Scottish beavers – No effect on streams so far

Beavers were released at vast expense in 2009. Photo SNH

Following their reintroduction to Knapdale forest near Lochgilphead in May 2009, as part of the Scottish Beaver Trial, SNH have been closely monitoring the effects of beavers on the environment in partnership with a number of other independent organisations.

Limited number of beaver dams
In autumn 2010, researchers at the University of Stirling re-surveyed 12 rivers and streams in the area used by the beavers, to assess their effects on stream habitats and landforms. They looked at a range of features including bankside vegetation; size and shape of the stream channel; the stability of the banks and the amount of woody debris in the stream. The results show that there has been a minimal change in the streams since the beavers were reintroduced. Small dams have been built in a few places but these were limited in number and scale.

Beavers settled in lochs
Angus Tree, who manages the independent river habitat monitoring for SNH explained: "It's notable that the beavers are having little effect on the streams in the area - this is because they have been concentrating nearly all of their activity around the lochs where they were originally released and have now settled. However, it's probable that they'll begin to use the rivers and streams more in future years, as their numbers increase and they spread further afield. This particular survey didn't cover the lochs, such as Dubh Loch, where more obvious changes are being seen, but that will be covered in a separate report to be published next year."

David Gilvear, Professor of River Science at the University of Stirling said: "It is widely known that beavers modify streams by damming, felling and caching food. These modifications are undertaken for their own benefit but at the same time create new aquatic features that provide habitat for a range of other plant and animal species. To date at Knapdale, such changes have not been apparent due to the beavers spending most of their time on the lochs. If the beavers do decide to live on the streams full-time, the monitoring being undertaken will pick up any physical impacts on the river margins, river banks and stream bed."

Angus added: "Beavers have complex effects on the environment, and measuring these changes is essential. The results of the monitoring work we're doing with our partners will give the Scottish Government the information they need to decide whether beavers should be permanently reintroduced to Scotland."

SNH will also publish the first in a series of reports on the socio-economic evaluation of the trial in the near future. Produced by the Scottish Agricultural College, it will set out the methods that will be used.