Ecosystem services at risk from disturbances in European forests

In Europe, forest ecosystems are facing increasing disturbances such as wildfires, insect-outbreaks and windthrows, and the impacts of such events are likely to increase under ongoing climate change. Increasing disturbances can challenge forest resilience and vulnerability, resulting in higher risks of losing forest ecosystem services. However, quantifying risk across large spatial scales such as Europe is still a fundamental research challenge, since it requires understanding and evaluating the main elements of risk. In this study, we aim to assess the risk of losing forest ecosystem services due to the most common forest disturbances in Europe (wildfires, windthrows and insect-outbreaks – mainly spruce bark beetle). To do so, we mapped the risk components across European forests: exposed values, hazard magnitude, susceptibility and lack of adaptive capacity. Exposed values were quantified in terms of the ecosystem services provided by forests (i.e., timber volume, carbon stocks, soil erosion control, protection against gravitational hazards, and outdoor recreation), that could be lost if the disturbance occurs. The magnitude of the hazard and its probability distribution was quantified using integrative hazard indices (e.g., the Fire Weather Index for wildfires). Susceptibility was based on characteristics that modulate the immediate impacts of the hazard, such as tree height for windthrows or forest continuity for spruce bark beetle. Lack of adaptive capacity was assessed using historical post-disturbance canopy recovery of forests. We integrated and harmonized different indicators, datasets and maps for each risk component and disturbance. Then, we combined the risk components to obtain a risk map for each ecosystem service and disturbance considered, which allowed us to identify the areas with the highest risk. This study is the first ecosystem services’ risk assessment of European forests, which provides critical spatial information for these forests. Given that climate change could amplify forest disturbances, the results of this study could be used to anticipate and adapt to future conditions, as well as to guide efficient forest management.