The Eurasian beaver

The Eurasian beaver is the second largest rodent in the world and superbly adapted to an aquatic lifestyle, with webbed hind feet, transparent eyelids, and a flattened tail to steer when swimming. They are herbivores and mainly eat leaves, bark, and other vegetation such as ferns and brambles. 

However, what is amazing about beavers is not the biology of the animals themselves but their impact on the ecosystem around them. By engineering the environment around them to suit their own needs, they create a huge diversity of niches for other species.

Beaver kit on dam. Joshua Harris

The extent to which they do this really is incredible. When I first visited a beaver wetland in Devon I did not see any beavers, but wading through the swamp was still one of the most ecstatic wildlife experiences ever. I was then inspired to raise money for the Beaver Trust by running from Bath to Cambridge in 4 days, and have now ended up working for them. 

By felling trees, building dams and lodges, and digging canals they create a mosaic of wetland habitats with a huge amount of structural complexity creating many different niches for other wildlife. Ponds are great for frogs and fish, which in turn support otters and kingfishers. Bats roost in the standing dead wood and hunt through the gaps between the trees (the beavers’ thinning out of the tree cover may make it easier for bats to hunt). Water rails and moorhens sneak through the sedges and wet scrub. Owls hunt the small mammals thriving in the tangled understorey of dead wood, brambles, sedges, and regenerating trees.

In addition to these species which are known to live in beaver wetlands, there are others which we can speculate might have in the past, and could make a comeback if beaver wetlands became widespread. Abandoned beaver lodges may have been one of the original hibernation sites of hedgehogs, before gardens and wood piles were a thing. European tree frogs were found in Britain up until the 16th century and were probably associated with beaver wetlands (they prefer low scrub rather than tall trees, so the coppiced wet willow woodlands which beavers create may have been perfect). In Belgium, the comeback of beavers and the amphibian rich ponds they create has attracted black storks, formerly extinct for hundreds of years. 

As well as turbocharging biodiversity, beaver engineering can also provide many wider benefits to society. By holding back water in the headwater streams and interrupting its flow downstream, their dams can reduce the severity of flooding in the lowlands. At the other end of the spectrum, their dams can retain water in droughts where streams would otherwise dry up. In some parts of North America, beaver wetlands can even act as refugia for animals to survive wildfires, because they remain lush and unburnt as the landscape around them is incinerated. 

Beaver wetlands can also substantially reduce the level of agricultural pollution in streams because the slow flows cause sediment to drop out, and the huge growth of vegetation and aquatic algae removes nitrates and phosphates from the water. 

Many of these benefits can be substantially increased by setting aside un-farmed buffers along rivers and streams to give beavers the space and materials to work. These buffers can intercept some of the runoff from farmland and eliminate most of the problems that beavers can cause for farming (crop raiding by beavers seldom occurs when the crops are more than 20m from the water). Across the landscape, a network of river buffers would form interconnected corridors for other wildlife to move along. River systems are a ready made basis for a nature recovery network.

Ultimately, addressing the ecological crisis will require a dramatic shift in the way we use land to produce our food, however, beavers are a great option for nature recovery because they can create huge environmental benefits whilst having only a relatively small impact on food production (except in some very flat, artificially drained areas where it would not be appropriate to reintroduce them). Furthermore, many of the problems can be solved with simple management interventions such as protecting trees, removing dams, and translocating problematic individuals. 

The comeback of beavers to the UK’s rivers is in my opinion the most exciting thing which is happening in the UK at the moment. As well as having a hugely important ecological function, beavers are also just amazing creatures by themselves. It won’t be too long before an early morning walk along your local river could involve a thrilling glimpse of this long lost mammal.

Joshua Harris

By Joshua Harris

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