- Amazon rain forest emits more carbon than it stores
The southern Amazon rainforest now emits significantly more carbon dioxide (CO2) than it absorbs due to forest damage, according to an analysis of detailed aerial imagery in the Brazilian states of Rondônia, Mato Grosso, and Pará from 2016 to 2018. The study, led by Ovidiu Csillik from the California Institute of Technology in Pasadena, shows that forest damage has various causes, with human activity often playing a role.
"Green Lung" of the Earth threatened
The Amazon rainforest in South America is home to more than 10% of all terrestrial species on Earth, according to a recent study published in the journal "Nature". The region contributes to the stabilization of global climate through the net cooling effect of water evaporation and stores a significant amount of carbon equivalent to the world's CO2 emissions for 15 to 20 years.
However, deforestation and other forest damages threaten the Amazon rainforest's role as the "green lung" of the Earth for the world's climate. Recent measures by the Brazilian government have reduced forest destruction.
Researchers analyze airplane images
"Satellite-based approaches, despite their greater range, suffer from coarse resolution, making it difficult to quantify the extent and intensity of forest damage," the authors of the current study write, reported in the journal "Proceedings of the National Academy of Sciences" ("PNAS").
They used images from airplanes flying in 99 strips over the study area at an altitude of 600 meters. The study used LiDAR technology, similar to a three-dimensional laser scan, to determine the height of the tree canopies. The study area was flown over twice, at intervals of one to one and a half years.
Human activity causes the most damage to the ecosystem
The study region covers an area of 544,300 square kilometers, or 8.2% of the entire Amazon region (about 6.6 million square kilometers). Csillik and his team found forest damage on 21.6% of the surveyed area. Of this, 0.7% was due to logging, 0.7% to agricultural expansion, and 2.8% to fires. Almost all fires in the Amazon are caused by humans, resulting in a total of 4.2% of the area damaged by human activities.
The team attributed the damage on the remaining 14.7% of the damaged area to smaller natural and human-caused disturbances that could not be identified with high certainty. The researchers were surprised by the large proportion of wind damage - 2.7%. No change was observed in 62.1% of the area between the two images. The researchers also found significant forest growth in 16.3% of the area.
Amazon absorbs less CO2
According to the study, this is insufficient to offset the carbon emissions from the damaged areas. The emissions totaled 134.6 million tons of carbon during the study period, while the forest growth absorbed 44.1 million tons from the air. This results in an annual emission surplus of 90.5 million tons of carbon between 2006 and 2018 in the studied area. The carbon balance of the soil was not considered in this study. The authors conclude: "This study highlights the role of forest damage in the carbon balance of this critical region in the Earth system."
The Amazon rainforest, often referred to as the "green lung" of the Earth, is not only home to a significant percentage of terrestrial species but also plays a crucial role in climate stabilization through water evaporation and carbon storage. Unfortunately, human activities such as deforestation and forest damage are threatening its ability to absorb more carbon dioxide than it emits, as seen in the southern Amazon rainforest, which now releases more CO2 than it absorbs.
The analysis of the current study, conducted using detailed aerial imagery, revealed that human activities, including logging, agricultural expansion, and fires, account for a substantial portion of the forest damage in the Amazon rainforest, contributing to its transformation from a carbon sink to a carbon source.
