How reintroducing wolves helped save a famous park (video)

Wolves had been absent from Yellowstone National Park for more than 70 years when they were reintroduced in the 1990s -- and their return had some surprising benefits. Wolves were once the top predator in America's world-famous Yellowstone National Park. But the population was eradicated in the 1920s, leaving the wilderness wolf-free for seven decades. - Science & Environment Animal Ecology Nature Sustainability