Climate change could turn Amazon forest into a carbon source: Scientists

Climate change will likely intensify fires in the Amazon rainforest, which could turn it from a carbon sink into a carbon source, scientists have warned, reports Newsweek.

Some 16 percent of the forest in the southern Brazilian Amazon may burn by 2050 "as the climate becomes drier and hotter in the next few decades," according to the authors of a study published in the journal Science Advances. That amounts to global warming doubling the area burned by wildfires in this region in the next three decades, they fear.

The authors of the paper used regional climate projections to create a model to predict the future of wildfires in the southern Brazilian Amazon. The area they looked at covered 192 million hectares in the driest part of the forest. Of that, 72 percent featured native forests, while deforested area were mainly used for cattle ranches, followed by mechanised agriculture.

The study comes after what is the world's largest tropical forest hit headlines over the summer, as scenes of raging wildfires fires and deforestation shocked the world.

Data suggests the carbon dioxide which has already been released into the atmosphere has likely already doomed the region to "substantial warming and drying," which will in turn likely intensify fires, the authors said.

The team explained deforestation declined by 70 percent in the Amazon between 2004 and 2014, preventing the equivalent of 12 percent of global annual global carbon dioxide emissions from being released. Despite that, forest fires have gotten bigger thanks to human activities and extreme weather, and are sending up more carbon into the atmosphere.

Changing temperature and rainfall levels in the forest could push the forest into a new low-biomass state, the researchers said. The burning would likely in turn spew large amounts of greenhouse gases into the atmosphere, and speed up global warming, they warned.

"Ignoring this potentially large source of GHG [greenhouse gas] emissions to the atmosphere may restrict our ability to mitigate climate change and, consequently, undermine effective conservation of Amazon forests," the authors wrote.

However, the researchers also provided a glimmer of hope. If new deforestation is avoided, net greenhouse gas emissions released by fires could be cut in half, and fires prevented from spreading to protected areas and indiginous lands, they believe. Besides, getting the levels of global greenhouse gas emissions down to almost zero may cut the risk of severe droughts, which are linked to wildfires. Up to 30 percent of the forest could be saved from being burned, and greenhouse gas emissions released by fires reduced by 56 percent.

"Wildfires, exacerbated by extreme weather events and land use, threaten to change the Amazon from a net carbon sink to a net carbon source," scientists wrote. "Aggressive efforts to eliminate ignition sources and suppress wildfires will be critical to conserve southern Amazon forests," they said.

Co-author Paulo Brando, assistant professor at the UCI department of earth system science, told Newsweek: "The major surprise was that even if our society sharply reduces greenhouse gas emissions to the atmosphere, there will likely be consequences for fires in the Amazon no matter what, but especially if we keep deforestation business as usual.

"The other surprise was the increased vulnerability of protected forests to fire in the near future. During decades, those forests' main protection against fire was the moist, humid microclimatic underneath the thick canopies. But with climate change, our model projects those canopies to become thinner, allowing dryness to take down that protection."

Brando said the main limitation of the study was the challenge of projecting future deforestation rates, as policy and economic decisions across the globe can "rapidly" change them.

Carlos Nobre, the National Secretary for Research and Development Policy in the Ministry of Science, Technology and Innovation of Brazil and an expert in climate change and the Amazon rainforest, told Newsweek the authors used a "state-of-the-art" model in their study.

But he pointed out that the work did not deal with the fact there was higher than average rainfall and floods in 2009 and 2012.

"What impact would that have in diminishing the increased vulnerability of the forests to fires in the future if one would see not only an increase of extreme droughts, but also an alternation of increased severity of droughts and floods?" he asked.

He went on: "This year we had a peak of fires, burned forest areas and deforestation, but it was not a drought year. It [the study] highlights the impact of human induced fires and the need to eliminate most of those.

"On the time scale of decades, it also shows that continued climate change will make the Amazon a net carbon source, if we failed to cut deforestation and the use of fires in agriculture and cattle ranching."

Professor Bruno De Faria, of Brazil's Federal Institute of Technology North of Minas Gerais, told Newsweek: "the article looks only until 2050 and we know that the biggest changes are likely to occur after 2050."