Abstract
The 2019–2020 'Black Summer' wildfires in Australia, a series of megafires and gigafires, represent an unprecedented escalation in both the area burned and the extent of high-severity burns compared to historical fires, prompting an evaluation of their ecological impacts. Fires of this magnitude homogenize the ecosystem, altering available resources for flora and fauna survival, and reshaping ecosystem dynamics. This thesis investigates the responses of ecosystems to such fires, focusing on refining the definition of 'megafire,' assessing the role of common wombat (Vombatus ursinus) burrows as refuges post-wildfire, and evaluating the effects of fire severity on biodiversity and animal behaviour. The overarching goal is to better understand adaptive strategies and resilience or resistance patterns among both native and introduced species in the face of unprecedented wildfires.
Chapter one provides the introduction to the thesis and each of the data chapters. Chapter two: Clarifies the term 'megafire' through a structured review of its usage across the peer-reviewed literature in numerous languages, highlighting variability in size thresholds and geographic occurrences. The term 'megafire' is predominantly applied to fires exceeding 10,000 ha, with significant ecological implications. As climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we proposed a definition of megafire as fires over 10,000 ha.
Chapter three: Explores the ecological role of common wombat burrows in providing refuge to other species after wildfires, employing camera traps to track changes in animal abundance in response to fire. Common wombat burrows serve as ecological refuges that predominantly support native species. Burrows were increasingly utilised by some native species as fire severity increased, suggesting burrows play an important post-fire refuge. Species that were found to utilise burrows tended to be smaller. Therefore, common wombat burrows might aid the survival and resilience of species in fire-affected areas.
Chapter four: Studies the impact of fire severity on vegetation and animal species at a site scale. Vegetation responded strongly to fire severity, with high-severity fires leading to the pronounced changes in vegetation. Fire severity had a modest effect on animal species, with a greater number of species responding to areas burned at high severity. However, few species responded negatively to fire severity, suggesting many species were resilient to fire. The diel activity of animal species in response to fire generally showed a reallocation of their active periods, becoming more pronounced at specific times in burnt areas, suggesting behavioural plasticity
Chapter five: Investigates the impact of fire severity on terrestrial fauna at a landscape scale, assessing community resilience and predator-prey dynamics in fire-affected landscapes. Most native species did not respond to areas burnt with varying extents of high severity, unburnt vegetation, or pyrodiversity. Although landscapes affected by high severity fire had higher richness of introduced species. This suggests widespread resilience or resistance among species to wildfire, potentially facilitated by evolutionary adaptations to fire as a disturbance.
The findings of this thesis highlight the importance of having standardised terminology and the ecological impacts of the 2019–2020 wildfires, revealing how altered fire regimes due to climate change affect biodiversity and ecosystems. Ensuring consistent, standardised terminology to describe ‘megafire’, especially with the increasing frequency and intensity of wildfires, aids the reporting of increasingly large fires in the future. Following an unprecedented wildfire, findings indicate that common wombat burrows serve as important post-fire refuges. While many species exhibited widespread resilience or resistance by not responding to fire severity at a site and landscape scale, others displayed altered diel activity, suggesting that behavioural plasticity is crucial for some species to persist after a fire. This research has underscored the ecological roles of wombat burrows as effective refuges post-fire and has advanced our understanding of species' responses to fire severity. These findings underscore the necessity for refined fire management strategies that integrate species-specific management plans, which are crucial for mitigating the increasingly severe impacts of wildfires. Chapter six discusses these conclusions in a broader context and proposes future research directions to further explore species-specific responses and adaptive strategies in fire-prone ecosystems.
Chapter one provides the introduction to the thesis and each of the data chapters. Chapter two: Clarifies the term 'megafire' through a structured review of its usage across the peer-reviewed literature in numerous languages, highlighting variability in size thresholds and geographic occurrences. The term 'megafire' is predominantly applied to fires exceeding 10,000 ha, with significant ecological implications. As climate and ecosystems change, it is important that scientists can communicate trends in the occurrence of larger and more extreme fires with clarity. To overcome ambiguity, we proposed a definition of megafire as fires over 10,000 ha.
Chapter three: Explores the ecological role of common wombat burrows in providing refuge to other species after wildfires, employing camera traps to track changes in animal abundance in response to fire. Common wombat burrows serve as ecological refuges that predominantly support native species. Burrows were increasingly utilised by some native species as fire severity increased, suggesting burrows play an important post-fire refuge. Species that were found to utilise burrows tended to be smaller. Therefore, common wombat burrows might aid the survival and resilience of species in fire-affected areas.
Chapter four: Studies the impact of fire severity on vegetation and animal species at a site scale. Vegetation responded strongly to fire severity, with high-severity fires leading to the pronounced changes in vegetation. Fire severity had a modest effect on animal species, with a greater number of species responding to areas burned at high severity. However, few species responded negatively to fire severity, suggesting many species were resilient to fire. The diel activity of animal species in response to fire generally showed a reallocation of their active periods, becoming more pronounced at specific times in burnt areas, suggesting behavioural plasticity
Chapter five: Investigates the impact of fire severity on terrestrial fauna at a landscape scale, assessing community resilience and predator-prey dynamics in fire-affected landscapes. Most native species did not respond to areas burnt with varying extents of high severity, unburnt vegetation, or pyrodiversity. Although landscapes affected by high severity fire had higher richness of introduced species. This suggests widespread resilience or resistance among species to wildfire, potentially facilitated by evolutionary adaptations to fire as a disturbance.
The findings of this thesis highlight the importance of having standardised terminology and the ecological impacts of the 2019–2020 wildfires, revealing how altered fire regimes due to climate change affect biodiversity and ecosystems. Ensuring consistent, standardised terminology to describe ‘megafire’, especially with the increasing frequency and intensity of wildfires, aids the reporting of increasingly large fires in the future. Following an unprecedented wildfire, findings indicate that common wombat burrows serve as important post-fire refuges. While many species exhibited widespread resilience or resistance by not responding to fire severity at a site and landscape scale, others displayed altered diel activity, suggesting that behavioural plasticity is crucial for some species to persist after a fire. This research has underscored the ecological roles of wombat burrows as effective refuges post-fire and has advanced our understanding of species' responses to fire severity. These findings underscore the necessity for refined fire management strategies that integrate species-specific management plans, which are crucial for mitigating the increasingly severe impacts of wildfires. Chapter six discusses these conclusions in a broader context and proposes future research directions to further explore species-specific responses and adaptive strategies in fire-prone ecosystems.
Original language | English |
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Qualification | Doctor of Philosophy |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 07 Nov 2024 |
Place of Publication | Australia |
Publisher | |
Publication status | Published - 14 Nov 2024 |