A Wildfire Or Wildland Fire

This article is about outdoor fires. For other uses, see Wildfire (disambiguation). For other uses, see Brushfire (disambiguation).The Rim Fire consumed more than 250,000 acres (1,000 km2) of forest near Yosemite National Park, in 2013 A wildfire or wildland fire is a fire in an area of combustible vegetation that occurs in the countryside or rural area. Depending on the type of vegetation where it occurs, a wildfire can also be classified more specifically as a brush fire, bush fire, desert fire, forest fire, grass fire, hill fire, peat fire, vegetation fire, or veld fire.

Fossil charcoal indicates that wildfires began soon after the appearance of terrestrial plants 420 million years ago. Wildfire’s occurrence throughout the history of terrestrial life invites conjecture that fire must have had pronounced evolutionary effects on most ecosystems' flora and fauna. Earth is an intrinsically flammable planet owing to its cover of carbon-rich vegetation, seasonally dry climates, atmospheric oxygen, and widespread lightning and volcanic ignitions. Wildfires can be characterized in terms of the cause of ignition, their physical properties, the combustible material present, and the effect of weather on the fire. Wildfires can cause damage to property and human life, but they have many beneficial effects on native vegetation, animals, and ecosystems that have evolved with fire. Many plant species depend on the effects of fire for growth and reproduction.

However, wildfire in ecosystems where wildfire is uncommon or where non-native vegetation has encroached may have negative ecological effects.[5] Wildfire behaviour and severity result from the combination of factors such as available fuels, physical setting, and weather.

Analyses of historical meteorological data and national fire records in western North America show the primacy of climate in driving large regional fires via wet periods that create substantial fuels or drought and warming that extend conducive fire weather. Strategies of wildfire prevention, detection, and suppression have varied over the years.[13] One common and inexpensive technique is controlled burning: permitting or even igniting smaller fires to minimize the amount of flammable material available for a potential wildfire.

Vegetation may be burned periodically to maintain high species diversity and frequent burning of surface fuels limits fuel accumulation.[16][17] Wildland fire use is the cheapest and most ecologically appropriate policy for many forests.[18] Fuels may also be removed by logging, but fuels treatments and thinning have no effect on severe fire behavior when under extreme weather conditions.[19] Wildfire itself is 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.[20] Building codes in fire-prone areas typically require that structures be built of flame-resistant materials and a defensible space be maintained by clearing flammable materials within a prescribed distance from the structure.

The most common direct human causes of wildfire ignition include arson, discarded cigarettes, power-line arcs (as detected by arc mapping), and sparks from equipment. Ignition of wildland fires via contact with hot rifle-bullet fragments is also possible under the right conditions. Wildfires can also be started in communities experiencing shifting cultivation, where land is cleared quickly and farmed until the soil loses fertility, and slash and burn clearing.[28] 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 stem in part from the destruction of forested areas by US militaryherbicides, explosives, and mechanical land-clearing and -burning operations during the Vietnam War.The most common cause of wildfires varies throughout the world.

In Canada and northwest China, for example, lightning operates as the major source of ignition. In other parts of the world, human involvement is a major contributor. In Africa, Central America, Fiji, Mexico, New Zealand, South America, and Southeast Asia, wildfires can be attributed to human activities such as agriculture, animal husbandry, and land-conversion burning. In China and in the Mediterranean Basin, human carelessness is a major cause of wildfires. In the United States and Australia, the source of wildfires can be traced both to lightning strikes and to human activities (such as machinery sparks, cast-away cigarette butts, or arson).Coal seam fires burn in the thousands around the world, such as those in Burning Mountain, New South Wales; Centralia, Pennsylvania; and several coal-sustained fires in China. They can also flare up unexpectedly and ignite nearby flammable material.

A surface fire in the western desert of Utah, U.S.Charred landscape following a crown fire in the North Cascades, U.S.The spread of wildfires varies based on the flammable material present, its vertical arrangement and moisture content, and weather conditions. Fuel arrangement and density is governed in part by topography, 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:Ground fires are fed by subterranean roots, duff and other buried organic matter. 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 Kalimantanand Eastern Sumatra, Indonesia, which resulted from a riceland creation project that unintentionally drained and dried the peat.

Crawling or surface fires are fueled by low-lying vegetation on the forest floor such as leaf and timber litter, debris, grass, and low-lying shrubbery. This kind of fire often burns at a relatively lower temperature than crown fires (less than 400 °C (752 °F)) and may spread at slow rate, though steep slopes and wind can accelerate the rate of spread.