We were just trying to help. Turns out the efforts of humankind to save beavers from extinction over the past century have had an eco-unfriendly side effect: The animals, whose population has rebounded, are contributing to climate change, researchers say at EurekAlert. Beaver dams create shallow ponds, which can host growing levels of carbon as biological material accumulates on the floor. The result is methane, a greenhouse gas that doesn't dissolve in the ponds; instead, it travels into the atmosphere. These days, beaver ponds release 200 times more methane than they did in 1900, when centuries of hunting threatened the animals with extinction.
Today, the animals are definitely doing better; in fact, there are about 10 million of them, researchers in Canada figured in a new study. One result of that is some 16,000 square miles of dammed ponds, which has led to the release of some 882,000 tons of methane, or 15% of what deer, antelope, and other cud-chewing wild creatures produce. And that figure could grow, says a researcher. Beavers aren't the only rodents to blame for climate change, the Independent reports: Arctic squirrels are doing their share, too, say US scientists. They dig burrows, which warms the ground and helps melt permafrost, where carbon has been building up "for tens of thousands of years," an expert explains. (Meanwhile, swamp rats are shrinking Louisiana.)