2. Materials and Methods
2.1. National Scale
- Settlements: Whether there is high or low population is a factor of maximum importance when configuring fire scenarios, as human lives are the top priority for protection in a fire. The information source used in this article is the settlement map (Mapa de Poblamientos) produced by TRAGSATEC from the coverage in Usos del Sistema de Información Geográfica de Parcelas Agrícolas (SIGPAC, 2005), which has been completed with information from the forest map of Spain (Mapa Forestal de España 1:50,000 (MFE50, 2007), both produced by the Spanish Ministry of the Environment (Ministerio de Medio Ambiente y Medio Rural y Marino). By contrasting the data from these two sources using GIS, 9 population/settlement types were obtained depending on type, density and territorial environment (agricultural, forest) (Table 1).
- Forest ecosystem propagation hazard: defined as the intrinsic propensity of a forest system to propagate fire and become a wildfire. It is estimated from (i) the fuel and forest vegetation model (determined by the degree of combustibility and flammability) and (ii) the physiography (slope dependent and interpreted through topography).The fuel and forest vegetation model established by Rothermel  is used. It has been adapted to Spanish forest systems by the Dirección General de Medio Natural y Política Forestal (MMAMRM), and includes 13 types of fuel models. Models 5, 8, 9, 10, 11, 12 and 13 have been defined as “low combustibility”, and models 1, 2, 3, 4 and 6 as “medium or high combustibility”. On the other hand, the results of the trials carried out in the INIA laboratory to classify plant species flammability have been used to determine which species display high flammability throughout the year or only in summer, which species display moderate or low flammability, and the remaining species . These two variables (combustibility and flammability) are then used to assess the fuel hazard using a decision matrix (Table 2).
- Predominantly agricultural areas with scarce forest presence. Habitats: large, concentrated nuclei. (Countryside, meadows, plains, corridors and intramontane lowlands).
- Predominantly forested areas with high/medium propagation capacity and low agricultural presence, scarcely populated. (Mountain massifs and ranges, south-western peneplains).
- Predominantly forested areas with medium propagation capacity and scarce population (Peneplains and piedmont with dehesa pastureland).
- Agroforest mosaic. Moderate propagation capacity and low population (Sierras and high lands, peneplain environments).
- Agroforest mosaic. High propagation capacity and densely populated (Southern sierras, Cantabrian rias and coastal areas).
- Predominantly forested areas with high/medium propagation capacity and minimum agricultural presence and population. (Sierras and mountain massifs).
- Forested sierras with low/medium propagation capacity.
- Predominantly urban areas.
2.2. Regional Scale
- Territorial context for vegetation (forest dynamics and agricultural abandonment dynamics): The variables used (proportion of forest, agricultural and non-productive land; proportion of abandoned farmland between 1990 and 2009) are grouped into 6 classes using a cluster analysis for land cover and dynamics. The intensity of agricultural abandonment compared with cultivated land is the main criterion differentiating situations corresponding to the 1st and 2nd generations.
- Interface between forest land and urban area: similarly, the drainage basins belonging to the 4th wildfire generation are identified by the land cover variables (% of urban area, % of dense forest land).
- Forest management: Calculated for each forest type (average values for each landscape unit).
3.1. Conceptual and Theoretical Foundation of Fire Scenarios
- National scale: the indicator used is propagation capacity, calculated as a function of flammability and combustibility of forest ecosystems, and slope gradient.
- Regional scale: propagation capacity is evaluated in more detail, by considering forest continuity and structure, as well as the extent of existing agricultural and unproductive land.
- Local scale: the indicators include the degree and continuity of vegetation, and its specific composition and structure, considering in particular the existence of WUI.
- National scale: size and morphology of urban areas and their connection with rural areas.
- Regional scale: density of urban occupancy, as well as the proportion, continuity and density of forested land at the interface between forest and urban areas.
- Local scale: description of WUI and their vulnerability to wildland fires.
3.2. Mapping and Characterization of National Fire Scenarios in Spain
3.3. Testing the Methodology for Identifying the Regional Fire Scenarios: Case Study—The Island of Mallorca
Conflicts of Interest
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|Urban environment||Urban areas of more than 50 ha|
|Settlement in forest area||Urban nuclei of 1–50 ha or more than 5 urban nuclei of under 1 ha in a 25 m buffer zone. More than 30% of the surrounding surface area (forest and agricultural) in a 1 m buffer zone is forest.|
|Settlement in agricultural area||Urban nuclei of 1–50 ha, or more than 5 urban nuclei of under 1 ha in a 25 m buffer zone. Less than 30% of the surrounding surface area (forest and agricultural) is forest in a 1 m buffer zone.|
|Scattered buildings in forest area||3–5 urban nuclei of under 1 ha in a 100 m buffer zone. More than 30% of the surrounding surface area (forest and agricultural) in a 1 m buffer zone is forest.|
|Scattered buildings in agricultural area||3–5 urban nuclei of under 1 ha in a 100 m buffer zone. Less than 30% of the surrounding surface area (forest and agricultural) in a 1 m buffer zone is forest.|
|Isolated buildings in forest area||1 or 2 urban nuclei of less than 1 ha in a 100 buffer zone. More than 30% of the surrounding surface area (forest and agricultural) in a 1 m buffer zone, is forest.|
|Isolated buildings in agricultural area||1 or 2 urban nuclei under 1 ha in a 100 m buffer zone. Less than 30% of the surrounding surface area (forest and agricultural) in a 1 m buffer zone is forest.|
|Unpopulated forest area||Forest area with no urban settlements.|
|Unpopulated agricultural area||Agricultural area with no urban settlements.|
|Low Combustibility||Medium and High Combustibility|
|Flammability||Low flammability||PC1 1||PC2 2|
|Physiographic Hazard||Slope Range|
|Wildfire Generation||Fuel||Wildfire Characteristics||Territorial and Temporal Context||Action|
|1st wildfire generation||Continuity of forest mass, low fuel load (grassland, meadows).||Long perimeters and high propagation speed.||Started in the late 1950–1960s, related to abandoned farmland.||Local response: increased accessibility to the land; linear prevention infrastructure (firebreaks).|
|2nd wildfire generation||Continuity of forest mass and increased fuel load (scrubland).||High intensity and high propagation speed; start of secondary ignition sites.||Started in the late 1970–1980s due to abandoning of farmland and traditional forest management.||Reduced access time (tracks, quick detection, forceful attack, water spots).|
|3rd wildfire generation||Homogeneous forests with high densities and vertical continuity.||Crown fires that overwhelm the tactical intervention capacity; multiple secondary ignition sites (advances jumping long distances). Large wildfires, more than 20,000 to 30,000 ha.||Prolonged lack of forest management (30–50 years); extinction of all low- and middle-intensity wildfires.||Extinction task forces admit their limits. Use of all extinction techniques. Strategic response: promotion of forest management and prescribed burnings; promotion of self-protection in estates; advance of opportunities (confinement and deceleration); more dynamic and flexible decision-making.|
|4th wildfire generation||Same as 3rd + estates with propagation capacity.||Same as 3rd (LWFs) + creation of multiple emergencies (in wildland-urban interfaces (WUI).||Same as 3rd + increase of scattered estates in forest land.||Same as 3rd + differentiation between strategic and tactical levels; decision making at lower levels.|
|5th wildfire generation||Same as 4th.||Same as 4th + simultaneity.||Same as 4th.||Same as 4th.|
|Defining Elements||Intervening Factors||Sources of Information|
|Propagation capacity||Fuel load and continuity|
|Cartography of fuel models (Forest Map)|
Digital Terrain Model (DTM)
|Wildfire characteristics||Intensity, propagation speed, simultaneity|
|Territorial context||Agricultural abandonment|
Intensity of forest management
Presence of wildland-urban interface (WUI)
|Crops and land use map|
National Forest Inventory
Settlement Map (TRAGSATEC)
|Driving Forces||Trends and Fire Behavior Effects|
|Ecosystem transition (from grass-fueled to woody-fueled fires)||In non-forested landscapes:|
Expansion of grass-dominated ecosystems, as a result of agricultural abandonment (higher fire spread: 1st generation of wildland fires)
Increase in understory fuels in open forests, as a result of grazing abandonment (higher fire intensity: 2nd generation of wildland fires)
In forested landscapes:
Increase of shrubland (regeneration of natural vegetation) and development of complex forest ecosystems: increase of fuel load and vertical continuity, as a result of land management abandonment (convective fire-type: 3rd generation)
|Increase of landscape fuel connectivity||Homogenous surfaces of the same fuel model after traditional landscape mosaic disappears (larger fire perimeters: 1st generation).|
|Urban sprawl||Development of WUI (higher fuel complexity: 4th generation|
Large and complex urban regions characterized as high risk areas with extremely rapid, virulent fire behavior (simultaneous large wildfires; megafires; 5th generation)
|Scale||Criteria for Definition of Fire Scenarios||Applied to Planning: Spatial Planning and Rural Development Policies||Applied to Planning : Wildland Fire and Civil Protection Policies|
|National (1:1,000,000)||General landscape configuration (relief and vegetation cover)|
Interaction between type of vegetation cover and settlement system.
|Characterize and differentiate land areas with regard to fires to enable different region-specific actions.|
Basis for establishing land development policies including fire risk management.
|Establish homogeneous fire prevention and extinction policies in large regional areas.|
|Regional (1:200,000–1:50,000)||Landscape patterns|
Trends in landscape changes
|More rational territorial model: to reduce settlement system vulnerability from proliferation of scattered settlements (WUI).|
Link major decisions on land use to fire regimes.
|Spatial basis for appropriate zoning for forest and fire management.|
|Local (1:25,000)||Definition of fire types (interaction of synoptic situations/topography/vegetation type) prone to develop into LWFs in each area||Risk maps: mandatory basis for detailed zoning by use.|
Management strategies to reduce vulnerability to specific hazards (damage mitigation).
|Establish management requirements for specific propagation modes.|
Pre-extinction actions (defence opportunities; reduction of propagation rate).
Mapping of suppression opportunities and priorities.
Involvement of general public in fire-related forest management.
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