Fire in Australia's forests

The extent and intensity of forest fires vary with latitude and seasonal rainfall. In northern Australia, where conditions are generally humid (see figure), low-intensity fires often burn across large areas. In contrast, hot, dry and windy summers in the 'southern mesic' rainfall zone of southern Australia mean that bushfires there are often intense and difficult to control. Such fires can cause large losses of human life, destroy community assets such as trees, buildings, fences, bridges and power lines, and greatly reduce water quality.

Rainfall classification showing 10 geographic regions that vary markedly in seasonal rainfall distribution

Planned and unplanned fire

Fire burned an estimated 24.7 million hectares of forest in the five-year period to 2005-06, of which 19.5 million hectares was in northern Australia and 5.2 million hectares in southern Australia. Of the total, an estimated 20.0 million hectares was burned by unplanned fire (bushfire) and 4.7 million hectares by planned fire (e.g. prescribed burning). The northern semi-humid and east coast semi-humid rainfall zones had the highest proportions of planned fires as a proportion of total area burned (45.4% and 34.5%, respectively).

Bushfires in southern Australia during the period caused soil erosion and reduced water quality in many important catchments. The resulting natural regrowth is also expected to reduce water yields in affected catchments for decades. The 2002-03 fire season in southern Australia was particularly bad, largely because it occurred during a period of severe drought. In New South Wales, 1.46 million hectares of vegetation was burned over 151 days between September 2002 and February 2003. In Victoria, 1.1 million hectares of forest was burned, including about 20,000 hectares of tall alpine ash forest. In the Australian Capital Territory, a severe fire in January 2003 burnt 157,000 hectares, including 11,000 hectares of pine plantation, and destroyed 500 homes. The table on page 1 lists large or landscape-scale bushfires (sometimes called mega-fires) that occurred in southern Australia between 1993 and 2007.

Climate change

Climate change could have serious implications for the frequency and severity of bushfires in Australia. When predicted changes in rainfall are combined with increases in potential evaporation due to higher temperatures, a general decrease in available soil moisture is projected across Australia. There is some evidence that the observed warming trend in Australia has already contributed to increased drought severity through higher evaporation and water demand. Native forests in many locations are expected to experience more stress due to higher temperatures and lower moisture availability and become more susceptible to fire and other pressures. In recent years there has been an increase in the number of people living at the urban/forest interface, often in areas prone to bushfire. The management of fire in these zones for both biodiversity conservation and the protection of assets has therefore become a major challenge for Australian forest and fire managers, particularly on the east coast. Many jurisdictions now require that the risk of bushfire is considered in urban planning and the design of houses and other buildings. However, prescribed burning - a technique used in many forests to reduce the risk of bushfire - is becoming more costly and the opportunity to undertake prescribed burns may be reduced by increased climate variability.

Further reading

Bartlett T, Leonard M and Morgan G (2007). The megafire phenomenon: some Australian perspectives. In: The 2007 Institute of Foresters of Australia and New Zealand Institute of Forestry Conference: Programme, Abstracts and Papers, Institute of Foresters of Australia, Canberra.

Dexter B and Hodgson A (2005). The Facts Behind the Fire, Forest Fire Victoria, Melbourne.

Ellis, S, Kanowski, P and Whelan, R (2004). National Inquiry on Bushfire Mitigation and Management. Commonwealth of Australia, Canberra.

Hennessy K, Lucas C, Nicholls N, Bathols, J Suppiah, R and Ricketts J. (2005). Climate Change Impacts on Fire Weather in South-eastern Australia, CSIRO Marine and Atmospheric Research, Aspendale.

MIG (2008). Criterion 3 - Maintenance of ecosystem health and vitality, State of the Forests Report 2008. Montreal Process Implementation Group for Australia, Canberra.

Russell-Smith J, Yates C, Whitehead P, Smith R, Craig R, Allan G, Thackway R, Frakes I, Cridland S, Meyer M and Gill A (2007). Bushfires 'down under': patterns and implications of contemporary Australian landscape burning. International Journal of Wildland Fire 16:361-377.

Wareing K and Flinn D (2003). The Victorian Alpine Fires January-March 2003, Department of Sustainability and Environment, Melbourne.