Characterizing pyroregions in south-eastern France

Abstract

Efficient fire policies may rely on good knowledge of the regional variations of fire activity and of fire drivers. South-eastern France comprises a range of pyroclimates, i.e. regions with contrasted fire activity (from fire-prone Mediterranean areas to mountain areas with few fires) and contrasted climate and fire weather. We tested if these pyroclimates also corresponded to specific hierarchy among environmental and human variables which drive fire activity. We used a 1973-2009 georeferenced fire database, and we computed how the landscape compartmentalization, the fuel coverage, the human density and the fire suppression capacity varied at a 2x2 km scale. The first pyroregion regroups two maritime fire-prone mountains (Corsica and the maritime Alps) in which there are no clear limitation to fire activity because of high human activity (i.e. numerous ignitions), no fuel limitation, and no weather limitation. The area is especially fire-prone because the suppression capacity is low to medium, and because the compartmented landscape hinders the activity of firemen. In the second pyroregion (fire-prone Mediterranean plains and foothills), fire activity is neither weather-limited (especially during dry summers) nor fuel-limited. It is clearly controlled by fire suppression which is especially active. In the third pyroregion (cool peri-Mediterranean mountains), fire activity remains low in spite of low fire suppression capacity and high landscape compartmentalization, because human activity is low and fire weather is unfavorable on average. We discuss to which extent the present fire suppression strategy (i.e. fast, hard-hitting initial attack on all fires) is adapted to these different pyroregions. In the fire-prone maritime mountains, it would be useful to increase the fire suppression forces. In fire-prone plains and foothills, the current plan of action is well suited, but large and destructive fire may persist due to the climate change and the fuel accumulation. In mountainous areas with low fire activity, fire suppression forces will likely have to adapt to the forecasted increase of fire activity.