Wolves back in Yellowstone benefit the ecosystem, scientists say

When rangers killed two gray wolf pups near Soda Butte Creek in Yellowstone National Park – in the year 1926 – it was the last official kill of wolves in Yellowstone. The species (Canis lupus) was absent from the park for 70 years. Then in 1996, amid controversy, the National Park Services reintroduced gray wolves into the park. Today, the wolves, which are considered “top predators,” are benefiting the Yellowstone ecosystem, scientists at Oregon State University said on December 21, 2011.

These scientists took the occasion of the 15th anniversary of the return of the wolves to Yellowstone to announce that “a quiet but profound rebirth of life and ecosystem health is emerging” in the park. Yet controversy surrounding the wolves remains.

The Oregon scientists said in their announcement that the wolves hold the elk population at bay and also prevent over-grazing by the elk. They point to the intricacy of the Yellowstone ecosystem, which is mainly in Wyoming, overlapping into Idaho and Montana. The wolves prey on the elk (Cervus elaphus), for example, which in turn graze on young aspen and willow trees in Yellowstone, which in their turn provide cover and food for songbirds and other species. The Oregon scientists suggest that, as the elks’ fear of wolves has increased over the past 15 years, elk “browse” less – that is, eat fewer twigs, leaves, and shoots from the park’s young trees – and that is why, the scientists say, trees and shrubs have begun recovering along some of Yellowstone’s streams. These streams are now providing improved habitat for beaver and fish, with more food for birds and bears, according to the Oregon scientists.

The announcement from Oregon comes on the heels of a major international study from earlier in 2011 suggesting that the loss of large predators is disrupting ecosystems in many parts of the world.

Yet, over the 20th century, the relationship between elk and wolves in Yellowstone has been and remains controversial. It started when a team of scientists visited Yellowstone in 1929, after the wolves had been absent for just three years, and again in 1933, and reported:

The range was in deplorable conditions when we first saw it, and its deterioration has been progressing steadily since then.

The scientists who visited in the early 20th century blamed the absence of wolves in the park on the poor condition of the landscape, but not everyone agreed with them. Even today, a National Park service website states clearly:

In response to continuing controversy over Yellowstone elk, in 1986 Congress ordered studies on the effects of natural regulation. This research initiative resulted in more than 40 projects by park biologists, university researchers, and scientists from other federal and state agencies, who have made substantial progress in clarifying the complex ecology of wildlands. The research demonstrates that the northern range continues to support large, healthy ungulate herds [elk, bison, pronghorn, deer, bighorn sheep, and moose] year after year, and that despite certain localized impacts, elk do not appear to have had any significant effect on the overall biodiversity of native animals and plants. Visible changes in vegetation such as a browse line on Douglas-fir stands and a lack of aspen reproduction are not simply the result of elk “overpopulation,” and may be part of long-term ecological processes we are only beginning to understand.

Meanwhile, the Oregon scientists have created the following video, which they say demonstrates the effect of the elk – and the effect of the return of the wolves on the elk – in Yellowstone:

On March 1, 1872 – when Yellowstone National Park became the first national park in the world – the primary goal was preservation of the area’s geysers and other geothermal wonders. Who knew that managing the park’s wildlife would be necessary, or such a complex problem?

In the park’s first years, people were free to kill any game or predator they came across. As a top predator – with few or no natural predators of its own – the gray wolf was considered an undesirable and dangerous animal, and so was especially vulnerable to the guns of human hunters. Public hunting was outlawed quickly, though, after the U.S. Army took over administration of the park in 1886. But even then the Army and other park personnel killed gray wolves, so that, by 1926, wolves were gone from Yellowstone.

On December 24, 2011, the Los Angeles Times reported that a lone gray wolf wearing a GPS collar is now “a day or two’s trot” away from California. If OR7, as he is known, crosses the California border, he will be the first wild wolf recorded in the Golden State since 1924. The LA Times said:

That prospect is thrilling to conservationists but chilling to ranchers, who have lost livestock in other parts of the West.

Are there any easy answers here? No. But clearly we humans – whose population grew to an estimated 7 billion in 2011 – will need to keep asking questions about the relationship between gray wolves, elk, aspen and willows, songbirds, and, yes, ranchers in the vicinity of Yellowstone National Park.

Bottom line: Scientists at Oregon State University announced that the return of the wolves to Yellowstone is benefitting the park’s ecosystem. This announcement comes amid a continuing controversy about the wolves and their prey and the overall impact of wolves in Yellowstone.

Loss of large predators has disrupted multiple ecosystems

Joel Cohen: Top 10 key population trends on Earth with 7 billion

December 27, 2011

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