Understanding Wildfire Patterns in the South-Eastern Australia

Abstract

Wildfires affect ecological processes, threaten human lives and cause economic losses. Understanding of fire patterns is required to better support the planning of sustainable fire management and risk reduction activities. Fire occurrence and fire size are two essential fire pattern components that describe the distribution of fires and the impacts of fires on landscapes and ecosystems. They vary substantially within and between regions due to variation in weather, fuel, topography and ignition sources. In this thesis, remotely sensed and administrative records as well as Generalised Linear Models and Generalised Additive Models have been used to understand fire occurrence patterns in the south-eastern part of Australia, as well as to obtain knowledge on the patterns of fire occurrence and fire size in the inland semi-arid riverine area.

The results suggest that in the south-eastern Australia, wildfires are more likely to occur in mountainous areas, forests, savannas, and in areas with high vegetation coverage and near human infrastructures, while they are less likely to occur on grasslands and shrublands. Environmental variables are strong individual predictors while anthropogenic variables contribute more to the final model. Fire-ignition drivers and their effects vary across ecoregions. There are non-linear relationships between the probability of fire ignition and some of its drivers e.g. the Normalized Difference Vegetation Index.

This study also reveals that on the NSW side of the Riverina bioregion, human-caused fires mostly occur in spring and summer while natural fires are clustered in summer. Forested wetlands and dry lands experience summer and spring-summer fire regime, respectively. Fire probabilities are higher in forested wetlands than in dry lands and in areas with intermediate inundation frequencies. Weather, fuel and ignition sources are comparably important in regulating human-caused ignitions, while weather contributes more than fuel in driving natural ignitions. Larger-size Fires that burned Entirely in forested Wetlands (FEW) are associated with higher ambient rainfall conditions of the 6th, 13-14th and 17-18th months before fires. Fire danger index is more powerful than other ambient weather factors in explaining the FEW size. The contributing and the most effective factors become different when fires burned in dry lands are incorporated.