The giant panda, the North American gray wolf, the black rhinoceros. These are just three of the dozens of mammals on the Department of the Interiors threatened or endangered species list.

Singling out vulnerable species for protection has been an important conservation tool for nearly 30 years. Now two prominent ecologists Stanford Professor Paul R. Ehrlich and Gerardo Ceballos of the University of Mexico (UNAM) are calling for a broader approach to wildlife preservation.

Writing in the May 3 issue of the journal Science, the researchers argue that, in addition to identifying endangered animal species, conservationists also must begin monitoring endangered animal populations.

Population extinctions are a more sensitive indicator of the loss of biological capital than species extinctions, they wrote. This is because many of the species that have lost a substantial portion of their populations are unlikely to go globally extinct and enter the species extinction statistics in the foreseeable future.

The authors noted that, although the disappearance of populations is a prelude to species extinction and signals a deterioration of ecosystem services essential to society no geographically precise estimates have been made of current population losses.

Most analyses of the current loss of biodiversity emphasize species extinctions and patterns of species decline, and do not convey the true extent of the depletion of humanitys natural capital, Ceballos and Ehrlich said. To measure that depletion, we need to analyze extinctions of both populations and species.

Focus on mammals

In their study, the authors examined evidence for population extinctions in medium and large-sized mammals.

Because of the diversity and variety of habitats mammals exploit, they can serve as an indicator of what is happening globally to animals and plants, said Ehrlich, the Bing Professor of Population Studies in Stanfords Departm
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Contact: Mark Shwartz
mshwartz@stanford.edu
650-723-9296
Stanford University
2-May-2002