Sharing the Space

29 March 2001 7:00 pm

Crowded. Areas rich in biodiversity overlap with centers of human population, such as at Nairobi National Park in Kenya.

Wilderness holds great allure. But focusing conservation efforts on these pristine, uninhabited spaces would leave many species vulnerable to extinction, according to a new analysis of human population and biodiversity in sub-Saharan Africa. In the 30 March issue of Science, researchers report that the greatest biodiversity is found in some of the most densely populated regions on the subcontinent.

The study focused on vertebrates. Andrew Balmford, a zoologist at the University of Cambridge, zoologist Carsten Rahbek of the University of Copenhagen, and their colleagues mined a comprehensive database at the Zoological Museum in Copenhagen describing vertebrate populations across sub-Saharan Africa. The team analyzed human census data and data on 1921 bird species, 940 mammal species, 406 snake species, and 618 amphibian species in geographical squares approximately 100 kilometers on a side. Areas rich in species also tend to contain more people, the team found.

The pattern is probably not unique to Africa, Balmford says. In North America, for example, "some of the highest conservation priorities have the highest real estate values," most notably along the East and West coasts. Smaller studies in South America show a similar pattern, notes ecologist Stuart Pimm of Columbia University in New York City.

The paper "cuts against much of the ethos of the conservation movement that wants to preserve absolutely pristine environments," says Sir Robert May, a zoologist at the University of Oxford. "I share that feeling, but there has to be much more work on determining minimal ecological structure: How much of the original habitat do you have to keep to enable particular plants and animals to coexist with humans?"

In some regions, however, "the only way you're going to make sure anything is left is by having secure borders and protecting what you have," says ecologist Gustavo da Fonseca of Conservation International. He says the study highlights the fact that if African biodiversity is to survive, "at some point we have to bite the bullet and make some very strong choices, even if those are costly and difficult both economically and socially," such as creating well-protected parks and compensating local residents. The study should help guide some of those choices. "We can't make these decisions unless we know where the species and people are," Fonseca says. "They've done that analysis in an extremely comprehensive way."

Related sites

More information on the study

More information on hotspots from Conservation International

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