A geospatial analysis of ecosystem engineer activity and its use during species reintroduction

The Scottish Government has announced that they are minded to allow reintroduced populations of Eurasian beaver (Castor fiber), an ecosystem engineer, to remain in Scotland. Some species and habitats of conservation importance may be affected by the activities of an ecosystem engineer. The study had two key objectives: to identify the potential location of the beaver’s two ecosystem engineering activities and to assess risks to vulnerable habitats and species. To identify potential core beaver woodland, a rule-based species distribution model was developed which included a novel method of integrating beaver territory size requirements. This was used to further predict where beavers would be unlikely to dam. We used the models to assess the spatial overlap between ecosystem engineering activities (i.e. herbivory and damming) with habitats and species of conservation importance. One hundred and five thousand five hundred eighty-six hectares of core beaver woodland was identified, which predicted the location of beaver herbivory. Our model successfully predicted the location of beaver activities surveyed in the largest beaver population in Scotland. Extensive overlap was predicted between beaver herbivory and habitats of conservation importance, in particular aspen woodland, Atlantic hazelwood, and alluvial forests. Eighty-seven percent of watercourses in Scotland were outside the beaver damming model, and hence had a lower likelihood of being dammed. The majority of freshwater pearl mussel, lamprey and Atlantic salmon Special Areas of Conservation, were in river sections less likely to be dammed. If beavers recolonise their former range in Scotland, ecosystem engineering activities are likely to be extensive. However, any impacts on vulnerable species and habitats will be in specific areas and will need to be monitored.