Beavers have bounced back and are re-engineering the landscape in parts of Canada they occupied before they were almost wiped out by the fur trade over four centuries from 1600, said the man who found the world’s largest beaver dam in Wood Buffalo National Park, which straddles Alberta and the Northwest Territories.

“They’re invading their old territories in a remarkable way in Canada,” said Dutch-born landscape ecologist Jean Thie in 2010. “I found huge dams throughout Canada, and beaver colonies with up to 100 of them in a square kilometer.”