Heinz Center President Tom Lovejoy on Habitat Fragmentation and Time to Extinction

Continuing development of natural areas around the world means that conservation managers need to know how quickly they must act to counter the effects of habitat fragmentation. Existing knowledge of species--area relations predicts the number of species that a habitat fragment of a certain size can hold, but until now it has not been possible to know how fast a fragment would lose its species. A paper published today in the Proceedings of the National Academy of Sciences (PNAS Online) provides an answer to that question: it reports that the number of captures per species in fragments diminishes over time in a predictable way. From those declining numbers, the authors derive a rule for the time it takes to lose half the species in habitat fragments of different sizes: fragments smaller than one square kilometer lose half their bird species in less than 15 years, too quickly for conservation measures to work. To slow the rate of species loss by 10-fold, fragment area must increase 1000-fold.

(PRWEB) November 5, 2003 -- Continuing development of natural areas around the world means that conservation managers need to know how quickly they must act to counter the effects of habitat fragmentation. Existing knowledge of species--area relations predicts the number of species that a fragment of a certain size can hold, but until now it has not been possible to know how fast a fragment would lose its species.

According to Thomas E. Lovejoy (president of The H. John Heinz III Center for Science, Economics and the Environment), and Gonçalo Ferraz (a researcher at the Nicholas School of the Environment, Duke University, and Ph.D. candidate at Columbia University), a paper to be published this week in the Proceedings of the National Academy of Sciences (PNAS Online) provides an answer to that question. The paper (Rates of Species Loss from Amazonian Forest Fragments," by G. Ferraz, G. J. Russell, P. C. Stouffer, R. O. Bierregard, S. L. Pimm, and T. E. Lovejoy) reports that the number of captures per species in fragments diminishes over time in a predictable way. From those declining numbers, the authors derive a rule for the time it takes to lose half the species in habitat fragments of different sizes. What they found is that fragments smaller than one square kilometer lose half their bird species in less than 15 years, too quickly for conservation measures to work. To slow the rate of species loss by 10-fold, fragment area must increase 1000-fold.

These are the latest findings of the Biological Dynamics of Forest Fragments Project (BDFFP), founded in 1979 by Dr. Lovejoy as the Minimum Critical Size of Ecosystems Project. Which plants and animals could withstand the inevitable development that would reduce and fragment the Amazonian forest? How large would reserves need to be to ensure the survival of rainforest species into the next century? Lovejoy and his colleagues have been working to answer these questions ever since, and the project is now one of the worlds largest and longest-running ecological projects.

Understanding the connection between habitat fragment size and time to extinction for bird species in the Amazon will help scientists and conservation managers deal with similar problems in other areas and with other species. The Heinz Centers ongoing State of the Nations Ecosystems project is focusing on fragmentation issues as its new Landscape Pattern Task Group begins work. The Task Group expects to complete its report in early 2005; the second State of the Nations Ecosystems report will appear in 2007.

The Heinz Center, established in 1995 in memory of Senator John Heinz, is a nonprofit, nonpartisan institution dedicated to improving the scientific and economic basis for environmental policy and to developing innovative solutions to environmental problems.

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