Amazon rainforest reaching tipping point

The Amazon rainforest is moving towards a "tipping point" where trees may die off en masse, say researchers.

A study, published in Nature Climate Change, suggests the world's largest rainforest is losing its ability to bounce back from damage caused by droughts, fires and deforestation. Large swathes could become sparsely forested savannah, which is much less efficient than tropical forest at sucking carbon dioxide from the air.

The giant forest traps carbon that would otherwise add to global warming. But previous studies have shown that parts of the Amazon are now emitting more carbon dioxide than can be absorbed.

Deforestation in the Amazon has hit record levels (Daniele Gidsicki / commons.wikimedia.org).

"The trees are losing health and could be approaching a tipping point – basically, a mass loss of trees," said Dr Chris Boulton of the University of Exeter. The findings, based on three decades of satellite data, show alarming trends in the "health" of the Amazon.

There are signs of a loss of resilience in more than 75% of the forest, with trees taking longer to recover from the effects of droughts largely driven by climate change as well as human impacts such as deforestation and fires.

A vicious cycle of damage could trigger "dieback", the scientists said. And while it's not clear when that critical point might be reached, the implications for climate change, biodiversity and the local community would be "devastating".

Once the process begins they predict it could be a matter of decades before a "significant chunk" of the Amazon is transformed into savannah – a vastly different ecosystem made up of a mixture of grassland and trees.

"The Amazon stores lots of carbon and all of that would be released into the atmosphere, which would then further contribute to increasing temperatures and have future effects on global mean temperatures," Dr Boulton said, adding that stopping deforestation would go some way to addressing the problem. Around a fifth of the rainforest has already been lost, compared to pre-industrial levels, they said.

The research was carried out by the University of Exeter, the Potsdam Institute for Climate Impact Research (PIK) and Technical University of Munich.

Reference

Boers N, Boulton A & Lenton T. 2022. Pronounced loss of Amazon rainforest resilience since the early 2000s. Nat. Clim. Change. DOI: doi.org/10.1038/s41558-022-01287-8