More than a third of the Amazon rainforest is struggling to recover from drought, according to a new study that warns of a “critical slowing down” of this vital global ecosystem. Signs of weakening resilience raise concerns that the world’s largest tropical forest and biggest terrestrial carbon sink is approaching a point of no return.
The study highlights how human-induced climate change has led to four “once-in-a-century” droughts in less than 20 years, placing unprecedented stress on trees and plants, many of which are dying from dehydration. Historically, the South American rainforest, which covers an area roughly half the size of Europe, could recover from single droughts, with its canopy expanding and contracting with the seasons. However, recoveries are now slower due to increasingly intense droughts in the southeast and more frequent ones in the northwest.
Published in the Proceedings of the National Academy of Sciences, the study analyzed satellite images of vegetation activity from 2001 to 2019, examining tens of thousands of 25-square-kilometer pixels monthly and correlating them with local rainfall data. The researchers aimed to understand how drought frequency, intensity, or duration contributes to the instability of Amazon vegetation. They found that 37% of the mature vegetation in the region showed a slowing-down trend, with the highly deforested and degraded southeastern Amazon being most vulnerable to a catastrophic “tipping event,” or a shift to a drier state.
The research concluded that drought intensity had a greater impact than frequency, though both were destabilizing. Lead author Johanna Van Passel noted that the satellite images likely understate the severity, as the situation beneath the canopy could be worse. Trees, having the longest life cycles, are the last to show tipping points. If a tipping point is approaching at the forest level, it is likely more advanced at a micro level.
This is alarming news for the Amazon and the world. Home to 15,000 tree species, the rainforest plays a crucial role in sequestering carbon dioxide. However, its resilience is being eroded by climate change driven by human activities such as deforestation and fossil fuel combustion. The paper suggests that the slowing recovery rate of the forest may be an early indicator of large-scale ecosystem collapse.
Van Passel expressed deep concern for the Amazon’s future, warning that continued and intensifying droughts could push the forest to a tipping point. Last year’s severe drought, which left rivers at record lows, worsened fires, and caused mass die-offs of river dolphins, exemplifies this trend. Areas with the lowest rainfall since the early 2000s experienced the greatest decline in stability.
Intense, hot droughts increase tree mortality through hydraulic failure, where xylem vessels rupture, and carbon starvation, where closed stomata prevent photosynthesis. Shorter, more intense rainy seasons hinder the forest’s recovery, as many tree species have not adapted to such extreme conditions. Global warming is expected to worsen these trends, increasing drought intensity and frequency in the Amazon, altering forest structure and function, and bringing more areas closer to a tipping point. Deforested and fire-affected regions are particularly vulnerable.
The paper warns that changes in the internal rain cycle could trigger cascading effects, further slowing recovery in other parts of the Amazon and impacting global tipping points. It calls for international policymakers to protect mature forests and Indigenous communities, and to reduce greenhouse gas emissions. Van Passel emphasized the urgency of acting on this information, stressing the need to protect existing forests, particularly in the Amazon’s south, and to stop climate change. Despite her worries, she remains hopeful.
