In 1995 wolves were reintroduced into Yellowstone National Park for the first time in 70 years.
Deer had overpopulated due to lack of predators causing them to depopulate the vegetation along the rivers. With the reintroduction of the wolves the deer learned to avoid the valleys and stay in higher ground.
This caused the vegetation along the rivers in the valleys to regenerate, resulting in new stands and forests of aspen, willow, and cotton trees.
With the return of the trees and vegetation, beavers, who are also ecosystem engineers, returned to the waters and began to build dams. These dams changed the ecology providing new homes for otters, muskrats, ducks, reptiles, and amphibians.
The wolves also killed coyotes and as a result of that the number of rabbit and mice began to rise.
Which in turn lead to an increase in the numbers of other predators such as hawks, eagles, weasels, badgers, and foxes.
But the most striking change was to the rivers. With the return of the trees and vegetation erosion slowed drastically and the rivers stopped meandering and became more stable.
All because a few wolves were brought back to Yellowstone.
Since wild wolves have returned to Yellowstone, the elk and deer are stronger, the aspens and willows are healthier and the grasses taller. For example, when wolves chase elk during the hunt, the elk are forced to run faster and farther. As the elk run, their hooves aerate the soil, allowing more grasses to grow. Since the elk cannot remain stationary for too long, aspens and willows in one area are not heavily grazed, and therefore can fully recover between migrations.
As with the rest of the country, coyote populations were nearly out of control in Yellowstone before the wolves returned. Now, the coyotes have been out-competed and essentially reduced by 80 percent in areas occupied by wolves. The coyotes that do remain are more skittish and wary. With fewer coyotes hunting small rodents, raptors like the eagle and osprey have more prey and are making a comeback.
The endangered grizzly bears successfully steal wolf kills more often than not, thus having more food to feed their cubs. In essence, we have learned that by starting recovery at the top with predators like wolves, the whole system benefits. A wild wolf population actually makes for a stronger, healthier and more balanced ecosystem. From plant, to insect, to people… we all stand to benefit from wolves.
Here is a fascinating short documentary on Yellowstone National Park, the first legislated National park in the world: