A population of beavers living on a Devon river will be allowed to stay in the wild if they are tested and proved to be disease free, Natural England announced today.

Following an intense campaign by Devon Wildlife Trust (DWT) with the support of many local people, the beavers will become part of a five-year trial conducted by the DWT to assess their impact on the waterways, fish populations and the wider environment.

The beavers are thought to have been resident on the River Otter in south-east Devon for at least the last three years though they were only filmed for the first time in early 2014. Their origins are uncertain but may be the result of an illegal introduction.

Devon Wildlife Trust believes that the beavers' activities – tree-felling and dam-building – will have a positive impact on water flow and quality throughout the catchment area and also create rich habitats for other wildlife.

However, angling bodies such as the Angling Trust and some landowners have opposed the move claiming that the beavers' dams will negatively impact on migrating fish and may also cause flooding.

A report released on 28 January in Scotland examining the potential impact of wild beaver populations in Scotland on salmonids found both positive and negative impacts – and stressed the need for careful management of the wild mammals.

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Speaking about today's decision on the Devon beavers, Chairman of Natural England Andrew Sells, said:

"We have considered this application very carefully. Responses to our written consultation and public meetings have been generally positive and we are now satisfied with Devon Wildlife Trust's plans for managing and monitoring the project."

Peter Burgess of the DWT said: "This project will measure the impact that these beavers have on the local environment, on the local economy and on local people. The evidence from elsewhere shows that beavers should have an overwhelmingly positive effect, but this is the first time the animals will be living in a well-populated, agriculturally productive English landscape for hundreds of years.

"We need to ensure that any negative impacts of beavers are avoided. This will mean working alongside the Environment Agency, local authorities and landowners to manage any problems that may arise over the coming years.’

A final decision on the beavers' future will be made at the end of the trial in 2020.

Fallen tree
Evidence of beavers at work near the River Otter in Devon.