Previously extinct in the UK, in May 2009 the few first individuals of an ambitious beaver reintroduction trial were released at Knapdale, Scotland. Over the course of the following months, a total of 15 Eurasian beavers (Castor fiber) were introduced to the trial site, a topic of much debate.
Work on the beaver reintroduction programme began as early as 1995, and the resulting trial will last 5 years and be the subject of careful monitoring. Beavers have been extinct in the UK for around 400 years, their decline a result of overhunting for their fur and castoreum, a secretion used for medicinial purposes. Hunting led to a decline across the entire range of the beaver, causing numbers to plummet and subsequent extinction in many European countries. Wild populations are today present across much of mainland Europe, spreading into China and Mongolia, with successful reintroductions in countries such as Romania, The Netherlands and Sweden.
Reintroduction of beavers to Scotland is a contentious issue. Those opposing the trial may do so for several reasons. Firstly, the term ‘ecosystem engineer’ may be applied to beavers, referring to their ability to change the habitat in which they live. The creation of dams, though not carried out by all beavers, may slow the water flow and trees in the surrounding area will become food sources. As with any introduction, any change to the area may disrupt the landscapes current ecology, favouring or troubling a species survival, though beavers dams may be beneficial by regulating flooding, retaining water during drought. The use of surrounding trees for feeding may encourage diversity by allowing others to grow. Consequently, intensive monitoring by independent organisations of the impact of beavers at the trial site is carried out. It should be considered that beavers were once a natural part of the British landscape, their absence man-made and relatively short-term.
The water quality in surrounding areas has also been a concern voiced; The Eurasian beaver often carries parasites, in particular Giardia lamblia , which may cause symptoms such as fever and diarrhoea in humans. Sampling of streams around the reintroduction site, however, showed G. lamblia (which may also be carried by other animals) to be already present, though the monitoring of other changes, whether changes in abundance or new species, is essential.
The trial may thus far be considered a success. In Spring 2010, the first kits were born, more of which have since followed. Some small dams and lodges have been built, all of which were in the loch rather than stream area. Independent analysis has determined that the beavers have had little impact on the water quality or surrounding areas, and the public have been increasingly involved in the programme. A full analysis will be completed in 2014, and the decision to launch a full reintroduction programme or not made. The trial has now been underway for just under 3 years, and, if everything continues to run smoothly, there may soon be a larger beaver population recolonising the rivers of the United Kingdom.