Isolating the Primary Drivers of Fire Risk to Structures in WUI regions in California

The destructive impacts of Wildland-Urban Interface (WUI) fires on people, property and the environment have dramatically increased, especially in California. Critical factors influencing structure protection during wildfires, including home hardening (e.g., vents, siding, roof, eaves, window, construction year), defensible space (vegetation and surrounding features), exposure to flames and embers, and structure separation are well known but their interrelated impacts are not quantified. Here, we find that structure separation and exposure significantly influence the probability of loss, underscoring the role of large conflagrations in driving widespread destruction. Machine learning models combined with previously unavailable exposure data enhance the predictive accuracy of structure loss up to 82%. Home hardening and defensible space, especially closest to the home, are still vital and effective mitigation measures, cutting hypothetical structures losses by 52%. Our results offer data-driven actionable insights for prioritizing mitigation strategies to protect vulnerable communities and structures in the WUI.