It was once considered the “lungs of the earth,” a valuable carbon sink and a key tool to reel in rising carbon dioxide (CO2) emissions levels in the face of climate change. But now, the Amazon Rainforest is reversing course, a swath of it emitting more CO2 than it is able to absorb, according to research published yesterday in the journal Nature.
Much of these emissions come from forest fires, the researchers behind the study found—but drought and rising temperatures also play a role, creating carbon-emitting biomass and reducing the Amazon’s ability to serve as a sink for greenhouse gases.
The study confirms what many have long predicted, but none had yet empirically found. The team of 19 researchers, many based out of the Brazilian National Institute of Space Research (INPE), sent 590 aircrafts over the rainforest between 2010 and 2018 to collect air samples from four locations throughout the forest, which they tested for carbon dioxide and monoxide levels. They found that Amazon forest fires produced around 1.5 billion tons of carbon dioxide annually, while trees only absorbed half a billion.
Emissions were three times higher in regions where the Amazon has seen forest fires than in regions where it hasn’t, Luciana Gatti, a researcher at INPE and first author on the study, told The Guardian Wednesday. They were also 10 times higher in regions where at least 30 percent of the land has been deforested than in regions where clear-cut rates were less than 20 percent, she said. While all regions the researchers sampled saw emissions from fires, the southeast region was the only one found to have turned into a carbon source, rather than a store. It’s also a region where dry conditions, spurred on by warming temperatures and reduced rainfall, have turned a growing amount of the forest into savannah, leading to tree decomposition and fires, both carbon emitters.
“We have a very negative loop that makes the forest more susceptible to uncontrolled fires,” Gatti told The Guardian. “We need a global agreement to save the Amazon.”
Broadly speaking, trees play a valuable role in sequestering carbon from the atmosphere through the process of photosynthesis, which requires carbon dioxide and water to generate glucose (used for plant energy) and oxygen. This carbon is then stored in soil and forest biomass which is made up of organic matter, like branches, roots, and leaves, both living and dead.
The world’s forests are responsible for absorbing an estimated 16 billion tons of climate change-contributing carbon dioxide from the atmosphere per year. But despite being the largest rainforest in the world, the Amazon’s contribution to this global effect has long been understood to be on the decline.
A forest is considered a carbon source if it emits more through wildfire and tree decay than it takes up through living trees and photosynthesis. And that’s what’s occurring in the Amazon, in part by design. Widespread and long-burning fires are not a natural part of the Amazon ecosystem, but human influence has changed that. Brazil President Jair Balsonaro, a well-known friend to the agribusiness lobby, has vigorously promoted logging in the rainforest since taking office in 2019; the same year saw the largest swath of Amazonian land razed since 2008, as a landmass seven times larger than Greater London was destroyed, the Guardian reported at the time.
Estimated forest cover in the Amazon has declined by around 20 percent since pre-1970 levels, according to data by the INPE. And while clear-cutting rates have fluctuated year-over-year in that time, they’ve been fairly steadily on the up since 2012, even as knowledge of the role trees play in mitigating climate change has grown.