Bushfire

They 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 where fallen branches, leaves, and other material can dry out and becomes highly flammable. Bushfires tend to be most common, and most severe, during years of drought, and occur on days of strong winds.

Bushfires are a natural part of the ecosystems in these areas, 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 (in the case of eucalypts, containing flammable oils in the leaves) as a way to eliminate competition from less fire-tolerant species. Most native animals, too, are adept at surviving bushfires.

At least some of the indigenous inhabitants of Australia accelerated this process of regular burning by deliberately torching sections of their home ranges at intervals. This cleared much of the undergrowth through forest and woodland areas, making travel and hunting much easier and reduced the risk of dangerous high-intensity fires caused by many years of fuel buildup.

Bushfires are most often started by lightning. However, near populated areas, accidents or arson, mostly by mentally disturbed individuals, causes many fires.

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. 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 which contain no combustible material. These control lines can be produced by physically removing it (for instance, with a bulldozer[?]), or by "backburning", where 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 away so that they meet the main fire front, at which point both fires will run out of flammable material and will thus be extinguished.

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

The actual goals of firefighters vary. Protection of life (both the firefighters and "civilians") is given top priority, then private property according to economic and social value. In very severe, large fires, this is sometimes the only possible action. Protecting houses is regarded as more important than, say, farming machinery sheds, though firefighters, if possible, will 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.

The risk of major bushfires can be reduced by reducing the amount of fuel present. In forests, 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.

Contrary to urban understanding of bushfire, rural farming communities are comparatively rarely threatened directly by them. They are usually located in the middle of large areas of cleared, usually grazed, land, and in the drought conditions present in bushfire years they is often very little grass, dead or alive, left on such grazed areas. Hence the risk is minimised. However, urban fringes have, for example in Sydney and Melbourne, spread into forested areas, and communities have literally built themselves in the middle of highly flammable forests. These communities are at high risk of destruction in bushfires.

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

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

Some significant bushfire events:

• Ash Wednesday bushfires[?] (1982)

See Also: Forest fire