Is pulling up invasive kudzu worth the effort? What about sprucing up a degraded stream channel? Restoring damaged ecosystems has long been an act of faith on the part of nature-lovers, but now a new study provides the strongest evidence to date that the practice is not only good for biodiversity, but also for humanity.

Since the rise of ecological economics in the 1990s, conservationists have tried to estimate the dollar value of all the eco-services Mother Nature provides society, in the hopes of preserving them. Tropical forests, for instance, can sequester climate-warming carbon dioxide, and coastal salt marshes provide breeding grounds for fisheries as well as filtration systems to keep fertilizer runoff from suffocating seas.

Although many conservationists have assumed that pristine ecosystems and biodiversity hot spots would offer the greatest benefits to humanity, few studies have confronted the question of eco-rehab head-on. Without that link conservationists have been hard-pressed to make an economic argument for restoration projects large and small. But an analysis published in this week's Science demonstrates that reparation generally provides a significant improvement in the services that ecosystems provide humanity.

"We were amazed when we found such a strong signal between restoration projects that increase biodiversity and those that increase ecosystem services," says James Bullock an ecologist at the Center for Ecology and Hydrology in Wallingford, England, "This is one of the first tests."

To study the question, José Benayas, a biologist at the University of Alcalá in Madrid, Bullock and colleagues pooled data from 89 restoration projects around the globe and looked at how restoring ecosystems impacted their biodiversity and their eco-services. By both measures, restored ecosystems were deficient compared with untouched ones, but the practice still had the capacity to increase biodiversity and eco-services by 44 and 25 percent, respectively.

Restoration seems to work better in some habitats than others. Terrestrial tropical ecosystems respond strongly to rehab, whereas temperate aquatic ones, such as saltwater marshes, fared poorly by both measures. In a few cases, restoration was found to have negative effects on biodiversity or ecosystem services or both.

Robert Costanza, an ecological economist at the University of Vermont in Burlington, says the new study will finally give managers quantitative information about the costs and benefits of restoration. In the past managers simply restored ecosystems to match an arbitrary point in history. "Measuring potential ecosystem benefits and the cost of restoration allows you to use limited resources more efficiently," he says. "That's different from a lot of the restoration planning going on today."