Six different regions across France

With respect to large wildfires, France has been divided into six environmental units (28):

• The northern region. This is the less fire-prone region, corresponding to a temperate climate in which average summer temperatures are relatively low. This region covers more than half of France but contributes only 1.9% to national burned area during 2001 to 2016.
• The Alpine region, dominated by conifer forests at high elevation and broadleaf forest at low elevation, and contributing 2.3% to national burned area during 2001 to 2016.
• The western region, corresponding to the southern Atlantic climate characterized by warm and dry summers coupled with mild and humid winters, and contributing 5.4% to national burned area during 2001 to 2016.
• The Mediterranean mountains, which combine the influence of both Mediterranean and mountain climates, and contribute 34.8% to national burned area during 2001 to 2016.
• The Mediterranean north, containing holm oak and cork-oak-dominated vegetation and contributing 25.7% to national burned area during 2001 to 2016.
• The Mediterranean south, a low-elevation area spanning the Rhône delta that contributes 7.1% to national burned area during 2001 to 2016.

The high percentage for the Mediterranean north illustrates that large wildfires occur when multiple conditions are gathered, namely high winds, dry fuel and low soil moisture levels. In flammability-limited systems such as the Alpine and southwestern regions, long-term drought is a significant predictor of large wildfires (28).

Vulnerabilities

In the summer 2003 heat wave in France, the costs of fighting forest fires for the Ministry of Interior increased from EUR 83 million in a normal year to EUR 179 million (1).

The Alps

So far, forest fires do not constitute a significant hazard in the central and northern parts of the Alps, while on the southern side they are more common even if the fire number and the burned area are low compared to the neighbouring Mediterranean area, where the climate is more in favour of the development of frequent and large wildfires (3).

Due to their high potential impact in terms of human lives, commodities and natural heritage, the Alpine forest fires require a relatively large amount of resources for fire-fighting and prevention: the mountainous environment makes fire fighting very difficult, and a rapid intervention is required because the fires readily endanger human activities and infrastructures. Furthermore, secondary damages via other consecutive natural hazards, such as an enhancement of debris flows, erosion and avalanche danger, may occur, too (3).

The impact of climate change on the fire potential in the Alps in the past and in future scenarios has been evaluated from a multimodel approach (simulations from 7 Regional Climate Models), a detailed Regional Climate Model for the Alps area (COSMO), and data on daily temperature and precipitation observations during 1961–2010. The scenario period is 2031–2050; the RCM projections are based on the SRES scenario A1B. These model confirm previous results (4) that in recent decades the strongest increase of forest fire danger has been observed in the Southern Alps, while north of the Alps no clear trend was observed (3).

Southeastern France 

In southeastern France, most of the large fires (>120ha) occur within the coastal Mediterranean areas whereas the mountains (Pyrenees, Southern Massif Central and Southern Alps) are less affected. In the period 1973–2013 on average 66% of annual burnt area in southeastern France burnt during July and August. Corsica is by far the most fire-prone region of southeastern France (6,32). 

Trends of fire activity and climate across the Mediterranean and mountain ecosystems of south-eastern France over the period 1973–2009 show a general decreasing pattern of fire activity since the early 1990s, specifically during summer in historically burned regions (5). However, extreme conditions in fire weather (fire danger indices) have greatly increased in south-eastern France over the past four decades: the flammability of ecosystems in south-eastern France has probably increased in these recent decades (5,32).

Changing wildfire regimes in Mediterranean Europe

Human activities versus climate change 

Higher temperatures and more droughts not necessarily lead to an increase in the number of wildfires or the area burnt annually. Human activity may alter fire regimes to such an extent that climate change impacts are completely overruled. These human alterations may both increase and decrease fire probability (7). An increase may result from land-use changes or more outdoor activities (including tourism) (8). A decrease may result from more effective fire suppression. Changes in land-use and fire suppression policy seem to have exceeded the strength of climate change effects on changing fire regime in southern France during the period 1976-2009. The complex interaction of climate change and human effects, which may vary regionally and from one season to another, makes regional predictions of future fires highly challenging (7). A study on the Mediterranean region on fire trends in Portugal, Spain, southern France, Italy, and Greece in the period 1985-2011 revealed a general decreasing trend of the total annual burned area in all countries, with the exception of Portugal (30). Future projections show an overall increase in fire danger for France throughout the century, however, with the largest absolute increases in the Mediterranean area (31,32).

Climate effects: fuel-limited versus drought-driven fire regimes

With respect to climate effects, the situation is even more complicated because climate affects wildfires in two opposing ways. In dry ecosystems wet conditions may be so rare that not enough fuel accumulates to start large fires, and fire activity is limited. These areas have a fuel-limited fire regime. In moist ecosystems on the other hand, dry conditions may be so rare that fuel doesn’t get sufficiently dry to sustain fire spread. These areas have a drought-driven fire regime (7). The alternation of wet and dry conditions, however, favours fires by increasing the amount of fine fuel in litter, grass and shrub layers during wet periods, which burn more intensely in subsequent dry periods (9). In Mediterranean ecosystems both fuel-limited and drought-driven fire regimes are present (10).

Human alterations of fire regimes

Human activities directly modify the fire regime In the Mediterranean Basin by setting or suppressing fires and by changing patterns of vegetation in the landscape (11). Moreover, the fuel build-up following agricultural land abandonment as a result of the rural exodus has created an increasing fire hazard in Mediterranean Europe (12). On the other hand, changes in fire suppression policy over the last few decades have probably induced sharp decreases in fires (13). Hence the functional relationships linking fire to climate have been partially modified by human activities (14), decreasing or increasing the fire activity independently of climate change.

The example of southern France

In southern France three pyroclimates can be discriminated (7): (1) the Mediterranean mountains, characterized by a high seasonality in precipitation and fires (dry summers and wet winters), and the highest burned area fraction, fire season length and the strongest increase in fire danger over the last four decades, (2) the Temperate mountains, characterized by wet and cold conditions, and the shortest fire seasons and the lowest fire activities, and (3) the Mediterranean lowlands, with the driest and warmest climates, and strong and dry winds (the Mistral and Tramontane) that favour fire spread in summer. Human presence and activities decrease from the Mediterranean coast to the rural hinterland, with anthropogenic ignitions accounting for 90% of the number of fires and 96% of the total burned area (15).

During the period 1976-2009 the climatic influence on fires in southern France was not restricted to the occurrence and duration of drought during a particular year: a mixture of drought-driven and fuel-limited fire regimes operated, emphasizing the lagged effects of warm or moist periods on fire (16). Higher fire activity was related to wetter conditions in the last three years. This illustrates that fuel abundance is an important constraint on Euro-Mediterranean (and other) fire regimes, even when drought is the main driver.

With respect to human alterations of fire regimes, contrasting short-term impacts of changes in land-use and fire suppression policy have been found: more fires where fuel biomass is high as a result of land-use change, and less fires in fire-prone ecosystems due to more effective fire suppression (17). Indeed, in the Mediterranean lowlands, which are densely populated and highly susceptible to extreme fire weather due to strong winds (18), both winter and summer fire activity were strongly suppressed, suggesting a gradual increase in the efficiency of fire suppression policy (19).

Adaptation strategies

In the national strategy of France the following adaptation measures are recommended (2):

• improve forecasting in the zonal systems;
• optimise the means of combating forest fires in terms of cost/efficiency.

Adaptation strategies: impact of new fire policy of 1994 

Establishing new tactics and strategies for a better prevention and preparedness to face large fires has become a centerpiece of the European fire policy (21). Large and destructive wildfires are likely to increase in southern Europe due to changes in climate and landscape (22). Yet little is known about the return periods of large fires. This also holds for southern France, where 2500 fires have been reported each year in the period 1994 to 2016. Together, they have burned approximately 12,000 ha annually, on average (23). Most of these fires are small. The largest fires (> 100 ha) represent only 1 % of the total number of fires. However, they account for approximately 70 % of the total burned area and they consume two-thirds of the total annual budget dedicated to civil protection against fire risk (24). From 2001 to 2016, across France, the average large-wildfire area (exceeding 100 ha) was found to be 398 ha, with the largest wildfire reaching 7675 ha (28).

The return period of these large fires, characterized by their burned area, has been quantified for southern France (20). This was done for two periods: 1973 - 1994 and 1995 - 2016. A new fire policy was set up in 1994 to reduce the likelihood of very large wildfires. This policy is based on improved prevention of fires, increased surveillance of forests, and a massive attack on all ignitions in order to prevent fire enlargement (23). Thus, by focusing on these two periods, the impact of this new fire policy can be assessed.

The assessment shows that the new fire policy is undoubtedly successful (see also 29). The area that is burned on average every 5 years has significantly decreased. For very large fires (> 10 000 ha), for instance those with a return period of 50 years, this is not the case. Apparently, firemen cannot control many large fires. Despite the new suppression-oriented policy set up in 1994, very large fires can still occur in southern France, and especially in the regional hot spots of Corsica and Provence. These fires, that cause most of the accidents or fatalities for fire crews, may belong to a new generation promoted by global changes (25).

Very large fires, generating high human, economic, and ecological damages, are a growing issue in southern Europe and almost worldwide. A combination of climate change, fuel accumulation, and increasing human pressure on ignitions in urbanized areas is the root cause for a new generation of wildfires characterized by extreme behavior (25). These new types of devastative fires are increasingly observed in southern Europe, and many of them are beyond the present suppression capacity (26). They often display eruptive or erratic behaviors. Recent studies in southern France have shown that new combinations of prolonged droughts, heat waves, and windy periods lead to a higher frequency of such extreme fire events (27).

Massive aerial and ground forces for fire suppression may not be sufficient to control extreme wildfire events. Managing landscapes and fuels, limiting unwanted ignitions, and the participation of the public in self-protection (i.e., tackling the root causes of fire risk) are key to leverage fire risk in the long term.

References

The references below are cited in full in a separate map 'References'. Please click here if you are looking for the full references for France.

1. EEA, JRC and WHO (2008)
2. ONERC (2007/2009)
3. Cane et al. (2013)
4. Wastl et al. (2012), in: Cane et al. (2013)
5. Fréjaville and Curt (2015)
6. Ruffault et al. (2017)
7. Fréjaville and Curt (2017)
8. Ganteaume and Jappiot (2013), in: Fréjaville and Curt (2017)
9. Fréjaville et al. (2016), in: Fréjaville and Curt (2017)
10. Batllori et al. (2013), in: Fréjaville and Curt (2017)
11. Moreira et al. (2011), in: Fréjaville and Curt (2017)
12. Moreira et al. (2011); Pausas and Fernández- Muñoz (2012), both in: Fréjaville and Curt (2017) 
13. Pezzatti et al. (2013); Moreno et a.l (2014), both in: Fréjaville and Curt (2017)
14. Higuera et al. (2015), in: Fréjaville and Curt (2017)
15. Curt et al. (2016), in: Fréjaville and Curt (2017)
16. Keeley (2004); Pausas (2004); Meyn et al. (2007); Zumbrunnen et al. (2009); O’Donnell et al. Pausas (2011), all in: Fréjaville and Curt (2017)
17. McWethy et al. (2013), in: Fréjaville and Curt (2017)
18. Ruffault et al. (2017), in: Fréjaville and Curt (2017)
19. Turco et al. (2014), in: Fréjaville and Curt (2017)
20. Evin et al. (2018)
21. EFIMED (2011); Moreira et al. (2011); Fernandes et al. (2013); Tedim et al. (2016), all in: Evin et al. (2018)
22. Bedia et al. (2014); Oliveira et al. (2014), both in: Evin et al. (2018)
23. Curt and Frejaville (2018), in: Evin et al. (2018)
24. Chatry et al. (2010); Curt and Frejaville (2018), both in: Evin et al. (2018)
25. Costa et al. (2011), in: Evin et al. (2018)
26. Lahaye et al. (2018), in: Evin et al. (2018)
27. Ruffault et al. (2016a,b, 2018), in: Evin et al. (2018)
28. Barbero et al. (2019)
29. Ganteaume and Barbero (2019)
30. Turco et al. (2016), in: Silva et al. (2019) 
31. Fargeon et al. (2020)
32. Lestienne et al. (2022)