A
bushfire (also known as a Wildfire in the USA and Canada) is a fire that occurs in the bush
(collective term for scrub, woodland or grassland of
Australia, New Zealand
, New
Caledonia
). In
south east Australia, bushfires tend to be most common and most
severe during summer and autumn, in
drought
years, and particularly severe in
El
Niño years. Southeast Australia is fire prone, and warm and dry
conditions intensify the probability of fire. In the north of
Australia, bushfires usually occur during the dry season (April to
September), and fire severity tends to be more associated with
seasonal weather patterns. In the southwest, similarly, bushfires
occur in the summer dry season and severity is usually related to
seasonal growth. Fire frequency in the north is difficult to
assess, as the vast majority of fires are caused by human activity,
however
lightning strikes are as common a
cause as human ignited fires and
arson.
History
The natural fire regime was altered by the arrival of humans in
Australia. Fires became 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.
Plants have evolved a variety of strategies to survive (or even
require) bushfires, (possessing reserve shoots that sprout after a
fire, or developing fire-resistant or fire-triggered
seeds) or even encourage fire (
eucalypts contain flammable oils in the leaves) as
a way to eliminate competition from less fire-tolerant species.
Many native animals are also adept at surviving bushfires.
Bushfire control
Key factors affecting bushfires
• Fuel: Anything that burns is fuel for the fire: litter on the
ground (leaves, twigs, rubbish), undergrowth (shrubs, grass,
seedlings), trees and other vegetation, structures (such as houses)
and any other miscellaneous objects in the vicinity; gas bottles,
piles of firewood, tyres, etc. Ladder fuels are low growing
(30 cm to 2 metres) vegetation that offers a ladder for the
fire to rise to the canopies of trees.
• Weather: Weather is a major contributor to bushfires. The hotter
and dryer, the more likely it is for a bushfire to start and spread
uncontrollably. High winds will reduce humidity, and cause an
ongoing bushfire to spread more rapidly. Most bushfires start in
the afternoon, when it is driest and hottest.
• Topography/slope: The topography of the terrain is a major factor
in bushfire behaviour. Generally the fire spreads faster uphill.
Conversely, fire going downhill advances more slowly. The
superheated air is pushed in front of the fire drying and
pre-warming the fuel for ignition. When a fire progressing downhill
hits the flat at the bottom of the hill, the height of the flame
can quadruple, when the fire hits the undulating slope opposite,
the height may quadruple again. In other words, 1 metre flames
going downhill can turn into 4 metre flames at the bottom of the
hill, and to 16 metre flames starting to climb the next hill. While
the height of the flame depends mainly on the height of the fuel,
the former stands as a reminder that an innocent looking small
bushfire can rapidly change into a life threatening fire.
Firefighting methods
In
National Parks and reserves,
bushfire fighting is carried out by
professional staff, such as
Rangers, Park Workers, Field and Technical
Officers, with help from
volunteers from
rural areas. The rural areas have
bush
fire services, such as the
CFA (in Victoria), the
RFS (in NSW), largely
staffed by volunteers, to help control bushfires. As with large
fires on
public land it is common for
Parks staff and Rural or Country volunteers to work together on
large rural fires. On some occasions
urban firefighting professionals are also
called in to assist. As well as the water-spraying trucks commonly
used in urban firefighting, bushfire services often own or lease
aircraft, particularly
fire
helicopters, that can douse areas inaccessible to ground crews.
However, large fires are often 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, clearing 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.
Unfortunately, such methods can fail in the face of wind shifts
causing fires to miss control lines, or because fires jump 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
livestock 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 hazard reduction
controlled burns — deliberately setting
areas ablaze during favourable weather conditions in spring or
autumn. Controlled burns can be controversial, both because they
can be regarded as tampering with the forest
ecosystem, and because serious fires can be
started if a control burn gets out of hand. The
Australian Aborigines used controlled
burning to encourage new growth of plants in some areas.
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.
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.
People living in fire-prone areas 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.
Significant bushfires
Notable bushfire events
| Fire |
Location |
Hectares Burned |
Date |
Deaths |
Properties Damaged |
| Black Thursday
bushfires |
Victoria, Australia |
approximately 5 million ha |
6 February 1851 |
about 12 |
1 million sheep; thousands of cattle |
| Red Tuesday bushfires |
Victoria |
260,000 ha |
1 February 1898 |
12 |
2,000 buildings |
| 1926 bushfires |
Victoria |
|
February – March 1926 |
60 |
| Black Friday bushfires |
Victoria |
2,000,000 ha |
December 1938 – January 1939, peaking 13 January 1939 |
71 |
3,700 |
| 1944 Bushfires |
Victoria |
estimated 1 million ha |
14 January – 14 February 1944 |
15–20 |
more than 500 houses |
| 1951-2 Bushfires |
Victoria |
|
Summer 1951–52 |
at least 10 |
|
| Black Sunday Bushfires |
South Australia |
|
2 January 1955 |
2 |
|
| 1961 Western
Australian bushfires |
Western Australia |
|
January–March 1961 |
0 |
|
| 1962 bushfires |
Victoria |
|
14–16 January 1962 |
32 |
450 houses |
| Southern Highlands
bushfires |
New South Wales |
|
5–14 March 1965 |
3 |
59 homes |
| Tasmanian "Black Tuesday"
bushfires |
Tasmania |
Approximately 264,000 ha |
1967 |
62 |
1,293 homes |
| 1969 bushfires |
Victoria |
|
8 January 1969 |
23 |
230 houses |
| Northern Sydney
bushfires |
Sydney ,
NSW |
|
1979 |
|
|
| Ash Wednesday bushfires |
South Australia and Victoria |
418,000 ha |
16 February 1983 |
75 |
about 2,400 houses |
| 1994 Eastern seaboard
fires |
New South Wales |
|
27 December 1993 – 16 January 1994 |
4 |
225 homes |
| Dandenongs bushfire |
Victoria |
|
21 January 1997 |
3 |
33 homes |
| Lithgow bushfire |
New South Wales |
|
2 December 1997 |
2 |
|
| Linton bushfire |
Victoria |
|
1998 |
5 |
|
| Black Christmas |
New South Wales |
740,000 acres |
2001–02 |
0 |
121 homes |
| 2003 Canberra
bushfires |
Canberra , Australian
Capital Territory |
|
2003 |
4 |
almost 500 homes |
| 2003 Eastern
Victorian alpine bushfires |
Victoria |
over 1.3 million ha |
8 January – 8 March 2003 |
|
41 homes |
| Tenterden |
Western Australia |
|
December 2003 |
2 |
|
| Eyre Peninsula
bushfire |
South Australia |
145,000 ha |
2005 |
9 |
93 homes |
| 2006 Central Coast
bushfire |
Central Coast, New South
Wales |
|
New Years Day, 2006 |
|
|
Jail Break Inn Fire |
Junee, New South Wales |
30,000 ha |
New Years Day 2006 |
0 |
Livestock losses estimated to be over 20,000. Seven homes,
seven headers and four shearing
sheds destroyed. of fencing damaged. |
| Stawell New year fire |
Victoria |
|
December 2005 – January 2006 |
|
|
| Grampians Bushfire |
Victoria |
|
January 2006 |
3 |
|
Pulletop bushfire |
Wagga Wagga, New South Wales |
9,000 |
6 February 2006 |
0 |
2,500 sheep and 6 cattle killed, 3 vehicles and 2 hay sheds
destroyed as well as 50 km of fencing. |
| 2006-07
Australian bushfire season |
|
|
September 2006 – January 2007 |
|
|
| Kangaroo Island
Bushfires |
South Australia |
95,000 ha |
6–14 December 2007 |
1 |
|
| Black Saturday
bushfires |
Victoria |
450,000+ ha |
7 February 2009 – 14 March 2009 |
173 |
2,029+ houses, 2,000 other structures |
Bushfire gallery
Image:Gippsland, Sunday night, February 20th, 1898.jpg|A painting
depicting the
Red Tuesday
bushfires at
Gippsland.
Image:Wagga Wagga,
Pulleytop bushfire, February 6th, 2006.jpg|The Pulletop
bushfire at Wagga Wagga.Image:UminaFire1.JPG|One of the blazes of
the
2006 Central Coast
bushfires on
New Years Day, 2006.
Photo
taken at Umina Beach
.Image:Smoke_from_fire_near_holbrook_NSW.jpg|Smoke
from the bushfire near Holbrook
on 2 February 2007.
See also
Notes and references
- Flannery, T. (1994) "The future eaters" Reed Books
Melbourne.
- Wilson, B., S. Boulter, et al. (2000). Queensland's resources.
Native Vegetation Management in Queensland. S. L. Boulter, B. A.
Wilson, J. Westrupet eds. Brisbane, Department of Natural
Resources.
- White, M. E. 1986. The Greening of Gondwana. Reed Books,
Frenchs Forest, Australia.
- Black Thursday. Retrieved 10-2-2009.
- ABS. Retrieved 10-2-2009.
- Norther Daily Leader, "Some past bushfires in Australia, p.3,
10 February 2009
External links
Wikis
Quiz
Map
Search
