Because of their role in the carbon cycle, trees and other plants reduce the concentration of greenhouse gases in the atmosphere, slowing the pace of global climate change.
Over the last 40 years, Earth’s forests have absorbed about 25 percent of the carbon emissions produced by human activity. Forests that remove more CO2 from the air than they emit are called carbon sinks.
In some years, however, insect outbreaks or large fires alter the balance of the carbon cycle, turning forests into net sources of atmospheric CO2. That’s a concern, because the “extra” CO2 drives further climate change.
