The following video was created from chunks of George Monbiot’s TED talk. The video, which shows how the reintroduction of wolves into Yellow Stone Park back in 1995 has not only drastically improved the ecosystem of the area, but is actually directly connected to actual physical changes in the landscape of the rive itself.

When wolves were reintroduced to Yellowstone National Park in the United States after being absent nearly 70 years, the most remarkable “trophic cascade” occurred. What is a trophic cascade and how exactly do wolves change rivers? George Monbiot explains in this movie remix.