Populated Areas the Hardest Hit There are now hardly any free-flowing rivers in heavily populated areas, with most confined to sparsely populated areas of the world such as the Arctic, Siberia, the Congo, and the Amazon. Rivers that have been heavily damned and fragmented include the Nile, Yangtze, and the Danube. The main reason for so many dams is the production of hydroelectricity, which with climate change is becoming an increasingly popular way of generating low carbon electricity and scientists have warned that the broader environmental costs of hydropower are not often taken into consideration. There are already around 60,000 large dams in the world, with another 3,700 under construction or in the planning phase. A separate study in Britain carried out by scientists at the University of Swansea looked at the effects of smaller infrastructure in rivers, such as weirs and culverts, and found that 97% of UK rivers have their flow interrupted by manmade structures. Carlos Garcia de Leaniz, who led the British research, thought the global study underestimated the extent of river fragmentation because it only considered very large dams. “We believe free-flowing rivers don’t exist anymore, at least in Europe,” he said.]]>