Nature: Trouble in the Amazon The rainforest is starting to release its carbon. Is it heading towards a tipping point?

24 August 2023 By Daniel Grossman; Photographs by Dado Galdieri/Hilaea Media for Nature; Video by Patrick Vanier/Hilaea Media for Nature

Climate change, deforestation and other human threats are driving the Amazon towards the limits of survival.

Researchers are racing to chart its future.

“Luciana Gatti stares grimly out of the window of the small aircraft as it takes off from the city of Santarém, Brazil, in the heart of the eastern Amazon forest. Minutes into the flight, the plane passes over a 30-kilometre stretch of near-total ecological devastation. It’s a patchwork of farmland, filled with emerald-green corn stalks and newly clear-cut plots where the rainforest once stood.

“’This is awful. So sad,’ says Gatti, a climate scientist at the National Institute for Space Research in São José dos Campos, Brazil.

“Gatti is part of a broad group of scientists attempting to forecast the future of the Amazon rainforest. The land ecosystems of the world together absorb about 30% of the carbon dioxide released by burning fossil fuels; scientists think that most of this takes place in forests, and the Amazon is by far the world’s largest contiguous forest.

“Since 2010, Gatti has collected air samples over the Amazon in planes such as this one, to monitor how much CO₂ the forest absorbs. In 2021, she reported data from 590 flights that showed that the Amazon forest’s uptake — its carbon sink — is weak over most of its area¹. In the southeastern Amazon, the forest has become a source of CO₂.

The finding gained headlines around the world and surprised many scientists, who expected the Amazon to be a much stronger carbon sink. For Carlos Nobre, a climate scientist at the University of São Paulo Institute of Advanced Studies in Brazil, the change was happening much too soon. In 2016, using climate models, he and his colleagues predicted that the combination of unchecked deforestation and global climate change would eventually push the Amazon forest past a “tipping point”, transforming the climate across a vast swathe of the Amazon². Then, the conditions that support a lush, closed-canopy forest would no longer exist. Gatti’s observations seem to show the early signs of what he forecast, Nobre says.

“’What we were predicting to happen perhaps in two or three decades is already taking place,’ says Nobre, who was one of a dozen co-authors of the paper with Gatti.

“I’ve travelled to Santarém, where the Tapajós River joins the Amazon River, to join Gatti and other scientists trying to determine whether the forest is heading for an irreversible transformation towards a degraded form of savannah. Another big question is whether the forest can still be saved by slowing climate change, halting Amazon deforestation and restoring its damaged lands, something Nobre suggests is possible…

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