Gastropods alien to South Africa cause severe environmental harm in their global alien ranges across habitats

Abstract

Alien gastropods have caused extensive harm to biodiversity and socioeconomic systems like agriculture and horticulture worldwide. For conservation and management purposes, information on impacts needs to be easily interpretable and comparable, and the factors that determine impacts understood. This study aimed to assess gastropods alien to South Africa to compare impact severity between species and understand how they vary between habitats and mechanisms. Furthermore, we explore the relationship between environmental and socioeconomic impacts, and both impact measures with life‐history traits. We used the Environmental Impact Classification for Alien Taxa (EICAT) and Socio‐Economic Impact Classification for Alien Taxa (SEICAT) to assess impacts of 34 gastropods alien to South Africa including evidence of impact from their entire alien range. We tested for correlations between environmental and socioeconomic impacts per species, and with fecundity and native latitude range using Kendall's tau tests. Kruskal–Wallis tests were used to compare impact magnitude among mechanisms and habitats, respectively. This study presents the first application of EICAT and SEICAT for invertebrates. There was no correlation between environmental impacts and socioeconomic impacts. Habitats did not differ regarding the severity of impacts recorded, but impacts via disease transmission were lower than other mechanisms. Neither fecundity nor native range latitude was correlated with impact magnitude. Despite gastropods being agricultural and horticultural pests globally, resilience of socioeconomic systems makes high impacts uncommon. Environmental systems may be vulnerable to gastropod impacts across habitats, having experienced multiple local extinctions of wetland island snail fauna. South Africa stands out as the only continental country that follows this trend. The knowledge gained on severity and nature of gastropod impacts is useful in risk assessment, which can aid conservation management. To make impact assessments more realistic, we suggest alternative ways of reporting impacts classified under EICAT and SEICAT.

Does origin determine environmental impacts? Not for bamboos

“…The EICAT scheme, which has been adopted by the IUCN, offers a standardised tool for producing impact assessments. To date, studies using EICAT have been published on birds (Evans, Kumschick, & Blackburn, ), amphibians (Kumschick, Measey, et al, ; Kumschick, Vimercati, et al, ), molluscs (Kesner & Kumschick, ), and some mammals (Hagen & Kumschick, ), but not yet for plants. In assessing the impacts of bamboos, we followed the guidelines of Hawkins et al () including: (1) intensive literature search of selected taxa of interest; (2) filtering of relevant literature pertaining to impacts; (3) scoring of the type and magnitude of impacts from the literature; and (4) evaluation of the data quality of the literature scored.…”

“…The EICAT scheme, which has been adopted by the IUCN, offers a standardised tool for producing impact assessments. To date, studies using EICAT have been published on birds (Evans, Kumschick, & Blackburn, 2016), amphibians , molluscs (Kesner & Kumschick, 2018), and some mammals (Hagen & Kumschick, 2018), but not yet for plants. In assessing the impacts of bamboos, we followed the We performed a systematic search of the peer-reviewed literature of our selected taxa using binomial species names on Google Scholar.…”

Reducing uncertainty in impact assessments for alien species

“…EICAT assessments have, to date, been published for alien birds (Evans et al 2016), amphibians (Kumschick et al 2017a), selected gastropods (Kesner and Kumschick 2018) and mammals (Hagen and Kumschick 2018), and bamboo species . Here we used the EICAT guidelines as published (Hawkins et al 2015), although these guidelines have subsequently been revised by the IUCN via an online consultation process (IUCN).…”

A four‐component classification of uncertainties in biological invasions: implications for management

“…, Kumschick et al. , Hagen and Kumschick , Kesner and Kumschick , Canavan et al. ), its applicability for guiding management in a marine context has been questioned due to differences in knowledge on invasion records (Ojaveer et al.…”

“…In addition, the difficulty of quantifying impact varies across environments. Although, unlike many other impact schemes, EICAT was designed to be practically applicable, and has been applied, across many taxa (Evans et al 2016, Kumschick et al 2017, Hagen and Kumschick 2018, Kesner and Kumschick 2018, Canavan et al 2019b), its applicability for guiding management in a marine context has been questioned due to differences in knowledge on invasion records (Ojaveer et al 2015). Despite a rebuttal to these critics (see the response by Blackburn et al 2015 as a comment to Ojaveer et al 2015), differences of knowledge between environments will indeed lead to differences in uncertainties on impact quantification, which also fall under the umbrella of natural variations (Box 1).…”