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Benefits to wildlife

Beavers influence their immediate environment to utilise resources, most notably by their action of dam building. They do this to raise the water levels. This affords them security in which to forage, cache food under water for the winter, and to increase protection around their place of shelter – the beaver lodge.

Beaver ponds become habitat and a haven for wildfowl and amphibians, mammals such as the water vole and otter, invertebrates and fish, and a host of plants and trees such as alder and willow.

Beavers often dig canals to reach new foraging areas. These canals are used as corridors for safety, as well as to transport feeding and branch materials back to the main dwelling and feeding areas. The canals and surrounding wetland habitats are ideal habitat for water voles – one of our most endangered mammal species.

Hole nesting species such as redstarts, pied and spotted flycatcher, tree creeper, tits and tawny owl benefit from nesting habitat created from waterlogged trees, which often rot and create nesting habitat which is usually in critically short supply.

Beaver wetlands are a haven for amphibians such as toads, frogs and newts. The creation of such habitat is of critical importance, as amphibian species are in steep decline, both nationally and worldwide.

Wildfowl in particular benefit from beaver ponds. Many duck species, together with rare species such as water rail and moorhen – two of our most rapidly declining water species, find feeding and nesting habitat in beaver wetlands.

The golden ringed dragonfly emerging from its nymphal skin is one of thousandsof invertebrate species which benefit from beaver wetlands in one way or another.

The puss moth and caterpillar is one of many species of moth which benefits from beaver impact upon riparian tree species. As species such as willow and aspen are selectively cut, the rigorous regeneration from the stumps attract many invertebrate species such as the puss moth. In the case of aspen – a favoured tree species of beaver, several of our most endangered invertebrate species benefit in one way or another from the different growth stages of post beaver felled aspen.

The endangered dark -bordered beauty moth requires aspen saplings about 2-3 feet high. As the trees grow, they become suitable for the rare poplar long horned beetle which requires trees of slender girth and thin bark. While old mature aspen which may be occasionally be felled or even drowned out by flooding are taken over by various hover fly and fly species – some so rare they have only recently been discovered by science. It is thought that these species were once an integral component of beaver habitats.

The vast array of wildlife species which thrive in the ecosystems created by beaver wetlands attract some of our most enigmatic mammal predators such as pine marten and otter. Indeed otters routinely take shelter and breed in old beaver burrows and benefit greatly from the increased fish and amphibian productivity associated with beaver ponds.

So efficient are beaver dams at retaining sediment, that beaver wetlands eventually silt over and become “beaver meadows”. Such meadows are virtual oasis of wildflower meadows. The rich mineral deposits associated with beaver meadows offer optimal foraging for deer and other species. Eventually the meadows are encroached by alder, willow and ash. This woodland type is arguably the most ecologically rich woodland type available. In particular, they offer critically rare habitat for hole nesting bird species, bats and invertebrates.

Impact on salmon

There has been a great deal of debate as to whether beavers will have a positive or negative impact on our salmon rivers in Scotland.  Some people involved with salmon fishing fear that the dams built by beavers will block the salmon’s access to spawning grounds.  It is claimed that, because modern agricultural practices in Scotland have canalised rivers, salmon have been forced upstream to the tributaries to find redds for breeding and that here they will come into conflict with beaver dams, once beavers are widespread throughout the river system.

Various expert opinions have been expressed about the problem that beaver dams will pose to migrating salmon – Ronald Campbell believes the beavers will cause a problem and informally, Professor John Thorpe, thought the contrary.

Research papers show that in American rivers the state of affairs is the other way round – it is the removal of beavers and their dams and coarse woody debris from the rivers that has been an important cause of loss of salmon, and their return greatly increases salmon numbers.  The size of salmon parr in beaver pools is much larger than elsewhere in the river.  In the South Umpquha river in Oregon, beaver have been returned to a river ruined by logging as part of a successful programme to get salmon back.

The counter argument to this research is that it applies to a different species of salmon, and a different species of beaver in a different topography.  There is very little research into beaver impacts in Europe as no problems have been reported in either France or Norway so no research has been carried out. However Duncan Halley, a beaver expert who is a former Scot now living in Norway reports that salmon parr are to be found above, below and between beaver dams in Norwegians rivers in topography very similar to that found in Scotland. SWBG is supportive of research into salmon and beavers now being carried out in Tayside.  

Parasite risk

Over 90% of the Tay beavers were born in Scotland and will be guaranteed free from this parasite.

The very small chance that one of the handful of imported beavers could carry this parasite has been carefully risk assessed by experts and a strategy for further risk reduction has been agreed. The parasite, which cycles between rodents and canids cannot be passed directly from beavers to humans. This risk occurred as a result of lack of knowledge in the past when beavers were brought legally into the UK and quarantined for use in zoos, wildlife parks etc. The Scottish Government scientists have already advised the Ministry that culling the beavers for this reason is not appropriate.

ECHINOCOCCUS MULTILOCULARIS

Very low risk of Tay beavers carrying the parasite