More than half of the rainforest could turn into savanna — threatening wildlife, shifting weather patterns and fueling climate change
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The Amazon rainforest, in the Amazonas state in Brazil, is
losing resilience, according to a study in the journal Nature
Climate Change. (Dado Galdieri/Bloomberg News)
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Yet satellite images taken over the past several decades reveal that more than 75 percent of the rainforest is losing resilience, according to a study published Monday in the journal Nature Climate Change. The vegetation is drier and takes longer to regenerate after a disturbance. Even the most densely forested tracts struggle to bounce back.
This widespread weakness offers an early warning sign that the Amazon is nearing its “tipping point,” the study’s authors say. Amid rising temperatures and other human pressures, the ecosystem could suffer sudden and irreversible dieback. More than half of the rainforest could be converted into savanna in a matter of decades — a transition that would imperil biodiversity, shift regional weather patterns and dramatically accelerate climate change.
Historically, the Amazon has been one of Earth’s most important “carbon sinks,” pulling billions of tons of carbon dioxide from the air and storing it in vegetation. Researchers fear that this carbon’s sudden release would put humanity’s most ambitious climate goal — limiting temperature rise to 1.5 degrees Celsius (2.7 degrees Fahrenheit) — out of reach.
“As a scientist, I am not supposed to have anxiety. But after reading this paper, I am very, very anxious,” said Carlos Nobre, a climate scientist at the University of São Paulo’s Institute of Advanced Studies, who was not involved in the new research. “This paper shows we are moving in the completely wrong direction … If we exceed the tipping point, that’s very bad news.”
The Amazon is one of several “tipping elements” in the global climate, scientists say. Rather than steadily worsening as the planet warms, these systems have the potential to abruptly switch from one phase to another — possibly with very little warning.
For the past 50 million years, the Amazon has been in a wet rainforest phase. The trees themselves ensured their continued existence: Water evaporating from leaves created an endless loop of rainfall, while the dense canopy prevented sunlight from drying out the soil. The contours of the forest may have shifted somewhat in response to ice ages, wildfires and rising seas, but it was always able to return to its lush, verdant state.
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An aerial view of deforestation in the western Amazon region
of Brazil in 2017. (Carl de Souza/AFP/Getty Images)
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By felling roughly 17 percent of its trees, people have undercut the forest’s water recycling mechanism. Trees stressed by drought are more vulnerable to wildfires. And the more trees die, the less rain falls, which in turn makes tree die-offs worse.
At a certain point, the ecosystem will lose more trees than it can recover in these hot, dry conditions. The dark, dense, damp tropical rainforest will give way to a more open savanna. Mathematician Niklas Boers, who contributed to the new paper, compared it to someone leaning back in a chair. If they don’t tilt too far, they can easily return to having all four legs on the floor. But once they pass the tipping point, the whole system comes crashing down. And it is much harder to get up again than it was to fall.
The satellite imagery Boers and his colleagues analyzed suggests that the Amazon is still wobbling on the edge of tipping, the scientists say. Looking at tracts of forest with at least 80 percent broadleaf tree cover — areas that have not been heavily affected by deforestation — researchers found that the vast majority of forest patches recover more slowly after seasonal fluctuations than they did 20 years ago. Tracts in the rainforest’s drier southern reaches, as well as ones that were closer to roads, suffered the most.
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A burned area of the Amazonia rainforest in the surroundings
of the city of Porto Velho in Rondonia state, Brazil. (Mauro
Pimentel/AFP/Getty Images)
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Yet unlike ice sheets and monsoon systems, which respond solely to the amount of heat humans are trapping in Earth’s atmosphere, the Amazon is being pushed toward its tipping point by two forces: deforestation and climate change. This also gives Boers hope, because it means humanity has two strategies for protecting the ecosystem.
“If we take one of those factors out of the equation, my intuition would be that the system would be able to cope with it,” he said. “That’s exactly what one should tell the Brazilian, Colombian and Peruvian governments: Stop deforestation today.”
Links
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- Countries’ climate pledges built on flawed data, Post investigation finds
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- How climate change is making parts of the world too hot and humid to survive
- The undeniable link between weather disasters and climate change
- The world’s biggest plant to capture CO2 from the air just opened in Iceland
- Toronto is home to the world’s largest lake-powered cooling system. Here’s how it works.
- Harnessing the energy of the ocean to power homes, planes and whisky distilleries
- The Glasgow climate pact, annotated
- Latest U.N. report shows what will be lost — and what can still be saved — as Earth warms
- 10 steps you can take to lower your carbon footprint
- Thomas E. Lovejoy III, the man who brought U.S. policymakers to see the Amazon firsthand
