Scientists have predicted for years that at some point the Amazon rainforest, known as “the lungs of the planet,” would be overcome in its ability to scrub carbon dioxide from the atmosphere and could even emit more greenhouse gases than it absorbs.
Now, a new study says, it’s probably already happened.
The research, published Thursday in the journal Frontiers in Forests and Global Change, looked at several factors at play in the Amazon, including fires, deforestation, weather and the expansion of ranching. It concludes that greenhouse gases including methane and nitrous oxide being emitted in the Amazon basin offset and most likely exceed the region’s ability to soak up carbon dioxide.
The Amazon’s declining ability to absorb carbon has been widely studied, in particular when it comes to deforestation. But this is the first report to look at a broader picture of the cumulative effects from both human and natural activities that contribute to global warming, according to National Geographic, which supported the research.
“Cutting the forest is interfering with its carbon uptake; that’s a problem,” lead author Kristofer Covey, a professor of environmental studies at New York’s Skidmore College, said. “But when you start to look at these other factors alongside CO2, it gets really hard to see how the net effect isn’t that the Amazon as a whole is really warming global climate.”
Among the other factors: Logging can increase emissions of nitrous oxide, fires release black carbon, deforestation can alter rainfall patterns and ranching leads to methane production.
Carbon dioxide, or CO2, is a greenhouse gas that results mostly from the burning of fossil fuels. Greenhouse gases absorb heat and then release it into the atmosphere, fueling higher temperatures that cause global warming and climate change, according to NOAA.
Tropical forests, including those in the Amazon, act as “carbon sinks” and are crucial to scrubbing the atmosphere of carbon dioxide.
“We have this system that we have relied on to counter our mistakes, and we have really exceeded the capacity of that system to provide reliable service,” Fiona Soper, a co-author of the new study and an assistant professor at McGill University, said.
The scientists say it’s not too late to turn things around. Along with halting global emissions from coal, oil and natural gas, they say Amazon deforestation must be curbed, fewer dams built, tree planting efforts stepped up and more research carried out.
“The message of this is obviously not to cut more, and it’s obviously not to stop restoring degraded ecosystems,” Covey told Fast Company. “I think the message is that if we’re going to lean on them as a key pillar, then we need to invest a lot in understanding them and in as much of the complexity that they offer as we can.”