The Tay Beavers furore has died down at the moment. Scottish Natural Heritage (SNH) stopped their capture programme back at the end of March to allow female beavers to have their young. Various meetings have taken place to try and resolve the issue, and these will continue through the summer. The outcome is uncertain, with much depending on the stance taken by the new incoming Government.

Efforts are ongoing to try and get a better idea of how many beavers there are on Tayside, and it now looks fairly certain that there are many, many more than was first supposed. They do indeed seem to breed and spread much faster than we would have imagined, but does this make them an invasive species, one that is difficult to control and which does immense damage to riparian habitats?
Like a number of others recently, I have been looking for beaver signs in Highland Perthshire, beyond the areas where they are well recognized to be currently residing.
Invasive species should be easy to find, especially ones that cut down trees. You would expect to see signs everywhere, but this is not really the case.

What Do Beavers Eat?
Actually, at this time of year, it is mostly grass and forbs and other bankside vegetation. Not trees, and certainly not fish or small children as some people might try to tell you. Have a look at this photograph of a beaver lawn taken by Paul Scott. Would you even notice this, or recognise that a beaver is feeding here in the area outlined? 
More than anything else, this has emphasised to me the steep learning curve we are on in relation to these animals, and explains why there can apparently be so many of them without leaving behind too much in the way of evidence.
The occasional willow branch is getting chewed off at present (as first picture above) but these are few and far between. Certainly on the main rivers these animals can exist, at least at low density, with minimal obvious signs in the landscape.

Real Invasive Species
While out looking for beavers on the Tummel, I quickly came upon some Himalayam balsam, (pictured) which is a real, proper invasive species. It spreads very rapidly and is getting out of control on Tayside, including now in Highland Perthshire. It does produce plenty of flowers for pollinators in late summer, but in every other way, it really is a problem.
 These species are supposedly a priority for government, but the grant schemes are still too bureaucratic and new powers under the Wildlife and Natural Environment (WANE) Bill are yet to be implemented or funded. All the time, it spreads further.
Although not invasive as such, sycamore trees (pictured), a non-native but naturalised species, will quickly colonise riparian woodlands, out-compete native trees and shade out bankside vegetation, inducing erosion and loss of biodiversity.
It is not classified as “invasive” because in the right situations, it can be a valuable and useful tree, but it is unquestionably a problem species in many riparian situations.
Both these latter species are a much greater threat to our riparian habitats than beavers at present, but they are simply not as newsworthy or exciting. Ultimately, a means of controlling beavers will have to be devised, simply because it will be necessary in some areas, but will we get a system in place which can effectively deal with real invasive species before they get too well established?
Here are three species, classified in different ways, giving problems in different ways, presenting opportunities in different ways. How would you prioritise them? If you were a government agency, which would/ should you want to get rid of first?

Victor Clements - Scottish Native Woods


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