Brazil's rainforest is under further threat from plans to build a giant hydroelectric dam on the Xingu River, a tributary of the Amazon River in Pará state. Plans for the dam, known as Belo Monte, have been approved by the environment agency. These come on top of pending changes to the Brazilian Forest Code that could allow deforestation of up to 20 million hectares of rainforest (Nature 476, 259–260; 2011).

The US$17-billion dam, together with four planned upstream dams, will have a combined hydroelectric potential of 21,600 megawatts. Leaders of the Brazilian energy sector argue that the dams could help to preserve the Amazon. But their construction will flood vast areas of tropical rainforest, jeopardizing ecosystem functions and species survival, increasing greenhouse-gas emissions and displacing tens of thousands of forest peoples.

Brazil is a world leader in clean-energy production. However, the dams will release into the atmosphere enormous quantities of methane — a greenhouse gas that is 25 times more potent than carbon dioxide.

Much of the electricity generated by Belo Monte is likely to be used in the production of aluminium ingots for export (see, making the environmental and social impact of the dam's construction even harder to justify.

Brazil must strive to control deforestation more effectively by strengthening its forest laws and consolidating the United Nations' REDD policy (for 'reduced emissions from deforestation and forest degradation'). Otherwise, the steady destruction of the country's tropical rainforest will have consequences well beyond its borders.