We all rely on the trees and plants around us for oxygen. The health of our world’s forests and diverse ecosystems are directly connected to the state of our water, our cities, and the lives of people and animals around the globe.
Unfortunately, the effects of climate change and other man-made factors have turned some of the world’s tropical forests into sources of carbon dioxide. Rather than absorbing carbon dioxide and producing oxygen, some forests are now expelling carbon dioxide into the atmosphere.
Damaged forests seem to be the most at risk for emitting carbon dioxide rather than absorbing it. Satellite images targeting areas of tropical Asia, Africa, and the Americas have shown that some tropical forests are dispelling more carbon than they are taking in. Deforestation is leading to much of the carbon release, as trees are logged, cut down for houses, or burned to make room for commerce or additional housing for communities in the area.
Although deforestation contributes to much of the carbon dioxide expulsion, there are other factors that are causing the forests to give off carbon dioxide. This includes a decrease in the diversity of the trees and plants that are growing in the forests.
Tropical forests and the trees growing in them store carbon in their roots, leaves, and stems. Selective logging of certain kinds of trees or clearcutting of a forested area results in that stored carbon being released back into the atmosphere. Wildfires and diseases that impact tropical trees can also release carbon from these areas.
Subtle degradation of tropical forests can be difficult to detect, which is where satellite images come into play. Satellites are able to detect mass deforestation, but can also be finely tuned to analyse changes in tropical forest environments. Although satellites can’t detect the weight of carbon being released from a forest, it can detect he density of the trees in a tropical forest.
Researchers have developed new techniques for detecting how much carbon is being released into the atmosphere from tropical forests around the world. Satellite images can be calibrated and combined with NASA’s Light Detection and Ranging Data (LiDAR) data and put into an algorithm that shows changes in carbon emissions over time.
Using these methods, researchers found that tropical forests release 862 teragras of carbon into the atmosphere every year. This is more than all the emissions from cars in the United States in 2015. Unfortunately, the same forests are only absorbing 436 teragrams of carbon. About 60% of the carbon comes from the tropical regions of the Americas, including the Amazon, and about 24% comes from Africa. A further 16% is from tropical forests in Asia.
The results of the researchers’ study have gained the conservation movement a lot of ground. There is now an empirical way to determine not only how deforestation affects the carbon levels in our atmosphere, but how low-level degradation of the forest also influences carbon levels. The data set doesn’t take into consideration what carbon is absorbed in the soil of forests, which overall allows the earth to absorb more carbon than is being released.
Researchers hope that this study and more studies like it will increase awareness about the importance of our world’s forests and how easily some of this degradation can be reversed.
Baccini, A., Walker, W., Carvalho, L., Farina, M., Sulla-Menashe, D., & Houghton, R. A. (2017). Tropical forests are a net carbon source based on aboveground measurements of gain and loss. Science, 358(6360), 230-234.