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A bushfire is a firre burning out of control inthe open. Bushfires can burn using grass,scrub or forest (or a combination of these) forfuel. Unless quickly controlled, bushfirescan become large, spreading to affect forests,wildlife, crops, houses and other buildings,and human life. In Australia, some bushfireshave become major disasters.
Fires are not a recent occurrence in Australia.
Since the last Ice Age, bushfires have influencedthe development of the Australian land. Fires arean essential element in some Australian ecosystems,which need the intense heat of bushfires torelease the seeds from plants and replenishgrowth. Australian Aborigines used fires to assistthem in their hunting activities. It is believedthat the fire activities of Aborigines contributedto the development of an open woodland ecosystemin parts of south-eastern Australia.
Early European settlers used fire to assist inthe clearing of land for crops and as a means ofremoving stubble following cropping. However, inmore recent times, laws have been passedrestricting the lighting of fires for these purposes.
This has led to a more dense vegetation in manyrural areas and a greater accumulation of leaf andba rk litter on the ground. The litterprovides a significant amount of fuelfor fires if they do start.
Bushfires are one of the most destructiveforces of nature. Firefighters risktheir lives each year to control andeventually extinguish them. Eventhough bushfires can occur naturally,mainly as a result of lightning strikesand spontaneous combustion, most arestarted by the activities of people. Thisincludes cigarettes and matches beingcarelessly discarded, electricity cables,sparks from machinery and tools, andburning off. Arson has been the causeof some of the worst bushfires.
BUSHFIRESWHAT CAUSESBUSHFIRES?Eucalypts and bushfiresThere are two main types of bushfires:· Surface bushfires burn in grass, low shrubs andground litter. They can travel at high speed butare relatively easy to control.
· Crown bushfires occur when heat and flamesfrom a surface flre ignite the crowns of trees.
Crown fires spread rapidly if there are strong,hot winds and very dry vegetation. Hugeamounts of ¯ammable eucalyptus vapour,transpired from leaves, can create firebrandsthat engulf the tree crowns ahead of the firefront. This makes crown fires very dangerousand difficult to control.
As the map shows, bushfires usually occurin the less arid parts of Australia. Aridareas tend not to have enough fuel to sustainfires for any length of time. SoutheasternAustralia is particularly subject tobushfires. There are several reasons for this,including the following:1. Large areas are covered with sclerophyll vegetation.
The dominant trees are eucalypts,which have highly flammable oil in theirbranches. Eucalypts burn readily and canbecome so hot during fires that their sap boilsand the whole tree or shrub can explode inflames. This is not a problem for the plantspecies as most eucalypt varieties burn hotand fast as a means of releasing seeds onto thefire-cleared ground. Some burnt trees simplysend up new shoots from their stumps or rootsand grow to full-size trees again.
2. The area is also subject to prolonged periods ofbelow average rainfall and droughts. Many ofthe most severe bushfires have occurredduring droughts and El Niño events. Bushfiresand drought often occur together.
3. South-eastern Australia is also subject toheatwaves and strong northerly winds duringthe summer months. Two or three days ofheatwave weather can often provide conditionssuitable for bushfires to occur.
Bushfires can bring massive destruction, loss oflife and personal hardship to families and communities.
Individuals, community-based groupsand governments have responded to this hazardin many ways.
There are over 70 000 individuals who are volunteermembers of bushfire brigades. They domost of the fighting of bushfires. During times ofsevere bushfires they can be on duty for days at atime, sometimes facing extreme danger. Theymake a highly significant contribution to makingour communities safer.
The government has set up many agenciesthat work to protect the community when bush-fires occur. These include ®re brigades, police andambulance services, welfare agencies and theState Emergency Service. Governments can provideemergency financial assistance in severebushfires. The Bureau of Meteorology providesshort- and long-term weather forecasts to warnof bushfire dangers.