Woody climbing vines called lianas are a known threat to tropical forests. They increase tree mortality and reduce growth, ultimately hampering a forest’s ability to store carbon in trees and battle climate change. Now a new study quantifies the rapid effect of the vines: Researchers who examined forests in the Barro Colorado Nature Monument in Panama report that after three years of growth, areas with lianas had accumulated 76 percent less biomass per year than plots that had been cleared of vines, mostly because of reduced tree growth. The study also reports that forest areas with lianas store more carbon in leaves and less in woody stems. Carbon in leaves returns to the atmosphere faster than carbon in stems.