Effect of habitat area and isolation on fragmented animal populations
- aDepartment of Environmental Science, Policy, and Management, University of California, 137 Mulford Hall, Berkeley, CA 94720;
- bCentre for Species at Risk and Habitat Studies, University of British Columbia Okanagan, 3333 University Way, Kelowna, BC, Canada V1V 1V7; and
- cCentre for Biodiversity Research, University of British Columbia, 6270 University Boulevard, Vancouver, BC, Canada V6T 1Z4
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Edited by Monica G. Turner, University of Wisconsin, Madison, WI, and approved October 29, 2008 (received for review June 25, 2008)
Abstract
Habitat destruction has driven many once-contiguous animal populations into remnant patches of varying size and isolation. The underlying framework for the conservation of fragmented populations is founded on the principles of island biogeography, wherein the probability of species occurrence in habitat patches varies as a function of patch size and isolation. Despite decades of research, the general importance of patch area and isolation as predictors of species occupancy in fragmented terrestrial systems remains unknown because of a lack of quantitative synthesis. Here, we compile occupancy data from 1,015 bird, mammal, reptile, amphibian, and invertebrate population networks on 6 continents and show that patch area and isolation are surprisingly poor predictors of occupancy for most species. We examine factors such as improper scaling and biases in species representation as explanations and find that the type of land cover separating patches most strongly affects the sensitivity of species to patch area and isolation. Our results indicate that patch area and isolation are indeed important factors affecting the occupancy of many species, but properties of the intervening matrix should not be ignored. Improving matrix quality may lead to higher conservation returns than manipulating the size and configuration of remnant patches for many of the species that persist in the aftermath of habitat destruction.
Footnotes
- 1To whom correspondence should be addressed. E-mail: prugh{at}nature.berkeley.edu
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Author contributions: L.R.P. and K.E.H. designed research; L.R.P. and K.E.H. performed research; L.R.P. analyzed data; and L.R.P., K.E.H., A.R.E.S., and J.S.B. wrote the paper.
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The authors declare no conflict of interest.
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This article is a PNAS Direct Submission.
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This article contains supporting information online at www.pnas.org/cgi/content/full/0806080105/DCSupplemental.
- © 2008 by The National Academy of Sciences of the USA
