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Wolves Helping Aspen Return To Northern Yellowstone

Aspen stands play a critical role in local ecosystems by providing habitat for birds, insects and various kinds of plants.

Aspen trees are on the rebound in and around Yellowstone National Park, and a new report says predators deserve the credit.

Luke Painter, a wildlife ecologist at Oregon State University and the study's lead author, says the trees were in decline for decades largely because concentrated elk populations were eating new tree shoots. 
He says since wolves were reintroduced, elk numbers have decreased and most of the herd's winter range is now outside the park.

"So that's relieved the pressure on the young aspen plants, and we're seeing new aspen trees beginning to grow," he points out. "So, this is a sign that things really have turned around for aspen in northern Yellowstone."

Wolves, along with bears, cougars and hunters outside the park, are culling the elk herd, which translates into fewer elk grazing on aspen and other woody species. 

Putting wolves back into the park in 1995 was a point of controversy because of ranchers' concerns about losing livestock and dogs, and outfitters who worried that fewer elk could mean a loss of tourism dollars.

Painter admits that some outfitters that depended on large elk concentrations in and near the park in the 1980s and '90s have lost some of that business.

"At the same time, there's a lot of new businesses around here bringing people into the park to see the wolves," he stresses. "That's actually stimulated some of the local economy, and there's a number of new startups doing that."

Painter says what's happening in Yellowstone is the emergence of an ecosystem that is more normal for the region and one that will support greater biodiversity. 

He says as one of the area's few deciduous trees, aspens are important because birds, insects and various kinds of plants thrive in their stands.

"As well as providing habitat and food for deer and elk and other animals," Painter adds. "When you start seeing these aspen stands popping up and getting more dense, you start finding these animals using them. So, all these plants are important for the landscape, for the ecology."

Painter notes that restoring aspen in northern Yellowstone has been a goal of the National Park Service for decades, a goal he says it largely has reached by letting the animals do the heavy lifting.