Beavers

Their dams protect against flooding, easing pressure downstream by slowing the flow of water upstream. For example, a single five-acre beaver enclosure in Cornwall decreased peak flows following high rainfall events by 50%, greatly reducing the flood risk in the village downstream.

Their dams help with drought by storing water upstream. This significantly reduces the impact of higher summer temperatures on surrounding habitats, by being a source of water for land managers and wildlife throughout periods of drought.

The dams hold back silt which captures carbon, while the new plant growth which is created by their efforts provides a fantastic carbon sink.

By filtering out sediment and pollutants such as fertilisers and pesticides used by farmers, the dams clean our water supply.

Beaver activity can boost plant diversity by as much as 33%. By gnawing down trees to create their dams, beavers coppice the woods around them, encouraging new growth among light-seeking plants. 

There is an increase in the abundance and diversity of all species. For example, the deep ponds beaver dams create by holding back water provide new habitats. Meanwhile, the wetlands they encourage are a haven for birdlife and the debris from their constant building work attracts a host of invertebrates, a vital part of the food chain.

A keynote species is a species which plays a unique and critical role in the way an ecosystem functions, or in the structure and health of a habitat. The presence of keystone species determines the types and numbers of other species found in that environment. Without keystone species, the habitat is dramatically different, usually far less healthy, and in many cases, ceases to exist. An analogy is the keystone in a brick arch. If you remove the keystone then the arch collapses. When beavers were removed from Britain, the habitats they supported collapsed.

Beavers do modify the habitats and landscapes they live in through coppicing, feeding and in some cases damming (beavers living on lakes or large rivers have little need of constructing dams). In the first instance, these changes can markedly alter the appearance of the local environment but all of these modifications have a positive effect on biodiversity. 

Beaver adaptations can bring enormous benefits to other species, including otters, water shrews, water voles, birds, invertebrates especially dragonflies, and breeding fish. In effect, beavers naturally create and maintain diverse habitats. Their dams can hold water in periods of drought, can regulate flooding and improve water quality by holding silt behind dams and catching acidic and agricultural run-off.

Beavers forage close to water with activity usually concentrated within 20m of the water’s edge. Beavers do fell broad-leafed trees and bushes in order to eat the bark during the winter and to construct their lodges. Most trees will be coppiced and will regenerate, which diversifies the surrounding habitat structure. Coppicing has been practiced by foresters throughout history as a method to manage bankside trees. The actions of beavers are very similar meaning the woodlands will be naturally maintained.

Beavers are a species that occasionally require the need for direct management intervention by man, if their activities result in undesirable localised flooding or tree felling. Any occasional localised problems are usually overcome by simple actions, such as overflow piping and electric fencing. Beavers rarely eat conifers, although the odd conifer might be gnawed by an immature animal that has not learned that conifers are unpalatable and that its resin gums up their teeth. They generally do not live in water entirely surrounded by conifers.

Impacts from burrowing, ie collapsed banks, are a factor and have been cited by some anglers.

Evidence from Europe shows that shows that beaver damage is, in the vast majority of cases, small-scale and localised. Beavers are not regarded as pests in Europe and where localised problems have occurred, there are a number of well-established methods in place. These include the removal of dams, the introduction of overflow piping, or the installation of fencing (as one does for deer and rabbits).

In general terms, beavers can actually help reduce the risk of flooding lower down in river systems by building dams and moderating water flow. The modifications made to the streams can raise the water table locally, creating wetland areas to the benefit of biodiversity. Evidence from elsewhere in Europe shows that instances of beaver dams creating undesirable flooding are uncommon, localised and usually small-scale. In these situations dams are simply removed or pipes (‘beaver deceivers’) are placed through them to manage water levels.

It is important to differentiate between the storage of water by beavers in river headwaters, and the impact of beavers on low lying land. In some places, culverts and drainage systems, some of which are critical to reducing flood risk, need to be kept clear of beaver debris

No. Beavers are completely vegetarian. Beavers eat woody plants and bark, aquatic plants, grasses and shrubs.

Beaver activities may have both positive and negative impacts on different fish species. Understanding the overall impact is complex. Beaver dams may act as barriers to migratory species such as salmon in some years and conditions, and cause localised siltation upstream of dams affecting spawning habitat. On the other hand, positive impacts may include an increase in habitat for fish rearing and overwintering, an increase in refuge areas during high and low flow periods and an increase in aquatic invertebrate prey species. Read more about the potential impact on fish by the Scottish Wildlife Trust.

Beavers have a definite preference for certain trees. Preferred tree species include alder, aspen, apple, birch, cherry, cottonwood, poplar and willow. Aspen/poplar and apple are their favourite. If the supply of their preferred trees is low, they will harvest oaks and some maples.

Conifers such as pines, hemlocks, etc. are their least favourite. Sometimes they will girdle (remove the bark around the entire base) of conifers for an unknown reason. One possibility is to obtain a much-needed dietary nutrient.

Research suggests that ponds and water pools created from beaver dams can have marked benefits on local water quality. Dams are usually only built on small streams, less than 3 metres wide, and these can moderate the detrimental effect of irregular flow. The modifications can also raise the water table locally creating wetland areas to the benefit of biodiversity.

The ponds can help to neutralise acidic run-off, act as sinks for pollutants and increase the self-purification of a watercourse. They can form considerable sediment traps, reducing very strongly erosive runoff and particulate loads in downstream water.

Beavers can carry host-specific parasites not currently present in Britain, though these are not known to infect or harm other species of wildlife,  livestock or humans. Other parasites carried by beaver are already present in British wildlife, livestock and humans and these other sources of infection pose a more significant risk to water contamination than beavers.

Beavers live in burrows dug into river and pond banks. They sometimes live in lodges built out of sticks and mud. They are mostly nocturnal (they are active at night). They can be seen emerging or returning to their lodges at dusk and dawn, times when they are actively feeding, grooming and patrolling their territories.

Beaver reintroduction in Great Britain is a devolved matter. As such, the status of beavers in Scotland, England and Wales is devolved to each respective government and reintroduction is at differing stages across these nations.

There currently is no known evidence of beavers ever having been present in Northern Ireland (or the Republic of Ireland). As such, no beaver introduction projects are due to take place there.

ENGLAND: The River Otter Beaver Trial was a licenced five year reintroduction trial that took place in Devon. In August 2020 the Government announced that Devon's beavers could stay.  This was 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. There are also a number of fenced projects across the country, including in Cornwall, Yorkshire and Essex amongst others. At present, a licence is required for a beaver project.  The Government have now set out plans to release beavers into the wild in England  in a consultation which launched on 25 August, which is due to report at the end of November 2021. 

SCOTLAND: As of May 2019, the Eurasian beaver is now protected in Scotland as a European Protected Species and the beavers currently present in Scotland will be allowed to expand their range naturally. The Scottish government have developed a Management Framework, details of which are available here.

WALES: The first officially-licensed beavers have been released in Wales by the Montgomeryshire Wildlife Trust as part of the Welsh Beaver Project. 

The origins of Avon’s wild beaver population are a mystery. Possibilities include escapees from other releases, which have occurred across the South West since the early 2000s. We started receiving sightings 2 years ago, and our subsequent monitoring told us there are 3 generations of beavers living on the riverbank. This suggests they have been happily co-existing alongside humans for some years.