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Fire regimes are changing across the globe in response to complex interactions between climate, fuel, and fire across space and time. Despite these complex interactions, research into predicting fire regime change is often unidimensional, typically focusing on direct relationships between fire activity and climate, increasing the chances of erroneous fire predictions that have ignored feedbacks with, for example, fuel loads and availability. Here, we quantify the direct and indirect role of climate on fire regime change in eucalypt dominated landscapes using a novel simulation approach that uses a landscape fire modelling framework to simulate fire regimes over decades to centuries. We estimated the relative roles of climate-mediated changes as both direct effects on fire weather and indirect effects on fuel load and structure in a full factorial simulation experiment (present and future weather, present and future fuel) that included six climate ensemble members. We applied this simulation framework to predict changes in fire regimes across six temperate forested landscapes in south-eastern Australia that encompass a broad continuum from climate-limited to fuel-limited. Climate-mediated change in weather and fuel was predicted to intensify fire regimes in all six landscapes by increasing wildfire extent and intensity and decreasing fire interval, potentially led by an earlier start to the fire season. Future weather was the dominant factor influencing changes in all the tested fire regime attributes: area burnt, area burnt at high intensity, fire interval, high-intensity fire interval, and season midpoint. However, effects of future fuel acted synergistically or antagonistically with future weather depending on the landscape and the fire regime attribute. Our results suggest that fire regimes are likely to shift across temperate ecosystems in south-eastern Australia in coming decades, particularly in climate-limited systems where there is the potential for a greater availability of fuels to burn through increased aridity.

Merging fires are known as destructive fires resulting in loss of life and houses. Despite growing efforts in the past decade to understand merging fires, there are still many knowledge gaps about their behaviour, especially at the field scale. In this study, we conducted experimental harvested crop burns in Victoria, Australia, in March and April 2021 to better understand thermal behaviour of merging fire fronts. UAVs with visual and thermal cameras were used to capture high-resolution fire propagation and the combustion process of merging fires. During experiments 50 junction fire fronts (32 forward and 18 backward) and 24 coalescence fire fronts were studied. For thermal analysis, 15 forward and 4 backward junction fire fronts, 6 coalescence fire fronts, and 10 parallel fire fronts were considered. Special methods were developed to process IR footages and compare the combustion process of merging fires and linear fire fronts (head and back fires). To do this, regions of interest (ROIs) containing the merging fire and linear fire front were selected in each frame using FLIR Research Studio. The ROIs were then exported using as bitmask images together with radiometric JPEG image containing both fires. Using the R programming platform, we determined the length and shape of the perimeter of fires for each JPEG image and defined buffer zones within the fire perimeter inside the ROI for each fire for further pixel temperature analysis. Thermal analysis showed that for forward junction fires the median temperature of head linear fire fronts was higher than forward junction fires except towards the end of merging. While in backward junction fires, the proportion of pixels with high temperature was much higher than in back linear fire fronts, indicating much larger burning areas. The temperature distributions of coalescence and parallel fires showed a decrease in the number of high-temperature pixels toward the end of the merge for coalescence and throughout for parallel fires. The fire behaviour observed in the field experiments demonstrates the necessity for better understanding of merging of fire fronts and the relationship between fuel, weather and fire line interaction.

Wildfires are a common threat to the sustainability of commercial plantations in fire-prone regions. Large losses of plantations from wildfires can lead to the disruption of forest yield, with flow-on impacts to downstream industries, resulting in significant social and economic impacts to local communities. Future climate projections indicate an increase in wildfire activity, including increases in fire extent, severity or frequency in many fire-prone ecosystems. Land and fire management agencies around the world invest significant resources to reduce the likelihood and impact of future fires and increase the capacity for fire suppression. However, we currently know very little about how commercial plantations will be impacted by fire as the climate changes, or if strategic management can mitigate some of these risks into the future. In this study we sought to quantify fire risks to plantations and nearby community assets under current and changing climates; and to evaluate the effectiveness of management options for mitigating some of these risks under changing climates. This research included the customisation of a fire simulation tool for use in plantation landscapes by developing plantation-specific fuel functions (derived from field-sampling in hardwood and softwood plantations around Australia) that were integrated into fire spread models. To quantify longer-term risks, these advancements were also integrated into a stochastic fire regime simulator (FROST– Fire Regimes and Operation Simulation Tool) that is proposed for future use in operational risk assessments. Fire risks to both environmental and community assets were evaluated under current and changing climates to support evidence-based management to help guide investment, insurance negotiations, and fire mitigation in the plantation sector. The fire regime simulator (FROST) was also used to evaluate a range of different management options for reducing risk as a basis for efficient allocation of fire prevention and response resources both by plantation growers and by broader fire regions. We found that reducing suppression response times (to 15 minutes or less for all ignitions) and the current approach to management (a construction rate of 2km/h for suppression and 15-minute response times, with 4000ha/year of prescribed burning) were consistently the best management strategies for reducing fire risks to plantations and adjacent communities, regardless of the climate model used. These strategies offer the greatest scope for reducing future wildfire risks to plantation assets and adjacent communities as the climate changes. High pruning in strategic locations may also be worthy of future investment but should be considered in combination with more rapid suppression and prescribed burning. Plantation owners currently have little influence over the amount and location of prescribed burning adjacent to plantations, and fuel reduction burning is not regularly undertaken in Australian plantations. Therefore, rapid suppression response times is the single best investment for minimising impact to plantation assets under a hotter or drier climate.

Fire regimes are changing around the world raising important questions about the risks to biodiversity. Fire seasons are lengthening, high-severity fires are occurring more often and in unexpected places. Extensive research examines some of the fire related risks to life and property. However, in the fire risk research space there is often limited or simplified inclusion of ecological values. Future fire regimes, alongside climatic change, could have profound impacts on biodiversity conservation and ecosystem function. For example, plant population trajectories can be influenced by demographic traits, disturbance regimes and environmental variables such as climate. Climate change can affect all three and is likely to impact on plant populations through altering natural fire regimes as well as influencing species demographic traits. These changes are unlikely to be unidirectional with some plant types benefiting and others being disadvantaged. Here, we examine the impacts of climate change both on the shifts in fire regimes alone and combined with predicted climate-induced demographic shifts. We use two functional plant types (obligate seeder, facultative resprouter) in a number of case-study areas representing woodland-dominated landscapes of south-eastern Australia. We link a fire regime simulation tool with a spatially explicit population viability analysis model. We simulate fire regimes under six different future climates representing different temperature and precipitation shifts, and 16 demographic change scenarios, characterised by changes to individual or multiple plant demographic processes. Obligate seeder species were predicted to be less resilient to changes in demographic parameters. However, both resprouter and seeder species were found to be negatively affected by the combined impacts of changes to multiple demographic parameters or to a combination of a shifting fire regime and changes to demographic traits, particularly through simulated reductions in adult survival. To our knowledge this is the first study to integrate fire regime simulations with spatially explicit population viability analyses. Such an approach significantly increases our ability to identify which functional types are most at risk of population extinction under predicted fire regime and demographic changes. This flexible framework is an important first step in exploring the complex interactions that determine plant viability under a changing climate and will increase our ability to prioritise research and fire management for biodiversity into the future.

Anthropogenic climate change is a key threat to global biodiversity. To inform strategic actions aimed at conserving biodiversity as climate changes, conservation planners need early warning of the risks faced by different species. The IUCN Red List criteria for threatened species are widely acknowledged as useful risk assessment tools for informing conservation under constraints imposed by limited data. However, doubts have been expressed about the ability of the criteria to detect risks imposed by potentially slow-acting threats such as climate change, particularly because criteria addressing rates of population decline are assessed over time scales as short as 10 years. We used spatially explicit stochastic population models and dynamic species distribution models projected to future climates to determine how long before extinction a species would become eligible for listing as threatened based on the IUCN Red List criteria. We focused on a short-lived frog species (Assa darlingtoni) chosen specifically to represent potential weaknesses in the criteria to allow detailed consideration of the analytical issues and to develop an approach for wider application. The criteria were more sensitive to climate change than previously anticipated; lead times between initial listing in a threatened category and predicted extinction varied from 40 to 80 years, depending on data availability. We attributed this sensitivity primarily to the ensemble properties of the criteria that assess contrasting symptoms of extinction risk. Nevertheless, we recommend the robustness of the criteria warrants further investigation across species with contrasting life histories and patterns of decline. The adequacy of these lead times for early warning depends on practicalities of environmental policy and management, bureaucratic or political inertia, and the anticipated species response times to management actions.