Environmentalists who hoped that preserving fragments of pristine forests would thereby preserve species have received bad news from a Duke ecologist's study of forest-dwelling tropical birds. The study found that even resilient deep-woods bird species that manage to hang on in remaining patches of a deforested area of Brazil gain no real advantage in avoiding extinction.
"Species that also tolerate secondary habitats are not deforestation's survivors," says Grant Harris Ph.D. '04, the first author of a paper on the subject published in the December issue of the Journal of Conservation Biology. Harris, who studied at the Nicholas School of the Environment and Earth Sciences, works for the U.S. Forest Service in Alaska.
"If you lose your habitat, everybody is equally threatened," adds co-author Stuart Pimm, the Nicholas School's Doris Duke Professor of conservation ecology. "There's no special class of species that seems to adapt well to the habitats we create for them."
Harris and Pimm started with the premise that in any deforestation, small patches of original habitat survive. They sought to explore how well some species survive in deforested habitat and whether some surviving species can persist in such landscapes.
Their study focused on Brazil's Atlantic Forest, now reduced to about 10 percent of its original extent and the home of more species threatened with extinction than anywhere else in the Americas. The scientists studied birds because of their extensive background knowledge of bird species and because of the enormous diversity of birds in the region.
By mapping the extent of deforestation and analyzing data on bird populations and ranges, they estimated the remaining distributions of two categories of bird species. "Forest obligate" birds are those that cannot exist outside the deep woods, and purported "survivor" birds are those that can supposedly survive in more marginal habitats. Some researchers have claimed that, even with deforestation, the second category would not become extinct, because they could tolerate degraded habitats.
But Harris and Pimm discovered otherwise. "We found no survivors," they wrote. "Habitat loss threatens forest-obligate birds and those using secondary habitats equally."