Driving factors of fire density can spatially vary at the local scale in south-eastern France

Abstract

South-eastern France is the most wildfire-prone region of the country. To identify the main driving factors in fire density (defined as the number of fires per hectare) at the local scale (clusters of communities that are homogeneous in terms of land cover, climate and wildland–urban interface (WUI)) and to assess their spatial variation at this scale, fire density was investigated in the département Bouches du Rhône using geo-referenced fire ignitions. To assess relationships between fire density and explanatory factors, statistical analyses and spatial evaluation were performed on each cluster taking into account climatic conditions, topography, land cover, WUI (defined as a buffer of 100 m around housing located less than 200 m from natural vegetation), minor road and population densities, with fire density as the dependent variable. High fire density was mainly related to high proportion of WUI in the study area. The proportion of natural vegetation and steep slope were also among the most important drivers of fire density. Depending on the cluster, some biophysical factors can in turn enhance or mitigate fire density but coolest and wettest climate conditions related to highest elevations as well as low housing density always mitigated fire density. This work showed that, at the local scale, the identification of factors driving fire density could improve fire prevention because this would enable the factors to be better targeted.