Tropical Forests
The Amazon makes its own rain. Cut enough of it and the forest can no longer water itself, and no amount of replanting brings that back.
The effect is immediate. This stops an emission that is happening right now.
Project Drawdown classifies this as Emergency Brake.
Origins
The tropical forest was, for most of European history, a place to be got through rather than understood. It was hot, it was full of things that bit you, and it stood between a boat and whatever the boat had come for.
The scientific reversal has a name, and it is Alexander von Humboldt. Travelling through South America between 1799 and 1804, he did something nobody had quite done before: he treated the forest not as a collection of specimens but as a system, in which climate, vegetation, soil and water were bound together and could not be understood apart. He noticed, at Lake Valencia in Venezuela, that clearing the surrounding forest had lowered the lake, and he wrote down the connection. It is arguably the first description of human-caused climate change in the scientific literature, and it was about deforestation.
It took another century and a half for the second great insight to arrive: that the forest does not merely respond to the climate, it manufactures it. Brazilian and international researchers, tracing the isotopes in rainfall, established that a very large share of the rain falling on the Amazon has already passed through the Amazon — exhaled by the trees, carried inland, and dropped again. Moisture recycles through the basin several times before it leaves. The forest is not sitting in a wet climate. The forest is the wet climate.
Which produced the finding that now haunts the field: if the forest makes its own rain, then there is a point at which cutting enough of it means the rest can no longer sustain itself. Not a slope. A cliff.
What it actually is
Tropical forest is the densest concentration of life on Earth. A few hectares can hold more tree species than the whole of North America, and the insects, fungi and animals depending on them have never been fully catalogued and, at current rates, never will be.
But the thing that makes tropical forest distinct as a climate solution is the flying rivers. The trees transpire enormous volumes of water, which rise, travel as aerial rivers, and fall again as rain — watering not only the forest but the agriculture of southern Brazil and Argentina thousands of kilometres away. Roughly half the rain that falls on the Amazon was previously exhaled by the Amazon.
This creates a feedback that most ecosystems do not have. Clear a patch and the local rainfall drops. Drier forest burns more readily. Burned forest transpires less. Less transpiration means less rain, which means drier forest. Push this far enough and the eastern Amazon stops being able to sustain rainforest at all and converts, irreversibly on human timescales, to degraded savanna.
Parts of the southeastern Amazon have already crossed from being a carbon sink to being a carbon source. This is not a projection. It has been measured.
The numbers
The tipping point. Estimates of where the Amazon can no longer sustain itself cluster in the range of 20–25% deforestation, combined with warming. Roughly 17–20% of the original forest is already gone. There is a serious scientific argument that we are inside the margin of error of an irreversible transition, and no serious argument that we are comfortably outside it.
The rain. On the order of half the precipitation falling on the Amazon basin has been recycled through the forest itself. The forest waters the agriculture of a continent, and does not send an invoice.
The sink is failing. Parts of the southeastern Amazon have flipped from absorbing carbon to emitting it, driven by deforestation, fire and drought. The world’s largest terrestrial carbon sink is, in places, now a source.
The prize. Avoiding human-caused forest loss globally offers on the order of 3.6 Gt CO₂-eq per year, with nearly 2 Gt of that achievable below US$10 a ton (Griscom et al., 2017). The tropics dominate that figure, because tropical forest holds the most carbon per hectare and is being cleared the fastest.
The most effective protection. Not a fence. Between 1985 and 2020, 90% of Amazon deforestation occurred outside Indigenous lands, which lost just 1.2% of their native vegetation across that period.
Why it matters
There is a way of framing this that gets past every political argument, and it is simply to describe what is being traded.
The Amazon is being converted, hectare by hectare, into cattle pasture and soy fields. The cattle produce beef. The beef is eaten. And the forest that is destroyed to produce it took, in its full complexity, somewhere between ten and fifty million years to assemble. That is the actual trade: an ecosystem older than the human genus, exchanged for a commodity with a shelf life measured in days.
You do not have to have a view on capitalism to think that is a bad price.
And it is not even a trade that works on its own terms. The soy farmers of southern Brazil depend on rain that the forest generates. The ranchers clearing the frontier are, at scale, destroying the rainfall their own industry runs on. This is not a conflict between the economy and the environment. It is the economy quietly sawing through the branch it is sitting on, and the environmentalists are the ones pointing at the saw.
The people who have understood this longest are the ones living in it. The forest is standing where they are, and it is falling where they are not. Whatever else is true, that fact should organise our thinking.
What it actually takes
The supply chain, which is where the chainsaw actually lives. Tropical deforestation is not driven by people who hate trees. It is driven by cattle, soy, palm oil and the roads that open the frontier for them — and those commodities end up in supermarkets on the other side of the world. This makes deforestation a demand-side problem, and it makes verified deforestation-free sourcing one of the few levers with real reach.
Land tenure, which is the most effective thing we know of. See above. The evidence is not close.
The roads. Almost all tropical deforestation happens within a few kilometres of a road. A road into a forest is not a neutral piece of infrastructure; it is the deforestation, arriving early. Infrastructure planning is forest policy whether or not anyone calls it that.
Being honest about the alternative. A Brazilian rancher clearing forest is doing something economically rational under the rules he faces. Telling him he is a villain accomplishes nothing. Changing what pays — through enforcement, market access, or payment for standing forest — accomplishes a great deal. The moralising is cheap and it is also counterproductive.
Where it matters most
The Amazon is the one that makes its own weather and the one closest to a threshold. Everything else is secondary to this.
The Congo Basin is the second-largest rainforest on Earth, still largely standing, and receiving a small fraction of the world’s attention and funding. Beneath it lies the Cuvette Centrale, the largest tropical peat complex on the planet, only recently discovered. It is the greatest opportunity in tropical forest conservation precisely because the loss has not yet happened.
Sundaland — Borneo, Sumatra, the Malay Peninsula — is where the loss has been fastest, driven by oil palm and pulpwood, and where forest sits on peat, which makes clearing it doubly catastrophic.
The Atlantic Forest of Brazil is the cautionary tale and the proof of hope: reduced to a small fraction of its original extent, and now the site of the most ambitious forest restoration effort anywhere.
The Guinean Forests of West Africa are where cocoa meets the last forest fragments, and where what happens in European supermarkets is decided.
How to tell it’s being done well
Does it distinguish primary forest from plantation? A great deal of forest-cover accounting quietly treats a eucalyptus monoculture as equivalent to primary rainforest. They are not equivalent in carbon, water, or life. Reporting that blurs this is reporting designed to be blurred.
Does it address the commodity driving the clearance? Protection that ignores the cattle, soy or palm oil economics is protection that will be overrun.
Is the additionality real? A carbon credit for protecting forest that nobody was going to cut is not a credit. It is a donation with a receipt. Ask what the counterfactual actually was.
Who holds the land? If a project is not working with or through the Indigenous and local communities who live in the forest, it is working against the best evidence we have.
What you can do
Anyone
- Beef and soy drive most Amazon clearance; palm oil drives most in Southeast Asia. You do not have to be a purist to be aware of it.
- Chocolate is a forest question. Most cocoa comes from West Africa and much of it was grown on land that was forest very recently.
- Support Indigenous-led forest organizations. On the evidence, they are the most effective forest protection on Earth.
Policymakers
- Deforestation-free import regulation works, because the demand is concentrated in a small number of wealthy markets.
- Stop funding roads into intact forest. Almost all tropical deforestation happens within a few kilometres of one.
- Recognise Indigenous title. Cheapest and most effective, and it is not close.
Business and investors
- Trace your commodities. Satellite monitoring means deforestation-free claims are now checkable, which means unverified claims are now a choice.
- Pay a premium that reaches the farmer. Deforestation-free cocoa that does not raise farmgate income is a rule the farmer cannot afford to follow.
Philanthropy
- The Congo Basin receives a fraction of the funding the Amazon does and holds nearly as much at stake. It is the most underfunded major forest on Earth.
- Fund enforcement and tenure, not just designation.
Where this matters most
Who is working on this
We are researching which organizations in our directory of 8,493 actively work on this solution, and we only list an organization once we have verified it. That research is ongoing. In the meantime, search the directory yourself:
Questions
Does the Amazon really make its own rain?
Yes. Roughly half the rain falling on the Amazon basin has already passed through the forest, transpired by the trees and carried inland as aerial moisture before falling again. The forest is not simply sitting in a wet climate; it substantially generates one, and it waters agriculture thousands of kilometres away.
What is the Amazon tipping point?
The point at which enough forest has been cleared that the remaining forest can no longer generate the rainfall it needs to sustain itself, converting irreversibly toward degraded savanna. Estimates cluster around 20 to 25% deforestation combined with warming. Roughly 17 to 20% is already gone, which places us uncomfortably close to the margin of error.
Is the Amazon still absorbing carbon?
Less than it was, and in places not at all. Parts of the southeastern Amazon have already flipped from being a carbon sink to being a carbon source, driven by deforestation, fire and drought. This has been measured, not projected.
Why is tropical deforestation worse than logging elsewhere?
Tropical forests hold more carbon per hectare than temperate or boreal forest, they host far more species, and when cleared they regrow into something dramatically less diverse. They also generate their own rainfall, which means clearing enough of them can push the remainder past the point of self-sustaining.
What actually drives it?
Commodity agriculture, overwhelmingly: cattle, soy and palm oil, together with the roads, mining and illegal logging that follow. Almost all tropical deforestation occurs within a few kilometres of a road, which means road-building into intact forest is deforestation policy whether or not it is called that.
What is the single most effective protection?
Recognising and enforcing Indigenous land tenure. Between 1985 and 2020, 90% of Amazon deforestation occurred outside Indigenous lands, which lost only 1.2% of their native vegetation over that period. No other intervention has a record like it, and none is cheaper.
Sources
- Project Drawdown - Protect Forests (Drawdown Explorer) Framework and classification. Cited, not reproduced.
- Griscom et al. (2017), PNAS - Natural climate solutions
- Gatti et al. (2021), Nature - Amazonia as a carbon source linked to deforestation and climate change
- Lovejoy & Nobre (2018), Science Advances - Amazon tipping point
- Sze et al. (2021), Nature Sustainability - Reduced deforestation in Indigenous Lands pan-tropically
- Global Forest Watch
The solution taxonomy follows the framework popularised by Project Drawdown. The analysis above is our own; for their carbon modeling and rankings, visit them directly.