Reintroducing beavers to the UK could help stop flooding

Reintroducing beavers to the UK could help stop flooding

Reintroducing beavers to Britain could help clean up rivers, prevent flooding and minimise soil loss, an expert has claimed.

Professor Richard Brazier, a researcher at the University of Exeter, has said unpublished preliminary results from a trial area in Devon showed muddy water entering an area where the creatures were living was three times cleaner when it left.

In England, several Bavarian beavers unofficially let loose on to the river Otter in east Devon are now part of an official trial licensed by Natural England, the government’s conservation watchdog. In 2020, the government will decide whether to allow them back for good.

The return of beavers to Britain half a millennium after we hunted them to extinction is both thrilling and controversial. The Eurasian beaver has been reintroduced into virtually every European country in recent decades. While Britain remains a member of the EU, it is obliged to reintroduce extinct species “where feasible”.

The experimental site in Devon is vivid proof of how beavers create a wildlife paradise, re-engineering small valleys with amphibian- and insect-friendly ponds. Exeter University scientists counted 10 clumps of frogspawn in 2011; this year there are 681. There were eight species of water beetle in 2011; 26 in 2015. Herons, grass snakes, kingfishers, willow tits, rare barbastelle bats have all returned. In Scotland, ecologists recently found that beavers increased the number of plant species by nearly 50% because they create such a rich variety of habitats, from saturated meadows to sunny glades where moisture- and light-loving plants prosper.

In Europe, beavers have stimulated ecotourism, but they may also benefit human communities in other ways. Devon’s small beaver ponds and soil saturated by damming hold nearly 1m litres of water. Scientific instruments measure water flows and quality above and below the site. The beaver dams improve water quality. Phosphates and excessive fertilisers washed into waterways can create toxic algal blooms, which can be fatal for anything from fish to swimming dogs.

Exeter University researchers have collated data in a graph showing flood events. During heavy rain, the volume of water flow increases rapidly above the site, creating a dramatic spike in the graph. But when the floodwater is measured again below the site, there is a gentle curve. In other words, the beavers dramatically reduce the peak flow of floodwater on this stream.

However, Mark Elliott, lead beaver project officer of Devon Wildlife Trust, does admit “beavers do create issues, there’s no two ways about it. They are not marauding across farms causing damage but they do engineer water and they could change the way we drain land.” His most crucial task is to work with local farmers. “Most have been brilliant. We’re not seeing any persecution [of beavers] on the river at all.”

In Scotland, however, farmers complain they have lost valuable farmland to flooding caused by beaver dams and have spent thousands clearing ditches blocked by the animals without recompense. They are negotiating with the Scottish government to cull if beavers threaten agricultural land.

Elliott says that, in Devon, “the farmers say to us: ‘We don’t mind the beaver, but if they return we need to be able to deal with problems quickly.’” This does not necessarily mean killing them.

In two instances so far on the river Otter, dams have flooded small areas of grazing pasture. Under the trial’s terms, Devon Wildlife Trust pays to solve the problem at no expense to the farmer.

In one case, it installed a “beaver deceiver”. This pipe goes through the dam, lowering the water level and stopping flooding. The pipe is concealed and covered with mesh, so busy beavers can’t block it. Important trees are protected with a sandy-textured anti-beaver paint – the animals hate chewing it. The trust hopes that such technologies will allow beavers back into human-dominated countryside, but also knows that farmers’ acceptance may depend upon government payments to reward them if agricultural land is given over to beaver-created flood defence.

For centuries in Britain, we have sought to remove water from land to farm it, and channel rainwater out to sea as quickly as possible. We have built houses on so many floodplains downstream that we need to slow the flow, and hold more water on land upriver to stop towns flooding. Beavers installed in every headwater – at the top of small streams – look like ideal, cost-effective flood engineers, providing landowners are compensated.

However, beavers are territorial and like deep water. Small streams require intensive beaver-labour to create dams and deep-enough water. Beavers won’t naturally inhabit these locations unless all the better territory downstream is occupied by other beavers.

“You’ve either got to hold them there with fencing or have beavers back in the landscape, so all territories are occupied and they are forced back into these sub-optimal habitats, where they must manipulate the landscape,” says Elliot.

In Cornwall, holding beavers in a pen upstream is exactly what one local farmer has started doing this year, in a bold attempt to protect the village of Ladock from flooding. There’s a proposal for a similar scheme in the Forest of Dean, Gloucestershire. But fenced-in beavers won’t be affordable in the long term.

Elliott believes there are plenty of suitable rivers – from the Severn to the Thames – but fears that they could cause more problems than benefits for intensively farmed lowlands such as the East Anglian Fens or the Somerset Levels.

The beaver can majorly influence ecosystems but it is a big animal and it will need space. It is a question of how willing we are to giving it space.

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