Evolution of the bark beetle crisis in Norway spruce forests: A spatial and temporal remote sensing analysis in Belgium and North-eastern France

In 2022, Europe emerged from eight of the hottest years on record, leading to significant spruce mortality across Europe. The particularly dry weather conditions of 2018 triggered an outbreak of bark beetles (Ips typographus), causing the loss of thousands of hectares of Norway spruce (Picea abies) stands, including in southern Belgium and north-eastern France.

A methodology for detecting the health status of spruce was developed based on dense time series of satellite imagery (Sentinel-2). The time series of satellite images allowed the modelling of the spectral response of healthy spruce forests over the seasons: a decrease in photosynthetic activity of the forest canopy causes deviations from this normal seasonal vegetation index trajectory. These anomalies are caused by a bark beetle attack and are detected automatically. The method leads in the production of annual spruce health map of southern Belgium and north-eastern France. The resulting map are used to assess the damage caused by bark beetle and to study the relation between the dieback and environmental conditions.

Lasted six years (2017-2022), bark beetle has destroyed 12.2 % (23,674 ha) of the spruce area in southern Belgium and north-eastern France. This study area is composed of three bioclimatic areas: Plains, Ardenne and Vosges, which have not been equally affected by bark beetle attacks. The plains were the most affected, with 50% of spruce forests destroyed, followed by the Ardenne, which lost 11.3% of its spruce stands. The Vosges was the least affected region, with 5.6% of spruce stands lost.