Scientists link world’s big dams to methane and global warming

Brazilian scientists say they have found evidence that the planet’s large dams emit nearly 115 million tons of methane every year, a figure that would put the water-control structures among the top contributors of human-caused greenhouse gases.

In a study released earlier this month, the scientists claim the world’s 52,000 dams contribute more than 4 percent of the warming impact linked to human activities. The study even suggests that dams and reservoirs are the single largest source of human-cased methane, a gas that traps heat in the atmosphere.


Environmental groups have rallied against dams for years, arguing that they destroy rivers and riparian habitat and wastewater through evaporation. The claim that the structures also cause global warming is new and is certain to be disputed by the hydropower industry as well as water supply managers.

“There is now more than enough evidence to show that large dams are a major source of climate-changing pollution,” says Patrick McCully, executive director of International Rivers Network. “Climate policy makers must address this issue.”

Arizona Republic