Satellite images taken over the past several decades show that more than 75 percent of the Amazon rainforest is losing resilience, according to a new study published in the journal Nature Climate Change. The vegetation is dryer and takes longer to recover after a disturbance. Even the most densely forested regions struggle to bounce back.
The study authors say that this is an early warning sign that the Amazon is nearing its “tipping point”. With rising temperatures and other human pressures, the ecosystem could suffer sudden and irreversible dieback. Over half the rainforest could be converted into savanna in a matter of decades – a transition that would threaten biodiversity, shift regional weather patterns and dramatically accelerate climate change.
Historically, the Amazon has been one of the Earth’s most important “carbon sinks,” pulling billions of tons of carbon dioxide from the air.
Over the past 50 million years, the Amazon has been in a wet rainforest phase, with water evaporating from leaves creating an endless loop of rainfall, while the dense canopy prevented sunlight from drying out the soil.
Human-caused warming and deforestation has disturbed this self-reinforcing system. Warmer conditions in the Atlantic Ocean have extended the Amazon’s dry season by several weeks. By chopping down roughly 17 percent of its trees, people have undercut the forest’s water recycling mechanism.
At some point, the ecosystem will lose more trees than it can recover in these hot, dry conditions. The dark, dense, damp tropical rainforest will transition to a more open savanna.
The warming consequences of suddenly losing half the rainforest would be felt thousands of miles away and for centuries from now, scientists warn. It would mean increasing storms and worsening wildfires, chronic food shortages and nearly a foot of sea level rise. It could also trigger other tipping points such as melting of ice sheets.