03 Jan 2012:
Return of Wolves Has Helped
Ecosystem Recovery in Yellowstone Park
The return of wolves to Yellowstone National Park has caused significant ecosystem recovery
by curbing populations of elk that for decades had over-browsed young aspen and willow trees, according to a new
U.S. Fish & Wildlife
study. In an analysis conducted by Oregon State University
, researchers found that tree stands and shrubs have recovered along some streams, improving habitat for beaver and fish and providing more food sources for birds and bears. In the 15 years since wolves were reintroduced to Yellowstone after being killed off last century, northern elk populations have decreased from more than 15,000 in the early 1990s to about 6,000 last year, according to the study published in the journal Biological Conservation
. By 2006, some aspen trees had grown tall enough that they were no longer susceptible to browsing by elk. As a result, along four streams in the Lamar River basin, less than 20 percent of the tallest young aspen sprouts were being browsed last year compared with 100 percent in 1998. “Yellowstone increasingly looks like a different place,” said William Ripple, an Oregon State professor and lead author of the study.
Yale Environment 360 is
a publication of the
Yale School of Forestry
& Environmental Studies
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