Monday, 3 August 2009

Beaver Reintroduction - Dr Keith Skene

There are three issues: philosophical, biological and ecological

1. Philosophical
Garden of Eden Fantasy
What I also refer to as “Golden Age environmentalism”, the compulsive yet foundationless desire to recreate some habitat from the past, by “re-wilding”. This is a very strange concept, given that you cannot go back in time. What is Eden, and when was it? 15000 years ago, for example, most of Britain was covered in ice. It’s a bit like plastic surgery – it may make you look 20 years younger, but beneath it, you’re still the same age, and getting older by the day! Unfortunately, some of our leading environmental organizations practice this cosmetic approach to conservation. Scottish Natural Heritage, for example, appears to be playing a game of King Canute at Tentsmuir National Nature Reserve, where they cut down birch and willow in an attempt to “freeze” the dune system.

We live in a changing world: communities have evolved away from what they were 400 years ago, when the beaver was last in Scotland, and from 800 years ago, when the beaver was in England. The industrial and agricultural revolutions, human population expansion, urbanization and climate change have made this a very different place.

2. Biology
The European beaver is actually made up of 8 sub-species. The decision to move one of these, the Norwegian sub-species, to Scotland is extremely dubious. At the end of the last ice age, the most likely sub species was the French one (Castor fiber gallicus), because the land bridge was to France, not to Norway. Norway was covered in ice just like Britain, and so the Mediterranean refuges were much more likely to form the source of our beavers. DNA analysis of beaver pelts from British beavers could be done to check this, but, surprisingly, this hasn’t been done.

A study in the journal Molecular Ecology by Walter Durka (Germany) and his colleagues – leading expert) stressed that geographically nearest form should be used, and that there was a huge danger related to re-wilding in terms of the future evolution of the beaver. In evolutionary terms, species start off as sub-species, and to intervene in this process by moving groups around the continent, we are potentially impacting on the future direction of Beaver evolution.

3. Ecology
The context of an organism is everything. Every species needs food and a predator for a natural balance to be achieved. Without the predator, the population will, always, spiral out of control without culling. But what is the point of bringing the beaver here just to be culled? There is a moral issue here. Beavers are advanced mammals, and so if our actions deliberately lead to us needing to cull, then this is not a positive approach. Culling is also not a simple process.

By killing particular beavers, we will not necessarily replicate the natural force of predation, because we may not kill the weaker beavers, but rather the stronger ones (for example those that disperse most). This can lead to a genetically weakened population, and thus to all sorts of genetic problems.

Suggestions that beavers that spread too far will be culled, in order to prevent their spread, are also extremely worrying. For example, after 2 years, juvenile beavers migrate from their natal site. They can travel up to 150 km. The reasons for this are to reduce population load at a particular habitat, and, even more importantly, to prevent inbreeding. If we do not allow these migrations to happen, inbreeding depression will occur, and this can lead to terrible deformities. Do we really want this? To avoid this, we would need to allow these migrations. If we do this, then there can be no control on the spread of these creatures, and they are likely to encounter roads, probably acting as a significant hazard to drivers.

It is no use citing examples that have run for 30 years in mainland Europe. Most of these have been disastrous in terms of mixing sub-species anyway. The consequences of genetic inbreeding play out over much greater timescales, but are likely to happen more quickly if the introduced populations are of the same subspecies, as mating between different sub-species (which must not happen) leads to genetic outbreeding (also a potential disaster, as specialized traits can be diluted or destroyed). The introductions of the sixties involved different sub-species, and so are not comparable to the single sub-species introductions to be used in the UK. So as we improve our purity of introduced individuals, ironically, we will increase the risk of inbreeding depression happening much more quickly.

As we have seen re-wilding is not a sensible idea. Neither is the use of the beaver for tourism. First, they are basically nocturnal, and in a British summer, this will mean 10pm. Shortly after seeing them, it gets dark. So safety concerns will come into play, as tourists have to try to get back off the water or river bank in dark conditions. Secondly, the moral issue of disturbing a shy and reclusive animal must be considered. The beavers do not want to be seen, and ecological tourism will be very detrimental to them, stressing them, and suppressing their immune system, due to an increase in cortisol levels. This will increase their susceptibility to a range of diseases, potentially leading them to become disease vectors. This has been widely researched, for example with mountain gorilla tourism of the 1980s.

One beaver family destroys 300 young trees in a single winter. Tree regeneration is difficult enough with rabbits and deer already putting unacceptable pressure upon young saplings. However the beaver removes bark, which contains the main transport system for sugar, thus killing the tree. Grey squirrels also do this, and so in combination, this is an unacceptable problem.

To use the beaver as a means of terraforming (changing a habitat into one that works for us) is an extremely risky strategy. The Harlequin ladybird was introduced to act as a predator on aphids, and now its population has run out of control in the UK and threatens many of our native ladybirds. The cane toad, introduced to Australia to kill insect pests of sugar cane, didn’t eat the pests, but instead ate many endangered insects, and has greatly damaged the other species. Biological control and biological engineering is never likely to work because the ecology is usually too complex to model and predict. It is like a car mechanic attempting brain surgery. In fact it is like a brain surgeon attempting brain surgery – the outcome is not secure.

Dr Keith Skene is the Convenor of the Board of Environmental and Applied Biology at Dundee University. His areas of expertise include Forensic Science. Conservation biology. Global Warming, Ecology and Botany. His latest book 'Shadows on the Cave Wall: A New Theory of Evolution', is now available exclusively from the publisher at:


  1. I think this is one of the best reasoned arguments against this introduction stupidity that I've read,I'ts a great shame that it didn't appear earlier, when the press were doing their silly pieces about the release.Sadly it's unlikely that SNH, or SWT will reply as they are so sure that they are right, that Dr Skene has therefore to be wrong.It is a damning indictment of the press that not one paper or programme,cares enough to call the Minister,SNH and SWT to task.

  2. We have received some positive coverage from the Daily Mail (London) this month. See the following two articles:;col1