Historical range of wildfire regime in black pine forests outside actual target of public policies.

Abstract

With global changes, disturbances including wildfires are expected to change, with consequences for ecosystems. The chief fire control policy of "fire suppression" aims to limit their numbers and areas. Mediterranean forest ecosystems have coevolved with fires, despite millennia of land use. Biota, climate and humans have long interacted to establish fire regimes in these socio-ecosystems. Sustainable fire stewardship should reconcile the protection of resources and people, while being realistic about the ability to limit all fires and preserving the ecological functions they provided. The past fire regime must be known and compared to the suppression objectives. We hypothesised that fires were infrequent and smaller, but with global changes in recent decades, they would be more frequent, and the burned areas would have increased. We addressed the fire regime (intervals, areas, season) in Corsican black pine forests, western Mediterranean, by reconstructing fire regime from geolocated fire scars dated by dendrochronology. The results show that fire intervals are currently long (40 years), whereas they have fluctuated several times over the past 300 years. Intervals were shorter (10 years) in 1719-1848 and 1923-1970. Burned areas also fluctuated, with larger areas occurring in 1849-1916. Fire seasons have not varied for at least 300 years. We highlighted a non-stochastic regime of fire intervals uncorrelated with burned areas. The fire regime targeted by public policies is not aligned with the historical regimes. We argue for new policies to prevent large fires, which could be more destructive than the frequent and low intensity observed over centuries.