"Protected areas are the backbone of biodiversity conservation strategies," so it is critical to examine how population growth is affecting them, said Justin Brashares of the University of California, Berkeley, at "Fertile Fringes: Population Growth at Protected-Area Edges," an October 22, 2008, meeting sponsored by the Environmental Change and Security Program (ECSP). "Biodiversity conservation objectives are being impacted by higher deforestation rates, [natural resource] offtake rates, [and] increasing pressure on the protected area" due to high local population growth, explained George Wittemyer of Colorado State University. Brashares and Wittemyer, who recently co-authored an article on population and protected areas in Science, were joined by Jason Bremner of the Population Reference Bureau.

To Stay or To Go?

"Many of the protected areas that we have today in sub-Saharan Africa and in Latin America are carryovers of areas set aside by colonial governments," said Brashares, "and for many researchers and for many communities, the creation of parks is seen to come at the cost of local communities." Yet certain features can encourage people to move near protected areas, including:

• Services made available by foreign assistance, such as health care, education, and livelihoods programs;
• Employment opportunities as park staff or in the tourism industry;
• Better ecosystem services, including food, water, wood, and traditional medicine;
• Easier access to markets, due to roads built to attract tourism; and
• Improved security provided by park guards and government staff.

Other features of protected areas deter migrants, including:

• Land-use restrictions;
• Conflict with wildlife (e.g., attacks on livestock and crops);
• Disadvantages associated with tourism, including higher cost of living and potential loss of cultural heritage;
• Isolation from urban centers; and
• Conflict with park staff, government representatives, or rural militias.

Higher Population Growth Near Protected Areas

Brashares and Wittemyer examined IUCN Category I and II protected areas in Africa and Latin America—which limit human activity within their boundaries—and excluded potentially confounding urban, marine, and new parks. Using UN Environment Programme population data from 1960-2000, they compared population growth in a 10-kilometer "buffer zone" surrounding each protected area with average rural population growth for that country. In 245 of the 306 parks they examined—and 38 of the 45 countries—population growth at protected-area edges was significantly higher than average national rural population growth.

Brashares and Wittemyer found three factors correlated with higher levels of population growth: more money for parks (as measured by protected-area funds from the Global Environment Facility); more park employees; and more deforestation on the edges of protected areas. Brashares emphasized, however, that there could be equally relevant correlations between population growth and employment in extractive industries, but that "the timber industry won't give us their data and the mining industry and the oil industries aren't so happy to share." Thus, the study might inadvertently penalize NGOs and international organizations for their transparency.

Some researchers hypothesized that because protected areas are usually located in ecologically dynamic areas, this ecological wealth might be attracting new residents, rather than the protected areas themselves. But Brashares and Wittemyer found that proximity to a protected area, not general ecological abundance, was driving the trend. Others suspected that population grows at protected-area edges because the people who have been displaced by the creation of a park move to the park's border. But population growth rates within the parks have been mostly stable or positive, so Brashares and Wittemyer doubt this is driving the trend.

Implications for Conservation

Brashares and Wittemyer outlined several policy implications of their research:

• Emerging infectious diseases are a serious risk in areas with high human density close to wildlife populations, so governments and international organizations should try to limit potential outbreaks near protected areas.
• If the effectiveness of a protected area is measured by its ability to preserve biodiversity for generations, then community development programs must be executed carefully. For instance, roads and schools should not be built in an ecologically fragile corridor between two parks.
• Multi-use buffer zones that make core areas less accessible can allow individuals to continue to benefit from their proximity to nature while protecting biodiversity. "Some of the best protection of biodiversity is through isolation," said Brashares.

Bremner took issue with some of Brashares' and Wittemyer's methods and conclusions; his full critique is available on ECSP's blog, the New Security Beat. Although Bremner agreed that migration—not natural increase—is likely driving higher population growth around protected areas, he believed the authors did not provide adequate evidence to demonstrate that this migration is driven by investments in conservation. "I hope that publishing this conclusion here in Science doesn't provide our detractors, those who don't want us to be spending on conservation, with the means to limit future spending for international conservation," said Bremner.

Drafted by Rachel Weisshaar.