Spatio-temporal analysis and risk management of forest fires (West Algerian region)

Algeria has a surface of 2,381,741 km² and is divided into 58 Wilayas (provinces) and 1541 municipalities. It has 2 important mountain ranges: the Tellian Atlas (from “Tell” a region in Algeria) in the North and the Saharian Atlas in the South. They divide the country into 3 types of environments characterized with their relief and morphology; from north to south, we find the Tellian system, the steppic high plains, and the Sahara (Fig. 1).

Figure 1.

The relief is divided into 2 rainfall gradients: a North–South decreasing gradient and a West–East increasing gradient (Tabet 2008).

Forest lands occupy 4,115,908 acres, i.e., 16.7% of North Algeria. They are made up of 58% scrubland and woody scrubland. However, natural forests and reforested sites cover only 42% of the total forest formations.

The Wilaya of Mascara, located in the West, is an adequate case study as it covers a surface of 513,000 acres with 47 municipalities (Fig. 2). Its topographic space may be classified into 5 relatively distinct homogenous zones with 504 douars (Algerian countryside). It is a semi-arid region with an average altitude of 600 m, ranked as a middle mountains area.

Figure 2.

The territories of the Wilaya of Mascara are made up of 5 individualized morphologic unities (Fig. 3) that are all oriented South-West/North-East.

Figure 3.

The 5 zones are as follows:

• Habra-Sig plain

• Beni Chougrane mounts

• Mascara-Ghriss plain

• Said (Aoufs) mounts

• Tessala Mascara mounts

The two important zones in the forested development and valorization of the mountain lands are the mounts of Beni Chougrane and the mounts of Saida (Aoufs) which represent 51% of the total surface. The forest surface of Mascara is 90,223 acres, i.e., a level of forestation of 17.57% of which 37,470 acres are forests, 52,571 acres are scrubland, and 182 acres are arable spaces.

A data analysis on the burned surfaces and the fire zones has been carried out from the internal archives and documents of the General Directorate of Forests which is part of the Ministry of Agriculture, Rural Development and Fishing. These data are available in the form of annual records of fires. Collected forest fires data (number of fires, damaged surface, and year of record) are saved in the form of Excel sheets, allowing all kinds of data manipulation and visual interpretations.

The methodological approach is based on the study of two parameters: the burned surface and the number of fires during 15 years (2003–2017) in 40 Wilayas of the North and Mascara.

The realization of the infrastructure map and that of forest fire dangers required the use of the Geographic Information System “ArcGIS 10.3” in order to integrate the collected data on the field (GPS points) in a digitalized database.

We studied three types of infrastructure proposed in Algeria’s forest fire-fighting plan, DFCI plan “Defense Forests Fire,” which are the fire break trenches, the tracks, and the lookout point. The aim of the firebreak trenches is to create a discontinuity of forestation in order to reduce the intensity of fires. They must be established perpendicularly to the winds’ orientation (Arbonnier and Faye 1988).

The rapid and guaranteed arrival to the incident can be guaranteed only through a sufficient number of the tracks that are well maintained.

Surveillance generally relies on lookout points located in high spots. Operators observe big parts of the territory with 360° coverage in order to make alerts when they suspect fires and precisely localize their occurrences.

The climatic study of Matmore station in Mascara for the period of 2007–2017 (474 m altitude, municipality n°14) (Fig. 3) contains the following 5 parameters: average annual and monthly temperature, average annual and monthly precipitations, humidity, evaporation, and wind speed. This climatic study enables us to make the relation between the climate and fire occurrence and spread. Indeed, assessing the impact of climate change on the future size of fires is important. Regional climate model simulations in the United States predict an overall increase in fire potential and an extension of the forest fire season in the future climate (Yu et al. 2023).

A number of dynamical methods have been developed in order to produce short-term hazard indices, such as the Fire Probability Index and the Fire Weather Index (Laneve et al. 2020; Vitolo et al. 2020). Multiple fire danger indices (FDIs) that incorporate weather and fuel conditions have been developed and utilized to support wildfire predictions and risk assessment (Tores et al. 2017; Hadisuwito and Hassan 2020; Yu et al. 2023; Atalay et al. 2024). In this paper, we have integrated different human activities in the realization of a map indicating fire-prone zones. The aim is to answer this question: Which areas present a high risk of fire starting?

To model fire danger, we opted for the Fire Danger Index (FDI) developed by Arfa et al. (2019) in Algeria, which is expressed with the following relationship (eqn. 1): (1) FDI=DFarm+DRH+DAgri+DTrack {\rm{FDI}} = {\rm{DFarm}} + {\rm{DRH}} + {\rm{DAgri}} + {\rm{DTrack}} were:

• D – the danger level related to the approximation of the following elements:

  • farms that indicate cattle ranching activities (Dfarm);

  • rural houses indicate the human presence (DRH)

  • agricultural lands (DAgri);

  • forest tracksthat allow the access to the forest massifs (DTrack).

For each of these criteria, the values of danger level D range from 1 (low danger) to 5 (very high danger). These danger levels are determined according to the rate of the declared fire numbers between 1985 and 2012 and the distance that separates them of each criterion. The hazard levels retained are as follows:

• D = 1: Low danger with a fire number rate equal to 5%

• D = 2: Moderate danger with a fire number rate equal to 10%

• D = 3: Average danger with a fire number rate equal to 20%

• D = 4: High danger with a fire number rate equal to 30%

• D = 5: very high danger with a fire number rate equal to 35%

The values of FDI are between 4 and 16. There are 5 classes code:

• Low: FDI =4

• Moderate: 4 <FDI ≤ 8

• Average: 8 <FDI≤ 12

• High: 12 <FDI ≤ 16

• Very high: FDI> 16

The global burned surface between 2003 and 2017 in North Algeria (Tellian Atlas) was 482,000 acres for 40,000 fires with an average of 32,133 acres per year. In the years 2007, 2012, 2014, and 2017, the burned surface exceeded 40,000 acres for each year with a total of 42% of the global burned surface with a peak in 2012 which witnessed 99,000 acres burned. They are subject to seasonal variability due to meteorological factors (precipitation, temperature, wind) or biotic factors (fuel type and structure). The North-Eastern region of Algeria (Skikda, Annaba, and Tarf) is the mostly damaged (Arfa et al. 2018). Table 1 shows that the burned surface in these three Wilayas during 2015–2018 was 31,333 acres, which represented 45% of the total burned surface (68,993 acres).

Analysis of fire data of the Northern region of Algeria (Fig. 4) shows a good correlation (R²= 0.69) between the number of fires and the burned surface during 2003–2017. The two indexes are well related.

Figure 4.

Figure 4 shows a stability in the period of 2003–2011 and a peak in 2012 which was marked with hot waves making the whole Northern region of Algeria witness significant temperature rise (Boudjemline et al. 2016).

Zeineddine (2011) confirms the return of rains during the last years of the period between 2002 and 2006. The rain which falls on the Algerian territory became more intense in 2007, 2008, 2009, 2010, and 2011, which explains the low number of fires during those years.

The global burned surface during the period from 2003 until 2017 in Mascara (Fig. 5) is 6,721 acres in 286 fires, with an average of 448 acres per year. In 2005 and 2014, the burned surface exceeded 1,000 acres with a rate of 47% of the global burned surface. In 2005, there was a peak with a surface of 2,042 acres. The correlation coefficient is equal to 0.71, which means that the number of fires and the burned surface of Mascara during 2003–2017 are well correlated.

Figure 5.

The total burned surface depends on the meteorological conditions. The number of fire occurrences related to imprudence is correlated with the density of the population in the natural space which depends on the meteorological conditions. In relatively “wet” years, there has been little human presence in the natural area, resulting in fewer incidents, small fires that can be easily fought, and, consequently, a low surface area burnt.

We clearly see that the scrubland of Mascara (53% of the forest massifs) is the formation that is most subject to forest fires with a rate of 61.12% during this decade. The forests witnessed fires with a percentage of 21.43%–14.36% for the scrub (Fig. 6). According to Belgherbi et al. (2018), the matorral is vulnerable to the fires more than the other forest formations.

Figure 6.

The most sensitive part of the day subject to fires is between midday and 4 pm where the temperature reaches its peak. 50% of the fire incidents have been registered during this period of the day.

The number of fire occurrences depends on the ignition of the combustibility and the water state of the vegetation determined by the dryness and humidity of the ground and the air (Chevrou 1998; Souidi et al. 2009). According to Souidi (2010), the water stress concords with the hottest and most humid hours of the day (maximal temperature, maximal humidity).

The climate of Mascara belongs to the tempered Mediterranean type characterized with two seasons. The humid season starts from October till May, while the dry season starts from June to September. The very rough terrain complexity contributes to the creation of various micro-climates in the region.

The Ombrothermic diagrams of Gaussen (Fig. 8) that are traced with data of the rains and average temperature of the period 2003–2017 show a dry period that lasts from April to October (i.e., 6 months) with the variations of the climate from one year to another. This period tends to become longer.

Figure 7.

Figure 8.

The meteorological conditions are the major factor on which the burned surfaces depend and their number decreases in an important way according to the quantity of the precipitations (Yu et al. 2023; Turco et al. 2023).

The monthly annual averages vary between 28°C and 32°C due to the geographic situation of the study zone which is mountainous and its semi-arid region. According to Figure 9, the number of fires generally increases as the temperature rises, which influences fire ignition by drying out vegetation, making it sensitive and flammable. The increase in the area burnt and the intensity and severity of fires, which will have a significant impact on forest ecosystems, is the consequence of the impact of climate change on the fire regime (Flannigan et al. 2000; Yu et al. 2023).

Figure 9.

The annual average precipitations vary between 20 and 30 mm, which are quite little for the prosperity of the vegetation in the best conditions.

The number of fires increases generally with the increase of the wind speed, which has an influence on fire ignitions by drying the vegetation making it vulnerable and leading to the spread of the fire and to the creation of new fires from the transported flames.

Analysis of the annual averages of the climatic parameters does not show clearly their relation with the fire occurrences. This requires an in-depth study of the monthly averages of the climatic parameters.

Table 2 indicates the existing infrastructure in linear kilometers of tracks and in surface of firebreak trenches throughout Mascara (Fig. 2).

According to BNEDER (2008), the generally accepted norms for the intensive management of the forests require 2 km of tracks for 100 acres of forest and 2.5 acres of firebreak trenches for 100 acres of forest.

Table 2 shows clearly the relation between the networks of tracks and the burned surface. In the forests that have an important surface and a low number of tracks, the burned surface is big, and vice versa. In the municipality of Hachem which has a forest surface of 4,586.2 acres and a track volume of 20 km, the burned surface is 387 acres; in the municipality of Nesmoth which has a forest surface of 6,495.36 acres and a track volume of 25 km, the burned surface is 265.5; in the municipality of Ain Fekan which has a forest surface of 4,458 acres and a track volume of 30 km, the burned surface is 24.9 km; while in the municipality of Ferraguig with a 1,822.89 acres of forests and a track length of 36 km, there were no fires.

In Mascara, the forest tracks are 1,059.35 km long, i.e., a density of 1.4 km for each 100 acres of forest (Fig. 15). This is insufficient regarding the norm that recommends 2 km of track for each 100 acres of forest (BNEDER 2008). The total number of tracks to be considered in the development program for the Wilaya of Mascara, to meet the standard, would be 786 km. These needs are relatively high at the level of the forests of Zelmata municipality (143 km), Nesmoth municipality (89.5 km), and Cheurfa municipality (354 km). Furthermore, the existing tracks are not very efficient and do not meet the requirements (insufficient width and absent or insufficient lateral protection) and need maintenance. The existing tracks will be progressively adapted to the norms which may be the opportunity to get rid of the inefficient ones.

Figure 15.

As for the firebreak trenches, the forests of the Wilaya have 936 acres of trenches. However, they need 1,035 acres. The needs are important for the forests of Zelmata (193.5 acres), Nesmoth (111.5 acres), Sdamas Guerbi (153 acres), and Cheurfa (529.5 acres).

The number of forest houses is superior to the norm that states1forest house for each 10,000 acres. Under the general rules, Mascara is allowed to have 8 houses instead of its usual 12, and the same applies to most of the forests, with the exception of Cheurfa, where the number of forest houses is low. The equipment with lookout points is sufficient as there are 28 points in total, while 11 points are required according to the norms.

Activities in the national forest are restricted for the people living inside or near those forests, and these activities usually include collecting products for the domestic needs and the enhancement of the life conditions.

The empty spaces inside the forest are meant to valorize the lands for the plantation of fruits (Tab. 3) for the inhabitants who will protect the forest against the fires by being the first to detect fires and fight against their spread.

Map representing the classification of Mascara forests according to their vulnerability to forest fires.

Figure 10 shows the spatial variability of the fire dangers in the forests of Mascara. Findings show that the most endangered class, which is the most represented, covers more than 74% of the forests. Only 0.16% of the forests are at low danger class.

The study of the fire records of Mascara shows that the most damaged forest massifs are located in the South and East of the Wilaya, where the scrubland occupies the 1st place among forest formations (Meddour-Sahar et al. 2013).

Firefighters signaled a lack in their infrastructure especially in the regions at high risk and where the forest massifs are not accessible.

The forest zones belonging to two classes of “moderate” and “low danger” (Fig. 16) are the smallest forests with surfaces of 30 acres to 100 acres, and they are accessible and easy to manage concerning prevention and fight.

Figure 16.