Scientists say re-introducing keystone species back to the wild could cause a cascade that would change landscapes.
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's Dana Lewis reports on how "rewilding" can renew fragile ecosystems.