We learned in elementary school that trees are good for the atmosphere because they take in harmful carbon dioxide (as well as carbon monoxide and sulfur dioxide) and release oxygen. Rainforests, those dense, rich, species-diverse forests, have historically been so good at this, they’ve been dubbed “the lungs of the planet.” Tropical forests store carbon, known as carbon sequestration, in their stems, leaves and roots, rather than releasing it to the atmosphere where it contributes to global warming and climate change. Unfortunately, these natural lungs appear to be losing their function, releasing more carbon dioxide into the atmosphere than they take in, according to a new study in the journal Science. Given that tropical forests store 25 percent of the global carbon and are home to 96 percent of the world's tree species, this new research reveals a potentially huge impact.
After analyzing satellite imagery of Asia, Africa and the Americas, researchers determined that deforestation, in which forests are torn down and replaced with urban spaces, farms or roads, is stealing the atmosphere-purifying power of these forests. However, it’s not just the sheer loss of numbers of trees that are responsible for the shift, the researchers say, so much as it is a decline in diversity of the kinds of trees that remain.