DURHAM, N.C. – In 2008, a study in the journal Science reported that the creation of international parks and protected areas as a conservation strategy was backfiring, because it increased population density around the areas’ edges – isolating species in the protected areas from surrounding habitats and threatening the very biodiversity the areas were created to achieve.

A new study by researchers at 91 and the Carnegie Institution for Science refutes that claim.

The study, published January 26 in the online, open-access peer-reviewed journal PLoS ONE, examines population trends near protected area boundaries. Its authors find no evidence to support the theory that population growth is greater near edges of protected areas.

“Simply put: parks do not promote unusual population growth near them,” says co-author Stuart L. Pimm, Doris Duke Professor of Conservation Ecology at Duke’s Nicholas School of the Environment.

“In earlier work published in the Proceeding of the National Academy of Sciences, my group and I showed that there is no excessive deforestation at the immediate edges of parks – an observation that motivated our examining the Science paper in detail. As expected, we found that there is less forest cover outside than inside a park, of course, but more forest close to park boundaries than far outside them,” Pimm says. “As it were, parks aren't perfect, but they are forgiven.”

Pimm conducted the study with Lucas Joppa, the lead author and a doctoral student in his lab at Duke, and Scott Loarie, a postdoctoral research associate in global ecology at the Carnegie Institution for Science. Loarie received his PhD in conservation ecology from Duke in 2008.

Joppa, Loarie, and Pimm examined population growth in 45 countries and around 304 protected areas, using a series of 10-kilometer buffer zones both inside and outside the protected area boundaries. They looked at population densities within these areas between the time of each protected area’s creation and the year 2000, and compared them at increasing intervals away from the boundaries.

They conclude that while individual case studies may provide examples of increased growth near park boundaries, there is no evidence to support this as a general rule. If anything, they say, increased population densities near protected areas are due to the spreading of previous population centers. And this could have negative impacts, as well.

“It’s not like there’s a big electric fence around most of these protected areas,” says Joppa. “Often there’s nothing but a marker on a tree, or maybe a river or a small clearing in the woods to demarcate protected versus unprotected lands. And so it’s often very easy with low-levels of law-enforcement for small communities to encroach upon protected areas, and this could be a huge problem.”

Joppa and Pimm say that it is important to have accurate information about protected areas and human activities around them.

“Our results really make a huge amount of difference, because a very substantial amount of funding could be diverted if somebody were to say, ‘Look, setting aside a protected area doesn’t really do any good,’” says Pimm. “There is a clear, major international issue at stake, and that is whether protected areas work or not. If the World Bank were to come to the conclusion that they didn’t, then funding for international parks around the world could be in serious jeopardy.”

“We need to know whether these protected areas are working, and we need to know what the pressures are around their edges,” Joppa says. “Right now what we’re hoping to do is just set the record straight, so that we’re not making any rash conclusions or judgment calls.”

Pimm and his colleagues say they undertook their study in response to a paper published by ecologist George Wittemyer and his group from the University of California at Berkeley’s Department of Environmental Science, Policy, and Management. Wittemyer’s paper, published in the journalScience in July 2008, theorized that the creation of these protected areas creates new economic or employment opportunities in bordering communities, and may encourage people to migrate closer to park boundaries. This could cause protected areas to become increasingly isolated from the surrounding environments, and be a major threat to biodiversity.

Wittemyer’s study was “flawed,” Pimm says, “the key result an unfortunate consequence of mixing two incompatible datasets on human density — one near parks, the other further away.”

Editor’s note: For additional comments, contact Stuart L. Pimm, 919/613-8141 orStuartPimm@me.com; or Lucas Joppa, (608) 345-7085 (cell) or lucas.joppa@duke.edu.