Modelling the potential range of Agrilus planipennis in Europe according to current and future climate conditions

Agrilus planipennis, the emerald ash borer, is a species native to East Asia that was accidentally introduced to North America and Eastern Europe. In North America, it is responsible for tremendous damage. In Europe, its range has quickly expanded from the east where it was introduced in 2003, and it threatens the species of the genus Fraxinus. We developed an ensemble modelling approach to model the potential range of A. planipennis according to current climate conditions and four scenarios of climate change: SSP1–2.6, SSP2–4.5, SSP3–7.0 SSP5–8.5 in the period 2041–2060. We used three algorithms; random forest, boosted regression trees and Bayesian additive regression trees with occurrence data from both native and invaded ranges. The results indicate that most of the European continent is climatically suitable for A. planipennis. In Western Europe, the northern limit of the range is located in the British Isles and southern Scandinavia. The projection of the models according to estimates of future climate conditions shows that climate suitability would mostly remain unchanged in 2041–2060. During that period, the potential range is expected to slightly shrink in the south, around the Mediterranean Basin, and expand at its northern limit. Our results confirm that A. planipennis is, and will remain, a major threat to forest and ornamental ash tree health across Europe.