Special Issue "Recent advancements in the risk screening of freshwater and terrestrial non-native species"

In the last decades, a large number of non-native species (NNS) has been identified in several invaded areas worldwide. However, in both the European Union and other developed countries, despite existing measures for prevention and control, extant NNS are still expanding their distributional range and new NNS are being recorded. Whereas in developing countries, legislation for the successful management and control of (invasive) NNS is increasingly needed. Further, the invasiveness potential of NNS in several taxonomic groups remains unknown due to the lack of supporting risk screening studies, which are of crucial importance especially in those geographical areas acting as biodiversity hotspots. For the above reasons, there is room for improvement in risk screening studies to fill out these knowledge gaps.

Risk analysis studies provide crucial information for environmental managers and policy makers to prioritise decisions in view of appropriate management and conservation measures for both aquatic and terrestrial biodiversity. Furthermore, quantifying the invasiveness potential of NNS can contribute important knowledge towards invasive species biology. In this context, the first step in risk analysis studies is screening (i.e. hazard identification), which aims to identify the NNS that are likely to pose an elevated threat to native species and ecosystems in the risk assessment area and, therefore, warrant more comprehensive (i.e. full) risk assessment. This examines in detail the risks of:

• introduction (entry);
• establishment (of one or more self-sustaining populations);
• dispersal (more widely within the risk assessment area, i.e. so-called secondary spread or introductions); and
• impacts (to native biodiversity, ecosystem function and services, and the introduction and transmission of diseases).

Previously published papers on risk screening of aquatic NNS, and especially those using the most widely-employed ‘-ISK’ decision-support toolkits (see https://doi.org/10.1016/j.envsoft.2020.104900), have attracted mounting interest from the wider scientific community and have been extensively cited (see https://doi.org/10.1007/s11160-019-09562-2; https://doi.org/10.1016/j.scitotenv.2021.147868). However, despite these numerous applications, there remain several knowledge gaps in NNS risk screening with special relevance to the following topics:

• the relative dearth of information on the invasiveness of aquatic NNS in taxonomic groups other than fishes and invertebrates;
• the paucity of risk screening studies focusing on biodiversity hotspots and/or tropical areas;
• the requirement for updated information on species invasiveness within a dynamic risk screening and comparative perspective; and
• the need for a taxon-generic decision-support toolkit for the screening of terrestrial animals and related applications.