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The 2019/2020 mega-fires exposed Australian ecosystems to an unprecedented extent of high-severity fire

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posted on 19.04.2021, 07:10 by Luke CollinsLuke Collins, RA Bradstock, H Clarke, Michael ClarkeMichael Clarke, RH Nolan, TD Penman
Extreme fire seasons characterised by very large 'mega-fires' have demonstrably increased area burnt across forested regions globally. However, the effect of extreme fire seasons on fire severity, a measure of fire impacts on ecosystems, remains unclear. Very large wildfires burnt an unprecedented area of temperate forest, woodland and shrubland across south-eastern Australia in 2019/2020, providing an opportunity to examine the impact of extreme fires on fire severity patterns. We developed an atlas of wildfire severity across south-eastern Australia between 1988 and 2020 to test (a) whether the 2019/2020 fire season was more severe than previous fire seasons, and (b) if the proportion of high-severity fire within the burn extent (HSp) increases with wildfire size and annual area burnt. We demonstrate that the 2019/2020 wildfires in south-eastern Australia were generally greater in extent but not proportionally more severe than previous fires, owing to constant scaling between HSp and annual fire extent across the dominant dry-forest communities. However, HSp did increase with increasing annual fire extent across wet-forests and the less-common rainforest and woodland communities. The absolute area of high-severity fire in 2019/2020 (∼1.8 M ha) was larger than previously seen, accounting for ∼44% of the area burnt by high-severity fire over the past 33 years. Our results demonstrate that extreme fire seasons are a rare but defining feature of fire regimes across forested regions, owing to the disproportionate influence of mega-fires on area burnt.


L C was supported by Post-doctoral Fellowships at La Trobe University and Arthur Rylah Institute, and the University of Melbourne. We thank Dr Rebecca Gibson for compiling the vegetation mapping and assisting with validation of fire severity mapping in New South Wales. We thank Dr Ashley Sparrow for providing feedback on an earlier draft of the manuscript.


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Environmental Research Letters





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Institute of Physics (IoP) Publishing



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