State of the Environment

2006

Indicator: LD-24 Severe drought and wildfire correlation

Data

No research has come to light in which the spatial and temporal wildfire data have been correlated with spatial and temporal drought data at a continental level. However, a paper produced by CSIRO Marine and Atmospheric Research, Bushfire CRC and Australian Bureau of Meteorology found, on the basis of studies of a number of sites in south eastern Australia, that an increase in fire-weather risk is likely at most sites, including the average number of days when the fire danger index rating is very high or extreme. The combined frequencies of days with very high and extreme fire danger index ratings are likely to increase 4-25% by 2020 and 15-70% by 2050. For example, the fire danger index results indicate that Canberra is likely to have an annual average of 25.6-28.6 very high or extreme fire danger days by 2020 and 27.9-38.3 days by 2050, compared to a present average of 23.1 days. The increase in fire-weather risk is generally largest inland. Tasmania is likely to be relatively unaffected.

Source: K. Hennessy, C. Lucas N. Nicholls J. Bathols, R. Suppiah and J. Ricketts, Climate change impacts on fire-weather in south-east Australia, CSIRO Marine and Atmospheric Research Bushfire CRC and Australian Bureau of Meteorology.

The Parliamentary Inquiry into the 2003 Australian bushfires also recognizes that more frequent and severe fires occur during periods of extended drought combined with high temperatures.

Source: the House of Representatives Select Committee on the Recent Australian Bushfires 2003, A Nation Charred: Inquiry into the Recent Australian Bushfire.

What the data mean

Since 1950, rainfall has decreased in south-east Australia, droughts have become more severe and the number of extremely hot days has risen. The effect of these changes on fire frequency and intensity is not evident, although it is clear that hotter and drier years have greater fire risk.

Data Limitations

Fire weather is only one of the important factors determining fire risk and fire behaviour. Fuels, terrain and suppression were not assessed in the CSIRO report. The study from A Nation Charred looked at the relationship between weather and fire but did not attempt to speculate on changing fire patterns resulting from long term changes in climate.

Issues for which this is an indicator and why

Land - Contributions and pressures between the land and the atmosphere - Climate 

The indicator would plot, temporally and spatially, positively and/or negatively, the correlation between severe drought and wildfire.

Altered fire regimes are a significant pressure on the land and its biodiversity that may result from changes in climate, particularly changed drought patterns. In the shorter term, extended periods of drought or more frequent drought will increase fire risk with hotter, faster fires because the land cover is present but dry. In the longer term, as vegetation disappears altogether, the fire risk is likely to decline because there is nothing to burn.

Ideally the indicator would also correlate location of fire and drought and control for other land cover changes or changes to the management of native vegetation.

Other indicators for this issue:

Biodiversity - Pressures on biodiversity - Fire 

Climate driven changes in fire patterns have significant implications for viability of vegetation types and for biodiversity more generally.

Other indicators for this issue:

Biodiversity - Pressures on biodiversity - Climate variability 

Changes in fire regimes may result from changes in climate, compounding the impacts of changing climate on biodiversity.

Other indicators for this issue:

Further Information

Key

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