Tropical forests could lose their role as major carbon store if the daytime temperature exceeds 32 ° C, a situation that would affect almost three quarters of these forests if global warming reaches 2 ° C, according to a study published Thursday in Science .
“Tropical forests currently store the equivalent of a quarter of a century of carbon dioxide emissions. However, global warming risks reducing this stock if the growth of trees decreases or if the mortality rate of trees increases, accelerating climate change at the same time , " according to a press release from CIRAD, which participated in this study. having mobilized 225 researchers.
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Researchers measured more than half a million trees in 813 rainforests around the world to assess the amount of carbon stored. Currently, tropical forests play their role as carbon sinks, "despite the rise in temperatures," the statement said.
But “the carbon stock contained in these forests remains stable up to a threshold daytime temperature of 32 ° C. Beyond this threshold, this stock decreases very sharply, ” according to Bruno Hérault, co-author of the study, and specialist in tropical forests in the Forests and Companies unit at CIRAD (Center for International Cooperation in Agronomic Research for Development) .
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The current objective set by the Paris Agreement to keep global warming below 2 ° C "would amount to exceeding these 32 degrees for a large number of tropical forests".
"If we limit global average temperatures to an increase of 2 ° C compared to pre-industrial levels, this pushes nearly three quarters of tropical forests above the temperature threshold that we have identified," warns Martin Sullivan, the author principal of the publication, researcher at the University of Leeds and the Metropolitan University of Manchester, cited in the press release.
The danger would then be "that forests, in turn, emit carbon". "Each degree of temperature increase would release 51 billion tonnes of CO2 from tropical forests into the atmosphere," says Martin Sullivan.