CONCERNS ABOUT BEAVER RE-INTRODUCTION
have been raised about the problems of beaver reintroduction.
there are two common misconceptions:
1. Beavers do not eat fish (ever) – they are completely herbivorous, feeding on plants and forbs, and sometimes tree bark and twigs.
The Scottish animals would be European beavers not North American beavers,
which have an image problem caused by its flooding of large areas.
Concerns have been expressed that as a herbivore and a dam builder, the beaver may have an adverse impact on forestry in this country. However beavers feed overwhelmingly on plants and forbs close to water as well as broadleaved species and as such avoid riparian areas planted exclusively with conifers. In mixed woodlands, conifers may be susceptible to flood damage but in Norway a review of the situation found that the problem of inundated conifers was much exaggerated, and that damage to forestry was so minimal that it was not worth insuring against it. In much of Scotland, the terrain would also mitigate against large areas of flooding (which is more common in exceptionally flat areas).
Scotland's native broadleaves will be preferred by beavers as both food and building material. In addition, given that they are the prime constituent of riparian woodland, native broadleaves are more likely to suffer the effects of inundation caused by beaver dams. However many riparian species such as willow, alder and birch have co-existed with beavers for millions of years. These trees are well equipped to deal with an increase in the water table. But in some cases where conditions become too wet, some trees will die and will provide excellent habitat for invertebrates and fungi as well as good feeding and nesting sites for birds and bats. In good quality habitat, it has been shown that beavers, by selective feeding and coppicing, create a diversity of species and age structure and so do not destroy riparian woodlands but instead maintain them. However in areas where less productive but preferred food species such as aspen are eaten, beavers do have the capacity to deplete food resources.
Scotland, the aspen is an uncommon tree which supports a rich invertebrate
fauna, including a unique association found only in Highland areas,
and there are concerns that these valuable aspen stands are at risk
of eradication by beavers. However, much of the Scottish aspen resource
is located far from beaver-suitable watercourses and is inaccessible
to beavers, while some of those special aspen stands within easy reach
of beavers could be protected by fencing or sheathing the lower 1.5
meters of each trunk with heavy gauge wire mesh, until such a time that
riparian woodland management schemes substantially increase the range
and numbers of aspen. In some ways, we could say that the debate about
beavers has done more to raise the profile of aspens than any previous
from Europe shows beavers can flood or feed on crops, but this is more
an issue of areas of lowland Europe beside big rivers. Beavers sometimes
feed on maize and root crops such as sugar beet. This is an issue when
crops are grown very close to riversides. The effects of both flooding
and feeding can be countered by not planting susceptible crops near
the watercourse as part of the new approach to
safeguarding rivers and freshwater. Buffer zones of even 10 meters of
good riparian habitat can remove risks to agriculture. Beavers can dam
culverts in low-lying fields, and there should always be the opportunity
to remove such structures. Simple electric fencing is also effective.
We have already shown that the presence of beavers on a watercourse can have several knock-on benefits for fish. But fisheries managers and anglers are concerned that beavers will adversely affect salmonids by causing sediment build up at spawning grounds and by impeding migration by dam building, a phenomenon they feel has been little studied in Europe. However most spawning grounds exist in fast-flowing upland streams unsuitable for beavers so that interference with spawning gravels is very unlikely to happen. Beavers dislike fast-flowing rivers and burns (in fact, according to Latvian research, stream velocities above 1metre/second are unsuitable beaver habitat and are avoided). It is worth considering that beavers and salmonids co-existed in the same rivers for millions of years before we exterminated the beaver, and it is extremely unlikely that beaver dams in slow-moving water would seriously impede fish that are capable of negotiating cascading waterfalls. Beavers in Norway have increased from around 100 in 1900 to over 50000 today where they co-exist at capacity numbers with salmon and yet have had no detrimental effect on salmon populations. In fact, high beaver populations are considered mildly beneficial to salmon stocks in Norway. Sweden's leading beaver expert who is himself a salmon fisherman stated that the reason for the lack of studies on this matter is quite simply because there is not a problem to study.
In the rare instances when dams do cause problems, there are effective remedies. One of these, dam removal, which can be achieved with picks and shovels or with a mechanical digger, should take place as soon as the dam is built. Beavers tend to just rebuild long established dams that are removed or in some cases abandon an area altogether. If a dam holds back a large volume of water, then the destruction of the dam could have a dramatic effect on the water table upstream of it. Sudden drying out of the area around a beaver pond could have detrimental economic effects by damaging vegetation. An alternative to dam removal is to insert a 3-metre long plastic pipe into the base of the dam. So long as both ends of the pipe are submerged, then the beavers won't attempt to block the gap.
This method can be used to completely drain a beaver pond or just to regulate the water level.
(See also the discussion of this point on the 'solutions' page of the Beavers: Wetlands and Wildlife website)
Like any animal, beavers sometimes carry diseases. The only diseases that beavers might transmit to other members of the Scottish fauna are rabies and tularaemia. However, neither of these diseases is new to Britain and are preventable by quarantine and inoculation. North American beavers are more susceptible to tularaemia and there is no evidence of an epidemic affecting a population of European beavers. In addition, beavers suffer from pseudotuberculosis and pneumonia as well as gut nematode and gut fluke. However, careful health checks and anti-worming medication can be applied to beavers before release in Scotland. One disease that has been mentioned as a possible health risk to humans is giardia. This illness can be spread by beavers defaecating in watercourses used for drinking water. Giardia cysts however, are removed from drinking water during the filtration process of water treatment thus reducing greatly the risk of infection. That said, the evidence linking beavers and giardia applies to the North American beaver and so far, no link has been established with the European beaver. In any case, giardia already exists in Scotland with 3-400 people affected annually.
There are concerns that, in the absence of natural predators, a reintroduced beaver population would spread quickly and spiral out of control. While it is true that beaver populations can, after a number of years, increase quickly, over-exploitation of food resources by high populations leads to a local decrease in population. In circumstances where over-exploitation of the habitat is undesirable, beaver populations may be controlled by relocation or hunting. Individual beaver families whose appearance in an area is potentially damaging, can be easily live trapped with the use of spotlights and landing nets and relocated to areas where establishment is desired. In Norway, beavers are protected in areas with low or newly-colonising populations but a hunting season with a variable quota is permitted elsewhere. In Sweden, outwith those provinces where beavers are protected, an unrestricted hunting season runs from October to May each year. 10% of the Norwegian and 6% of the Swedish population are harvested. The meat from hunted beavers is a delicacy and the fur is often used to make hats and waistcoats.
We feel that many of the perceived problems associated with a reintroduced population of beavers are non-existent or are easily surmounted.