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Divergent responses of fire to recent warming and drying across south-eastern Australia

Authors

  • Ross Bradstock,

    Corresponding author
    1. Centre for Environmental Risk Management of Bushfires, Institute for Conservation Biology and Management, University of Wollongong, Wollongong, NSW, Australia
    • Correspondence: Ross Bradstock, tel. + 61 2 42215531, fax + 61 2 42215395, e-mail: rossb@uow.edu.au

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  • Trent Penman,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia
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  • Matthias Boer,

    1. Hawkesbury Institute for the Environment, University of Western Sydney, Penrith, NSW, Australia
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  • Owen Price,

    1. Centre for Environmental Risk Management of Bushfires, Institute for Conservation Biology and Management, University of Wollongong, Wollongong, NSW, Australia
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  • Hamish Clarke

    1. Climate and Atmospheric Science Section, NSW Office of Environment and Heritage, Climate Change Research Centre and ARC Centre of Excellence for Climate Systems Science, The University of New South Wales, Sydney, NSW, Australia
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Abstract

The response of fire to climate change may vary across fuel types characteristic of differing vegetation types (i.e. litter vs. grass). Models of fire under climatic change capture these differing potential responses to varying degrees. Across south-eastern Australia, an elevation in the severity of weather conditions conducive to fire has been measured in recent decades. We examined trends in area burned (1975–2009) to determine if a corresponding increase in fire had occurred across the diverse range of ecosystems found in this part of the continent. We predicted that an increase in fire, due to climatic warming and drying, was more likely to have occurred in moist, temperate forests near the coast than in arid and semiarid woodlands of the interior, due to inherent contrasts in the respective dominant fuel types (woody litter vs. herbaceous fuels). Significant warming (i.e. increased temperature and number of hot days) and drying (i.e. negative precipitation anomaly, number of days with low humidity) occurred across most of the 32 Bioregions examined. The results were mostly consistent with predictions, with an increase in area burned in seven of eight forest Bioregions, whereas area burned either declined (two) or did not change significantly (nine) in drier woodland Bioregions. In 12 woodland Bioregions, data were insufficient for analysis of temporal trends in fire. Increases in fire attributable mostly to warming or drying were confined to three Bioregions. In the remainder, such increases were mostly unrelated to warming or drying trends and therefore may be due to other climate effects not explored (e.g. lightning ignitions) or possible anthropogenic influences. Projections of future fire must therefore not only account for responses of different fuel systems to climatic change but also the wider range of ecological and human effects on interactions between fire and vegetation.

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