The Amazon rainforest could endure decades of drought, but it won’t come out the same. A new long-term study reveals that this resilience comes at the expense of its giant trees and its critical role as Earth’s carbon sink.
Key Points at a Glance
- Amazon rainforest shows long-term resilience to drought—but with major biomass loss
- Over 15 years, the largest trees died, releasing vast stores of carbon
- Surviving trees adapted, stabilizing carbon uptake after initial collapse
- Amazon’s role as a carbon sink could be sharply diminished in a drier climate
Could the Amazon rainforest survive a drier future? A new study suggests it can—but the cost is steep. In the world’s longest-running drought experiment in tropical rainforest, a team of international researchers led by the University of Edinburgh and the Federal University of Pará in Brazil has shown that while parts of the Amazon can stabilize after prolonged drought, this stability comes with profound ecological consequences.
The study, published in Nature Ecology and Evolution, examined a one-hectare plot of rainforest in north-eastern Amazonian Brazil over 22 years. Since 2002, the site has been subject to artificial drought, with thousands of transparent panels diverting half of the natural rainfall away from the forest floor. The goal: to simulate the dry future projected for large swaths of the Amazon under climate change.
The results reveal a dramatic transformation. During the first 15 years of rainfall reduction, most of the forest’s largest trees—its towering carbon-storing giants—died. These trees hold a significant portion of the Amazon’s total biomass, and their deaths released immense amounts of carbon into the atmosphere. Altogether, the experimental plot lost more than one-third of its living biomass, particularly in the form of trunks, roots, and branches.
This is no small loss. The Amazon stores more carbon than any other terrestrial ecosystem, acting as a natural brake on global climate change. When that carbon is released, either through deforestation or drought-induced dieback, it accelerates global warming. According to the research team, such biomass loss across the Amazon could significantly reduce its function as a carbon sink—possibly turning it into a carbon source.
However, the study also brings a glimmer of cautious optimism. After the initial wave of large tree deaths, the remaining forest began to stabilize. Over the past seven years of the experiment, water availability for surviving trees increased, and these trees no longer showed signs of drought stress. In fact, they began to accumulate carbon again—albeit at lower levels than before.
“We’re seeing signs of adaptation,” said Dr. Pablo Sanchez Martinez, lead author of the study from the University of Edinburgh’s School of GeoSciences. “But this comes only after the forest paid a high price in lost biomass and carbon.”
The researchers stress that this recovery does not mean the Amazon is immune to climate change. On the contrary, the transformation it undergoes—losing its largest, most carbon-rich trees—marks a substantial shift in its ecological structure and global role. Moreover, the study only examined drought caused by reduced soil moisture. It did not account for related stressors like rising temperatures, shifting humidity, fires, or storms, all of which are expected to intensify in a warming world.
Even in its altered state, the drought-affected plot still retained more biomass than many dry forests or savannas, highlighting the Amazon’s inherent resilience. But as Professor Patrick Meir of the University of Edinburgh emphasized, “Ecological responses to climate can have very large impacts on our environment, locally and globally. We cannot understand and predict them without long-term collaborative research of this sort.”
This study underscores just how critical long-duration experiments are for truly grasping the complexity of ecological adaptation. Short-term observations might miss the delayed consequences of environmental stress, such as mass tree deaths, or the long timelines required for any form of stabilization.
As policymakers and climate scientists search for solutions to the mounting climate crisis, understanding the tipping points—and survival strategies—of the world’s largest rainforest becomes ever more urgent. The Amazon may endure, but not without shedding part of its essence.
Source: University of Edinburgh
