Scientific research has shown that the restoration of wolves can have a profoundly positive effect on the ecological health of the landscape. By culling the sick, old and weak, wolves improve the overall health, vigor, and genetic integrity of elk and deer herds. Through a cascade of interactions, the presence of wolves has been shown to increase the diversity of life throughout entire ecosystems, even in plant communities.
The Wolf's Place in the Wild
Following a 1930's field trip to an undisturbed region of the Sierra Madre in Chihuahua, Mexico, the famous conservation visionary Aldo Leopold wrote:
"Deer irruptions [population explosions] are unknown. Mountain lions and wolves are still common… There are no coyotes in the mountains… I submit for conservationists to ponder the question of whether the wolves have not kept the coyotes out? And whether the presence of a normal complement of predators is not, at least in part, accountable for the absence of irruption [of deer populations]? If so, would not our rougher mountains [in Arizona and New Mexico] be better off and might we not have more normalcy in our deer herds, if we let the wolves and lions come back in reasonable numbers?"
Leopold's insights were decades ahead of his time and uncannily accurate. Modern ecological research shows us that top predators, such as gray wolves, influence entire ecosystems through a cascade of effects through all the links in the food chain—the so called "top-down effect." Wolves keep populations of large herbivores like deer and elk in check so they don't destroy their own habitat by overgrazing or over-browsing their preferred food plants. The result is a more diverse and healthy plant community. Wolves also keep the number of mid-sized predators like bobcats and coyotes under control allowing populations of smaller animals to flourish in diverse habitats.
We can now see direct evidence of the effects of wolves in Yellowstone National Park. Following the 1995 reintroduction of wolves to Yellowstone, biologists have documented the return of willows and cottonwoods (long ago browsed to oblivion by over abundant and unwary elk) to stream banks. Songbirds have increased in both numbers and kinds, and long-absent beavers are returning to take advantage of the newly restored food supply. Beavers build dams that further diversify aquatic habitats for fish, amphibians, insects, and other plants and animals. The predatory actions of wolves also result in more food in the form of carcasses on the landscape. Animals now taking advantage of this newly restored food supply include grizzly and black bears, coyotes, foxes, weasels, eagles, ravens, vultures, a variety of smaller birds and mammals, and insects.
The result is an ecosystem that supports a more diverse assemblage of plants and animals. In short, the Yellowstone ecosystem is becoming more diverse and vibrant because of the return of wolves. Biologists generally agree that more diverse ecosystems are more stable and healthy than less diverse ecosystems. And healthy ecosystems are good for humans as well as the diverse plants and animals they support.
Wildlife biologists are anxious to learn how restoration of the Mexican wolf will affect ecosystems in the Southwest; but so far, there are simply too few wolves. Mexican wolves will need to be restored to more natural population densities before ecological benefits can be expected.