Comment on nhess-2021-174

Abstract

Forest fires burn an average of about 440,000 ha each year in southern Europe. These fires cause numerous casualties and deaths and destroy houses and other infrastructures. In order to elaborate suitable fire-fighting strategies, complex interactions between human and environmental factors must be taken into account. In this study, we investigated the spatio-temporal evolution in burned area over a 50-year period (1970–2019) and its interactions between topography (slope inclination and aspect) and vegetation type in south-eastern France by exploiting Geographic Information System databases. Burned area decreased sharply after 1994, with the advent of the new fire suppression policy which focused on rapid extinction of fires in their early phase. The geographic distribution of burned area has also changed in the last 25 years, mainly in regions where large fires occurred (Var department). In other parts, even though forest fires are still frequent and occur in the same geographic locations, the total extent of the burned area is significantly reduced. Slope orientation presents an increasingly important role every decade, S-facing slopes have the greatest burned areas and increase their proportion each decade, while the opposite is observed for N-facing and W-facing ones. Fire increasingly favors low and intermediate slopes after the sharp decrease of burned area in 1990. The largest part of the BA is strongly associated with the location of sclerophyllous vegetation clusters, which exhibit high fire proneness while simultaneously expanding the region. On the contrary, natural grassland numbers decline through time as the proportion of area burned increases.