Global risk of invasion by terrestrial vertebrates under contrasting SSP scenarios

Abstract

The introduction of alien species is among the main causes of biodiversity decline in the Anthropocene. We generated predictions of how climate and land-use change may modulate invasions by exotic species in the coming decades. We used the InSiGHTS modelling framework, which projects global species distributions through bioclimatic envelopes and habitat suitability models (HSMs), to predict the introduction and invasion risk of 333 allochthonous mammals and amphibians in three scenarios of global change: Representative Concentration Pathway (RCP) 2.6 - Shared Socioeconomic Pathway (SSP) 1; RCP 6.0 – SSP 3; and RCP 8.5 – SSP 5. The bioclimatic envelopes were developed using biomod2 with specific settings for alien species, mediated bioclimatic layers from 10 Coupled Model Intercomparison Project Phase 5 (CMIP5) global circulation models and alien species distributions from recent databases. The HSMs were based on the Land-Use Harmonization dataset (LUH2). We defined the invasion risk as the species InSiGHTS Index, the mean proportion of suitable habitat for introduced species in each 0.5 degree cell, inside the exotic range plus the area reachable through natural species dispersal, and the introduction risk as the InSiGHTS Index outside the native range. Global invasion risk by terrestrial vertebrates is predicted to increase in all the scenarios. Invasion hotsposts were located in every continent except Antarctica and noticeably overlapped with biodiversity hotspots. The global introduction risk of mammals was positively correlated with climate change mitigation, with higher risk under RCP 2.6 – SSP 1 than in the other scenarios, and decreasing risk under RCP 8.5 – SSP 5 particularly at higher latitudes. For amphibians, global introduction risk increased at higher latitudes and decreased at lower latitudes in all the scenarios. Our prediction quantifies how mammals and amphibian invasion front will move in response to different global change scenarios, providing crucial information to prevent or mitigate their possible impact on biodiversity worldwide.