Emerging Invasion Risks of Non-Native Urban Trees in Continental Europe Under a Changing Climate

Urban green areas contain numerous non-native tree species that may escape from cultivation and potentially become invasive. Climate change is expected to exacerbate this risk by creating favourable conditions for species that are currently climatically restricted. Here, we provide a comprehensive risk screening of 34 non-native urban tree species in continental Europe under current and projected future climate scenarios using the Terrestrial Plant Species Invasiveness Screening Kit (TPS-ISK). Under current conditions, 10 species (29.4%) were categorized as high risk, 23 (67.6%) as medium risk, and one (2.9%) as low risk. Under the projected climate change, 11 species were classified as high risk, including seven categorized as very high risk. Ailanthus altissima, Diospyros virginiana, and Quercus rubra consistently ranked among the highest-risk species, while Acer tataricum subsp. ginnala, Koelreuteria paniculata, Magnolia kobus, Phellodendron amurense, Pseudotsuga menziesii, and Robinia pseudoacacia showed an increased invasion potential under future climate conditions. These findings indicate that climate change may facilitate the establishment and spread of several currently cultivated urban tree species. Our study provides the first comprehensive TPS-ISK screening of non-native urban trees for mainland Europe and identifies priority species for early detection, monitoring, and management.