In 30 years, the burned area of the Amazon rainforest will have doubled. A study based on the evolution of fires so far this century shows that the result of the interaction of deforestation and climate change will be a greater number of even more devastating fires. As a consequence, a large part of the Amazon region will become a net emitter of greenhouse gases which, in turn, will feed back into the process. There are experts who are beginning to speak of a point of no return and the savannah of the Amazon.
Brazilian and US researchers have modeled the evolution of fires in almost 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 (timing of ignition, duration, burned area…) with the evolution of deforestation and climate change between 2000 and 2050. Both processes are independent but, combined, they affect the number and severity of the fires, as shown in this work, published in Science Advances.
In the worst of the forecast 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 conditions for ignition. In 2050, according to this study and in this scenario, up to 15 million hectares of forest will have been burned.
Rising temperatures and lower humidity will increase the flammability of the forest
But it is in combination with deforestation that climate change will stoke the fire until it threatens what the Amazon has been for the last 55 million years. In a context of high greenhouse gas (GHG) emissions and increased regional warming, intensified logging will expose the rest of the forest. The study estimates that, in this scenario, the hectares burned in 2050 will rise to 22 million.
Among the synergies between climate change and logging that explain this increase in the area burned is a general increase in the flammability of the forest. The edges and edges of the forest, more exposed, will have increased. In cleared forests, higher solar radiation reduces humidity, the main natural firefighter. And a less humid environment facilitates the start and spread of a fire and complicates its extinction. In addition, what remains of the jungle will have a more difficult time recovering.
“Our projections point to an acceleration of fire activity in the southern Amazon,” the authors of the study conclude, adding: “We show that up to 16% of the region’s forests could burn as climate it’s getting drier and warmer over a few decades.”
A paradoxical effect of these projections has to do with GHG emissions. The Amazon rainforest is the main sink for CO2 what is on the earth’s surface. The fires could upset its balance. According to this research, and in the worst climate and deforestation scenario, the burning of a sixth of the Amazon will release more than 17,000 million tons of CO by 20502 into the atmosphere, turning a large part of the southern and southeastern Amazon into 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 like the Amazon are very humid, have a short dry season and are very resistant to fire,” recalls Carlos Nobre, a researcher at the Institute for Advanced Studies of the University of São Paulo (Brazil). “However, climate change has led to higher temperatures and more extreme droughts everywhere, including in the Amazon. Together with human-caused degradation of the tropical forest and the intensive use of fire in tropical agriculture and to clear new ranches and farmland, all of this makes today’s Amazon rainforest exponentially more vulnerable to fire than in the past,” adds Nobre, unrelated to this study.
Fire thus joins the cocktail that threatens to change what the Amazon is forever. “We are very close to reaching a point of no return in savannah of large portions of the Amazon rainforest,” says Nobre, who wrote an editorial about this risk in the magazine Science Advances last month. “If we pass this point of no return, more than 60% of the Amazonian forests would become a tropical dry savannah. What remains of the forest would be limited to the western portion of the Amazon basin, at the foot of the Andes. south, east and northeast of the Amazon forest could disappear,” he warns.