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Beaver Trial successful say scientific reports

Six reports looking at the trial reintroduction of beavers at Knapdale in Argyll have been published showing generally positive effects of the trial including increased visitors to the area and manageable effects on other plants and wildlife. The reports will be used to prepare evidence to help the Scottish Government decide whether to permanently introduce beavers to Scotland.

Beaver (Photo: Paul Stevenson)

Beaver (Photo: Paul Stevenson)


The reports consider the health of the beavers and their effect on aquatic plants, woodland, scheduled monuments and public health as well as the socio-economic costs and benefits of the trial. They set out the findings over the five years the Scottish Beaver Trial has been running, since the beavers were released in May 2009 by the Scottish Wildlife Trust and the Royal Zoological Society of Scotland, on land managed by Forestry Commission Scotland. During that time Scottish Natural Heritage (SNH) and its partners have been closely monitoring the beavers and their effects on the environment. The results will help the Scottish Government decide on the future of beavers in Scotland.

Work by the University of Stirling has shown that beavers have had an effect on aquatic plants in some of the lochs, showing a taste for white water lily and water horsetail, with a particular preference for common club rush and great fen-sedge. The most obvious impact was on great fen-sedge, an uncommon, though not rare plant in Great Britain, which declined substantially at three of the lochs used by the beavers. However it survived in other lochs in the area, also used by beavers. The water level in one loch rose significantly, because of a beaver dam, causing a major change in the quantity and distribution of plants. Although some of the original plants in this loch were lost, other plants grew on floating peat. The wetland habitat increased and was rapidly colonised by a range of plants and insects.

Turning to the woodland study, run by the James Hutton Institute, the beavers had gnawed or felled 8.6% of trees in the area as a whole by early 2014. Most of this activity was within 10m of the water’s edge. They favoured trees that were 2–6 cm across. Their particular favourites were willow, rowan and hazel but birch was most often used by beavers as it was the most commonly found tree in the survey area. Conifers were fairly plentiful but little used. Many trees felled by beavers regrow from their stumps but an initial flush of re-sprouting earlier in the trial tailed off more recently, as deer have eaten some of the new growth. The overall effect of the beavers on the woodland since they arrived at Knapdale is to significantly change the structure of some areas close to the edge of the lochs where they are living. In these areas the woodland has opened up and at ground level grass cover and woody debris has increased while leaf litter has reduced. Many other areas of woodland along the shore and away from the water haven’t been affected by the beavers at all.

The socio-economic impact of the trial has been assessed by Scotland’s Rural College. Visitor numbers and volunteering in the area have had a boost. The benefits extended beyond the trial area, and included a range of activities held throughout Scotland, such as education sessions, events, talks and walks. Over 5,000 students from 135 schools took part in field trips and events related to the trial. Costs include setting up and running the trial, as well as the loss of approximately 1.6 ha of land for woodland management and a 400m section of forest track as a result of flooding caused by a beaver dam. The report acknowledges that a formal cost-benefit comparison for the trial is not straightforward as many of the categories are difficult to put a financial value on. It also notes that as the trial site is quite remote, both positive and negative socio-economic impacts are more limited than they might be in the event of a wider reintroduction.

The other three reports were published by independent monitoring partners.

Argyll and Bute Council, responsible for monitoring public health, found that the additional risk to human health from the beavers at Knapdale is very low. The council have recommended that the Scottish Zoonoses Group provide an expert opinion on the public health consequences, if any, of the wider presence of beavers in Scotland, to inform the decision of Scottish Ministers on the future of beavers.

The impact of beavers on scheduled monuments was assessed by Historic Scotland. Their view is that the beavers are unlikely to have any effect on the Loch Coille-Bharr crannog, as long as the current water level of the loch is maintained in the expected range. They weren’t aware of any adverse impact on the Crinan Canal or its associated watercourses during the trial.

Veterinary monitoring of the beavers while they were at Knapdale was carried out by The Royal (Dick) School of Veterinary Studies. All 16 beavers released between 2009 and 2010 had a thorough clinical examination and were screened for a variety of animal and human pathogens before they were released. No significant pathogens were found that prevented their release. Health monitoring continued after release, until 2014, by trapping and visual observations. As a result of this monitoring one beaver was removed from the trial because of poor body condition. Two beavers died shortly after release – one with circulatory failure and one where the cause of death was not clear. Two kits died, most likely due to predation. The body weights of the adult beavers following their release have stayed within the expected weight range for Norwegian beavers.

All the reports also considered the likely future effects of beavers at Knapdale and in the event of a wider reintroduction, based on the results and conclusions from the five years of the trial.

Martin Gaywood, who leads the independent scientific monitoring of the trial for SNH said: “It’s essential that any species reintroduction project is properly managed and monitored. The independent monitoring of the Scottish Beaver Trial has helped us understand how they behave in a Scottish environment. Together with the range of work being done in Tayside and through other projects, it means that future decisions about the beavers at Knapdale and elsewhere in Scotland will be based on the best information available. We’ll be preparing a report for Ministers on the trial, which will be submitted in May 2015. The Scottish Government will then decide if beavers will be permanently reintroduced to Scotland.”

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