Climate change to fuel fires in the Amazon rainforest

In 30 years, the burned surface of the Amazon rainforest will have bent. A study that starts from the evolution of fires so far this century shows that the outcome of the interaction of deforestation and climate change will be a greater number of fires even more devastating. As a result, much of the Amazon region will become a net greenhouse gas broadcaster that would, in turn, feed back the process. Experts are beginning to talk about a point of no return and the sabanization of the Amazon.

Brazilian and American researchers have modeled the evolution of fires on nearly 200 million hectares of the southern and southeastern portions of the Legal Amazon. In the model they integrated the number of fires and their main characteristics (moment of ignition, duration, burned area...) with the evolution of deforestation and climate change between 2000 and 2050. Both processes are independent but, combined, affect the quantity and severity of fires, as this work shows, published in Science Advances.

In the worst of the expected emission scenarios and maintaining the current rate of deforestation, relatively low (compared to 2000), the severity of the fires will intensify. In an expected context of higher temperature and lower humidity, the dry season will lengthen, exacerbating the conditions for ignition. By 2050, according to this study and in this scenario, up to 15 million hectares of rainforest will have been burned,

Rising temperatures and lower humidity will raise the flammability of the forest

But it is in combination with deforestation that climate change will spark fire to threaten what has been the Amazon in the last 55 million years. In a context of high greenhouse gas (GHG) emissions and increased regional warming, the intensification of tree felling will expose the rest of the forest. The study estimates that, in this scenario, hectares burned in 2050 will rise to 22 million,

Among the synergies between climate change and logging that explain this increase in the burned area is a widespread increase in forest flammability. The edges and edges of the forest, more exposed, will have increased. In cleared forests, the increased solar radiation reduces moisture, the main natural firefighter. And a less humid environment facilitates the onset and spread of a fire and complicates its extinction. Besides, what's in the jungle will make it more difficult to recover,

"Our projections point to an acceleration of fire activity in the southern Amazon," the study authors conclude, adding, "We show that up to 16% of the region's jungles could burn as the climate gets drier and warmer in a few decades.

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A paradoxical effect of these projections has to do with GHG emissions. The Amazon rainforest is the main CO2 sink on the Earth's surface. The fires could upset their balance. According to this research, and in the worst climate and deforestation scenario, the burning of the sixth part of the Amazon will release by 2050 more than 17 billion tons of CO2 into the atmosphere, making much of the South and Southeast Amazonians net emitters of GHG.

Up to 60% of the forest could degenerate into savannah by the end of the century

"Under normal conditions, tropical forests such as the Amazon are very humid, short dry season and very fire resistant", recalls the researcher at the Institute of Advanced Studies at the University of Sao Paulo (Brazil) Carlos Nobre. "However, climate change has generalized higher temperatures and more extreme droughts everywhere, including in the Amazon. Along with the degradation of the human-caused tropical forest and the intensive use of fire in tropical agriculture and to clear new ranches and farmland, all this makes today's Amazon rainforest exponentially more vulnerable to fires than in the past," adds Nobre, unrelated to this study

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Fire thus joins the cocktail that threatens to change forever what the Amazon is. "We are very close to reaching a point of no return in the sabanization large portions of the Amazon rainforest," says Nobre, who wrote an editorial about this risk in the journal Science Advances last month. "If we exceedthis point of no return, more than 60% of the Amazonian forests would become a tropical dry savannah. What was left of the forest would be limited to the western portion of the Amazon basin, at the foot of the Andes. The south, east and northeast of the Amazon rainforest could disappear," he warns,