Aspen trees are making a comeback in Yellowstone National Park, and according to a new study out of Oregon State University, that’s thanks to wolves.
For much of the last century, elk were eating young aspen roots and shoots, leaving park managers concerned the trees were being eliminated. When wolves were reintroduced a couple decades ago, it created a new predator that’s pushing a majority of elk to winter outside the park.
Luke Painter, co-author of the study, said the return of aspens isn’t just because of wolves, but it wouldn’t have happened without them.
"There’s predation by grizzlies and cougars. There’s hunting outside the park. And there’s also more food for elk outside the park now then there used to be with irrigated fields and so forth. So, wolves have added to that equation,” Painter said.
With fewer predators and more food, that has significantly added to the number of elk wintering outside Yellowstone, and that helps aspens.
“Now, we have most of the elk are wintering outside the park, this winter was about three-quarters of the herd was outside the park in the annual count and before, up until the time when wolves came in actually, three-quarters of the herd was actually inside the park,” Painter said.
He said recovery of aspen is still in its early stages but will likely continue. The deciduous tree is important to the park’s biodiversity because it supplies nutrients for several bird and insect species.