Image: Kate Wong

With human land-use pressures taking an ever-increasing toll on tropical biodiversity, conservationists agree that without effective protection many of these plants and animalssuch as Madagascar's black-and-white ruffed lemur (right)will perish. Establishing parks is one such safeguarding strategy. Critics, however, charge that parks generally fail to preserve the biodiversity within their borders. But the results of a study published today in the journal Science indicate that, in fact, parks do protect and that increased funding would improve their performance.

Aaron G. Bruner of Conservation International and his colleagues studied 93 parks "at risk of failure" in 22 countries. They then assessed park performance, looking at, for example, land clearing since establishment, and the condition of the park as compared with its surroundings. The team found that 83 percent of the parks succeed in halting land clearing, and roughly half of those even incorporated neighboring land formerly under cultivation into their borders, thereby increasing vegetative cover. The parks were not so effective in preventing logging and hunting, but 60 percent still fared better than the areas surrounding them. Park success, Bruner and his colleagues determined, correlated most strongly with the density of guards patrolling the grounds. "The median density of guards in the 15 most effective parks," they report, "was more than eight times higher than in the 15 least effective parks."

"There is a clear need to increase support for parks to improve effectiveness against all threats, perhaps especially hunting," the authors conclude. "These findings suggest that parks should remain a central component of conservation strategies. Both creating new parks and addressing the tractable problem of making existing parks perform better will make a significant contribution to long-term biodiversity conservation in the tropics."