When Yellowstone National Park was first established, there were wolves involved as part of the ecosystem. The wolves, though, disappeared: their numbers dwindled until they were totally gone. And then, the willows started disappearing as elk numbers soared, beaver numbers dropped, and the birds disappeared. How could this problem be fixed? In 1995, wolves were reintroduced to the ecosystem, and it started to correct itself. The top-down effect that having the wolves as predator in the ecosystem had was unbelievable, and replicatable in other areas as well. While solving the problems of ecosystems and global warming around the world isn't going to be as simple as balancing one ecosystem with one animal, it's a step in the right direction. This video, narrated by George Monbiot, tells this story. Monbiot considers himself a Rewilding campaigner, which means letting nature get "wild" again to save itself. Can rewilding succeed?