What causes large fires in Southern France

Abstract

In Southern France, where most wildfires occur, the fire size has never exceeded 6 744 ha since 1991, whereas mega-fires have burned huge areas in other Mediterranean countries such as Spain and Portugal. It was interesting to find out what main factors drove the ignition of the largest fires that had occurred in this region of France.The study was carried out using the forest fires database Prométhée that records all fires occurring in the 15 départements of Southern France since 1973. However, the records preceeding 1997 are not reliable, only the 1997-2010 period was investigated.Less than 1% of the fires (N=260) recorded during this period were equal or larger than 100 ha whereas 78% of the fires were smaller than 1 ha. However these large fires accounted for 78% of the burned area and 66% of these fires occurred during the summer (July-August). The number of large fires and the burned area per year and per département were calculated and the proportions of fires causes were determined.In each département, the impact of different explanatory variables (land-cover, topographic, climatic or socio-economic) on the number of large fires and on the size of the burned area was investigated using multivariate and regression analyses.Results showed that high shrubland and pasture covers, high population and minor road densities as well as dryness in fall to spring were positively linked to the number of large fires whereas high forest cover, ruggedness, wetness in fall to spring were negatively linked to this parameter. High wildland vegetation cover, especially shrubland, wetness in fall-winter, dryness in summer during a long period, high unemployment rate and tourism pressure were positively linked to the burned area whereas wetness in summer, high farmland and pasture covers and high population density were negatively linked to this parameter. However, only shrubland cover and ruggedness were significant descriptors of both fire occurrence and burned area.The départements the most affected by such fires were those situated in the eastern part of the region, on the Mediterranean coast and the main fire cause was arson.

Increased vulnerability to wildfires and post fire hydro-geomorphic processes in Portuguese mountain regions: what has changed?

“…"Arrolamento Geral de Gados e Animais de Capoeira" : 1934, 1955and 1970"Recenseamento Agrícola do Continente": 1989, 1999, Instituto Nacional de Estatística of the Piodão and Pomares parishes, respectively) ( Figure 7). Several studies confirm that this land cover is one of the types most seriously affected by wildfires (Nunes et al 2005;Sebastián-López et al 2008;Catry et al 2009;Moreira et al 2009;Bajocco and Ricotta 2008;Nunes 2012;Carmo et al 2011;Oliveira et al 2012;Ganteaume and Jappiot, 2013;Oliveira 2014;Nunes et al 2016). Conversely, Nunes et al (2016) found that in Portugal at municipal level, traditional activities based on agriculture, grazing and forestry seem to reduce the burnt area, suggesting that the survival of Mediterranean silvopasture activities reduces the frequency and impact of forest fires.…”

Trends in adverse weather patterns and large wildland fires in Aragón (NE Spain) from 1978 to 2010

“…Agricultural abandonment is the main cause of an increased fuel load (Millán et al, 1998), but wildland fuel homogeneity and continuity are also major facilitators of both a fast fire propagation and a higher fire line intensity Vega-García and Chuvieco, 2006). In addition, climate and weather are two of the main factors influencing fire regime (Trouet et al, 2009), and climate change could have an important impact on ecosystems due to increases in area burned and fire intensity/severity (Flannigan et al, 2000). Regato (2008) showed that climate change could provide an increase in the intensity and frequency of summer heat waves (short periods with very hot days, very low air humidity and frequently with strong winds) that increase the probability of large wildland fire (LWF).…”

“…Typically, just a few LWFs cause the majority of the damage (Alvarado et al, 1998;Ganteaume and Jappiot, 2012) because they account for a very high percentage of the total burned area (Stocks et al, 2003), and their severity is normally higher. In these LWF events fire behavior is often extreme, making suppression difficult.…”

Conservation Measures and Loss of Ecosystem Services: A Study Concerning the Sardinian Natura 2000 Network

“…In fact, although environmental protection and minimization of fire risk should promote the protection of the areas and sites characterized by environmental and/or natural resources, the construction of new roads and pathways, the increment of rural areas and the promotion of rural tourism could potentially generate negative impacts. For example, according to Ganteaume and Jappiot [40], the presence of minor roads and tourism pressure are drivers for the occurrence of large fires and the size of burned areas, respectively. Moreover, we observe, following Burkhard et al [37], that the land use categories, included in the "Mountain of Sette Fratelli" SPA, have a high-to-medium capacity to provide livestock.…”

“…Moreover, we observe, following Burkhard et al [37], that the land use categories, included in the "Mountain of Sette Fratelli" SPA, have a high-to-medium capacity to provide livestock. Furthermore, pastoral activities and pasture may generate negative impacts in relation to habitats' protection (MP of the SPA "Mountain of Sette Fratelli") and fire occurrence [40].…”