The environmental and social cost of major dam projects around the world has been unacceptably high, even though many of them have provided significant economic benefits, says a global assessment that is expected to influence future consideration of dam developments.
The World Commission on Dams, which released its report in London last week, proposes new frameworks for deciding whether dam projects are really needed and for planning those that do proceed.
The report has been welcomed by ecologists and health researchers, many of whom have criticized national governments and agencies such as the World Bank for ploughing ahead with large dam projects in the face of environmental objections. “It represents a unique body of knowledge that has not been accessible before,” says Adrian Sleigh, a researcher into tropical public health at the University of Queensland in Brisbane.
The commission is an international 12-member panel representing such diverse interests as commercial dam builders, indigenous peoples and environmental organizations. It functions independently, but is sponsored by the World Bank and other interested organizations.
It estimates that the 45,000 large dams around the globe have cost over $2 trillion to build and are responsible for about 20% of the world's power and 15% of its food supply. The report says that although dams can have positive ecological effects, such as establishing new wetland habitats, their overall effect on the environment has been negative because of loss of habitat, species reductions and other problems. In addition, dams have displaced between 40 million and 80 million people from their homes.
Deborah Moore, a member of the commission and a consulting scientist with Environmental Defense, a non-profit organization based in New York, says that few of the dams have been properly evaluated on their performance in producing energy, controlling floods or delivering water supplies. But the commission's study suggests that large dams have typically not met their intended goals.
The report calls for long-term monitoring of dam performance to maximize efficiency and reduce harmful effects. And it strongly urges planners to consider potential alternatives to dams, such as better management of existing resources and interconnection of power grids.
The commission adds that when dam projects do proceed, social and environmental effects should be considered just as important as economic ones — in contrast to current standard practice. It also urges that people affected by projects be allowed to participate in planning, and that developers should be held contractually accountable for accomplishing agreed goals.
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Regional Environmental Change (2013)