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Science: Amazon Birds Harmed Despite "Habitat Patches" in Logged Forests
A 10-hectare and a 1-hectare fragment just after isolation.
[Photo © R. Bierregaard, Jr.]
The practice of heavily logging Amazon forests but leaving small, isolated "habitat patches" has a consistently strong negative effect on many native species of forest birds, according to the results of a 13-year study published in the 12 January issue of Science.
Gonçalo Ferraz of the Instituto Nacional de Pesquisas da Amazônia in Manaus, Brazil, and his colleagues performed a large-scale experimental study at the Biological Dynamics of Forest Fragments Project to quantify the effects of patch size and patch isolation on 55 species of forest birds from the central Amazon.
Originally all 23 patches were in contiguous forest, but 11 were eventually isolated by ranchlands.
Ferraz and colleagues found that patch size has a negative effect on species occurrence, with fewer species persisting in smaller patches. The effects of isolation from larger tracts of forest are also often negative but vary considerably across species.
A ringed White-plumed Antbird, Pithys albifrons.
[Photo © S. Laurance]
The methodology separates the effects of size and isolation, and also takes into account that different species are detected differently.
The scientists predict that "further forest destruction is expected to result in additional species loss and larger effects of isolation."
12 January 2007