In July 2019, about 30 scientists from around the world gathered in Manaus, Brazil. Their goal was to map out all of the ways the Amazon absorbs and releases greenhouse gases. In a new study published Thursday, they found something startling: The Amazon may emit as much as or more than it sequesters. Thanks in large part to human decisions, one of the greatest rain forests left on earth may now actually be warming the planet.
Forests, when they are working well, are miraculous carbon-reducing machines. You may recall seeing a diagram of this in a school textbook: the trees pulling carbon dioxide from the atmosphere, transforming the carbon into wood and releasing oxygen in the process.
But in any ecosystem, particularly one as vast and diverse as the Amazon, there aren’t just undisturbed trees—there is soil and water and air, all with their own complicated processes of sequestering and emitting. Trees themselves don’t put out only oxygen; they can also release methane and something called biogenic volatile organic compounds. By looking primarily at carbon sequestration and emissions, the team of scientists concluded in this recent study, we’ve been missing the bigger picture, including other powerful and long-lasting greenhouse gases being released from the Amazon because of human activities like logging, mining, farming, and setting fires.
“If you’re only looking at the carbon picture, you’re missing a big part of the story,” Kristofer Covey, lead author of the report and a visiting assistant professor at Skidmore College, told me. “We need to start understanding the full complexity of this ecosystem. We’re down there tinkering at a massive scale, and we don’t really understand the full implications of what we’re doing.”
When you set fire to trees, for instance, as part of slash-and-burn farming or ranching, you’re not just getting rid of a carbon-sucking machine. You’re releasing methane, which is 84 times more potent than carbon dioxide and lingers in the atmosphere for a dozen years. You’re changing the color of the earth’s surface from green to brown or black, which affects how the earth absorbs rather than reflects the sun’s rays. And you’re spraying black carbon into the atmosphere, which changes its reflectivity and traps more heat. All of these factors, the researchers found, work together in extremely complex and little-understood ways.
“When we look at the scale of the Amazon basin, it’s pretty likely that the net effect of all of this is that the Amazon is warming the earth’s atmosphere,” Covey said. Because of massive deforestation, the Amazon is not the carbon sink it once was, so the balance of emissions is now thrown off. “If we had an intact ecosystem that was still doing this enormous carbon service, this would be a much closer call,” Covey said. But the authors also realized that there is much they still need to learn about how these other factors—like emissions of methane, nitrous oxide, black carbon, and aerosols—work together, and the extent of the benefits they offer or the damage they cause.
“It is an important step. But I think it’s just the start,” said Dr. Bernardo M. Flores, a researcher at Federal University of Santa Catarina in Brazil, who was not involved with the study. “It’s great to show what we know so far.” Feedback loops are a particular concern that can be difficult to follow and understand. Changes in forest cover, for example, can change rainfall patterns and then the risk of fires—thus changing forest cover even more.
In 2018, researchers introduced the concept of a “tipping point“ in the Amazon—the point at which forest losses become irreversible. “We’ve not crossed that threshold,” Covey said. “If we do, we’re going to know about it, and it’s not going to be pretty.” But to make matters worse, he said, “you don’t figure out exactly where that line is until you’re on the wrong side of it.”
There’s another important takeaway from this new study: the limitations of relying on carbon sinks like the Amazon in addressing climate change. Right now, many climate plans from both corporations and governments rely on carbon capture or sequestration to reach what’s known as “net-zero”: In other words, they reduce emissions by a certain amount and then depend on planting trees or new technology to suck extra greenhouse gases from the air to get the rest of the way. As critics have pointed out in the past year, though, it’s not clear that we can rely on this strategy, because pulling carbon from the air, whether through natural or technological means, is easier said than done.
This new study is another big warning sign. “We can get a lot of services out of forests; we already get a lot of services out of forests. But we can’t always count on them to fix everything for us,” he said. Instead, we will have to find other ways to reduce greenhouse gases in the atmosphere—by emitting fewer of them, for instance. We must protect and restore the Amazon, but it can’t be our only hope. “We might need to think very carefully about the trade-offs between emissions and natural climate solutions,” Covey said. “We have this expectation that the lungs of the planet are taking care of it. And at the same time, we’ve been really degrading that service for a long time.”
Recent political developments haven’t helped. “Between 2005 and 2012, Brazil was a global example of a country showing that we can stop deforestation or reduce it drastically,” Flores said. But deforestation has increased dramatically under the administration of current President Jair Bolsonaro. “Now we’re having what is going to be the worst deforestation in 10 years,” Flores said. “We can go back to doing the right thing. But now, the situation with the government seems a bit difficult.”
To a certain extent, policymakers’ desire to develop the country by capitalizing on the forest’s vast resources makes sense. For decades now, richer nations have gotten ahead by recklessly polluting far more than the rest of the world. That’s one of the reasons behind calls for climate reparations and adequately compensating nations with vast natural reserves for not developing them. However, much of the deforestation in the Amazon and other rain forests in the past few years has flouted the law, coming explicitly at the expense of Indigenous communities and their land rights. A change in governance could help. Recently, former President Luiz Inácio Lula da Silva, who had an impressive environmental record during his term, was cleared of corruption charges, allowing him to challenge Bolsonaro, a climate denier openly contemptuous of Indigenous rights, in the elections.
Degrading the Amazon is kind of like balancing a bank account, Covey said. By clearing out forests that serve as a massive sink not just for carbon but for other greenhouse gases, “you’re losing income and doing a lot of spending out of your accounts at the same time,” he said. Now, as researchers discover other potentially significant sources of emissions, “we may have a whole bunch of expenses on the forest books that we haven’t accounted for.” Instead of looking to rain forests in terms of capitalistic resources—timber, gold, beef, crops—we should value the important services these intact ecosystems offer, he said, and start “paying the real cost of degrading the Amazon.… People will pay the cost down the line. There’s no avoiding the check coming due. But I think if we’ve focused attention on any one thing in the past year, it’s that not everybody’s going to pay those costs equally.”
Those who depend upon the Amazon more directly, such as the Indigenous people who have coexisted peacefully with the land for centuries, stand to lose the most. But the entire world will suffer if the Amazon is destroyed. What this new study shows, above all, is that we’re dangerously close to finding out what that would look like.