High wildfire damage in interface communities in California

Globally, and in the US, wildfires pose increasing risk to people and their homes. Wildfire management assumes that buildings burn primarily in the wildland-urban interface (WUI), where homes are either ignited directly (especially in intermix WUI areas, where houses and wildland fuels intermingle), or via firebrands, the main threat to buildings in the interface WUI (areas with minimal wildland fuel, yet close to dense wildland vegetation). However, even urban areas can succumb to wildfires. We examined where wildfire damages occur among urban, rural and WUI (intermix and interface) areas for approximately three decades in California (1985-2013). We found that interface WUI contained 50% of buildings destroyed by wildfire, whereas intermix WUI contained only 32%. The proportion of buildings destroyed by fires among classes was similar, though highest in interface WUI areas (15.6%). Our results demonstrate that the interface WUI is where most buildings were destroyed in California, despite less wildland fuel. Continued advancement of models, mitigation and regulations tailored for the interface WUI, both for California and elsewhere, will complement the prior focus on the intermix WUI.