CORVALLIS, Ore. The wolves are back, and for the first time in more than 50 years, young aspen trees are growing again in the northern range of Yellowstone National Park.
The findings of a new study, just published in Biological Conservation, show that a process called the ecology of fear is at work, a balance has been restored to an important natural ecosystem, and aspen trees are surviving elk browsing for the first time in decades.
The research, done by forestry researchers at Oregon State University, supports theories about trophic cascades of ecological damage that can be caused when key predators in this case, wolves are removed from an ecosystem, and show that recovery is possible when the predators are returned. The results are especially encouraging for the health of Americas first national park, but may also have implications for other areas of the West and other important predators.
After an absence of 70 years, wolves were re-introduced to Yellowstone Park in 1995, and elk populations began a steady decline, cut in half over the past decade. Also, the presence of a natural predator appears to have altered the behavior of the remaining elk, which in their fear of wolves tend to avoid browsing in certain areas where they feel most vulnerable. The two factors together have caused a significant reduction in elk browsing on young aspen shoots, allowing them to survive to heights where some are now above the animal browsing level.
This is really exciting, and its great news for Yellowstone, said William Ripple, a professor in the OSU College of Forestry. Weve seen some recovery of willows and cottonwood, but this is the first time we can document significant aspen growth, a tree species in decline all over the West. Weve waited a long time to see this, but now were optimistic that things may be on the right track.