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Bushfire

From Academic Kids

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Backburning in Townsville, Australia to prevent bushfires.

A bushfire is a wildfire that occurs in the forests, scrubs, woodlands or grasslands of Australia or New Zealand. In the south, bushfires tend to be most common and most severe, during summer and autumn, in drought years, and particularly in El Niņo years. In the north, bushfires usually occur during winter (the dry season), and fire severity tends to be more associated with seasonal growth patterns. Fire frequency in the north is difficult to assess, as the vast majority of fires are deliberately started by humans.

Bushfires are a natural part of the ecosystem, but a part that is much misunderstood.

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.

The natural fire regime was altered forever by the arrival of humans in Australia about 50,000 years ago. Fires became much more frequent, and fire-loving species — notably eucalypts — greatly expanded their range. It is assumed that a good deal of this change came about as the result of deliberate action by early humans, setting fires to clear undergrowth or drive game.

In the south, bushfires are most often started by lightning. However, near populated areas, accidents and arson cause many fires. In the north, most fires are deliberately lit.

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 inaccessible to ground crews. 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.

Typically, this involves controlling the area that the fire can spread to, creating control lines which are areas which contain no combustible material. These control lines can be produced by bulldozing, or by backburning — setting a small, low-intensity fire to burn the flammable material in a 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 be extinguished.

A year after the massive ,  remains almost devoid of animal life, but a thick carpet of  seedlings has sprouted in the ashes.
A year after the massive bushfires of 2003, Mt Buffalo remains almost devoid of animal life, but a thick carpet of Alpine Ash seedlings has sprouted in the ashes.

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 fires, this is sometimes the only possible action. Protecting houses is regarded as more important than, say, 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 is usually accomplished by conducting control burns — deliberately setting areas ablaze under less dangerous weather conditions in spring or autumn. Control burns are often controversial, both because they can be regarded as tampering with the forest ecosystem, and because many a serious fire has started as a control burn that got out of hand.

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 there is often very little grass left. However, urban fringes often spread into forested areas, and communities have literally built themselves in the middle of highly flammable forests.

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Smoke from bushfires can cover a large area, as seen here in eastern Victoria.

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, constructing firebreaks, and investing in firefighting equipment.

Bushfires have existed for as long as trees have been around. The kind of Australian trees that tend to burn most vigorously evolved millions of years ago to cope with the dry conditions as Continental Australia drifted slowly towards the equator. Ancient indigenous aboriginals learned through thousands of years to use controlled burning to encourage new growth of plants.

Some significant bushfire events

External links


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Major bushfires on Perth's outer suburbs shroud the city in heavy smoke for over a week. January 2005.
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