The Amazon rainforest is teetering on a dangerous tightrope. As per a major new study, reported in the journal Nature, it looks like deforestation and climate change are pushing the Amazon towards a grim tipping point, with significant parts of the world's largest tropical rainforest now emitting more carbon than it absorbs.
The past few years have seen a number of scientists debating and speculating whether parts of the Amazon had made this dreaded flip. Just as they suspected, this new study affirms their worries that parts of the rainforest no longer protect against climate change and, in fact, actually contribute to greenhouse gas emissions.
The new study, led by Brazil’s National Institute for Space Research and the US National Oceanic and Atmospheric Administration (NOAA), looked at aircraft observations of carbon dioxide and carbon monoxide concentrations in the troposphere — the lowest layer of the Earth’s atmosphere — above Brazilian Amazonia from 2010 to 2018.
Their findings show southeastern Amazonia has now switched from becoming a net carbon emitter, switching from being a sink to being a substantial carbon source.
“Using nearly 10 years of CO2 (carbon dioxide ) measurements, we found that the more deforested and climate-stressed eastern Amazon, especially the southeast, was a net emitter of CO2 to the atmosphere, especially as a result of fires,” John Miller, study co-author and a scientist with NOAA’s Global Monitoring Laboratory, explained in a statement.
“On the other hand, the wetter, more intact western and central Amazon, was neither a carbon sink nor source of atmospheric CO2, with the absorption by healthy forests balancing the emissions from fires.”
One of the chief reasons for this shift in the so-called “lungs of the planet" is deforestation. Rainforests act as carbon sinks through their wealth of trees and plant life “sucking up” carbon dioxide from the environment and using it for photosynthesis. The carbon is sequestered by the plants and stored as biomass. A huge amount of carbon is also stored in the soil as dead organic matter, such as decomposing trees. In the simplest terms, fewer trees mean less potential for the rainforest to suck up carbon. On top of all of this, rising temperatures produced by climate change also alert the capacity of tropical forests to absorb carbon.
On the other hand, rainforests also emit carbon through the respiration of microorganisms that decompose trees once they die. Forest fires — which have been very prominent in the Amazon over recent years — release huge amounts of stored carbon back into the atmosphere too.
All of these factors have all culminated in the southeast region of the Amazon, which has been hit especially hard by deforestation in the past 40 years, experiencing around 30 percent of total deforestation. As the Amazon continues to be ravaged by deforestation and unmitigated climate change, researchers are now eagerly keeping an eye on other parts of the rainforest, worrying if and when they might breach the tipping point of becoming a carbon source too.
“The big question this research raises is if the connection between climate, deforestation, and carbon that we see in the eastern Amazon could one day be the fate of the central and western Amazon, if they become subject to stronger human impact,” warned Miller.