convective loops created by patches of enhanced evapotranspiration. Slow water interventions can inject moisture into the convective boundary layer locally, triggering rainfall without raising relative humidity uniformly across the region. Millán Millán’s climate models and Oliver Branch’s [Branch 2019] micrometeorological models support this.

The research question is this: How can high-resolution field data and micrometeorological observations be integrated into climate models to capture scale-dependent effects, and how much land restoration is required to restore rainfall?

5. Breaking the Drought-Fire-Flood Watershed Death Cycle

Expert practitioners like Zach Weiss and Sepp Holzer propose that landscapes can become caught in a self-reinforcing cycle of degradation, called the Watershed Death Spiral. Drought dry soils and make vegetation more flammable. Fires remove cover, potentially creating hydrophobic soils that amplify flood risk when rains return. Floods wash away soils that are needed to absorb the rain, a process which replenishes aquifers and increases precipitation recycling. This drought-fire-flood sequence leads to erosion, sediment loss, and accelerated watershed degradation. The drying of our continents via a variety of processes like river channelization, wetland depletion, groundwater depletion, deforestation, and the paving over of the land is contributing to the drought-fire-flood cycle.

The research question is this: How can a dynamic ecohydrological model capture these feedback loops, and what level of water cycle restoration might shift a watershed from a destructive regime to a regenerative, resilient state? Integrating fire, flood, soil, and vegetation parameters into a system-level model can help identify interventions that decouple drought, fire, and flood, ultimately building long-term resilience.

6. Groundwater as a Driver of Biome Flips

Groundwater can determine which ecosystems dominate a landscape. When water tables drop, deep-rooted species may die, allowing grasses, shrubs, or desert-adapted plants to take over. In some regions, this triggers rapid, often irreversible biome flips.

The research question is this: When groundwater declines, can it trigger sudden shifts from forest to savanna, or wetland to desert? How do these hydrological drivers influence ecosystem resilience? How much water restoration of the cycle do we need to do to protect our ecosystems? Addressing this question requires integrating dynamic groundwater models, vegetation physiology, and fire-climate feedbacks, especially where water stress interacts with human land use. Observations in riparian and groundwater-dependent ecosystems show strong local effects, but systematic understanding of groundwater-driven biome flips remains limited. Filling this gap could improve predictions of ecosystem collapse, guide restoration priorities, and safeguard biodiversity.

These questions are just the start of a research agenda. Working together, scientists and eco-practitioners can uncover even more questions and insights. By combining field observations with remote sensing and high-resolution modeling, we can put numbers on the benefits of nature-based solutions, guide restoration efforts where they’ll have the most impact, and help communities adapt to and mitigate environmental and climate challenges around the world.

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Branch, Oliver, and Volker Wulfmeyer. “Deliberate enhancement of rainfall using desert plantations.” Proceedings of the National Academy of Sciences 116, no. 38 (2019): 18841-18847

Meier, Ronny, Jonas Schwaab, Sonia I. Seneviratne, Michael Sprenger, Elizabeth Lewis, and Edouard L. Davin. “Empirical estimate of forestation-induced precipitation changes in Europe.” Nature Geoscience 14, no. 7 (2021): 473-478 https://www.nature.com/articles/s41561-021-00773-6

Millán, Millán M. “Extreme hydrometeorological events and climate change predictions in Europe.” Journal of Hydrology 518 (2014): 206-224

Norman, Laura M., Kristine Uhlman, Hanna A. Coy, Natalie R. Wilson, Andrew M. Bennett, Floyd Gray, and Kurt T. Ehrenberg. ““Leaky Weirs” capture alluvial deposition and enhance seasonal mountain-front recharge in dryland streams.” Applied Water Science 15, no. 2 (2025): 29

Norman, Laura M. “Ecosystem services of riparian restoration: a review of rock detention structures in the Madrean Archipelago Ecoregion.” Air, Soil and Water Research 13 (2020): 1178622120946337.

Norman, Laura M., Rattan Lal, Ellen Wohl, Emily Fairfax, Allen C. Gellis, and Michael M. Pollock. “Natural infrastructure in dryland streams (NIDS) can establish regenerative wetland sinks that reverse desertification and strengthen climate resilience.” Science of the Total Environment 849 (2022): 157738.

Sazib, Nazmus, John D. Bolten, and Iliana E. Mladenova. “Leveraging NASA soil moisture active passive for assessing fire susceptibility and potential impacts over Australia and California.” IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing 15 (2021): 779-787.

[Aragao 2012]

There is a powerful and surprisingly lucid way to understand the complex, integrated system that is Earth’s ecology, water, and climate. One of the keys to understanding our environmental resilience is that the planet is fundamentally nonlinear. To safeguard our future and manage environmental risk, we must move beyond gradualist assumptions and answer a critical question: What are the specific stabilizing loops that keep us in our current environmental regime, and what are the powerful, invisible drivers that could suddenly tip the system into a fundamentally different state?

The key to this analysis comes from the field of complex systems. This framework reveals that the Earth is not simply a linear machine responding to external forces, but a vast, interconnected network of causal loops. Because of this intricate coupling, the system doesn’t just decline or grow slowly, it can suddenly change. This nonlinearity is evidenced in planetary-scale phenomena where biomes, when pushed too far, abruptly reorganize themselves, shifting into a totally different, often irreversible state, much like liquid water instantaneously freezing into ice. Scientists call these sudden, systemic changes regime shifts or tipping points.

This lens provides the essential language and analytical tool-set for understanding the planet’s stability. Every stable ecological state, whether it be a desert, a rainforest, an ice sheet, is essentially a “mode” held in place by a constant, hidden struggle between two core forces: negative feedback loops that seek to stabilize the system by counteracting disturbances, and positive feedback loops (like a snowball rolling down a hill) that seek to amplify change by pushing the system further in the direction it is already moving. Understanding this struggle, knowing which loops stabilize us, and being wary of the drivers that unleash the amplifying loops, is crucial for climate and environmental policy. A regime shift occurs when the amplifying positive feedback overwhelms the stabilizing negative feedback, pushing the system past a critical threshold.

These regime shifts are a direct consequence of coupling, the non-independent and reciprocal linking of the Earth’s major sub-systems. Complex systems theory shows that the way components lock together determines the number and stability of available modes. Our deepening understanding of the climate system, therefore, requires radical interdisciplinary collaboration, the bringing together of hydrologists, ecologists, atmospheric scientists, and oceanographers. We must move past isolated studies of water or atmosphere to grasp how groundwater, the biosphere (vegetation), the atmosphere, and the oceans all actively couple. These deep, intertwined relationships, where the ocean influences rainfall, where groundwater influences biomes, where biomes and deforestation influences climate, where climate influences oceans, create a single, global network. This integrated approach is the only way to understand how all these things fit together to create planetary regimes. An example of this dramatic principle of nonlinearity and tipping is the fate of the Amazon rainforest.

Consider a forested landscape. Trees pull water from the soil and release it into the air through their leaves. That moisture forms clouds and falls back as rain. The rain sustains the forest, and a healthy forest transpires even more moisture. It becomes a self-reinforcing cycle: the forest creates its own rain, and that rain sustains the forest that created it. This is the “forest-rain mode,” a deeply coupled system in which vegetation, soil moisture, and atmosphere amplify one another.

In some regions, the same land can occupy a very different mode. In a savanna, sparse vegetation and grasses transpire only modest amounts of moisture. With so little water entering the air, the region produces little of its own rainfall. The landscape depends on whatever storms drift in from far away. With less rain, only drought-tolerant plants survive, and those plants contribute even less to atmospheric moisture. The feedback loop runs in the opposite direction, locking the region into a dry state. The difference between rainforest and savanna is not solar radiation or latitude; it is which feedback loops dominate.

Carlos Nobre, one of Brazil’s leading climate scientists, and Thomas Lovejoy have warned for years that the Amazon is approaching a tipping point. The rainforest does not merely receive rainfall; it manufactures it. Up to half of the rain that falls in the basin originates as transpiration from the forest itself. Remove enough forest, and the precipitation-recycling engine weakens. A weakened engine produces less rain, and less rain stresses the remaining forest. Stressed trees transpire less, producing still less rain. Eventually, the system crosses a critical threshold, estimated at around twenty to twenty-five percent deforestation, and the entire basin flips. Forest does not slowly thin; it collapses into a savannized state, even in areas never touched by chainsaws.

We are already at roughly seventeen percent deforestation in the Brazilian Amazon. The tipping point is not so far off distant possibility. And once the system flips, it becomes extremely hard to reverse. A savanna cannot generate the rainfall required to regrow a rainforest. The old feedback loop is gone. Even heroic reforestation efforts struggle because the atmospheric coupling, the invisible engine of moisture recycling, has been broken. The system now remembers its degraded state.

To understand why this irreversibility matters, it helps to zoom out and look at what a regime shift actually is. Any complex system, the climate, a forest, even a human body, stays in a particular mode because negative feedback loops keep it there. Negative feedback is stabilizing: when something changes, the system pushes back.

For instance, think of a thermostat in your home. It maintains room temperature through negative feedback: when the air gets too warm, the heater turns off; when it gets too cold, it turns on. The system stabilizes around a set temperature. Now imagine the thermostat malfunctions or the room is extremely cold. The negative feedback alone cannot maintain balance, and small changes can escalate. The system tips into a new mode where the room is uncomfortably hot or cold.

Another everyday example comes from the “wave” in stadiums. At first, a few people standing and raising their arms is dampened by the surrounding crowd. Negative feedback suppresses the small movement. But if enough people start participating, positive feedback takes over: one section stands because the previous section stood, and the motion propagates around the stadium. The system switches into a new, self-reinforcing mode, a moving wave, that would not exist without the initial excitation to overcome stabilizing forces.

A rainforest behaves this way. If one patch dries temporarily, deeper-rooted trees draw on stored moisture, transpire steadily, and help maintain local rainfall. The system dampens the disturbance. A savanna has its own stabilizing loop: grasses adapted to fire and drought, with low but steady transpiration, prevent total desiccation. Savannahs also have groundwater to draw upon for survival. Each landscape has a “home mode,” held in place by the negative feedbacks that give it resilience.

A regime shift happens when positive feedback overwhelms these stabilizing forces. Positive feedback amplifies change: a little drying leads to less vegetation, which leads to even less moisture recycling, which leads to further drying. Eventually, the stabilizing loop of the forest is too weak to counter the runaway loop pulling the system toward a new state. That is why the transition from forest to savanna is abrupt rather than smooth; the system is not sliding along a gradient but falling into a different basin of attraction, a new self-reinforcing mode. Thinking in terms of modes and feedback loops may sound abstract, but it is one of the most powerful tools we have for understanding how landscapes reorganize themselves and why some changes, once triggered, resist reversal. [Staal et al 2020]

Another idea from complex systems is the idea of fitness landscapes. In the attractor-basins/valleys (which you can see in diagram below) is where the system’s modes will settle into. It requires a perturbation to move it from one of valley to another. When it does the mode or regime shift happens. The idea of hystersis means the system is path dependent. What happens as rain increases depends if you are in the savannah basin or the forest basin.

[The fitness landscape and regime shifts of forest to savannah/grasslands. The system is bistable, meaning it has two modes Diagram from Staal et al 2020 ]

When we add groundwater to this vegetation-rain system this framework adds something extra: the subterranean reservoir, the living canopy above it, and the moisture in the sky form their own web of stabilizing and destabilizing loops, capable of holding a region in a humid, resilient mode or, if the feedbacks turn the wrong way, pushing it toward a drier, more fragile one.

Once we bring groundwater into the picture, the story of modes and feedbacks adds a another systems effect. Groundwater adds a slow, stabilizing reservoir to the system, a deep memory that can carry a forest across months of drought. In a healthy rainforest, this groundwater–tree–atmosphere loop acts as a powerful negative feedback: when the surface soil dries, deep roots tap the aquifer; when trees keep transpiring, they keep moisture recycling alive; when moisture recycling stays intact, rains eventually return; when rains return, groundwater is recharged. Each leg of the loop reinforces the others. The system cushions disturbance. It stays in the forest mode because its stabilizing feedbacks link the underground, the biosphere, and the atmosphere into a single self-regulating circuit.

But these feedbacks have their own tipping point. When groundwater drops below rooting depth, whether by over-extraction, prolonged drought, or cumulative deforestation, trees lose their buffer. They begin behaving like shallow-rooted plants, shutting down transpiration during dry periods. The negative feedback collapses. Suddenly, the system is dominated by positive feedback: less transpiration means less atmospheric moisture; less moisture means less rainfall; less rainfall means weaker groundwater recharge; weaker recharge means groundwater falls even further from reach. The loop amplifies itself, pushing the landscape toward an entirely different mode. What emerges is a reconfigured system in which groundwater, vegetation, and the atmosphere no longer reinforce one another. The reservoirs decouple. The internal rainfall engine falters. The region becomes dependent on whatever moisture external circulation happens to deliver, an identity much closer to savanna than forest.

Groundwater and vegetation interact in other ways too, Studies such as Ulrik Ilstedt and Douglas Sheil [2016] looked at in Burkina Faso have shown that trees create shade and enrich the soil with organic matter, improving its structure and increasing rainwater infiltration. These feedback loops can produce particular “modes” of groundwater storage: for example, in some savannas, intermediate tree cover maximizes groundwater, while too few or too many trees reduce it. Other research suggests different groundwater modes depending on soil type, climate, and vegetation configuration. The system is not linear: vegetation and groundwater reinforce each other, producing emergent states that are stable under certain conditions and prone to tipping under others. In places where groundwater can become saline like coastal areas, and much of Australia, a certain type of bistable mode behavior appears. When the water table is deep, a stable mode exists where healthy vegetation transpires large amounts of water, keeping the water table low. Conversely, if the saline water table rises high enough to intersect the root zone, the salt stresses the vegetation, severely reducing transpiration and creating a secondary, less desirable stable mode. This reduction in water uptake (a positive feedback) allows the water table to persist at a shallow, highly saline level, leading to the self-perpetuation of the dryland salinity regime. [Peterson 2012]

This perspective also sheds light on a long-standing debate in forest hydrology: do forests “use up” groundwater, or do they help sustain it? [Ellison 2012] On the one hand, trees extract water from the soil, which can reduce local groundwater levels, a straightforward demand-side effect. On the other hand, through precipitation recycling, forests generate rainfall that eventually recharges the aquifer, a supply-side effect. Traditional studies often focus on one side or the other, leading to apparently conflicting conclusions. But when we view the system through the lens of coupled modes and feedback loops, the picture becomes clearer. Cutting down trees might temporarily increase groundwater locally, but over longer timescales, reduced transpiration lowers rainfall, weakening recharge and potentially pushing the watershed into a new, drier mode with less total water. In other words, what looks like a linear, short-term gain can translate into a long-term loss once the full coupled system is considered. Mode thinking and complex adaptive systems provide a framework to reconcile these observations, showing that short-term changes in demand or supply are inseparable from the emergent behavior of the watershed as a whole.

Seen through this lens, the Amazon is not just a biome at risk of losing trees; it is a coupled hydro-biological system approaching a phase transition. The forest mode is defined by tight integration: deep groundwater feeding evergreen canopies, canopies maintaining atmospheric humidity, humidity sustaining rainfall, rainfall replenishing groundwater. The savanna mode, in contrast, is characterized by sparser tree cover and grasses that, while able to access groundwater, produce less transpiration overall. Moisture escapes to the atmosphere more slowly and over shorter periods, rainfall is less effectively recycled, and the system’s feedback loops are weaker. The difference between these modes is not only the amount of water available but the structure and strength of the feedbacks themselves: one configuration stabilizes, the other is more fragile. Because regime shifts depend on the architecture of feedback loops, not just averages of rainfall or temperature, the transition between modes can be swift, nonlinear, and difficult to reverse.

Traditionally, climatologists have often described the world’s biomes using the Köppen–Geiger classification, a framework in which temperature and rainfall largely determine vegetation type. In this view, climate dictates the biome: deserts are dry, rainforests are wet, and savannas sit somewhere in between. This is a form of climate determinism, treating ecosystems as passive responses to external climate variables. But the coupled groundwater–tree–rain dynamics we have described suggest a more nuanced picture. Biomes are not merely outcomes of average rainfall and temperature; they are part of a complex, dynamical system in which vegetation, groundwater, and climate co-evolve. Different modes can emerge from these interactions: a forest mode with strong rainfall recycling, and intermediate tree modes with groundwater and rain coupling. In other words, the Earth system itself generates multiple stable states, and which state emerges depends on the internal feedbacks and thresholds, not solely on the imposed climate averages. This perspective moves us beyond simple climate determinism to a framework where the biome–hydrology–atmosphere network actively shapes its own climate.

The logic extends further when we consider that the climate itself has multiple modes, self-reinforcing patterns of circulation that can persist for weeks, months, or even years. Phenomena such as El Niño, the Indian Ocean Dipole, Madden-Julien oscillation, and persistent jet stream blocking are examples of these modes. Each mode represents a stable or quasi-stable configuration of the atmosphere and ocean, much like forest and savanna are stable modes of the land–water system. These modes can shift abruptly, producing periods of intense rainfall, drought, or extreme temperature swings, sometimes called climate whiplash.

Recent research shows that vegetation and land processes are not just passive responses to these modes; they can actively influence them. Transpiration from trees affects regional and even global circulation patterns: it can alter the Hadley cell, which modulates jet stream behavior, potentially influencing blocking events that drive extreme weather. Land surface moisture and evapotranspiration can even affect the development and intensity of El Niño events [Lee 2021]. In other words, trees, soil, and groundwater are part of the chain that links local water use to modes of the entire climate system.

This chain of logic, from groundwater extraction to ecosystem feedbacks, to rainfall patterns, to atmospheric circulation modes, to climate extremes, is long and complex. Scientists are working on each link, but understanding how all the links interact remains a challenge. This is where the framework of complex systems, feedback loops, and regime shifts becomes useful: it provides a way to conceptualize the system’s architecture, highlight which loops stabilize or destabilize it, and identify where thresholds and new modes may emerge. Within this framework, groundwater extraction emerges as not just a local hydrological issue, but a potent climate driver capable of nudging the system into new modes, with consequences that may propagate far beyond the local landscape.

The Madden–Julian Oscillation (MJO), was discovered by observing repeating eastward-propagating waves of enhanced and suppressed tropical rainfall every 30 to 60 days. Scientists noticed that these oscillations could reinforce or dampen rainfall over forests and savannas depending on timing and local conditions. The key insight from the MJO, and from decades of studying atmospheric modes, is that emergent patterns often appear only when data are analyzed across space and time, revealing feedbacks and phase-like behavior that are invisible in short-term or localized observations. This is how we might find groundwater–climate coupling. Just as the MJO could not have been discovered by looking at a single weather station, the multiple modes of vegetation–groundwater–rainfall interaction may only emerge when we integrate long-term hydrological, vegetation, and atmospheric data. Detecting these coupled modes requires careful analysis across seasons, years, and landscapes, looking for correlations, lags, and feedback loops that indicate the system is self-organizing into distinct states.

A significant amount of groundwater can be brought up by trees to then transpire to create rain. Some estimates groundwater creates 10% of rain [Barlage 2021]. That rain can then flow back down into the aquifers. When there is bidirectionality there becomes a feedback loop. Feedback loops might then emerge modes. Currently groundwater-biome-climate coupling where the groundwater can also influence the climate, is an understudied research area with just a smattering of papers.

There is also a broader layer of coupling that also involves the ocean to add to the , atmosphere- land coupling. Traditionally, scientists have viewed the ocean as influencing the land, shifts in currents or the Atlantic Meridional Overturning Circulation (AMOC), for example, can drive changes in atmospheric circulation and rainfall over continents. (AMOC has two basic modes - if we shift out of our current mode it would lead to big climate shifts). However, recent research shows that land changes, such as widespread deforestation, can also affect ocean air [Lague], ocean temperatures and circulation. [Portman 2022].. This two-way interaction opens a whole new world of potential modes, where land/ecosystem, groundwater, ocean, and atmosphere feedbacks can produce emergent behavior that was previously unrecognized.

It is also worth stepping back and thinking about what drives climate and ecosystem changes in the first place. Scientists often speak of “climate drivers,” factors that push the Earth system in one direction or another. Carbon emissions are the most familiar: more greenhouse gases trap heat, alter temperatures, and shift weather patterns. But they are far from the only driver. Water matters too, and in ways that are just as fundamental. When we extract groundwater, we are not only changing aquifer levels; we are triggering a cascade of effects through soil, vegetation, rivers, and the atmosphere. Each loop feeds back into others, reshaping rainfall, surface water, and even the structure of biomes. Groundwater withdrawal may thus be a physical climate driver in its own right: it can flip landscapes from one mode to another, just as deforestation or greenhouse gas accumulation can. We need more research into this area.

There is also a whole other dimenasion. Biodiversity itself can act as a Complex Adaptive System (CAS). Trees, plants, and soil microbes do not just passively transpire water or store nutrients; they respond to local conditions, adapt their strategies, and interact with one another in ways that collectively shape larger-scale patterns. Through mechanisms like tuned transpiration, hydraulic lift, and shading, biodiversity can influence moisture, rainfall, and even regional or global climate in ways we are only beginning to quantify.

Complex Adaptive Systems describes systems composed of interacting agents that respond to each other and to the environment, producing emergent behavior that cannot be predicted from the behavior of individual components alone. So it is to be distinguished from the more basic complex systems where the components don’t make choices. A well-known example comes from economics: in a market, each buyer or seller makes choices based on prices, expectations, and competitors’ actions. The overall behavior of the market, trends, bubbles, or crashes, emerges from these local decisions, not from a single controller. Feedbacks can be stabilizing (negative) or amplifying (positive), and agents constantly adapt their strategies, producing new patterns over time. (See work by Brian Arthur and Doyne Farmer.)

Applying this analogy to forests and watersheds highlights how each tree, patch of soil, and aquifer segment acts as an adaptive agent. Trees make choices, when to transpire, when to conserve water, based on local conditions and interactions with neighboring plants. They can also choose when to bring up groundwater. Together, these choices shape emergent patterns of moisture, rainfall, and even regional climate. Giving trees this adaptive agency, puts a whole different factor into climate models and earth system models that can lead to them exhibiting quite different modes and regimes, and in their ability to regulate its regimes and regime shifts. The system is adaptive, self-organizing, and capable of both resilience and abrupt shifts, just like economic markets. This perspective could help formalize ideas proposed by hydrologists and ecologists: Hubert Savenije (2017, 2024) suggested that trees regulate water in watersheds for its own needs, so that the eco-watershed system is like an organism, while Makarieva and Gorshkov [2000] emphasized the role of living organisms in biotic regulation of the atmosphere. Complex adaptive systems provides a framework for understanding these insights: the coupled land–water–climate system is a network of interacting agents whose choices collectively produce stable modes, regulate the Earth system, and buffer against shocks.

Through this lens, the coupled land–water–climate system becomes not just a passive machine, but an adaptive, self-regulating network capable of buffering change, sustaining life, and guiding human interventions. Only by integrating multiple dynamical mechanisms, groundwater, vegetation, soil, atmosphere, and their feedbacks, can we begin to anticipate how new modes might emerge, and how seemingly local changes could ripple outward to shape global climate. Recognizing these multiple drivers, and understanding how they interact through complex feedbacks in a complex adaptive system, is essential if we hope to anticipate, and perhaps prevent, abrupt shifts in Earth’s coupled water–land–climate system.

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