Potential of wildland fire hazard in France towards 2100: a bioclimatic approach

IPCC reports identified a potential general increase of wildland fires according to climate change scenarios in different ecological situations for 2050 and 2100. In France, more than 6.800 municipalities are exposed to wildland fire, which represents 19% of the amount of municipalities. According to the official data on municipalities exposed to such hazard, France has seen an increase of 900 municipalities between 2010 and 2019, from 5900 to 6800, which represent a progression of 13% of municipalities exposed to wildland fires.
We propose a bioclimatic approach in order to assess the potential spread of such hazard. The model is based on the distribution of suitable areas for bio-indicators of wildland fire. These bio-indicators com from bibliographic review and field observations. Then, we define a group of plants that gathers 154 trees (like Pinus halepensis, Arbutus unedo, Acacia dealbata etc.), shrubs (like Lavandula stoechas, Pistacia lentiscus, Cistus albidus etc.) and herbs (like Brachypodium ramosum, Psoralea bituminosa, Aphyllanthes monspelliensis etc.) that are very often exposed to wildland fire. In that way, it is possible to consider these species as indicators of potential risk of wildland fire in the territories where they are observed or where they should grow.
We also characterized the ecological niche of these 154 taxa by using climatic data coming from WorldClim model (with a spatial resolution of around 1km), soils types and pH levels coming from the European Soils Bureau Database.
We estimated the average probability to find suitable areas for these bio-indicators for the current situation and for 2050 and 2100 by using IPCC RCP6.0 scenarios. We also selected the plots where the probability of suitable areas for wildland fire indicators is equal or greater to 0.5, in order to have at least one chance out of two to find territories exposed to such event.
In order to validate our bioclimatic model, we overlap the estimate for the current situation with the layer of municipalities that have declared at least one wildfire episode in France since 40 years. We identified that 84% of the current municipalities at risk gather significant probabilities of suitable areas for bio-indicators of wildland fire. Then we can consider that our model has an average of 16% of uncertainty.
 
Applied for the current and future situations, we can estimate the amount of potential vulnerable municipalities taking into account the level of uncertainty:

Current situation

17.019

48.7 %

The evolution of the most suitable areas for 154 indicators of wildland fire risk shows a potential spread in the whole territory.

Current to 2050
Estimated vulnerability of the territory to wildland fire for 2050, RCP6.0 scenario. 
 

2050 RCP6.0

26.107

74.7 %

2050 to 2100 
​Estimated vulnerability of the territory to wildland fire for 2100, RCP6.0 scenario. 
 

2100 RCP6.0

26.781

76.6 %

These results underline a potential increase of wildland fire risk spread in the French territory due to the potential spread of suitable area for plants that are often involved in such hazard. This trend would be located in the northern part of the territory and in highest altitudes than the current period.
 

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