We in Washington have been hearing plenty about the Elwha dam removal (see it live here!). While ecological effects of such a giant project will take years to assess, the removal itself might be a hallmark of shifting perceptions about the costs and benefits of damming rivers.

This shift might have begun around 1978 with Tennessee Valley Authority v. Hill, a 1978 ruling in which the Supreme Court ruled that a project to build the Tellico Dam on the Little Tennessee River had to be halted because it would likely lead to the extinction of the snail darter. Retired Supreme Court Justice John Paul Stevens’ memoir about this case is released today, amidst plenty of other dam news.

Internationally, both Brazil and Myanmar halted giant, expensive dam projects this week.  The dam in Myanmar would have flooded an area about the size of Singapore, creating a 766 sq km (296 sq mile) reservoir, mainly to serve growing energy needs in northern neighbor China, which would have imported about 90 percent of its power. After weeks of rare public outrage against the Myitsone dam, President Thein Sein told parliament his government had to act “according to the desire of the people”.

These decisions relate also to the riverine ecosystems that are often irrevocably altered. In Brazil, the hydroelectric dam is seen to threaten fishing on the Xingu River. Brazil’s government strongly backs the project, which when completed would make the dam the world’s third-largest hydroelectric energy producer, and said it planned to appeal.

The ecological effects of dams are still being understood. Today the United States Fish and Wildlife Service has announced that it will begin a review process to determine whether the American eel qualifies for federal protection as an endangered species, as the eel has been driven from parts of its historical freshwater habitat mainly because of dams built in the 1960’s but also because of harvesting, degradation of freshwater streams and turbine mortality.