Remote Sensing Perspective on Integrated Bark Beetle Vulnerability Assessment

Threats to European forests caused by pests are increasing due to climate change and its associated effects. The European spruce bark beetle (Ips typographus) is a prominent example, benefitting from warmer and drier conditions and well-known to cause wide-spread calamities in spruce-dominated forests in Northern and Central Europe. Current remote sensing approaches, built upon changes in spectral signatures, do currently not provide satisfactory results on the early detection of infestation stages to contain outbreaks. Thus, visual terrestrial surveys are required, which are highly time-consuming and hardly feasible for most foresters due to spatio-temporal constraints. Additional tools, such as trap-based monitoring, aim to reduce the required effort in the field by prioritisation, but cannot deliver information over wide-spread areas. Therefore, this work provides an outlook on an explorative approach to analyse factors which influence the number of bark beetle monitoring trap catches, a proxy for the local bark beetle population, from a remote sensing perspective. It aims to further deduce factors that mediate forest vulnerability to bark beetle infestation and thus provide further decision ground for a more efficient management. To achieve this, we combine weekly data from pheromone traps that are part of the bark beetle monitoring in Bavaria (southwestern Germany) with open-source remote sensing data, including LiDAR, RGB-Imagery as well as meteorological measurements. The calculated products include the detection and quantification of forest edge effects, structural forest heterogeneity (vertical and horizontal), proportion of Norway spruce (Picea abies) and species composition. This will help to identify and quantify the impact of forest and landscape features on Ips typographus populations. In addition, we aim to analyse the effect of different spatial resolutions as well as the temporal dimension. Ultimately, together with other relevant information such as current bark beetle swarming activity, weather, as well as soil and site conditions, our results will contribute to a more holistic and precise assessment of forests’ vulnerability to bark beetles in the future.