Beware of beaver fever

The verdict is in: hooray for beavers! The rodents that once roamed the wetlands of Britain, hunted to extinction in the 16th century, have been gradually returning to our rivers for some years now.

The first, discovered on the River Tay in 2006, had either escaped from enclosures or, more probably, were deliberately (and illegally) released into the wild. In England the first were found on the River Otter in Devon in 2013. Following a five-year report by the Devon Wildlife Trust, the environment minister Rebecca Pow this month gave them the right to live, roam and reproduce. The report’s conclusion was overwhelmingly positive. Beavers attract tourists and promote ecological diversity. Their dams might even help fight climate change and flooding.

In February, some of us concerned with the future of England’s chalk streams met in a Dorset village hall near Tolpuddle to offer a contrary view. The ecological great and good — Natural England, the National Trust, the Dorset Wildlife Trust — sent representatives to deliver their verdict in the name of consultation.

Chalk streams are often called ‘England’s rainforests’. They are unique, delicate ecosystems, home to many rare, vulnerable species, including water vole and damselfly. They are the corridor of life for the Atlantic salmon, the European eel, the brown trout. They are scarce and are almost exclusively English: of the 225 that exist globally, 215 are in England.

Since their flow is gentle, impoundments — whether the result of man or nature — can cause serious problems. Like a blocked gutter, dams bung up the system, trapping detritus that festers. We know this to be true because for the past two decades the Environment Agency (EA), the government body charged with protecting the health of our rivers, has been telling us so. In response to a Europe-wide initiative, the EA has arranged hundreds of consultations and spent millions of pounds to remove the weirs, dams and numerous other obstructions from our chalk streams that impede the free flow of water and migrating fish.

Beavers, of course, are all about dams. Natural England (the government’s adviser for the natural environment) has deemed these impoundments to be good, in contradiction to the EA. In the right place, they are. They can create a healthy wetland. But they will do great damage in the chalk-stream valleys. The river below will become starved of water; at best a dirty ditch. Soon the fish, water voles, amphibians and insects will flee or die. Beaver dams are nigh on impenetrable for fish. Trout or salmon moving upstream need a run-up to leap a dam. In fact, there is a formula to guide their efforts: the ‘plunge pool’ needs to be 1.25 times deeper than the dam in front of it. Since a beaver dam is at least four feet tall, a trout may be able to clear one on the Otter, but there is little hope of that happening on chalk streams, which are typically shallow.

But pointing out these negatives does not seem to have much effect on the National Trust, Britain’s biggest landowner, which is set on wild releases in the Purbeck Hills. This will place beavers within a day’s walk of Dorset’s chalk streams. All the argument is focused on rewilding and reintroduction, as if the landscape the beavers once occupied still exists. It doesn’t. In the 500-year absence of beavers, the wetlands of chalk valleys have been transformed into water meadows, a balanced ecosystem that beavers would upend as the streams are transformed from Tennyson’s ‘brimming river’ to a series of static water ponds prone to silt-ation and deoxygenation with the loss of spawning habitat. As for a reduction of flood risks, a favourite argument of the pro-beaver lobby, this has little relevance to a chalk stream where the rise and fall between winter highs and summer lows is measured in inches rather than feet and the excess, such as it, is spills out on to the water meadows.

Like the National Trust, the Dorset Wildlife Trust are beaver-smitten. At our meeting, there was an extraordinary exchange between a Trust representative and a landowner who asked, given that the Trust river flowed into his, why he hadn’t been consulted about a release of beavers into a three-hectare enclosure? The reply was tart: we are a private company, so we don’t have to.

The deck is stacked against the status quo because beavers have captured the zeitgeist. Those of us who have concerns have been treated with the kind of hostility usually reserved for climate change deniers. The government’s decision about the River Otter proves the point — it was based on an impact study of the local environment. The report does not ask what may happen if the beavers roam to the nearest chalk stream valley just 35 miles to the east, or examine the wider effects for fish, wildlife and landscapes very different to those in Devon.

And if beavers do cause problems for chalk valleys, any hope we can get rid of them is fanciful. If you thought the badger cull was controversial, try going after beavers.

My view is that Natural England should adopt a precautionary approach and impose a moratorium on future licences for both wild and enclosed releases until 2030. In that time the beavers on rivers such as the Otter can take their chances. If they thrive without causing permanent damage, the fears of us beaver-sceptics will have proved unfounded. The country has done pretty well without beavers for 500 years; I don’t think waiting another ten will make much difference.