A new WWF report warns that indiscriminate dam-building is threatening the world's largest and most important rivers. The WWF report, Rivers at Risk identifies the top 21 rivers at risk from dams being planned or under construction. It shows that over 60 per cent of the world's 227 largest rivers have been fragmented by dams, which has led to the destruction of wetlands, a decline in freshwater species - including river dolphins, fish, and birds - and the forced displacement of tens of millions of people.