11 December 2017
How Has Wolf Reintroduction Affected the Yellowstone Environment?
The wolves of Yellowstone have an interesting history. By the end of the 1920s almost
all of the United States' wolves were killed off, predominantly by ranchers protecting their
livestock. With the population decimated, Yellowstone National Park began the reintroduction of
the gray wolf in 1995. In December 2014, the wolf population was an estimated 104 wolves in
11 packs. Many scientists debated wolf reintroduction, questioning the upside. There was a large
handful that felt wolves would primarily feed on livestock, and also worried about their effect on
a historically low elk population. That being said, scientists took a calculated risk in their
decision to bring back many park goers favorite predator. Despite having a bad reputation, the
reintroduction of gray wolves into Yellowstone has had a positive impact on the environment.
“Yellowstone wolves are causing a trophic cascade of ecological change, including
helping to increase beaver populations and bring back aspen, and vegetation,” said Doug Smith,
a wildlife biologist in charge of the Yellowstone Wolf Project. Smith continues, writing, “When
the gray wolf was reintroduced into the Greater Yellowstone Ecosystem in 1995, there was only
one beaver colony in the park.” There are now 9 beaver colonies in Yellowstone, and that
number may still be on the rise.
In the 1920’s Yellowstone killed off its wolf population, taking loads of predatory
pressure off the elk. Elk populations skyrocketed in the park. The increased number of elk in the
park largely stayed put in the winter, with no predators to keep them moving. During the winter
months, the elk browsed heavily on willow plants, leaving little food for the beaver. According
to Smith, this created a counterintuitive problem. Smith claimed, “In 1968, when the elk
population was about a third what it is today, the willow stands along streams were in
historically bad condition. Today, with three times as many elk, willow stands are robust.” This
is all thanks to the fact that the wolves keep the elk moving throughout the winter. The elk never
have the opportunity to clear out a section completely before being chased out by the wolves,
leaving food left over for a flourishing beaver population.
An increased beaver population also has a monumental impact on the natural
environment in the park. Beavers affect their environment by building dams on the many calm
streams of Yellowstone National Park. The dams result in flooding creating small ponds. These
ponds effectively nurture the soil in the immediately surrounding areas, thus vastly improving
the growth of vegetation throughout the park.
As many researchers have noted, the impact of the gray wolf stretches far beyond the
skyrocketing beaver population. Since gray wolves have returned to Yellowstone, the deer and
elk have gotten stronger. The aspens and willows have returned to...