In the wolf hearings Fish and Game held around the state, one of wolf advocates most powerful arguments for keeping the wolf population high was their assertion that it would have a positive cascading effect throughout the ecosystem.
Their argument, based on the research of two Oregon State ecologists released in 2003, is that fear of wolves is keeping elk from eating too many young trees and shrubs in the streamside zones along rivers. Robert Beschta and William Ripple , professors of forestry at Oregon State say the reintroduction of wolves has allowed willows and cottonwoods to grow back, reducing erosion, improving stream quality and encouraging the return of species from insects up to birds.
The two OSU scientists research fits the view that restoring wolves has reduced the overgrazing that was going on in the park because the elk populations were allowed to grow largely unimpeded, a view livestock growers and range managers shared for years.
Don Despain, a retired plant ecologist with the U.S. Geological Survey, who has studied Yellowstone since 1971, has been telling me ever since their report came out in 2003 that he doesn’t believe wolves are the reason willows and other streamside shrubs are growing back. He and Yellowstone researcher Ron Renkin say longer growing seasons, caused by climate change, are the cause. There is a good story about this at High Country News.
Which scientists are right? Probably both. But it will take more research to determine whether climate change or wolves are having the larger impact.
Nothing is simple in ecology.