Abstract
Fire activity in Australia is strongly affected by high inter-annual climate variability and extremes. Through changes in the climate, anthropogenic climate change has the potential to alter fire dynamics. Here we compile satellite (19 and 32 years) and ground-based (90 years) burned area datasets, climate and weather observations, and simulated fuel loads for Australian forests. Burned area in Australia’s forests shows a linear positive annual trend but an exponential increase during autumn and winter. The mean number of years since the last fire has decreased consecutively in each of the past four decades, while the frequency of forest megafire years (>1 Mha burned) has markedly increased since 2000. The increase in forest burned area is consistent with increasingly more dangerous fire weather conditions, increased risk factors associated with pyroconvection, including fire-generated thunderstorms, and increased ignitions from dry lightning, all associated to varying degrees with anthropogenic climate change.
Highlights
Fire activity in Australia is strongly affected by high inter-annual climate variability and extremes
Along the latitudinal increasing temperature gradient from South to North (Tasmania, Victoria, New South Wales, and Queensland), we find that the largest relative growth of burned area between the early (1988–2002) and later (2003-2019) periods of the record occurred in the southern coolest parts of the forest distribution (Tasmania) and the northern warmest parts of the forest distribution (Queensland), with Queensland showing the largest absolute difference of the two
The growth in burned area is exponential for the autumn-winter period, the largest absolute seasonal contributions to the increase were in spring and summer. These trends show a lengthening of the fire season towards the cooler seasons, where limited fire activity occurred in the early part of the satellite 32year record
Summary
Fire activity in Australia is strongly affected by high inter-annual climate variability and extremes. Fire, including cultural burns by indigenous people, has shaped the function and structure of most Australian ecosystems for millennia[10,11] Against this background of fire activity, Australia’s mean temperature has increased by 1.4 °C since 1910 with a rapid increase in extreme heat events, while rainfall has declined in the southern and eastern regions of the continent, during. 600 400 200 a Australia b Forest (fire year) the cool half of the year[12,13,14] These changes can affect the four components that must simultaneously come together for fire to occur: biomass production, its availability to burn (fuel loads), fire weather, and ignition[7], making Australian forests vulnerable and sensitive to changes in fire activity
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