— Logging in tropical rainforests creates more insidious and longer-lasting environmental devastation than previously thought, researchers say.
When loggers and ranchers clear-cut parts of the jungle, the forest fragments that remain change far more quickly than ecologists expected, according to a famous, long-running study of forest fragmentation in central Brazil.
There, researchers have been carrying out a census of tree species in 40 one-hectare rainforest plots since the early 1980s, when ranchers cleared large swathes of forest to leave fragments ranging in size from 1 to 100 hectares.
William Laurance, a tropical ecologist at the Smithsonian Tropical Research Institute in Balboa, Panama, and colleagues combed through these censuses to compare plots near forest edges with those in mature forest far from edges. The edge plots, they found, were more likely to lose their original tree species because of wind damage and drought, and were also more likely to gain fast-growing colonising species.
These changes cause the forest to become more unstable and less mature than undisturbed forest, even though the total number of tree species present on each plot remains roughly the same. Moreover, the new trees tend to be smaller and have less dense wood than the trees they replace, so that the change represents a net loss of carbon storage an ominous trend for the forest's ability to buffer against global warming.
"In just two decades a wink of time for a thousand-year-old tree the ecosystem has been seriously degraded," says Laurance.
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0609048103)