Beavers are known as ecosystem engineers- they alter their environment and manage the biodiversity and biomass found within it.
This can have many positive impacts: creation of fertile soils- perfect for a range of riverbank plants, fish stock recovery, reduced water flow- useful particularly during heavy rain and flood periods, and creation of new, complex underwater habitat between the river and the bank. Dams also help purify water and trap silt, reducing turbidity and sedimentation of water courses.
Concerns about reintroducing beavers range from disease introduction, such as beaver fluke and beaver beetle, reduction in agricultural land due to wetland creation and the impact to fish. The beaver beetle is a parasite to beavers alone, and with proper screening, disease introductions can be managed. Beaver dams only flood small amounts of land, and compared to the large scale flooding they can control, the economic impact is minimal. Fish migrations have been studied in Scotland to understand the barrier effect of dams. Initial studies suggest that dams do impede movement upstream in salmon and trout, but due to increased habitat diversity, the impact on abundance and productivity is positive. These are only preliminary results and the issue needs further research.
Beavers are native to the UK, but have been extinct here since the 16th century, when they were hunted for their pelts, meat and scent glands. Schemes are now starting to bring this native animal back. Beavers have been reintroduced into Scotland- the Scottish Beaver Trail started in 2009, introducing 4 beaver families into Knapdale Forest. These beavers have been thriving, with 2 new beaver kits spotted this year.
In Devon, the Wildlife Trusts have set up an enclosed 3 hectare area containing 2 beavers, with the aim of researching the effects that beavers have on wetlands and to help inform future reintroductions. The original small stream has been transformed into an amazing network of waterways.
Now there is another project in Devon. In 2014, beavers were found on the river Otter, their origin unknown, but suspected to be the result of an escape or unauthorised release. Initially, Defra planned to place them into captivity after fears of disease (E. multilocularis forms liver cysts, it cannot be transferred between beavers, but it can be transferred to other mammals). After the animals were found to be disease free, the Devon Wildlife Trust were granted permission to start the River Otter Beaver Trial. You can follow their story here.
There are now an estimated 12 individuals in 4 parts of the river. Recently there have been concerns that the beavers have disappeared, but the Wildlife Trusts have assured us that there is no need to worry. In fact, you can head down to the river to spot them for yourself.