To understand how fragmentation is affecting the trees, the team studied 22 different characteristics of the increasing and declining species. Our results show that tree communities in fragments are being completely restructured, said Nascimento. Most vulnerable are trees specialized for living in the dark forest understory that need animals such as birds or bats to disperse their seeds and pollen.
Fragmentation is also changing the dynamics and structure of the forest. Tree communities in fragments are highly unstable, losing and gaining species at a high rate. Fragments also tend to lose many of their large trees and become dominated by small, fast-growing species.
Forest fragmentation may even increase global warming. The authors demonstrate that the small, fast-growing trees that proliferate in fragments contain less biomass, and hence store less carbon, than do the original rainforest trees they replaced. The carbon from the dead rainforest trees is broken down by microbes and fungi to become carbon dioxide, the most important greenhouse gas.
Fragmentation is affecting the forest in a lot of ways, said Laurance. These changes occur remarkably fast, and when you completely alter something as basic as the trees, the other species that live in the rainforest will surely be affected too.