Wow, it seems so simple: healthy forests bring in and trigger their own rain. But, since most rain comes from elsewhere, shouldn’t we be more interested in this “elsewhere”? Why aren’t farmers, investors, entrepreneurs, and policymakers in agriculture, forestry, and land use more engaged with this bigger picture? For example, if China realises that most of its rainfall comes from beyond its Western borders- even as far as Europe. would they get involved in restoring farms and forests all the way to Europe? Big ideas. And you could argue: it doesn’t get much bigger than this.
Yes, we’re talking again about water cycles and this time with Douglas Sheil, Professor of Forest Ecology and Forest Management at Wageningen University, one of the most famous agricultural universities in the world. Why has it been so difficult to get scientific discoveries, like the biotic pump theory in physics, to enter other fields like climate science and forestry? We talk about the huge pushback biotic pump scientists have faced in publishing papers and gaining recognition over the past 20 years.
But we also talk about optimism, why water is a much easier sell than carbon, and how it could spark far more cross-border cooperation. Still, to make it work, we need to think big and get much better at working together, which is no easy feat. It’s a wide-ranging conversation on tropical forests, science, the Sahel, natural regeneration, and politics.
WHY SCIENCE HAS BEEN SLOW ON THE BIOTIC PUMP
The Biotic Pump theory, developed by theoretical physicists, faced significant resistance and dismissiveness from the broader scientific community, particularly climate modellers. This was due to its challenging of established models, its complex presentation, and a degree of institutional dogma.
Condensation over forests helps lower pressure and draw in humid air, increasing the odds of rainfall. It’s a physics-backed mechanism that complements what many farmers already observe: trees cool land, raise humidity, and, when timed right, can help trigger monsoons. Douglas shares field evidence from Borneo’s 20% rainfall decline after major deforestation and from Burkina Faso, where scattered native trees increased soil infiltration severalfold. The throughline is simple: water follows life. But the implications are big. If climate models underrepresent land–atmosphere feedbacks, we’re mispricing drought risk, overlooking a lever for local cooling, and underinvesting in the landscapes that stabilize rainfall.
“I asked around. And then a lot of people initially were a bit dismissive or suspicious; if it were true, we would know already or have different kinds of arguments. But you think, okay, nobody really knows. They’re just making stuff up.” Douglas Sheil
WHY WATER IS A MUCH EASIER SELL THAN CARBON
We also explore practice and policy. Why water is a better unifier than carbon for cross-border action. How biogenic particles from vegetation seed clouds and why swapping native diversity for monocultures can backfire. Where capital should flow first- dryland Africa and other regions ready for coastal-to-inland “green corridors” that stitch together intact habitat, farmer-managed natural regeneration, and productive agroforestry. And how supply chains, from Brazilian soy to European grains, depend on moisture recycling far beyond farm gates, making “elsewhere rain” a material risk and a tangible opportunity.
Water is a more intuitive and universally critical issue for people everywhere, from farmers to city dwellers. Unlike the abstract concept of carbon, the immediate importance of water for life and livelihoods makes it a more compelling and relatable subject for engagement.
“It is so much easier to engage people about water than, for example, about carbon. Everybody, everywhere, cares about reliable access to water… the floods or the droughts, I mean. Everybody, this impacts everybody. Carbon is a difficult pitch. Carbon is a difficult sell.” Douglas Sheil
CLIMATE MODELLERS ARE THE MOST DIFFICULT TO PERSUADE
He identifies climate modellers as the group most resistant to accepting the biotic pump theory. He suggests this is due to the highly politicised nature of climate science, which leads them to bat away new ideas they perceive as challenges to their established work, and the sheer complexity of their existing models.
“Perhaps it’s the climate modellers that are the most difficult to persuade… There are all kinds of complications they have to deal with all the time. And this, to them, just seems like another one to add to their list of over a hundred items. And the question, of course, is would it really make a big difference? And I clearly think it would, and I think Anastasia clearly thinks it would, but we really need somebody to take this seriously.” Douglas Sheil
HOW MOST OF THE RAIN COMES FROM ELSEWHERE AND WHY THAT IS IMPORTANT
Rainfall in one region is often dependent on forests and vegetation in another, upwind region. This understanding is crucial because it reveals that deforestation in one area can directly cause drought and reduce productivity in another, making forest conservation a matter of international cooperation.
“A lot of their rainfall is coming from elsewhere. And I think we are only just beginning to really think about these connections and what they imply.” Douglas Sheil
OTHER POINTS DISCUSSED
Koen and Douglas also talked about:
- Forests draw “elsewhere rain” via condensation-driven pressure drops
- Evidence of rainfall decline with deforestation, including Borneo
- Sahel greening and scattered trees boosting infiltration
- Native vegetation timing helps trigger monsoons
- Risks of monocultures vs benefits of diverse agroforestry
- Investment focus on coastal-to-inland green corridors
- Supply chain exposure to rainfall recycling and tipping points
- Cross-border cooperation to fund upwind regeneration
LINKS:
- Douglas Sheil
- For investors, the cost of inaction around growing water scarcity will be ‘significant,’ says FAIRR
LINKED INTERVIEWS:
- Rob de Laet – Water is key to cool the planet within 20 years
- Alpha Lo – What if water is more important than carbon
- Anastassia Makarieva – Healthy forests invest their capital to create their own rain
- Water cycles series
- Dimitri Tsitos – Making regenerative intensive tree crops profitable
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The above references an opinion and is for information and educational purposes only. It is not intended to be investment advice. Seek a duly licensed professional for investment advice.