Housing arrangement and location increase wildfire risk

Background/Question/Methods

Surging wildfires across the globe are contributing to escalating residential losses and have major social, economic, and ecological consequences. The highest wildfire-related property loss in the US occurs in southern California, where nearly 1000 homes per year have been destroyed since 2000.  Wildfire risk reduction efforts have focused primarily on fuel reduction, and some to house characteristics and homeowner responsibility.  However, the extent to which land use planning could alleviate wildfire risk has been largely missing from the debate, despite the large number of homes being placed in the most hazardous parts of the landscape. We developed an extensive geographic dataset of structure locations, including more than 5500 that were destroyed or damaged by wildfire since 2001, and evaluated the relative role of housing arrangement, location, and environment in contributing to property loss in southern California. We also asked whether available fuel-based maps of fire hazard correspond to actual wildfire impacts and whether maps based on empirical data and an expanded set of explanatory variables could better predict property loss.

Results/Conclusions

The arrangement and location of structures strongly affected their susceptibility to wildfire, with property loss most likely at low to intermediate structure densities and in areas with a history of frequent fire.  Property loss was more likely to occur when structures were surrounded by wildland vegetation rather than urban areas, but was higher in herbaceous fuel types than in higher fuel-volume woody types that are typically considered as the most hazardous fuels.  Empirically based maps developed using housing pattern and location performed better in distinguishing hazardous from non-hazardous areas than maps based on fuel distribution patterns. The strong importance of housing arrangement and location indicate that land use planning may be a critical tool for reducing fire risk in the future.  However, mitigating future home loss will require plans that reliably delineate the most hazardous locations.