Part of the Amazon is emitting more carbon dioxide than it absorbs — and it's a "really big warning" for the planet

The Amazon rainforest has played a critical role in the fight against climate change by absorbing carbon dioxide that would otherwise be released into the atmosphere. But a study published in Nature on Wednesday found that humans are threatening its ability to do so — which could have devastating consequences for the planet. 

The Amazon basin is roughly 80% to 90% of the size of the continental U.S. and contains 2.8 million square miles of jungle, which is more than half of Earth's remaining tropical rainforests, according to the National Oceanic and Atmospheric Administration, which helped support the research. The region stores roughly 123 billion tons of carbon in trees and in the soil. "Roughly half of the CO2 that we've emitted from fossil fuels has been absorbed by either the oceans or the land — and that's roughly a 50-50 split," John Miller, one of the study's lead authors, told CBS News. "So there's this huge climate mitigation service that we're getting for free, and global warming would be much worse if trees were not taking this up."