Once a key part of wetland habitats, these ecosystem engineers were hunted to extinction. Now they’re returning to our forests to see if they can help restore our wetlands and reduce the impact of flooding.
Walking along the water’s edge, small tree stumps dot the area. The wood has been chiselled into a pencil-like point, as if sharpened with a knife. Webbed hind footprints in the mud are another sign that a forester did not fell these trees. They were felled by one of nature’s greatest engineers, the beaver.
The Eurasian beaver (Castor fiber) is a large semi-aquatic mammal and one of the largest rodents in the world. Their thick, waterproof fur and broad, leathery tail make them excellent swimmers. Known for tree felling and dam building, beavers have huge orange teeth hardened with iron that they used to ‘coppice’ waterside trees by gnawing on the stems.
These charismatic creatures were once widespread throughout Britain. However, beavers were heavily hunted for their fur and scent glands that produce a substance called castoreum. By the beginning of the 16th century the beaver became extinct from the country. Their absence has changed landscapes ever since.
Beavers play an important role in complex wetland ecosystems, creating habitats for many other plant, insect and mammal species. Few other animals have the ability to modify and shape their surrounding environment like the beaver does. Their damming creates complex pools and riffles, providing both deeper water and shallow, fast-flowing areas, important for a range of aquatic life. The coppicing they do opens up the canopy, creating areas of vegetation great for breeding birds. How they feed increases deadwood in the watercourse, which leads to an abundance of invertebrates. For these reasons, beavers are often referred to as ‘ecosystem engineers’ and known as a keystone species. Where beavers return, they can help to restore an entire ecosystem.
Their return can benefit people too. Beaver dams increase water storage and slow the flow of water downstream, potentially reducing the impact of flooding in the surrounding area. The dams are a real feat of engineering in themselves. The largest are 2-metre-high woven structures of branches and vegetation packed with mud to hold back the water.
With evidence of projects like the Scottish Beaver Trial at Knapdale Forest being a success, in 2018 a pair of Eurasian beavers were introduced in an enclosed trial at Greathough Brook in the Forest of Dean. To make this happen, we worked with beaver experts Dr Roisin Campbell-Palmer and Derek Gow, University of Exeter and Ecosulis, with funding by Gloucestershire Environmental Trust and Forest Holidays. The beavers were released into a specially designed enclosure within 6 hectares of woodland so that their impact can be carefully monitored. After a pause in the project, due to disease concerns, a new pair of beavers from Scotland were released last autumn and have settled in well.
Our team have been using trail cameras located around the site to monitor the beaver’s activity and see what they’ve been up to. Rebecca Wilson, Planning and Environment Manager for West England, explains:
Activity is usually picked up between the hours of 10pm and 3am when the beavers leave their burrows and start to work on maintaining the dams. Cutting willow and bramble with their chisel-like teeth, they carefully thread it into the dams to create deeper pools of water to conceal the underwater entrances to their burrows.
The benefits to wildlife in the area are already evident. Rebecca continues
Beaver coppicing has opened up small glades, increasing light levels, and created standing pools of water that are supporting frogspawn and tadpoles. There’s also more deadwood benefiting invertebrates, and a variety of birdlife has been captured on cameras feeding on insects around the dams.
In April 2019, two adult beavers were also released into an enclosure in Cropton Forest in Yorkshire as part of a five-year trial, with funding from North York Moors National Park, Forest Holidays and North Yorkshire Country Council. The main aim of this project is to see how they interact with the man-made woody dams in this area, working with researchers from universities of Leeds, Hull, Teesside and Exeter. The benefits have been witnessed already. Ecologist Cath Bashforth explains:
The changes to the environment have been amazing. There were two old ornamental fishponds on the site and these had become very shaded and silted-up, with the top pond holding very little water. The beavers set to work straight away. They have been plugging the leaks in the ponds and water levels in both have risen by over a metre. The beavers have also coppiced many of the trees overhanging the pond, opening it up to a lot more light.
The beavers’ work has resulted in a record amount of amphibians recorded at the site this year. Previously just six clumps of spawn had been recorded in the area. This year the total amount of spawn has been uncountable. Cath continues:
Because of the increased number of frogs and toads, over a dozen herons have now been regularly seen fishing around the pond, and otters and tawny owls have been caught on camera feasting on the amphibians. Teal and Mandarin ducks have been spotted on the site for the first time too, because of the increased water levels.
In addition to their work on the ponds, the beavers built a large, metre-high dam in the river. Like the Forest of Dean beavers, this has significantly raised water levels upstream enabling them to burrow into the banks and create an underwater entrance into the lodge they have constructed on the riverbank. Cath concludes:
They have now extended this dam across the floodplain by about five metres to hold back more water. The river here is now at least four times wider than it was before. As yet, the beavers have been swimming past the man-made structures and have been concentrating on their own! Though it is early days yet.
Both the Greathough Brook and Cropton Forest projects have huge support from our volunteers, who have been busy with wildlife surveys, monitoring the beavers and regularly checking the fences of the enclosures.
The beavers have also been busy growing their family. Both beaver projects are hoping for the patter of tiny webbed feet this year. The Cropton Forest pair had two kits in May last year, who have both grown well and have been helping the adults with their habitat amendments and learning the ropes of tree felling. Beavers give birth from spring to early summer and kits stay within the lodge for the first 1 or 2 months of their lives, so it’s not yet known if the beavers have successfully bred. Everyone is keeping their fingers crossed for positive news later in the year.
Now that beavers have already been formally reintroduced to Scotland, our Head of Environment and Forest Planning Andrew Stringer reflects on the future of the projects in England:
For now, we’ll continue to monitor both projects and measure the impacts of the enclosed beaver trials on the wider environment and local communities. We’re currently awaiting the decision by ministers on whether free-living beavers will be allowed in England. We're fully supportive of this, and hope to do a free-ranging release in the future.
One day, beavers may well be found across England’s forests once again.