Forestry & Forest Sciences · Forest Protection, Wildlife & Rangelands · also Fire Ecology and Management, Wildland Fire Management, Forest Fire Protection
How forest fires start and spread, their ecological roles and impacts, and how fire is prevented, detected, suppressed and used deliberately.
In the exams: ICAR AICE-JRF 59 Unit 8 (forest fires: causes, types, impacts, control); IFoS Forestry Paper II Section B (forest protection); NWCG qualifications (USA)
Fire is one of the most powerful forces shaping forests. In some ecosystems it is a natural and necessary process: many pine forests, savannas, eucalypt forests and boreal forests have burned regularly for millennia, and their species have evolved to survive or even depend on fire. In others, such as tropical rain forests and peat swamps, fire is rare in nature and highly destructive when it occurs. Almost everywhere, people now start most fires, through land clearing, agricultural burning, collection of non-timber products, hunting, carelessness and arson, and climate change is lengthening fire seasons and making extreme fire weather more frequent. Fire management, which combines prevention, detection, suppression and the deliberate use of fire, is therefore a core responsibility of foresters.
This subject covers the science and practice of forest fire: the fire triangle and the chemistry of combustion; fuels, their types, loads and moisture; fire behaviour, including rate of spread, intensity and flame length; the types of fire (ground, surface and crown); fire weather and fire danger rating systems; fire ecology and fire-adapted ecosystems; prevention and fire lines; detection by lookouts, patrols and satellites; suppression methods and the Incident Command System; prescribed and controlled burning; post-fire assessment and rehabilitation; and community-based fire management. Forest ecology and disturbance in general are treated in forest-ecology; climate change and its effects on fire weather in forests-climate-carbon; and the hydrological effects of fire in forest-hydrology-watershed.
In India, forest fires are a major cause of forest degradation, and the forest fire season in most regions runs through the dry months from about February to June. Most fires are surface fires, set by people, in dry deciduous forests, chir pine forests of the western Himalaya and areas of shifting cultivation in the north-east. Fire is examined in Unit 8 of the ICAR AICE-JRF forestry syllabus (forest fires: causes, types, impacts and control measures), in forest protection in Section B of Paper II of the Indian Forest Service forestry optional, and in the training of forest staff; in the United States, wildland fire qualifications are set by the National Wildfire Coordinating Group. Questions ask for the fire triangle, fuel classes and timelag, the types of fire, factors affecting fire behaviour, fire danger indices, control methods and organisation, and the ecological role of fire.
Fire is rapid oxidation of fuel with the release of heat and light. Three elements must be present: fuel (combustible material), oxygen (from the air) and heat (enough to raise the fuel to its ignition temperature). These form the fire triangle; remove any one and the fire goes out. Firefighting methods correspond to its sides: removing fuel (fire lines, clearing), excluding oxygen (smothering with soil or beating) and removing heat (cooling with water). A fourth element, the self-sustaining chemical chain reaction of combustion, is sometimes added to make a fire tetrahedron; some retardants and extinguishing agents act by interrupting it. For wildland fire behaviour, a different triangle is used: the fire behaviour triangle of fuel, weather and topography.
Combustion of wood and other plant fuels proceeds in phases. In the preheating phase, fuel ahead of the fire is heated; water is driven off and then, at higher temperatures, the fuel begins to decompose chemically (pyrolysis), releasing flammable gases. In the flaming phase, these gases ignite and burn above the fuel, producing visible flames and most of the heat; the charcoal left behind then burns more slowly. In the smouldering phase, fuels such as duff, peat and rotten logs burn without flame, at lower temperature, often for long periods, producing much smoke. The glowing phase is the final, flameless burning of charcoal. Flaming combustion dominates in fine, dry fuels; smouldering dominates in deep, compact organic layers, which can burn for days or months, as in peat fires.
Heat moves from burning fuel to unburned fuel in three ways. Conduction is transfer through a solid, which is slow in wood because wood is a poor conductor. Convection is transfer by moving hot gases; it carries heat upward into tree crowns and ahead of the fire with the wind, and is the main reason fires spread fastest upslope and downwind. Radiation is transfer by electromagnetic waves from the flames to nearby fuels, important in preheating fuel in front of the fire. A fourth mechanism, spotting, is the transport of burning embers (firebrands) by wind and convection columns, which can start new fires well ahead of the main front.
The energy released by burning a unit mass of fuel is its heat of combustion. For dry wood and similar plant fuels it is in the range of about 18 000 to 20 000 kJ/kg; allowing for the energy used to evaporate moisture and for incomplete combustion, a heat yield of about 18 000 kJ/kg is commonly used in fire behaviour calculations. This value enters the calculation of fireline intensity described in the fire behaviour chapter.
Wildland fuels are classified by their position. Ground fuels lie beneath the surface litter: duff (partly decomposed organic matter), roots, buried logs and peat; they burn mainly by smouldering. Surface fuels lie on or near the ground: litter of leaves and needles, grasses and herbs, low shrubs, seedlings and fallen woody material; most fires spread through them. Ladder fuels are vertically continuous fuels, such as shrubs, small trees and low branches, that carry fire from the surface into the crowns. Crown (aerial) fuels are the foliage and fine branches of the tree canopy. Understanding the strata explains how fires move from one layer to another and why removing ladder fuels reduces crown fire risk.
Several properties of fuels determine how they burn. Fuel load is the dry mass of fuel per unit area, expressed in t/ha or kg/m²; more fuel means more energy release. Fuel size is often expressed as the surface-area-to-volume ratio: fine fuels such as grass and needles have high ratios, heat and dry quickly and ignite easily, while large logs have low ratios. Fuel arrangement includes compactness (how tightly packed fuel is; loosely packed fuel burns faster because air reaches it) and continuity, horizontal and vertical (gaps break fire spread). Fuel chemistry also matters: resins, oils and waxes, as in pine needles and eucalypt leaves, increase flammability, while high mineral content reduces it. Fuel models group fuel complexes with similar properties so that fire behaviour can be predicted, such as the standard fuel models used in the United States with the Rothermel spread model.
Fuel moisture content, the mass of water as a percentage of the oven-dry mass of fuel, is the most important variable controlling ignition and spread. Dead fuels gain and lose moisture with the weather; the speed of this response depends on their size and is described by the timelag, the time needed for a fuel to lose about 63% of the difference between its initial moisture and the equilibrium moisture with the air. Dead fuels are grouped into timelag classes: 1-hour fuels (less than about 0.6 cm in diameter, such as grass, needles and fine twigs), 10-hour fuels (about 0.6 to 2.5 cm), 100-hour fuels (about 2.5 to 7.6 cm) and 1000-hour fuels (about 7.6 to 20 cm). Fine 1-hour fuels can dry within hours after rain and drive fire spread; large fuels reflect longer drought and control how much fuel is consumed. Each fuel type has a moisture of extinction, the moisture content above which fire will not spread through it. Live fuel moisture, in green foliage, is much higher and varies seasonally; low live fuel moisture during drought makes shrubs and crowns far more flammable.
In Indian forests, the main fuels are leaf litter of dry deciduous forests after leaf fall in the dry season, grasses in open forests and savannas, the needle litter of chir pine (Pinus roxburghii) in the western Himalaya, which forms thick, highly flammable layers, bamboo litter and dried culms after gregarious flowering, and slash from felling and shifting cultivation. Weeds such as Lantana camara form dense, flammable understoreys in many forests and act as ladder fuels. Reducing these fuels, by removing pine needles (which can also be collected for briquettes and energy), clearing weeds and controlled burning of fire lines, is a central part of fire prevention.
A free-burning fire spreading under wind or slope has a characteristic shape, roughly elliptical. The head is the fastest-spreading part, moving with the wind or upslope, with the highest intensity. The flanks are the sides, spreading more slowly. The rear or back is the part burning against the wind or downslope, slowly and with low intensity. Fingers are narrow extensions of the fire and pockets are unburned indentations between them. Spot fires are new fires started ahead of the main fire by firebrands. Knowing these parts matters for safety and suppression: the head is the most dangerous, and attack often starts from an anchor point at the rear and proceeds along the flanks.
Rate of spread is the speed at which the fire front advances, usually expressed in metres per minute or kilometres per hour. It depends on fuel (load, size, moisture, arrangement), weather (wind speed, temperature, humidity) and topography (slope and aspect). Wind tilts flames forward, increasing radiation and convection to unburned fuel, and is usually the most important factor in rapid spread. Slope has a similar effect: fire spreads faster upslope because flames are closer to the fuel above. A widely used rule of thumb from Australian research is that, on a given fuel, the rate of spread roughly doubles for each 10° increase in upslope gradient, and halves for each 10° downslope. Mathematical models, such as Rothermel's surface fire spread model (1972), used in the United States, predict rate of spread from fuel model, fuel moisture, wind and slope.
Fireline intensity, defined by Byram, is the rate of energy release per unit length of the fire front, in kilowatts per metre (kW/m): I = H × w × r, where H is the heat yield of the fuel (kJ/kg), w is the mass of fuel consumed per unit area (kg/m²) and r is the rate of spread (m/s). For example, with H = 18 000 kJ/kg, w = 0.8 kg/m² and r = 0.05 m/s (3 m/min), I = 720 kW/m. Fireline intensity is the most useful single measure for suppression planning and for predicting scorch height and tree damage. Very roughly, fires of less than a few hundred kW/m can be attacked directly by crews with hand tools; fires of several thousand kW/m are beyond direct attack, and crown fires may exceed tens of thousands of kW/m.
Flame length, the distance from the base of the flame to its tip measured along the flame, can be observed in the field and is related to fireline intensity. Byram's relationship is L = 0.0775 × I^0.46, with L in metres and I in kW/m; a fire of 720 kW/m has a flame length of about 1.6 m. Suppression guidelines in the United States relate flame length to tactics: fires with flames below about 1.2 m (4 ft) can generally be attacked at the head or flanks by people with hand tools; between about 1.2 and 2.4 m (4–8 ft) direct attack by hand crews at the head is too dangerous and machines, engines and aircraft are needed; above about 2.4 m, control efforts at the head are likely to be ineffective, and above about 3.4 m (11 ft) crowning, spotting and major runs are probable. Flame length should not be confused with flame height (the vertical extent), which is smaller when flames are tilted by wind or slope.
Ground fires burn in the organic layers beneath the surface litter, such as duff, roots and peat, mainly by smouldering. They spread slowly but can burn deeply and persist for weeks or months, killing roots and the cambium at the base of trees, and they are difficult to detect and extinguish because they burn underground. Peat fires in South-east Asia, especially in drained peatlands in Indonesia, release very large amounts of carbon and cause severe regional haze. Ground fires can re-emerge to start surface fires after the main fire appears to be out.
Surface fires burn in the litter, grasses, herbs, shrubs and small woody debris on the forest floor. They are the most common type of forest fire, including the great majority of forest fires in India. Their intensity varies from low, creeping fires in compact litter to fast, intense fires in dry grass and shrubs under wind. Low-intensity surface fires may cause little damage to mature, thick-barked trees but kill seedlings, saplings and regeneration, scorch the lower stems of trees (creating wounds through which decay fungi enter), consume litter and organic matter, and favour fire-tolerant grasses and weeds over time. Repeated annual surface fires are a major cause of regeneration failure and degradation in dry deciduous forests.
Crown fires burn through the canopy of trees. They usually develop from intense surface fires when ladder fuels carry flames into the crowns. A passive crown fire (torching) involves individual trees or groups of trees burning in their crowns, while the fire still depends on the surface fire for spread. An active (running) crown fire spreads through the canopy as a continuous front, linked with the surface fire; it requires dense, continuous crown fuel and strong winds or steep slopes. An independent crown fire spreads through crowns without support from the surface fire, which is rare. Crown fires are most common in dense conifer forests, such as boreal and some temperate pine forests, and in eucalypt forests in Australia; they are extremely intense, fast, prone to spotting and largely beyond direct control. Van Wagner's criteria relate crown fire initiation to surface fireline intensity, crown base height and foliar moisture, and crown fire spread to crown bulk density.
The type of fire determines effects and control strategies. Ground fires require digging, flooding or trenching around the burning area and long mop-up. Surface fires can usually be controlled by fire lines, beating and water, and their risk is reduced by fuel management and controlled burning. Crown fires are controlled mainly by indirect methods, wide breaks and favourable changes in weather; their risk is reduced by thinning, pruning lower branches and removing ladder fuels to raise the crown base height and reduce crown continuity.
Weather controls fuel moisture and fire behaviour from day to day. Air temperature affects fuel temperature and drying; relative humidity governs the moisture of fine dead fuels, which can change within hours; wind supplies oxygen, tilts flames, carries firebrands and is usually the strongest driver of spread; precipitation wets fuels, and its amount, duration and time since the last rain determine how dry the larger fuels and organic layers become. Atmospheric stability determines whether smoke and heat rise freely: unstable air allows tall convection columns and erratic fire behaviour, while stable air suppresses columns. Local winds, such as daily upslope and downslope winds in mountains, and dry, warm föhn-type winds, are important. Longer-term drought dries large fuels and organic soils and is tracked by drought indices such as the Keetch-Byram Drought Index, which ranges from 0 (saturated) to 800 (extreme drought).
Fire danger rating systems combine weather and fuel information into indices that describe the potential for fires to start, spread and resist control. They are used to decide when to increase readiness, restrict activities, ban burning and position resources. The Canadian Forest Fire Weather Index (FWI) System, widely used internationally, calculates three fuel moisture codes (the Fine Fuel Moisture Code for litter, the Duff Moisture Code for loosely compacted organic layers and the Drought Code for deep compact organic layers) and three fire behaviour indices (the Initial Spread Index, combining fine fuel moisture and wind; the Buildup Index, combining the duff and drought codes; and the Fire Weather Index, combining these into a measure of fire intensity). The United States uses the National Fire Danger Rating System. Australia long used the McArthur Forest and Grassland Fire Danger Indices and, from 2022, a national Australian Fire Danger Rating System with four public levels: Moderate, High, Extreme and Catastrophic.
In India, the Forest Survey of India operates a forest fire alert system that uses satellite detections of active fires and disseminates alerts to forest officers and registered users, and has developed pre-fire advisories based on weather and fuel conditions. State forest departments declare fire seasons and use fire danger information to deploy fire watchers and crews. Fire danger in most of India peaks in the hot, dry pre-monsoon months, from about March to May, when deciduous litter is dry, humidity is low and winds are strong.
Fire weather forecasts and danger ratings allow managers to anticipate dangerous days, issue public warnings, close forests or restrict activities such as burning, pre-position crews and aircraft, and plan prescribed burns for safe conditions. Climate change is increasing the number of days with high fire danger in many regions, which is changing the length of fire seasons and the demands on fire management (see forests-climate-carbon).
A fire regime describes the pattern of fire in an ecosystem over long periods: its frequency (how often fire returns, or its return interval), intensity (energy released), severity (its ecological effect, such as tree mortality or soil damage), season, size, spatial pattern and type (ground, surface or crown). Broad types include frequent low-severity surface fire regimes, as in many open pine forests and savannas; mixed-severity regimes; and infrequent high-severity, stand-replacing regimes, as in many boreal forests and some temperate conifer forests. Intensity and severity are distinct: an intense grass fire may have low severity for trees, while a slow smouldering fire may have high severity for soil and roots.
Plants in fire-prone ecosystems show traits that allow them to survive or regenerate after fire. Thick, insulating bark protects the cambium, as in longleaf pine, ponderosa pine, chir pine and many savanna trees. Resprouting from buds protected under bark (epicormic buds) or from underground organs such as lignotubers and root crowns allows recovery after crowns are scorched; many eucalypts resprout in this way. Serotiny, in which seeds are held in closed cones or fruits that open after fire, ensures a seed rain onto the freshly burned seedbed, as in lodgepole pine, jack pine and many Banksia species. Fire-stimulated germination, triggered by heat or chemicals in smoke, is common in fire-prone shrublands. Self-pruning of lower branches and high crown bases reduce the risk of crown fire. Some grasses promote frequent fires that favour them over trees.
Tropical rain forests, cloud forests, peat swamp forests and many temperate rain forests rarely burn naturally, and their species lack fire adaptations: thin bark, dense shade and moist microclimate are typical. When they do burn, often because of clearing, drainage, logging or drought, fire can kill many trees, open the canopy and dry the forest, making later fires more likely; repeated fires can convert forest to grassland or scrub. Fire in the Amazon and in the peat forests of Indonesia during drought years has shown how fire can drive forest loss and large carbon emissions.
In ecosystems adapted to frequent low-severity fire, a century of fire exclusion, as in many dry pine forests of the western United States, allowed dense understoreys and fuel to accumulate, changing species composition and leading to larger, more severe fires than before. This experience led to policies of restoring fire through prescribed burning and allowing some natural fires to burn under suitable conditions. In India, the role of fire is debated: frequent anthropogenic fires degrade many forests, but some ecosystems, such as savannas and certain dry forests and grasslands, have long fire histories, and complete exclusion may not always be ecologically appropriate. Management must therefore be based on the fire ecology of each forest type and on objectives.
Prevention starts with knowing why fires start. Natural ignitions, mainly lightning, are important in boreal forests and parts of North America and Australia. In South Asia and most tropical regions, the great majority of fires are caused by people: burning to clear land or prepare fields, shifting cultivation, burning grass to encourage fresh growth for livestock, collecting non-timber products such as mahua flowers and tendu leaves (where the forest floor is burned to make collection easier or to stimulate new leaves), honey collection, hunting, careless disposal of cigarettes and campfires, sparks from vehicles and power lines, and deliberate arson, sometimes linked to conflicts over forest use.
Prevention measures address both people and fuels. Education and awareness campaigns, through schools, village meetings, media and forest staff, explain the damage fires cause and safe practices. Regulation includes restricting or banning burning and access during high danger periods, controlling the use of fire for agriculture and requiring permits. Engaging communities through joint forest management, incentives and rewards for fire-free forests gives local people a stake in prevention (see the community chapter). Fuel management reduces the amount and continuity of fuel: removing litter and pine needles from strategic areas, clearing weeds such as Lantana, thinning and pruning to remove ladder fuels, grazing in some areas, and controlled burning.
A fire line (firebreak) is a strip of land cleared of flammable material, or of vegetation down to mineral soil, to stop or slow the spread of fire and to provide access and a base for suppression. In Indian forestry, a network of fire lines of different widths is maintained in many forests: wider main or external fire lines along boundaries and major ridges, and narrower internal lines dividing the forest into blocks. Fire lines are cleared and their debris burned under controlled conditions before the fire season, so that the cleared strip itself cannot carry fire. Natural features such as streams, roads and rocky areas are incorporated into the network. Fuel breaks, in which vegetation is thinned and pruned rather than cleared to bare soil, and green belts of less flammable species are alternatives that reduce erosion compared with bare fire lines.
Fire lines stop low- to moderate-intensity surface fires but cannot stop high-intensity fires with strong winds, crown fires or fires that spot across them. They need maintenance every year, can cause erosion on slopes, and are only effective if staff and equipment are available to use them during fires. They are best seen as part of a system that includes fuel management, detection, rapid response and community involvement.
The size and cost of a fire depend heavily on how quickly it is detected and attacked. A small fire found in its first minutes can be put out by a few people; the same fire found hours later may need large crews and aircraft. Detection systems therefore aim to find fires early, locate them accurately and report them quickly to those who will respond.
Traditional detection relies on lookout towers placed on high points with wide views, staffed during the fire season by watchers who report smoke with its bearing; bearings from two or more towers fix the fire's location by cross-bearings. Patrols on foot, motorcycle or vehicle cover areas not visible from towers. Fire watchers employed by forest departments in India during the fire season combine patrolling, detection and initial attack. Aerial patrols by light aircraft are used in some countries, especially after lightning storms. Reports from the public and local communities are a major source of detection everywhere, and telephone and mobile reporting systems make them faster.
Satellites detect active fires by the strong thermal infrared signal from burning areas. The MODIS sensors on the Terra and Aqua satellites, with a resolution of about 1 km for fire detection, and the VIIRS sensors, with a resolution of 375 m, provide near-real-time active fire data several times a day, freely available through systems such as NASA's Fire Information for Resource Management System (FIRMS). Geostationary weather satellites detect fires every few minutes at coarser resolution. Satellite data are also used after fires to map burned areas. In India, the Forest Survey of India's forest fire alert system processes satellite fire detections, overlays them on forest boundaries and sends alerts by SMS and email to forest officers and registered community members, enabling rapid ground checks and response.
Automated camera systems mounted on towers, with software that detects smoke, are increasingly used in Europe, North America and elsewhere, covering large areas without permanent staff. Sensor networks and drones supplement them. Effective detection systems integrate all sources, satellites, cameras, towers, patrols and public reports, into a coordination centre that verifies reports, dispatches resources and tracks fires, linked to fire danger information so that detection effort is concentrated on high-danger days.
Suppression aims to stop the spread of a fire and extinguish it. Direct attack works at the fire edge, cooling, smothering or removing fuel immediately adjacent to the burning edge, using beaters, hand tools, water and sometimes retardants; it is suitable for low-intensity fires and is safest when crews work from an anchor point with one foot in the burned area. Indirect attack builds a control line some distance ahead of or beside the fire, using natural barriers, roads or constructed lines, and then removes the fuel between the line and the fire by burning out or backfiring; it is used when the fire is too intense or fast for direct attack. Parallel attack builds a line close to and parallel with the fire edge, burning out the strip between. Every attack should begin from an anchor point, a secure location such as a road, stream or burned area, to prevent being outflanked.
Hand tools include fire beaters or flappers for beating out flames in grass and litter, rakes, shovels, axes and combination tools for scraping and cutting fire lines down to mineral soil. Water is applied from backpack pumps, engines (fire trucks) and aircraft; additives such as foams and wetting agents improve its effectiveness. Long-term retardants, usually based on ammonium phosphate salts, are dropped from aircraft ahead of fires to slow spread. Bulldozers and other machines construct wide control lines rapidly where terrain allows. Backfiring (lighting fire from a control line toward an approaching main fire) and burning out (removing fuel between a control line and the fire) are powerful but dangerous techniques requiring skill and authority. After the fire is contained, mop-up extinguishes or removes burning material near the control line to prevent re-ignition, and patrol continues until the fire is declared out.
Firefighter safety is the first priority. The LCES principle requires that lookouts, communications, escape routes and safety zones are established and known to all before and during engagement. Standard firefighting orders and watch-out situations, developed in the United States, list conditions that increase risk, such as working downhill toward a fire, in heavy fuels, in unfamiliar terrain or when weather is changing. Many firefighter deaths have occurred when fires made sudden runs uphill or with wind shifts, trapping crews in vegetation without escape routes. Protective clothing, training, physical fitness and limits on working hours reduce risk.
The Incident Command System (ICS) is a standardised organisation for managing emergencies, developed in the United States in the 1970s after major California wildfires and now used for many types of incident in many countries. It is led by an incident commander, supported by command staff for safety, liaison and public information, and by general staff heading four sections: operations (tactical work on the fire), planning (information, resources status, incident action plans), logistics (supplies, facilities, communications, food) and finance/administration (costs, time records, procurement). ICS uses common terminology, a modular structure that expands or contracts with the size of the incident, unified command when several agencies are involved, management by objectives through incident action plans for each operational period, and a manageable span of control, usually between three and seven subordinates per supervisor, with five considered ideal. Adoption of ICS-type systems by forest departments improves coordination with fire services, police and disaster management authorities.
Prescribed burning is the deliberate application of fire to fuels under specified weather, fuel and other conditions (the prescription), within a defined area, to achieve management objectives. Objectives include reducing hazardous fuel loads to lower the intensity and severity of later wildfires; preparing seedbeds and controlling competing vegetation for regeneration; maintaining fire-dependent ecosystems and habitats; improving forage; controlling some pests and diseases; and reducing fuel along fire lines. In Indian forestry, controlled burning refers especially to the burning of cleared fire lines and of litter in selected areas before the main fire season, and early burning to burning parts of the forest early in the dry season, when fuels are still partly moist, so that fires are of low intensity and later fires are deprived of fuel.
A prescribed burn is carried out under a written burn plan that states the objectives; describes the area, fuels and boundaries; sets the prescription (acceptable ranges of temperature, relative humidity, wind speed and direction, fuel moisture and drought indices); specifies the ignition pattern, the personnel, equipment and water needed, holding and contingency arrangements if fire escapes; plans smoke management to avoid impacts on roads, settlements and sensitive sites; and includes notification of neighbours and authorities and post-burn evaluation. The burn proceeds only when conditions are within prescription, and is stopped if they move outside it.
The ignition pattern controls fire intensity. A backing fire is lit along a downwind or downslope control line and allowed to burn slowly against the wind or downslope; it has low intensity and short flames and is safest, though slow. A head fire burns with the wind or upslope, fast and intense; it is used only when higher intensity is needed and control is assured. Flank fires are lit in lines parallel to the wind and spread sideways. Strip-head firing sets a series of lines upwind of a control line, each burning a short distance with the wind before meeting the burned strip ahead, giving intensity between backing and heading fires. Spot or grid ignition lights points in a pattern so that fires merge. Aerial ignition from helicopters or drones is used for large areas.
Prescribed burning carries risks: fires can escape, smoke can affect health and visibility, and burning at the wrong season can damage species or soils. Burning windows, the days when conditions fall within prescription, are limited and becoming fewer in some regions with climate change. Legal liability, staff capacity, smoke regulations and public acceptance constrain its use. Where it is ecologically appropriate and well executed, prescribed burning is one of the most effective tools for reducing wildfire risk; where it is not, mechanical fuel treatments may be preferred.
After a fire, managers assess its extent and effects to decide on rehabilitation, salvage and future management. Burned-area mapping uses ground surveys, aerial photography and satellite imagery. Burn severity, the degree of ecological change, is assessed by ground indicators, such as the proportion of trees killed, crown scorch, char height on stems, consumption of litter and duff and the condition of the soil surface, and by remote sensing. The differenced Normalized Burn Ratio (dNBR), calculated from near-infrared and shortwave-infrared reflectance before and after the fire, is widely used to map severity over large areas, with field plots used to calibrate severity classes.
Whether a tree dies after fire depends on crown scorch (the proportion of the crown killed), cambium damage at the base (related to bark thickness and residence time of the fire) and root damage, and on species and tree size. Delayed mortality is common, so assessments should be repeated after a year or more. Fire-damaged trees may be attacked by bark beetles and borers (see forest-entomology) and decay fungi. Salvage logging recovers timber value from killed trees, but it can damage regenerating vegetation and soils and remove dead wood important for habitat; its timing, extent and methods should be planned with ecological effects in mind.
Severe fires can expose soil, destroy the litter layer and sometimes create water-repellent (hydrophobic) soil layers, increasing runoff, erosion, flooding and debris flows in the following rainy seasons (see forest-hydrology-watershed). In the United States, Burned Area Emergency Response (BAER) teams assess risks to life, property and critical resources after major fires and prescribe emergency treatments. Measures include mulching with straw or wood shreds, seeding with quick-growing native or sterile cover species, contour log or straw barriers, check dams in channels, road drainage improvements and protection of water intakes. Treatments should be targeted to the highest-risk areas because their effectiveness varies and some, such as seeding non-native grasses, can hinder native recovery.
Longer-term rehabilitation assesses natural regeneration, which in fire-adapted forests is often sufficient, and plants or sows where it is not, using species and provenances suited to the site and future climate. Protection from grazing and from repeated fire is often the most important measure for recovery of degraded tropical forests. Monitoring vegetation recovery, erosion and water quality over several years informs future fire and land management.
In landscapes where most fires are started by people, fire cannot be managed effectively without the people who live in and use the forest. Community-based fire management involves local communities in prevention, detection, suppression and the safe use of fire, building on their knowledge, their presence in the landscape and their interest in the forest's products. It recognises that many uses of fire are legitimate livelihoods (agricultural burning, pasture management) and seeks to make them safer rather than simply prohibiting them, which often fails.
Common elements include awareness and training of villagers in fire prevention and safe burning; formation of village fire committees or volunteer fire groups equipped with basic tools; agreements on rules for agricultural and pasture burning, such as burning only in permitted seasons, in the early morning or evening, with fire lines around fields and with people present; rewards for villages whose forests remain fire-free, through development funds or a share of forest revenue; employment of local people as fire watchers; and joint patrols with forest staff. In India, joint forest management committees and the van panchayats of Uttarakhand have taken responsibility for fire protection in their forests, and the National Action Plan on Forest Fires (2018) emphasised community participation. In Indonesia, community fire-care groups (Masyarakat Peduli Api) were established in fire-prone provinces. In northern Australia, Indigenous ranger groups use traditional early dry-season burning to reduce late dry-season wildfires, and savanna burning projects earn carbon credits for the emissions avoided.
Many indigenous and local communities have long traditions of fire use, timed and placed to manage habitats, reduce fuel and protect resources. Recognising and supporting traditional fire knowledge, where it remains, can complement scientific fire management. At the same time, changes in population, land use, climate and invasive species mean that traditional practices may need adaptation, and conflicts can arise where fire use by one group damages the resources of another.
Community-based fire management succeeds when communities have secure rights and clear benefits from the forest, when roles and responsibilities between communities and forest departments are agreed, when training and equipment are provided, when early warnings reach villages, and when successes are recognised. It fails when fire bans are imposed without addressing livelihoods, when benefits do not reach those who bear the costs, or when support ends after projects close.
Learn the fire triangle and fire behaviour triangle, fuel strata and timelag classes, the parts of a fire and the factors driving spread, Byram's intensity and flame-length formulas with their units, the three types of fire, the main fire danger indices, the elements of a burn plan and the structure of the Incident Command System. Practise calculating fireline intensity and flame length. In descriptive answers, link causes, behaviour, effects and control, and give examples from Indian forests and from fire-adapted ecosystems elsewhere.
A forester five years in prepares for each fire season: maintaining and burning fire lines, recruiting and training fire watchers, organising village fire committees, checking equipment and communication, and monitoring fire danger and satellite alerts. During fires the forester leads initial attack, applies safety rules and coordinates with other agencies; afterwards, assesses damage, records fires and plans rehabilitation. Practical skills include reading fire behaviour, choosing direct or indirect attack and running safe controlled burns.
A senior forester designs fire management strategy for a division or region: fire risk mapping, fuel management priorities, detection and response capacity, interagency coordination using incident command principles, community programmes, and policy on prescribed burning and fire use. The senior forester also leads large incidents, manages budgets and public communication, and adapts planning to longer, more severe fire seasons.
A senior researcher studies fire behaviour modelling, fire ecology and regimes, remote sensing of fire and burn severity, fire-climate interactions, smoke and carbon emissions, and the social dimensions of fire use; develops danger rating and decision support tools; and advises national fire policy and international programmes.
Fire line widths, fire season dates and organisational details vary by state and country and are not prescribed here. Thresholds relating flame length to suppression tactics are US guidance and approximate. Fuel model parameters, the equations of the Rothermel model and detailed FWI calculations are not reproduced. Retardant and foam products are not named. Smoke health effects and air-quality regulation are mentioned only briefly. General disturbance ecology is in forest-ecology, climate links in forests-climate-carbon and hydrological effects of fire in forest-hydrology-watershed.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
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