The Amazon rainforest is losing its ability to recover from destruction, and parts of it are approaching “a catastrophic tipping point”, warns a leading scientist after a new study using two decades of satellite data.
The research found that in more than three-quarters of the world’s largest rainforest its resilience to damaging events, such as droughts or fires, had declined consistently since the early 2000s.
The study by Exeter university, the Potsdam Institute and Munich technical university used satellite information to track changes over 25 years to examine how the Amazon’s vegetation had responded to fluctuating weather conditions.
Any transformation of the Amazon into a hotter, drier grassland would bring major consequences for global climate change because of the disappearance of carbon-storing trees and potential increases in fires. Droughts would probably become even more frequent and severe across South America.
“It’s alarming to think where we’re getting the evidence now to confirm we’re heading towards the potential abrupt loss of this ecosystem,” said Tim Lenton, director of the Global Systems Institute at Exeter university and a global expert on climate tipping points.
A tipping point is defined as the stage when feedback loops, or cycles of cause and effect, become so strong they start propelling themselves independently of the initial cause, triggering the system to change state. This is often irreversible.
In the Amazon, the cycle is set off by the logging of trees that reduces moisture levels in the rainforest, and in turn results in the further loss of trees because of the lack of rainfall to sustain them.
This vicious cycle is then amplified by warming temperatures and a drier climate in the entire region. The tipping point would occur when the rainforest ecosystem could no longer regenerate itself, collapsing irreversibly instead into a dry savannah.
“Take one or several trees out and then it causes a change that takes out just as many trees again, and again, and you can’t stop it,” Lenton said.
The study is the latest of multiple scientific warnings that large parts of the Amazon could soon experience widespread dieback. Some experts estimate that the tipping point is 10 to 20 years away, based on present deforestation and global warming rates. Temperatures have already risen by at least 1.1C since the pre-industrial era.
“I’m already a seriously concerned scientist about the risks from several climate tipping points,” Lenton said. “This one is almost more emotive to me because this isn’t just a crucial part of the climate system and a massive store of carbon. This is an incredible crucible of biodiversity and it’s home to some very special indigenous human populations as well.”
The researchers said the Amazon’s resilience had dropped particularly during two “once-in-a-century” droughts, in 2005 and 2010. Average rainfall in the Amazon had not recently changed drastically in spite of climate change, they said, but dry seasons had lengthened and droughts had become more severe.
Resilience is being lost faster in parts of the Amazon nearest to human activity, the study found. “This gives new compelling evidence to support efforts to reverse deforestation and degradation,” said Lenton.