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AbstractThis work aims at assessing, in the French Mediterranean area, the spatio‐temporal trends of fires, including their causes, at fine scale (communities), comparing different periods between 1993 and 2017. These trends were compared to those of land‐cover and wildland‐urban interface (WUI) which were coupled with a spatial analysis of the ignitions in order to highlight the main drivers and preferential areas. Fire density was highly variable among communities, hotspots being located mostly close to big cities but spatially varying in time in contrast to fire occurrence and burned area. A decrease in the unknown cause proportion and a variation of the cause frequency were highlighted among periods, criminal fires being the most frequent and deleterious, especially before 2009, as well as those due to negligence during private activities, mostly after 2009. Land cover classes significantly varied among periods, artificialized and natural areas presenting a reversed trend compared with agricultural areas. Natural areas were the most affected by ignitions (60%), regardless of the period; this trend is slowly decreasing. WUI represented ∼30% of the study area, the different types varying spatially (denser clustered types mostly located in the South‐East) and showed an increase over time, especially for both clustered types but with high variability among communities. Half of the ignitions occurred in WUI, with "very dense clustered" and "scattered" types being the most affected, especially in 2009. Better understanding the spatio‐temporal evolution of fires and of their causes should allow refining the fire policies in terms of awareness raising, firefighting means, and land management.

Abstract. In the French Mediterranean, large fires have significant socioeconomic and
environmental impacts. We used a long-term georeferenced fire time series
(1958–2017) to analyze both spatial and temporal distributions of large
fires (LFs; ≥100 ha). The region was impacted in some locations up to
six
times by recurrent LFs and 21 % of the total area burned by LFs occurred on
a surface that previously burned in the past, with potential impact on
forest resilience. We found contrasting patterns between the east and the
west of the study area, the former experiencing fewer LFs but of a larger
extent compared to the latter, with an average time of occurrence between LFs
exceeding 4000 ha < 7 years mostly in the eastern coastal area and
> 50 years in the west. This longitudinal gradient in LF return
level contrasts with what we would expect from mean fire weather conditions
strongly decreasing eastwards during the fire season but is consistent with
larger fuel cover in the east, highlighting the strong role of fuel
continuity in fire spread. Additionally, our analysis confirms the sharp
decrease in both LF frequency and burned area in the early 1990s, due to the
efficiency of fire suppression and prevention reinforced at that time,
thereby weakening the functional climate–fire relationship across the
region.

Abstract. Large wildfires across parts of France can cause devastating damage which
puts lives, infrastructure, and the natural ecosystem at risk. In the climate
change context, it is essential to better understand how these large
wildfires relate to weather and climate and how they might change in a warmer
world. Such projections rely on the development of a robust modeling
framework linking large wildfires to present-day atmospheric variability.
Drawing from a MODIS product and a gridded meteorological dataset, we derived
a suite of biophysical and fire danger indices and developed generalized
linear models simulating the probability of large wildfires (>100 ha) at
8 km spatial and daily temporal resolutions across the entire country over
the last two decades. The models were able to reproduce large-wildfire
activity across a range of spatial and temporal scales. Different
sensitivities to weather and climate were detected across different
environmental regions. Long-term drought was found to be a significant
predictor of large wildfires in flammability-limited systems such as the
Alpine and southwestern regions. In the Mediterranean, large wildfires were
found to be associated with both short-term fire weather conditions and
longer-term soil moisture deficits, collectively facilitating the occurrence
of large wildfires. Simulated probabilities on days with large wildfires were
on average 2–3 times higher than normal with respect to the mean seasonal
cycle, highlighting the key role of atmospheric variability in wildfire
spread. The model has wide applications, including improving our
understanding of the drivers of large wildfires over the historical period
and providing a basis on which to estimate future changes to large wildfires
from climate scenarios.