My only experience of beavers at that time were the animals I had seen on wildlife documentaries, building huge dams across large rivers in the wildest parts of America. It seemed like such an outlandish idea to think of a species like this living in Surrey. Surely beavers can’t live in Surrey!
The common mistake I had made however was that my idea of a beaver was actually an American beaver, Castor canadensis. The Environment Agency officer, on the other hand, had been referring to the Eurasian beaver, Castor fiber, which was once widespread across the British Isles and Europe.
Beavers in the UK
Beavers were hunted to extinction in England and Wales as far back as the 12th century but hung on in Scotland until the 16th century, before finally disappearing from the British Isles altogether. They didn’t fare much better in Europe, where hunting beavers for their fur, meat and glandular oil (castoreum) drove the population down as low as 1200 animals.
Since then, beavers have made a remarkable comeback thanks to bans on hunting and more than 200 formal beaver reintroduction projects (plus numerous unofficial releases) in more than 26 European countries. European population estimates now stand at over 1.2million animals and the International Union for the Conservation of Nature (IUCN) now classes the species as ‘of least concern’.
After being absent from the UK countryside for over 400 years, beavers were spotted in 2001 living wild on the River Tay in Perthshire, Scotland, likely as a result of an escape or an unlicensed release.
A licensed trial reintroduction followed in 2009 when four families of beavers were released at Knapdale in Argyll, Scotland with the aim of closely monitoring their effects on the environment. The trial was a success and in November 2016 the Scottish Government announced that beavers are to remain in Scotland as a protected species.
A similar story played out a little closer to home, when in 2008 a small population of wild beavers was found to be living on the River Otter in Devon (as a result of an unlicensed or accidental release). When in 2014 it became clear that the beavers were breeding, the UK government planned to remove the animals, however the Devon Wildlife Trust instead proposed to carry out a five-year trial to monitor the beaver’s effects on the landscape. This trial project, named the River Otter Beaver Trial (ROBT) ended on the 31 August 2021 and was hailed a success by the UK government. The beavers will now be allowed to remain on the River Otter permanently and free to continue to expand their range naturally, finding new areas to settle as they need.
In a huge milestone, beavers have recently been granted native species status in the UK and the government are seeking the public's views on their proposed approach to further reintroductions in England and the management of the species in the wild.
The consultation will run for 12 weeks and will close on 17 November and relates to beavers in England only.
Eurasian beaver families consist of, on average, about four individuals, of which only the adult pair breeds. The species needs deep stable water (around 70 cm) to feel secure, particularly around their lodges and burrows, so where deep water does not exist, they can create it by constructing dams and digging canals. Beaver dams are made of sticks and earth, and gradually extended over time however they are much smaller than those built by their cousins, the American beaver. Beavers dig canals to explore different parts of their territory and forage in relative safety. Canals often start as regular tracks through wet ground, these are then gradually widened and dredged by the beavers.
As well as feeding extensively on soft riverside and aquatic plants, beavers browse on woody vegetation throughout the year, particularly during the winter months. They do not feed on fish which is a common misconception.
Benefits for Wildlife
Beavers are known as a keystone species, that is a species which has a disproportionally large effect on the ecosystem in which it lives. Their habit of building dams, felling trees and digging canals creates a mosaic of habitats across their range which supports a whole host of other species.
Beaver dams hold water behind them, creating pond like areas which push water sideways, helping to create a complex network of wetland habitats across the floodplain.
England and Wales lost three quarters of its ponds over the last 150 years however between 2011 and 2016 the DEBP site saw ponded areas increase 20 fold from 90m2 to 1800m2. In response to this, annual counts of frogspawn clumps have shown the number of clumps counted has increased from 10 in 2011 to 580 by 2016.
The foraging behaviour of beavers on woody riparian vegetation alters the structure of vegetation in beaver-occupied river reaches. This alteration is reported to improve habitat for a range of species such as birds, bats, and other terrestrial species due to the increases in canopy variability and increased dead wood abundance. Increased light penetration in areas of dense riparian woodland also enables the regeneration of understory vegetation. Beavers also provide numerous other habitats (e.g. canals and accumulation sites for woody debris), all of which will contribute to increased invertebrate biodiversity. Aquatic invertebrates responded very quickly to the increase in wetland habitats created in the first year of the DEBP. Between 2011 and 2012, the number of aquatic invertebrate species increased from 14 to 41
Within the channel beavers create a mosaic of habitats, with woody material providing cover for juvenile fish whilst coppicing of riparian trees opens up the river to light which benefits aquatic invertebrates through increased plant growth. Gravel habitats created by the beaver dams provide suitable spawning ground for some fish species and suitable habitat for riverflies such as mayflies.
Much of the river restoration carried out by the Surrey Wildlife Trust Wetlands Team focusses on restoring natural river processes to boost wetland biodiversity. Interestingly, without even meaning to, beavers do exactly the same. For example, beaver dams impound water, helping sediments and gravels to be deposited in the pools. When dams breach during high flows, fine sediments are flushed downstream and larger sediments such as gravels are redistributed, creating new riffles and gravel beds. This also results in an increase in bed level height in these reaches and a wider, more meandering and multi-threaded channel. With the creation of new dams elsewhere, the process is repeated. This results in the restoration of dynamic morphological processes and an increase in habitat variability within the reach, including deep pools, mobile gravels, extensive in-channel woody material, eroding banks and other natural features. The beavers have the added advantage of not having to spend days filling out permit applications to carry out their work 😉.
As climate change begins to bite, we are noticing storm events increasing in intensity along with prolonged dry spells. This famine and feast cycle is not only putting our homes and water resources at risk but also the biodiversity of our wetland habitats.
A large part of the problem is down to our intensively-managed landscapes, where the emphasis on water resource management is to move the water from the land to the watercourse as fast as possible. This leads to extreme flood peaks in our downstream settlements during wet weather followed by low flows during prolonged dry weather. Beavers however could provide part of the solution.
Beaver dams act as mini reservoirs helping to store water up in the headwaters of river catchments. The flow of water down the catchment is also slowed down as it is backed up behind the dams and encouraged out on to the floodplain. Research carried out by the University of Exeter found that during storm flows in the DEBP site, average peak flows were 30% lower leaving the site than entering. It was also estimated that the beaver ponds were storing 1 million litres of water at any one time.
This profound impact persists even during the wettest times of the year as the leaky dams constantly drain, freeing-up storage capacity in each pond. For example, during storm Frank in December 2015, 29 mm of rain fell on the DEBP site; peak flow leaving the site was 3 times lower than into the site and the water took 30 min to travel through the site (a distance of 183 m). Holding water back like this in minor water courses is a key principle in flood alleviation and something that beaver dams and increased channel complexity are likely to contribute to.
Between rainfall events, the leaky dams release water slowly, which provide a constant supply of water downstream. A month long drought in the summer of 2016, left the incoming channel, coming into the DEBP site, completely dry, whilst baseflow leaving the site continued. Low flows cause serious environmental problems as oxygen levels are depleted and any pollutants are concentrated
As well as water regulation, beaver dams also help to improve water quality. Diffuse pollution from agriculture is one of the biggest problems our rivers face. Sediment washing off fields smothers instream habitats while nutrients such as nitrates and phosphates reduce biodiversity. Research has shown that beaver dams help to filter out sediment and pollution that has washed into the river from the surrounding landscape. During 11 storm events monitored in the DEBP site, 1.6 tonnes of sediment was lost from 20 ha of grassland upstream of the beaver site but only 0.4 t of sediment left the bottom of the site during these same 11 storms. The beaver activity therefore led to a fourfold decrease in sediment yields downstream. During storm events, each litre of surface water leaving the beaver-modified site had 5x less phosphate than the water entering the site from agricultural land upstream. By the time the water has flowed through the sequence of beaver dams, a high proportion of these diffuse pollutants have been removed from the water, settling out in the ponds
Despite the multiple benefits created by the presence of beavers within a river catchment, there will also be impacts on the surrounding landscape that will need to be managed to ensure landowners are not left out of pocket. The majority of landowners within the ROBT area, where beavers had free range, were supportive of the project and a management plan was set up to deal with any issues.
When beavers build a dam, the water is backed up. In some cases this can lead to small scale flooding of fields, especially if the beavers decide to build a dam in a drainage ditch. ROBT project officers worked closely with landowners so that any problem dams were either reduced in size, or removed completely. This helped to ensure that farming operations were not affected.
Impacts on infrastructure also needs to be taken into account to ensure roads, tracks, footpaths, flood infrastructure and monitoring stations are not affected. Early on in the trial the ROBT worked together with the Environment Agency to identify sites in the River Otter that had the potential to be negatively impacted by beaver activity (EA) and outlined a mechanism for monitoring key EA assets for signs of beaver impacts. No impacts on EA infrastructure were observed during the trial, however some beaver dams caused minor flooding on tracks, so had to be reduced in size or removed.
Beavers feeding habits can also cause conflict with local landowners and farmers. This can include foraging on crops or damaging trees. Beavers were observed feeding on Maize during the ROBT however the impact was minor with an estimated cost to the farmer of £1.33. Feeding on trees can be more of an issue, especially when a tree has a monetary or sentimental value. A small apple tree was felled in a private garden during the trial however this was replaced by the project team and tree guards put around the remaining trees.
Beavers in Surrey
Since 2017, Natural England has issued 13 licenses across the country for enclosed beaver releases. One of the Successful applicants was the National Trust in Haslemere who plan to release beavers onto one of their estates in the South downs. Straddling the Surrey/West Sussex border, the beavers will be released into an enclosure on a headwater of the River Wey.
The National Trust said ‘Through this pioneering trial it is hoped that beavers can once more become an important and integral part of the ecological process at Valewood, contributing to the health and richness of the wildlife here and also giving future generations the chance to get to know these special residents. This work is part of the Trust’s strategy to restore a healthier natural environment and improve 25% of our land for wildlife by 2025.
The project will be working closely with expert beaver ecologists along with volunteers to monitor the effects the beavers have on the local environment.
Elsewhere beavers are settling in to the British Isles very well. It is now estimated that the River Tay in Scotland has a population of 400 beavers over an area of 5000km2.
As our country looks ahead to a green future, one which is able to withstand the impacts of climate change, working with natural processes to build resilience across our landscapes will become more and more important. Beaver reintroductions are seen by many as the epitome of such an approach due to the multiple benefits they deliver.
Taking this approach will require strong collaboration between landowners, government agencies, organisations and of course, local communities. Through partnership working and consultation, and with the right governance in place, in future we could see restoration of our wetland habitats on a scale never seen before, benefitting both people and wildlife.
Elliott, M., Blythe, C., Brazier, R.E., Burgess, P., King, S., Puttock, A., Turner,C., (2017) Beavers – Nature’s Water Engineers. Devon Wildlife Trust
- Brazier, R.E., Elliott, M., Andison, E., Auster, R.E., Bridgewater, S., Burgess, P., Chant, J., Graham, H., Knott, E., Puttock, A.K., Sansum, P., Vowles, A., (2020) River Otter Beaver Trial: Science and Evidence