Environmental and economic impact of alien terrestrial arthropods in Europe

In the last decades abundance and importance of invasive alien species has grown continuously due to the undiminished growth of global trade. In most cases, arthropod introductions were unintended and occurred as hitchhikers or contaminants. Alien arthropods can have significant environmental impacts and can be economically costly. To measure these impacts, we expand the generic impact scoring system initially developed for mammals and birds, and applied it to terrestrial arthropods. The scoring of the 77 most widely distributed arthropod species alien to Europe revealed the mite Varroa destructor as the most harmful species, followed by the Chinese longhorn beetle Anoplophora chinensis and the Argentine ant Linepithema humile. The highest environmental impact is through herbivory, disease transmission, and ecosystem impacts. The highest economic impact is on agriculture and human infrastructure. The generic impact scoring system allows comparing impact scores of vertebrates and arthropods, thus serving as a background for decision making processes of policies and stakeholders.