Fire Risk Assessment In The Wildland-Urban Interface Of Ibero-Atlantic Heterogeneous Landscapes

Forest fires cause major environmental and socio-economic impacts, with the greatest risk for people occurring in the wildland-urban interface (WUI). In Ibero-Atlantic landscapes, where dispersed settlements are expanding into wildlands and vegetation is encroaching on populated areas, both the frequency and severity of WUI fires are rising sharply. The objective of this study was to develop a new methodological approach to assess fire risk in the WUI of Ibero-Atlantic heterogeneous landscapes under the assumption that fire impacts on population entities may occur by direct or indirect exposure to different types of vegetation. Based on landscape configuration analysis, expert knowledge of fire behaviour across vegetation types and on-site observations of fire impact on buildings and other infrastructures, we developed a multi-ring system around different types of population entities to characterize pre-fire vegetation patterns and fire severity across zones of influence (rings) within the WUI. The relationships between vegetation and severity (estimated with the Relativized Burn Ratio –RBR– spectral index derived from Sentinel-2 satellite imagery) were evaluated using multivariate linear regression models, with a backward stepwise procedure, at two levels: WUI and ring. This framework was tested in the large forest fire of Foyedo (Asturias, NW Spain) that affected more than 10,000 ha in the spring of 2023. Vegetation changed across the WUI, reflecting a land-use gradient from more managed vegetation near settlements to less managed and more natural types in outer zones, with fire severity increasing outward. The main drivers of fire severity at WUI level were vegetation type and vertical complexity. At ring level, the pattern was similar, with the percentage of heathlands and shrublands being the best predictor of fire severity in all rings. In the outermost ring, pine and eucalyptus plantations were also directly related to fire severity. Our findings underscore the need to develop spatially complex analytical frameworks accounting for different exposures across the WUI in order to guide effective vegetation management for forest fire prevention in the Atlantic landscapes of the Iberian Peninsula.