Changes In Fire Regimes Research Articles

Climate change, fire return intervals and the growing risk of permanent forest loss in boreal Eurasia

Climate change has driven an increase in the frequency and severity of fires in Eurasian boreal forests. A growing number of field studies have linked the change in fire regime to post-fire recruitment failure and permanent forest loss. In this study we used four burned area and two forest loss datasets to calculate the landscape-scale fire return interval (FRI) and associated risk of permanent forest loss. We then used machine learning to predict how the FRI will change under a high emissions scenario (SSP3–7.0) by the end of the century. We found that there are currently 133,000 km2 forest at high, or extreme, risk of fire-induced forest loss, with a further 3 M km2 at risk by the end of the century. This has the potential to degrade or destroy some of the largest remaining intact forests in the world, negatively impact the health and economic wellbeing of people living in the region, as well as accelerate global climate change.

Assessment of satellite orbit-drift artifacts in the long-term AVHRR FireCCILT11 global burned area data set

The recent 1982–2018 FireCCILT11 burned area (BA) product derived from NOAA AVHRR data is examined with regard to its suitability for long-term BA analyses. We focus on identifying NOAA AVHRR satellite orbit-drift artifacts within the FireCCILT11 BA time series since the occurrence of such artifacts can render any BA data set inappropriate for long-term analyses. We show that significant orbit-drift artifacts are present in the FireCCILT11 product over numerous large spatial patches located on every continent except Antarctica. In addition, the BA mapped by the FireCCILT11 in the United States is compared to independent ground-based records compiled by the National Interagency Fire Center. Prior to 2001, the FireCCILT11 product drastically overestimated BA within this region, to the point of falsely suggesting an abrupt radical change in fire regime at the turn of the century. Our findings indicate that caution is required when using the FireCCILT11 product for long-term BA studies, particularly within the tropics or the United States for the periods 1982–2000 and 2018. Studies requiring gridded BA data for these years, particularly at local and regional scales, should explicitly consider AVHRR orbit-drift artifacts that may result in FireCCILT11-reported BA that is substantially different (for example, several times greater) than the actual BA.

Predicting natural hyperdense regeneration after wildfires in Pinus halepensis (Mill.) forests using prefire site factors, forest structure and fire severity

Postfire Pinus halepensis (Aleppo pine) regeneration is often hyperdense. The overstocked stands created by this hyperdense regeneration considerably increase the risk of biotic and abiotic disturbances, especially fires, by increasing the potential for widespread forest losses. Our aim was to understand the relation between prefire site factors (climate, geographical position, topography, soil), prefire forest structure variables and fire severity with regeneration density after fire. We specifically wondered: (1) what are the general drivers of natural regeneration in these forests after fire?; (2) what are the necessary prefire conditions for establishing Aleppo pine hyperdense regenerations (>4,000 plants/ha)? To answer these questions, we sampled 147 plots in 15 wildfires located in the Comunitat Valenciana, which were representative of Aleppo pine Mediterranean forests. We used full and partial redundancy analyses (RDAs) for variance partitioning, and a decision tree analysis to look for the key site factors that drive regeneration density after fire. We found that all the site factors measured in the study explained 34.4 % of total variation in regeneration density. Prefire site factors and fire severity together explained 28.4 % of total variability, while the measured postfire factors explained only 7.5 %. Forest structure and climate explained 8.3 % and 6.7 % of variation, respectively. Five specific site factors drove regeneration density after fire: average minimum temperature, tree density before fire, resprouting shrubs coverage before fire, soil depth and bedrock type. The conclusions of this study were: (i) the average minimum temperature was the main significant variable that classified regeneration density and split data into three significant groups of Aleppo pine burned sites; (ii) the prefire forest structure (overstorey density and understorey coverage) controls regeneration density at colder burned sites, but soil depth and bedrock can be more important at warmer sites; (iii) fire severity relates positively to pine regeneration density, but negatively to resprouting vegetation coverage after fire; (iv) overstocked stands are not expected if prefire stand density is below 100 trees/ha at colder burned sites. These results may facilitate the planning of forest management and restoration actions because it may be used to identify those areas more likely to regenerate overstocked stands when faced with a changing fire regime.

Wildfire contribution to streamflow variability across Australian temperate zone

As wildfires become more frequent and severe, there are concerns regarding their impacts on water yield from forested catchments. While there are many studies in Australia about the effects of individual wildfires on streamflow at fine scales (<1 km2) in specific geographic settings, the effects of wildfire regimes on streamflow at broad spatial scales across temperate forests in Australia are not well understood. In this paper, we combined climate, wildfire, streamflow records (1975 to 2018), topographic, and landcover data from 92 catchments (74 – 4740 km2) in the Australian temperate zone to quantify the contribution of wildfire regimes over time to streamflow variability in different hydroclimatic settings (humid, dry sub-humid, and semi-arid) and geographic regions (Southeast Australia (SEA), Southwest Western Australia (SWWA), and Tasmania (TAS)). Wildfire regimes were represented by two metrics: the burnt area to drainage area (BDA) ratio for wildfire events in each year and a spatially averaged metric of Time Since Fire (TSF), which is a spatial average of time since the last wildfire in the catchment. By comparing prefire and postfire runoff ratios our study found that on average there was a short-term increase in runoff ratio (∼3% in year 1 and ∼6% in year 2 post-fire) after wildfires with BDA > 25%. No influence of fire was found in the long-term (15–20 years after the wildfire) runoff ratio. We found that wildfire regime, measured by TSF, explained ∼8.8% of the variation in annual streamflow across the Australian temperate zone, and that with decreasing TSF (i.e., increased wildfire impact), the average streamflow increased. Streamflow variation explained by wildfire regimes varied with hydroclimate. The explained variance of streamflow by wildfire regimes in semi-arid catchments (23%) and dry sub-humid catchments (13%) were higher than humid catchments (5%). Our results provide a broad-scale understanding of how wildfire regimes influence streamflow variability at broad temporal and spatial scales, and provided important context and baseline information for determining the implications of changes in climate and fire regimes for regional water availability.

The Reading Palaeofire Database: an expanded global resource to document changes in fire regimes from sedimentary charcoal records

Abstract. Sedimentary charcoal records are widely used to reconstruct regional changes in fire regimes through time in the geological past. Existing global compilations are not geographically comprehensive and do not provide consistent metadata for all sites. Furthermore, the age models provided for these records are not harmonised and many are based on older calibrations of the radiocarbon ages. These issues limit the use of existing compilations for research into past fire regimes. Here, we present an expanded database of charcoal records, accompanied by new age models based on recalibration of radiocarbon ages using IntCal20 and Bayesian age-modelling software. We document the structure and contents of the database, the construction of the age models, and the quality control measures applied. We also record the expansion of geographical coverage relative to previous charcoal compilations and the expansion of metadata that can be used to inform analyses. This first version of the Reading Palaeofire Database contains 1676 records (entities) from 1480 sites worldwide. The database (RPDv1b – Harrison et al., 2021) is available at https://doi.org/10.17864/1947.000345.

First Spatial Reconstruction of Past Fires in Temperate Europe Suggests Large Variability of Fire Sizes and an Important Role of Human-Related Ignitions

The spatial component of past forest fires in temperate Europe has been little studied, despite the value of such data in quantifying human and natural factors driving fire activity and associated forest dynamics. Changes in fire regimes reported across a range of ecosystems call for a better understanding of variability in historic fires and may help define reference points that can be relied upon when discussing climate change effects. We provide the first dendrochronological reconstruction of historical fire sizes in Central Europe and analyze the minimum extent of fires during the last four centuries in a 9.2 km2 (920 ha) conifer-dominated section of Białowieża Forest, one of the largest continuous lowland forests of the subcontinent. We recorded 82 fires between 1666 and 1946, using 275 sample trees, while 92% of fires (76 out of 82) spread beyond the studied area. Fires varied considerably in size, from events recorded at only one site (1–200 ha) to fires recorded in more than half of the studied area, thus exceeding 500 ha in size. The fire cycle was 11 years over the whole study period, with three distinct periods revealed by the regime shift analysis. In the years 1670–1750, the fire cycle averaged 12 years. It shortened to 7 years between 1755–1840 and increased to 22 years over the 1845–1955 period. In comparison with present day data, the reconstructed fire density of 3.2 fires per 100 km2 (10 000 ha) and year exceeded lightning ignition density by one to two orders of magnitude, suggesting a significant contribution of human-related ignitions. Our results highlight the important role of fire disturbance in Białowieża Forest and provide critical baseline information to design biological conservation strategies for European forests.

Increasing fire frequency and severity will increase habitat loss for a boreal forest indicator species.

Climate change will lead to more frequent and more severe fires in some areas of boreal forests, affecting the distribution and availability of late‐successional forest communities. These forest communities help to protect globally significant carbon reserves beneath permafrost layers and provide habitat for many animal species, including forest‐dwelling caribou. Many caribou populations are declining, yet the mechanisms by which changing fire regimes could affect caribou declines are poorly understood. We analyzed resource selection of 686 GPS‐collared female caribou from three ecotypes and 15 populations in a ~600,000 km2 region of northwest Canada and eastern Alaska. These populations span a wide gradient of fire frequency but experience low levels of human‐caused habitat disturbance. We used a mixed‐effects modeling framework to characterize caribou resource selection in response to burns at different seasons and spatiotemporal scales, and to test for functional responses in resource selection to burn availability. We also tested mechanisms driving observed selection patterns using burn severity and lichen cover data. Caribou avoided burns more strongly during winter relative to summer and at larger spatiotemporal scales relative to smaller scales. During the winter, caribou consistently avoided burns at both spatiotemporal scales as burn availability increased, indicating little evidence of a functional response. However, they decreased their avoidance of burns during summer as burn availability increased. Burn availability explained more variation in caribou selection for burns than ecotype. Within burns, caribou strongly avoided severely burned areas in winter, and this avoidance lasted nearly 30 years after a fire. Caribou within burns also selected higher cover of terrestrial lichen (an important caribou food source). We found a negative relationship between burn severity and lichen cover, confirming that caribou avoidance of burns was consistent with lower lichen abundance. Consistent winter avoidance of burns and severely burned areas suggests that caribou will experience increasing winter habitat loss as fire frequency and severity increase. Our results highlight the potential for climate‐induced alteration of natural disturbance regimes to affect boreal biodiversity through habitat loss. We suggest that management strategies prioritizing protection of core winter range habitat with lower burn probabilities would provide important climate‐change refugia for caribou.

Changing fire regimes during the first olive cultivation in the Mediterranean Basin: New high-resolution evidence from the Sea of Galilee, Israel

Throughout the Mediterranean biome, fire has been a dominant natural agent of change and an important tool for anthropogenic landscape modifications for millennia. However, fundamental knowledge on the complex linkages among fire, vegetation, and early agricultural practices remains limited. This research explores the role these processes have in shaping the landscape in the southern Levant – a key region with a long tradition of agriculture and horticulture. Olive horticulture is among the oldest and most widespread agricultural forms in the Mediterranean Basin. The earliest palynological evidence for olive horticulture is recorded in the Sea of Galilee in Israel and suggests that the first major olive cultivation began during the end of the 8th millennium BP. We present a multi-proxy dataset from the Sea of Galilee before and during the first olive cultivation (~7700–6680 a cal BP). Quantitative analyses of a charcoal time series categorized into distinct charcoal morphotypes indicate changes in fire regimes and sources of biomass burning. With a two-year-resolution, our study offers one of the highest resolution sedimentary charcoal records yet available worldwide. Isotopes from lake carbonates provide new evidence for the climatic setting of this phase, providing an independent evaluation of climatic impacts on vegetation and fire. Combined with palynological evidence, this multi-proxy dataset provides new insights into the linkages between fire, climate, fuel, and early horticultural practice. The fire regime changed with the start of olive cultivation in the Sea of Galilee's catchment. Fire frequency increased just before and during the expansion of olive cultivation, probably driven by the anthropogenic use of fire for clearing the landscape and promoting fertile soils. Once olive orchards were established, low magnitude fires became common, suggesting anthropogenic manipulation of the fire regime with frequent, low intensity, controlled burnings. Fuel limitation and low fuel connectivity likely played a role in both pre-cultivation and cultivation phases, resulting in low fire activity during times of reduced grass and woody vegetation cover. This study allows a new perspective into the temporal variability of middle-Holocene fire regimes in the Levant and an increased understanding of the dynamic role of fire during early horticulture practices. Our data also have relevance for future challenges that cultural legacies such as olive cultivation will face.

Fuel Loads and Plant Traits as Community‐Level Predictors of Emergent Properties of Vulnerability and Resilience to a Changing Fire Regime in Black Spruce Forests of Boreal Alaska

AbstractBlack spruce forest communities in boreal Alaska have undergone self‐replacement succession following low‐to‐moderate severity fires for thousands of years. However, recent intensification of interior Alaska's fire regime, particularly deeper burning of the soil organic layer, is leading to shifts to deciduous‐dominated successional pathways, resulting in many socioecological consequences. Both fuel load quantity and quality (or “burnability”) influence black spruce plant communities' potential to burn. Even relatively low fuel loads, such as those seen in black spruce forest understory, can be highly influential drivers of fire behavior due to their high flammability. Additionally, black spruce community self‐replacement following fire can be largely attributed to the suite of functional and life history traits possessed by the species dominating these communities. We used fuel load (quantity and quality) and amount of within‐population plant trait variation (coefficient of variation; CV) as community‐level emergent properties to investigate black spruce forest vulnerability and resilience to a changing fire regime across the landscape. Our burn severity potential index (BSPI), calculated from fuel load quantity and quality measurements, indicates that drier, higher elevation stands with thicker active layers were the most vulnerable to fire‐induced vegetation shifts under a changing fire regime. Forest resilience to fire‐induced vegetation shift, represented by higher CV, was negatively associated with BSPI and greatest in ecoregions dominated by lowland black spruce forests. Together, these analyses provide critical information for determining the likelihood of stand‐replacing shifts in dominant vegetation following fire and for implementing appropriate ecosystem management practices.

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Fire ecology for the 21st century: Conserving biodiversity in the age of megafire

Gaps in Monitoring Leave Northern Australian Mammal Fauna with Uncertain Futures

Northern Australian biomes hold high biodiversity values within largely intact vegetation complexes, yet many species of mammals, and some other taxa, are endangered. Recently, six mammal species were added to the 20 or so already listed in the Australian endangered category. Current predictions suggest that nine species of mammal in northern Australia are in imminent danger of extinction within 20 years. We examine the robustness of the assumptions of status and trends in light of the low levels of monitoring of species and ecosystems across northern Australia, including monitoring the effects of management actions. The causes of the declines include a warming climate, pest species, changed fire regimes, grazing by introduced herbivores, and diseases, and work to help species and ecosystems recover is being conducted across the region. Indigenous custodians who work on the land have the potential and capacity to provide a significant human resource to tackle the challenge of species recovery. By working with non-Indigenous researchers and conservation managers, and with adequate support and incentives, many improvements in species’ downward trajectories could be made. We propose a strategy to establish a network of monitoring sites based on a pragmatic approach by prioritizing particular bioregions. The policies that determine research and monitoring investment need to be re-set and new and modified approaches need to be implemented urgently. The funding needs to be returned to levels that are adequate for the task. At present resourcing levels, species are likely to become extinct through an avoidable attrition process.

Mortality and resprouting responses in forest trees driven more by tree and ecosystem characteristics than drought severity and fire frequency

Increases in tree mortality linked to drought and fires have been reported across a range of forests globally over the last few decades. Forests that resprout epicormically/aerially should be the most resistant and resilient to changes in fire regime, yet they may be at risk of increased mortality, demographic shifts and changes to species composition due to the compounding effects of drought and fire. Despite this, the synergistic effects of drought and fire frequency on resprouters has received less attention than for obligate seeder tree species. Our study examined the effects of drought severity and fire frequency on the fire resistance of eucalypts (i.e., including Eucalyptus, Angophora and Corymbia) that can resprout epicormically. Following large-scale wildfires and drought in 2013, we conducted field surveys of temperate eucalypt forests in the Sydney Basin Bioregion, focusing on two major Eucalyptus forest assemblages: dry ridgetops and wet gullies. We measured tree size, previous fire damage (i.e., fire scars), bark type, mortality and resprouting position (e.g., canopy, stem, base) of reproductive-age trees. We used a Bayesian modelling approach to derive bounded estimates of response probabilities for trees sampled in each combination of drought severity (mild/moderate versus severe) and fire frequency (low versus high), as well as bounded estimates of differences between trees with and without fire scars, different bark types and drought/fire histories. Eucalypt populations in both vegetation types were resilient to increases in mortality and changes in resprouting position under severe drought and frequent fire, and mortality and resprouting position varied substantially with tree size, fire scar presence/absence and among bark types. Tree mortality and changes in resprouting position were considerably more likely in smaller trees with fire scars. Species with non-compact bark (e.g., fibrous, stringy, rough) were less resilient to lowering in resprouting position, e.g., from canopy to stem. Populations dominated by species that have small stem diameters, thin/non-compact bark and previous fire damage are likely at elevated risk of mortality and changes in resprouting position under future climate change.

Spatio-Temporal Patterns of Joshua Tree Stand Structure and Regeneration Following Mojave Desert Wildfires

Eastern Joshua tree (Yucca jaegeriana) plays a central role in the ecology of the Mojave Desert ecosystem. However, the emergence of invasive grass fire-cycles in the last several decades brings into question Joshua trees’ tolerance and resilience to changing fire regimes. This study’s objective was to examine the effects of wildfires on the structure and regeneration potential of Joshua trees forests. We examined the density, size class structure, and regeneration response of Joshua tree populations on a network of one kilometer transects along the boundaries of four independent wildfires and the interior of the largest fire that occurred 15 years ago (2005) in the northeast Mojave Desert. Burned edge and burned interior transects had 23- and 4.1-fold lower Joshua tree stand densities than unburned transects. The more robust recovery of stand density along burned interior transects compared to burned edge transects appears to be primarily driven by more prolific vegetative sprouting. Our data show that Joshua trees can sprout vegetatively following fire, but it is not a strong or consistent post-fire resprouter. Limiting the spread of invasive annual grasses and novel fire regimes will be critical to maintaining healthy Joshua tree populations into the future, particularly on the edge of its ecological range.

Evidence that modern fires may be unprecedented during the last 3400 years in permafrost zone of Central Siberia, Russia

Recent climate change in Siberia is increasing the probability of dangerous forest fires. The development of effective measures to mitigate and prevent fires is impossible without an understanding of long-term fire dynamics. This paper presents the first multi-site palaeo-fire reconstruction based on macroscopic charcoal data from peat and lake sediment cores located in different landscapes across the permafrost area of central Siberia. The obtained results show similar temporal patterns of charcoal accumulation rates in the cores under study, and near synchronous changes in fire regimes. The paleo-fire record revealed moderate biomass burning between 3.4 and 2.6 ka BP, followed by the period of lower burning occurring from 2.6 to 1.7 ka BP that coincided with regional climate cooling and moistening. Minimal fire activity was also observed during the Little Ice Age (0.7–0.25 ka BP). Fire frequencies increased during the interval from 1.7 to 0.7 ka BP and appears to be partly synchronous with climate warming during the Medieval Climate Anomaly. Regional reconstructions of long-term fire history show that recent fires are unprecedented during the late Holocene, with modern high biomass burning lying outside millennial and centennial variability of the last 3400 years.

Limitations to Propagule Dispersal Will Constrain Postfire Recovery of Plants and Fungi in Western Coniferous Forests

AbstractMany forest species are adapted to long-interval, high-severity fires, but the intervals between severe fires are decreasing with changes in climate, land use, and biological invasions. Although the effects of changing fire regimes on some important recovery processes have previously been considered, the consequences for the dispersal of propagules (plant seeds and fungal spores) in forest communities have not. We characterize three mechanisms by which changing fire regimes disrupt propagule dispersal in mesic temperate, boreal, and high-elevation forests: reduced abundance and altered spatial distributions of propagule source populations, less effective dispersal of propagules by wind, and altered behavior of animal dispersers and propagule predators. We consider how disruptions to propagule dispersal may interact with other factors that are also influenced by fire regime change, potentially increasing risk of forest conversion. Finally, we highlight urgent research topics regarding how dispersal limitation may shape twenty-first century forest recovery after stand-replacing fire.

Environmental Factors Driving Seed Hydration Status of Soil Seed Banks and the Implications for Post-fire Recruitment.

Changes in fire regimes due to climate change and fire management practices are affecting the timing, length, and distribution of vegetation fires throughout the year. Plant species responses and tolerances to fire differ from season to season and are influenced by species-specific phenological processes. The ability of seeds to tolerate extreme temperatures associated with fire is one of these processes, with survival linked to seed moisture content at the time of exposure. As fire is more often occurring outside historic dry fire seasons, the probability of fire occurring when seeds are hydrated may also be increasing. In this study, we set out to understand the seasonal dynamics of seed hydration for seeds of Banksia woodland species, and how certain seed traits interact with environmental conditions to influence survival of high temperatures associated with fire. We measured the moisture content of seeds buried to 2 cm in the soil seed bank for four common native species and one invasive species on a weekly basis throughout 2017, along with soil moisture content and environmental correlates. We determined water sorption isotherms at 20°C for seeds of each species and used these functions to model weekly variation in seed water activity and predict when seeds are most sensitive to soil heating. Using Generalised additive models (GAMs), we were able to describe approximately 67% of the weekly variance in seed water activity and explored differences in seed hydration dynamics between species. Seed water activity was sufficiently high (i.e., ≥ 0.85 aw) so as to have created an increased risk of mortality if a fire had occurred during an almost continuous period between May and November in the study period (i.e., 2017). There were brief windows when seeds may have been in a dry state during early winter and late spring, and also when they may have been in a wet state during summer and late autumn. These data, and the associated analyses, provide an opportunity to develop approaches to minimize seed mortality during fire and maximize the seed bank response.

The effect of changes in human drivers on the fire regimes of South African grassland and savanna environments over the past 100 years

Fire is a key regulator of tree cover in grassy ecosystems, but century-long changes in fire regimes have not been explicitly quantified in South Africa. This study aimed to determine changes in the fire regimes of South Africa’s grassy biomes over the past century in response to widespread human-induced changes. Using spatially explicit data, we employed random forest models to examine the importance of climatic and human drivers on the extent, frequency and intensity of fire. We then modelled how fire regimes are likely to have changed over the past century using historical trends in key human drivers (population growth, livestock density, road density and land cover change) as inputs. Results showed that human drivers, particularly land transformation and human population density, were important determinants of fire regime. Random forest predictions showed a decline in burnt area (mean of 10.5% in 1910 to 5.1% in 2020), and a shift to fire regimes with smaller burnt areas, longer fire return intervals and lower intensity fires over the past century, particularly in the mesic east. These dynamics have important implications for our understanding of the widespread increases in woody cover observed in the region over this period.

Disentangling the factors of spatio-temporal patterns of wildfire activity in south-eastern France

Background Identifying if and how climatic and non-climatic factors drive local changes in fire regimes is, as in many other human-dominated landscapes, challenging in south-eastern France where both heterogeneous spatial patterns and complex fire trends are observed. Aim We sought to identify the factors driving the spatial-temporal patterns of fire activity in southeastern France. Methods We incorporated several non-climatic variables into the probabilistic Firelihood model of fire activity and implemented an enhanced spatio-temporal component to quantitatively assess remaining unexplained variations in fire activity. Key results Several non-climatic drivers (i.e. orography, land cover and human activities) contributed as much as fire-weather to the distribution of fire occurrence (&gt;1 ha) but less to larger fires (&gt;10, 100 and 1000 ha). Over the past decades, increased fire-weather induced a strong increase in wildfire probabilities, which was actually observed on the western part of the region but not so in the east and Corsican Island, most likely due to reinforced suppression policies. Conclusions While spatial patterns in fire activity are driven by land-use and land-cover factors, temporal patterns were mostly driven by changes in fire-weather and unexplained effects potentially related to suppression policies but with large differences between regions.

Restoration sites on the Californian coast have different ecological histories that can influence restoration success

For each restoration project, it is essential to define a reference ecosystem towards which ecological restoration aims. Historical information may be useful in the construction of the reference model and in finding out about the type and degree of disturbances that have caused degradation on the site, as legacies of past human land-uses have been shown to be major determinants of vegetation and plant diversity even in the very long term. The aim of this paper is the retrace the history of three sites where restoration protocols were tested, to better apprehend the potential reference ecosystems as well as the disturbances that degraded them. To do so, we first compiled information on the reference ecosystems at the landscape scale. Then, we compiled historical and agricultural information at the scale of the sites from local historical documents, historical reviews and aerial photographs. The three sites most likely were grasslands or oak savannas before European settlement. Grasslands used to cover 8.9 million ha in California. They were species-rich grasslands managed with fire by the native people and grazed by native ungulates. Early settlers introduced cattle grazing and changed fire regimes. Later on, many grasslands were converted to cultivation. All three sites were used for ranching and sometimes overgrazed. At least two of them were cultivated, probably leading to restoration being harder there, as plowing eliminates perennial species, destroys the seedbank, changes soil characteristics.

Frameworks for identifying priority plants and ecosystems most impacted by major fires

Globally, many species and ecosystems are experiencing landscape-scale wildfires (‘megafires’) and these events are predicted to increase in frequency and severity as the climate warms. Consequently, the capability to rapidly assess the likely impacts of such large fires and identify potential risks they pose to the persistence of species and ecosystems is vital for effective conservation management. In this review, we propose novel frameworks to identify which plant species and ecosystems are most in need of management actions as a result of megafires. We do this by assessing the impacts of a fire event on plants and ecosystems in the context of the whole fire regime (current fire event combined with recent fire history) and its interactions with other threatening processes, rather than simply considering the amount of habitat burnt. The frameworks are based on a combination of key species’ traits related to mechanisms of decline, components of the fire regime that are most likely to have adverse impacts on species or ecosystem recovery, and biotic and environmental factors that may amplify fire impacts or pose barriers to post-fire recovery. We applied these frameworks to guide management priorities and responses following the extensive 2019/2020 fires in southern Australia, and we illustrate their application here via a series of worked examples that highlight the various mechanisms of post-fire decline the frameworks address. The frameworks should be applicable to a broader range of fire-prone biomes worldwide. Our approach will (1) promote the development of foundational national datasets for assessing megafire impacts on biodiversity, (2) identify targeted priority actions for conservation, (3) inform planning for future fires (both prescribed burning and wildfire suppression), and (4) build awareness and understanding of the potential breadth of factors that threaten plants and ecosystems under changing fire regimes.