2 June 2000
WCD Response to New Scientist article
"Dear Sir, Your article 'Raising a stink - rotting vegetation in hydro dams stokes global warming', referring to 'a report of the World Commission on Dams', gives the unduly simplistic impression..."

Dear Sir,

Your article “Raising a stink - rotting vegetation in hydro dams stokes global warming”, referring to “a report of the World Commission on Dams”, gives the unduly simplistic impression that the observed greenhouse gas (GHG) emissions from a few Brazilian dams means that all dams are bad

Contrary to your article, reservoirs in boreal areas and at least half the Brazilian dams studied appear, on balance, to be more effective at avoiding GHGs than the thermal alternative. More importantly, your correspondent ignored the emphasis on GHG emissions from natural habitats. Undeveloped Amazonian floodplains emit substantial quantities of methane. So it is therefore incorrect to conclude that “a reservoir will produce more methane than the river did before the dam was built”.

The workshop report of the World Commission on Dams, which incidentally reflects the views of the participants, not those of the commission, emphasises the scientific complexities involved with increasing power production while reducing life cycle emissions from dams or other energy options.

Yours sincerely,

Jamie Skinner

Senior Advisor - Environment
World Commission on Dams

Dear Sir,

Fred Pearce's report will help alert the public and decision makers to reject the dam industry's claims that hydropower is a "carbon-free" electricity source.

One major greenhouse-gas emitting reservoir that Pearce did not mention lies behind the huge Tucuruí Dam in the Brazilian Amazon. Recent calculations by Philip Fearnside of the National Research Institute of the Amazon indicates that in 1990 this 2430-square-kilometre reservoir had as much impact on global warming as all the fossil fuels burned by the 17-million-strong population of São Paulo. The emissions are roughly equivalent to those of a gas power plant producing the same amount of energy as the 4000-megawatt Tucuruí.

Fearnside's latest estimate for Tucuruí emissions, which has not yet been published, is more than twice an earlier estimate, mainly because he takes account of recent research showing substantial methane emissions from dam turbines and spillways.

The World Commission on Dams, which appears to seek to downplay the significance of its own findings on reservoir emissions, stresses that natural wetlands in the Amazon emit substantial amounts of methane, so flooding these wetlands with reservoirs may not significantly increase emissions.

Fearnside, however, explains that little of the land flooded by Tucuruí was wetland.

Patrick McCully
International Rivers Network
Berkeley, California