Barriers to globally invasive species are weakening across the Antarctic

Aim: Biological invasions are a substantial threat to Antarctic biodiversity and a priority conservation policy focus for Antarctic Treaty Parties and the sovereign states of surrounding islands. Key to their strategies is prevention, including assessment of establishment risk for alien species. Despite establishment of some of the worst globally invasive species across the Antarctic region, assessments of establishment potential of these species are non-existent. Here, we address this deficit and determine whether these invasive species constitute a significant conservation threat to the broader Antarctic region both now and in response to future regional climate change. Location: Antarctica and the Southern Ocean islands (45°–90° S). Methods: We used ensemble species distribution models to assess the current and future climate suitability of the Antarctic region for 69 of the worst globally invasive species and 24 insect and plant species that have already established somewhere in the region. Results: The Antarctic continent is unsuitable for all of the worst globally invasive species under current conditions, but areas of the Antarctic Peninsula are predicted to become climatically suitable for up to six globally invasive species within the next century. By contrast, all Southern Ocean islands are presently climatically suitable for additional non-native species, with the threat increasing in the future. Main conclusions: Our findings demonstrate that climate, which is often cited as a key barrier to alien species establishment, may afford some protection to continental Antarctica, but that this protection is not currently extended to the Southern Ocean islands. Furthermore, existing climatic barriers to alien species establishment will weaken as warming continues across the region. This not only illustrates the value of applying distribution modelling methods to this largely ice-covered region, but demonstrates how these methods can be used to inform targeted surveillance of introduction pathways and sites that have the highest risk of establishment of invasive alien species.