June 4, 2012

Megadams worse than thought for environment

sheyla_yakarepi_at_london_dam_protest_020311.jpgMegadams create social upheaval and are worse than at combatting climate change

A series of new megadams are proposed and some now being built in the Brazilian and Peruvian Amazon, but a new report published in Nature Climate Change journal claims that tropical dams are being treated as a solution to climate change despite the reality that they emit significant greenhouse gas emissions.


The report authors – Philip Fearnside and Salvador Pueyo – argue that there are serious errors in calculations by energy companies such as ELECTROBRÁS which is behind the new Amazon megadam projects.  According to the authors, the myth can no longer be sustained that tropical dams produce clean energy.

“Various mathematical errors have resulted in Brazil’s electrical authorities estimating the magnitude of emissions from reservoir surfaces at a level of only one-fourth what it should be,” write Fearnside and Pueyo.  They go on to suggest that ELETROBRÁS’s estimates should be 345 percent higher.


One of  ELETROBRÁS’s hydroelectric megadam proposals targets the Rio Ene in Peru with a 2,200MW project that will displace 10,000 indigenous Asháninka from their traditional heartland, villages and best garden sites.  Furthermore, it proposes to flood over 180,000 acres of forest.  In Brazil, the construction of the controversial Belo Monte dam is about to displace 20,000 local people,, including indigenous communities, as it floods tens of thousands of hectares of Amazon rainforest.

The carbon released from soil carbon stocks as well as dying forest vegetation could represent millions of tons on CO² emitted to the atmosphere as a direct result of damming the main headwaters of the world’s biggest river.  Also, of course, 180,000 acres of rainforest, which is presently a carbon sink, will no longer fulfill that function.   Even worse, says the report, when organic matter decays under the low oxygen conditions found at the bottom of reservoirs it forms methane which is a greenhouse gas with a much greater adverse impact on global climate change.  Methane release is also facilitated by a dam’s hydro turbines, which tend to draw on water from the bottom of the reservoir.

In theory, it would be possible to capture much of the methane produced, but nothing can compensate for the social upheavals and the loss of forest and gardens which is the consequence of these megadams for local communities.

Sources: Mongabay and Nature Climate Change (Vol 2, June 2012)



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