A Generic Impact‐Scoring System Applied to Alien Mammals in Europe

We present a generic scoring system that compares the impact of alien species among members of large taxonomic groups. This scoring can be used to identify the most harmful alien species so that conservation measures to ameliorate their negative effects can be prioritized. For all alien mammals in Europe, we assessed impact reports as completely as possible. Impact was classified as either environmental or economic. We subdivided each of these categories into five subcategories (environmental: impact through competition, predation, hybridization, transmission of disease, and herbivory; economic: impact on agriculture, livestock, forestry, human health, and infrastructure). We assigned all impact reports to one of these 10 categories. All categories had impact scores that ranged from zero (minimal) to five (maximal possible impact at a location). We summed all impact scores for a species to calculate "potential impact" scores. We obtained "actual impact" scores by multiplying potential impact scores by the percentage of area occupied by the respective species in Europe. Finally, we correlated species' ecological traits with the derived impact scores. Alien mammals from the orders Rodentia, Artiodactyla, and Carnivora caused the highest impact. In particular, the brown rat (Rattus norvegicus), muskrat (Ondathra zibethicus), and sika deer (Cervus nippon) had the highest overall scores. Species with a high potential environmental impact also had a strong potential economic impact. Potential impact also correlated with the distribution of a species in Europe. Ecological flexibility (measured as number of different habitats a species occupies) was strongly related to impact. The scoring system was robust to uncertainty in knowledge of impact and could be adjusted with weight scores to account for specific value systems of particular stakeholder groups (e.g., agronomists or environmentalists). Finally, the scoring system is easily applicable and adaptable to other taxonomic groups.

[1]  D. Simberloff,et al.  BIOTIC INVASIONS: CAUSES, EPIDEMIOLOGY, GLOBAL CONSEQUENCES, AND CONTROL , 2000 .

[2]  E. Grosholz.  Contrasting Rates of Spread for Introduced Species in Terrestrial and Marine Systems , 1996 .

[3]  Sergej Olenin,et al.  Assessment of biopollution in aquatic ecosystems. , 2007, Marine pollution bulletin.

[4]  James M. Bullock,et al.  The impacts of non-native species on UK biodiversity and the effectiveness of control. , 2000 .

[5]  D. Strayer,et al.  Invasion success of vertebrates in Europe and North America. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[6]  Piero Genovesi.  Eradications of invasive alien species in Europe: a review , 2005 .

[7]  M. Bomford.  RISK ASSESSMENT FOR THE IMPORT AND KEEPING OF EXOTIC VERTEBRATES , 2003 .

[8]  David Pimentel,et al.  Biological Invasions : Economic and Environmental Costs of Alien Plant, Animal, and Microbe Species , 2002 .

[9]  M. Graham.  CONFRONTING MULTICOLLINEARITY IN ECOLOGICAL MULTIPLE REGRESSION , 2003 .

[10]  Petr Pyšek,et al.  Predicting invasions by woody species in a temperate zone: a test of three risk assessment schemes in the Czech Republic (Central Europe) , 2006 .

[11]  Jan Zima,et al.  The Atlas of European Mammals , 1999 .

[12]  M. S. Hoddle,et al.  Population biology of invasive species. , 2001 .

[13]  Wolfgang Nentwig,et al.  Grasping at the routes of biological invasions: a framework for integrating pathways into policy , 2008 .

[14]  T. Blackburn,et al.  Determinants of establishment success in introduced birds , 2001, Nature.

[15]  Martin A. Nuñez,et al.  Gringos En El Bosque: Introduced Tree Invasion in a Native Nothofagus/Austrocedrus Forest , 2002, Biological Invasions.

[16]  K. S. Smallwood,et al.  A rating system for potential exotic bird and mammal pests , 1992 .

[17]  Petr Pyšek,et al.  Traits Associated with Invasiveness in Alien Plants: Where Do we Stand? , 2008 .

[18]  Daniel Sol,et al.  Brain Size Predicts the Success of Mammal Species Introduced into Novel Environments , 2008, The American Naturalist.

[19]  J. L. Long.  Introduced Mammals of the World: Their History, Distribution and Influence , 2003 .

[20]  C. Daehler.  PERFORMANCE COMPARISONS OF Co-OCCURRING NATIVE AND ALIEN INVASIVE PLANTS: Implications for Conservation and Restoration , 2003 .

[21]  D. Richardson,et al.  Plant invasions: merging the concepts of species invasiveness and community invasibility , 2006 .