Early season wildfires pose the highest threat to buildings and people in Sweden

Wildfire damage to the built environment and people is typically understood through case studies of high-impact events, or from incident databases where the smallest wildfires are not always accounted for. We analyzed an exhaustive database of 131 040 reported fire service wildfire dispatches (1996–2022) in Sweden. There were on average per year 126 wildfires that threatened buildings, 22 that ignited buildings, 17.6 that injured people and 1.1 that led to a fatality. The analysis showed that building ignitions, human injuries as well as fatalities in this region were caused primarily by relatively small fires (90th percentile <10 ha) and that they occurred predominantly in the spring season. Untended grass litter near buildings constituted a much higher fire threat to the built environment than did forest vegetation, even when fire danger was relatively low. The source of the ignitions was 99 % anthropogenic and mostly connected with intentional fire use such as burning grass litter or garden debris. Our study highlights the need for improved fire statistics to cover the full extent of threats to life and property from wildfires. Further, it suggests that the potential for harm reduction through improved wildfire knowledge among the rural population should be large.