Alien species can exert negative environmental and socio-economic impacts. Therefore, administrations from different sectors are trying to prevent further introductions, stop the spread of established species, and apply or develop programs to mitigate their impact, to contain the most harmful species, or to eradicate them if possible. Often it is not clear which of the numerous alien species are most important in terms of damage, and therefore, impact scoring systems have been developed to allow a comparison and thus prioritization of species. Here, we present the generic impact scoring system (GISS), which relies on published evidence of environmental and socio-economic impact of alien species. We developed a system of 12 impact categories, for environmental and socio-economic impact, comprising all kinds of impacts that an alien species may exert. In each category, the intensity of impact is quantified by a six-level scale ranging from 0 (no impact detectable) to 5 (the highest impact possible). Such an approach, where impacts are grouped based on mechanisms for environmental impacts and receiving sectors for socio-economy, allows for cross-taxa comparisons and prioritization of the most damaging species. The GISS is simple and transparent, can be conducted with limited funds, and can be applied to a large number of alien species across taxa and environments. Meanwhile, the system was applied to 349 alien animal and plant species. In a comparison with 22 other impact assessment methods, the combination of environmental and socio-economic impact, as well as the possibility of weighting and ranking of the scoring results make GISS the most broadly applicable system.
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We thank Elfi Kühnel, Thomas Evans, Ciaran Laverty, Zuzana Marková, Jan Pergl, Sibylle Vaes-Petignat, and Gabriel van der Veer for their contributions to the development of the GISS; Pablo González-Moreno for the development of the excel version of the GISS; Marianne Kettunen for a discussion on socio-economy; Myles Menz for text improvement; and our reviewers for their comments. The support from COST Actions TD1209 Alien Challenge and ES1304 ParrotNet is gratefully acknowledged. SK acknowledges financial support from the South African National Department of Environment Affairs, the DST-NRF Centre of Excellence for Invasion Biology, and the Swiss National Science Foundation; PP was supported by long-term research development project RVO 67985939 and Praemium Academiae award (from The Czech Academy of Sciences), and by the Centre of Excellence PLADIAS (Czech Science Foundation project no. 14-36079G) and MV by the Ministerio de Economia y Competitividad projects FLORMAS (CGL 2012–33801), IMPLANTIN (CGL2015-65346R) and the Severo Ochoa Program for Centres of Excellence (SEV-2012-0262).
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Appendix S1. A spreadsheet table (in Microsoft Excel) to perform the Generic Impact Scoring System GISS. (XLSX 68.3 kb)
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Nentwig, W., Bacher, S., Pyšek, P. et al. The generic impact scoring system (GISS): a standardized tool to quantify the impacts of alien species. Environ Monit Assess 188, 315 (2016). https://doi.org/10.1007/s10661-016-5321-4