Katharina Lapin , Sven Bacher , Thomas Cech , Rok Damjanić , Franz Essl , Freya-Isabel Georges , Gernot Hoch , Andreja Kavčič , András Koltay , Saša Kostić , Ivan Lukić , Aleksander Marinšek , László Nagy , Sanja Novak Agbaba , Janine Oettel , Saša Orlović , Leopold Poljaković-Pajnik , Markus Sallmannshofer , Martin Steinkellner , Srdjan Stojnic , Marjana Westergren , Milica Zlatkovic , Anita Zolles , Maarten de Groot
October 07 2021
October 07 2021
The prioritization of alien species according to the magnitude of their environmental impacts has become increasingly important for the management of invasive alien species. In this study, we applied the Environmental Impact Classification of Alien Taxa (EICAT) to classify alien taxa from three different taxonomic groups to facilitate the prioritisation of management actions for the threatened riparian forests of the Mura-Drava-Danube Biosphere Reserve, South East Europe. With local experts we collated a list of 198 alien species (115 plants, 45 insects, and 38 fungi) with populations reported in southeast European forest ecosystems and included them in the EICAT. We found impact reports for 114 species. Eleven of these species caused local extinctions of a native species, 35 led to a population decrease, 51 to a reduction in performance in at least one native species and for 17 alien species no effects on individual fitness of native species were detected. Fungi had significantly highest impact and were more likely to have information on their impacts reported. Competition and parasitism were the most important impact mechanisms of alien species. This study is, to our knowledge, the first application of EICAT to all known alien species of several taxonomic groups in a protected area. The impact rankings enabled to identify taxa that generally cause high impacts and to prioritize species for the management in protected areas according to their impact magnitudes. By following a standardized impact protocol, we identified several alien species causing high impacts that do not appear on any expert-based risk list, which are relevant for policymakers. Thus, we recommend that alien species be systematically screened to identify knowledge gaps and prioritize their management with respect to spatio-temporal trends in impact magnitudes.