1. Introduction
Forest fires rank among the most intricate and prevalent natural disasters. They have the capacity to engulf vast expanses, often infiltrating remote and challenging terrains, thereby compounding the already formidable task of extinguishing them. In recent years, these fires have emerged as a principal concern affecting both our nation and the global community. Alarming statistics underscore the growing frequency with which these fires spiral beyond containment. Consequently, the affected regions witness escalating devastation in terms of burnt acreage, material losses, and environmental contamination. The evolving landscape of forest fires presents a pressing challenge for communities and nations alike [
1].
A recent forest fires analysis reveals that they occur most often in the foothills, where forests alternate in close proximity with cereal crops. The intensive movement of people and equipment in these areas during harvesting and fodder, the throwing of unextinguished matches and cigarettes, the use of open fire for various purposes and the burning of stubble without prior precautions are the prerequisites for ignitions and for carrying the fire in the forest massifs [
2,
3,
4]. In addition to large losses of valuable wood, forest fires also cause hard-to-recover damage to the environment: a significant amount of harmful substances are released into the atmosphere, oxygen generation decreases, soils are destroyed, and flora and fauna are irreparably damaged.
In recent years, there has been a drastic increase in fires worldwide. Our country is no exception. There is no single methodology for effectively fighting forest fires, which makes the subject of forest fires and the protection of forest areas very relevant.
In the presented work, a methodology is given for determining the rate of fires by region in Bulgaria, and how the amount of carbon dioxide released during forest fires is determined for coniferous and broad-leaved forests.
2. Analysis of Risk Assessment of Forest Fires
The assessment of the risk level of forest fires in the forested areas of the country is conducted following the guidelines established in reference [
5], following this specific sequence:
The concentration of forest fires in forested region within a country, denoted as
Rd, is determined as follows:
where
Rd. is the average value of the fires for forest region per year (units/year/1000 ha);
Ni is the number of fires (units/year);
n is the number of years for the analysed period (
n = 10); and
Ft. is the total country forest area (ha).
With the help of Equation (2), the inflammability of the forest regions can be calculated as an estimate of the burned areas for the period:
where
Rac. is the average value for the actual combustibility of the country forest territory for 1 year (ha/year/1000), ha; and
Fba. the annual burnt area in the country forest territory (ha/year).
The magnitude of the risk of forest fires, denoted as
Rrf, is determined as an integrated indicator, incorporating the numerical values for
Rd—the density of forest fires and
Rac—the real inflammability of forest territories, using the following formula:
The methodology shown in
Figure 1 shows the risk of forest fires by region in the territory of Bulgaria.
Figure 1 shows the distribution of fires by area. It can be seen that the high risk areas are like those shown based on the statistics in the next part.
3. Calculation of the Amount of Carbon Dioxide Released
In this section, calculations have been made of the amounts of carbon dioxide released during forest fires for the last two years. The calculations were made for broadleaf and coniferous forests and were divided by the regions of Bulgaria.
Figure 2,
Figure 3,
Figure 4 and
Figure 5 shows the burned areas by region in Bulgaria for 2021 and 2022, and they are divided into broad-leaved and coniferous forests.
Depending on the year and the location of the fires, the following dependence is observed, that there are more fires in broad-leaved forests than in coniferous forests. This can be explained by the fact that there are more broadleaf forests in the territory of Bulgaria, and they are also more accessible to humans than coniferous forests, and can be further explained by the fact that most fires occur as a result of human error.
Forest fires represent a complex mixture of chemical compounds. These fires release primarily carbon dioxide (CO2), along with methane and nitrogen oxides, all of which not only contribute to environmental challenges but are also toxic to human health. But, fires also emit aerosols, soot (extremely fine particles) and tar.
In addition, as they are more numerous and larger, fires increasingly affect the quality of the air breathed by the population. The combustion of trees releases carbon dioxide (CO2), which is the primary greenhouse gas responsible for global warming.
Figure 6 presents a calculation of the amount of released carbon dioxide (
Es) by year, based on burned forest massifs. The calculations were made according to the following [
6]:
where
is the burning factor, %;
S is the burned forest stands in ha; and
B is the heat load of forest massifs, kW/m
2. For the calculations, an average value was taken for forest massifs typical for the territory of Bulgaria;
- coefficient of CO
2 release.
In
Figure 7,
Figure 8,
Figure 9 and
Figure 10 is the given amount of emitted carbon dioxide for deciduous and coniferous forest for 2021 and 2022 divided by municipality in Bulgaria.
The results are made according (3) for deciduous and coniferous forests.
The heat load is taken as an arithmetic mean of the most common trees in broad-leaved and coniferous forests in the territory of Bulgaria. The value of B for different kinds of trees is given in
Table 1.
Nearly 70% of Bulgaria’s forests are deciduous. They are widespread in the lowlands, plains, and low mountains, even at an altitude of up to 1500 m above sea level.
The most widespread broad-leaved tree species are oaks, beech and hornbeam. Apart from them, sycamores and ash, elm, linden, and poplar, etc., are often found in our forests.
The most characteristic conifers of Bulgaria are the white pine, the black pine, the spruce, the fir, the white and the black mulberry, and the squat, etc. White pine is the most widespread coniferous tree species in Bulgaria, followed by spruce. Forests with a predominant presence of black pine are ranked third in terms of area, and forests with the presence of common fir are also relatively widespread.