GoKawiilEl Niño is back with a vengeance. A mammoth patch of warm water is growing in the equatorial Pacific Ocean, and the US National Oceanic and Atmospheric Administration is giving four-in-five odds that the disruptive climate phenomenon will turn into a “very strong” event by the end of the year. Some forecasters say this El Niño is on track to become the strongest in at least 150 years.
For the Amazon rainforest, the timing could hardly be worse.
Trouble in the Amazon
El Niño events, which happen roughly once every two to seven years, upset weather patterns around the globe. For the Amazon basin, they typically trigger severe droughts. The most recent El Niño, which formed in June 2023 and had dissipated by June 2024, hit the rainforest especially hard by drying out large sections1, shrinking major rivers to historic lows2 and helping to fuel the worst fire season in more than two decades3 (see ‘Tree troubles’). Some researchers suggest that the developing El Niño, coming on top of warming and drying caused by climate change, might push the rainforest past its ‘tipping point’ — shorthand for the threshold at which a runaway cascade of drying, tree death and wildfire would begin to spread irreversibly across the Amazon basin. If that were to happen, rainforest would give way to savannah and degraded woodland over decades, potentially releasing an amount of carbon equivalent to several years of global emissions and dramatically reducing rainfall across South America and beyond4.
Source: Ref. 3
The impacts of the current El Niño might not be as severe as the gloomiest forecasts suggest; much depends on how strong it becomes, and how much of the forest burns. But the Amazon is entering this test in a weakened state, and some researchers who know it well are uneasy. “If this next El Niño really is as strong as we think it will be, it might result in things like huge wildfires in the Amazon, spreading across areas that were unimaginable before,” says Bernardo Flores, a specialist in Amazon resilience at the Juruá Institute in Manaus, Brazil. “We will see how much of the forest might die from it.”
Past trauma
Part of the concern, researchers say, is that large areas of the Amazon might still be recovering from the severe droughts of 2023–24. Hao Bai, a forest ecologist at Peking University in Beijing, and his colleagues determined this by analysing 33 years of radar satellite data that tracked two indicators of forest health — how much moisture the forest holds and how much living plant matter it contains — across the Amazon basin. During the 2023–24 droughts, the researchers found, radar measurements associated with both indicators fell to their lowest levels since satellite records began in 19925. The authors estimate that less than half of the affected forest will have returned to pre-drought conditions within seven years — the slowest recovery from a major Amazon drought in the satellite record.
To Bai and his colleagues, these findings underscore the Amazon’s increasing vulnerability to intense droughts spurred by El Niño and human-caused climate change. If major droughts continue to strike before the forest has recovered from previous ones, the repeated stress could weaken the forest, leaving it less able to withstand climate extremes.
When will the Amazon hit a tipping point?
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