Beaver and cubs on the Otter Devon Wildlife Trust (Mike Symes)
The first beavers to live wild in England for centuries are to be allowed to remain on the River Otter in East Devon after a five-year reintroduction trial. Ecologist Paul Chanin reports on the Crediton link to this recent government announcement, the environmental benefits and challenges of beavers and the prospects of them returning to the River Creedy. 

Crediton has a place in the recent story of beavers because a national expert on the species lives nearby, in Hookway. Professor Richard Brazier from the Geography Department at Exeter University is supervising research on recently reintroduced beaver colonies on the river Otter in East Devon. He and his research team are studying the way they affect water flow and water quality and also the extent to which they may mitigate flooding and contribute to the storage of carbon thereby reducing its impact on the climate crisis. 

We don’t know when beavers became extinct in Britain, but they were still present in Somerset four or five hundred years ago as their bones have been found near Weston-super-Mare. It is possible that they survived until the early 1700s, though the evidence is not easy to interpret. 

They are in the news this month because the Government has accepted that the population on the river Otter can remain, once more, officially part of the English fauna. The decision is a landmark one, as it signals the first legally sanctioned reintroduction of an extinct native mammal to England. It means that the beaver population, which lives on the River Otter and is estimated to consist of up to 15 family groups, now has a secure future.

Beavers are already re-established in Scotland where they are a protected species. Around the country there are several semi-wild colonies in large enclosures, including one on a tributary of the Tamar in West Devon, not to mention a few escapees from wildlife parks. In the Forest of Dean beavers have been reintroduced to try to reduce flooding in the village of Lydbrook and there are plans to introduce captive colonies in Wales, Exmoor and the South Downs. 

When beavers are present, they have dramatic impacts on the way that water flows through the landscape. Richard Brazier’s research team has shown that during storms water flow is reduced by beaver dams because it is held back and released slowly. This reduces flooding because the water doesn’t all arrive in built up areas at the same time. 

Beaver dam. Mainly made from branches but with some stones (white objects) on top to increase stability

Slowing the water down also alleviates the effects of agricultural run-off and diffuse pollution by allowing silt to settle as the water flows through beaver ponds. During storms, silt was reduced by two thirds and nitrogen by a third. Only 5% of the phosphorus in water which entered the site was present when it left.  This storage of enriching nutrients reduces the risk of algal blooms and excessive growth of water plants elsewhere in the river as well as reducing silting in sensitive areas downstream. They also found that during the study 100 tonnes of silt was retained in the ponds made by one group of beavers. This contained 15 tonnes of carbon so beaver ponds are a carbon sink too.

Beaver pond with dam at left.

Beaver ponds are also effective in increasing wildlife such as insects, water voles, amphibia and fish. In one area the abundance of fish, including trout, was 37% higher in the beaver pond than nearby.

Beavers are good landscape engineers, but they are not very good neighbours for farmers. Their dams raise water levels which sometimes floods fields and they are also partial to some crops, including maize and orchard trees. There are straightforward ways to overcome these problems but, of course, they can cost money and the cost may be borne by the farmer or landowner unless a management group is in place, as is the case on the River Otter – run by Devon Wildlife Trust. 

Feeding remains. Sticks and small branches stripped of their bark.

On the other hand, beavers save money, by reducing flood risk and are beneficial in improving water quality and biodiversity. The key is to ensure that those of us who benefit from their presence bear the costs of the damage they do. The Government has said that it wishes to pay farmers for environmental benefits and, if it lives up to these ambitions, there is no reason why beavers should not be more widespread. 

It is several hundred years since there were beavers on the Creedy catchment itself, but younger readers of this article could see them back within their lifetime. The beavers that have colonised the river Otter will, in time, spread to the adjacent Culm catchment. The Culm flows into the Exe at Stoke Cannon, little more than two miles, as the beaver swims, from where the Creedy joins it at Cowley. I would love to see it happen!

Beavers on the River Otter Devon Wildlife Trust

You can read more about the beaver colony on the River Otter on the Devon Wildlife Trust website 

Aug 7, 2020

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