| By: Whitney Rothwell |

A new study has found that beavers could help clean polluted rivers and slow the loss of soil from farms. The study was led by hydrologist professor Richard Brazier of the University of Exeter, using a captive beaver trial-run by the Devon Wildlife Trust. 

A family of beavers, who have lived in a fenced site at a secret location in West Devon since 2011, built 13 dams which slowed the flow of water and created a system of deep ponds along the course of what used to be a small stream. 

“Were beaver dams to be commonplace in the landscape we would no doubt see these effects delivering multiple benefits across whole ecosystems” – Richard Brazier

Researchers measured the amount of suspended sediment, phosphorus, and nitrogen in the water as it runs into the site and compared this to the water running out of the site after having passed through the beaver dams. 

The results showed that the single family of beavers had trapped 100 tonnes of sediment in their dams. Seventy percent of this was soil eroded from “intensively managed grassland” fields upstream. The results also showed that this sediment contained high concentrations of nitrogen and phosphorus. Nitrogen and Phosphorus are nutrients known to cause problems for wildlife in rivers and streams and are also removed from drinking water supplies.

Professor Brazier said: “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. 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.”

Devon Wildlife Trust has conducted the enclosed beaver trial for seven years and has also run another beaver project since 2015 involving a population of wild beavers in East Devon.