Trophic Cascade - How Wolves Change Rivers

When we try to pick out anything by itself, we find it hitched to everything else in the Universe.
— John Muir

Wolves were reintroduced to Yellowstone National Park after 70 years, a "trophic cascade" happened.

This video from Sustainable Man accompanies narration from George Monbiot's TED Talk: "For more wonder, rewild the world"  Watch the full talk.