UNIVERSITA’ DEGLI STUDI DI PISA
SCUOLA DI INGENGERIA
DIPARTIMENTO DI INGEGNERIA CIVILE E INDUSTRIALE
Corso di Laurea Magistrale in Ingegneria Edile e delle Costruzioni Civili
Tesi di Laurea
SAFETY OF MUNICIPALITIES IN
CASE OF WILDFIRES
Relatori:
Candidato:
Prof. Ing. Mauro Sassu
Luca Bernardini
Dott. Ing. Linda Giresini
Dott. Ing. Mario Lucio Puppio
Prof. Ing. José Campos E Matos
Ing. Alessandro Pucci
Acknowledgement
First of all, I would like to thank who made this project possible. Thanks to Mauro Sassu, Linda Giresini and Mario Lucio Puppio for giving me the opportunity to carry out my Master Thesis abroad and for the helpfulness and support demonstrated during the development of the entire work. Moreover, thanks to Professor José Campos E Matos for having welcomed me in the University of Minho with kindness and enthusiasm, for the competence demonstrated and for the confidence he has given me from the first day. A special thanks goes to Alessandro Pucci for the professionalism shown during these months, for his suggestions and for the support he gave me during the entire thesis period, he really made many efforts to help me and to make the thesis more suitable for me.
Furthermore, thanks to Portugal, to all the fantastic people I met during the ERASMUS Project and if I feel Guimarães now as a second home it is also thank to you.
A very special thank absolutely goes to my family, my father Mario, my mother Rosalia and my sister Valeria who even in the hardest moments they have always supported me and encouraged me not to give up and to believe in myself. Thank you because you have always allowed me to pursue my goals and dreams. Thank you to my grandfather Fosco, who with his words “È più dura la vanga o la penna?” or “Smetti di studiare e vieni di qua che ti rilassi un po’ po’” he always manage to make me smile and he make me appreciate the real moments of everyday life, for example watching with him Tv programs like L’Eredità and guess the game La Ghigliottina.
Thank you to all my University colleagues with whom I shared all these long University years made of notes, plans, joys and sorrows. Without their presence and help these years would not have been the same. A very special thank goes to Pippo Bertini, my inseparable colleague of every University moment within the walls of the school of Engineering. It was a pleasure to start and finish this journey with you. Thanks to my friends of a lifetime too, who have been with me in every step of my life. Thank you for putting up with all my answers to your messages like this one “I’m sorry, I can’t. I have to study”. Last but not least, thank you Cami for the patience you had with me during the period I was in Portugal and for always being an inexhaustible source of suggestions, thank you for having the right word in every situation and for having the smile that always push away my worries and anxieties.
Pisa, December 2019
RINGRAZIAMENTI
Innanzi tutto, vorrei ringraziare chi ha reso possibile questo lavoro. Grazie a Mauro Sassu, Linda Giresini e Mario Lucio Puppio per avermi dato l’opportunità di svolgere la tesi fuori sede e per la disponibilità dimostrata durante lo sviluppo di tutto il lavoro. Inoltre, grazie al Professor José Campos E Matos per avermi accolto all’Università di Minho, per la competenza dimostrata e per la fiducia datami fin dal primo giorno. Un ringraziamento speciale va ad Alessandro Pucci per la professionalità dimostrata in questi mesi, per i numerosi consigli e per il supporto che mi ha dato durante l’intero periodo di tesi, mi ha permesso di portare a termine il lavoro rendendolo sempre più adatto a me.
Grazie al Portogallo e a tutte le fantastiche persone conosciute durante l’ERASMUS perché, se adesso sento Guimarães una seconda casa è anche merito vostro.
Un grandissimo grazie va assolutamente alla mia famiglia, babbo, mamma e Vale che nei momenti di difficoltà mi hanno sempre spronato a non mollare e a credere in me stesso. Grazie perché mi avete sempre permesso di perseguire tutti i miei obiettivi e sogni. Grazie a nonno Fosco che con i suoi “È più dura la vanga o la penna?” o “Smetti di studiare e vieni di qua che ti rilassi un po’ po’” mi ha sempre strappato un sorriso e fatto apprezzare anche i piccoli momenti di quotidianità come guardare
L’Eredità e indovinare La Ghigliottina.
Grazie ai miei compagni universitari con cui ho condiviso tutti questi fantastici anni fatti di appunti, progetti, gioie e dolori. Senza di loro questo percorso non sarebbe stato lo stesso. Un ringraziamento speciale va a Pippo Bertini, compagno inseparabile di ogni momento vissuto tra le mura di Ingegneria. È stato un piacere iniziare e finire insieme a te questo percorso.
Un ringraziamento va anche agli amici di una vita che da più di 25 anni mi accompagnano in ogni passo. Grazie per aver sopportato tutti i miei “No devo studiare” con cui ho risposto ai vostri messaggi. In fine ringrazio Cami per la pazienza dimostrata durante il mio periodo in Portogallo e per essere sempre fonte inesauribile di consigli, la parola giusta in ogni situazione e il sorriso che scaccia via ogni mia paura e ansia.
Pisa, Dicembre 2019
Emancipate yourselves from mental slavery none but ourselves can free our minds
Index
1. Introduction
8
2. State of Art
10
2.1 The Forest Fire in the History of Life 11
2.1.1 Pre-Human Era 11
2.1.2 Human Era 12
2.1.3 Modern World 13
2.2 Causes of Wildfires Ignition 15
2.2.1 Causes and Motivations 15
2.3 Fire Spread 19
2.3.1 Development of a Forest Fire 19 2.3.2 Main Types of Fire Spread 20 2.3.3 Main Factors Affecting Fire Spread 23 2.4 Forest Fire Consequences on Ecosystem 25 2.4.1 Gas Emissions in the Atmosphere 25
2.4.2 Effects on the Soil 26
2.4.3 Effects on the Vegetation 30 2.4.4 Effects on the Wildlife 32
2.5 Wildfire Management 33
2.5.1 Risk Maps 33
2.5.2 Wildfire Risk on the Wildland-Urban Interface 34
2.6 Coexist with Wildfire 37
2.6.1 Europe, the Mediterranean Basin 37
2.6.2 American Forest Fires 40
3. Geographic Information System
43
2
3.1.1 QGIS Extensions 44
3.1.2 Raster and Vector Data 45
3.1.3 DEM and DTM 47
3.1.4 Database 48
4. Fires and Economic Analysis
50
4.1 Wildfire Analysis 51
4.1.1 Rate of Spread 53
4.1.2 Rate of Spread Parameters 58 4.1.3 QGIS Steps to Find the Rate of Spread 61
4.2 Costs Analysis 64
4.2.1 Bill of Quantities (BOQ) 66
5. Application to a Case Study
68
5.1 Rate of Spread of Massa district 70
5.2 Antona 76
5.3 Casette 80
5.4 Forno 82
5.5 Resceto 86
6. Discussion of Results
88
6.1 Early Warning Systems (EWS) 89 6.1.1 Early Warning System for Forest Fires 92
6.2 Future Applications 98
Index of Figures
2. State of Art
Figure 2. 1: Fire Triangle 15
Figure 2. 2: Signal of fire hazard 16
Figure 2. 3: Fire growth, spread and decay 19
Figure 2. 4: Ground fire 20
Figure 2. 5: Surface fire 21
Figure 2. 6: Crown fire 21
Figure 2. 7: Spot fire 22
Figure 2. 8: Analogy between fire triangle and factors affecting fire spread 23
Figure 2. 9: Fire spread affects from weather, topography and fuel 24
Figure 2. 10: High severity fire effects and factors that control post-fire recuperation, [22] 29
Figure 2. 11: Development of Hydrophobic Soil 30
Figure 2. 12: Landscape after forest fire on pine forest “Ramazzotti” near Ravenna 30
Figure 2. 13: Vegetative reproduction 31
Figure 2. 14: Seed reproduction 31
Figure 2. 15: Number of forest fires in Italy 38
Figure 2. 16: Area burnt in Italy 39
Figure 2. 17: Landscape of Pisan mountains after the forest fire 39
Figure 2. 18: Crown fire. The North Fork fire approaches the Old Faithful complex on September 7,
1988. 41
Figure 2. 19: Amazon forest fire, August 2019 42
3. Geographic Information System
Figure 3. 1: Logo Quantuom GIS 44
Figure 3. 2: GRASS and SAGA logo 45
Figure 3. 3: Attribute table of Massa district 46
Figure 3. 4: Raster structure [62] 47
4
4. Fires and Economic Analysis
Figure 4. 1: Flow of calculations in the fire spread model [67] 57
Figure 4. 2: Forest distribution of area of study 62
Figure 4. 3: A part of attribute table with fuel factors 62
Figure 4. 4: Rasterize 63
Figure 4. 5: Raster Calculator 63
Figure 4. 6: Variable distance Buffer 65
Figure 4. 7: Market value 67
5. Application to a Case Study
Figure 5. 1: Case of study 68
Figure 5. 2: Towns of the case of study 69
Figure 5. 4: TL1 fuel models to represent the coniferous forests 70
Figure 5. 5: TL9 fuel models to represent the broadleaved forests 71
Figure 5. 6: Shape file of wind velocity 72
Figure 5. 7: Wind factors 72
Figure 5. 8: DTM of Massa province 73
Figure 5. 9: Slope factors 74
Figure 5. 10: Rate of Spread on Massa district 75
Figure 5. 11: Vulnerable Area of Antona 77
Figure 5. 12: Area at Risk of Antona 78
Figure 5. 13: Overlap between Vulnerable Area and Area at Risk 79
Figure 5. 14: Vulnerable Area/Area at Risk of Casette 81
Figure 5. 15: Vulnerable Area of Forno 83
Figure 5. 16: Area at Risk of Forno 85
Figure 5. 17: Overlap between Vulnerable Area and Area at Risk 85
Figure 5. 18: Vulnerable Area of Resceto 87
6. Discussion of Results
Figure 6. 1: Main principle of Early Warning System 89
Figure 6. 3: Regular deployment with square layout 95
Figure 6. 4: Regular deployment with hexagonal layout 96
Figure 6. 5: Tower for the monitoring of forest 98
6
Index of Tables
4. Fire and Economic Analysis
Table 4.1: Components of width of Vulnerable Area 51 Table 4.2: Components of Rothermel equation 54 Table 4.3: Input parameters for the fire spread model 55 Table 4.4: Equations for the fire spread model 56 Table 4.5: Components of cost factors 64 Table 4.6: Components of width of Area at Risk 65
5. Application to a Case of Study
Table 5.1: Width of Vulnerable Area, Antona 76 Table 5.2: Buildings characteristics and CF, Antona 77 Table 5.3: Width of Area at Risk, Antona 78 Table 5.4: Width of Vulnerable Area, Casette 80 Table 5.5: Width of Vulnerable Area, Forno 82 Table 5.6: Buildings characteristics and CF, Forno 84 Table 5.7: Width of Area at Risk, Forno 84 Table 5.8: Width of Vulnerable Area, Resceto 86
6. Discussion of Results
8
Chapter 1
Introduction
The forest fires have played a very important role since the born of the first vegetation on the earth. Before the human, only the vegetation is strongly influenced by forest fires, after the advent of humans, their buildings and the vegetation are strongly influenced by forest fires. The wildfires have continued to influence these factors until now. They modify and change whole landscape after their passage.
The forest fires are difficult events to predict because they are not created by recurring and easy predict events, but they are caused by external influences. The main influences are the humans and then the climatic events. These are rare and difficult to predict; an example is the fall of lighting. This classification shows four kind of causes: natural causes, negligent causes or involuntary, malicious causes or voluntary and unknown causes. The passages of wildfires always make damages to people and natural environment. These damages depend on the level of fire spread, the time between ignition and extinction and intensity of the event, in addition the damages also depend on the lay of the land and weather conditions.
The risk analyses are used to predict and decrease the forest fire risk. These analyses could be used to develop a risk map or to decrease the wildfire risk on the wildland-urban interface. The first kind of analyses identifies the area with forest fire risk, and they can propose a monitoring or decreasing risk solutions by software QGIS and a specific knowledge of the vegetation. Indeed, the works to reduce the wildfire risk on wildland-urban interface modify the vegetation around the towns or residential area with high forest fire risk.
The thesis discusses the combination of these two risk analyses, and it proposes a framework to predict an Area at Risk on the wildland-urban. It proposes a monitoring method of Area at Risk to ensure an efficient and immediately action of the Firemen. The Area at Risk and its monitoring significantly reduce the time between detection and wildfire alarm, in addition reduce the probability that the flames reach the residential areas and their habitants.
The thesis is divided in six chapter, where it describes the causes, steps and consequence of forest fire, the various risk analysis, the software used in this work, the framework made for this work, application of the framework on the case of study.
The structure of the thesis is as follows:
- Chapter 2: brief introduction of how first the wildfires have influenced the environment and after the human since the birth of the world until now. Subsequently it has been described the causes of forest fires, their spread on the land and vegetation, the factors that influence the fire behavior and the consequence on the people, land and vegetation after the passage of the fire. Finally, the chapter contains the risk analyses which is used in these situations and an overview about the forest fires in the world;
- Chapter 3: overview on the software used in this thesis, QGIS and their parts. In addition, the chapter show the database used to do the work;
- Chapter 4: it shows the framework used on the thesis. It analyses the method and every its steps. It is divided in two part. On the first part, it discusses the wildfire analysis with every element on which depends and every step to arrive at the final result. Instead, the second part discusses a cost analysis. This is used to add the building factor (importance of the buildings) on the framework;
- Chapter 5: application of the framework to the case of study. It shows the final results which have been found by the method described before and all values which have been found before the final results by wildfire and cost analysis;
- Chapter 6: It discusses the possible monitoring systems which used in Italy and in other parts of the world and the benefit which this work can bring to the existent fire-fighting plan.
10
Chapter 2
State of Art
Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. It can occur with or without development of flames. There are factors for the physical process of fire: fuel, oxygen and heat.
The UNI EN 2 2005 divides the fires into five classes, according to the characteristic of fuel material: - Class A: solid fuel (organic origins);
- Class B: liquid fuel; - Class C: gas fuel; - Class D: metal fuel;
- Class F: cooking fuel (vegetable or animal oils).
In addition to this classification [1], the fires can be classified according to the place where it burns: building fires or forest fire (knows as wildfire). The main difference between them is the fire’s behavior. Building fires have a random spread and, the spread factors of fire are difficult to simulate because, in general, the kind of building, the kind of stuff inside and the possible interactions between rooms or floors are intrinsically probabilistic elements1 [2]. On the other side, the forest fires are usually wider
than building fires, because the fuel area can expand for many kilometers on mountains or hills. In contrast of what happen on buildings, wildfire’ behaviors can be predicted with much accuracy since fire parameters are well defined [3][2].
2.1 The Forest Fire in the History of Life
During the history of life, the fire has played a main role on ecological system during the pre-human era. It has proven to be crucial on the main role on human era too, especially during the pre-industrial period the modern one [4].
2.1.1 Pre-Human Era
The origin of fire is strictly tied to the origin of plants, which are responsible for two of the three essential elements to generate a fire: oxygen and fuel. The third element, i.e. the heat, has probably been available throughout the history of the planet thanks to lightning, volcanic eruptions and sparks from rock falls and meteorite impacts. The first fires have been estimated to happen 440 million years ago (mya) with the first low-growing vegetation [4]. The subsequent fire history on Earth is marked by periods of apparently high and low activity, which seem to be tied to changes in atmospheric oxygen levels. During the Permian and the Triassic there was a major fall in atmospheric oxygen levels and consequently the fires were scant, nevertheless, during the remainder of the Mesozoic (Jurassic and Cretaceous periods), fire was increasingly important [5].
Thanks to the data found through these eras it has been possible to define the necessary ecological conditions for wildland fires, as they involve some specific parameters. The process of wildfire spread needs biomass fuels, but in addition to this there must be a dry season that converts potential flammable material to available fuels. Such seasonal variability climates may or may not be annual and may arise from different synoptic weather conditions. Thus, there is a link between the fire regimes of the past and the present. Indeed, the climatic conditions were and are the same.
Although the history of fire appears to have been continuous since plants invaded land, evidence that fire has actually altered the biogeography of landscapes and had major impacts on ecosystem function may be tied to the Late Tertiary [6]. During this era, it has been postulated that the spread of grasses during the more seasonal climate of the Late Tertiary was due to this increase antifire activity, which opened up woodlands and created favorable environments to grasslands. Although other factors such as the increased aridity have been invoked to explain the expansion of grassland, only the fire can prove that, since the expansion was possible because these grasses shifted their distribution to more mesic environments [7]. These cases suggest the re-sprouting of plants as an adaptation selected in response to fire. Another example to adaptation is the tree bark: it evolved in response to multiple environmental factors, including heat, cold, and disturbance such as fire. The genus Pinus is an outstanding example in which clearly fire is the driving force for thick bark, as those lineages prominent
12 in extreme climatic zone as deserts and timberlines, have the thinnest bark in the genus; all other pines dominate in fire prone landscapes. This radiation very likely began in the Cretaceous and continued through the Tertiary, suggesting that fire was an important ecosystem process throughout these periods [6].
2.1.2 Human Era
The early hominids (genus Homo) appeared in eastern Africa about 2.5 mya, and fire has been closely integrated into many stages of their evolution. It is believed that the rise of Homo erectus from its more primitive ancestors was fueled by the ability to cook (that is, to use fire).
After that, these early hominids started moving out of Africa, distributing their available fire technology; indeed, fire promoted the spread of humans by allowing them to colonize colder environments and by protecting them from predators.
During the Paleolithic and Mesolithic ages, fire was used extensively for what has been termed “fire-stick farming technique” [8]. This technique uses fire for a variety of reason: clearing ground for human habits, facilitating travel, killing insects, hunting, regenerating plants food sources for both humans and livestock, and to combat other tribes. Learning the management of this technique generated deep impacts not only on fire regimes but also on the landscape vegetation pattern and biodiversity. Commonly, closed canopy shrublands and woodlands were opened or entirely displaced by fast-growing species that provided greater seed resources, travel, hunting and planting opportunities. The spread of humans, perhaps at the same time with climatic changes, contributed to disappearance of mega-fauna (mammoths and other large herbivores) [9]. Extinction of mega-herbivores have resulted in fuel buildup and the consequent change in fire activity. For this reason, “fire-stick farming technique” was probably necessary after the mega-fauna extinction, not only to open up closed woodlands and subsequently habitable environments but also to reduce catastrophic fires that would pose a risk to humans.
The Neolithic agricultural revolution required fire to alter the natural vegetation form perennial that were dominating the landscapes. It has been postulated that people preferred to live in fire prone places because the burned land gave advantages for hunting, foraging, cultivation, and livestock. Even today, many agricultural and forestry techniques require fire. These activities have halted with the rise of agriculture. Agriculture has tended to limit fuels on many landscapes due to the increasing humans’ population through history. Furthermore, farming contributes to disrupt fuel’s continuity for agriculture lands and farm animals.
At global scale, both climatic and anthropogenic factors are needed to explain variations in global biomass burning over the last two millennia.
From 1 AD to approximately 1750 AD there have been found fewer charcoal sediments, this has attributed to a Little Ice Age. This decrease of charcoal sediment meaning increased land area dedicated to agriculture and exponential increases in world population [10].
The humans have affected fire regimes for millennia. Indeed, in mid latitudes, there are clear and consistent fire-regime changes as hunting and gathering societies, although these changes may have occurred at different times in different parts of the world.
2.1.3 Modern World
While humans have altered fire regimes since their early history. There have been marked by rapid-fire regime changes as a result of significant shifts in human population, particularly with respect to growth, socioeconomic factors, and land management.
During the 20th century, fire regimes in temperate latitudes has changed in different ways related to
both ecosystem characteristics and changes in land use. In southern Europe, industrialization led to people’s movement from rural areas into industrial centers. The sudden abandonment of farms, concomitant reduction in livestock grazing pressure (without replacement by natural grazers) and the consequent growth of tree plantations (mainly dense coniferous stands), has greatly increased fuel buildup, resulting in anomalously large and catastrophic wildfires, as reflected in the great increase in the last few decades in the amount of area burnt annually [11].
Over the same period, western US forests have also experienced an increase in hazardous fuels because of a highly effective fire suppression policy that excluded fires for much of the 20th century
[11]. This result, with questionable logging practices, has caused unusually high fuel accumulation. Historic high-frequency, low-severity surface fire regimes are now being replaced with low-frequency, high-intensity crown fires that are outside the historical range of variability for these ecosystems. In contrast, in the eastern United States, fire suppression has shifted oak and pine woodlands to mesophotic hardwoods, consequently reducing flammability and fire activity [12].
At the same time, in Europe, North America, Australia, and elsewhere, urban areas have expanded into wildland areas, producing more ignition sources (arson and accidental) and exposing more people to wildfires. Where populations have expanded into naturally high-intensity crown fire ecosystems, such as in many Mediterranean-climate regions, the result has often been catastrophic. Population
14 expansion into these fire-prone, crown-fire ecosystems has also had highly undesirable impacts on natural resources.
The replacing native woody vegetation with alien herbaceous species has destabilized these ecosystems in a multitude of ways (e.g., the reforestation of Portuguese forest with Eucalyptus has brought changes on fauna, soil and vegetation [13] [14] [15]) . These changes may reduce the habitat for native fauna, extend the length of the fire season, alter the functions plant types from deep-rooted shrubs to shallow-rooted grasses that affect the watershed stability.
The events that placed wildfires in a global context during 20th century have been the Indonesian fires:
during the burning, the growth rate of carbon dioxide emitted into the atmosphere doubled and reached the highest levels on record; carbon emissions from these fires made up 13% to 40% of global mean annual emissions from fossil fuels, yet they came from a relatively small area of the world [16]. The effects of these large wildfires on biodiversity and other natural resources are yet to be fully assessed. Fires as in Indonesia took place also in Yellowstone park (USA) and in Australia. These events put fire science on an upward trajectory leading to substantial changes in our understanding of fire as a natural ecosystem process. Theses histories have shown that humans have left a wide footprint on natural fire regimes in all corners of the globe.
2.2 Causes of Wildfires Ignition
As abovementioned, the fire is the rapid oxidation of a material in the exothermic chemical process of combustion and the factors for the physical process of fire are three (Figure: 2.1): fuel, oxygen and heat.
Figure 2. 1: Fire Triangle
In the past, the causes of forest fire were very different from the current ones, though the percentage of fires is approximately the same. In the world, the fires are not a calamity or fatality problem but an anthropogenic consequence which depends on voluntary and involuntary behavior. Indeed, the natural causes do not justify the high percentage of fires, so they are negligible. The 98÷99% of the Fires are caused by human, therefore it is not an unpredictable event but a recurrent event [17].
2.2.1 Causes and Motivations
The causes of fire are the same in every European country, they are described on Eurostat and are the following:
- Natural causes, like lightnings, volcanic eruptions and auto combustion;
- Negligent causes or involuntary, the causes do not depend directly on the human actions; - Malicious causes or voluntary, the causes depend directly on the human actions;
- Unknow causes.
2.2.1.1 Natural Causes
Among the natural causes there are some very rare such as the fall of meteorite and the rock spark during the rolling and there are causes less rare such as volcanic eruptions, lightnings and auto combustions [18].
The lightnings represent the 1÷2% of causes in Italy, while in other countries, as Canada and USA, lightnings are the 60% of the cases, being a relevant problem [18].
16 The auto-combustion is less than 1% in nature; indeed it is very rare and regardless of high temperature. On the other side, the industrial sector represents about 8% of causes. The main auto-combustion industrial materials are wood, carbon, oils, cotton and silk.
2.2.1.2 Negligence
The negligent causes are due to distractions or actions made without the intent to cause damage. The causes in literature are as the following:
- Agriculture: the highest negligence is found in agriculture. The frequency of fires changes with the place or region. At the beginning, the fire is under control of the farmer, but then he loses the control and the fire spread everywhere. The main causes of this kind of accident are the wind and the farmer’s scarce awareness of risk. To decrease the percentage of this negligence-induced fires, the local authorities needed much harder laws (i.e. forbid to burn), much controls on the agricultural areas and collect much more information;
- Recreational activities and indirect ignition. There are two kind of ignition: fires spreads from barbecue gas stove or from cigarettes thrown down from cars or during a walk. The first is much rare than the second cause.
The fires spread from barbecue can decrease with more greatest controls on barbeque areas and also with attention signals (Figure: 2.2) and proper equipment.
The cigarettes thrown down from cars or during a walk represent a very common problem. Despite its frequency, people underestimate this problem even though there are the right signals (Figure: 2.2). To decrease this problem, it has been improved the control on the risk areas and sensibilization campaigns;
Figure 2. 2: Signal of fire hazard
- Landfill sites: this case is very similar to the farmer’ one, because the fire can get out of control and spread everywhere. It is not a very common problem, but it is rather dangerous in the illegal landfills because there are not controls and the problem is not immediately recognizable. In order to decrease the problem, is of the outmost importance to close every illegal landfill;
- Power line: this source of spread is common during windy days, since the lines can break, or the pylons can fall. Another cause is when the vegetation touches the line because the humidity/water of plants can make a circuit-breaker. Usually, the low power lines cannot produce fire while the medium and high-power lines can. To decrease this problem, it can be improved the control along the power line to check its conditions and the surrounding vegetation;
- Train line: it is not a common cause indeed, but when a train breaks the spark can start a fire. To decrease this problem the excess of vegetation can be removed.
2.2.1.3 Malicious Causes
Malicious causes depend directly on the human actions. People set fires for their interests and they do not think about the environment consequences. The cases in literature are the following [18]:
- Renewal of pastor land: some shepherds burn pastures to eliminate parasites and chopping weeds on their land. Other shepherds burn the pastures to recriminate an area or to do damages to another pastures. In Italy, these causes are typical in Sardinia Region where the sheep farming is very important for the economy of the region;
- Recovery of agricultural land: when vegetation covers an agricultural land, some farmers burn the vegetation cover to eliminate it, in this way they can reuse the land to their activities; - Fire industry: some people used the fire as a tool to create jobs. It is common in Italy, USA and
Spanish but it is expanding also in other countries. Some people set fires with the aim to increase the frequency of fires in this way that the regions, or provinces, or civil protection must recruit new employees. This is a complex issue since these persons, with a reckless behavior, create significant damage to the moreover set people in danger;
- Protected areas: the problem of fires in the protected areas is very common in Spain []. Usually people trigger fires for some reasons: less economic value of building land, fear of much controls of breeding, hunting and forest activities, no information about advantages brought by protected areas (tourism). The solution is to let people be aware of the real potential of protect areas by local initiatives;
- Building opportunity: burn the forest to build. It is not a common problem in Italy, thanks to the law (art. 10, law 353/2000) which has classified the lands such as buildable and not buildable. In other country like Greece, the building opportunity is one of the main causes of fires. The reason to set fire to build comes from the fact that, often, after the fire occurs a requalification [18];
18 - Pyromania: this is uncontrollable impulse and practice of setting things on fire. This instinct sometimes is enhanced by mass-media, since the arsonist sees to trigger fires such as a mission against the authority and where he must not be discovered. Accusing arsonists to arson is not correct because they are psychopaths, and this create in their mind the criminal will [18].
2.3 Fire Spread
The previous chapter showed that the main causes of forest fires are caused by human action but, it is also known that the possibility of starting a fire depends on physical factors like vegetation cover and status, local topography and meteorology.
Forest fires start and propagate according to natural laws. The propagation of forest fire is central to the research and management of forest fires. It is therefore important to have some knowledge about the fire behavior and its spreading factors [19].
2.3.1 Development of a Forest Fire
The forest fires have different stages as: ignition, spread, decay and extinction. If the attention is focused on the place where the wildfire triggers, it is possible identify the succession of the events which are represented schematically in Figure 2.3 [20].
Figure 2. 3: Fire growth, spread and decay [20]
It has been assumed that the fuel is in “self-sustained combustion” without flames at the ignition phase.
The growth phase corresponds to the passage of slow combustion to flaming. It corresponds to the evolution of the flaming reaction from the material near the ground surface to the upper layers of the
20 vegetation (to the foliage of the tree canopies). This type of fire propagation regime is also called crown fire propagation.
At different stages the fire may decay to a lower regime until total fire extinction. In general a crown fire will decay and propagate as a surface fire, with a flaming fire front. If the flames continue to decay the fire may propagate as a ground fire and finally, when glowing combustion is extinguished, the fire process finishes.
The above described process of growth and decay is not a closed one, in the sense that at a given place a decaying ground fire may grow and spread again as a flaming fire or even experience a growth and propagate as a crown fire at a later stage [20].
2.3.2 Main Types of Fire Spread
During the time steps of forest fires, the fire front can have different configurations; these depends on the spread factors. First, fire spread goes in every direction and then thanks to various factors the fire front (or head) grows. The spread depends on wind and/or slope. The fire front can be identified in three parts:
- Fire front or head: it is perpendicular to wind direction; - Side of the fire: it is parallel to wind direction;
- Tail of fire: it goes along the opposite direction of wind.
On the head the temperature and the speed of fire is higher than the side and the tail [18].
The fire front can be identified with three main stable regimes of fire propagation that are involved in the combustion process [20]:
- Ground fire (Figure 2.4);
- Surface fire (Figure 2.5);
Figure 2. 5: Surface fire
- Crown fire (Figure 2.6).
Figure 2. 6: Crown fire
Ground fire usually burn without flame in the organic layer above the mineral soil. Its propagation is very slow and although it does not pose a great threat to the upper layers of the vegetation cover, it can produce considerable damage to the soil, given their large residence time. In some particular conditions this ground fire can have an initial growth and becomes a flaming surface fire. This is also quite common during the decaying phase of fires that are not completely extinguished they may rekindle and start another loop in the fire development process.
If the conditions are favorable, a surface fire propagating under tree canopies may extend to the upper layers of the crown foliage. This fire can torch a single tree or a group of trees. If there is horizontal continuity in the canopies and if the foliage moisture content is below a given threshold, a sustained crown fire propagation regime will be achieved. Given the fact that the tops of the tree canopies are exposed to higher wind velocities this crown fire may propagate with very high rate of spread. Under very strong winds this intense fire may experience high rate of spread and has the capacity of destroying large areas of forest land and is very difficult to suppress. It is found that usually crown fire
22 does not burn uniformly large areas of the forest, tending to form more or less heterogeneous patterns, due to the complex interaction of the convective flow and the tree canopies.
The fire front can be identified with another instable regime of fire propagation that is involved in the combustion process: the spot fire [21]. To understand the factors that influence spotting, it has been considered the life cycle of an ember or fire brand. The ember starts as a leaf or a larger piece of fuel that was partially consumed. It may originate on the ground, in the understory, or in the canopy. The air flux associated with the fire, lifts the ember up into the fire’s plume and throw it out from fire. When the ember gets out, the winds continue to push it horizontally or/and vertically. All through this journey, the ember continues to burn, losing mass and getting smaller. Eventually, the ember reaches the ground or perhaps it comes to rest in a tree canopy or understory vegetation. If it lands in flammable fuel, it may ignite that fuel, but only if the ember has enough energy to dry and heat up that fuel; drying and heating may take some time, resulting in an ignition delay. During the fire it is common to find several embers in the air. The size, shape, and number of embers depend on the fuel type and the intensity of the fire. The zone where the embers fall down has no definite size, it depends on the fire’s rate of spread, the fuel moisture, and, again, the fuel type. However, in this zone there is a chance for embers to ignite a new fire, as abovementioned (Figure: 2.7).
2.3.3 Main Factors Affecting Fire Spread
The physical factors which have a significant influence on the initiation and development of forest fires are usually grouped into three categories [20] (Figure: 2.8):
Figure 2. 8: Analogy between fire triangle and factors affecting fire spread
- Weather, meteorology: meteorological conditions are the most changeable factor in the fire propagation process. The most relevant parameters of the weather are the following: air temperature, humidity, precipitation, solar radiation, atmospheric stability, wind velocity and direction. The first four parameters have important influence on the moisture content of the fuel particles and are therefore related to the meteorological fire danger level. Some of these factors have a cumulative effect on the fire danger level. Wind patterns are mostly associated to fire spread conditions. Wind is recognized so far to be the most important factor in the entire problem of forest fire propagation. Given the spatial and temporal variability of wind, in practice it is not possible to have a uniform and stable conditions of propagation for any measurable period of time. The ability to estimate wind distribution near the vegetation surface and its time evolution is therefore of utmost importance to deal with the one of fire propagation (Figure: 2.9);
- Topography: the terrain configuration at the location of the fire, namely its altitude, slope, solar exposition and the overall surroundings determine the type of climate, vegetation cover and the wind pattern near the ground. For a given fuel the rate of spread of downslope propagating fires is quite low and practically constant, while the rate of spread of a fire front increases with the slope (Figure: 2.9);
- Fuel, vegetation: forest fires consume parts of vegetation which can have different forms and spatial arrangements, constituting a solid porous fuel bed with one or more layers (Figure: 2.9). The parts of the plants that participate in the propagation of the majority of forest fires are the fine particles, for which there is a minimum dimension (thickness or diameter) of less
24 than 6 mm. Only in very intense fires will larger particles burn during the spread of the fire front, although they may be consumed after its passage.
It is usual to consider three layers of fuel particles:
(a) The ground layer, with organic residues and decomposing litter, just above the mineral soil;
(b) The surface layer, consisting of the fuel on or in the close vicinity to the ground surface: litter, herbaceous, shrubs and small trees;
(c) The canopy layer, it formed by the foliage of the trees.
Each one of these layers can be characterized globally by its height or thickness, porosity, fuel load, and vertical and horizontal continuity.
Each layer is usually a mixture of particles of different species, sizes and shapes that may be alive or dead. The water or moisture content of fuel particles act as a heat sink or even as a chemical inhibitor in the pyrolysis process and therefore have a major influence on the fire ignition and fire spread properties. The moisture content of fuel particles depends greatly on the long and short term meteorological conditions; dead fine fuels particles may significantly change their moisture content in a period of few hours, while heavier or living particles require longer time periods.
2.4 Forest Fire Consequences on Ecosystem
As it has seen, the wildfires birth, grow, decay and die. After fires extinction there are many problems due by their passage. These have a very important role in the public and ecological safety and in the landscape of environmental heritages. These aspects are increasingly important in the modern society. The fires have important impact to many aspects as economy, environment and safety. These aspects have consequences on people’s lives and on the society.
This part will focus on the ecological consequence and in the following chapters the economy, safety and consequence of wildfires are taken into consideration.
2.4.1 Gas Emissions in the Atmosphere
One of the consequences of forest fires are the emissions of gasses in the atmosphere. These arise from wood combustion with vegetal oils or resins enclosed in the tree or on other plants. The most emitted gasses are carbon dioxide (CO2) and carbon monoxide (CO) [18].
With a slow fire front, the combustion is complete, instead with fast fire front the combustion is incomplete because with the fast fire front the flames pass quickly and the trees do not burn completely. For this reason, the slow combustion is eight times slower than the fast one. The mass of inquinate depends on the fuel burnt.
The chemical process resulting from forest fires can change the chemical status of atmosphere. The CO2 and CO gasses are one of the causes of climate change or global warming. Having said that, it is
possible suggest that the fires influence the climate and the climate influences the fires. Indeed, the frequency of the fires is changing with the climate change. This highlights as the climate change, it modifies the water level in the plants and thus the fire regime changes. Another consequence of the increase of CO2 in the atmosphere, is the improved flammability of plants and trees and consequently
the frequency of fires. All of these changes create a movement shift of the vegetation with latitude of about 500 – 1000 km in 200 – 500 years [18].
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2.4.2 Effects on the Soil
The fires could have many effects/impacts on soil in different environments because these depend on the kind of soil, forest fires, season, environment conditions before the forest fire (it was raining, windy, arid or when there was the last forest fire). The changes caused by fires are related to the intensity of fires. These are, usually, low to moderate with moderate fire, and high during the hot and arid season. In order to assess soil’s heating, the fires can be classified on the basis of their intensity as follow:
- Low severity fires; - High severity fires.
Fire impacts on soil properties can be direct or indirect [22].
Direct impacts are related to heat. With the exception of smoldering fires and burning logs and piles, the direct impact of fire on soil properties is usually short because soils are poor conductors of energy. The heating induced by fire is restricted to the first few centimeters of the soil. The exact effects depends on the type of soil, texture, pre-fire conditions (moisture content), type and structure of vegetation (density and connectivity), the ecosystem, fire intensity, severity, and recurrence, meteorological conditions during the fire and topography (slope) that influences fire behavior. The indirect impacts of fire are related to the ash-bed effects, degree of vegetation recuperation, topography, post-fire weather patterns and post-fire management.
Low severity fires can have beneficial impacts on soil properties, since the reached temperatures are not high and the loss of nutrients by volatilization and smoke are reduced. Good examples of these types of fires are grassland fires or fires during the autumn and winter seasons. The impact on soil cover is minimal (the plants are not completely burned) and soil heating is negligible (the soil does not change in color), therefore, overland flow and soil erosion are reduced compared to high severity wildfires. As a consequence of the production of ash rich in carbon, there is an increase in soil organic matter, pH, electrical conductivity and extractable cations such as calcium, magnesium, sodium and some forms of nitrogen such as ammonia, important for vegetation recuperation. A potential negative impact of low severity fires is the production of hydrophobic ash that can temporarily increase soil-water repellency.
Contrary to low-severity fires, high-severity fires combust a large amount of fuel and have extremely negative impacts on soil. One of the most important impacts is the large reduction in soil coverage. High temperatures at the soil surface reduce the quantity of organic materials and induce important
transformations in organic matter composition. The major changes in soil organic matter composition occur at temperatures between 250 and 450 °C. However, high temperatures may increase aggregation as a consequence of recrystallization of some iron and aluminum oxyhydroxides, if present in the burned soil (Figure: 2.10). Fire can increase soil hydrophobicity as a consequence of the volatilization of hydrophobic compounds from organic matter that are condensed onto soil particulates, increasing water repellency. However, at high temperatures, hydrophobicity disappears. Below 175 °C no changes are observed in water repellency, with repellency increasing at temperatures around 200 °C. At temperatures between 280 and 400 °C hydrophobicity is destroyed. High severity fires can destroy hydrophobicity in previously water repellent soils [23].
Severe wildfires volatilize high amounts of carbon and nitrogen since these nutrients start to vaporize at temperatures of about 200 °C. Carbon and nitrogen are totally lost in soils that burned at temperatures higher than 550 °C (Figure: 2.10). Wildfire temperatures can be as high as 1100 °C, thus elements such as calcium, magnesium, aluminum or manganese that need higher temperatures to be volatilized can only be lost by evacuation with ash and smoke.
High severity fires increase soil pH because of organic acid denaturation and the increase of sodium and potassium oxides, carbonates and hydroxides and electrical conductivity as a consequence of the mineralization of organic matter. The increase in pH favors the solubility of some cations such as calcium, magnesium, sodium and potassium, and reduces others such as cooper and zinc (Figure: 2.10). Soil microbes are very sensitive to high severity wildfires, especially in the topsoil, where soil heating is more intense. The thermal shock induced by fire changes the activity, size and composition of the microbial biomass. At temperatures higher than 70 and 80 °C, the majority of the soil microbes are destroyed and at temperatures between 115 and 150 °C they disappear completely.
Pre-fire land use and management is a crucial aspect to understanding the degree of the impacts of a wildfire on soil. The highest wildfire severities and the highest environmental, economic and social damages occur in areas where there was a lack of management or in existing industrial plantations of Pinus and Eucalyptus. Soil degradation is high in these areas because of the impacts of the high temperatures on the volatilization of nutrients and negative impacts on soil biological and physical properties, which in turn will limit the capacity of the ecosystem to recover. Ecosystems with high biodiversity are less vulnerable to wildfire impacts. Post-fire impacts on soil degradation extent and magnitude depends on the fire history, environmental conditions of the fire affected area and the human management. Fire history has important implications on soil properties. For example, high fire frequencies increase the flammability of vegetation. This increases the vulnerability of those areas to wildfire occurrence creating a fire recurrence cycle that can be disastrous for soils in these ecosystems
28 and induce a negative trend in soil fertility. On the other hand, high fire recurrence may decrease soil water repellency, which can reduce overland flow and soil erosion. However, this may not be considered a positive, because the loss of organic matter is extremely negative for soil quality. Soil is much vulnerable to degradation on steep slopes, especially after high severity fires. Steep slopes are the most vulnerable to the effects of flames, especially if the fire line heads upslope, since convection of heat from the fire has the capacity to pre-heat the fuel, reducing moisture content before combustion. These effects are especially important on dry south facing slopes that are also the most vulnerable to soil erosion. This is aggravated by slow vegetation recovery. Post-fire wind and rainfall intensity influence the soil degradation in fire-affected areas [24][22][25][26][27]. Ashes and soil erosion and nutrient losses are high when intense rainfall (normally accompanied by strong winds) occurs in the period immediately after a fire. During this time, soils are very sensitive to any kind of disturbance. In this context, both excess and lack of rainfall may increase soil degradation in soils affected by a high severity fire. Low intensity rainfall events can be beneficial reducing soil degradation because the capacity to compact the soil and create sediment detachment is reduced, soil moisture increases rapidly, and soil water repellency is destroyed, facilitating water infiltration, input of nutrients from ash, and microbial and vegetative recovery (Figure: 2.10).
High fire severities affect seed abundance in the soil. This is especially observed when high temperatures are combined with prolonged periods of contact. Normally, there is a reduction in seed germination rate with increasing temperature, and at 300 °C most of the seeds are killed. This is intensified by the occurrence of drought periods. All these aspects contribute to soil degradation. To better understand the steps to arrive at hydrophobic soil after the fire passed, it can look at the Figure: 2.11. On section A (no fire) the soil doesn’t have damage and the water is absorbed by soil, on the step B the soil is burning and its properties began to change (it is becoming to be hydrophobic). In the last step, on C, the soil is completely burned, and it becomes completely hydrophobic. That can be good if the rainfalls, post forest fire, are not severe because the water increases the soil moisture and recovery the vegetative. Instead, the hydrophobic soil can be dangerous if there are severe rainfalls post forest fire because the rain if accompanied by strong winds can increase soil degradation.
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Figure 2. 11: Development of Hydrophobic Soil
2.4.3 Effects on the Vegetation
During the last years in the Mediterranean area, has been observed winder wildfires jointly with an increase in their frequency, leading to negative effects on the economy and ecology of southern Europe. The changes of soil usage, and vegetable cover, have affected the landscape (Figure: 2.12), these make favorable conditions for starting fires [28].
After the passage of forest fires, shrubs grow on the land and that increase the possibility of fires. If the fire spread through a continue and dense vegetation, this becomes uneven. Instead, if the fire spread through an uneven vegetation of shrubs, the vegetation become even. The right modification induced by fire on the landscape has been evaluated by the knowing of the kind of vegetations involved, the width of the fire and the consequence [18].
In the forest, where the fires are a recurring event, there is a natural selection of floras. The plants which have adapted to fire, developing regeneration and defense technique will grow back easier [29]. The defense techniques are: thick bark (it is like a thermal insulation), fast-growing during the first years of life to transport the crown beyond the ground fire area, low flammability, dead leaves with a fast decomposition in order accumulate too much fuel and reduce the probability of ground fires, to have woody seed to reduce the damage of high temperatures [18].
The plants have two kind of regeneration techniques: vegetative reproduction (the plants make a pollen) (Figure: 2.13) and seed reproduction (the plants make a seed that fall down on the ground) (Figure: 2.14).
Figure 2. 13:Vegetative reproduction
32 These two techniques depend on some factors like: fires characteristics, life environment of plants and the morphologic and ecophysiology of plants. Usually, the flora with a vegetative reproduction prevail over the plants with the seed reproduction in arid habitat. During the forest fire the plant, has a thermic shock and its grow stop. This occur even if the fire doesn’t directly touch the plant.
The regeneration techniques are not only for high vegetation. Indeed, the low vegetations use the spore germination or vegetable reproduction.
2.4.4 Effects on the Wildlife
The wildlife depends on vegetation, for the food and for dens and nests. Therefore, there are very important relationships between forest fires, vegetation and wildlife.
The fires can cause direct and indirect effects to fauna [18].
The direct effects due to the actions of flames and high temperatures are exhibited by the mobility of animals. These effects depend of the kind of fires, if the fires are fast enough, the deaths of animals will be higher than the one registered during a slow fire. Moreover, if the fires occur during the love season, the future density of animals will be low.
The indirect effects are very variable because they depend on the vegetation’s changes. The animals must adapt to habitat changes caused by forest fires.
2.5 Wildfire Management
As it has seen, the wildfires have their behavior and spread, these are influenced by environmental and weather characteristics. All forest fires have their ignition and extinction, they change the characteristics depending on the place where fires set and spread. In the same way, every consequence is specific of the place where the fire trigger and spread. Wildfires with their behavior are the only one natural hazard that affect human communities especially on the wildland-urban interface (WUI). Wildfires on the wildland-urban interface have as a result in thousands of homes burned and civilian fatalities. These forest fires are inevitable, but the destruction of homes, ecosystems, and lives is not. In order to reduce these risks, it is possible to propose a risk analysis to provide land management agencies, first responders, and affected communities who face the inevitability of wildfires the ability to reduce the potential for loss. It is possible consider the wildland-urban interface fire disasters as a wildfire control problem. Practically, all the risks analyses are developed on QGIS. These can follow different calculation models, and these can be of two different type:
- Risk analysis to find a risk maps;
- Risk analysis to decrease the wildfire risk on the wildland-urban interface.
Successful fire management depends on effective fire prevention, detection, and forecast, and with adequate fire reduction or suppression capacity of the forest fire. Geographical information systems (GIS) provide tools to create, transform, and combine georeferenced variables, which have better quality, higher reliability and flexibility to simulate the wildfires behaviors.
2.5.1 Risk Maps
A lot of countries suffer from forest fires. The high frequency at which forest fires occur in recent years reinforces the need for a better understanding of forest fire risks, given the importance of sustaining forest resources. The management of these disasters is of importance to both government authorities and the public. The fire management activity involves the strategic integration of several factors such as knowledge of fire regimes; probable fire effects; value-at-risk; level of forest protection required; cost of fire-related activities and prescribed fire technology into multiple-use planning; decision-making. Every analysis of geographical data with Geographic Information Systems (GIS) preserves the spatial dimension of variables being processed, because all transformations are performed cartographically. Therefore, GIS oriented toward fire risk mapping may portray the geographical location of those areas where risk factors are most severe. Fire protection programs may then be
34 spatially and temporally oriented to the areas labeled as having high risk [31]. Several GIS applications have been developed in the last decade to improve management of fire risk [32]. A GIS can spatially integrate several environmental variables, such as vegetation, topography and climatology which can cover the whole study area.
A Risk Map allows the evaluation of the potential loss in a certain hazard zone. The forest fire risk map is created multiplying the Hazard Map by the Potential Loss Map [33]. The final result is a raster file, which is like a model consisting of area with wildfire priorities. These areas are geolocated and classified according to their forest fire risk [34]. It could have five classes of risk, every class have its different color: very low risk (dark green), low risk (green), medium risk (yellow), high risk (orange), and very high risk (red) [33].
In Portugal, as in many other countries, it is mandatory that all the municipalities produce forest fire risk maps on an annual basis following the rules of the Portuguese Forest Authority (AFN – Autoridad Forestal Nacional), which is a governmental association. These rules are published in technical guide for forest fires management for municipalities. An example of fires management for a Portuguese municipality is [35] .
The majority of wildfires are caused by human activities. However, much wildfire research has focused on the biological and physical aspects of wildfire, with comparatively less attention given to the importance of socio-economic factors. With recent changes in human activity, potentially contributing to the increases in wildfire occurrence, it has increased the need to consider human activity in models of wildfire risk. A possible method to predict the human hazard on the forests is the method from Bayesian statistics [36], the weights of evidence (WofE) model. This can produce predictive maps of wildfire risk. The results of this method show that spatial patterns of wildfire ignition are strongly associated with human access to the natural landscape. The WofE model can also be useful for estimating future wildfire risk. This method is useful to optimize time, human resources and fire management funds in areas where urbanization is increasing the urban-forest interface and where human activity is an important cause of wildfire ignition [37].
2.5.2 Wildfire Risk on the Wildland-Urban Interface
During the past two decades, many parts of the globe have experienced significant, damaging wildfire events with increasing frequency [38]. High-value developed assets located in areas prone to wildfire hazards, along with more frequent, extreme weather events possibly caused by global climate change [39], have implications to society, national governments, and the global insurance industry. The land management agencies, first responders, and affected communities face the inevitability of wildfires by
doing what other institutions, both private and public, across sectors, have done in the face of complexity and uncertainty: turn to the principles of decision science and risk management. Similar to other forms of risk management, the management of wildfire risks begins with an assessment of the probability of a wildfire event and the vulnerability of highly valued resources and assets to wildfire [40]. Strategic risk management in the wildfire context involves many complicate factors, including:
- Many wildlands are historically predisposed to periodic fire;
- Wildfire is a spatial process: fuel continuity is critical in fire spread, and burned areas may be considerable distances from the ignition point;
- Many communities have developed within or adjacent to fire-prone ecosystems;
- Sociopolitical expectations regarding wildland fire management and community fire protection may not be realistic under current and expected future conditions [41].
These factors present challenges to wildfire risk mitigation. The risk mitigation opportunities can be on the private areas and/or the public areas. On the first areas, it is possible the implementation of mitigation measure of the home ignition, while it is possible reduce hazardous fuel loads and to use elements of early warning systems on the public areas.
The reduce of the home ignition susceptibility is usually done on the private areas by using a strategic risk assessment framework enables evaluation of how reducing home ignition potential and reducing fuel loads can affect various risk factors [42]. Applying such a framework requires an understanding of the relationship between extreme wildfires, home ignitions, and mitigation opportunities. The primary risk factors are probability of home exposure to flames and burning embers which vary geographically according to environmental and socioeconomic variables. Probability of home exposure to wildfire is in turn influenced by the occurrence of fire, the size and intensity of fire, and the presence of homes in fire-prone areas. Particularly common before of the home fire risk mitigation options are fuels reduction or the use of early warning systems on public lands. The two principal objectives for fuel treatment are to reduce the wildfire intensity and severity within private areas, and to reduce the probability of fire occurrence on public areas near the private areas by limiting fire spread rates and/or enhancing suppression effectiveness. However, fuel treatments will or sensors monitoring not stop or eliminate fires, but they will improve the areas so to have a less intense wildfire and to have a faster identification of forest fire. For every risk mitigation opportunity the initial step must be to identify the wildfire behavior conditions by QGIS. Modern fire suppression organizations are highly effective under all wildfire except for the most extreme [43]. In other words, effective treatments must be designed to reduce the fires and their conditions which make an extreme event.
36 The most important mitigation elements involve surface fuel removal by prescribed fire [44] and the monitoring of forest areas with high fire hazard [45]. The level of fire behavior change needed depends on the area of study. The fuel treatments are intended to reduce the probability of fire and to change the way fires move across the relevant landscape. The challenges to accomplishing landscape level modifications become almost intractable with dispersed residential development because the multiplicity of land ownership.
To appropriately analyze and mitigate WUI fire destruction risk, it should be also understood how wildfires cause home ignitions, and how disastrous home destruction occurs during wildfires. However, during the extreme wildfire conditions of WUI fire disasters, nonintuitively, most home destruction within residential developments occurs with low-intensity flame exposures [46]. The likelihood of home ignition during extreme wildfire conditions is principally determined by home’s materials, design, and maintenance in relation to its immediate surroundings [47]. Last, given a sustained home ignition, the probability of home destruction is influenced by the effectiveness of fire protection efforts in suppressing the structure fire. The disaster sequence shows that, although some WUI fire protection tactics might succeed, these standard response tactics fail to prevent residential fire disasters with highly ignitable communities. Areas of high-density suburban development can lead to additional fire risk through home-to-home ignition. Thus, effective fire protection depends on fire resistance of homes and fire vulnerability of environment around the houses during wildfires.
2.6 Coexist with Wildfire
The previous chapters have showed as the wildfires through their spread can cause several type of environment consequences. The wildfires with their behavior are the only one natural hazard that affect human communities and the ecosystems on which their depend. For other natural hazards, such as earthquakes, hurricanes and floods, there is much more emphasis on the identifications of vulnerabilities and adaptations [48]. Unless people’s view fires as an inevitable and natural process, it will continue to have serious consequences for both social and ecological systems. Over the past two decades, wildfires around the world have increasingly affected human values (for example, lives, views or sacred environments) and assets (for example, damage to homes or public infrastructure) and ecosystem services (for example, air quality). The prospective of widely increasing fire activity due to ongoing climate change, intensifies the need for a new path. Viewing fire-related problems in the context of coupled socioecological systems (SES), which explicitly recognize links between humans and their natural environments, provides insights into achieving a more sustainable coexistence with wildfire [30]. In this chapter, it will see the fire-prone ecosystems and fire effects on human communities.
It will focus on three regions where major fire-related losses have occurred in recent decades: the Mediterranean area, United States (US) and South America.
2.6.1 Europe, the Mediterranean Basin
In Europe, the fires are concentrated in the Mediterranean area: indeed, the average area burnt annually is 55000 ha in Europe and the 95% of this area is on Mediterranean basin. The most affected countries of this problem are Italy, French, Greece, Portugal and Spain [18].
Mediterranean landscapes have various shrub-lands and pine woodlands which alternate with extensive pastures, farmlands and abandoned agricultural fields. Management and traditional use of fire has strongly influenced historical landscape dynamics.
The southern and eastern regions are subject to land over-exploitation and reduction in vegetation cover that increases the risk of desertification and loss of ecosystem services. By contrast, ecosystem services are increasing fire hazards and losses over Mediterranean Europe (northern region) owing to rural depopulation and land-cover changes that are sometimes promoted through afforestation policies. Most shrublands and woodlands, in the northern region, are becoming dense enough to support climate-driven high-intensity crown fires.
