The Latest Climate Change Threat: Beavers

Methane emissions associated with the animals' prolific dam building are soaring even as the critters create habitat for wildlife.

(Photo: Jeff R. Clow/Getty Images)

Jan 6, 2015· 1 MIN READ
Padma Nagappan is a multimedia journalist who writes about the environment, renewable energy, sustainability, agriculture, and biotechnology.

The good news: Beavers are back. And they’re busy—in a big way. And that benefits the environment.

The bad news: Beaver-related emissions of methane, a potent greenhouse gas that contributes to global warming, are on the rise.

The dam builders are responsible for 800,000 metric tons of methane a year, which scientists estimate is 200 times more than the critters generated in 1900.

No, it’s not what you’re thinking. The source of all the methane gas those eager beavers generate is not their digestive system—unlike with cows—it's a result of building dams.

The world’s 10 million beavers have created 16,215 square miles of ponds—equal to the size of Switzerland—and 124,275 miles of shoreline habitat.

All of which provides a thriving environment for birds, deer, frogs, and fish and improves biodiversity and water quality.

In regions suffering from drought, the dams and ponds these hard-working creatures engineer also enrich the soil and retain water that would otherwise flow away.

Because beavers can restore damaged land much more cheaply than other methods, drought-stricken Western states have been laying out the red carpet for them.

The downside is the methane emissions associated with all that beaver business.

“When they establish ponds, the flow of water is reduced, so organic plant material gets accumulated in the ponds and settles at the bottom,” said Colin Whitfield, a hydrologist with the University of Saskatchewan who recently completed a two-year study on beavers and the emissions they generate. “The bottom of the pond is a low-oxygen environment, so when plant material decomposes, it becomes methane.”

“The good news is that beavers are unlikely to be a big driver of climate change,” Whitfield added. “The methane they generate is only 15 percent of what cud-chewing animals generate and less than 1 percent of the emissions from fossil fuel.”

But because the beaver population has changed so dramatically over the last 100 years, the emissions the animals indirectly generate are 200 times more than they were in 1900.

In the 19th century, trappers hunted beavers for their pelts, which were made into hats.

Beaver populations subsequently crashed, and so did demand for beaver fur hats. The timid creatures are native to North America, Europe, and parts of Russia. Once they were reintroduced, they multiplied like bunnies.

“As their numbers increase, so will the methane generated,” Whitfield said. “But they won’t have a major impact on pollution, because they’re the architects behind critical ecosystems and biodiversity.”