High-severity wildfires in temperate Australian forests have increased in extent and aggregation in recent decades

Abstract

Wildfires have increased in size and frequency in recent decades in many biomes, but have they also become more severe? This question remains under-examined despite fire severity being a critical aspect of fire regimes that indicates fire impacts on ecosystem attributes and associated post-fire recovery. We conducted a retrospective analysis of wildfires larger than 1000 ha in south-eastern Australia to examine the extent and spatial pattern of high-severity burned areas between 1987 and 2017. High-severity maps were generated from Landsat remote sensing imagery. Total and proportional high-severity burned area increased through time. The number of high-severity patches per year remained unchanged but variability in patch size increased, and patches became more aggregated and more irregular in shape. Our results confirm that wildfires in southern Australia have become more severe. This shift in fire regime may have critical consequences for ecosystem dynamics, as fire-adapted temperate forests are more likely to be burned at high severities relative to historical ranges, a trend that seems set to continue under projections of a hotter, drier climate in south-eastern Australia.

The Effect of Antecedent Fire Severity on Reburn Severity and Fuel Structure in a Resprouting Eucalypt Forest in Victoria, Australia

“…These findings are consistent with a growing body of evidence showing that high-severity canopy-disturbing fires cause transitions towards fuel states with greater ignitability and propensity to burn at a high severity [14,30,68]. There is evidence that the increasing frequency of severe fire weather has already driven the contraction of interfire intervals and increased the area affected by high severity fire across large areas of south-eastern Australia [83][84][85]. These changes to fire weather and fire regimes, coupled with increased canopy fuel connectivity resulting from exposure to high-severity fire, have likely increased the propensity for high-severity fires across areas of southern Australia.…”

A New Application of the Disturbance Index for Fire Severity in Coastal Dunes

“…Coastal dunes are dynamic and resilient systems that are continually adjusting to disturbances and extreme events [125]. The stratigraphy-based research suggesting dune destabilisations after fires [62][63][64][65][66][67][68][69][70][71] has not been confirmed by contemporary observations [32,33,53], but the consequences of increasing frequency [30] and severity [8] of fires may result in altered landscape morphology and dominant vegetation communities [10]. Specific to Kangaroo Island, the highly fire-adapted vegetation community is likely a result of the evolution in its fire regime since colonisation.…”

“…Fires are an ordinary, recurring, and integral part of ecosystems around the globe and across many parts of Australia [1], and provide many benefits to ecosystems [2][3][4]. Shifts in fire regimes (frequency and severity) are associated with climate change, extreme weather events, and drought [5][6][7][8], and may alter vegetation succession [9,10] or landscape stability [11]. Fire severity is a measurement of the effects of fire on landscapes and can be irregular within a burnt area due to variation in fuel loads, fuel type, weather conditions, topography, or maturity of the plant community [12,13].…”

FIRELAN—An Ecologically Based Planning Model towards a Fire Resilient and Sustainable Landscape. A Case Study in Center Region of Portugal

“…Large-scale rural fires are a worldwide problem that has been studied in the most fire-prone regions of the world, such as North America [1], Australia [2] and Europe [3], with several methodological approaches [4]. In Europe, the Mediterranean region has been the most affected area by rural fires in the last decades [5].…”