Fire in the Amazon rainforest in the Candeias do Jamari region of Porto Velho in Brazil, on Aug. 24, 2019. Humanity has pushed atmospheric carbon dioxide levels almost 50% higher than they were before industrialization. That dramatic number would be even higher without tropical forests, which have been absorbing as much as 17% of CO₂ emissions along the way. Unfortunately, rainforests can’t capture carbon like they used to. In a new study using 30 years of data from pristine Amazon and African tropical forests, researchers found the actual rate CO₂-reduction rate peaked a quarter-century ago. These rainforests absorbed about a third less CO₂ over the past decade than they did the 1990s, according to the study published in the journal Nature . That’s a difference of 21 billion metric tons—or roughly similar to a decade of fossil-fuel emissions from the U.K., Canada, Germany, and France combined. South American forests […]