The Paris Agreement’s 1.5°C warming limit was designed partly with ecosystems like the Amazon in mind.
Keep warming under that mark – the thinking went – and the forest had enough stability to weather what was coming.
A new study puts a precise asterisk on that protection.
With forest clearing just a few percentage points higher than today, the 1.5°C boundary no longer acts as a safety net – it sits in the middle of a danger zone.
The research was led by Nico Wunderling, a scientist at the Potsdam Institute for Climate Impact Research (PIK).
The role of deforestation
Without deforestation, the model puts the danger threshold for warming alone at around 3.7 to 4°C.
That’s the range where large stretches of the Amazon rainforest start losing stability under heat alone, before the effects of forest clearing are factored in.
Once deforestation joins the math, that cushion shrinks sharply.
“Deforestation makes the Amazon far less resilient than we previously anticipated,” said Wunderling, lead author of the study.
The model suggests that combining 22 to 28 percent forest loss with global warming of 1.5 to 1.9°C could push 62 to 77 percent of the basin toward degraded forest or savannah-like land.
About 17 to 18 percent of the rainforest is already gone. Warming continues to climb. Both numbers are now tracking toward that danger zone.
Trees that produce rain
The Amazon waters itself. Trees pull moisture from deep soil and breathe it out as vapor. That vapor drifts up, condenses, and falls again as rain somewhere else in the basin.
As much as half of the rainforest’s precipitation comes from this moisture recycling, and the tallest trees do most of the heavy lifting.
Pull out the trees and the loop weakens. Less vapor means less rain. The forest that’s still standing gets pushed steadily closer to its drought limit.
A 2023 paper found that tropical deforestation already produces sizable drops in regional rainfall, separate from any warming-driven effects on the rest of the basin.
Drying spreads downwind
What sets the new model apart is geography. The team mapped how moisture actually travels from one stretch of forest to another.
When trees in the eastern Amazon disappear, the drying effect can spread far beyond the cleared land.
Study co-author Arie Staal, an assistant professor at Utrecht University, noted that cleared land in one part of the basin can dry out forests thousands of miles downwind.
In the simulations, 88 percent of forest die-off without deforestation came from these chain reactions rather than local drought. Add deforestation, and the figure climbed to 99 percent.
Previous research already documented the forest’s declining ability to recover from drought. The new model puts hard numbers on how fast that decline could cascade.
Regions that face the greatest risk
Most of the existing forest loss runs along a curve through the southern and eastern edges of the basin – the so-called deforestation arc.
The study finds the location is unfortunate. Trade winds blow east to west across the Amazon, so trees cleared in the east stop sending moisture westward.
That creates the downwind cascade the model picks up.
Western and southwestern Amazon, which receive the most forest-generated rainfall, face the highest risk even when those areas remain mostly intact themselves.
A cascade of impacts
The team ran scenarios using a moisture-tracking model fed by detailed climate projections, processing more than a billion simulated water parcels across the Amazon basin.
Two thresholds together mark the danger zone: average annual rainfall dropping below about 73 inches, and dry-season water shortfalls past roughly 9 inches.
Without deforestation, those conditions only show up above 3.7°C. Add deforestation, and they appear far earlier.
Wetter regions can hold the line – but only briefly. Once a single patch flips, neighbors downwind tend to follow.
Recovery that could take centuries
The analysis relies on a single climate dataset and doesn’t simulate fire directly – a limitation that likely makes the projected timelines conservative rather than alarmist.
The deforestation scenario used to stress-test the results predate 2013 and may not fully reflect current land-use trends, though the team ran multiple sensitivity checks showing the core findings held.
According to Wunderling’s team, the findings are more than a warning.
Forests can grow back. Moisture recycling returns relatively quickly when trees return – faster than biodiversity, which can take centuries to rebuild.
A pledge to end deforestation
Brazilian and other South American governments have pledged to end Amazon deforestation by 2030.
The country has also committed to restoring about 30 million acres of cleared land in the Arc of Restoration.
A 2022 review of climate tipping points placed the Amazon among the most critical systems on Earth for preventing irreversible cascades at the global scale.
A tipping point that can still be avoided
Earlier modeling has tended to treat warming and deforestation as largely separate forces acting on the Amazon, each operating on its own threshold.
The new modeling collapses that distinction. Each pressure multiplies the other, and the combined ceiling lands much lower than either factor alone implies.
That redraws what “safe” warming looks like for the rainforest. With current forest-loss rates, even 1.5°C – the Paris Agreement target – may not provide enough margin.
Slowing emissions still help, but not enough. Stopping forest loss and restoring cleared land become equally critical to avoiding the basin-wide collapse the model projects.
Johan Rockström, director of PIK and a co-author of the study, said continued deforestation is pushing the Amazon closer to an irreversible tipping point, though he emphasized that the outcome can still be avoided.
The study is published in the journal Nature.
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