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The cause of large areas of treeless Sedgeland and Scrub communities in western Tasmania, one of the wettest regions of Australia, has long puzzled ecologists, given the climatic suitability for temperate Eucalyptus and rainforests. A pervasive theory, known as the ecological drift model, is that landscape fires have created a dynamic mosaic of fire-adapted and fire-sensitive vegetation. A contrary view, known as the fire cycle model, asserts that fire patterns are a consequence, not a cause, of the mosaics, which are edaphically determined. We leveraged the opportunity presented by a large wildfire that occurred in a Sedgeland tract surrounded by Eucalyptus forest in the Huon Valley in 2019 to help discriminate between these competing models. Specifically, we sought to determine whether there was any evidence that the Sedgeland was becoming infilled with Scrub prior to the 2019 fire, and whether the fire caused the Scrub community to convert to Sedgeland. A field survey was used to assess the mortality of shrubs and their regeneration following the 2019 fire, and we used dendrochronology to determine the age of the fire-killed shrubs. We also used historical aerial photography since the 1980s to map fire scars and the distribution of Sedgeland and Scrub. We found that fire killed most shrubs in the Sedgeland and Scrub communities and initiated a cohort of shrub regeneration. Dendrochronological analysis of the fire-killed shrubs revealed that most were established approximately 40 years ago, following a fire that is apparent from aerial photography and most likely occurred around 1983. An analysis of aerial photography revealed that since 1980, the distribution of the Scrub community has remained stable, although the density of shrubs declined following the 1983 fire. The recovery of the burned Scrub areas in 1983 and the rapid regeneration of the shrubs following the 2019 fire is more consistent with the fire cycle model than the ecological drift model. These findings concord with the demonstrated stability of the Eucalyptus forest boundary at this site revealed by a separate study. The slow growth of the shrubs cautions against frequently burning Sedgelands, because it could cause the collapse of shrub populations by killing the immature cohort initiated by fire.

Fire is a major cause of tree injury and mortality worldwide, yet our current understanding of fire effects is largely based on ocular estimates of stem charring and foliage discoloration, which are error prone and provide little information on underlying tree function. Accurate quantification of physiological performance is a research and forest management need, given that declining performance could help identify mechanisms of—and serve as an early warning sign for—mortality. Many previous efforts have been hampered by the inability to quantify the heat flux that a tree experiences during a fire, given its highly variable nature in space and time. In this study, we used a dose–response approach to elucidate fire impacts by subjecting Pinus monticola var. minima Lemmon and Pseudotsuga menziesii (Mirb.) Franco var. glauca (Beissn.) Franco saplings to surface fires of varying intensity doses and measuring short-term post-fire physiological performance in photosynthetic rate and chlorophyll fluorescence. We also evaluated the ability of spectral reflectance indices to quantify change in physiological performance at the individual tree crown and stand scales. Although physiological performance in both P. monticola and P. menziesii declined with increasing fire intensity, P. monticola maintained a greater photosynthetic rate and higher chlorophyll fluorescence at higher doses, for longer after the fire. Pinus monticola also had complete survival at lower fire intensity doses, whereas P. menziesii had some mortality at all doses, implying higher fire resistance for P. monticola at this life stage. Generally, individual-scale spectral indices were more accurate at quantifying physiological performance than those acquired at the stand-scale. The Photochemical Reflectance Index outperformed other indices at quantifying photosynthesis and chlorophyll fluorescence, highlighting its potential use to quantify crown scale physiological performance. Spectral indices that incorporated near-infrared and shortwave infrared reflectance, such as the Normalized Burn Ratio, were accurate at characterizing stand-scale mortality. The results from this study were included in a conifer cross-comparison using physiology and mortality data from other dose–response studies. The comparison highlights the close evolutionary relationship between fire and species within the Pinus genus, assessed to date, given the high survivorship of Pinus species at lower fire intensities versus other conifers.

Savanna fire management is a topic of global debate, with early dry season burning promoted as a large-scale emissions reduction opportunity. To date, discussions have centred on carbon abatement efficacy, biodiversity and cultural benefits and/or risks. Here we use a case study of Darwin, Australia to highlight smoke pollution as another critical consideration. Smoke pollution from savanna fires is a major public health issue, yet absent so far from discussions of program design. Here, we assess the likely impacts of increased early dry season burning on smoke pollution in Darwin between 2004 and 2019, spanning the introduction and expansion of carbon abatement programs. We found increased smoke pollution in the early dry season but little change in the late dry season, contributing to a net annual increase in air quality standard exceedances. Geospatial analysis suggests this relates to increased burning in the path of early dry season trade winds. This study highlights the complex health trade-offs involved with any large-scale prescribed burning, including for carbon abatement.

There is mounting concern that global wildfire activity is shifting in frequency, intensity, and seasonality in response to climate change. Fuel moisture provides a powerful means of detecting changing fire potential. Here, we use global burned area, weather reanalysis data, and the Canadian fire weather index system to calculate fuel moisture trends for multiscale biogeographic regions across a gradient in vegetation productivity. We quantify the proportion of days in the local fire season between 1979 and 2019, where fuel moisture content is below a critical threshold indicating extreme fire potential. We then associate fuel moisture trends over that period to vegetation productivity and comment on its implications for projected anthropogenic climate change. Overall, there is a strong drying trend across realms, biomes, and the productivity gradient. Even where a wetting trend is observed, this often indicates a trend toward increasing fire activity due to an expected increase in fuel production. The detected trends across the productivity gradient lead us to conclude global fire activity will increase with anthropogenic climate change.

Ongoing European suppression of Aboriginal cultural land management since early-nineteenth century colonisation is widely thought to have caused major transformations across all Australian landscapes, including vegetation thickening, severe fires and biodiversity declines. However, these effects are often confounded in the densely settled southern Australia due to European land transformation. Landscapes currently under conservation and national park management in Tasmania are generally less disturbed, providing an opportunity to track ecosystem changes caused by the removal of Aboriginal peoples following colonisation in southern Australia. We use a multi-proxy palaeoecological technique and the analysis of historical aerial photography to investigate these changes in Cape Pillar, southeast Tasmania. Results reveal a major ecological shift following European colonisation, with the replacement of stable, open wet heathland characterised by minor fires (active cultural land use) with dense dry scrub characterised by major fires (cessation of cultural land use). We also discuss potential background role of regional climatic shifts in the observed ecological changes. Management programmes designed to restore open heathland pre-colonial cultural ecosystem would help reduce the risk of large fires in Cape Pillar.

Athrotaxis cupressoides is an iconic Tasmanian palaeoendemic conifer that is vulnerable to fire. A survey of three populations burnt by severe fire in 2016, conducted 1 year post-fire, found 33% of stems were still alive, with many surviving stems suffering some canopy scorch. We re-surveyed these populations to quantify delayed mortality, resprouting, and presence of juveniles, and to determine whether fire impacts can be reliably assessed after 1 year. We applied three measures of fire severity: canopy scorched, canopy consumed, and the minimum burnt twig diameter of neighbouring shrubs. We found overall stem survival in 2020 was 31%, and that 97% of stems that were dead 4 years post-fire had died within the first year. Our best predictor of stem mortality was percentage canopy scorched. Overall, 1.8% of burnt stems resprouted, but severely burnt stems did not resprout. Juveniles were present ~9.9% of burnt trees in 2017, and only 1.8% in 2020. We conclude that A. cupressoides stems are not unusually fire sensitive, but rather, that the species’ vulnerability to severe fire results from its lack of reliable recovery mechanisms. This study shows that fire-caused mortality can be reliably assessed 1 year post-fire, and possibly earlier. Interventions such as sowing seed or transplanting seedlings could be necessary to re-establish fire-killed populations.

The 2019-20 wildfires in eastern Australia presented a globally important opportunity to evaluate the respective roles of climatic drivers and natural and anthropogenic disturbances in causing high-severity fires. Here, we show the overwhelming dominance of fire weather in causing complete scorch or consumption of forest canopies in natural and plantation forests in three regions across the geographic range of these fires. Sampling 32% (2.35 Mha) of the area burnt we found that >44% of the native forests suffered severe canopy damage. Past logging and wildfire disturbance in natural forests had a very low effect on severe canopy damage, reflecting the limited extent logged in the last 25 years (4.5% in eastern Victoria, 5.3% in southern New South Wales (NSW) and 7.8% in northern NSW). The most important variables determining severe canopy damage were broad spatial factors (mostly topographic) followed by fire weather. Timber plantations affected by fire were concentrated in NSW and 26% were burnt by the fires and >70% of the NSW plantations suffered severe canopy damage showing that this intensive means of wood production is extremely vulnerable to wildfire. The massive geographic scale and severity of these Australian fires is best explained by extrinsic factors: an historically anomalous drought coupled with strong, hot dry westerly winds that caused uninterrupted, and often dangerous, fire weather over the entire fire season.

The relationships between productivity, fire frequency and fire severity shape the distribution of plant communities globally. Dry forests are expected to burn frequently and wet forests to burn infrequently. However, the effect of productivity on intensity and severity of wildfire is less consistent and poorly understood. One productive ecosystem where this is especially true is the Australian tall wet Eucalyptus‐dominated forest (TWEF), which spans wet areas across the continent. This study aims to characterise how climate shapes the likelihood of low‐ and high‐severity wildfire across Australian TWEF. We performed a continental‐scale analysis of fuels in 48 permanent plots in early‐mature stage TWEF across four climate regions in Australia. We estimated fuel loads and measured understorey microclimate. We then obtained historical fire‐weather observations from nearby meteorological stations and used fuel moisture and fire behaviour equations to predict the historical frequency with which TWEF could burn and what fire severities were expected. We investigated how this varies across the different TWEF climate regions. Lastly, we validated our approach by remeasuring eight plots that burned unexpectedly post‐measurement. We found that surface fuels in cooler, moister regions were available to burn 1-16 days per year historically, with only low‐severity, surface fire possible most of these days: high‐severity fire was only possible under rare, extreme fire‐weather conditions. However, in warmer, drier regions, fuels were available to burn 23-35 days annually, and high‐severity fire was more likely than low‐severity fire. Validation showed that we slightly overestimated flame heights, inflating high‐severity risk estimates. If we used elevated fuel loads to predict flame heights, however, high‐severity fire was more likely than low‐severity fire everywhere. Lastly, the likelihood of high‐severity fire increased with increasing temperature and worsening fire weather. Synthesis. Fire activity in early‐mature TWEF is limited by climatic constraints on fire weather and availability to burn, with high‐severity fire more likely in warmer, drier regions than in cooler, wetter ones. This indicates a particularly worrisome vulnerability to climate change, given TWEF's diminished ability to recover from disturbance in a warmer world. The occurrence of both low‐ and high‐severity fire means the fire regimes of TWEF are best described as mixed severity.

Achieving sustainable coexistence with wildfires in the Anthropocene requires skilful integrated fire observations, fire behaviour predictions, forecasts of fire risk, and projections of change to fire climates. The diverse and multiscale approaches used by the atmospheric sciences, to understand geographic patterns, temporal trends and likely trajectories of weather and climate, provide a role model for how multiscale assessments of fire danger can be formulated and delivered to fire managers, emergency responders and at-risk communities. Adaptation to escalating risk of fire disasters requires specialised national agencies, like weather services, that provide to provide a diverse range of products to enable detection and near and longer-range prediction of landscape fire activity.

Globally, collapse of ecosystems—potentially irreversible change to ecosystem structure, composition and function—imperils biodiversity, human health and well‐being. We examine the current state and recent trajectories of 19 ecosystems, spanning 58° of latitude across 7.7 M km2, from Australia's coral reefs to terrestrial Antarctica. Pressures from global climate change and regional human impacts, occurring as chronic ‘presses’ and/or acute ‘pulses’, drive ecosystem collapse. Ecosystem responses to 5–17 pressures were categorised as four collapse profiles—abrupt, smooth, stepped and fluctuating. The manifestation of widespread ecosystem collapse is a stark warning of the necessity to take action. We present a three‐step assessment and management framework (3As Pathway Awareness, Anticipation and Action) to aid strategic and effective mitigation to alleviate further degradation to help secure our future.

Background Climate change is projected to increase environmental health hazard risks through fire-related air pollution and increased airborne pollen levels. To protect vulnerable populations, it is imperative that evidence-based and accessible interventions are available. The environmental health app, AirRater, was developed in 2015 in Australia to provide information on multiple atmospheric health hazards in near real time. The app allows users to view local environmental conditions, and input and track their personal symptoms to enable behaviors that protect health in response to environmental hazards. Objective This study aimed to develop insights into users’ perceptions of engagement, comprehension, and trust in AirRater to inform the future development of environmental health apps. Specifically, this study explored which AirRater features users engaged with, what additional features or functionality needs users felt they required, users’ self-perception of understanding app information, and their level of trust in the information provided. Methods A total of 42 adult AirRater users were recruited from 3 locations in Australia to participate in semistructured interviews to capture location- or context-specific experiences. Participants were notified of the recruitment opportunity through multiple avenues including newsletter articles and social media. Informed consent was obtained before participation, and the participants were remunerated for their time and perspectives. A preinterview questionnaire collected data including age range, any preexisting conditions, and location (postcode). All participant data were deidentified. Interviews were recorded, transcribed, and analyzed using thematic analysis in NVivo 12 (QSR International). Results Participants discussed app features and functionality, as well as their understanding of, and trust in, the information provided by the app. Most (26/42, 62%) participants used and valued visual environmental hazard features, especially maps, location settings, and hazard alerts. Most (33/42, 78%) found information in the app easy to understand and support their needs, irrespective of their self-reported literacy levels. Many (21/42, 50%) users reported that they did not question the accuracy of the data presented in the app. Suggested enhancements include the provision of meteorological information (eg, wind speed or direction, air pressure, UV rating, and humidity), functionality enhancements (eg, forecasting, additional alerts, and the inclusion of health advice), and clarification of existing information (eg, symptom triggers), including the capacity to download personal summary data for a specified period. Conclusions Participants’ perspectives can inform the future development of environmental health apps. Specifically, participants’ insights support the identification of key elements for the optimal development of environmental health app design, including streamlining, capacity for users to customize, use of real time data, visual cues, credibility, and accuracy of data. The results also suggest that, in the future, iterative collaboration between developers, environmental agencies, and users will likely promote better functional design, user trust in the data, and ultimately better population health outcomes.

Background Uncontrolled wildfires in Australian temperate Eucalyptus forests produce significant smoke emissions, particularly carbon dioxide (CO2) and particulates. Emissions from fires in these ecosystems, however, have received less research attention than the fires in North American conifer forests or frequently burned Australian tropical savannas. Here, we use the 2013 Forcett–Dunalley fire that caused the first recorded pyrocumulonimbus event in Tasmania, to understand CO2 and particulate matter (PM2.5) emissions from a severe Eucalyptus forest fire. We investigate the spatial patterns of the two emissions using a fine scale mapping of vegetation and fire severity (50 m resolution), and utilising available emission factors suitable for Australian vegetation types. We compare the results with coarse-scale (28 km resolution) emissions estimates from Global Fire Emissions Database (GFED) to determine the reliability of the global model in emissions estimation. Results The fine scale inventory yielded total CO2 emission of 1.125 ± 0.232 Tg and PM2.5 emission of 0.022 ± 0.006 Tg, representing a loss of 56 t CO2 ha−1 and 1 t PM2.5 ha−1. The CO2 emissions were comparable to GFED estimates, but GFED PM2.5 estimates were lower by a factor of three. This study highlights the reliability of GFED for CO2 but not PM2.5 for estimating emissions from Eucalyptus forest fires. Our fine scale and GFED estimates showed that the Forcett–Dunalley fire produced 30% of 2013 fire carbon emissions in Tasmania, and 26–36% of mean annual fire emissions for the State, representing a significant single source of emissions. Conclusions Our analyses highlight the need for improved PM2.5 emission factors specific to Australian vegetation, and better characterisation of fuel loads, particularly coarse fuel loads, to quantify wildfire particulate and greenhouse gas emissions more accurately. Current Australian carbon accountancy approach of excluding large wildfires from final GHG accounts likely exaggerates Tasmania’s claim to carbon neutrality; we therefore recommend that planned and unplanned emissions are included in the final national and state greenhouse gas accounting to international conventions. Advancing these issues is important given the trajectory of more frequent large fires driven by anthropogenic climate change.

Globally, land- and fire-management policies have counterproductively caused cascading ecosystem changes that exacerbate, rather than mitigate, wildfires. Given rapidly changing climate and land-use conditions that amplify wildfire risk, a policy shift to adaptive management of fire regimes is urgently needed.

In flammable landscapes around the globe, longer fire seasons with larger, more severely burnt areas are causing social and economic impacts that are unsustainable. The Australian 2019–20 fire season is emblematic of this trend, burning over 8 million ha of predominately Eucalyptus forests over a six-month period. We calculated the wildfire-smoke-related health burden and costs in Australia for the most recent 20 fire seasons and found that the 2019–20 season was a major anomaly in the recent record, with smoke-related health costs of AU$1.95 billion. These were driven largely by an estimated 429 smoke-related premature deaths in addition to 3,230 hospital admissions for cardiovascular and respiratory disorders and 1,523 emergency attendances for asthma. The total cost was well above the next highest estimate of AU$566 million in 2002–03 and more than nine times the median annual wildfire associated costs for the previous 19 years of AU$211 million. There are substantial economic costs attributable to wildfire smoke and the potential for dramatic increases in this burden as the frequency and intensity of wildfires increase with a hotter climate. Worldwide, longer fire seasons are causing unsustainable impacts. This study finds that the 2019–20 Australia fire season caused health-related costs of AU$1.95 billion, nine times the median for the previous 19 years.

Fire behaviour research has largely focused on dry ecosystems that burn frequently, with far less attention on wetter forests. Yet, the impacts of fire in wet forests can be high and therefore understanding the drivers of fire in these systems is vital. We sought to identify and rank by importance the factors plausibly driving flammability in wet eucalypt forests, and describe relationships between them. In doing so, we formulated a set of research priorities. Conceptual models of forest flammability in wet eucalypt forests were elicited from 21 fire experts using a combination of elicitation techniques. Forest flammability was defined using fire occurrence and fireline intensity as measures of ignitability and heat release rate, respectively. There were shared and divergent opinions about the drivers of flammability in wet eucalypt forests. Widely agreed factors were drought, dead fine fuel moisture content, weather and topography. These factors all influence the availability of biomass to burn, albeit their effects and interactions on various dimensions of flammability are poorly understood. Differences between the models related to lesser understood factors (e.g. live and coarse fuel moisture, plant traits, heatwaves) and the links between factors. By documenting alternative conceptual models, we made shared and divergent opinions explicit about flammability in wet forests. We identified four priority research areas: (1) quantifying drought and fuel moisture thresholds for fire occurrence and intensity, (2) modelling microclimate in dense vegetation and rugged terrain, (3) determining the attributes of live vegetation that influence forest flammability, (4) evaluating fire management strategies.

Extreme fires have substantial adverse effects on society and natural ecosystems. Such events can be associated with the intense coupling of fire behaviour with the atmosphere, resulting in extreme fire characteristics such as pyrocumulonimbus cloud (pyroCb) development. Concern that anthropogenic climate change is increasing the occurrence of pyroCbs globally is driving more focused research into these meteorological phenomena. Using 6 min scans from a nearby weather radar, we describe the development of a pyroCb during the afternoon of 4 January 2013 above the Forcett–Dunalley fire in south-eastern Tasmania. We relate storm development to (1) near-surface weather using the McArthur forest fire danger index (FFDI) and the C-Haines index, the latter of which is a measure of the vertical atmospheric stability and dryness, both derived from gridded weather reanalysis for Tasmania (BARRA-TA); and (2) a chronosequence of fire severity derived from remote sensing. We show that the pyroCb rapidly developed over a 24 min period on the afternoon of 4 January, with the cloud top reaching a height of 15 km. The pyroCb was associated with a highly unstable lower atmosphere (C-Haines value of 10–11) and severe–marginally extreme (FFDI 60–75) near-surface fire weather, and it formed over an area of forest that was severely burned (total crown defoliation). We use spatial patterns of elevated fire weather in Tasmania and fire weather during major runs of large wildfires in Tasmania for the period from 2007 to 2016 to geographically and historically contextualise this pyroCb event. Although the Forcett–Dunalley fire is the only known record of a pyroCb in Tasmania, our results show that eastern and south-eastern Tasmania are prone to the conjunction of high FFDI and C-Haines values that have been associated with pyroCb development. Our findings have implications for fire weather forecasting and wildfire management, and they highlight the vulnerability of south-east Tasmania to extreme fire events.

Australian mammals have exhibited exceptionally high rates of decline since European settlement 230 years ago with much focus on small mammals in northern tropical savannas. In these systems, little scientific attention has been given to the suite of grazing macropods, family Macropodidae, (common wallaroo (Osphranter robustus), antilopine wallaroo (O. antilopinus) and agile wallaby (Notamacropus agilis)). These species may be impacted by feral herbivores and contemporary fire regimes, two threats linked to small mammal declines. A multi‐scale approach using aerial surveys, road surveys and camera trapping was utilised to determine the effects of feral cattle and fire on the distribution and abundance of large macropods in the North Kimberley bioregion. Feral cattle density and biomass exceeded that of macropods regardless of survey technique. Density estimates for cattle were up to 125 times higher (0.3–10.0 km-2) than estimates for macropods (0.08–0.49 km-2). Cattle biomass, based on the aerial survey estimates (corrected for perception bias), were 15 and 95 times higher than macropods for infertile (279 vs. 19 kg km-2) and fertile savannas (518 vs. 5 kg km-2), respectively. Proximity to the nearest pastoral station was a significant predictor of the aerial sightings of feral cattle (P ≤ 0.05). Abundance and foraging activity of cattle were positively associated (P ≤ 0.05) with recently burnt areas. In contrast, camera trapping showed agile wallaby and wallaroo occurrence and foraging were associated with longer unburnt areas (P ≤ 0.05). Agile wallaby and wallaroo were negatively associated with cattle (P ≤ 0.05) and showed substantial diurnal and seasonal separation consistent with an antagonistic interspecific interaction. Results also suggest that the agile wallaby is the primary prey of the dingo, not wallaroo. Collectively, this study suggests that recent landscape changes such as altered fire regimes and introduced herbivores have negatively impacted large grazing macropod species.

Previous analyses of historical aerial photography and satellite imagery have shown thickening of woody cover in Australian tropical savannas, despite increasing fire frequency. The thickening has been attributed to increasing precipitation and atmospheric CO2 enrichment. These analyses involved labour‐intensive, manual classification of vegetation, and hence were limited in the extent of the areas and the number of measurement times used. Object‐based, semi‐automated classification of historical sequences of aerial photography and satellite imagery has enabled the spatio‐temporal analysis of woody cover over entire landscapes, thus facilitating measurement, monitoring and attribution of drivers of change. Using this approach, we investigated woody cover change in 4000 ha of intact mesic savanna in the Ranger uranium lease and surrounding Kakadu National Park, using imagery acquired on 10 occasions between 1950 and 2016. Unlike previous studies, we detected no overall trend in woody cover through time. Some variation in cover was related to rainfall in the previous 12 months, and there were weak effects of fire in the year of image acquisition and the antecedent 4 years. Our local‐scale study showed a mesic eucalypt savanna in northern Australia has been resilient to short‐term variation in rainfall and fire activity; however, changes in canopy cover could have occurred in other settings. When applying this semi‐automated approach to similar studies of savanna dynamics, we recommend maximising the time depth and number of measurement years, standardising the time of year for image acquisition and using many plots of 1 ha in area, rather than fewer, larger plots.

Australian Aboriginal cultures are globally recognised for using patchy and low intensity fires to sustainably manage landscapes and promote biodiversity [...]

We introduce the AusTraits database - a compilation of values of plant traits for taxa in the Australian flora (hereafter AusTraits). AusTraits synthesises data on 448 traits across 28,640 taxa from field campaigns, published literature, taxonomic monographs, and individual taxon descriptions. Traits vary in scope from physiological measures of performance (e.g. photosynthetic gas exchange, water-use efficiency) to morphological attributes (e.g. leaf area, seed mass, plant height) which link to aspects of ecological variation. AusTraits contains curated and harmonised individual- and species-level measurements coupled to, where available, contextual information on site properties and experimental conditions. This article provides information on version 3.0.2 of AusTraits which contains data for 997,808 trait-by-taxon combinations. We envision AusTraits as an ongoing collaborative initiative for easily archiving and sharing trait data, which also provides a template for other national or regional initiatives globally to fill persistent gaps in trait knowledge., Measurement(s)plant traitTechnology Type(s)digital curationSample Characteristic - OrganismViridiplantaeSample Characteristic - LocationAustralia Machine-accessible metadata file describing the reported data: 10.6084/m9.figshare.14545755

Background Pollen is a well-established trigger of asthma and allergic rhinoconjunctivitis, yet key gaps in our understanding remain. These include knowledge of concentration thresholds for symptoms, exposure-response associations through time, and the potential for interactions with other environmental stressors such as air pollution. Smartphone technology offers an opportunity to address these challenges using large datasets that capture individual symptoms in real time. Methods We analysed 44,820 symptom reports logged by 2,272 users of the AirRater app over four years to evaluate associations between daily respiratory symptoms and atmospheric concentrations of pollen in Tasmania, Australia. We used case time series, a novel methodology developed for app-sourced data. We adjusted for seasonality and meteorology and tested for interactions with particulate pollution (PM2.5). Results There was a non-linear association between pollen concentrations and respiratory symptoms for up to three days following exposure. Risk ratios (RR) were greatest on the same day, for total pollen increased steeply to a RR of 1.31 (95% CI: 1.26-1.37) at a concentration of 50 grains/m3 before plateauing. Associations with individual pollen taxa showed similar non-linear trends. There was an interaction with PM2.5, with effect estimates significantly higher when PM2.5 was >50 µg/m3 (p for interaction < 0.001). Conclusions The association between respiratory symptoms and airborne pollen was non-linear, greatest in magnitude on the day of exposure, and synergistic with air pollution. Key messages Smartphone symptom tracking offers a useful means of assessing dose-response relationships in environmental epidemiology.

Australian montane sclerophyll shrubland vegetation is widely considered to be resilient to infrequent severe fire, but this may not be the case in Tasmania. Here, we report on the vegetative and seedling regeneration response of a Tasmanian non-coniferous woody montane shrubland following a severe fire, which burned much of the Great Pine Tier in the Central Plateau Conservation Area during the 2018–2019 fire season when a historically anomalously large area was burned in central Tasmania. Our field survey of a representative area burned by severe crown fire revealed that more than 99% of the shrubland plants were top-killed, with only 5% of the burnt plants resprouting one year following the fire. Such a low resprouting rate means the resilience of the shrubland depends on seedling regeneration from aerial and soil seedbanks or colonization from plants outside the burned area. Woody species’ seedling densities were variable but generally low (25 m−2). The low number of resprouters, and reliance on seedlings for recovery, suggest the shrubland may not be as resilient to fire as mainland Australian montane shrubland, particularly given a warming climate and likely increase in fire frequency.

The temperate island of Tasmania is a global centre of plant endemism, with relictual lineages that persist in topographically rugged, wet and cool refugia. An iconic example of these palaeoendemic plants is the slow‐growing conifer, Athrotaxis cupressoides D. Don (Cupressaceae). The geographic range of A. cupressoides has shrunk since European settlement because of destructive anthropogenic fires. Inscription of the Tasmanian Wilderness World Heritage Area in 1982 provided formal protection for Tasmania's palaeoendemic taxa, but they remain vulnerable to lightning‐ignited landscape fires, which are becoming more frequent due to climate change. We surveyed stands across the species’ range and found that stands damaged by fires in the 20th century had higher grass cover and were more exposed to hot northerly winds than unburnt stands. A recruitment bottleneck was evident, with juveniles absent in 28% of unburnt and 47% of burnt transects. Transects on small islands in lakes had lower herbivore densities and less evidence of fire than comparable mainland transects. However, the island transects had lower densities of A. cupressoides seedlings and saplings, despite similar densities of adult trees, suggesting factors other than fire and herbivory contribute to the poor regeneration. We also studied the effects of a lightning fire in 2016, finding it killed 68% of stems overall, with stems less than 30 cm diameter and those scarred by previous fires more likely to die. These findings of high adult mortality and poor regeneration following fire suggest that the geographic range of A. cupressoides will contract due to the increasing frequency of lightning‐ignited fires. Management responses to the increasing risk of landscape fires now include establishment of seed banks, restoration planting and use of irrigation to protect stands from active fires, in addition to rapid suppression of ignitions and targeted planned burning to reduce fuel loads in surrounding flammable vegetation.

Aim: Understanding past distributions of people across the landscape is key to understanding how people used, affected and related to the natural environment. Here, we use habitat suitability modelling to represent the landscape distribution of Tasmanian Aboriginal archaeological sites and assess the implications for patterns of past human activity. Location: Tasmania, Australia. Methods: We developed a RandomForest ‘habitat suitability' model of site records in the Tasmanian Aboriginal Heritage Register. We applied a best‐effort bias correction, considered 31 predictor variables relating to climate, topography and resource proximity, and used a variable selection procedure to optimize the final model. Model uncertainty was assessed via bootstrapping and we ran an analogous MaxEnt model as a cross‐validation exercise. Results: The results from the RandomForest and MaxEnt models are highly congruent. The strongest environmental predictors of site occurrence include distance to coast, elevation, soil clay content, topographic roughness and distance to inland water. The highest habitat suitability scores are distributed across a wide range of environments in central, northern and eastern Tasmania, including coastal areas, inland water body margins and forests and savannas in the drier parts of Tasmania. With the exception of coastal areas much of western Tasmania has low habitat suitability scores, consistent with theories of low‐density Holocene Tasmanian Aboriginal settlement in this region. Main conclusions: Our modelling suggests Tasmanian Aboriginal people occupied a heterogeneity of habitats but targeted coastal areas around the whole island, and drier, less steep and/or open forest and savanna environments in the central lowlands. The western interior was identified as being rarely used by Aboriginal people in the Holocene, with the exception of isolated pockets of habitat; yet whether this is a true reflection of Aboriginal‐resourceuse demands increased archaeological surveys, particularly in the Tasmanian Wilderness World Heritage Area.

Fine fuel moisture content (FFMC) is a key determinant of wildfire occurrence, behaviour, and pyrogeographic patterns. Accurate determination of FFMC is laborious, hence managers and ecologists have devised a range of empirical and mechanistic measures for FFMC. These FFMC measures, however, have received limited field validation against field-based gravimetric fuel moisture measurements. Using statistical modelling, we evaluate the use of the relationship between gravimetric FFMC and the Fuel Moisture Index (FMI), based on Hygrochron iButton humidity and temperature dataloggers. We do this in Tasmanian wet and dry Eucalyptus forests subjected to strongly contrasting disturbance histories and, hence, percentage of canopy cover. We show that 24 h average FMI based on data from Hygrochron iButtons 0.75 m above the forest floor provides reliable estimates of gravimetric litter fuel moisture (c. 1 h fuels) that are strongly correlated with near surface gravimetric fuel moisture sticks (c. 10 h fuels). We conclude FMI based on Hygrochron iButton data provides ecologists with an economic and effective method to retrospectively measure landscape patterns in fuel moisture in Tasmanian forests.

Sleeper populations of non-native species can remain at low abundance for decades before irrupting. For over a century, fallow deer ( Dama dama ) in the island state of Tasmania, Australia, remained at low abundance and close to the region in which they were released. Recently, there are indications the population has increased in abundance and distribution. Here, we spatially quantify the population change using a time series of annual spotlight counts from 1985 to 2019 (total of 5,761 counts). Next, we predict the potential for further range expansion, using global occurrences to characterise the species’ climatic niche, and remote-camera surveys (n = 3,225) to model fine-grained habitat suitability. Spotlight counts of fallow deer increased by 11.5% annually, resulting in a 40-fold increase from 1985 to 2019. The core distribution increased 2.9-fold during this 35-year period, and now spans c. 27% of Tasmania’s land area. Satellite populations have established in locations where farmed deer have escaped or been released, suggesting that humans have facilitated some of the range expansion via new introduction events. Based on climate and habitat suitability, our models predict that 56% of Tasmania is suitable under the current climate. This suggests range expansion is likely to continue unless the population is actively managed, which could include the eradication of satellite populations and containment of core populations. This case study cautions that despite over a century of slow population growth, sleeper populations of non-native species can abruptly increase.

Fire risk can be defined as the probability that a fire will spread across a landscape, that therefore determines the likely area burnt by a wildfire. Reliable monitoring of fire risk is essential for effective landscape management. Compilation of fire risk records enable identification of seasonal and inter-annual patterns and provide a baseline to evaluate the trajectories in response to climate change. Typically, fire risk is estimated from meteorological data. In regions with sparse meteorological station coverage environmental proxies provide important additional data source for estimating past and current fire risk. Here, we use a 60-year record of daily flows (ML day−1 past a fixed-point river gauge) from two rivers (Franklin and Davey) in the remote Tasmanian Wilderness World Heritage Area (TWWHA) to characterize seasonal patterns in fire risk in temperate Eucalyptus forests and rainforests. We show that river flows are strongly related to landscape soil moisture estimates derived from down-scaled re-analysis of meteorological data available since 1990. To identify river flow thresholds where forests are likely to burn, we relate river flows to known forest fires that have occurred in the previously defined ecohydrological domains that surround the Franklin and Davey catchments. Our analysis shows that the fire season in the TWWHA is centered on February (70% of all years below the median river flow threshold), with shoulders on December-January and March. Since 1954, forest fire can occur in at least one month for all but four summers in the ecohydrological domain that includes the Franklin catchment, and since 1964 fire could occur in at least one month in every summer in the ecohydrological domain that includes the Davey catchment. Our analysis shows that managers can use river flows as a simple index that indicates landscape-scale forest fire risk in the TWWHA.

Indigenous land use and climate have shaped fire regimes in southeast Australia during the Holocene, although their relative influence remains unclear. The archaeologically attested mid-Holocene decline in land-use intensity on the Furneaux Group islands (FGI) relative to mainland Tasmanian and SE Australia presents a natural experiment to identify the roles of climate and anthropogenic land use. We reconstruct two key facets of regional fire regimes, biomass (vegetation) burned (BB) and recurrence rate of fire episodes (RRFE), by using total charcoal influx and charcoal peaks in palaeoecological records, respectively. Our results suggest climate-driven biomass accumulation and dryness-controlled BB across southeast Australia during the Holocene. Insights from the FGI suggest people elevated the recurrence rate of fire episodes through frequent cultural burning during the early Holocene and reduction in recurrent Indigenous cultural burning during the mid–late Holocene led to increases in BB. These results provide long-term evidence of the effectiveness of Indigenous cultural burning in reducing biomass burned and may be effective in stabilizing fire regimes in flammable landscapes in the future.

AirRater is a free smartphone app developed in 2015, supporting individuals to protect their health from environmental hazards. It does this by providing (i) location-specific and near real-time air quality, pollen and temperature information and (ii) personal symptom tracking functionality. This research sought to evaluate user perceptions of AirRater’s usability and effectiveness. We collected demographic data and completed semi-structured interviews with 42 AirRater users, identified emergent themes, and used two frameworks designed to understand and support behavior change—the Behavior Change Wheel (BCW) and the Protective Action Decision Model (PADM)—to interpret results. Of the 42 participants, almost half indicated that experiencing symptoms acted as a prompt for app use. Information provided by the app supported a majority of the 42 participants to make decisions and implement behaviors to protect their health irrespective of their location or context. The majority of participants also indicated that they shared information provided by the app with family, friends and/or colleagues. The evaluation also identified opportunities to improve the app. Several study limitations were identified, which impacts the generalizability of results beyond the populations studied. Despite these limitations, findings facilitated new insights into motivations for behavior change, and contribute to the existing literature investigating the potential for smartphone apps to support health protection from environmental hazards in a changing climate.

Summary Background Smoke from uncontrolled wildfires and deliberately set prescribed burns has the potential to produce substantial population exposure to fine particulate matter (PM2·5). We aimed to estimate historical health costs attributable to smoke-related PM2·5 from all landscape fires combined, and the relative contributions from wildfires and prescribed burns, in New South Wales, Australia. Methods We quantified PM2·5 from all landscape fire smoke (LFS) and estimated the attributable health burden and daily health costs between July 1, 2000, and June 30, 2020, for all of New South Wales and by smaller geographical regions. We combined these results with a spatial database of landscape fires to estimate the relative total and per hectare health costs attributable to PM2·5 from wildfire smoke (WFS) and prescribed burning smoke (PBS). Findings We estimated health costs of AU$ 2013 million (95% CI 718–3354; calculated with the 2018 value of the AU$). $1653 million (82·1%) of costs were attributable to WFS and $361 million (17·9%) to PBS. The per hectare health cost was of $105 for all LFS days ($104 for WFS and $477 for PBS). In sensitivity analyses, the per hectare costs associated with PBS was consistently higher than for WFS under a range of different scenarios. Interpretation WFS and PBS produce substantial health costs. Total health costs are higher for WFS, but per hectare costs are higher for PBS. This should be considered when assessing the trade-offs between prescribed burns and wildfires. Funding None.

Vegetation fires are an essential component of the Earth system but can also cause substantial economic losses, severe air pollution, human mortality and environmental damage. Contemporary fire regimes are increasingly impacted by human activities and climate change, but, owing to the complex fire–human–climate interactions and incomplete historical or long-term datasets, it is difficult to detect and project fire-regime trajectories. In this Review, we describe recent global and regional trends in fire activity and examine projections for fire regimes in the near future. Although there are large uncertainties, it is likely that the economic and environmental impacts of vegetation fires will worsen as a result of anthropogenic climate change. These effects will be particularly prominent in flammable forests in populated temperate zones, the sparsely inhabited flammable boreal zone and fire-sensitive tropical rainforests, and will contribute to greenhouse gas emissions. The impacts of increased fire activity can be mitigated through effective stewardship of fire regimes, which should be achieved through evidence-based fire management that incorporates indigenous and local knowledge, combined with planning and design of natural and urban landscapes. Increasing transdisciplinary research is needed to fully understand how Anthropocene fire regimes are changing and how humans must adapt.

Background In the southern hemisphere summer of 2019-2020, Australia experienced its most severe bushfire season on record. Smoke from fires affected 80% of the population, with large exceedances of the Australian National Air Quality Standard for particulate air pollution recorded in all major population centres during this period. We examined if emerging and innovative digital technology can assist extreme smoke-affected populations to reduce their exposure and protect their health. Methods AirRater is a free smartphone app that tracks air quality and user symptoms in near real-time. We distributed an online survey to over 13,000 app users to assess how they used this information during the 2019-20 bushfire season, and if the app was helpful in decision-making around reducing personal smoke exposure. Results We received responses from 1732 users (13.3%). Respondents reported that the app was highly useful, supporting informed decisions regarding daily activities during the smoke-affected period. Commonly reported activities supported by information provided through the app were staying inside (76%), rescheduling or planning outdoor activities (64%), changing locations to less affected areas (29%) and informing decisions on medication use (15%). Conclusions Smartphone apps enable users to reduce smoke exposure and protect their health by providing individual-level and location-specific data. Furthermore, digital technology such as AirRater provides the potential to provide insight into the community impacts of environmental hazards such as bushfire smoke. Key messages Smartphone apps enable users to reduce their smoke exposure and protect their health. These emerging technologies can help public health authorities to understand the community impact of environmental hazards.

Comprehensive fire surveillance will strengthen resilience and adaptation to climate change.

In the southern hemisphere summer of 2019&ndash, 20, Australia experienced its most severe bushfire season on record. Smoke from fires affected 80% of the population, with large and prolonged exceedances of the Australian National Air Quality Standard for fine particulate matter (PM2.5) recorded in all major population centers. We examined if AirRater, a free smartphone app that reports air quality and tracks user symptoms in near real-time, assisted those populations to reduce their smoke exposure and protect their health. We distributed an online survey to over 13,000 AirRater users to assess how they used this information during the 2019&ndash, 20 bushfire season, and why it was helpful to aid decision-making in reducing personal smoke exposure. We received responses from 1732 users (13.3%). Respondents reported the app was highly useful, supporting informed decision-making regarding daily activities during the smoke-affected period. Commonly reported activities supported by information provided through the app were staying inside (76%), rescheduling or planning outdoor activities (64%), changing locations to less affected areas (29%) and informing decisions on medication use (15%). Innovative and easy-to-use smartphone apps such as AirRater, that provide individual-level and location-specific data, can enable users to reduce their exposure to environmental hazards and therefore protect their health.

Over the Austral spring and summer of 2019/20 > 7 million ha of Eucalyptus forest and woodland, including some of Australia's most carbon dense ecosystems, were burnt on the east coast of Australia. We estimated bootstrapped mean CO2 emissions of c. 0.67 Pg, with other available estimates ranging from 0.55 to 0.85 Pg. Eucalyptus forests are renowned for their ability to resist and recover from wildfire so it would be expected that emitted CO2 will be reabsorbed. The combination of drought and frequent fires is likely reducing the capacity to recover from the fire so future Australian forests may store less carbon. Broadscale prescribed burning is a widely promoted approach to reduce uncontrolled wildfires, yet the benefits for the management of carbon stores are controversial. Prescribed burning can reduce carbon losses from subsequent wildfire, yet the "carbon costs" of it may equal or outweigh the "carbon benefits" in reduced wildfire emissions. Likewise, mechanical thinning of vegetation to reduce fuel loads also carries heavy carbon costs with uncertain carbon benefits. Research involving empirical measurements, modelling and a mix of large-scale management intervention is urgently required to determine what interventions can maximise carbon storage in the face of climate change-driven fires.

The boreal forests are one of the largest terrestrial carbon stores on Earth, much of which is contained in deep organic soils. The stores of aboveground and belowground biomass are periodically burned by wildfire, a natural disturbance in the boreal zone. Anthropogenic climate change is leading to larger and more severe fires, raising concerns that the boreal forest could become a carbon source rather than a sink. Quantifying and predicting boreal forest fire-driven carbon dynamics is a major research challenge, hampered by the complexity and spatio-temporal scale of the biogeochemical processes involved. Dieleman et al. (2020) used a natural experimental design to show that the legacy effects of past logging and fire disturbance have strongly contrasting effects on aboveground and belowground carbon losses associated with major wildfires that occurred in 2015 in southern boreal forests in central Saskatchewan, Canada. Their study design controlled for the effects of ecoregion, forest type and topo-edaphic gradients that all affect carbon. Based on these data they estimated the magnitude of carbon emissions from the 2015 fire season in Saskatchewan was 36.3 ± 15.0 Tg C. They drew an analogy with northern boreal forests, positing that in the future these forests may store significantly less carbon because frequent fires will impede forest growth and consume organic soil. Natural experiments, such as that undertaken by Dieleman et al. (2020), are constrained by numerous assumptions and contain statistical uncertainties blunting their capacity to accurately disclose the trajectory of complex ecological systems such as boreal carbon dynamics. Nonetheless, natural experiments are a critical element in Earth System science because they are important for framing questions, refining hypotheses and generating empirical data that can inform and ground in reality other approaches, such as mechanistic biogeochemical models, essential in predicting the fate of global carbon stores like those in the boreal forest.

The island state of Tasmania has marked seasonal variations of fine particulate matter (PM2.5) concentrations related to wood heating during winter, planned forest fires during autumn and spring, and bushfires during summer. Biomass smoke causes considerable health harms and associated costs. We estimated the historical health burden from PM2.5 attributable to wood heater smoke (WHS) and landscape fire smoke (LFS) in Tasmania between 2010 and 2019. We calculated the daily population level exposure to WHS- and LFS-related PM2.5 and estimated the number of cases and health costs due to premature mortality, cardiorespiratory hospital admissions, and asthma emergency department (ED) visits. We estimated 69 deaths, 86 hospital admissions, and 15 asthma ED visits, each year, with over 74% of impacts attributed to WHS. Average yearly costs associated with WHS were of AUD$ 293 million and AUD$ 16 million for LFS. The latter increased up to more than AUD$ 34 million during extreme bushfire seasons. This is the first study to quantify the health impacts attributable to biomass smoke for Tasmania. We estimated substantial impacts, which could be reduced through replacing heating technologies, improving fire management, and possibly implementing integrated strategies. This would most likely produce important and cost-effective health benefits.

Context Populations of native mammals are declining at an alarming rate in many parts of tropical northern Australia. Fire regimes are considered a contributing factor, but this hypothesis is difficult to test because of the ubiquity of fire. Aims This preliminary study investigated relative abundance and richness of small mammals on a gradient of fire regimes in the Uunguu Indigenous Protected Area (north Kimberley, Australia). Methods Species were sampled using 40 unbaited camera traps, positioned for a year on 20 transects crossing the rainforest–savanna boundary at locations with comparable environment and geology but varying fire history. The relative importance of the factors ‘fire frequency’, ‘late dry season fire frequency’, ‘time since burnt’ and ‘vegetation type’ as predictors of the number of small mammal species and detections was tested using Spatial Generalised Linear Mixed Models to account for spatial autocorrelation. Key results Nine species of small mammals were observed. Mammals were more abundant and diverse in locations with low overall fire frequency, which was a better predictor than late dry season fire frequency or time since burnt. The model including fire frequency and vegetation explained the highest proportion of total variation in mammal diversity (R2 = 42.0%), with most of this variation explained by fire frequency alone (R2 = 40.5%). The best model for number of detections (R2 = 20.9%) included both factors. Conclusions In the north Kimberley, small mammals are likely to be more abundant and diverse in areas with low fire frequency. Implications This natural experiment supports the theory that frequent fires are contributing to the decline of small mammals observed across northern Australia.

Summary Cupressaceae subfamily Callitroideae has been an important exemplar for vicariance biogeography, but its history is more than just disjunctions resulting from continental drift. We combine fossil and molecular data to better assess its extinction and, sometimes, rediversification after past global change.Key fossils were reassessed and their phylogenetic placement for calibration was determined using trait mapping and Bayes Factors. Five vicariance hypotheses were tested by comparing molecular divergence times with the timing of tectonic rifting. The role of adaptation to fire (serotiny) in its spread across a drying Australia was tested for Callitris.Our findings suggest that three transoceanic disjunctions within the Callitroideae probably arose from long‐distance dispersal. A signature of extinction, centred on the end‐Eocene global climatic chilling and drying, is evident in lineages‐through‐time plots and in the fossil record. Callitris, the most diverse extant callitroid genus, suffered extinctions but surviving lineages adapted and re‐radiated into dry, fire‐prone biomes that expanded in the Neogene. Serotiny, a key adaptation to fire, likely evolved in Callitris coincident with the biome shift.Both extinction and adaptive shifts have probably played major roles in this chronicle of turnover and renewal, but better understanding of biogeographical history requires improved taxonomy of fossils.