Brazilian climate scientist Carlos Nobre has warned that the Amazon rainforest is perilously close to an irreversible tipping point, beyond which it would transform into a degraded savannah. The world’s largest tropical rainforest is a pillar of the global climate system, home to immense biodiversity and essential for regional weather patterns.
Nobre estimates that the tipping point could be reached if deforestation reaches 20-25% or global heating rises to 2.0-2.5°C above preindustrial levels. Currently, 18% of the Amazon has been cleared and the world has warmed by 1.5°C, on course to reach 2.0-2.5°C by 2050.
The rainforest suffered record droughts in 2023 and 2024, the fourth severe drought in two decades. The dry season in the southern Amazon is now four to five weeks longer than 45 years ago, with 20% less rain. If the dry season extends to six months, self-degradation becomes unavoidable. In southern Pará and northern Mato Grosso, minimum rainfall during the dry season is already below 40mm per month.
Degraded pastures recycle only one-third to one-fourth of the water vapour that forests do, contributing to longer dry seasons. A savannah would be less humid, more vulnerable to fire, and lack the closed canopy that keeps the forest floor moist and fire-resistant. Nobre stresses that the southern Amazon, an area of over 2 million square kilometres, is at or very close to the tipping point.
