Using advanced satellite data and machine learning, the researchers tracked more than a decade of changes in aboveground forest biomass, the amount of carbon stored in trees and woody vegetation. They found that while Africa gained carbon between 2007 and 2010, widespread forest loss in tropical rainforests has since tipped the balance.

Between 2010 and 2017, the continent lost approximately 106 billion kilograms of forest biomass per year. That is equivalent to the weight of about 106 million cars. The losses are concentrated in tropical moist broadleaf forests in countries such as the Democratic Republic of Congo, Madagascar, and parts of West Africa, driven by deforestation and forest degradation. Gains in savanna regions due to shrub growth have not been enough to offset the losses.