The Amazon rainforest is teetering on the precipice of a dangerous tipping point, new research warns. It’s gradually losing its ability to bounce back after disturbances like droughts or other extreme weather events.
With enough time and forest losses, scientists say, large swaths of the Amazon could fall into an unstoppable spiral that would transform them from lush rainforest into grassy savanna.
The global implications would be profound. The loss of the rainforest would cause a large-scale drying across the region. The circulation of the atmosphere could change in response, altering weather patterns around the world.
And the Amazon has the potential to pour some 90 billion metric tons of carbon dioxide into the atmosphere as the forest dies off, the equivalent of several years of human-caused greenhouse gas emissions.
“It’s worth reminding ourselves that if it gets to that tipping point and we commit to losing the Amazon rainforest, then we get a significant feedback to global climate change,” said Timothy Lenton, a scientist at the University of Exeter and a co-author of the study, published yesterday in Nature Climate Change.
Scientists have warned of an Amazon tipping point for years. Computer models and simulations have frequently shown that with enough future warming, the rainforest could eventually enter an irreversible transition to a new kind of ecosystem.
Now, the new study adds extra urgency to the situation. It demonstrates, with real-life observations, that the Amazon is already losing its resilience. In fact, it has been for years.
The research draws on three decades of satellite data, monitoring the way trees and other vegetation recover after damaging weather events, droughts or other disturbances. The findings are stark: The Amazon has been losing its resilience for at least 20 years. The majority of the areas observed recover more slowly today than they did a couple of decades ago.
Drier parts of the Amazon seem to be faring worse, the research reveals, along with areas located closer to human activities. Declining rainfall, increasing drought and deforestation are chipping away at the rainforest’s strength to recover.
How long it can keep holding on is the million-dollar question. The new study shows that an irreversible tipping point is inching closer — but it hasn’t arrived. And it’s still unclear how long it might take to get there.
Once the threshold is actually crossed, though, the transformation of the Amazon could occur swiftly.
As the forest begins to die off, it may enter a reinforcing cycle. With fewer trees, the region will grow even drier. More droughts will cause more trees to die. Wildfires may also grow more severe, wiping out huge tracts of forest at a time.
“Once it starts, my sense is it could happen in decades,” said Chris Boulton, a scientist at the University of Exeter and lead author of the new study.
‘There is still hope’
The Amazon rainforest is just one of many possible tipping points in the Earth’s climate system.
Scientists have warned, for instance, that the Greenland and Antarctic ice sheets may have their own dangerous thresholds — that enough future warming could cause rapid, unstoppable ice loss and the risk of catastrophic ice sheet collapse. In such a scenario, the effects on global sea levels would be apocalyptic.
Studies have also suggested that one of the world’s largest ocean currents, the Atlantic Meridional Overturning Circulation, is slowing down as the planet warms. The AMOC helps ferry heat between the equator and the Arctic and plays an important role in regulating climate and weather patterns throughout the Northern Hemisphere. Some experts have warned that the current may also have a tipping point, beyond which it could collapse entirely.
A recent report from the Intergovernmental Panel on Climate Change notes that there’s a lot of uncertainty about the Earth’s tipping points and a lot of debate about how much warming it would take to actually cross them (Climatewire, Aug. 12, 2021). While none of these scenarios can be completely ruled out, some of them present more immediate concerns than others.
Scientists generally agree that the ice sheets will likely melt at faster and faster rates in the coming decades, a growing concern for global sea-level rise. But catastrophic ice sheet collapse is highly unlikely anytime within the next 100 years. Similarly, the AMOC is expected to keep on slowing, but is unlikely to be at risk of collapse in this century.
The Amazon’s near-term future, on the other hand, is the subject of greater speculation.
The IPCC report notes that the combination of continued warming and deforestation could put the Amazon at risk of reaching its tipping point before the end of this century. But it also notes that there’s still a lot of debate about that. Modeling studies have tended to disagree about where the threshold lies.
The new study doesn’t make any concrete predictions about it.
“We can’t turn this into a definitive forecast of when the tipping would happen,” Lenton said.
The study simply points out that the warning signs are already there. The Amazon isn’t recovering as quickly as it used to, which means it’s more vulnerable to the kinds of disturbances that may eventually cause it to start rapidly dying off.
There’s some good news mixed in there, according to the authors. The tipping point hasn’t arrived yet, which means there’s still time to work on saving the Amazon. And the research holds some important, if unsurprising, clues about how to do it.
Curbing global climate change is key. Slowing down the warming can help mitigate the droughts, wildfires and other disasters that are damaging the rainforest.
And halting deforestation is crucial. The study demonstrates that human land use is taking a clear toll on the Amazon.
“The resilience loss that we observed means that we have likely moved closer to that critical point, to that tipping point,” said Niklas Boers, a modeling scientist at the Technical University of Munich and another co-author of the new study. “It also suggests we haven’t crossed that tipping point yet, so there is still hope.”
Reprinted from E&E News with permission from POLITICO, LLC. Copyright 2022. E&E News provides essential news for energy and environment professionals.