Prioritising the management of invasive non-native species

Abstract

Invasive non-native species (INNS) are a global threat to economies and biodiversity. With large numbers of species and limited resources, their management must be carefully prioritised; yet agreed methods to support prioritisation are lacking. Here, methods to support prioritisation based on species impacts, pathways of introduction and management feasibility were developed and tested. Results provide, for the first time, a comprehensive list of INNS in Great Britain (GB) based on the severity of their biodiversity impacts. This revealed that established vertebrates, aquatic species and non-European species caused greater impacts than other groups. These high impact groups increased as a proportion of all non-native species over time; yet overall the proportion of INNS in GB decreased. This was likely the result of lag in the detection of impact, suggesting that GB is suffering from invasion debt. Testing methods for ranking the importance of introduction pathways showed that methods incorporating impact, uncertainty and temporal trend performed better than methods based on counts of all species. Eradicating new and emerging species is one of the most effective management responses; however, practical methods to prioritise species based both on their risk and the feasibility of their eradication are lacking. A novel risk management method was developed and applied in GB and the EU to identify not only priority species for eradication and contingency planning, but also prevention and long term management. In this way, long lists of species were reduced to management focussed short lists that provided better cost-benefit than risk assessment alone. These pathway ranking and species prioritisation methods complement risk assessment and horizon scanning tools within a wider risk analysis framework for prioritisation. While applied here to identify management priorities in GB and the EU, they are flexible and could help prioritise INNS management at local, national and international scales.