Deforestation: damage from dams adds to emissions

Sir

In your Special Report 'Brazil goes to war against logging' (Nature 452, 134–135; 2008), you argue that the Brazilian government is willing to stop logging operations on the Amazon and to push down Brazil's greenhouse-gas emissions. But the Brazilian government still plans to build several hydroelectric power plants on the Amazon (see http://tinyurl.com/5hb6st), which could increase both deforestation and greenhouse-gas emissions.

Dams flood thousands of hectares of forest and threaten many aspects of the Amazon basin. Some are already being built in the Amazon headwaters and will interfere with the migratory route of economically and ecologically important fish. The previous construction of such barrages was a huge mistake, as sediment transportation to the lowlands (where soil is poor) was blocked and the excess of dead trees in the reservoir caused high water eutrophication.

Dams have also been implicated in methane and carbon dioxide emissions, in part because of organic-matter decomposition in the reservoirs. These emissions from artificial lakes should be considered along with Amazon logging and burning in calculations of Brazil's total greenhouse-gas emissions.

The Brazilian government needs to look at some proposed solutions, such as renewing non-productive 30-year-old dams (already built next to energy-consuming regions, but they would keep methane emissions at today's levels) or imposing a solar-energy policy that could reduce greenhouse-gas emissions if dams were decommissioned. Unfortunately, it does not look as though this will happen.

See also Deforestation: call for justice, not militarization

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Barbosa, A. Deforestation: damage from dams adds to emissions. Nature 453, 280 (2008) doi:10.1038/453280b

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