The Eurasian beaver (Castor fiber) is a large, semi-aquatic rodent that once thrived in watercourses throughout Britain. Its extensive engineering activities had a dramatic impact on the landscape, and wetland and aquatic species would have evolved in the beaver's ecosystems.
It is unclear exactly when and how it disappeared from Britain, but a church ledger from Bolton Percy in North Yorkshire records a bounty being paid for a beaver head in 1780 – the last written record of its presence. The removal of this keystone species and the subsequent drainage and engineering of our waterways and wetlands transformed the countryside into a more productive landscape, but one where water and wildlife often now have to compete for space. The potential for beavers to restore more naturally functioning wetland ecosystems is the reason many people are so enthusiastic about their return. After discovery of a breeding family on the River Otter in East Devon in February 2015, Devon Wildlife Trust was given a licence to release beavers into the wild as part of a five-year trial reintroduction. At the end of the trial in 2020, the government will determine their future.
They seem to be thriving. Initially, there were around nine beavers in two family groups, but the most recent survey in March suggested there are now at least seven breeding families. There are also up to 13 territories, some of which could be occupied by single animals or young pairs.
When beavers are recolonising a sparsely populated catchment such as the River Otter, they will travel great distances in search of other beavers and resources. In one instance a tagged one-year-old swam roughly 50km upstream and settled in a lake, successfully attracting a mate and giving birth to a kit in 2018.
Every winter, the trust surveys the watercourses in the catchment area covering much of the main river and tributaries. During this season, surveyors can easily see signs of activity such as trees and branches that beavers have fed on, feeding stations, dams, lodges, footprints and scent mounds. All beaver field signs are spatially recorded and a heat map is produced from these
The survey suggests that the river's beavers are occupying deeper areas of water first and have now colonised much of the lower part of the small catchment. In these areas, they do not need to build dams to impound water because there are deeper stretches that allow them to construct the underwater burrow entrances they prefer.
As these optimal territories become occupied, beavers start to disperse into less-ideal habitats in smaller streams and ditches, and it is here that they tend to build dams to create the deeper water they need. Beavers feel safe in deep water where they can easily move around and escape predators. Their dams can create ponds and wetlands, and potentially have a huge role in reducing peak flows and associated flooding and low flows downstream – but potentially also bring them into conflict with existing land uses. After all, that water must be stored somewhere.
The University of Exeter has published data from a separate enclosed beaver site in West Devon that clearly shows how a sequence of 13 beaver dams built along 183m of small headwater stream has reduced peak flows after heavy rainfall. Flows are measured upstream and downstream, and after a flood has passed through the sequence of dams and pools the lag time is increased and peak flows reduced.
An expert steering group and working group have finalised and adopted the Beaver Management Strategy Framework for the River Otter – which contains recommendations from the trial on future management of the animal – that will apply after 2020. But as well as awaiting a timely decision from the government about the future of the beavers and clarity about their legal status, this framework will also need funding for a beaver management group for the catchment that includes support for landowners.
Central government funding is imperative for land and property owners to allow more space for rivers and associated wetlands to develop, and to manage any conflicts with existing land use, through a bespoke environmental land management scheme for instance. Strategic support for rural businesses and land-based enterprises is also vital, allowing new business opportunities, such as local tourism, to respond to the beavers' presence.
These animals have been absent from our waterways for so long that people have forgotten much about their ecology and behaviour, and many myths and misunderstandings have developed. As has been successfully shown on the River Otter, the first step with beaver management is to have readily available pragmatic advice and support for people living and working in the areas that beavers are colonising, because this can resolve many potential conflicts. However, a suite of mitigation measures should also be available to manage any negative impacts.
Beavers are very territorial, and if their effects can be managed without removing them, then they will keep other, potentially more disruptive, beavers out; trapping and removal is another option. In the longer term, when translocation sites that have sufficient food sources and shelter for beavers to live and where they can be released safely are no longer available, lethal control may be necessary in the highest risk circumstances.
As we approach a final government decision next year, the evidence gathered throughout the trial will be presented and disseminated. In May this year, the Scottish government formally recognised beavers as a resident species once again and gave them legal protection. Whatever we decide in England, it will significantly influence the way we manage water in the landscape in future.
Mark Elliott is Devon beaver project lead at Devon Wildlife Trust firstname.lastname@example.org
Related competencies include: Environmental management Management of the natural environment and landscape
Beaver dams have been built in the floodplain ditches in the lower River Otter valley