Hydroelectric dams contribute more to global warming than previously estimated, according to a study published in BioScience.
It appears that the current and planned boom of hydroelectric projects would double the current cover of dams in the world and will aggravate the problem.
Researchers found that rotting vegetation in the water means that the dams emit about a billion tonnes of greenhouse gases every year. This represents 1.3% of total annual anthropogenic (human-caused) global emissions

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