Wildfire

Wildfire

Overview
A wildfire is any uncontrolled fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

 in combustible vegetation that occurs in the countryside or a wilderness
Wilderness
Wilderness or wildland is a natural environment on Earth that has not been significantly modified by human activity. It may also be defined as: "The most intact, undisturbed wild natural areas left on our planet—those last truly wild places that humans do not control and have not developed with...

 area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same phenomenon depending on the type of vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 being burned.
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Encyclopedia
A wildfire is any uncontrolled fire
Fire
Fire is the rapid oxidation of a material in the chemical process of combustion, releasing heat, light, and various reaction products. Slower oxidative processes like rusting or digestion are not included by this definition....

 in combustible vegetation that occurs in the countryside or a wilderness
Wilderness
Wilderness or wildland is a natural environment on Earth that has not been significantly modified by human activity. It may also be defined as: "The most intact, undisturbed wild natural areas left on our planet—those last truly wild places that humans do not control and have not developed with...

 area. Other names such as brush fire, bushfire, forest fire, desert fire, grass fire, hill fire, squirrel fire, vegetation fire, veldfire, and wilkjjofire may be used to describe the same phenomenon depending on the type of vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

 being burned. A wildfire differs from other fires by its extensive size, the speed at which it can spread out from its original source, its potential to change direction unexpectedly, and its ability to jump gaps such as roads, rivers and fire breaks. Wildfires are characterized in terms of the cause of ignition, their physical properties such as speed of propagation, the combustible material present, and the effect of weather on the fire.

Wildfires occur on every continent except Antarctica. Fossil records and human history contain accounts of wildfires, as wildfires can occur in periodic intervals. Wildfires can cause extensive damage, both to property and human life, but they also have various beneficial effects on wilderness areas. Some plant species depend on the effects of fire for growth and reproduction, although large wildfires may also have negative ecological effects.

Strategies of wildfire prevention, detection, and suppression have varied over the years, and international wildfire management experts encourage further development of technology and research. One of the more controversial techniques is controlled burn
Controlled burn
Controlled or prescribed burning, also known as hazard reduction burning or Swailing is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for...

ing
: permitting or even igniting smaller fires to minimize the amount of flammable material available for a potential wildfire. While some wildfires burn in remote forested regions, they can cause extensive destruction of homes and other property located in the wildland-urban interface
Wildland-urban interface
A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within of the zone may also be included...

: a zone of transition between developed areas and undeveloped wilderness.

Characteristics


The name wildfire was once a synonym for Greek fire
Greek fire
Greek fire was an incendiary weapon used by the Byzantine Empire. The Byzantines typically used it in naval battles to great effect as it could continue burning while floating on water....

 but now refers to any large or destructive conflagration
Conflagration
A conflagration or a blaze is an uncontrolled burning that threatens human life, health, or property. A conflagration can be accidentally begun, naturally caused , or intentionally created . Arson can be accomplished for the purpose of sabotage or diversion, and also can be the consequence of...

. Wildfires differ from other fires in that they take place outdoors in areas of grassland
Grassland
Grasslands are areas where the vegetation is dominated by grasses and other herbaceous plants . However, sedge and rush families can also be found. Grasslands occur naturally on all continents except Antarctica...

, woodland
Woodland
Ecologically, a woodland is a low-density forest forming open habitats with plenty of sunlight and limited shade. Woodlands may support an understory of shrubs and herbaceous plants including grasses. Woodland may form a transition to shrubland under drier conditions or during early stages of...

s, bushland
Bushland
Bushland is any area in Australia that is predominantly indigenous flora and fauna.Bushland is the term commonly used by conservation protection groups and other environmental groups as a blanket term for natural vegetation, which may cover any kind of habitat from open shrubby country with few...

, scrubland, peatland, and other wooded areas that act as a source of fuel
Fuel
Fuel is any material that stores energy that can later be extracted to perform mechanical work in a controlled manner. Most fuels used by humans undergo combustion, a redox reaction in which a combustible substance releases energy after it ignites and reacts with the oxygen in the air...

, or combustible material. Buildings may become involved if a wildfire spreads to adjacent communities. While the causes of wildfires vary and the outcomes are always unique, all wildfires can be characterized in terms of their physical properties, their fuel type, and the effect that weather has on the fire.

Wildfire behaviour and severity result from the combination of factors such as available fuels, physical setting, and weather. While wildfires can be large, uncontrolled disasters that burn through 0.4 to 400 km² (98.8 to 98,842.1 acre) or more, they can also be as small as 0.001 square kilometre (0.247105163015276 acre) or less. Although smaller events may be included in wildfire modeling
Wildfire modeling
In computational science, wildfire modeling is concerned with numerical simulation of wildland fires in order to understand and predict fire behavior. Wildfire modeling can ultimately aid wildland fire suppression, namely increase safety of firefighters and the public, reduce risk, and minimize...

, most do not earn press attention. This can be problematic because public fire policies, which relate to fires of all sizes, are influenced more by the way the media portrays catastrophic wildfires than by small fires.

Causes



The four major natural causes of wildfire ignitions are lightning
Lightning
Lightning is an atmospheric electrostatic discharge accompanied by thunder, which typically occurs during thunderstorms, and sometimes during volcanic eruptions or dust storms...

, volcanic eruption, sparks from rockfalls, and spontaneous combustion
Spontaneous combustion
Spontaneous combustion is the self-ignition of a mass, for example, a pile of oily rags. Allegedly, humans can also ignite and burn without an obvious cause; this phenomenon is known as spontaneous human combustion....

. The thousands of coal seam fires that are burning around the world, such as those in Centralia
Centralia, Pennsylvania
Centralia is a borough and ghost town in Columbia County, Pennsylvania, United States. Its population has dwindled from over 1,000 residents in 1981 to 12 in 2005, 9 in 2007, and 10 in 2010, as a result of a mine fire burning beneath the borough since 1962...

, Burning Mountain
Burning Mountain
Burning Mountain, the common name for Mount Wingen, is a hill near Wingen, New South Wales, Australia, approximately north of Sydney just off the New England Highway. It takes its name from a smouldering coal seam running underground through the sandstone...

, and several coal-sustained fires in China, can also flare up and ignite nearby flammable material. However, many wildfires are attributed to human sources such as arson
Arson
Arson is the crime of intentionally or maliciously setting fire to structures or wildland areas. It may be distinguished from other causes such as spontaneous combustion and natural wildfires...

, discarded cigarettes, sparks from equipment, and power line arcs
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...

 (as detected by arc mapping
Arc mapping
Arc mapping is a technique used in fire investigation and is usually performed by a forensic electrical engineer. It relies on finding the locations of electrical arcs and other electrical faults that occurred during the fire; the locations of the electrical faults can then, under some...

). In societies experiencing shifting cultivation
Shifting cultivation
Shifting cultivation is an agricultural system in which plots of land are cultivated temporarily, then abandoned. This system often involves clearing of a piece of land followed by several years of wood harvesting or farming, until the soil loses fertility...

 where land is cleared quickly and farmed until the soil loses fertility, slash and burn
Slash and burn
Slash-and-burn is an agricultural technique which involves cutting and burning of forests or woodlands to create fields. It is subsistence agriculture that typically uses little technology or other tools. It is typically part of shifting cultivation agriculture, and of transhumance livestock...

 clearing is often considered the least expensive way to prepare land for future use. Forested areas cleared by logging encourage the dominance of flammable grasses, and abandoned logging roads overgrown by vegetation may act as fire corridors. Annual grassland fires in southern Vietnam
Vietnam
Vietnam – sometimes spelled Viet Nam , officially the Socialist Republic of Vietnam – is the easternmost country on the Indochina Peninsula in Southeast Asia. It is bordered by China to the north, Laos to the northwest, Cambodia to the southwest, and the South China Sea –...

 can be attributed in part to the destruction of forested areas by US military herbicides, explosives, and mechanical land clearing and burning operations during the Vietnam War
Vietnam War
The Vietnam War was a Cold War-era military conflict that occurred in Vietnam, Laos, and Cambodia from 1 November 1955 to the fall of Saigon on 30 April 1975. This war followed the First Indochina War and was fought between North Vietnam, supported by its communist allies, and the government of...

.

The most common cause of wildfires varies throughout the world. In the United States, Canada, and northwest China, for example, lightning is the major source of ignition. In other parts of the world, human involvement is a major contributor. In Mexico, Central America, South America, Africa, Southeast Asia, Fiji, and New Zealand, wildfires can be attributed to human activities such as animal husbandry
Animal husbandry
Animal husbandry is the agricultural practice of breeding and raising livestock.- History :Animal husbandry has been practiced for thousands of years, since the first domestication of animals....

, agriculture, and land-conversion burning. Human carelessness is a major cause of wildfires in China and in the Mediterranean Basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...

. In Australia, the source of wildfires can be traced to both lightning strikes and human activities such as machinery sparks and cast-away cigarette butts."

Fuel type


The spread of wildfires varies based on the flammable material present and its vertical arrangement. For example, fuels uphill from a fire are more readily dried and warmed by the fire than those downhill, yet burning logs can roll downhill from the fire to ignite other fuels. Fuel arrangement and density is governed in part by topography
Topography
Topography is the study of Earth's surface shape and features or those ofplanets, moons, and asteroids...

, as land shape determines factors such as available sunlight and water for plant growth. Overall, fire types can be generally characterized by their fuels as follows:This section is a composite of several references. Refer to:
  • National Wildfire Coordinating Group Communicator's Guide For Wildland Fire Management, 3.

  • Ground fires are fed by subterranean roots, duff
    Forest floor
    The forest floor, also called detritus, duff and the O horizon, is one of the most distinctive features of a forest ecosystem. It mainly consists of shed vegetative parts, such as leaves, branches, bark, and stems, existing in various stages of decomposition above the soil surface...

     and other buried organic matter
    Organic matter
    Organic matter is matter that has come from a once-living organism; is capable of decay, or the product of decay; or is composed of organic compounds...

    . This fuel type is especially susceptible to ignition due to spotting. Ground fires typically burn by smoldering, and can burn slowly for days to months, such as peat fires in Kalimantan
    Kalimantan
    In English, the term Kalimantan refers to the Indonesian portion of the island of Borneo, while in Indonesian, the term "Kalimantan" refers to the whole island of Borneo....

     and Eastern Sumatra
    Sumatra
    Sumatra is an island in western Indonesia, westernmost of the Sunda Islands. It is the largest island entirely in Indonesia , and the sixth largest island in the world at 473,481 km2 with a population of 50,365,538...

    , Indonesia
    Indonesia
    Indonesia , officially the Republic of Indonesia , is a country in Southeast Asia and Oceania. Indonesia is an archipelago comprising approximately 13,000 islands. It has 33 provinces with over 238 million people, and is the world's fourth most populous country. Indonesia is a republic, with an...

    , which resulted from a riceland creation project
    Mega Rice Project (Kalimantan)
    The Mega Rice Project was initiated in 1996 in the southern sections of Kalimantan, the Indonesian section of Borneo. The goal was to turn one million hectares of unproductive and sparsely populated peat swamp forest into rice paddies in an effort to allieviate Indonesia's growing food shortage....

     that unintentionally drained and dried the peat.
  • Crawling or surface fires are fueled by low-lying vegetation such as leaf and timber litter, debris, grass, and low-lying shrubbery.
  • Ladder fires consume material between low-level vegetation and tree canopies, such as small trees, downed logs, and vine
    Vine
    A vine in the narrowest sense is the grapevine , but more generally it can refer to any plant with a growth habit of trailing or scandent, that is to say climbing, stems or runners...

    s. Kudzu
    Kudzu
    Kudzu is a plant in the genus Pueraria in the pea family Fabaceae, subfamily Faboideae. It is a climbing, coiling, and trailing vine native to southern Japan and southeast China. Its name comes from the Japanese name for the plant, . It is a weed that climbs over trees or shrubs and grows so...

    , Old World climbing fern, and other invasive plants that scale trees may also encourage ladder fires.
  • Crown, canopy, or aerial fires burn suspended material at the canopy level, such as tall trees, vines, and mosses. The ignition of a crown fire, termed crowning, is dependent on the density of the suspended material, canopy height, canopy continuity, and sufficient surface and ladder fires in order to reach the tree crowns. For example, ground-clearing fires lit by humans can spread into the Amazon rain forest, damaging ecosystems not particularly suited for heat or arid conditions.

Physical properties


Wildfires occur when all of the necessary elements of a fire triangle
Fire triangle
The fire triangle or combustion triangle is a simple model for understanding the ingredients necessary for most fires.The triangle illustrates a fire requires three elements: heat, fuel, and an oxidizing agent . The fire is prevented or extinguished by removing any one of them...

 come together in a susceptible area: an ignition source is brought into contact with a combustible material such as vegetation
Vegetation
Vegetation is a general term for the plant life of a region; it refers to the ground cover provided by plants. It is a general term, without specific reference to particular taxa, life forms, structure, spatial extent, or any other specific botanical or geographic characteristics. It is broader...

, that is subjected to sufficient heat and has an adequate supply of oxygen from the ambient air. A high moisture content usually prevents ignition and slows propagation, because higher temperatures are required to evaporate any water within the material and heat the material to its fire point
Fire point
The fire point of a fuel is the temperature at which it will continue to burn for at least 5 seconds after ignition by an open flame. At the flash point, a lower temperature, a substance will ignite briefly, but vapor might not be produced at a rate to sustain the fire...

. Dense forests usually provide more shade, resulting in lower ambient temperatures and greater humidity, and are therefore less susceptible to wildfires. Less dense material such as grasses and leaves are easier to ignite because they contain less water than denser material such as branches and trunks. Plants continuously lose water by evapotranspiration
Evapotranspiration
Evapotranspiration is a term used to describe the sum of evaporation and plant transpiration from the Earth's land surface to atmosphere. Evaporation accounts for the movement of water to the air from sources such as the soil, canopy interception, and waterbodies...

, but water loss is usually balanced by water absorbed from the soil, humidity, or rain. When this balance is not maintained, plants dry out and are therefore more flammable, often a consequence of droughts.
A wildfire front is the portion sustaining continuous flaming combustion, where unburned material meets active flames, or the smoldering transition between unburned and burned material. As the front approaches, the fire heats both the surrounding air and woody material through convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 and thermal radiation
Thermal radiation
Thermal radiation is electromagnetic radiation generated by the thermal motion of charged particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation....

. First, wood is dried as water is vaporized at a temperature of 100 °C (212 °F). Next, the pyrolysis
Pyrolysis
Pyrolysis is a thermochemical decomposition of organic material at elevated temperatures without the participation of oxygen. It involves the simultaneous change of chemical composition and physical phase, and is irreversible...

 of wood at 230 °C (446 °F) releases flammable gases. Finally, wood can smoulder at 380 °C (716 °F) or, when heated sufficiently, ignite at 590 °C (1,094 °F). Even before the flames of a wildfire arrive at a particular location, heat transfer
Heat transfer
Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...

 from the wildfire front warms the air to 800 °C (1,472 °F), which pre-heats and dries flammable materials, causing materials to ignite faster and allowing the fire to spread faster. High-temperature and long-duration surface wildfires may encourage flashover
Flashover
A flashover is the near simultaneous ignition of most of the directly exposed combustible material in an enclosed area. When certain organic materials are heated they undergo thermal decomposition and release flammable gases...

 or torching: the drying of tree canopies and their subsequent ignition from below.

Wildfires have a rapid forward rate of spread (FROS) when burning through dense, uninterrupted fuels. They can move as fast as 10.8 kilometres per hour (6.7 mph) in forests and 22 kilometres per hour (13.7 mph) in grasslands. Wildfires can advance tangential to the main front to form a flanking front, or burn in the opposite direction of the main front by backing. They may also spread by jumping or spotting as winds and vertical convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....

 columns carry firebrand
Firebrand
The word Firebrand has several uses:* A piece of burning wood * A person with a penchant for militancy in speech and/or action-Vehicles:*Blackburn Firebrand, an aircraft constructed for the Royal Navy...

s
(hot wood embers) and other burning materials through the air over roads, rivers, and other barriers that may otherwise act as firebreak
Firebreak
A firebreak is a gap in vegetation or other combustible material that acts as a barrier to slow or stop the progress of a bushfire or wildfire. A firebreak may occur naturally where there is a lack of vegetation or "fuel", such as a river, lake or canyon...

s. Torching and fires in tree canopies encourage spotting, and dry ground fuels that surround a wildfire are especially vulnerable to ignition from firebrands. Spotting can create spot fires as hot embers and firebrands ignite fuels downwind from the fire. In Australian bushfires, spot fires are known to occur as far as 10 kilometres (6 mi) from the fire front.

Especially large wildfires may affect air currents in their immediate vicinities by the stack effect
Stack effect
Stack effect is the movement of air into and out of buildings, chimneys, flue gas stacks, or other containers, and is driven by buoyancy. Buoyancy occurs due to a difference in indoor-to-outdoor air density resulting from temperature and moisture differences. The result is either a positive or...

: air rises as it is heated, and large wildfires create powerful updrafts that will draw in
Advection
Advection, in chemistry, engineering and earth sciences, is a transport mechanism of a substance, or a conserved property, by a fluid, due to the fluid's bulk motion in a particular direction. An example of advection is the transport of pollutants or silt in a river. The motion of the water carries...

 new, cooler air from surrounding areas in thermal columns. Great vertical differences in temperature and humidity encourage pyrocumulus cloud
Pyrocumulus cloud
A pyrocumulus, or literally fire cloud, is a dense cumuliform cloud associated with fire or volcanic activity.A pyrocumulus is similar dynamically in some ways to a firestorm, and the two phenomena may occur in conjunction with each other...

s, strong winds, and fire whirl
Fire whirl
A fire whirl, colloquially fire devil or fire tornado, is a phenomenon—rarely captured on camera—in which a fire, under certain conditions , acquires a vertical vorticity and forms a whirl, or a tornado-like vertically oriented rotating column of air...

s with the force of tornadoes at speeds of more than 80 kilometres per hour (49.7 mph). Rapid rates of spread, prolific crowning or spotting, the presence of fire whirls, and strong convection columns signify extreme conditions.

Effect of weather


Heat wave
Heat wave
A heat wave is a prolonged period of excessively hot weather, which may be accompanied by high humidity. There is no universal definition of a heat wave; the term is relative to the usual weather in the area...

s, drought
Drought
A drought is an extended period of months or years when a region notes a deficiency in its water supply. Generally, this occurs when a region receives consistently below average precipitation. It can have a substantial impact on the ecosystem and agriculture of the affected region...

s, cyclical climate change
Climate change
Climate change is a significant and lasting change in the statistical distribution of weather patterns over periods ranging from decades to millions of years. It may be a change in average weather conditions or the distribution of events around that average...

s such as El Niño, and regional weather patterns such as high-pressure ridges can increase the risk and alter the behavior of wildfires dramatically. Years of precipitation followed by warm periods can encourage more widespread fires and longer fire seasons. Since the mid 1980s, earlier snowmelt and associated warming has also been associated with an increase in length and severity of the wildfire season in the Western United States
Western United States
.The Western United States, commonly referred to as the American West or simply "the West," traditionally refers to the region comprising the westernmost states of the United States. Because the U.S. expanded westward after its founding, the meaning of the West has evolved over time...

. However, one individual element does not always cause an increase in wildfire activity. For example, wildfires will not occur during a drought unless accompanied by other factors, such as lightning (ignition source) and strong winds (mechanism for rapid spread).

Fire intensity also increases during daytime hours. Burn rates of smoldering logs are up to five times greater during the day due to lower humidity, increased temperatures, and increased wind speeds. Sunlight warms the ground during the day which creates air currents that travel uphill. At night the land cools, creating air currents that travel downhill. Wildfires are fanned by these winds and often follow the air currents over hills and through valleys. Fires in Europe occur frequently during the hours of 12:00 p.m. and 2:00 p.m. Wildfire suppression operations in the United States revolve around a 24-hour fire day that begins at 10:00 a.m. due to the predictable increase in intensity resulting from the daytime warmth.

Ecology



Wildfires are common in climates that are sufficiently moist to allow the growth of vegetation but feature extended dry, hot periods. Such places include the vegetated areas of Australia and Southeast Asia
Southeast Asia
Southeast Asia, South-East Asia, South East Asia or Southeastern Asia is a subregion of Asia, consisting of the countries that are geographically south of China, east of India, west of New Guinea and north of Australia. The region lies on the intersection of geological plates, with heavy seismic...

, the veld
Veld
The term Veld refers primarily to the wide open rural spaces of South Africa or southern Africa and in particular to certain flatter areas or districts covered in grass or low scrub...

 in southern Africa, the fynbos
Fynbos
Fynbos is the natural shrubland or heathland vegetation occurring in a small belt of the Western Cape of South Africa, mainly in winter rainfall coastal and mountainous areas with a Mediterranean climate...

 in the Western Cape of South Africa, the forested areas of the United States and Canada, and the Mediterranean Basin
Mediterranean Basin
In biogeography, the Mediterranean Basin refers to the lands around the Mediterranean Sea that have a Mediterranean climate, with mild, rainy winters and hot, dry summers, which supports characteristic Mediterranean forests, woodlands, and scrub vegetation...

. Fires can be particularly intense during days of strong winds, periods of drought, and during warm summer months. Global warming
Global warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...

 may increase the intensity and frequency of droughts in many areas, creating more intense and frequent wildfires.

Although some ecosystems rely on naturally occurring fires to regulate growth, many ecosystems suffer from too much fire, such as the chaparral
Chaparral
Chaparral is a shrubland or heathland plant community found primarily in the U.S. state of California and in the northern portion of the Baja California peninsula, Mexico...

 in southern California
Southern California
Southern California is a megaregion, or megapolitan area, in the southern area of the U.S. state of California. Large urban areas include Greater Los Angeles and Greater San Diego. The urban area stretches along the coast from Ventura through the Southland and Inland Empire to San Diego...

 and lower elevation deserts in the American Southwest. The increased fire frequency in these ordinarily fire-dependent areas has upset natural cycles, destroyed native plant communities, and encouraged the growth of fire-intolerant vegetation and non-native weeds. Invasive species
Invasive species
"Invasive species", or invasive exotics, is a nomenclature term and categorization phrase used for flora and fauna, and for specific restoration-preservation processes in native habitats, with several definitions....

, such as Lygodium microphyllum
Lygodium microphyllum
Lygodium microphyllum is a climbing fern originating in tropical Africa, South East Asia, Melanesia and Australia. It is an invasive weed in the US States of Florida and Alabama where it invades open forest and wetland areas...

and Bromus tectorum, can grow rapidly in areas that were damaged by fires. Because they are highly flammable, they can increase the future risk of fire, creating a positive feedback loop that increases fire frequency and further destroys native growth.

In the Amazon Rainforest
Amazon Rainforest
The Amazon Rainforest , also known in English as Amazonia or the Amazon Jungle, is a moist broadleaf forest that covers most of the Amazon Basin of South America...

, drought, logging, cattle ranching practices, and slash-and-burn agriculture damage fire-resistant forests and promote the growth of flammable brush, creating a cycle that encourages more burning. Fires in the rainforest threaten its collection of diverse species and produce large amounts of CO2. Also, fires in the rainforest, along with drought and human involvement, could damage or destroy more than half of the Amazon rainforest by the year 2030. Wildfires generate ash, destroy available organic nutrients, and cause an increase in water runoff, eroding away other nutrients and creating flash flood
Flash flood
A flash flood is a rapid flooding of geomorphic low-lying areas—washes, rivers, dry lakes and basins. It may be caused by heavy rain associated with a storm, hurricane, or tropical storm or meltwater from ice or snow flowing over ice sheets or snowfields...

 conditions. A 2003 wildfire in the North Yorkshire Moors destroyed 2.5 square kilometres (617.8 acre) of heather
Ericaceae
The Ericaceae, commonly known as the heath or heather family, is a group of mostly calcifuge flowering plants. The family is large, with roughly 4000 species spread across 126 genera, making it the 14th most speciose family of flowering plants...

 and the underlying peat
Peat
Peat is an accumulation of partially decayed vegetation matter or histosol. Peat forms in wetland bogs, moors, muskegs, pocosins, mires, and peat swamp forests. Peat is harvested as an important source of fuel in certain parts of the world...

 layers. Afterwards, wind erosion stripped the ash and the exposed soil, revealing archaeological remains dating back to 10,000 BC. Wildfires can also have an effect on climate change, increasing the amount of carbon released into the atmosphere and inhibiting vegetation growth, which affects overall carbon uptake by plants.

Plant adaptation


Plants in wildfire-prone ecosystems often survive through adaptations to their local fire regime
Fire regime
A fire regime is the pattern, frequency and intensity of the bushfires and wildfires that prevails in an area. It is an integral part of fire ecology, and renewal for certain types of ecosystems. If fires are too frequent, plants may be killed before they have matured, or before they have set...

. Such adaptations include physical protection against heat, increased growth after a fire event, and flammable materials that encourage fire and may eliminate competition
Competition
Competition is a contest between individuals, groups, animals, etc. for territory, a niche, or a location of resources. It arises whenever two and only two strive for a goal which cannot be shared. Competition occurs naturally between living organisms which co-exist in the same environment. For...

. For example, plants of the genus Eucalyptus
Eucalyptus
Eucalyptus is a diverse genus of flowering trees in the myrtle family, Myrtaceae. Members of the genus dominate the tree flora of Australia...

contain flammable oils that encourage fire and hard sclerophyll
Sclerophyll
Sclerophyll is the term for a type of vegetation that has hard leaves and short internodes . The word comes from the Greek sclero and phyllon ....

 leaves to resist heat and drought, ensuring their dominance over less fire-tolerant species. Dense bark, shedding lower branches, and high water content in external structures may also protect trees from rising temperatures. Fire-resistant seeds and reserve shoot
Shoot
Shoots are new plant growth, they can include stems, flowering stems with flower buds, and leaves. The new growth from seed germination that grows upward is a shoot where leaves will develop...

s that sprout after a fire encourage species preservation, as embodied by pioneer species
Pioneer species
Pioneer species are species which colonize previously uncolonized land, usually leading to ecological succession. They are the first organisms to start the chain of events leading to a livable biosphere or ecosystem...

. Smoke, charred wood, and heat can stimulate the germination of seeds in a process called serotiny
Serotiny
Serotiny is an ecological adaptation exhibited by some seed plants, in which seed release occurs in response to an environmental trigger, rather than spontaneously at seed maturation. The most common and best studied trigger is fire, and the term serotiny is often used to refer to this specific case...

. Exposure to smoke from burning plants promotes germination
Germination
Germination is the process in which a plant or fungus emerges from a seed or spore, respectively, and begins growth. The most common example of germination is the sprouting of a seedling from a seed of an angiosperm or gymnosperm. However the growth of a sporeling from a spore, for example the...

 in other types of plants by inducing the production of the orange butenolide
Butenolide
Butenolides are a class of lactones with a four-carbon heterocyclic ring structure. They are sometimes considered oxidized derivatives of furan. The simplest butenolide is 2-furanone, which is a common component of larger natural products and is sometimes referred to as simply "butenolide". A...

.

Grasslands in Western Sabah
Sabah
Sabah is one of 13 member states of Malaysia. It is located on the northern portion of the island of Borneo. It is the second largest state in the country after Sarawak, which it borders on its southwest. It also shares a border with the province of East Kalimantan of Indonesia in the south...

, Malaysian pine
Pine
Pines are trees in the genus Pinus ,in the family Pinaceae. They make up the monotypic subfamily Pinoideae. There are about 115 species of pine, although different authorities accept between 105 and 125 species.-Etymology:...

 forests, and Indonesian Casuarina
Casuarina
Casuarina is a genus of 17 species in the family Casuarinaceae, native to Australasia, southeast Asia, and islands of the western Pacific Ocean. It was once treated as the sole genus in the family, but has been split into three genera .They are evergreen shrubs and trees growing to 35 m tall...

forests are believed to have resulted from previous periods of fire. Chamise deadwood litter is low in water content and flammable, and the shrub quickly sprouts after a fire. Sequoia rely on periodic fires to reduce competition, release seeds from their cone
Conifer cone
A cone is an organ on plants in the division Pinophyta that contains the reproductive structures. The familiar woody cone is the female cone, which produces seeds. The male cones, which produce pollen, are usually herbaceous and much less conspicuous even at full maturity...

s, and clear the soil and canopy for new growth. Caribbean Pine
Caribbean Pine
The Caribbean Pine, Pinus caribaea, is a hard pine native to Central America, Cuba, Jamaica, the Bahamas, and the Turks and Caicos Islands. It inhabits tropical and subtropical coniferous forests, which include both lowland savannas and montane forests...

 in Bahamian pineyards have adapted to and rely on low-intensity, surface fires for survival and growth. An optimum fire frequency for growth is every 3 to 10 years. Too frequent fires favor herbaceous plant
Herbaceous plant
A herbaceous plant is a plant that has leaves and stems that die down at the end of the growing season to the soil level. They have no persistent woody stem above ground...

s, and infrequent fires favor species typical of Bahamian dry forests
Bahamian dry forests
The Bahamian dry forests are a tropical and subtropical dry broadleaf forest ecoregion in the Bahamas and the Turks and Caicos Islands, covering an area of . They are found on much of the northern Bahamas, including Andros, Abaco, and Grand Bahama, where they are known as coppices...

.

Atmospheric effects



Most of the Earth's weather and air pollution resides in the troposphere
Troposphere
The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 80% of the atmosphere's mass and 99% of its water vapor and aerosols....

, the part of the atmosphere that extends from the surface of the planet to a height of about 10 kilometres (6.2 mi). The vertical lift of a severe thunderstorm or pyrocumulonimbus
Pyrocumulonimbus
The pyrocumulonimbus cloud is a type of cumulus cloud formed above a source of heat such as a wildfire and may sometimes even extinguish the fire that formed it. It is the most extreme manifestation of pyrocumulus...

 can be enhanced in the area of a large wildfire, which can propel smoke, soot, and other particulate matter as high as the lower stratosphere
Stratosphere
The stratosphere is the second major layer of Earth's atmosphere, just above the troposphere, and below the mesosphere. It is stratified in temperature, with warmer layers higher up and cooler layers farther down. This is in contrast to the troposphere near the Earth's surface, which is cooler...

. Previously, prevailing scientific theory held that most particles in the stratosphere came from volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

es, but smoke and other wildfire emissions have been detected from the lower stratosphere. Pyrocumulus clouds can reach 6100 metres (20,013.1 ft) over wildfires. Increased fire byproducts in the stratosphere can increase ozone concentration beyond safe levels. Satellite observation of smoke plumes from wildfires revealed that the plumes could be traced intact for distances exceeding 1600 kilometres (994.2 mi). Computer-aided models such as CALPUFF
CALPUFF
CALPUFF is an advanced, integrated Gaussian puff modeling system for the simulation of atmospheric pollution dispersion distributed by the Atmospheric Studies Group at TRC Solutions...

 may help predict the size and direction of wildfire-generated smoke plumes by using atmospheric dispersion modeling
Atmospheric dispersion modeling
Atmospheric dispersion modeling is the mathematical simulation of how air pollutants disperse in the ambient atmosphere. It is performed with computer programs that solve the mathematical equations and algorithms which simulate the pollutant dispersion...

.

Wildfires can affect climate and weather and have major impacts on atmospheric pollution. Wildfire emissions
Wildland fire emissions
Wildland fire and wildland fire atmospheric emissions have been a part of the global biosphere for millennia. . The major wildland fire emissions include greenhouse gasses and several criteria pollutants that impact human health and welfare. :...

 contain fine particulate matter which can cause cardiovascular and respiratory problems. Forest fires in Indonesia in 1997 were estimated to have released between 0.81 and 2.57 gigatonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s (0.89 and 2.83 billion short ton
Short ton
The short ton is a unit of mass equal to . In the United States it is often called simply ton without distinguishing it from the metric ton or the long ton ; rather, the other two are specifically noted. There are, however, some U.S...

s) of CO2 into the atmosphere, which is between 13%–40% of the annual carbon dioxide emissions from burning fossil fuels. Atmospheric models suggest that these concentrations of sooty particles could increase absorption of incoming solar radiation during winter months by as much as 15%.

History



In the Welsh Borders, the first evidence of wildfire is rhyniophytoid
Rhyniophyta
Rhyniopsida is a class of extinct early vascular plants, with one family, Rhyniaceae, found in the Early Devonian . They are polysporangiophytes, since their sporophytes consisted of branched stems bearing sporangia . They lacked leaves or true roots but did have simple vascular tissue...

 plant fossils preserved as charcoal
Charcoal
Charcoal is the dark grey residue consisting of carbon, and any remaining ash, obtained by removing water and other volatile constituents from animal and vegetation substances. Charcoal is usually produced by slow pyrolysis, the heating of wood or other substances in the absence of oxygen...

, dating to the Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 period (about ). Smoldering surface fires started to occur sometime before the Early Devonian
Devonian
The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 period . Low atmospheric oxygen during the Middle and Late Devonian was accompanied by a decrease in charcoal abundance. Additional charcoal evidence suggests that fires continued through the Carboniferous
Carboniferous
The Carboniferous is a geologic period and system that extends from the end of the Devonian Period, about 359.2 ± 2.5 Mya , to the beginning of the Permian Period, about 299.0 ± 0.8 Mya . The name is derived from the Latin word for coal, carbo. Carboniferous means "coal-bearing"...

 period. Later, the overall increase of atmospheric oxygen from 13% in the Late Devonian to 30-31% by the Late Permian was accompanied by a more widespread distribution of wildfires. Later, a decrease in wildfire-related charcoal deposits from the late Permian to the Triassic
Triassic
The Triassic is a geologic period and system that extends from about 250 to 200 Mya . As the first period of the Mesozoic Era, the Triassic follows the Permian and is followed by the Jurassic. Both the start and end of the Triassic are marked by major extinction events...

 periods is explained by a decrease in oxygen levels.

Wildfires during the Paleozoic and Mesozoic periods followed patterns similar to fires that occur in modern times. Surface fires driven by dry seasons are evident in Devonian and Carboniferous progymnosperm
Progymnosperm
The progymnosperms are an extinct group of woody, spore-bearing plants that is presumed to have evolved from the "trimerophytes", and eventually gave rise to the gymnosperms. They have been treated formally at the rank of division Progymnospermophyta or class Progymnospermopsida...

 forests. Lepidodendron
Lepidodendron
Lepidodendron is an extinct genus of primitive, vascular, arborescent plant related to the Lycopsids . It was part of the coal forest flora. They sometimes reached heights of over , and the trunks were often over in diameter, and thrived during the Carboniferous period...

 forests dating to the Carboniferous period have charred peaks, evidence of crown fires. In Jurassic gymnosperm
Gymnosperm
The gymnosperms are a group of seed-bearing plants that includes conifers, cycads, Ginkgo, and Gnetales. The term "gymnosperm" comes from the Greek word gymnospermos , meaning "naked seeds", after the unenclosed condition of their seeds...

 forests, there is evidence of high frequency, light surface fires. The increase of fire activity in the late Tertiary
Tertiary
The Tertiary is a deprecated term for a geologic period 65 million to 2.6 million years ago. The Tertiary covered the time span between the superseded Secondary period and the Quaternary...

 is possibly due to the increase of C4
C4 carbon fixation
C4 carbon fixation is one of three biochemical mechanisms, along with and CAM photosynthesis, used in carbon fixation. It is named for the 4-carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3-carbon molecule products in plants. fixation is an...

-type grasses. As these grasses shifted to more mesic habitat
Mesic habitat
In ecology, a mesic habitat is a type of habitat with a moderate or well-balanced supply of moisture, e.g., a mesic forest, a temperate hardwood forest, or dry-mesic prairie. Compared to a dry habitat, a mesic habitat is moister....

s, their high flammability increased fire frequency, promoting grasslands over woodlands. However, fire-prone habitats may have contributed to the prominence of trees such as those of the genus Pinus, which have thick bark to withstand fires and employ serotiny.

Human involvement


The human use of fire for agricultural and hunting purposes during the Paleolithic
Paleolithic
The Paleolithic Age, Era or Period, is a prehistoric period of human history distinguished by the development of the most primitive stone tools discovered , and covers roughly 99% of human technological prehistory...

 and Mesolithic
Mesolithic
The Mesolithic is an archaeological concept used to refer to certain groups of archaeological cultures defined as falling between the Paleolithic and the Neolithic....

 ages altered the preexisting landscapes and fire regimes. Woodlands were gradually replaced by smaller vegetation that facilitated travel, hunting, seed-gathering and planting. In recorded human history, minor allusions to wildfires were mentioned in the Bible
Bible
The Bible refers to any one of the collections of the primary religious texts of Judaism and Christianity. There is no common version of the Bible, as the individual books , their contents and their order vary among denominations...

 and by classical writers such as Homer
Homer
In the Western classical tradition Homer , is the author of the Iliad and the Odyssey, and is revered as the greatest ancient Greek epic poet. These epics lie at the beginning of the Western canon of literature, and have had an enormous influence on the history of literature.When he lived is...

. However, while ancient Hebrew, Greek, and Roman writers were aware of fires, they were not very interested in the uncultivated lands where wildfires occurred. Wildfires were used in battles throughout human history as early thermal weapons. From the Middle ages
Middle Ages
The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, accounts were written of occupational burning as well as customs and laws that governed the use of fire. In Germany, regular burning was documented in 1290 in the Odenwald
Odenwald
The Odenwald is a low mountain range in Hesse, Bavaria and Baden-Württemberg in Germany.- Location :The Odenwald lies between the Upper Rhine Rift Valley with the Bergstraße and the Hessisches Ried in the west, the Main and the Bauland in the east, the Hanau-Seligenstadt Basin – a subbasin of...

 and in 1344 in the Black Forest
Black Forest
The Black Forest is a wooded mountain range in Baden-Württemberg, southwestern Germany. It is bordered by the Rhine valley to the west and south. The highest peak is the Feldberg with an elevation of 1,493 metres ....

. In the 14th century Sardinia
Sardinia
Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...

, firebreaks were used for wildfire protection. In Spain during the 1550s, sheep husbandry
Sheep husbandry
Sheep husbandry is a subcategory of animal husbandry specifically dealing with the raising and breeding of domestic sheep. Sheep farming is primarily based on raising lambs for meat, or raising sheep for wool. Sheep may also be raised for milk or to sell to other farmers.-Shelter and...

 was discouraged in certain provinces by Philip II
Philip II of Spain
Philip II was King of Spain, Portugal, Naples, Sicily, and, while married to Mary I, King of England and Ireland. He was lord of the Seventeen Provinces from 1556 until 1581, holding various titles for the individual territories such as duke or count....

 due to the harmful effects of fires used in transhumance
Transhumance
Transhumance is the seasonal movement of people with their livestock between fixed summer and winter pastures. In montane regions it implies movement between higher pastures in summer and to lower valleys in winter. Herders have a permanent home, typically in valleys. Only the herds travel, with...

. As early as the 17th century, Native Americans were observed using fire
Native American use of fire
In addition to simple cooking, Pre-Columbian Native Americans used fire in many and significant ways, ranging from protecting an area from fire to landscape-altering clearing of prairie.-Human-shaped landscape:...

 for many purposes including cultivation, signaling
Smoke signal
The smoke signal is one of the oldest forms of communication in recorded history. It is a form of visual communication used over long distance.-History and usage:...

, and warfare. Scottish botanist David Douglas
David Douglas
David Douglas was a Scottish botanist. He worked as a gardener, and explored the Scottish Highlands, North America, and Hawaii, where he died.-Early life:...

 noted the native use of fire for tobacco cultivation, to encourage deer into smaller areas for hunting purposes, and to improve foraging for honey and grasshoppers. Charcoal found in sedimentary deposits off the Pacific coast of Central America suggests that more burning occurred in the 50 years before the Spanish colonization of the Americas
Spanish colonization of the Americas
Colonial expansion under the Spanish Empire was initiated by the Spanish conquistadores and developed by the Monarchy of Spain through its administrators and missionaries. The motivations for colonial expansion were trade and the spread of the Christian faith through indigenous conversions...

 than after the colonization. In the post-World War II Baltic region
Baltic region
The terms Baltic region, Baltic Rim countries, and Baltic Rim refer to slightly different combinations of countries in the general area surrounding the Baltic Sea.- Etymology :...

, socio-economic changes led more stringent air quality standards and bans on fires that eliminated traditional burning practices.

Wildfires typically occurred during periods of increased temperature and drought. An increase in fire-related debris flow
Debris flow
A debris flow is a fast moving, liquefied landslide of unconsolidated, saturated debris that looks like flowing concrete. It is differentiated from a mudflow in terms of the viscosity and textural properties of the flow. Flows can carry material ranging in size from clay to boulders, and may...

 in alluvial fan
Alluvial fan
An alluvial fan is a fan-shaped deposit formed where a fast flowing stream flattens, slows, and spreads typically at the exit of a canyon onto a flatter plain. A convergence of neighboring alluvial fans into a single apron of deposits against a slope is called a bajada, or compound alluvial...

s of northeastern Yellowstone National Park
Yellowstone National Park
Yellowstone National Park, established by the U.S. Congress and signed into law by President Ulysses S. Grant on March 1, 1872, is a national park located primarily in the U.S. state of Wyoming, although it also extends into Montana and Idaho...

 was linked to the period between AD 1050 and 1200, coinciding with the Medieval Warm Period
Medieval Warm Period
The Medieval Warm Period , Medieval Climate Optimum, or Medieval Climatic Anomaly was a time of warm climate in the North Atlantic region, that may also have been related to other climate events around the world during that time, including in China, New Zealand, and other countries lasting from...

. However, human influence caused an increase in fire frequency. Dendrochronological fire scar data and charcoal layer data in Finland
Finland
Finland , officially the Republic of Finland, is a Nordic country situated in the Fennoscandian region of Northern Europe. It is bordered by Sweden in the west, Norway in the north and Russia in the east, while Estonia lies to its south across the Gulf of Finland.Around 5.4 million people reside...

 suggests that, while many fires occurred during severe drought conditions, an increase in the number of fires during 850 BC and 1660 AD can be attributed to human influence. Charcoal evidence from the Americas suggested a general decrease in wildfires between 1 AD and 1750 compared to previous years. However, a period of increased fire frequency between 1750 and 1870 was suggested by charcoal data from North America and Asia, attributed to human population growth and influences such as land clearing practices. This period was followed by an overall decrease in burning in the 20th century, linked to the expansion of agriculture, increased livestock grazing, and fire prevention efforts.

Prevention



Wildfire prevention refers to the preemptive methods of reducing the risk of fires as well as lessening its severity and spread. Effective prevention techniques allow supervising agencies to manage air quality, maintain ecological balances, protect resources, and to limit the effects of future uncontrolled fires. North American firefighting policies may permit naturally caused fires to burn to maintain their ecological role, so long as the risks of escape into high-value areas are mitigated. However, prevention policies must consider the role that humans play in wildfires, since, for example, 95% of forest fires in Europe are related to human involvement. Sources of human-caused fire may include arson, accidental ignition, or the uncontrolled use of fire in land-clearing and agriculture such as the slash-and-burn farming in Southeast Asia. A new and ecologically evolutionary practice, termed "Hydro-Pyrogeography", promises and claims to bound wildfire from passing through any such wildland-urban interface anywhere on earth that the practice is put into place, and thereby diminishing, even eliminating the above-referred oppositions and concerns to traditional fuel management techniques.

In the mid-19th century, explorers from the HMS Beagle
HMS Beagle
HMS Beagle was a Cherokee-class 10-gun brig-sloop of the Royal Navy. She was launched on 11 May 1820 from the Woolwich Dockyard on the River Thames, at a cost of £7,803. In July of that year she took part in a fleet review celebrating the coronation of King George IV of the United Kingdom in which...

 observed Australian Aborigines
Australian Aborigines
Australian Aborigines , also called Aboriginal Australians, from the latin ab originem , are people who are indigenous to most of the Australian continentthat is, to mainland Australia and the island of Tasmania...

 using fire for ground clearing, hunting, and regeneration of plant food in a method later named fire-stick farming
Fire-stick farming
Fire-stick farming is a term coined by Australian archaeologist Rhys Jones in 1969 to describe the practice of Indigenous Australians where fire was used regularly to burn vegetation to facilitate hunting and to change the composition of plant and animal species in an area.Fire-stick farming had...

. Such careful use of fire has been employed for centuries in the lands protected by Kakadu National Park
Kakadu National Park
Kakadu National Park is in the Northern Territory of Australia, 171 km southeast of Darwin.Kakadu National Park is located within the Alligator Rivers Region of the Northern Territory of Australia. It covers an area of , extending nearly 200 kilometres from north to south and over 100 kilometres...

 to encourage biodiversity. In 1937, U.S. President Franklin D. Roosevelt
Franklin D. Roosevelt
Franklin Delano Roosevelt , also known by his initials, FDR, was the 32nd President of the United States and a central figure in world events during the mid-20th century, leading the United States during a time of worldwide economic crisis and world war...

 initiated a nationwide fire prevention campaign, highlighting the role of human carelessness in forest fires. Later posters of the program featured Uncle Sam
Uncle Sam
Uncle Sam is a common national personification of the American government originally used during the War of 1812. He is depicted as a stern elderly man with white hair and a goatee beard...

, leaders of the Axis powers of World War II, characters from the Disney movie Bambi
Bambi
Bambi is a 1942 American animated film directed by David Hand , produced by Walt Disney and based on the book Bambi, A Life in the Woods by Austrian author Felix Salten...

, and the official mascot of the U.S. Forest Service, Smokey Bear
Smokey Bear
Smokey Bear is a mascot of the United States Forest Service created to educate the public about the dangers of forest fires. An advertising campaign featuring Smokey was created in 1944 with the slogan, "Smokey Says – Care Will Prevent 9 out of 10 Forest Fires". Smokey Bear's later slogan,...

.
Wildfires are caused by a combination of natural factors such as topography, fuels, and weather. Other than reducing human infractions, only fuels may be altered to affect future fire risk and behavior. Wildfire prevention programs around the world may employ techniques such as wildland fire use and prescribed or controlled burn
Controlled burn
Controlled or prescribed burning, also known as hazard reduction burning or Swailing is a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement. Fire is a natural part of both forest and grassland ecology and controlled fire can be a tool for...

s
. Wildland fire use refers to any fire of natural causes that is monitored but allowed to burn. Controlled burns are fires ignited by government agencies under less dangerous weather conditions.

Vegetation may be burned periodically to maintain high species diversity, and frequent burning of surface fuels limits fuel accumulation, thereby reducing the risk of crown fires. Using strategic cuts of trees, fuels may also be removed by handcrews in order to clean and clear the forest, prevent fuel build-up, and create access into forested areas. Chain saws and large equipment can be used to thin out ladder fuels and shred trees and vegetation to a mulch
Mulch
In agriculture and gardening, is a protective cover placed over the soil to retain moisture, reduce erosion, provide nutrients, and suppress weed growth and seed germination. Mulching in gardens and landscaping mimics the leaf cover that is found on forest floors....

. Multiple fuel treatments are often needed to influence future fire risks, and wildfire models may be used to predict and compare the benefits of different fuel treatments on future wildfire spread.

However, controlled burns are reportedly "the most effective treatment for reducing a fire’s rate of spread, fireline intensity, flame length, and heat per unit of area" according to Jan Van Wagtendonk, a biologist at the Yellowstone Field Station. Additionally, while fuel treatments are typically limited to smaller areas, effective fire management requires the administration of fuels across large landscapes in order to reduce future fire size and severity.

Building codes in fire-prone areas typically require that structures be built of flame-resistant materials and a defensible space
Defensible space (fire control)
In the context of fire control, Defensible Space is the natural and landscaped area around a structure that has been maintained and designed to reduce fire danger, sometimes called Firescaping. "Defensible space" is also used in the context of wildfires, especially in the wildland-urban interface...

 be maintained by clearing flammable materials within a prescribed distance from the structure. Communities in the Philippines
Philippines
The Philippines , officially known as the Republic of the Philippines , is a country in Southeast Asia in the western Pacific Ocean. To its north across the Luzon Strait lies Taiwan. West across the South China Sea sits Vietnam...

 also maintain fire lines 5 to 10 m (16.4 to 32.8 ft) wide between the forest and their village, and patrol these lines during summer months or seasons of dry weather. Fuel buildup can result in costly, devastating fires as new homes, ranches, and other development are built adjacent to wilderness areas
Wildland-urban interface
A wildland–urban interface refers to the zone of transition between unoccupied land and human development. Communities that are within of the zone may also be included...

. Continued growth in fire-prone areas and rebuilding structures destroyed by fires has been met with criticism.

However, the population growth along the wildland-urban interface discourages the use of current fuel management techniques. Smoke is an irritant and attempts to thin out the fuel load is met with opposition due to desirability of forested areas, in addition to other wilderness goals such as endangered species protection and habitat preservation. The ecological benefits of fire are often overridden by the economic and safety benefits of protecting structures and human life. For example, while fuel treatments decrease the risk of crown fires, these techniques destroy the habitats of various plant and animal species. Additionally, government policies that cover the wilderness usually differ from local and state policies that govern urban lands.

History of Wildland Fire Policy in the U.S.


Since the turn of the 20th century, various federal and state agencies have been involved in wildland fire management in one form or another. In the early 20th century, for example, the federal government, through the U.S. Army and the U.S. Forest Service, solicited fire suppression as a primary goal of managing the nation’s forests. At this time in history fire was viewed as a threat to timber-an economically important natural resource. As such, rational decisions were made to devote public funds to fire suppression and fire prevention efforts. For example, the Forest Fire Emergency Fund Act of 1908 permitted deficit spending in the case of emergency fire situations. As a result, the U.S. Forest Service was able to acquire a deficit of over $1 million in 1910 due to emergency fire suppression efforts. Following the same tone of timber resource protection, the U.S. Forest Service adopted the “10 AM Policy” in 1935. Through this policy the agency advocated the control of all fires by 10 o’clock of the morning following the discovery of a wildfire. Fire prevention was also heavily advocated through public education campaigns such as Smokey the Bear. Through these and similar public education campaigns the general public was, in a sense, trained to perceive all wildfire as a threat to civilized society and natural resources. The negative sentiment towards wildland fire prevailed and helped to shape wildland fire management objectives throughout most of the 20th century.

Beginning in the 1970s public perception of wildland fire management began to shift. Despite portly funding for fire suppression in the first half of the 20th century, massive wildfires continued to be prevalent across the landscape of North America. Natural resource professionals and ordinary citizens alike became curious about the ecological effects of wildfire. Ecologists were beginning to recognize the presence and ecological importance of natural lightning-ignited wildfires across the United States. Along with this new discovery of fire knowledge and the emergence of fire ecology as a science came an effort to apply fire to land in a controlled manner. It was learned that suppression of fire in certain ecosystems actually increases the likelihood that a wildfire will occur and increases the intensity of those wildfires. By the 1980s funding efforts began to support prescribed burning. In light of emerging information about wildland fire, rational thought justified funding prescribed burning in order to prevent catastrophic wildfire events. In this way, the costs of implementing prescribed burns were thought to be less than the costs imposed on society by catastrophic wildfires. In addition to using prescribed fire to reduce the chance of catastrophic wildfires, mechanical methods have recently been adopted as well. Mechanical methods include the use of chippers and other machinery to remove hazardous fuels and thereby reduce the risk of wildfire events.

Economics of Fire Management Policy


Similar to that of military operations, fire management is often very expensive in the U.S. Today, it is not uncommon for suppression operations for a single wildfire to exceed costs of $1 million in just a few days. Although fire suppression offers many benefits to society, other options for fire management exist. While these options cannot completely replace fire suppression as a fire management tool, other options can play an important role in overall fire management and can therefore affect the costs of fire suppression.

The application of fire management tools requires making certain tradeoffs. Below is a sample of some costs and benefits associated with the tools currently used in fire management. Current approaches to fire management are an almost complete turnaround compared to historic approaches. In fact, it is commonly accepted that past fire suppression, along with other factors, has resulted in larger, more intense wildfire events which are seen today. In economic terms, expenditures used for wildfire suppression in the early 20th century have contributed to increased suppression costs which are being realized today. As is the case with many public policy issues, costs and benefits associated with particular fire management tools are difficult to accurately quantify. Ultimately, costs and benefits should be weighed against one another on a case-by-case basis in planning wildland fire management operations.

Depending on the tradeoffs that a land manager is willing to make, a combination of the following fire management tools could be used. For instance, prescribed fire and/or mechanical fuels reduction could be used to help prevent or lessen the intensity of a wildfire thereby reducing or eliminating suppression costs. In addition, prescribed fire and/or mechanical fuels reduction could be used to improve soil conditions in fields or in forests to the benefit of wildlife or natural resources. On the other hand, the use of prescribed fire requires much advanced planning and can have negative impacts on human health in nearby communities.


Costs and Benefits of Wildland Fire Management Tools
Costs Benefits
Suppression
  • Labour intensive
  • Requires high level of planning
  • Can be very expensive
  • Particular strategies can be very inefficient (i.e. aerial retardant drops)
  • Can increase intensity and likelihood of future wildfires.
  • Inhibits natural ecological processes in many cases

  • Can reduce human health impacts
  • Can protect forest and agricultural resources
  • Can save private dwellings and commercial buildings
Prescribed fire
  • Can be expensive to implement
  • Requires skilled workforce to implement
  • Requires high level of planning
  • Can impact human health (e.g. smoke and its effect on those with asthma or allergies)

  • Can provide habitat for wildlife
  • Can improve forest and agricultural resources
  • Can reduce hazardous fuel loading
  • Mimics natural processes but under more controlled circumstances
Mechanical Fuels Reduction
  • Requires use of heavy machinery (resulting in fossil fuel consumption, compaction, etc.)
  • Can be expensive to implement
  • Does not mimic natural processes

  • Can provide habitat for wildlife
  • Can improve forest and agricultural resources
  • Can reduce hazardous fuel loading
  • Does not produce large amounts of smoke

Detection



Fast and effective detection is a key factor in wildfire fighting. Early detection efforts were focused on early response, accurate results in both daytime and nighttime, and the ability to prioritize fire danger. Fire lookout tower
Fire lookout tower
A fire lookout tower, fire tower or lookout tower, provides housing and protection for a person known as a "fire lookout" whose duty it is to search for wildfires in the wilderness...

s were used in the United States in the early 20th century and fires were reported using telephones, carrier pigeon
Carrier pigeon
A carrier pigeon is a homing pigeon that is used to carry messages. Using pigeons to carry messages is generally called "pigeon post". Most homing or racing type varieties are used to carry messages. There is no specific breed actually called "carrier pigeon"...

s, and heliograph
Heliograph
A heliograph is a wireless solar telegraph that signals by flashes of sunlight reflected by a mirror. The flashes are produced by momentarily pivoting the mirror, or by interrupting the beam with a shutter...

s. Aerial and land photography using instant camera
Instant camera
The instant camera is a type of camera that generates a developed film image. The most popular types to use self-developing film were formerly made by Polaroid Corporation....

s were used in the 1950s until infrared scanning
Infrared photography
In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about...

 was developed for fire detection in the 1960s. However, information analysis and delivery was often delayed by limitations in communication technology. Early satellite-derived fire analyses were hand-drawn on maps at a remote site and sent via overnight mail to the fire manager
Incident Commander
The incident commander is the person responsible for all aspects of an emergency response; including quickly developing incident objectives, managing all incident operations, application of resources as well as responsibility for all persons involved. The incident commander sets priorities and...

. During the Yellowstone fires of 1988
Yellowstone fires of 1988
The Yellowstone fires of 1988 together formed the largest wildfire in the recorded history of the U.S.'s Yellowstone National Park. Starting as many smaller individual fires, the flames spread quickly out of control with increasing winds and drought and combined into one large conflagration, which...

, a data station was established in West Yellowstone, permitting the delivery of satellite-based fire information in approximately four hours.

Currently, public hotlines, fire lookout
Fire lookout
A fire lookout is a person assigned the duty to look for fire from atop a building known as a fire lookout tower. These towers are used in remote areas, normally on mountain tops with high elevation and a good view of the surrounding terrain, to spot smoke caused by a wildfire.Once a possible fire...

s in towers, and ground and aerial patrols can be used as a means of early detection of forest fires. However, accurate human observation may be limited by operator fatigue
Asthenopia
Asthenopia or eye strain is an ophthalmological condition that manifests itself through nonspecific symptoms such as fatigue, pain in or around the eyes, blurred vision, headache and occasional double vision...

, time of day, time of year, and geographic location. Electronic systems have gained popularity in recent years as a possible resolution to human operator error. These systems may be semi- or fully automated and employ systems based on the risk area and degree of human presence, as suggested by GIS
Geographic Information System
A geographic information system, geographical information science, or geospatial information studies is a system designed to capture, store, manipulate, analyze, manage, and present all types of geographically referenced data...

 data analyses. An integrated approach of multiple systems can be used to merge satellite data, aerial imagery, and personnel position via Global Positioning System
Global Positioning System
The Global Positioning System is a space-based global navigation satellite system that provides location and time information in all weather, anywhere on or near the Earth, where there is an unobstructed line of sight to four or more GPS satellites...

 (GPS) into a collective whole for near-realtime use by wireless Incident Command Centers
Incident Command System
The Incident Command System is "a systematic tool used for the command, control, and coordination of emergency response" according to the United States Federal Highway Administration...

.

A small, high risk area that features thick vegetation, a strong human presence, or is close to a critical urban area can be monitored using a local sensor network. Detection systems may include wireless sensor network
Wireless sensor network
A wireless sensor network consists of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants and to cooperatively pass their data through the network to a main location. The more modern...

s that act as automated weather systems: detecting temperature, humidity, and smoke. These may be battery-powered, solar-powered, or tree-rechargeable: able to recharge their battery systems using the small electrical currents in plant material. Larger, medium-risk areas can be monitored by scanning towers that incorporate fixed cameras and sensors to detect smoke or additional factors such as the infrared signature of carbon dioxide produced by fires. Additional capabilities such as night vision
Night vision
Night vision is the ability to see in low light conditions. Whether by biological or technological means, night vision is made possible by a combination of two approaches: sufficient spectral range, and sufficient intensity range...

, brightness detection, and color change detection may also be incorporated into sensor arrays.
Satellite and aerial monitoring through the use of planes, helicopter, or UAVs can provide a wider view and may be sufficient to monitor very large, low risk areas. These more sophisticated systems employ GPS and aircraft-mounted infrared or high-resolution visible cameras to identify and target wildfires. Satellite-mounted sensors such as Envisat
Envisat
Envisat is an Earth-observing satellite. It was launched on 1 March 2002 aboard an Ariane 5 from the Guyana Space Centre in Kourou, French Guyana into a Sun synchronous polar orbit at an altitude of...

's Advanced Along Track Scanning Radiometer
AATSR
The Advanced Along Track Scanning Radiometer is one of the Announcement of Opportunity instruments on board the European Space Agency 's Envisat satellite....

 and European Remote-Sensing Satellite
European Remote-Sensing Satellite
European remote sensing satellite was the European Space Agency's first Earth-observing satellite. It was launched on July 17, 1991 into a Sun-synchronous polar orbit at a height of 782–785 km.-Instruments:...

's Along-Track Scanning Radiometer can measure infrared radiation emitted by fires, identifying hot spots greater than 39 °C (102.2 °F). The National Oceanic and Atmospheric Administration
National Oceanic and Atmospheric Administration
The National Oceanic and Atmospheric Administration , pronounced , like "noah", is a scientific agency within the United States Department of Commerce focused on the conditions of the oceans and the atmosphere...

's Hazard Mapping System combines remote-sensing data from satellite sources such as Geostationary Operational Environmental Satellite
Geostationary Operational Environmental Satellite
The Geostationary Satellite system, operated by the United States National Environmental Satellite, Data, and Information Service , supports weather forecasting, severe storm tracking, and meteorology research. Spacecraft and ground-based elements of the system work together to provide a continuous...

 (GOES), Moderate-Resolution Imaging Spectroradiometer (MODIS), and Advanced Very High Resolution Radiometer
Advanced Very High Resolution Radiometer
The Advanced Very High Resolution Radiometer is a space-borne sensor embarked on the National Oceanic and Atmospheric Administration family of polar orbiting platforms . AVHRR instruments measure the reflectance of the Earth in 5 relatively wide spectral bands...

 (AVHRR) for detection of fire and smoke plume locations. However, satellite detection is prone to offset errors, anywhere from 2 to 3 km (1.2 to 1.9 mi) for MODIS and AVHRR data and up to 12 kilometres (7.5 mi) for GOES data. Satellites in geostationary orbits may become disabled, and satellites in polar orbits are often limited by their short window of observation time. Cloud cover and image resolution and may also limit the effectiveness of satellite imagery.

Suppression


Wildfire suppression depends on the technologies available in the area in which the wildfire occurs. In less developed nations the techniques used can be as simple as throwing sand or beating the fire with sticks or palm fronds. In more advanced nations, the suppression methods vary due to increased technological capacity. Silver iodide
Silver iodide
Silver iodide is a yellow, inorganic, photosensitive iodide of silver used in photography, in medicine as an antiseptic, and in rainmaking for cloud seeding.-Crystal structure:...

 can be used to encourage snow fall, while fire retardant
Fire retardant
A fire retardant is a substance other than water that reduces flammability of fuels or delays their combustion. This typically refers to chemical retardants but may also include substances that work by physical action, such as cooling the fuels; examples of these include fire-fighting foams and...

s and water can be dropped onto fires by unmanned aerial vehicle
Unmanned aerial vehicle
An unmanned aerial vehicle , also known as a unmanned aircraft system , remotely piloted aircraft or unmanned aircraft, is a machine which functions either by the remote control of a navigator or pilot or autonomously, that is, as a self-directing entity...

s, planes, and helicopters
Helitack
Helitack refers to "helicopter-delivered fire resources", and is the system of managing and using helicopters and their crews to perform aerial firefighting and other firefighting duties, primarily initial attack on wildfires...

. Complete fire suppression is no longer an expectation, but the majority of wildfires are often extinguished before they grow out of control. While more than 99% of the 10,000 new wildfires each year are contained, escaped wildfires can cause extensive damage. Worldwide damage from wildfires is in the billions of euros annually. Wildfires in Canada and the US burn an average of 54500 square kilometres (13,467,231.4 acre) per year.

Above all, fighting wildfires can become deadly. A wildfire's burning front may also change direction unexpectedly and jump across fire breaks. Intense heat and smoke can lead to disorientation and loss of appreciation of the direction of the fire, which can make fires particularly dangerous. For example, during the 1949 Mann Gulch fire
Mann Gulch fire
The Mann Gulch fire of 1949 was a wildfire in the Helena National Forest, Montana, United States, which claimed the lives of 13 firefighters including 12 smoke jumpers who were parachuted into the area to fight the fire, but were unable to control it....

 in Montana
Montana
Montana is a state in the Western United States. The western third of Montana contains numerous mountain ranges. Smaller, "island ranges" are found in the central third of the state, for a total of 77 named ranges of the Rocky Mountains. This geographical fact is reflected in the state's name,...

, USA, thirteen smokejumper
Smokejumper
A smokejumper is a wildland firefighter who parachutes into a remote area to combat wildfires.Smokejumpers are most often deployed to fires that are extremely remote. The risks associated with this method of personnel deployment are mitigated by an extremely well developed training program that has...

s died when they lost their communication links, became disorientated, and were overtaken by the fire. In the Australian February 2009 Victorian bushfires
February 2009 Victorian bushfires
The Black Saturday bushfires were a series of bushfires that ignited or were burning across the Australian state of Victoria on and around Saturday, 7 February 2009...

, at least 173 people died and over 2,029 homes and 3,500 structures were lost when they became engulfed by wildfire.

Modeling


Wildfire modeling is concerned with numerical simulation of wildfires in order to comprehend and predict fire behavior. Wildfire modeling can ultimately aid wildfire suppression, increase the safety of firefighters and the public, and minimize damage. Using computational science
Computational science
Computational science is the field of study concerned with constructing mathematical models and quantitative analysis techniques and using computers to analyze and solve scientific problems...

, wildfire modeling involves the statistical analysis of past fire events to predict spotting risks and front behavior. Various wildfire propagation models have been proposed in the past, including simple ellipses and egg- and fan-shaped models. Early attempts to determine wildfire behavior assumed terrain and vegetation uniformity. However, the exact behavior of a wildfire's front is dependent on a variety of factors, including windspeed and slope steepness. Modern growth models utilize a combination of past ellipsoidal descriptions and Huygens' Principle to simulate fire growth as a continuously expanding polygon. Extreme value theory
Extreme value theory
Extreme value theory is a branch of statistics dealing with the extreme deviations from the median of probability distributions. The general theory sets out to assess the type of probability distributions generated by processes...

 may also be used to predict the size of large wildfires. However, large fires that exceed suppression capabilities are often regarded as statistical outliers in standard analyses, even though fire policies are more influenced by catastrophic wildfires than by small fires.

See also


External links