Efforts by many countries to reduce their carbon footprint by building hydroelectric dams could be misbegotten should these facilities also prove to be a major source of greenhouse gas emissions.

While dams have long been believed to make a major contribution to reducing carbon emissions by enabling the generation of renewable energy in the form of hydropower, researchers now suspect they could be one of the world’s leading sources of greenhouse gas emissions. The reservoirs created by dams generate copious amounts of methane as…