When most people think of beavers, the first thing that comes to mind is the incredibly elaborate dam structures they manage to carve from simple pieces of spare timber. What most don’t think about is their role as a keystone species in wetland areas, and the effects of their loss on those environments. Beavers build dams that slow down or block off waterways, creating new ecosystems for species to build themselves around and stimulating the growth of wetland biodiversity¹. Eurasian Beavers (Castor fiber) used to be quite prominent in Scottish wetlands before they were hunted to extinction in the 16th century, dealing a significant blow to the biodiversity of these areas that have not since recovered². The purpose of this research was to determine if their reintroduction to wetland areas through rewilding efforts could restore the abundance of species seen previously and increase overall biodiversity of wetlands in Scotland.

To better determine what positive effects introducing new beavers could have on these ecosystems, researchers at the Royal Zoological Society of Scotland, the Scottish Wildlife Trust and the Forestry Commission Scotland started the Scotland Beaver Trial in 2009. This study involved releasing four families of Eurasian Beavers into Knapdale Forest in the Heart of Argyll and closely monitoring them for the next five years. The goal of the trial was to assess what impacts the new species would have on the ecosystem and if their presence was more overall beneficial or harmful⁴.

Concerns that the study had to address were those of introducing any new species- how well the beavers would fit into their new ecosystem without actively disrupting the existing populations of other species already living there. It was also theorized that beavers being introduced could be devastating to species that relied on the woodlands for habitats such as woodland lichens and fungi communities⁶, considering beavers would be routinely destroying these trees for dam-building supplies. There was also concern about the fish population, as the construction of these dams-while beneficial for creating pools of still water that would attract a variety of species- would impede or trap the fish populations that passed through the waterways. This was an important point, as fishing was vital to the people of Knapdale. In the same vein, fears existed of croplands being flooded by water displacement from the dams when these streams would be stopped or redirected due to beaver activity⁷.

In order to address these concerns, regulations were enacted during the study to manage the beavers’ activities as well as monitoring species that could be negatively affected. These regulations included keeping the beavers within the boundaries of the research area, and “Beaver Management Groups” were formed to monitor the interactions between beavers and the existing species of the wetlands in case issues arose. Despite these protocols having to be issued in order to gain support for the project to move forward, the goal of the study was still to observe both beneficial and detrimental aspects of the beaver reintroductions for future research purposes⁸.

After five years, the study found that the structures built by the beavers eventually became overgrown and did indeed create sprawling new habitats in previously barren marshes. The researchers established regulations to limit areas the beavers could transform to minimize potential harm to the overall ecosystem, specifically ensuring no more than fourteen dams were built alongside approved waterways. A negative aspect the researchers did not account for initially that quickly arose was the observation of a parasite (Stichorchis subtriquetrus) that had been introduced to the wetlands by the introduction of previously infected beavers that had been illegally introduced¹⁰. The study was however still able to continue and make progress in the diagnosis/treatment of these previously unheard-of parasitic infections, from which new information was gained about the behaviors of beavers in these wetland environments.

While the study certainly had its issues, it clearly provided evidence that beavers could offer a solution to reduced biodiversity in Scottish wetlands. Even though it’s true that their dams are made from the destruction of forests alongside the waterways, these effects can be minimized through supervision of their activities by newly established monitoring methods. Since the trial’s conclusion in 2015, new studies have explored the research further to measure the impact on biodiversity through other factors. In 2018, The Royal Society conducted a plant and water beetle survey at similar wetland sites between Örebro and Skinnskatteberg in central southern Sweden, which was similarly being considered for revitalization through beaver reintroduction. After beavers were reintroduced, the surveys found plant species diversity to be 17% higher in environments where beavers were present, and water beetles to be 26% more abundant¹¹. From these findings, it was inferred that beavers reshaped their environments in such a way to increase wetland plants and insects, which would naturally then attract additional species and continue to revitalize these ecosystems.

The studies presented show that beaver reintroduction can have unintended consequences on the ecosystem of wetland communities such as introduction of parasites, but their environmental engineering practices can revitalize biodiversity as well. There is still further research to be done as it is still a relatively unexplored field, but currently beavers stand as an efficient method of combating the rapid biodiversity loss present in UK wetlands¹².