Edge Effects and the Extinction of Populations Inside Protected Areas

American Association for the Advancement of Science (AAAS) - Tập 280 Số 5372 - Trang 2126-2128 - 1998
Roșie Woodroffe1,2, Joshua R. Ginsberg1,3
1J. R. Ginsberg, Wildlife Conservation Society, Bronx, NY 10460–1099, USA.
2R. Woodroffe, Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK. J. R. Ginsberg, Wildlife Conservation Society, Bronx, NY 10460-1099, USA.
3R. Woodroffe, Department of Zoology, Downing Street, Cambridge CB2 3EJ, UK.

Tóm tắt

Theory predicts that small populations may be driven to extinction by random fluctuations in demography and loss of genetic diversity through drift. However, population size is a poor predictor of extinction in large carnivores inhabiting protected areas. Conflict with people on reserve borders is the major cause of mortality in such populations, so that border areas represent population sinks. The species most likely to disappear from small reserves are those that range widely—and are therefore most exposed to threats on reserve borders—irrespective of population size. Conservation efforts that combat only stochastic processes are therefore unlikely to avert extinction.

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Tài liệu tham khảo

10.1126/science.3420403

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W. D. Newmark Cons. Biol. 9 512 (1995)

but see J. Berger ibid. 4 91 (1990).

Several intensive studies of carnivores have shown that deaths caused by people—especially harvesting—increase overall mortality and result in population decline. This impact of harvesting is marked in two species with low fecundity (black and grizzly bears) as well as one with high fecundity (gray wolf). For each species the proportion of deaths of radio-collared adults caused by people and sample sizes are as follows: gray wolf 79% (97); black bear 90% (21); grizzly bear 56% (16). Data sources: gray wolf: W. B. Ballard J. S. Whitman C. L. Gardner Wildl. Monogr. 98 1 (1987); W. B. Ballard L. E. Ayres P. R. Krausman D. J. Reed S. G. Fancy ibid. 135 1 (1997); black bear: R. A. Powell J. W. Zimmerman D. E. Seaman J. F. Gilliam Cons. Biol. 10 224 (1996); grizzly bear: R. B. Wielgus and F. L. Bunnell Biol. Cons. 67 161 (1994).

10.2307/1940382

IUCN Protected Areas of the World: A Review of National Systems (IUCN Gland 1992). We included protected areas in categories I II and IV defined by the IUCN. These categories include national parks reserves and sanctuaries established with the primary aim of protecting wildlife.

A summary data set and data sources are available at http://www.sciencemag.org/feature/data/980867.shl.

D. R. Cox The Analysis of Binary Data (Methuen London 1970). A model of the form p(reserve occupied) = {exp [A + B(log reserve area) + C(log reserve age)]}/{1 + exp [A + B(log reserve area) + C(log reserve age)]} where A B and C are constants was fitted to the data by using the Genstat statistical package [Genstat Committee Genstat 5 Release 3 Reference Manual (Clarendon Press Oxford UK 1993)]. Parameters were estimated by maximum likelihood to determine which significantly improved the fit of the model. The effects of reserve age and size were assessed by dropping each in turn from the model to estimate the contribution of each to total deviance. The resulting changes in deviance are distributed as χ 2 in this case with 1 df.

J. W. A. Grant C. A. Chapman K. S. Richardson Behav. Ecol. Sociobiol. 31 149 (1992).

10.1086/284325

10.1139/z89-264

We thank S. Durant L. Frank G. Mace J. Robinson P. Rohani and K. Rose for valuable comments and discussions.

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American Association for the Advancement of Science (AAAS)

Tập 280 Số 5372

2126-2128

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