Earth's trees and plants absorb large amounts of carbon dioxide from the atmosphere during photosynthesis, incorporating some of this carbon into structures such as wood. Areas that absorb more carbon than they emit are called carbon sinks. But plants can also release greenhouse gases during processes such as respiration, when dead plants decay, or during combustion in fires. Researchers are particularly interested in whether – and how – plants at the scale of an ecosystem such as a forest act as sources or sinks in an increasingly warm world.
A recent study led by scientists at NASA's Jet Propulsion Laboratory in Southern California identified whether vegetated areas such as forests and savannas around the world were carbon sources or sinks each year from 2000 to 2019. The study found that during these two decades ago, woody plants were responsible for more than 80% of sources and sinks in soil, with soil, leaf litter and decaying organic matter making up the rest. But they also saw that the vegetation held a much smaller fraction of carbon than scientists first thought.
Furthermore, the researchers found that the total amount of carbon emitted and absorbed in the tropics was four times greater than in the temperate regions and boreal zones (northernmost forests) combined, but that the ability of tropical forests to absorb massive amounts carbon has faded in recent years. The decline in this ability is due to large-scale deforestation, habitat degradation and the effects of climate change, such as more frequent droughts and fires. In fact, the study, published in Science Advances, showed that 90% of the carbon that forests around the world absorb from the atmosphere is offset by the amount of carbon released by disturbances such as deforestation and drought.
The scientists created maps of carbon sources and sinks from land-use changes such as deforestation, habitat degradation and afforestation, as well as forest growth. They did this by analyzing data on global vegetation collected from space using instruments such as NASA's Geoscience Laser Altimeter System (GLAS) aboard ICESat and
(BalakanWeb)
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