Wildfire


Fire in San Bernardino, California Mountains
(image taken from the International Space Station)
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A wildfire, also known as a forest fire (or bushfire in Australasia), is an uncontrolled fire in wildland often caused by lightning; other common causes are human carelessness and arson.

Drought and the prevention of small forest fires are major contributors to extreme forest fires.

Table of contents
1 Background
2 Prevention
3 Fire suppression
4 Famous wildfires in North America
5 External Links
6 Further Reading
7 Other Items Titled 'Wildfire'

Background

Wildfires are common in many places around the world, including much of the vegetated areas of Australia, forest areas of the United States and Canada, where the climates are sufficiently moist to allow the growth of trees, but feature extended dry, hot periods when fallen branches, leaves, and other material can dry out and becomes highly flammable. Wildfires are also common in grasslands and scrublands. Wildfires tend to be most common and severe during years of drought and occur on days of strong winds. With extensive urbanization of wildlands, these fires often involve destruction of suburban homes located in the wildland urban intermix.

Today it is accepted that wildfires are a natural part of the ecosystem of wildlands, where, at the least, plants have evolved to survive fires by a variety of strategies (from possessing reserve shoots that sprout after a fire, to fire-resistant seeds), or even encourage fire (for example eucalypts contain flammable oils in the leaves) as a way to eliminate competition from less fire-tolerant species. Most native animals, too, are adept at surviving wildfires.

On occasions, wildfires have caused large-scale damage to private property, particularly when they have reached urban-fringe communities, destroying many homes and causing deaths.

Slash, small, rotten, mis-shapen, or otherwise undesirable wood discarded during logging, has historically provided the fuel for devastating fires such as the fires in Michigan in the 19th century.

The aftermath of a wildfire can be as disastrous if not more so than the actual fire itself. A particularly destructive fire burns away all the plants and trees which prevented erosion. If heavy rains occur after such a fire, landslides, ash flows, and flash floods are to be expected. Not only does this result in severe property damage for those living in the immediate fire area, but it also affects the quality of the local water supply.


Green Knoll Wildfire
in Jackson, Wyoming

Prevention

For many decades the policy of the United States Forest Service was to surpress all fires, and this policy was epitomized by the mascot Smokey the Bear and was also the basis of parts of the movie Bambi. The policy began to be questioned in the 1960s, when it was realized that no new sequoias had been grown in the redwood forests of California, because fire is an essential part of their life cycle. This produced the policy of controlled burns to reduce underbrush. This clears much of the undergrowth through forest and woodland areas, making travel and hunting much easier while reducing the risk of dangerous high-intensity fires caused by many years of fuel buildup.

However, the previous policy of absolute fire suppression in the United States had resulted in the buildup of fuel resulting in large and severe fires such as the fire in Yellowstone National Park in 1988. Urbanization can also result in fuel buildup and devastating fires, such as those in Los Alamos, New Mexico, East Bay Hills, within the California cities of Oakland and Berkeley, between October 19 and 22, 1991, all over Colorado in 2002, and throughout Southern California in October, 2003.

On average, wildfires burn 4.3 million acres (1.7 million hectares) in the United States annually. In recent years the federal government has spent $1 billion a year on fire suppression. 2002 was a record year for fires with major fires in Arizona, California, Colorado, and Oregon.

The risk of major wildfires can be reduced by reducing the amount of fuel present. In wildland, this can be accomplished by either conducting "controlled burns" - deliberately setting areas ablaze under less dangerous weather conditions in spring or autumn - or physical fuel removal by removing some trees as is conducted in many American forests. Both approaches are controversial with some environmentalists, who regard them as tampering with the forest ecosystem.

People living in fire-prone areas typically take a variety of precautions, including building their homes out of flame-resistant materials, reducing the amount of fuel near the home or property (including firebreaks - their own miniature control lines, in effect), and investing in their own firefighting equipment.

Rural farming communities are rarely threatened directly by wildfire. These types of communities are usually located in large areas of cleared, usually grazed, land, and in the drought conditions present in wildfire years there is often very little grass left on such grazed areas. Hence the risk is minimized. However, urban fringes have spread into forested areas, for example in Sydney and Melbourne, and communities have literally built themselves in the middle of highly flammable forests. These communities are at high risk of destruction in bushfires.

Fire suppression

Most fire-prone areas have large firefighter services to help control bushfires. As well as the water-spraying trucks most commonly used in urban firefighting, bushfire services use a variety of alternative techniques. They often possess aircraft, particularly helicopters, that can douse areas that are inaccessible to ground crews and deliver greater quantities of water and/or flame retardant chemicals. However, large fires are of such a size that no conceivable firefighting service could attempt to douse the whole fire directly, and so alternative techniques are used.

In alternative approaches, firefighters attempt to control the fire by controlling the area that it can spread to, by creating "control lines", which are areas that contain no combustible material. These control lines can be produced by physically removing fuel (for instance, with a bulldozer), or by "backburning", in which small, low-intensity fires are started to burn the flammable material in a (hopefully) controlled way. These may then be extinguished by firefighters, or, ideally, directed in such a way that they meet the main fire front, at which point both fires run out of flammable material and are thus extinguished.

Unfortunately, such methods can fail in the face of wind shifts causing fires to miss control lines or to jump straight over them (for instance, because a burning tree falls across a line, burning embers are carried by the wind over the line, or burning tumbleweeds cross the line).

The actual goals of firefighters vary. Protection of life (those of both the firefighters and "civilians") is given top priority, then private property according to economic and social value and also to its "savability" (for example, more effort will be expended on saving a house with a tile roof than one with a wooden-shake roof). In very severe, large fires, this is sometimes the only possible action. Protecting houses is regarded as more important than, say, farming machinery sheds, although firefighters, if possible, try to keep fires off farmland to protect stock and fences (steel fences are destroyed by the passage of fire, as the wire is irreversibly stretched and weakened by it). Preventing the burning of publicly-owned forested areas is generally of least priority, and, indeed, it is quite common (in Australia, at least) for firefighters to simply observe a fire burn towards control lines through forest rather than attempt to put it out more quickly - it is, after all, a natural process.

Famous wildfires in North America

External Links

Further Reading

  • Fire in America: A Cultural History of Wildland and Rural Fire, Stephen J. Pyne, Princeton University Press, 1982, hardcover, 654 pages, ISBN 0-691-08300-2
  • Year of the Fires, The Story of the Great Fires of 1910, Stephen J. Pyne, Viking Penguin, 2001, 320 pages, ISBN 0670899909
  • Ghosts of the Fireground: Echoes of the Great Peshtigo Fire and the Calling of a Wildland Firefighter, Peter M. Leschak, HarperSanFrancisco, 2002, hardback, 288 pages, ISBN 0062517775

Other Items Titled 'Wildfire'


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