From the NYT:
The focus is the huge Belo Monte dam planned by the Brazilian government. It would be the third largest in the world, and environmentalists say it would flood hundreds of square miles of the Amazon and dry up a 60-mile stretch of the Xingu River, devastating the indigenous communities that live along it. For years the project was on the shelf, but the government now plans to hold an April 20 auction to award contracts for its construction.
Stopping the dam has become a fresh personal crusade for the director, who came here as indigenous leaders from 13 tribes held a special council to discuss their last-ditch options. It was Mr. Cameron’s first visit to the Amazon, he said, even though he based the fictional planet in “Avatar” on Amazon rain forests. Still, he found the real-life similarities to the themes in his movie undeniable.
The dam is a “quintessential example of the type of thing we are showing in ‘Avatar’ — the collision of a technological civilization’s vision for progress at the expense of the natural world and the cultures of the indigenous people that live there,” he said.
Here is the wiki on the Belo Monte Dam. It is the old story of taking things from others by force, the story of national entities and identities forged in violence, for the benefit of companies run by the corrupt.