The Amazon rainforest could cross a point of no return at just 1.5–1.9°C of global warming — far below the 3.7–4°C threshold the study identifies without deforestation — if forest loss continues to mount. The world is already at 1.3–1.4°C and could reach 1.5°C by the end of this decade.

A study published today in Nature by researchers at the Potsdam Institute for Climate Impact Research (PIK) finds that with deforestation reaching 22–28% of the Amazon basin, between 62 and 77% of the forest could shift into degraded savanna-like ecosystems. Roughly 17–18% of the Amazon has already been cleared, placing the system uncomfortably close to that trigger range.

The mechanism is moisture recycling. Up to half of the Amazon’s rainfall is generated by the forest itself — trees transpire water vapor that falls again as rain downwind, in cycles that stretch hundreds of kilometers. Deforestation breaks those atmospheric rivers. Once one area dries out, neighboring areas lose their rainfall, which dries them out too.

“Deforestation makes the Amazon far less resilient than we previously anticipated,” said Nico Wunderling, the study’s lead author and a scientist at PIK. “Even moderate additional warming could then trigger cascading impacts across large parts of the forest.”

Without deforestation, the study puts the Amazon’s critical warming threshold at 3.7–4°C. Deforestation effectively cuts that threshold in half.

Brazil nearly halved its deforestation rate in 2025 after record losses the year before, and President Lula has pledged to halt clearing by 2030. But wildfires — increasingly able to spread as the forest grows hotter and drier — now account for two-thirds of forest destruction, a feedback loop that outside scientists warn could make such estimates conservative.

The Amazon has already flipped from carbon sink to carbon source. Widespread dieback could release enough carbon to warm the planet by an additional 0.2°C — a relatively modest number that would become part of every other climate calculation on Earth.

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