The Brazilian Amazon rainforest, victim of climate change and human activities, has rejected, over the past ten years, more carbon than it has absorbed, a major and unprecedented shift, according to a study published Thursday, April 29 by a team international in the scientific journal Nature Climate Change.
Without forests – which absorb between 25 and 30% of greenhouse gases emitted by humans – climate change would be much worse. For several years, scientists have been worried about the loss of steam in tropical forests and fear that they may less and less play their role as carbon sinks. The concern comes in particular from the Amazon rainforest, which represents half of the tropical forests on the planet.
The study published in Nature Climate Change looks at the Brazilian Amazon, which represents 60% of this primary forest. And the picture is grim. Between 2010 and 2019, this forest lost its biomass: the carbon losses of the Brazilian Amazon are about 18% greater than the gains, said in a statement the French Research Institute for Agriculture, Food and the environment (Inrae).
Amazonia, the last bulwark
“This is the first time that we have figures which show that we have switched and that the Brazilian Amazon is emitting” net of carbon, explains one of the authors, Jean-Pierre Wigneron, researcher at INRAE. For now, a priori, “The other countries compensate for the losses of the Brazilian Amazon” and “The whole of the Amazon has not yet changed, but it could do so soon”, continues the researcher, who warns:
” Until now, (…) the tropical forests protected us by making it possible to slow down the warming, but our last bulwark, the Amazonia, is in the process of toppling. “
In addition, the study highlights the unrecognized, but major, responsibility of “Degradations” of the forest. Unlike deforestation, which causes the wooded area to disappear, degradation includes everything that can damage it, without however completely destroying it: weakened trees on the edge of deforested areas, selective cutting, small fires or even tree mortality linked to Drought. Damages which are less easily detectable than large areas razed to the ground.
Using a vegetation index from microwave satellite observations, making it possible to probe the entire vegetation layer and not just the top of the canopy, the study concludes that these forest degradations have contributed to 73% of carbon losses, against 27% for deforestation, which is however large.
