Résumé
RCP scenarios predict increasing burned areas and more intense fire regimes in the coming decades, raising concerns about ecosystem resilience and essential services. Temperate region's areas previously considered low risk for wildfires are becoming increasingly flammable (Rodrigues et al. 2023) due to climate change. This trend is especially relevant in the Landes de Gascogne (LGA), dominated by maritime pine (Pinus pinaster Ait), where 30,000 ha of forest burned during the extreme wildfires of summer 2022. Current fire prediction models rely mainly on modern observational data but should be complemented by palaeoecological records to offer a long-term perspective. These reconstructions allow for a broader understanding of ecosystem responses to climate and anthropogenic forcing across longer timescales. However, the LGA's long-term fire and vegetation history remains poorly documented. Palaeoecological studies (Faure & Galop, 2011) indicate that before large-scale afforestation initiated by the 1857 law, the landscape was a mosaic of moorlands and mixed forests. This major vegetation shift likely altered ecosystem flammability, raising a key question: to what extent have historical changes in vegetation structure—particularly afforestation with flammable monocultures—increased the region's fire susceptibility? Addressing this knowledge gap, the ANR FIRE-LANDES project aims to reconstruct fire regimes in the region to assess the impact of land cover changes and improve flammability models. We analyzed macro-charcoal (>160 µm) and sedimentary records (XRF, magnetic susceptibility, density) from six laguna/peat bogs in the Hostens area (Gironde, France). The records reveal temporal variations in fire regimes. Preliminary findings suggest a possible shift: fires may have been more frequent before plantation development, while the post-afforestation period shows evidence of increased burned biomass. These trends could reflect growing landscape sensitivity to combined anthropogenic and climatic pressures. Upcoming palynological analyses will reconstruct plant composition and abundance to clarify how vegetation changes—shaped by natural and human factors—have influenced long-term fire dynamics. Combined with climate and fire data and forest modeling, this work will improve understanding of vegetation–fire–climate feedbacks and enhance flammability simulations to support fire management in the LGA.