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In a landscape empty of a critical carnivore, parts of Yellowstone National Park became denuded, its greenery eaten by elk, its biodiversity diminished. Then in 1995, wildlife managers reintroduced gray wolves to restore the population and found that their presence actually benefited the environment around them. Successful examples like that are the basis for a new paper in BioScience in which the authors propose that national park officials reintroduce managed wolf packs on conserved land in order to restore damaged habitats.

"The pros, the benefits, would far outweigh the negatives," says lead author Daniel Licht, a wildlife biologist with the National Park Service. “We have these ecosystems that are in dire need of wolves, and we think that the debate now should say, 'Consider reintroducing wolves even when the population is not viable or self-sustaining.'”

Wolves eat ungulates like elk and deer, reducing their numbers. The mere existence of wolves in the same ecosystem also creates what biologists call an “ecology of fear,” so ungulates spend less time eating in one place. As a result, trees and shrubs come back and there’s more biodiversity. In Yellowstone, researchers saw that open fields became more vegetated when they reintroduced wolves. Wolves also increase biodiversity by providing food for scavengers and influencing the way that coyotes behave.

The benefits aren’t limited to the environment. “Wolves in Yellowstone National Park increased visitation and ecotourism spending by $35 million in 2005,” Licht and his four co-authors write in the paper. Having the predators in the park could make visitors more appreciative of the wild environs and give them a thrill when they hear a howl or see another wolf sign.

The populations wouldn’t be self-sustaining, they say, and could be managed with GPS, contraception, and surgery—a potentially less expensive and energy intensive alternative to ungulate fertility control. People overseeing the project could erect fences, eliminating predation on livestock and animals, and protecting people.

Yet wolf reintroduction and protection remains a polarizing issue, despite the fact that biologically predators are a vital part of a healthy, natural ecosystem. “We need to go through the planning process and look at the alternatives and weigh all of the pros and cons,” says Licht. “Every place is going to be different, but we think this concept warrants more serious discussion than it’s been given in the past.”

If someone had mentioned reintroducing wolves into Yellowstone 50 years ago, he wouldn’t have been taken seriously, says Licht. Now that wildlife biologists know how wolves benefit the environment and the public, reintroducing them in more national parks could be the next step for ecosystem management, write the authors. “While the use of wolves for ecosystem restoration and stewardship on small natural areas will not be a panacea, it will move all of these areas closer to true and meaningful biodiversity conservation.”