Fuels of the future : the challenge of new fuel types

Landscape disturbances associated with human activities result in many changes in vegetation structure and floristics. These changes include invasion of native vegetation by both introduced and native species, which leads to the development of 'new' vegetation types. These new vegetation types are often associated with greatly increased fuel loads, and increased levels of fire hazard. Two of these 'new' fuel types are dense thickets of woody weeds, such as Coyote Bush (Baccharis pilularis) and swards of exotic grasses with very high fuel loads, such as Buffel Grass (Cenchrus ciliaris) and Para Grass (Urochloa mutica). The 'new' fuel types which can now be recognized have significant implications for the accuracy of fire behaviour prediction and modelling. For example, modelling fire behaviour in areas invaded by exotic grasses in Australia is problematic, as current grassland fire behaviour models do not allow for the input ofthe high fuel loads associated with these invasive grasses. In forest, McArthur Forest Fire Danger Meters may not be appropriate for forests with significant levels of elevated fuels. Two case studies from southeastern Australia are discussed: the invasion of native vegetation in the urban interface by the woody shrub Burgan (Kunzea ericoides) and invasion of native grasslands by Phalaris (Phalaris aquatica).