Amazon rainforest nearing tipping point to shift to savannah, new study suggests

The fate of the rainforest is critical to the health of the planet as it is home to a unique diversity of animal and plant life, stores vast amounts of carbon and strongly influences global weather patterns.

Scientists say about three-quarters of the rainforest shows signs of “loss of resilience” — a reduced ability to adapt to disturbances such as droughts, deforestation and fires. Their study is based on monthly observations of satellite data over the past 20 years, which have mapped the forest’s biomass (the area’s organic matter) and greenery to show how it has changed in response to fluctuating weather conditions.

This declining resilience since the early 2000s is a warning sign of irreversible decline, the authors say. While it’s not possible to say exactly when the transition from rainforest to savanna might occur, once it became obvious, it would be too late to stop.

“It’s worth remembering that if we come to this tipping point and commit to losing the Amazon rainforest, we will have a significant feedback on global climate change,” says Timothy M. Lenton, one of the authors oneNew study and a director of the Global Systems Institute at the University of Exeter in the UK, in a press conference.

“We’re losing about 90 billion tons of carbon dioxide, mostly in the trees but also in the soil (of the Amazon),” Lenton said.

When the Amazon ceases to be a rainforest, it won’t store as much carbon.

Aerial view showing a boat speeding on the Jurura river in the municipality of Carauari, in the heart of Brazil's Amazon forest, March 15, 2020.
previous studies have come to similar conclusions about an ecological point of no return for the Amazon rainforest based on computer simulations — but the authors said their research, published Monday in Nature Climate Change, uses real-world observations.

Once we hit the tipping point, the authors said the rainforest could disappear pretty quickly. “My guess, for what it’s worth, (is that) it could happen within decades,” Lenton said.

The study found that resilience loss was most severe in areas closer to human activity, as well as areas with less rainfall. The study also found that loss of resilience does not equate to loss of forest cover – meaning that without clearly identifiable changes, the rainforest could be close to the point of no return.

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Chantelle Burton, a senior climate scientist at the Met Office Hadley Center in the UK, said it was questionable how the Amazon rainforest would withstand the challenges of climate change, land-use change and fires. She said this new study is “really important.”

“What this study is doing is providing some observational evidence of what is already happening with this major carbon sink, and it shows that human land use and changes in weather and climate patterns are already driving an important change in the system,” said Burton, who was not involved in the research, said the Science Media Center in London.

“Crossing such a tipping point would make it even more difficult to achieve our goal of net-zero global emissions by losing the Amazon carbon sink ‘free service’ that currently removes some of our emissions.”

Richard Allan, a professor of climate science at the University of Reading, said the study was a “comprehensive and rigorous assessment of the Amazon’s sustainability.”

“It comes to the tantalizing conclusion that much of the Amazon is showing signs of approaching a tipping point toward irreversible decline; but since multiple satellite sensors are used to infer vegetation ‘lushness’, we must rely on these data records to show accurate trends,” Allan was quoted as saying in the SMC statement.

“In any case, it is undeniable that human activity is waging a multi-pronged war of attrition against nature, although fortunately the solutions in this case are known: halting deforestation while rapidly and massively reducing greenhouse gas emissions.”

https://www.cnn.com/2022/03/07/americas/amazon-tipping-point-climate-scn/index.html Amazon rainforest nearing tipping point to shift to savannah, new study suggests

Charles Jones

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