You often hear about animals disappearing from nature from over hunting' or urban sprawl. But there is some good news in the form of animals being re-introduced to the wild.

Beavers were brought back in Britain's River Otter after 500 years while wolves were re-introduced to America's Yellowstone National Park in 1995 after an absence of 75 years.

They are called a keystone species that can create a cascade of life in the river.

TRT World'sDana Lewis reports on how "rewilding" can renew fragile ecosystems.