Extent Of Wildfires Research Articles

No deceleration signs in the permafrost ground subsidence four years after the 2019 fire in Northwest Territories, Canada

Abstract The circum-arctic permafrost environment is often disturbed by wildfires but could also show resilience to these disturbances. However, the increased frequency and extent of wildfires, coupled with unprecedented hot weather, have introduced greater uncertainties in the post-fire permafrost dynamics. We need to address emerging questions, e.g., How will permafrost respond to the joint effect of hot anomalies and wildfires? To what extent will post-wildfire deformation evolve? How will permafrost resilience to wildfires vary? Utilizing Interferometric Synthetic Aperture Radar (InSAR) time series analysis, we investigated the post-wildfire ground deformation around a 2019 fire scar in the lower Mackenzie Valley, Northwest Territories, Canada, where dramatic heat anomalies and severe wildfires have been recorded in recent years. The resilience of permafrost to wildfires appears to be weakened by the continuous and rapid warming after the fire, as evidenced by the year-on-year acceleration in subsidence rates. Such acceleration was never reported by previous findings that typically observed deceleration in subsidence rates four to five years after wildfires. The deformation along the line of sight (LOS) of the satellite demonstrates significant permafrost degradation induced by wildfires and exacerbated by climate warming, and the cumulative subsidence was detected up to 25 cm in the LOS direction in the upland areas and up to 10 cm in the lowland areas four years after the fire. The difference in deformation magnitude could be attributed to local factors, including ground ice, topography, and vegetation. Our study highlights the increasingly severe threat to circum-arctic permafrost due to the combined effects of wildfires and extreme heat anomalies.

Stakeholders’ participation in decreasing wildfire risk in the context of natural resource management in the Podpoľanie region of Slovakia

Key MessageAs the number and extent of wildfires are increasing due to climate change and human impacts, the demand for effective risk reduction strategies is growing. Due to limited resources or management capabilities in Slovakia, appropriate multistakeholder participation could help decrease the risk of wildfires while continuing to implement the principles of sustainable forest management. Thus, we recommend improving relationships with responsible stakeholders and increasing their knowledge.ContextAlthough the frequency of wildfires has declined in Slovakia, the total burned area per year and the average burned area per fire have increased rapidly, mainly due to traditional land management and increasing numbers of natural disasters resulting from climate change.AimThe objective of this study is to assess the participation and management of stakeholders in the region of Podpoľanie, which is the region of Slovakia that is most prone to wildfires. In particular, this study investigates the questions of who is accountable, in what networks, and with regard to what issues with the goal of enhancing efforts to combat wildfires.MethodsThis single-country case study features an exploratory sequential mixed-methods design. While stakeholders’ participation was explored via face-to-face interviews and interest-influence matrices, stakeholders’ prioritization was assessed via an online survey and the quantitative mapping of stakeholders’ involvement, power, interest, and knowledge.ResultsWe separately identified primary stakeholders (e.g., fire departments and state-owned forest enterprises) and secondary stakeholders (e.g., municipalities and community members). Tasks related to efforts to combat wildfires were largely in compliance with legal regulations and other mandates. Nonetheless, some stakeholders (e.g., governmental organizations involved in nature protection or nonstate forest owners and the associated enterprises) lacked the knowledge, experience, or responsibility necessary to perform these tasks.ConclusionThese stakeholders should be informed and monitored closely to achieve outcomes that can benefit a variety of stakeholders. We recommend a plan that involves improving the relationships among primary and secondary stakeholders, increasing their knowledge, and promoting effective participation to decrease the risk of wildfires in the region.

Estimated Impacts of Prescribed Fires on Air Quality and Premature Deaths in Georgia and Surrounding Areas in the US, 2015-2020.

Smoke from wildfires poses a substantial threat to health in communities near and far. To mitigate the extent and potential damage of wildfires, prescribed burning techniques are commonly employed as land management tools; however, they introduce their own smoke-related risks. This study investigates the impact of prescribed fires on daily average PM2.5 and maximum daily 8-h averaged O3 (MDA8-O3) concentrations and estimates premature deaths associated with short-term exposure to prescribed fire PM2.5 and MDA8-O3 in Georgia and surrounding areas of the Southeastern US from 2015 to 2020. Our findings indicate that over the study domain, prescribed fire contributes to average daily PM2.5 by 0.94 ± 1.45 μg/m3 (mean ± standard deviation), accounting for 14.0% of year-round ambient PM2.5. Higher average daily contributions were predicted during the extensive burning season (January-April): 1.43 ± 1.97 μg/m3 (20.0% of ambient PM2.5). Additionally, prescribed burning is also responsible for an annual average increase of 0.36 ± 0.61 ppb in MDA8-O3 (approximately 0.8% of ambient MDA8-O3) and 1.3% (0.62 ± 0.88 ppb) during the extensive burning season. We estimate that short-term exposure to prescribed fire PM2.5 and MDA8-O3 could have caused 2665 (95% confidence interval (CI): 2249-3080) and 233 (95% CI: 148-317) excess deaths, respectively. These results suggest that smoke from prescribed burns increases the mortality. However, refraining from such burns may escalate the risk of wildfires; therefore, the trade-offs between the health impacts of wildfires and prescribed fires, including morbidity, need to be taken into consideration in future studies.

Mitigation of disease and browsing impacts, and translocation, supports post-fire threatened flora recovery

Context For plant species that have evolved in fire-prone environments, declines after wildfires are often driven by the combination of fire and other threatening processes. Mitigating the impacts of these threatening processes can sometimes effectively support post-fire population recovery. Aims We test the effectiveness of: (1) phosphite application to mitigate Phytophthora dieback; (2) fencing to exclude browsing by mammalian herbivores; and (3) translocation to sites where threats can be practically managed, for conservation of threatened flora affected by wildfires in 2018 and 2019 in the Stirling Range (Koi Kyeunu-ruff), south-western Australia. Methods Survival of Phytophthora-susceptible flora was compared in repeatedly sampled plots from prior to and after wildfire and ± recurrent phosphite application. Survival and growth of browsing-susceptible flora was compared post-fire in fenced and control plots. Survival, growth and flowering was compared between wild populations recruiting after wildfire and translocated populations. Key results Phosphite application increased survival of most Phytophthora-susceptible flora. Fencing led to greater growth and often increased survival. Translocated populations, with supplemental water, had greater growth rates and earlier flowering than wild populations, and a non-significant trend for higher survival. Conclusions These findings provide strong evidence supporting continuation of phosphite application, herbivore exclusion and translocation for post-fire recovery of the threatened flora of the Stirling Range. Implications With increasing wildfire extent, frequency and impact across the globe, successful management of non-fire threats will be crucial for post-fire conservation of threatened flora, with the approaches proving effective in this study likely to have conservation value elsewhere.

Short-Interval, High-Severity Wildfire Depletes Diversity of Both Extant Vegetation and Soil Seed Banks in Fire-Tolerant Eucalypt Forests

Many plant species are well-adapted to historical fire regimes. An increase in the severity, frequency, and extent of wildfires could compromise the regenerative capacity of species, resulting in permanent shifts in plant diversity. We surveyed extant vegetation and soil seed banks across two forest types with contrasting historical fire regimes—Shrubby Dry Forest (fire return interval: 10–20 years) and Sub-Alpine Woodland (50–100 years). Over the past 20 years, both forests have been subject to repeated, high-severity wildfires at intervals significantly shorter than their historical return intervals. We examined the soil seed bank response to fire-cued germination, and whether the plant diversity in soil seed banks and extant vegetation demonstrated similar responses to short-interval, high-severity wildfires. The soil seed bank demonstrated a positive response to heat in combination with smoke, and for the Sub-Alpine Woodland, this was limited to sites more frequently burnt by fire. With an increase in fire frequency, there was a decline in species richness and Shannon’s Diversity and a shift in species composition in both extant vegetation and the soil seed bank. The fire frequency effects on the relative richness of trait associations were restricted to the Shrubby Dry Forest, and included an increase in short-lived obligate seeders, wind-dispersed species, and ant-dispersed shrubs in burnt relative to long unburnt sites in both extant vegetation and the soil seed bank. Graminoids were the most abundant component of the soil seed banks of Sub-Alpine Woodlands, and this increased with more frequent fire, with a similar trend (p = 0.06) in extant vegetation. Clear shifts in plant diversity in both soil seed banks and extant vegetation in forest types with contrasting historical fire regimes suggest that emerging fire regimes are pushing ecosystems beyond their historical range of variability, including potentially more flammable states and a decline in the buffering capacity of soil seed banks.

Opportunities and challenges for precipitation forcing data in post‐wildfire hydrologic modeling applications

AbstractThe frequency and extent of wildfires have increased in recent decades with immediate and cascading effects on water availability in many regions of the world. Precipitation is used as primary input to hydrologic models and is a critical driver of post‐wildfire hydrologic hazards including debris flows, flash floods, water‐quality effects, and reservoir sedimentation. These models are valuable tools for understanding the hydrologic response to wildfire but require accurate precipitation data at suitable spatial and temporal resolutions. Wildfires often occur in data‐sparse, headwater catchments in complex terrain, and post‐wildfire hydrologic effects are particularly sensitive to high‐intensity, short‐duration precipitation events, which are highly variable and difficult to measure or estimate. Therefore, the assessment and prediction of wildfire‐induced changes to watershed hydrology, including the associated effects on ecosystems and communities, are complicated by uncertainty in precipitation data. When direct measurements of precipitation are not available, datasets of indirect measurements or estimates are often used. Choosing the most appropriate precipitation dataset can be difficult as different datasets have unique trade‐offs in terms of spatial and temporal accuracy, resolution, and completeness. Here, we outline the challenges and opportunities associated with different precipitation datasets as they apply to post‐wildfire hydrologic models and modeling objectives. We highlight the need for expanded precipitation gage deployment in wildfire‐prone areas and discuss potential opportunities for future research and the integration of precipitation data from disparate sources into a common hydrologic modeling framework.This article is categorized under: Science of Water > Hydrological Processes Science of Water > Methods Science of Water > Water and Environmental Change

Prescribed fire placement matters more than increasing frequency and extent in a simulated Pacific Northwest landscape

AbstractPrescribed fire has been increasingly promoted to reduce wildfire risk and restore fire‐adapted ecosystems. Yet, the complexities of forest ecosystem dynamics in response to disturbances, climate change, and drought stress, combined with myriad social and policy barriers, have inhibited widespread implementation. Using the forest succession model LANDIS‐II, we investigated the likely impacts of increasing prescribed fire frequency and extent on wildfire severity and forest carbon storage at local and landscape scales. Specifically, we ask how much prescribed fire is required to maintain carbon storage and reduce the severity and extent of wildfires under divergent climate change scenarios? We simulated four prescribed fire scenarios (no prescribed fire, business‐as‐usual, moderate increase, and large increase) in the Siskiyou Mountains of northwest California and southwest Oregon. At the local site scale, prescribed fires lowered the severity of projected wildfires and maintained approximately the same level of ecosystem carbon storage when reapplied at a ~15‐year return interval for 50‐year simulations. Increased frequency and extent of prescribed fire decreased the likelihood of aboveground carbon combustion during wildfire events. However, at the landscape scale, prescribed fire did not decrease the projected severity and extent of wildfire, even when large increases (up to 10× the current levels) of prescribed fire were simulated. Prescribed fire was most effective at reducing wildfire severity under a climate change scenario with increased temperature and precipitation and on sites with north‐facing aspects and slopes greater than 30°. Our findings suggest that placement matters more than frequency and extent to estimate the effects of prescribed fire, and that prescribed fire alone would not be sufficient to reduce the risk of wildfire and promote carbon sequestration at regional scales in the Siskiyou Mountains. To improve feasibility, we propose targeting areas of high concern or value to decrease the risk of high‐severity fire and contribute to meeting climate mitigation and adaptation goals. Our results support strategic and targeted landscape prioritization of fire treatments to reduce wildfire severity and increase the pace and scale of forest restoration in areas of social and ecological importance, highlighting the challenges of using prescribed fire to lower wildfire risk.

Spatial and temporal monitoring of wildfires in Golestan province using remote sensing data

Wildfires are one of the most significant factors of ecosystem change. Knowing the wildfire regime (frequency, intensity, and distribution pattern) is essential in wildfire management. This research aims to analyze the spatiotemporal pattern of wildfires in Golestan in 2001-2021 using MODIS data, burned area product (MCD64A1). For this purpose, the annual and monthly frequency, as well as the trend of wildfires based on types of forest, pasture, and crop cover, were statistically analyzed. The local Moran pattern analysis method and kernel density function were used to analyze the spatial dynamics of wildfire. The results showed that 18,462 wildfires occurred in Golestan, the highest of which was in 2010, with 2,517 wildfires (13.8%). The lowest number of wildfires, with only 57 events (0.5%), was in 2001. Based on the local Moran model results and the kernel density function, the wildfires' extent and intensity were greater in the plains and foothills to the south and southeast of Golestan. The lowest extent and intensity of the wildfire corresponded to the eastern parts of the province. The frequency of wildfires was higher in the hot period of the year (spring and summer). However, the period of occurrence of wildfire and the peak of wildfire changes in different uses. The wildfire zones in June were wider and more intense than in other months. The frequency and spatial extent of wildfires in agricultural lands from May to July, pasture lands in July, August, and September, and forest lands in November and December were more than in other months. Weather conditions play a significant role in the occurrence of wildfire in the forest lands of Golestan. The results of this research help understand wildfire risk areas and provide a scientific basis for predicting and controlling wildfires and reducing carbon emissions related to them.

Delineating wildfire burns and regrowth using satellite imagery to assess moose (Alces alces) spatial responses to burns

AbstractClimate change is predicted to increase the frequency and size of wildfires. Wildfire burns can influence wildlife space use, but prior to understanding the relationship between wildlife and burns, the extent of wildfires and the regrowth of burned areas must be determined. We used remotely sensed, multispectral satellite imagery to calculate differenced normalized burn ratios (NBRs) to define areas burned by wildfire and assess temporal trends in burn frequency and extent in central British Columbia. We then used NBRs as an index of vegetation regrowth to model regrowth trajectories within burns. Next, we examined spatial responses to burns by a moose (Alces alces) population that recently declined in abundance. We utilized locations used by and available to collared moose to determine spatial responses as a function of years since wildfire and vegetation regrowth. We also assessed functional responses to burns by moose, dependent upon the proportion of burned areas available to each individual. We hypothesized that (h1) wildfire burns within our study area increased from 1985 to 2017, (h2) that moose increase their use of burns in comparison with availability as burns age as a result of vegetation regrowth, and (h3) that moose demonstrate functional responses to burns (i.e., selection of burns by individual moose declines as the amount of burned areas increases). We observed that the frequency and extent of burns are increasing within our study area. In contrast to h2, moose in summer and fall decreased the selection of burns as burns aged. We, however, observed that moose responded most positively to locations with intermediate vegetation regrowth (i.e., NBR values), which according to burn regrowth trajectories were most likely to be achieved 13 or more years post‐wildfire; given that most burns within our study area were ≤13 years of age, we predict that the use of burns will likely increase as vegetation regrows. Moose only selected for burns in fall, and we did not find support for the presence of a functional response. Our research demonstrated the utility of remotely sensed imagery and NBRs to define burn locations and to reveal current and probable future spatial responses to burns by a wildlife population of concern.

Interdependencies Between Wildfire‐Induced Alterations in Soil Properties, Near‐Surface Processes, and Geohazards

AbstractThe frequency, severity, and spatial extent of destructive wildfires have increased in several regions globally over the past decades. While direct impacts from wildfires are devastating, the hazardous legacy of wildfires affects nearby communities long after the flames have been extinguished. Post‐wildfire soil conditions control the persistence, severity, and timing of cascading geohazards in burned landscapes. The interplay and feedback between geohazards and wildfire‐induced changes to soil properties, land cover conditions, and near‐surface and surface processes are still poorly understood. Here, we synthesize wildfire‐induced processes that can affect the critical attributes of burned soils and their conditioning of subsequent geohazards. More specifically, we discuss the state of knowledge pertaining to changes in mineralogical, hydraulic, mechanical, and thermal properties of soil due to wildfire with a focus on advances in the past decade. We identify how these changes in soil properties alter evapotranspiration, interception, sediment transport, infiltration, and runoff. We then link these alterations to the evolution of different geohazards, including dry raveling, erosion, rockfalls, landslides, debris flows, and land subsidence. Finally, we identify research gaps and future directions to advance knowledge on how wildfires control the evolution of various earth surface processes and geohazards over time.

Trout and invertebrate assemblages in stream pools through wildfire and drought

Abstract Climate change is increasing the frequency, severity, and extent of wildfires and drought in many parts of the world, with numerous repercussions for the physical, chemical, and biological characteristics of streams. However, information on how these perturbations affect top predators and their impacts on lower trophic levels in streams is limited. The top aquatic predator in southern California streams is native Oncorhynchus mykiss, the endangered southern California steelhead trout (trout). To examine relationships among the distribution of trout, environmental factors, and stream invertebrate resources and assemblages, we sampled pools in 25 stream reaches that differed in the presence (nine reaches) or absence (16 reaches) of trout over 12 years, including eight reaches where trout were extirpated during the study period by drought or post‐fire flood disturbances. Trout were present in deep pools with high water and habitat quality. Invertebrate communities in trout pools were dominated by a variety of medium‐sized collector–gatherer and shredder invertebrate taxa with non‐seasonal life cycles, whereas tadpoles and large, predatory invertebrates (Odonata, Coleoptera, Hemiptera [OCH]), often with atmospheric breather traits, were more abundant in troutless than trout pools. Structural equation modelling of the algal‐based food web indicated a trophic cascade from trout to predatory invertebrates to collector–gatherer taxa and weaker direct negative trout effects on grazers; however, both grazers and collector–gatherers also were positively related to macroalgal biomass. Structural equation modelling also suggested that bottom‐up interactions and abiotic factors drove the detritus‐based food web, with shredder abundance being positively related to leaf litter (coarse particulate organic matter) levels, which, in turn, were positively related to canopy cover and negatively related to flow. These results emphasise the context dependency of trout effects on prey communities and of the relative importance of top‐down versus bottom‐up interactions on food webs, contingent on environmental conditions (flow, light, nutrients, disturbances) and the abundances and traits of component taxa. Invertebrate assemblage structure changed from a trout to a troutless configuration within a year or two after trout were lost owing to post‐fire scouring flows or drought. Increases in OCH abundance after trout were lost were much more variable after drought than after fire. The reappearance of trout in one stream resulted in quick, severe reductions in OCH abundance. These results indicate that climate‐change induced disturbances can result in the extirpation of a top predator, with cascading repercussions for stream communities and food webs. This study also emphasises the importance of preserving or restoring refuge habitats, such as deep, shaded, perennial, cool stream pools with high habitat and water quality, to prevent the extirpation of sensitive species and preserve native biodiversity during a time of climate change.

Movement response of small mammals to burn severity reveals importance of microhabitat features

Abstract Disturbance events are increasing at a global scale, with cascading impacts to ecosystems and residents therein that include fragmentation and altered vegetation structure and composition. Such changes may disproportionately impact small mammal movements, risk perception, and community dynamics as smaller species perceive such changes at finer spatial scales. We examined movement response to burn severity, vegetation structure, and composition in Mexican woodrats (Neotoma mexicana), a common but understudied small mammal species. The study was conducted on Mt. Graham in southeastern Arizona, United States, following a fire that burned over 19,400 ha. We measured path tortuosity of woodrats translocated over patches of different burn severity. Tortuosity can indicate microhabitat selection, foraging behavior, and perceived predation risk—features affecting population-level processes that changes in community composition alone cannot fully demonstrate. We captured woodrats, released them 50 m away from their midden, and used fluorescent powder to track woodrat movement paths through areas of low–severe burn severity. We analyzed features of the resulting powder trails including straightness, average step length, fractal dimension, and squared displacement. We also compared used versus expected vegetation structure and composition along movement paths across burn severities. Analyses indicated shorter step length with increased bare ground, as well as higher squared displacement in areas with more logs. Vegetation analyses likewise showed that logs were heavily used in low-burned areas, whereas dense vegetation was avoided in highly burned areas. Burn severity alone did not have a direct effect on movement parameters, rather its influence on vegetative composition and structure appears to be most important. Selection for logs and avoidance of dense vegetation may be attributed to auditory concealment and ease of travel. With projected increases in wildfire extent and severity, this work represents an understudied approach to understanding these disturbances and their effects on ecological communities.

Long-term summer warming reduces post-fire carbon dioxide losses in an arctic heath tundra

The frequency and extent of wildfires in the Arctic has been increasing due to climate change. However, there is a lack of understanding about long-term impacts of climate warming on post-fire carbon dioxide (CO2) exchange in arctic tundra ecosystems. To investigate this, we conducted an experimental low-intensity fire in combination with summer warming (using open top chambers) in a dry heath tundra ecosystem in West Greenland. We report here on the impact four and five years after the fire. We also examined immediate effects of soil heating to three temperature levels (35, 55 and 80 °C), as a simulation of heat transfer during a typical tundra fire. Fire increased soil organic phosphorus concentrations up to at least four years after the burning. The burned areas remained a net CO2 source five years after the fire, mainly due to the lower aboveground vegetation biomass and reduced gross ecosystem production (GEP). However, with four to five years of summer warming, the GEP, ecosystem respiration and soil respiration significantly increased, and burned areas turned into a net CO2 sink. Ex-situ soil heating to the temperature of 55 °C, reaching the heat load comparable with in-situ burning, had minor effects on soil GHG fluxes. This suggests that soil GHG activities are not immediately affected by heat transfer and associated soil temperature increases during a typical low-intensity wildfire in arctic dry tundra. Overall, our results reveal that in a future warmer climate, vegetation is likely to recover more quickly from fires, resulting in a reduction in post-fire CO2 losses.

Changes in European fire weather extremes and related atmospheric drivers

Recent destructive fire seasons around the world have increased concern that climate change is escalating the frequency, intensity, and extent of wildfires. While the contributions of individual factors can be debated, the scientific literature concludes that fire weather is one prominent driver of fire activity. Our analysis of the relationship between fire weather extremes and burned area in Europe revealed that the number of extreme fire weather days per year correlates positively with the annual burned area over most of the study domain. The evidence presented in our study strongly suggests that fire weather extremes in Europe have become more frequent in recent decades while affecting increasingly larger areas and occurring earlier and later in the fire season. Increases in fire weather extremes occurred abruptly in several parts of Europe, as evidenced by the detection of statistically significant change-points in the time series of the annual extreme fire weather days. Our analysis revealed that, at the regional scale, significant change-points occurred around the late 1990s and mid-2000s in the Mediterranean, marking an abrupt rise in the median of extreme fire weather days per year. We found that high-latitude blocking and sub-tropical ridging drive fire weather extremes in northern and southern Europe, respectively. The results of our study suggest that fire weather extremes are today more likely to occur than in the past, and the increasing occurrence of extreme fire weather could lead to rapidly reaching adaptation limits, thereby reversing currently stagnating or even declining trends reported for fire activity in Europe. Corresponding with extreme fire weather years reported here, recent destructive fire seasons exemplify the limits of fire suppression and the need to adapt to the reality of more frequent extreme fire weather.

Remote sensing delineation of wildfire spatial extents and post-fire recovery along a semi-arid climate gradient

Understanding the wildfire extent and post-fire vegetation recovery is critical for fire and forest management. Remote sensing imagery is widely used in wildfire detection because it provides continuous and large-scale surface monitoring capability. In this study, we apply and evaluate the performance of the LandTrendr algorithm in wildfire detection across a semi-arid climate region with a marked precipitation gradient. The aims are to compare the performance of four spectral indices for the burned areas and post-fire recovery detection for different climate conditions and investigate the relationship between suitable model parameters and climate conditions. The results show that NDVI outperforms other indices, including NBR, in burned area detection for drier areas (annual precipitation <400 mm). Disturbance signal-to-noise ratio can serve as an indicator for suitable index selection for semi-arid areas. Although the performance in the detection of burned pixels varies among different indices, they are all suitable for delineating post-fire recovery except for the wet site (annual precipitation of 575 mm) where NBR displays the best performance. Parameter optimization results along the climate gradient show that climate conditions have a significant impact on suitable parameter selection. These findings provide guidance on vegetation wildfire detection in arid and semi-arid climates to support wildfire risk and forestry management.

Consequential lightning-caused wildfires and the “let burn” narrative

BackgroundCurrent guidance for implementation of United States federal wildland fire policy charges agencies with restoring and maintaining fire-adapted ecosystems while limiting the extent of wildfires that threaten life and property, weighed against the risks posed to firefighters. These ostensibly conflicting goals can make it difficult to clearly communicate specific response objectives of a given incident. Inherent ambiguity can expose land management agencies, like the United States Department of Agriculture Forest Service (USFS), to scrutiny when once remote, lightning-ignited wildfires burn across boundaries and result in damage. One such incident was the 2021 Tamarack Fire, ignited by lightning in a remote USFS wilderness area and ultimately burning 27,776 ha across multiple jurisdictions and destroying 25 structures. Intense sociopolitical interest developed around this incident, reigniting a “let burn” policy debate of the USFS despite this policy not formally existing. We provide a first approximation at quantifying the base rates of potentially consequently lightning-caused fires like the Tamarack Fire. We use multiple sources of fire-reporting data to characterize USFS fires from 2009 to 2020 by management-strategy to identify Tamarack Fire analogs. Within Incident Command System 209 (ICS-209) reports for fires originating on USFS lands, we identified 32 wildfires with similar key characteristics to the Tamarack Fire; nearly half ignited within wilderness areas.ResultsInitial strategies were driven by resource objectives for only six of the 32 wildfires; firefighter hazard mitigation was the primary driver of all others. No fire exhibited every characteristic of the Tamarack Fire. Analog fires accounted for a small percent (3.4%) of large (> 121 ha) USFS lightning-caused ignitions. These fires were responsible for 61.6% of structures destroyed and 25.8% of total personnel commitments of large lightning-caused USFS fires.ConclusionsLightning-ignited wildfires that could have resulted in sociopolitical controversy are rare, and those with strategies driven by resource objective are even rarer. More commonly, risks posed to firefighters from terrain, snags, or accessibility are factors driving strategy, even when fires ignite within wilderness areas. These results suggest that simple definitions of strategy such as those reported within the ICS-209 lack clarity and may increase sociopolitical pressure on the agency to continue aggressive fire exclusion strategies.

How does wildfire and climate variability affect streamflow in forested catchments? A regional study in eastern Australia

The impact of wildfire on catchment water yield remains uncertain, with case studies reporting a range of observed response paths. Additionally, the impacts of fire and climate variability are often intertwined, making them difficult to evaluate separately. This study assesses how wildfire and climate influence streamflow in forested catchments. We focused on selected forested catchments in eastern Australia that have experienced both sustained drought and large fire events, but otherwise have experienced little hydrological modification. We compared the relationship between streamflow and rainfall before and after the severe fire events in the 2019/2020 season and over a longer multi-year period. We obtained historical data for streamflow, rainfall, and wildfire extent, timing, and severity for each catchment. The study found a consistent increase in streamflow with given rainfall after the 2019/2020 fire event. However, the timing of the fire aligned with the end of a prolonged major drought that affected the region. Dry conditions decrease runoff while fire increases it, which makes it difficult to attribute the flow increase to fire alone. We also assessed the relative importance of multiple potential drivers (climatic and fire-related) of changes in streamflow over a longer, multi-year historical period. We found that the impacts of historical wildfires on streamflow are generally smaller than the impacts of hydro-climatic factors such as catchment storage, which has a relative importance for the streamflow over 3 times greater than that of the fire-related factors. Our results imply that historical changes in flow in the study region are more heavily affected by climate variability than by fires at the catchment scale. They emphasize the importance for water resources management of considering regional drivers such as changing climatic conditions over wildfire, which often affects only parts of individual catchments.

Climate predicts wildland fire extent across China

Wildland fire extent varies seasonally and interannually in response to climatic and landscape-level drivers, yet predicting wildfires remains a challenge. Existing linear models that characterize climate and wildland fire relationships fail to account for non-stationary and non-linear associations, thus limiting prediction accuracy. To account for non-stationary and non-linear effects, we use time-series climate and wildfire extent data from across China with unit root methods, thus providing an approach for improved wildfire prediction. Results from this approach suggest that wildland area burned is sensitive to vapor pressure deficit (VPD) and maximum temperature changes over short and long-term scenarios. Moreover, repeated fires constrain system variability resulting in non-stationarity responses. We conclude that an autoregressive distributed lag (ARDL) approach to dynamic simulation models better elucidates interactions between climate and wildfire compared to more commonly used linear models. We suggest that this approach will provide insights into a better understanding of complex ecological relationships and represents a significant step toward the development of guidance for regional planners hoping to address climate-driven increases in wildfire incidence and impacts.

Lightning-Ignited Wildfires beyond the Polar Circle

Warming-driven lightning frequency increases may influence the burning rate within the circumpolar Arctic and influence vegetation productivity (GPP). We considered wildfire occurrence within the different Arctic sectors (Russian, North American, and Scandinavian). We used satellite-derived (MODIS) data to document changes in the occurrence and geographic extent of wildfires and vegetation productivity. Correlation analysis was used to determine environmental variables (lightning occurrence, air temperature, precipitation, soil and terrestrial moisture content) associated with a change in wildfires. Within the Arctic, the majority (&gt;75%) of wildfires occurred in Russia (and ca. 65% in Eastern Siberia). We found that lightning occurrence increase and moisture are primary factors that meditate the fire frequency in the Arctic. Throughout the Arctic, warming-driven lightning influences fire occurrence observed mainly in Eastern Siberia (&gt;40% of explained variance). Similar values (ca. 40%) at the scale of Eurasia and the entire Arctic are attributed to Eastern Siberia input. Driving by increased lightning and warming, the fires’ occurrence boundary is shifting northward and already reached the Arctic Ocean coast in Eastern Siberia. The boundary’s extreme shifts synchronized with air temperature extremes (heat waves). Despite the increased burning rate, vegetation productivity rapidly (5–10 y) recovered to pre-fire levels within burns. Together with increasing GPP trends throughout the Arctic, that may offset fires-caused carbon release and maintain the status of the Arctic as a carbon sink.

Multimodal Wildland Fire Smoke Detection

Research has shown that climate change creates warmer temperatures and drier conditions, leading to longer wildfire seasons and increased wildfire risks in the United States. These factors have, in turn, led to increases in the frequency, extent, and severity of wildfires in recent years. Given the danger posed by wildland fires to people, property, wildlife, and the environment, there is an urgent need to provide tools for effective wildfire management. Early detection of wildfires is essential to minimizing potentially catastrophic destruction. To that end, in this paper, we present our work on integrating multiple data sources into SmokeyNet, a deep learning model using spatiotemporal information to detect smoke from wildland fires. We present Multimodal SmokeyNet and SmokeyNet Ensemble for multimodal wildland fire smoke detection using satellite-based fire detections, weather sensor measurements, and optical camera images. An analysis is provided to compare these multimodal approaches to the baseline SmokeyNet in terms of accuracy metrics, as well as time-to-detect, which is important for the early detection of wildfires. Our results show that incorporating weather data in SmokeyNet improves performance numerically in terms of both F1 and time-to-detect over the baseline with a single data source. With a time-to-detect of only a few minutes, SmokeyNet can be used for automated early notification of wildfires, providing a useful tool in the fight against destructive wildfires.