The keystone at the top of an arch holds all the stones in place. Without it, the arch collapses. Healthy ecosystems needs keystones—like wolves and whitebark pines—to function. Keystone species are the architects of biodiversity.
In the absence of wolves in Rocky Mountain and Yellowstone National Parks, elk browsed willows in river and creek bottoms excessively. Now that wolves are back in Yellowstone, riparian areas have come alive as long-suppressed cottonwoods and willows are growing, providing vital habitat for songbirds. Beaver have also returned, influencing water quality.
Wolves also play an important role in regulating other predators. With fewer coyotes, antelope fawn survival has increased dramatically.
Grizzly bears play a highly complex role in ecosystems. In addition to predation on elk and moose calves, grizzlies disperse seeds over large areas, and contribute to nutrient cycling. Dubbed “ecosystem engineers” by some, the foraging activities of grizzly bears may build or change the ecosystem. For example, coastal brown bears transfer salmon-derived nitrogen into riparian ecosystems when they kill, move, eat, and leave some fish in the forest.