How Beavers Could Help Clean Up Polluted Waters Around the World

Beavers are a lot more impressive than you might think. These semiaquatic rodents can build dams as large as 2800 feet deep, thanks in part to their super sharp teeth and sturdy tails that keep them from tipping over while hauling heavy materials into the water. According to research from scientists at the UK-based University of Exeter, the animals could also potentially help clean up polluted waterways.

Professor Richard Brazier and his colleagues studied the water quality at the site of a fenced-in area in southwest England, where a family of captive beavers has been living since 2011. The water flowed from nearby fields to a local river, where it deposited sediment while passing through 13 dams that had been built by the beavers.

The reduced water flow—and the deep ponds that formed as a result of the dams—had a filtering effect. The beavers’ dams captured more than 100 tons of soil and other sediment that contained high levels of nitrogen and phosphorus, both of which are bad for wildlife and human consumption.

The runoff problem is also twofold: The erosion of soil on agricultural land has both economic and environmental consequences. Scientists suggest that the reintroduction of the Eurasian beaver to rivers could help curb some of this damage. These “ecosystem engineers,” as the animals are called in the University of Exeter study, were believed to have been hunted to extinction in Britain by the 1500s. However, a colony was found in Scotland a decade ago, and there have been some efforts since then to release beaver populations into the wild.

"It is of serious concern that we observe such high rates of soil loss from agricultural land, which are well in excess of soil formation rates,” Brazier said in a statement. “However, we are heartened to discover that beaver dams can go a long way to mitigate this soil loss and also trap pollutants which lead to the degradation of our water bodies. Were beaver dams to be commonplace in the landscape we would no doubt see these effects delivering multiple benefits across whole ecosystems, as they do elsewhere around the world."

In a separate study from 2015, scientists at the University of Rhode Island determined that larger beaver ponds were able to remove up to 45 percent of nitrogen in the water that passed through them, while smaller ponds removed roughly 5 percent. The North American beaver was also on the brink of extinction in the 1800s, but these populations have since rebounded in Rhode Island and other parts of the continent.