The geography of social vulnerability and wildfire occurrence (1984–2018) in the conterminous USA

Wildfire is increasing in frequency, extent, and severity in many parts of the USA. Considering the unequal burden of natural hazards on socially vulnerable populations, we ask here, how are characteristics of social vulnerability associated with wildfire occurrence nationwide, at different scales and across differing levels of wildland–urban interface development? To answer this question, we first identify all non-urban census tracts in the USA that have experienced a wildfire since 1984. Using 26 different measures of social vulnerability, we compare these tracts to non-urban census tracts that have not experienced a wildfire. In doing so, we identify notable social vulnerabilities in areas that have experienced wildfire, including higher unemployment, higher employment in extractive industries, higher percentage of people living in mobile homes, higher percentages of Native Americans, higher percentage of people with less than 12th grade education, and higher populations of people with special needs. Breaking our data into eight regions and comparing tracts with a high proportion of wildland–urban interface (WUI) to those with a low proportion of WUI, we find that these characteristics are generally consistent across regions of the USA and vary slightly between high WUI and low WUI tracts. Overall, we find a robust pattern of higher social vulnerability in areas with wildfire occurrence. Whereas previous studies about social vulnerability to wildfire focus on relationships with wildfire hazard potential or concentrate on a single region, this study fills a knowledge gap by examining the relationship between social vulnerability and wildfire occurrence nationwide.