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Effet du changement climatique sur l'évolution de l'aléa incendie de forêt en France métropolitaine au 21ème siècle

Abstract : Wildfires impacting French forests are currently concentrated in the South, especially in the Mediterranean and Aquitaine regions. Climate projections for the 21st century in France question the impact of climate change on wildfire hazard. We focus on two particular issues: the evolution of the fire danger and fire regime in regions already facing frequent wildfires today, and the potential extension of the risk to new regions in the future.Climate change effect was first determined using projections of an empirical fire danger index (FWI) under future climate, computed for five contrasted climatic models under two greenhouse gases emission scenarios. These projections highlight a very strong increase in fire danger levels in the areas already facing wildfires, especially in the Mediterranean, with a very good agreement between climate models. The range of the increase in the North and the West, though existing, is more challenging to quantify, because of climate model uncertainties.This first approach was limited by the ability of FWI to represent fire activity. Therefore, we developed a probabilistic model for fire activity, aiming at projecting fire numbers and burnt areas under future climate. The approach considers that fires result from underlying random processes that determine the occurrence and the fire size based on the FWI and various spatiotemporal factors. The model was fitted following a Bayesian approach using the Promethee database, which records fire observations in the Mediterranean area. Model projections under historical and future conditions demonstrated that FWI projections underestimated projected fire activity increases, mainly due to the non-linearity of the fire-climate relation. Thus, fire danger increases projected in summer in the Mediterranean in 2080 (pessimistic scenario) are considerably lower (25 to 59%) than those for burnt areas (48 to 202%).This approach does not apply to regions where wildfires are currently sparse, and unreliably recorded, especially in Northern France. Yet we extrapolated the model, established over the Mediterranean area, to the rest of Southern France where data were sufficient. Among the difficulties encountered while extrapolating to the national scale, the variation of fuel structure is a critical issue. It was not included in the projections, but its implications are discussed.
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https://hal.inrae.fr/tel-02789674
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Submitted on : Friday, December 11, 2020 - 3:26:08 PM
Last modification on : Wednesday, March 17, 2021 - 12:06:03 PM
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  • HAL Id : tel-02789674, version 1
  • PRODINRA : 495320

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Hélène Fargeon. Effet du changement climatique sur l'évolution de l'aléa incendie de forêt en France métropolitaine au 21ème siècle. Sylviculture, foresterie. Institut agronomique, vétérinaire et forestier de France, 2019. Français. ⟨NNT : 2019IAVF0025⟩. ⟨tel-02789674⟩

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