When it comes to trapping carbon from the atmosphere, little is as effective as the Amazon rainforest. When the forest burns, the result is catastrophic for the Earth. Researchers have recently discovered that Amazonian forest fires are even worse for the environment than we suspected: the fires that burned during El Niño into the atmosphere as previously thought.
During the warmer-than-average El Niño years of 2015 and 2016, extensive forest fires broke out in the Amazon. These fires were some of the worst the rainforest has suffered in decades, and burned more than a million acres across Brazil.
The fires also burned a handful of test plots set up by a group of researchers in the rainforest. Initially, the researchers set up the test plots to study the healthy forest, but after eight of them were caught in the blaze they decided to seize this opportunity to learn more about how forest fires affect this unique environment.
The researchers compared how much vegetation was left over after the fire with how much they had recorded before it started. the fires released three to four times as much carbon dioxide as predicted by commonly-used databases.
This is a pretty big discrepancy, and the researchers believe it’s due to underestimating the amount of carbon released by the understory, the ground level of the rainforest. The Amazon’s understory is filled with smaller plants, leaves, and other debris, and this plant matter contributes a great deal of carbon to the atmosphere when it burns.
The researchers also examined what happens when the forest starts to recover from a devastating fire. The good news is that trees and other plants in fire-scarred regions grow back very quickly. The researchers found that trees in areas that had been burned grow about 250 percent faster than normal trees.
The bad news is that this rapid growth rate isn’t enough to ever fully recover from a fire. Even when examining regions of the Amazon that experienced fires decades ago, the researchers found that these places still haven’t fully recovered.
“Only a few trees can survive these wildfires, as Amazonian forests did not co-evolve with this threat,” says study author Jos Barlow . “So even though surviving trees grow faster in burned forests, this does not compensate the large carbon loss that results from tree mortality.”
The end result is a vicious cycle where forest fires send huge amounts of carbon dioxide into the air, which increases temperatures and makes those same fires more likely and more deadly. It’s just one more way that climate change poses an existential threat.