Delineating protection forests at the regional scale: a decision-support framework for forest planning and management

Protection Forests (PFs) play a fundamental role in mitigating natural hazards by reducing their impacts on people, infrastructure, and other exposed assets. Despite their importance for forest planning and risk management, the regional delineation of PFs remains challenging because the protective role of forests varies among hazard types and available hazard assessments are often heterogeneous in terms of methodology, spatial resolution, and data quality. Moreover, their protective function can be distinguished into two complementary forms: indirect protection, which reduces the likelihood and magnitude of hazardous processes irrespective of the presence of exposed elements, and direct protection, which provides a site-specific protective function by being located between hazard source areas and exposed elements. The present study proposes a flexible, spatially explicit framework for delineating PFs through the integration of geospatial information layers describing natural hazards, exposed elements, topographic connectivity, and forest cover. The framework is independent of the specific hazard-assessment methodology adopted because all hazard information is standardized into a common indicator, allowing the integration of different modelling approaches within a unified analysis. Moreover, the Management Priority Index (MPI), a spatially explicit metric, is introduced to prioritize monitoring and silvicultural planning according to the protective importance of individual forest stands. The methodology was applied to the Lombardy Region (northern Italy), covering 23863 km², of which approximately 6758 km² are forested. The results indicate that PFs occupy approximately 1770 km², corresponding to about 26% of the regional forest area, of which 970 km² are classified as Direct Protection Forests (14%), i.e., forests that provide a protective function between a hazardous process and one or more exposed elements. Landslide-related protection represents the dominant protective function, whereas forests protecting against snow avalanches and debris flows are more spatially restricted. The proposed methodology provides a consistent and transferable decision-support framework for regional forest planning by distinguishing the forest suitability to perform a direct protective function from their actual effectiveness, which requires detailed process-based analyses at the local scale. Because the framework can progressively incorporate improved susceptibility/hazard models, forest inventories, and exposure datasets, it provides a robust basis for supporting adaptive forest management under increasing natural hazard pressure.