Due to forest damage, the southern Amazon rainforest is now emitting significantly more carbon dioxide (CO2) than it absorbs. This is the result of an analysis of aerial photographs taken in the Brazilian states of Rondônia, Mato Grosso and Pará between 2016 and 2018. As the study led by Ovidiu Csillik from the California Institute of Technology in Pasadena shows, the damage has very different causes, with humans often playing a role.
The Amazon rainforest in South America is home to more than ten percent of all terrestrial species living in the world, according to a study recently published in the journal Nature. The study states that the area contributes to stabilizing the Earth’s climate through the net cooling effect of water evaporation. The rainforest also stores an amount of carbon equivalent to 15 to 20 years of global CO2 emissions.
Shots from airplanes are more precise
But deforestation and other damage threaten the role that the Amazon rainforest plays as the earth’s “green lung” for the global climate. Measures taken by the current Brazilian government have recently significantly reduced forest destruction.”Despite their greater reach, satellite-based approaches suffer from coarse resolution, which makes it difficult to quantify the extent and intensity of forest degradation“, write the authors of the current study, which is reported in the journal “Proceedings of the National Academy of Sciences” (“PNAS”).
They therefore used images from aircraft that flew over the study area at an altitude of 600 meters in 99 measuring strips. The so-called Lidar technology was used: a method similar to radar that is roughly equivalent to three-dimensional laser scanning. In this way, the research group determined, among other things, the height of the treetops. The study area was flown over twice at intervals of one to one and a half years.
The study region has an area of 544,300 square kilometers, which is 8.2 percent of the entire Amazon region (about 6,600,000 square kilometers). Csillik and his team discovered forest damage on 21.6 percent of the area studied. Of this, 0.7 percent was due to logging, 0.7 percent to land clearing for agriculture and 2.8 percent to fire. According to the research group, almost all of the fires in the Amazon region are started by humans. This results in 4.2 percent of the area being damaged by human activities.
Man-made damage
Csillik’s team attributes the damage on the remaining 14.7 percent of the damaged area to minor natural and man-made disturbances that could not be identified with great certainty. The scientists were surprised by the large proportion of damage caused by wind damage – i.e. strong wind – at 2.7 percent. There was no change between the two images on 62.1 percent of the area. The researchers also found clearly visible forest growth on 16.3 percent of the area.
However, this is not enough to offset the carbon emissions from the damaged areas. Emissions totaled 134.6 million tonnes of carbon during the study period, while 44.1 million tonnes were absorbed from the air through forest growth. This results in annual emissions of 90.5 million tonnes of carbon between 2016 and 2018 on the area studied. However, the soil’s carbon balance was not taken into account. The authors conclude: “This study highlights the role of forest degradation in the carbon balance of this critical region in the Earth system.“
The study can here can be retrieved.
(Oekoreich/APA)
