The Atlanta Journal-Constitution
Data shows Amazon rainforest hurtling to ‘tipping point’
Viewed from space, the Amazon rainforest doesn’t look like an ecosystem on the brink. Clouds still coalesce from the breath of some 390 billion trees. Rivers snake their way through what appears to be a sea of endless green.
Yet satellite images taken over the past several decades reveal that more than 75% 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 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.
Yet human-caused warming and deforestation have hijacked this self-reinforcing system. Hotter conditions in the Atlantic Ocean have extended the Amazon’s dry season by several weeks. By felling 17% of its trees, people have undercut the forest’s water recycling mechanism.