The relevance of using various scoring schemes revealed by an impact assessment of feral mammals

Bianca L Hagen,Sabrina Kumschick

doi:10.3897/neobiota.38.23509

Abstract

Impact scoring schemes are useful for identifying to what extent alien species cause damage. Quantifying the similarity and differences between impact scoring schemes can help determine how to optimally use these tools for policy decisions. Using feral mammals (including rats and mice) as a case study, environmental and socio-economic impacts were assessed using three schemes, namely the Generic Impact Scoring System (GISS), Environmental Impact Classification for Alien Taxa (EICAT) and Socio-Economic Impact Classification for Alien Taxa (SEICAT). The results show that socio-economic impacts scores differ between the respective schemes (GISS and SEICAT) possibly because they assess different aspects of social life and economy. This suggests that both scoring schemes should ideally be applied in concert to get a complete picture of socio-economic impacts. In contrast, environmental impact scores are correlated between GISS and EICAT assessments and this similarity is consistent over most mechanisms except for predation and ecosystems, suggesting that one scoring scheme is sufficient to capture all the environmental impacts. Furthermore, we present evidence for the island susceptibility hypothesis as impacts of feral mammals were found to be higher on islands compared to mainlands.

Highlights

Alien species cause various and sometimes devastating changes to the environment where they are introduced and influence social and economic aspects of human life (e.g. Pyšek and Richardson 2010, Vilà et al 2010, Kumschick et al 2015, Bacher et al 2017)
9% of the species’ scores were equivalent, whereas more than 81% of the species scored higher in Generic Impact Scoring System (GISS) than in Socio-Economic Impact Classification for Alien Taxa (SEICAT). This higher score was mostly by a single magnitude (e.g. 4 in GISS and MO in SEICAT), except for S. scrofa where the schemes differed by two magnitudes (5 versus MO)
While summed SE_GISS scores in this case never exceeded 15, SEICAT scores ranged from MN to MR

Summary

Introduction

Alien species cause various and sometimes devastating changes to the environment where they are introduced and influence social and economic aspects of human life (e.g. Pyšek and Richardson 2010, Vilà et al 2010, Kumschick et al 2015, Bacher et al 2017). To minimise the negative effect of alien species, the Convention on Biological Diversity in its Aichi target 9 has proposed steps to mitigate their impacts, including identifying harmful alien species and prioritising their management (www.cbd.int/sp/ targets/). To reach these goals, standardised measures for impact assessment and species prioritisation are needed. Hawkins et al 2015, Nentwig et al 2016, Bacher et al 2017; see Leung et al 2012 for a review on risk assessments more broadly) Such schemes are typically based on published evidence of impacts or expert opinion and are meant to be transparent, robust and easy to use (Vanderhoeven et al 2017). Differences in the outcomes using these schemes can potentially influence policy decisions and, for this reason, there is a need to quantify whether impact assessment schemes are comparable

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