Survival in Patches

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Science  05 Dec 2003:
Vol. 302, Issue 5651, pp. 1627
DOI: 10.1126/science.302.5651.1627b

Tropical forests worldwide are being fragmented into smaller patches by human activity. These fragments are of varying sizes and degrees of isolation from one another and are the only refuge for most of the tropics' wildlife. If conservation planning is to be effective, data and long-term projections are needed on the sizes of fragments that can support viable populations of organisms. For almost a quarter of a century, the Biological Dynamics of Forest Fragments Project, established in the Brazilian Amazon, has been following the fate of the habitat and inhabitants of forest fragments of varying sizes. Ferraz et al. have surveyed bird populations in sites of 1, 10, and 100 ha, and derive from their data a scaling rule relating rates of species loss to area of fragment. Not surprisingly, the smaller fragments lose species fastest, but even the 100-ha fragments lost 50% of their species in about 10 years. Thus a minimum fragment size of at least 10,000 ha appears to be required to reduce the loss of species to <50% over a century, and large protected areas in tropical forest will need to be maintained. — AMS

Proc. Natl. Acad. Sci. U.S.A. 24, 14069 (2003).

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