14-02-2016 - After a 400-year absence, the industrious rodents are back.

On a river near Okehampton their reintroduction has led to biodiversity and cleaner water
“Look at these teeth marks!” Professor Richard Brazier pauses, mud oozing over his Wellington boots, to admire the work of a pair of beavers who have been introduced into a patch of Devon woodland. “Just look at the size of them!” He runs his fingers along the incisions left in the exposed trunk of a recently toppled tree, before turning to survey the devastation around him.
The devastation is part of a scheme that backers hope will provide a template for a more balanced approach to flood prevention. The government is spending L3.2bn on flood management in the course of this parliament. As flood events such as those seen in Cumbria at the end of last year become more common, so attention has turned to flood management, with a call for resources to be allocated not to building flood defences to deal with the water when it arrives downstream but prevent it getting there at all.
The beavers resident on the three hectares of woodland near Okehampton in Devon could be part of the solution. In the five years since they moved there, they have toppled trees, gnawed bark, dug channels, constructed dams and made a rather impressive home for themselves.
“Prior to working with beavers we’d never really come across animals that would disrupt your work so much,” says Brazier, a hydrologist at the University of Exeter, as he surveys the tangle of branches and tree trunks.
But there is hope, too. New shoots are sprouting from the felled willows and a closer inspection reveals that beneath the devastation lies further evidence of new life promoted by the beavers’ work. “They are a keystone species who are obviously engineering the environment to their own benefit,” says Brazier. “But what’s interesting is all the other benefits.”
The Devon project targets three key indicators: water storage, flood attenuation and water quality. The beavers are, they believe, helping in all three. The 13 dams they have built along the 150 metres stretch of water have increased water storage capacity, evened out the flow of water and improved the quality of the water that emerges from the dams.
“This was a small stream that, before, would only have held a few hundred litres. Now it can hold 65,000,” he says.
Brazier proffers a graph showing that the dams have contained sudden rainfall, slowly releasing it along a “staircase” of dams: in this way they prevent the inundation that occurs when water is simply channelled downstream, while also providing a resource in times of drought.
“There are 20 hectares of intensively managed grassland feeding into the dams – bringing manure, slurry, non-organic fertiliser,” Brazier says, standing at the last of the network of dams. “You can see the quality of the water here at the bottom. Beaver activity has filtered out the impurities really effectively, like a good reed system might do.”
The level of sediment coming out of the dams is so low that the deposits of nitrogen and phosphate remaining in the water do not register on the university’s equipment.
Mark Elliott, who leads the beaver project for the Devon Wildlife Trust, pulls a large stone from the water. On the underside, a small community of grubs and larvae writhe and squirm: they are caddisflies and mayflies. “What’s happened here is transformational,” he says. “You have this incredibly complex mosaic of a transitional, dynamic habitat. There’s now a complex braided stream providing a habitat for orchids, watermint, bog pimpernel, herons, kingfishers, water beetles and damselflies. Five years ago when we started out, we didn’t know where we were going to get.”
The trust runs a beaver programme on the river Otter in Devon, and two programmes have run in Scotland, but it is the scheme near Okehampton that has provided the most controlled environment and the most reliable data.
“We obtained a five-year licence and trial to release beavers from [conservation bod] Natural England,” says Elliott. “We were interested to see what they would do with the encroaching scrub. It’s hard for farmers to manage. What we should see is landowners getting a payment for storing water on their land, to go alongside the stewardship schemes for wildlife. We’re trying to understand how beavers and people can co-exist by studying the impact on farming, wildlife, ecology and tourism.
“The biggest concern the landowners have expressed is not about the beavers, but about the people that come with the beavers – the interest we’ve had and the tourism boost on the river Otter have been extraordinary.”
But Paul Cottington, an environmental adviser for the National Famers Union in the south-west, sees the contribution beavers might make to flood management as marginal.
“If the question is about how we manage flooding, rewilding and the reintroduction of beavers is not a priority for us,” he says. “This is a very emotive topic: they look very good. But as soon as they become a self-sustaining population they become more protected than you and your child.
“Almost everywhere there are beavers – in Bavaria or North America, say – there have been issues, of crops being flooded, impact on roads and infrastructure. This tends not to occur initially, but 10 or 20 years on. The main point for us is not dismissing them, but they’re moving into a landscape that is modified and managed by humans, and they will need to be managed. The question is, how do we do that?”
Many of the concerns about the reintroduction of beavers could be rooted in the fact that they have been absent for 400 years. An indigenous species, they were hunted to extinction for their fur – used primarily to make hats – their meat and their castoreum, a secretion that was used in medicines.
Perhaps the most common misconception about beavers is that they will eat all the fish in the newly clean rivers, a charge repeated by Labour MP Mary Creagh during a select committee hearing into the government’s response to flooding. It was pointed out that beavers are actually herbivores.