Deforestation is the leading cause of declining rainfall in the Amazon rainforest
For decades, the Amazon has been growing drier. A new study in Nature Communications disentangles how much of this shift is due to global warming and how much to tree loss within the forest. The results suggest deforestation is the dominant factor.
Researchers led by Marco Franco and Luiz Augusto Toledo Machado examined 35 years of land-use and atmospheric data across Brazil’s “Legal Amazon,” an area of 5 million square kilometers. Using statistical models, they separated the effects of greenhouse-gas emissions from local forest loss. They found deforestation accounts for nearly three-quarters of the rainfall decline and about one-sixth of the warming during the dry season since the mid-1980s.
Between 1985 and 2020, dry-season rainfall fell by about 21 millimeters per year, of which 15.8mm—74.5%—was linked to forest loss. Maximum daily temperatures rose by 2°C, with 0.39°C, or 16.5%, due to deforestation. The findings confirm what scientists have long suspected: forest clearance disrupts not only carbon balances but also local weather.
Amazonian trees are central to this system. Through transpiration they draw water from the soil and release it into the air, providing more than 40% of the region’s rainfall. This moisture rises and condenses into clouds, while creating low-pressure zones that pull in additional humid air, a process some call the “biotic pump.” Strip away forest and the cycle falters.
The consequences extend beyond the basin. The “flying rivers” of vapor influence rainfall across Brazil’s agricultural heartlands and into the Andes. Deforestation is also altering the South American monsoon, raising the risk of drought in central and southeastern Brazil.
If recent trends continue, by 2035 the region could see dry-season rainfall fall by another 7mm and temperatures climb by 0.6°C. The Amazon’s climate could begin to resemble that of the Cerrado savanna or even the semi-arid Caatinga.
Such a shift would test the resilience of the forest’s 11,000 known tree species, the communities that depend on them, and distant agricultural zones and megacities that rely on the Amazon’s moisture.
🔬 Franco, M.A., Rizzo, L.V., Teixeira, M.J. et al. How climate change and deforestation interact in the transformation of the Amazon rainforest. Nature Communications 16, 7944 (2025). https://www.nature.com/articles/s41467-025-63156-0