Environmental suitability and potential range expansion of the Eurasian beaver in Italy

Reintroduction and rewilding initiatives are key strategies to reverse human impacts on ecosystems and re-establish natural processes. However, rewilding may involve complex management scenarios, because many expanding species can have economic impacts and cause human–wildlife conflicts. Conflicts can be particularly challenging when carnivores, large herbivores and ecosystem engineers are involved. The Eurasian beaver (Castor fiber) is a key ecosystem engineer that was once present in a large part of the Palearctic, but in Medieval times underwent a severe decline due to the joint effects of habitat loss and hunting. Subsequent legal protection and reintroductions triggered the recovery of the species through most of its original range. Eurasian beavers recently started the recolonization of Italy, because of the joint effects of natural dispersal (from Austria to northern Italy) and illegal reintroductions (central Italy). The lack of data on the most likely colonization routes hampers appropriate management of this species. Here, we identified the areas where beaver populations are most likely to arrive in the near future within Europe, with a specific focus on Italy. First, we developed spatially cross-validated species distribution models to identify the areas with the highest suitability for the Eurasian beaver in Europe. Second, we used connectivity modelling to assess the possible expansion routes of this species in Italy. Large areas of Europe are suitable for the beaver and may soon be colonized. The connectivity model showed a high potential for expansion from central Italy to surrounding areas, while the high isolation of northern Italy populations suggests a slower expansion. Our results can help environmental managers to understand where to focus both the future monitoring of beaver populations and actions aimed at preventing and mitigating possible human–wildlife conflicts that could arise from the expansion of an environmental engineer such as the beaver.