San José, Costa Rica, since 1956

To Dam… Or Not to Dam?

Once considered the cleanest, most efficient form of renewable energy, dams are falling from grace.

The findings of the World Commission on Dams (, an independent, international, workgroup that addressed issues with large dams, concluded that “the ecosystem impacts are more negative than positive, and they have led, in many cases, to significant and irreversible loss of species and ecosystems.”

Effects to fish and invertebrate populations in rivers, as well as the surrounding wildlife and vegetation, are well documented.

Recent studies conducted by Brazil’s National Institute for Space Research (INPE), also warn that the world’s large dams emit 104 million metric tons of methane annually – 23% of the world’s human-induced methane emission total, driven mostly by decaying organic material beneath impoundments.

Methane is a much more potent greenhouse gas than carbon dioxide, say scientists.

The same study found that large hydropower reservoirs in the tropics may have a higher global warming impact per kilowatt hour than the burning of fossil fuels, including coal.

Others believe these claims to be exaggerated by the anti-dam contingent.

The Costa Rican Electricity Institute (ICE) says hydropower, while not perfect, remains the most viable option, in terms of economics and environment.

“Faced with increasingly unpredictable weather and growing demand for energy, the best option we have is to build impoundments that store water, so that we can control and regulate generation as we see fit,” said ICE’s Roberto’s Jiménez.

“Otherwise, we’ll be forced to burn fossil fuels.”


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