Even young rainforests can help save the climate

Chazdon et al. Sci. Adv. 2016; 2 : e1501639

Even young rainforests can help save the climate

The logging of old-growth rainforest in the tropics—often to create cattle pastures—is a major blow to the climate. Cutting down the forests releases lots of carbon dioxide into the atmosphere—and of course, the trees aren’t absorbing it anymore. But that’s not the end of the story. When pastures are abandoned (often after a few years), trees start to come back, forming second-growth forests. These forests might lack the massive trees and rich biodiversity of an old-growth forest, but they can still play an important role in helping regulate climate. Robin Chazdon, an ecologist at the University of Connecticut, Storrs,  and the International Institute of Sustainability in Rio de Janeiro, Brazil, (who was profiled last August in Science), and a team of 60 researchers first estimated the extent of second-growth forests across 43 regions of Latin America, and then built a model to estimate their ability to store carbon. It turned out that second-growth forests made up a sizeable fraction: In 2008, 17% of forest was 20 years old or younger, and another 11% was between 20 and 60 years old (above). If all this forest continues to grow for the next 4 decades, their model showed, it would store 8.5 petagrams of carbon, 71% of that in Brazil alone, as the team reports today in Science Advances. That’s equivalent to the carbon emissions from all fossil fuels throughout Latin America and the Caribbean from 1993 to 2014. The results suggest that second growth forests—along with halting deforestation—can provide major help for meeting climate goals.