FOR 70 years, trees alongside the rivers in YellowstoneNational Park wouldn’t grow. Shoots sprang up but soon disappeared. Forest rangers suspected elk were eating the seedlings, but they couldn’t figure out what to do about it.
Then, about six years ago, things changed. The elk moved away from the rivers and into the woods, and the trees grew again. Why? It wasn’t drought or fire or floods or any other natural disaster.
They had happened before. No, there was only one possible reason. Wolves were killing the elk. Seventy years ago gray wolves were eliminated from Yellowstone because they killed livestock and wrecked crops.
BUT in 1995, the U.S. Fish and Wildlife Service put 15 gray wolves from Canada back into the park to restore Yellowstone’s natural habitat.
The results have been spectacular. Today, the park has 250 to 300 wolves, and the Fish and Wildlife Service likely will take them off the Endangered Species list soon. But even more important, it turns out the wolves are a “keystone species.”
Everything they do affects everything else that happens in the park. The result is that Yellowstone is becoming more like it was when there were no humans to interfere.
THE trees’ return was reported late last year, but the trees are only one end of a long series of environmental events: Wolves hunt the elk, so the elk leave the rivers. The willows, cottonwoods and aspens grow, casting shade that cools the water to temperatures favored by trout. Migratory birds return to roost in the new foliage.
But it does not stop there. In 1996, there were no beavers in Yellowstone, but today there are seven colonies, because the beavers can eat the low hanging willow branches. And the beavers build dams, creating marshland that brings back otters, mink, muskrats and ducks. It may take 20 or 30 years before the wolves change things completely, but Yellowstone is a perfect laboratory – a place where you can’t hunt and can’t farm. At 2.2 million acres, it’s very big.
WHEN the wolves first came back, there were 17,000 elk in Yellowstone.
Weighing as much as 700 pounds, the elk had no serious rivals, and at first ignored the 100-pound wolves the way they ignored 35-pound coyotes.
This was a big mistake. Today Yellowstone has about 8,000 elk. But scientists say this is just the way nature meant things to be. Every elk that’s killed by wolves provides a meal for ravens, magpies, golden eagles, bears, bald eagles and coyotes, not to mention smaller mammals and insects. And once the elk become harder to find, the wolves will have to go after even bigger animals– moose and bison.
