Horizon scanning of potential invasive alien plant species and their distribution in Norway under a changing climate

Invasive alien plant species can cause considerable ecological, economic, and social impacts, and the number of impactful species will likely increase with globalisation and anthropogenic climate change. Preventing potentially invasive alien plant species from becoming introduced is the most cost-effective way to protect Norway's ecosystems from future invasions. We developed and applied a new method for horizon scanning to identify high-risk potentially invasive alien plant species that are not yet present in Norway but could be introduced and become naturalised and invasive in the future. Starting with 16 866 species known to be naturalised somewhere globally, we employed a simple and novel method for assessing the climate match of each species' known distribution to Norway's climate, then used economic and environmental impact data to narrow them down further. Of the species identified, we implemented species distribution models to predict the potential distribution of these high-risk species in Norway under both current and projected future (2060–2080) climate scenarios. A total of 265 plant species were identified as posing a high invasion risk to Norway. Under the current climate, their distributions were mostly limited to the southeast and coastal regions of Norway. However, under future climate change scenarios, the species' potential distribution increased significantly, with their ranges expanding northwards and further inland. Several invasion hotspots containing large numbers of species were identified close to urban areas such as Oslo, which is of particular concern as urban areas are amongst the most highly invaded environments globally. We strongly recommend that the import into Norway of species identified in this study be closely monitored and/or restricted to reduce the risk of invasions and to safeguard Norway's native biodiversity. We have also presented a novel and widely applicable method of horizon scanning with a particular focus on climate matching between species and the area of interest for both current and future climate scenarios.