Integrating climate and land‐use change scenarios in modelling the future spread of invasive squirrels in Italy

Mirko Di Febbraro,Danilo Russo,Sandro Bertolino,Mattia Menchetti,Emiliano Mori,Adriano Martinoli,Leonardo Ancillotto,Damiano G Preatoni,Federica Roscioni,Anna Loy,Gaetano Aloise,Núria Roura‐Pascual

doi:10.1111/ddi.12890

Abstract

AbstractAimThe establishment and spread of invasive alien species may be influenced by several mutually interacting factors, whose understanding is paramount to develop effective biosecurity policies. However, studies focused on modelling spatially explicit patterns of future invasion risk have so far focused on species response to climate change impacts, while land‐use change has been neglected. We investigated how the interplay between climate and land‐use change could affect the future potential distribution and dispersal corridors of four alien squirrels introduced to Europe (Sciurus carolinensis, Callosciurus finlaysonii, Callosciurus erythraeus and Eutamias sibiricus).Location and MethodsOur study was conducted in Italy. We used Species Distribution Models and circuit theory methods to test whether future scenarios based only on climate change predict a different effect on range and connectivity of alien squirrel populations, compared to scenarios that include both climate and land‐use changes.ResultsScenarios based only on climate change predicted a range increase and a high geographic stability (>50%) for most species, with different, yet limited, effects on connectivity corridors. Conversely, scenarios based on both climate and land‐use change showed a loss in range extent and a low geographic stability (<50%) of both range and dispersal corridors for most species.Main conclusionsScenarios considering both climate and land‐use change provide predictions on invasion risk that overturn those including only climate change. The effect of global warming alone would lead to a considerable range expansion of all species. Conversely, when land‐use change is added, a potential loss in suitable habitat and dispersal corridors is predicted for alien squirrels, hence limiting their range expansion. We recommend using multiple drivers in models to obtain reliable predictions for implementing biosecurity policies related to invasive alien species.

Highlights

Species introduction is an ever‐growing process (Bellard, Rysman, Leroy, Claud, & Mace, 2017) that poses major threats to global bio‐ diversity (Mack et al, 2000; Nentwig, Bacher, Kumschick, Pyšek, & Vilà, 2018)
We predicted (a) a species‐ specific response to interacting climate and land‐use change, with some species favoured and others limited by the increase in tem‐ perature (IPCC, 2007) and the reduction of forest and semi‐natural areas (Verburg et al, 2006), and (b) that effects of interacting climate and land‐use change may overturn predictions conducted under cli‐ mate change only
We considered the scenarios by the fourth Intergovernmental Panel on Climate Change (IPCC) assessment instead of the most up‐to‐dated fifth one (IPCC, 2013), since these lastly released scenarios are available only for climate change, without any analogous for land‐use change

Summary

| INTRODUCTION

Species introduction is an ever‐growing process (Bellard, Rysman, Leroy, Claud, & Mace, 2017) that poses major threats to global bio‐ diversity (Mack et al, 2000; Nentwig, Bacher, Kumschick, Pyšek, & Vilà, 2018). Most European populations of introduced squirrels are expanding their distribution range (Bertolino, Cordero di Montezemolo, Preatoni, Wauters, & Martinoli, 2014; Dozières et al, 2015; Goldstein, Butler, & Lawton, 2016; Gurnell, Lurz, & Bertoldi, 2014), offering a suitable model to test the invasion risk they pose considering the effects of both cli‐ mate and land‐use change. Specific objectives of this study were the following: (a) to assess the current potential distribution and dispersal corri‐ dors for alien squirrels in Italy, considering both climatic and land‐ use variables, (b) to predict the potential distribution and dispersal corridors of these species under future scenarios based on climate change only and on pooled climate and land‐use change, and (c) to quantify differences among species response to both of the consid‐ ered global change drivers. We predicted (a) a species‐ specific response to interacting climate and land‐use change, with some species favoured and others limited by the increase in tem‐ perature (IPCC, 2007) and the reduction of forest and semi‐natural areas (Verburg et al, 2006), and (b) that effects of interacting climate and land‐use change may overturn predictions conducted under cli‐ mate change only

| METHODS

Findings

| DISCUSSION