There are two ways of looking at beavers: they are either nature’s eco- engineers, long overdue for reintroduction to Scotland or they are the country’s newest agricultural pest, with the potential to ruin large areas of arable land.
Their suitability for reintroduction after a 400-year absence was originally to be tested by a licensed release of around 16 Norwegian beavers in Knapdale in mid-Argyll in 2009.
However, that controlled experiment has been rapidly overtaken by the unlicensed and unregulated build-up of a population in the Tay catchment area.
Whereas the Knapdale population has only built up slowly, if at all, the Tayside one has boomed and anecdotally now seems to number several hundred.
The population, which is probably longer established, originates either from escapees or deliberate releases and has obviously found the east side of the country to its liking, with family groups as far east as Kinnordy and Forfar lochs and as far west as Kenmore.
Beaver damage has recently been noted in the vulnerable drainage systems of the Carse of Gowrie.
One of the farmers suffering from beaver activity is Adrian Ivory of Strathisla Farms at Meigle.
Yesterday he was able to show this correspondent considerable damage caused by these semi-aquatic rodents right up the river system from the Isla to its tributary the River Dean, and along the Baikie Burn which flows from Airlie into the Dean.
He estimates that he is now having to spend £4,000 per year on digger hire to clear away beaver dams and on repairs to ruined drainage systems.
Along the Baikie Burn and the Dean it was easy to see quite dramatic slippage of the banks where the beavers had undermined them to create nests.
In some cases the fences were hanging in mid-air where the banks had slipped into the watercourses.
“I know some farmers have, out of desperation, cut down all the trees and bushes along the watercourses to deprive the beavers of building material but it hasn’t really worked, because they have started pulling crops such as wheat out of the fields to make dams,” he said.
Indeed it is easy to see the slides all along the bank where the beavers have been active, and the gnawed trees stumps.
Mr Ivory is in no doubt of the need to remove dams as soon as they are formed because of the effect they have on field drainage systems.
From a beaver’s viewpoint a dam is an ideal way to provide a deep upstream pool, but the effect of raising the water level on streams and ditches such as those in Strathmore is catastrophic for the drains that feed them.
Beavers have also been implicated in causing breaches of the embankments further down the Isla during November’s floods. The theory is that, by burrowing into the raised banks, they are creating a weak spot which is soon eroded into a major breach.
Ardler farmer Peter Grewar chairs the Meigle Burn Group, with its membership of eight farmers and two house owners. He said: “Since June 2013 we have removed 32 beaver dams, three in the last four weeks.
“We have to inspect our watercourses regularly to identify the new sites and remove the dams before they cause flooding damage to good arable land.
“Also, the longer they are left, the bigger they become and the more difficult to remove.
“The dams also cause bank erosion, which puts sediment into the watercourses.
“We are experimenting with removing trees, the beavers’ food source, from the banks of various reaches.
“This is only partially successful as one dam has been made with a growing crop of wheat where no trees were available.
“Any planned level of protection for beavers must be resisted.”
Mr Ivory made the same point as regards giving the Tay beavers protected status, and said it was also vital to be allowed to continue to remove dams.
The problems have been building up for three or four years, but addressing them has now become critical.
The £2 million Knapdale project is now complete, and a 176-page report has been lodged.
The Perth-based Tayside Beaver Study Group is monitoring the population in the east and has been capturing animals for blood and genotype testing.
Beavers can carry bovine TB, but the population appears to be free of the disease.
It has also been established that the beavers are all of the Eurasian type and not the allegedly more destructive American type.
There is now some urgency about the situation, with decisions scheduled to be made this year on the future of the Tayside beavers.
In theory, at one extreme there could be an attempt to exterminate the population but this is unlikely to be a practical option. Attempts to eradicate wild mink are now decades old and have only had limited impact.
At the other extreme, beavers could be given full protection but from the evidence to date, this would cause agricultural havoc.
The most likely outcome will be compromise. Some commentators have suggested following the example of various European countries where there is zoning, with populations being licensed to develop unhindered in higher wilder country but strictly controlled in arable areas.
Scottish Land & Estates: A spokesman for Scottish Land & Estates said: “We have raised the issue of the Tayside beaver population with the Environment Minister. “Our concerns are mainly on the flood risk to high-quality arable ground, but also to rural communities, as well as tree damage and crop foraging. “There is a need for robust management and sufficient controls to bring about balance between the natural and farmed environments,” he added.
NFU Scotland: An NFU Scotland policy document says: “We are deeply sceptical that beavers can be excluded from areas of farmland that are heavily reliant on complex drainage systems. “NFUS also believes beaver reintroduction would divert resources and attention away from helping existing species such as the wildcat and the capercaillie which are under threat.”
The supporters: Louise Ramsay and her husband Paul from Bamff Estate near Alyth are beaver enthusiasts and have allowed their own population of the animals to create wetland areas within the estate. “I realise we are in a bit of a crisis at the moment, and we are very interested in helping to solve the problems,” said Mrs Ramsay. “I know the difficulties of managing beaver populations on the low ground and am not against zoning proposals. “The ideal scenario would see low-ground beavers allowed in certain places. “They can actually have a role in preventing flooding as has been proved in Holland, where they are regarded as essential and have helped to re-meander certain watercourses,” said Mrs Ramsay. “I am sure there are mitigation measures which would allow beavers and farmers to co-exist,” she added. The Tayside Beaver Study Group also encourages mitigation measures, with a section of its website devoted to describing various methods including installing dam drainage devices and electric fencing.