Do wolves help trees in Yellowstone flourish?

Gray wolves have caused problems for ranchers around Yellowstone National Park since their reintroduction in the mid-1990s, but their return has enabled other species to thrive in areas where they previously could not. They have curbed elk populations in the park, which has allowed aspen, willow and cottonwood trees to take root where the foraging herds once prevented their growth, Matthew Brown of The Associated Press reports.

Other factors such as changing climate and wildfires can play a role in new tree growth, but the wolf is the protagonist, says Oregon State University researcher William Ripple, who discovered the phenomenon. Ripple told AP that wolves "are more than just charismatic animals that are nice to have around. We're finding that their function in nature is very important." Wolves control the elk, trees grow in their place, and as a result there is more habitat for songbirds and more food for beavers, who in turn dam streams, creating ponds that attract fish, reptiles and amphibians.

Some scientist dispute Ripple's findings. Matthew Kauffman of the U.S. Geological Survey told Brown elk only slightly alter their behavior to avoid wolves, and herd numbers would have to drop even more for aspen populations to fully recover. Others say Ripple's work ignores factors such as drought and stream levels which also affect tree growth. (Read more)