Tensions are so high over a proposed dam in the Brazilian Amazon that violence broke out at a May meeting in the city of Altamira to discuss the project. A thousand indigenous people from 26 ethnic tribes crowded into a high school gymnasium. Members of the the Kayapó, Juruna, Arara, Xipaia, Kuruaia, and other tribes that live along the mighty river’s second longest tributary, the Xingu, don’t get together in Altamira very often. But the $6.6 billion dam, called the Belo Monte, that Brazil’s electric utility, Electronorte, plans to build along the 1,200-mile Xingu River will affect them all. It would be the world’s third largest dam, with a potential installed capacity of 11,181 MW—and its reservoir would flood 100,000 acres, putting many tribal lands underwater.

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