Britain’s largest rodent, the humble beaver, can help prevent flooding thanks to its habit of building dams across waterways. The semi-aquatic rodent has been reintroduced into the wild in the 21st century after over-hunting almost wiped it out.
Today, this amazing mammal is gradually reappearing in England, Wales and Scotland, thanks to dedicated conservationists, including the RSPB and other wildlife organisations, who have brought it back from the brink. There are around 400 beavers in the wild in the UK, after it became officially extinct in the 16th century.
Scientists have labelled beavers “climate saviours”, in the belief that their dams can potentially reduce flooding by as much as 60%.
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The eager beaver
Synonymous with getting on with tasks enthusiastically and vigorously, Britain’s largest rodent weighs up to 30kg and can measure more than a metre from head to tail.
Webbed feet enable beavers to swim, and strong teeth and a powerful jaw give them the ability to source the materials to build dams. You might be forgiven for thinking the large, protruding teeth implied a carnivorous diet, but the beaver doesn’t even eat fish! 100% herbivore; it eats leaves, tree bark, aquatic plants and grass.
Their trademark teeth are used to build their homes on waterways, with their large, broad, flat tails also playing an integral role in the construction process. The beaver builds dams on streams and rivers to restrict the water flow. This creates a deep pond of still water, where they construct their home, known as a lodge.
Building their home on the water keeps them safe from predators such as foxes, humans and dogs.
Beaver dams: the benefits
While creating their own ecosystem, beavers’ dams can also help reduce flooding.
While some landowners fear beaver dams may increase the chances of flooding, this hasn’t been the case. As they are slightly leaky, the area around the dam is likely to become a wetland area, which improves biodiversity – there is very rarely any flooding as a result.
Studies in Europe show the beaver dams reduce the risks of flooding by up to 60%. In the European studies, small pipes nicknamed “beaver deceivers” were placed through some of the dams in high-risk flood areas, allowing a small amount of water to pass through to further manage water levels. In the UK, the beavers’ dam-building activities are tracked by field staff at the Scottish Beaver Trial – an independent scientific study carried out by Scottish Natural Heritage.
When beavers chew the trees at the water’s edge to build dams, it also mimics a historic method of woodland management, called “coppicing”. The idea is that the stumps of the trees left in the ground will sprout new shoots and branches. Coppicing increases the trees’ capacity to grow back more densely at ground level, providing shelter for other animals and birds.
Beaver dams also improve the water quality by trapping sediment. This gives fish species such as trout and salmon a greater opportunity to forage.
How severe is the threat of flooding in the UK?
Floods have become more commonplace in Britain in recent years. In December 2020, more than 1,000 people were evacuated from their homes due to flooding in Northamptonshire, leaving some people homeless for Christmas.
In January 2021, Storm Cristoph also caused widespread flood damage, with the Environment Agency confirming 400 homes had been hit. People in central and northern England were worst affected, with river levels described as “exceptionally high”, especially around the River Dee in Cheshire. A total of 138 flood warnings were put in place and people were advised to stay away from swollen rivers and not to drive along flooded roads.
Will more beavers be introduced in the wild?
Prior to their reintroduction to the wild in the 21st century, the last mention of beavers in England was in 1526. They were over-hunted for meat, fur and for a secretion called castoreum that was used in perfume and medicine.
A new population of Eurasian beavers has been gradually re-established across their former range in Britain through a licensed programme supported by the RSPB. The wildlife charity describes the beaver as a “keystone species” due to its positive influence on the environment.
A population of beavers appeared around Devon’s River Otter in 2008, with their origins unknown. More beavers were released there in 2016. In 2011, beavers were also introduced in south Devon, near Dartmoor, as part of the scientific studies. They built dams that created 13 ponds on local waterways, reducing flooding by releasing precipitation over a period of days or weeks, rather than hours.
In Scotland, a beaver population now lives around the River Tay, while others live in Knapdale Forest, after being released by the Scottish Wildlife Trust and the Royal Zoological Society of Scotland. Under Scottish laws, the beaver can now expand its range naturally, rather than being reliant on the reintroduction programme.
Beavers were released on to a four-hectare site of farmland in North Essex in 2019, as part of a flood risk reduction project. The impact on flooding and wildlife is currently being monitored by the landowner.
While the beaver isn’t a protected species in England, the RSPB continues to support the River Otter Beaver Trial, where the licensed population of beavers is steadily increasing.
Flood damage
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