Assessing disturbance risks of the European spruce bark beetle under climate change: a review of model approaches and future perspectives

Abstract Mass outbreaks of the European spruce bark beetle ( Ips typographus ) have increased in both frequency and severity over the last two decades, with major ecological and economic consequences for European forests. To maintain the functionality of forests for future generations and mitigate climate change effects, comprehensive and operational bark beetle risk assessment is key for proactive and reactive forest management. Here, we review the diverse approaches that have been applied to assess the risk of I. typographus disturbances over the past two decades. We outline the biological and phenological characteristics of I. typographus important for its management, and identify the variables used in the models. We categorise the models into five groups: phenology models, dispersal models, disturbance driver models, ecosystem and management models, as well as frameworks and combined approaches, and evaluate the risk components considered. Furthermore, recent developments, challenges, and future perspectives towards operational systems that could bridge science and practice are highlighted. We expect that technological advances will soon enable the development of comprehensive high-resolution, near real-time I. typographus risk assessment systems at national or transnational scales that can cope with the high degree of uncertainty regarding time, location, and extent of bark beetle disturbances, and thus may also act as early warning systems. We therefore encourage fellow scientists and institutions to seize the opportunity to develop practice-oriented applications that will support forest management, in order to prevent or mitigate I. typographus disturbances, adapt European forests to climate change, and maintain and secure important ecosystem services for the future.