Brazil is in the midst of a dam-building spree in the Amazon basin that is changing the face of the world’s largest tropical forest region. The boom is driven by the country’s agricultural and heavy industrial interests, is being carried out with little regard to the impacts on indigenous people and the environment, is proceeding with little effort to capitalize on the nation’s vast renewable energy potential, and is often fueled by corruption.

The most notable example is the massive Belo Monte Dam, the world’s fourth-largest hydroelectric project. The dam itself has already blocked the 1,000-mile Xingu River, a ma