https://youtu.be/ysa5OBhXz-Q 

 At the Alladale Wilderness Reserve in Scotland they want to reintroduce the wolf. Fearful of large predators these efforts have so far been unsuccessful. With a better understanding we realize that predators have complex and important effects on ecological systems that not only alter species composition but also the land itself. "When we try to pick out anything by itself, we find it hitched to everything else in the Universe." - John Muir If we want a healthy, beautiful planet we have to leave large areas wild so that ecosystems can function and do their thing - rewilding. When we do we discover anew just how beautiful our planet is - without human interference. 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. Narration from TED: "For more wonder, rewild the world" by George Monbiot.