European beavers were present in the UK until the 16th century. Two populations in Scotland have recently been established: one through a licensed release at Knapdale, and one through unauthorised reintroductions on the River Tay. The Scottish Government will decide later this year whether to allow these beavers to remain. The Welsh Beaver Project is currently assessing the feasibility of reintroductions in that country. In England, a report in 2009 concluded that the benefits to ecosystems were, on balance, likely to outweigh the potential negative effects. There are already at least four enclosed populations of beavers at various locations in England, and small numbers of wild beavers are present on the River Otter in South West England originating from an unlicensed release or escape.
The Mammal Society recognises that beavers are important components of river and wetland ecosystems and supports the reintroduction of this native species to the UK. In line with international guidelines on reintroductions published by the International Union for the Conservation of Nature (IUCN), populations of beavers should be monitored, and safeguards put in place to minimise the risk of negative impacts including disease transmission. It is important that strategies to manage potential conflicts between beavers and people are established, and that any new introductions follow the advice provided by the Statutory Nature Conservation Organisations.
European beavers, Castor fiber, are large, vegetarian, semi-aquatic rodents weighing 15 kg to 38 kg. They live in rivers, streams, ditches, lakes and wetlands. Territorial family groups of 3-5 occupy stretches of river or lake bank 1-13km long. They fell trees, burrow in the banks of rivers, and build lodges of piled logs and branches. In Europe, beavers do not usually dam waterways to the same extent as in North America where the habitat is significantly different. Nevertheless, they construct canals into the riparian zone and build dams across shallow streams and rivers with tree trunks, branches, mud and stones. These dams help to maintain water levels above the entrance of their burrows, providing protection from predators, and assist in the transport of the heavy branches and vegetation used for food in the winter.
Beavers were lost from the UK in the 16th century and over much of continental Europe by the early 1900s, probably due to over-hunting. Refuge populations remained in Scandinavia, France, Germany, Russia and the Baltic States. Since the start of the 20th century, populations have been re-established over much of Europe by natural movement, reintroduction and supplementary releases. Until recently, Britain has been one of very few countries in the original geographic range of the species in Europe which did not have beavers.
Under the EU’s Directive 92/43/EEC Conservation of Natural Habitats and Wild Flora and Fauna (the Habitats and Species Directive) Article 22, member states must consider reintroductions of extinct native species in Annex IV. Eurasian beaver is currently listed as an Annex IV species and an Annex III species of the Bern Convention.
A licence is required from DEFRA under Section 16 of the Wildlife & Countryside Act 1981 legally to release species into the wild that are not normally present in Britain.
The potential impacts of re-establishing beavers in the UK
Beavers are ecosystem engineers. They modify habitats by building dams and lodges and creating networks of ponds and wetlands which can influence water quality, water storage, flood risk and biodiversity (see Figure). The provision of ecosystem services by beavers, and the potential positive and negative impacts of re-establishing the species, have been assessed in detail (see Bibliography). The weight of evidence is that there will be an overall beneficial effect of beavers returning, largely because of their role in creating a matrix of wetland habitats that are favoured by a wide range of other species. Once well established in a river system (which may be 10-20 years after first introduction), they may also lower the rate at which water flows from river headwaters into lower parts of the catchment, reducing the extent of river level fluctuations and potentially therefore also reducing flood risks, as well as improving water quality. There may be local negative effects in some situations. For example, concerns have been raised about damage to flood defences and trees, and about the potential for dams to block the movement of migratory fish or affect spawning grounds. Nevertheless, there are likely to be other more immediate benefits connected with recreation (e.g. through the creation of habitats favourable for bird watching) and tourism. Beavers are a high-profile species; the animals are relatively easy to watch, the results of their building activities a source of great interest. They are therefore a highly attractive component of the fauna of any region.
Beavers and disease
Like all wild animals, beavers carry diseases. The Society supports the view that a detailed disease risk assessment should be made during the planning stage of reintroduction projects and all potential release animals should be given a thorough veterinary screening. Of particular concern are diseases and parasites that do not occur naturally in the UK. The tapeworm Echinococcus multilocularis (Em) is a case in point and potentially represents a serious threat to human health. The life cycle of this parasite involves a carnivore such as a fox (or a domestic dog) as the definitive host and usually a rodent, such as a vole or a beaver, as a secondary host. However, other animals and humans can also be infected by ingesting eggs of the parasite. At one time, it was thought that if beavers for introduction were sourced in Norway, they would be free of Em, but there is now evidence that the parasite has spread at least as far as Sweden, so this assumption is no longer safe. Some introductions or releases in the UK have involved beavers from Bavaria, which may carry the tapeworm. Although the risk is small, the very serious nature of the disease in humans, and the difficulty of controlling it if it were to infect other more widespread species, mean that great care must be taken to avoid its introduction either via the River Otter population in Devon, or elsewhere.
The Mammal Society welcomes the return of the beaver to the UK. There are likely to be significant benefits to biodiversity, as well as contributions to reduced flood risk and improved water quality in river systems. Beavers are also likely to prove an important ecotourism attraction. However, there are also potentially negative local effects. It is vital that appropriate management and mitigation strategies are in place and also that effective disease-screening measures are implemented. We do not support unlicensed releases, and emphasise that these pose a real risk to human and animal health, damage the interests of nature conservation, and may also compromise the welfare of the beavers themselves. Across Europe there is now a wealth of experience of developing modern and sustainable strategies that permit beavers to co-exist with humans. We urge all parties to draw on this experience to ensure the successful return of beavers to the UK.
Buckley, M., Souhlas, T., Niemi, E., Warren, E., & Reich, S. (2011) The economic value of beaver Ecosystem services: Escalante River Basin, Utah. ECONorthwest, 57 pp.
Gurnell, J., Gurnell, A., Demeritt, D., Lurz, P., Shirley, M., Rushton, S., et al. (2009) The feasibility and acceptability of reintroducing the European beaver to England. Report No. NECR002, Natural England, Peterborough, UK. Available from http://publications.naturalengland.org.uk/publication/45003.
Jones, A., Halley, D., Gow, D., Branscombe, J., & Aykroyd, T. (2011) Welsh Beaver Assessment Initiative Report: An investigation into the feasibility of reintroducing European Beaver (Castor fiber) to Wales. Wildlife Trusts Wales, UK., 99 pp.
Jones, S., & Campbell-Palmer, R. (2014) The Scottish Beaver Trial: The story of Britain’s first licensed release into the wild. Scottish Wildlife Trust and Royal Zoological Society of Scotland, 172 pp.
Kemp, P. S., Worthington, T. A., Langford, T. E. L., Tree, A. R. J., & Gaywood, M. J. (2012) Qualitative and quantitative effects of reintroduced beavers on stream fish. Fish and Fisheries, 13, 158-181.
Rosell, F., Bozser, O., Collen, P., & Parker, H. (2005) Ecological impact of beavers Castor fiber and Castor canadensis and their ability to modify ecosystems. Mammal Review, 35, 248-276.