Carnivore species are predicted to be at increased extinction risk from human population growth

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Research published online today reveals that many of the world's carnivores are at greater risk of extinction than previously thought. Close to a quarter of the world's mammals are already at high risk of extinction. Any chance of reversing this trend depends on understanding what makes some species vulnerable and others resilient. And that depends on being able to predict extinction risk.

Now, a new model based on a phylogenetic analysis of the mammalian order Carnivora, described online in the open-access journal PLoS Biology, could help focus conservation efforts by predicting which species face greatest risk. The model predicts risk based on the density of local human populations combined with various traits of different species of carnivores, such as their population density, gestation length, and habitat range. The research, by Marcel Cardillo and other conservation scientists from London, Virginia and the IUCN, finds that combining data on species' biology with that on human population densities yields better predictions of extinction risk than either set of data can alone. For example, a species with a long gestation period that lives close to densely populated human areas are at greater risk than species with similar gestation periods that live near sparsely populated areas. When under heavy pressure from people--whether hunting or habitat loss--species with long gestation periods can't repopulate fast enough and become endangered.

Based on projected human population growth, the researchers predict that many carnivore species will join the list of endangered species list by 2030. Most of these species live in Africa, where human populations are growing faster than the global average. Based on the researchers' projections, some species currently considered low conservation priorities--such as members of the weasel-like viverrid family--could soon become endangered.

Altogether, these results indicate that as human population pressures increase, it becomes ever more important to take account of each species' biological traits to best predict which species will become most vulnerable. While most conservation efforts focus on damage control, Cardillo and colleagues argue for interceding before a species reaches the brink of extinction. "There is no room for complacency about the security of species," the authors warn, "simply because they are not currently considered threatened."

Citation: Cardillo M, et al (2004) Human population density and extinction risk in the world's carnivores. PLoS Biol 2(7): e197

DOI: 10.1371/journal.pbio.0020197

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