How repeatable is the Environmental Impact Classification of Alien Taxa (EICAT)? Comparing independent global impact assessments of amphibians.

Sabrina Kumschick,G. John Measey,Sarah J. Davies,Giovanni Vimercati,Tim M. Blackburn,Alexander D. Rebelo,Corey J. Thorp,Fred Kraus,F. Andre de Villiers,Mohlamatsane M. Mokhatla

doi:10.1002/ece3.2877

Abstract

The magnitude of impacts some alien species cause to native environments makes them targets for regulation and management. However, which species to target is not always clear, and comparisons of a wide variety of impacts are necessary. Impact scoring systems can aid management prioritization of alien species. For such tools to be objective, they need to be robust to assessor bias. Here, we assess the newly proposed Environmental Impact Classification for Alien Taxa (EICAT) used for amphibians and test how outcomes differ between assessors. Two independent assessments were made by Kraus (Annual Review of Ecology Evolution and Systematics, 46, 2015, 75‐97) and Kumschick et al. (Neobiota, 33, 2017, 53‐66), including independent literature searches for impact records. Most of the differences between these two classifications can be attributed to different literature search strategies used with only one‐third of the combined number of references shared between both studies. For the commonly assessed species, the classification of maximum impacts for most species is similar between assessors, but there are differences in the more detailed assessments. We clarify one specific issue resulting from different interpretations of EICAT, namely the practical interpretation and assigning of disease impacts in the absence of direct evidence of transmission from alien to native species. The differences between assessments outlined here cannot be attributed to features of the scheme. Reporting bias should be avoided by assessing all alien species rather than only the seemingly high‐impacting ones, which also improves the utility of the data for management and prioritization for future research. Furthermore, assessments of the same taxon by various assessors and a structured review process for assessments, as proposed by Hawkins et al. (Diversity and Distributions, 21, 2015, 1360), can ensure that biases can be avoided and all important literature is included.

Highlights

Species are being moved beyond the natural limits of their native ranges at a staggering rate
It was left unremarked whether species not assessed by Kraus fell into lower-impact categories, or were Data Deficient (DD) under the Environmental Impact Classification for Alien Taxa (EICAT) classification scheme (Hawkins et al, 2015)
We suggest that given the limited overlap between references included in the two studies (Figure 1), differences in interpreting the EICAT criteria are not the primary reason for differences in the classifications by Kraus and Kumschick et al The limited cases where differences could be attributed to different interpretation may have arisen because the extensive criteria and guidelines developed by Hawkins et al (2015) for implementing EICAT were not available to Kraus

Summary

Introduction

Species are being moved beyond the natural limits of their native ranges at a staggering rate. Impact scoring and classification systems are increasing in importance for invasion science and alien species management Such systems aim to make highly diverse data on impacts comparable between species, and allow patterns, trends, and potential predictors of impact to be analyzed quantitatively (e.g., Evans, Kumschick, Dyer, & Blackburn, 2014; Kumschick, Bacher, & Blackburn, 2013). They can play a crucial role in informing and guiding management decisions and creating lists of alien species with quantified impacts (e.g., Kumschick, Blackburn, & Richardson, 2016)

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