Summer Fires Research Articles

Coupled Effects of High Temperatures and Droughts on Forest Fires in Northeast China

High temperatures and droughts are two natural disasters that cause forest fires. During climate change, the frequent occurrence of high temperatures, droughts, and their coupled effects significantly increase the forest fire risk. To reveal the seasonal and spatial differences in the coupled effects of high temperatures and droughts on forest fires, this study used the Copula method and proposed the compound extremely high-temperature and drought event index (CTDI). The results indicated that the study area was subject to frequent forest fires in spring (71.56%), and the burned areas were mainly located in forests (40.83%) and the transition zone between farmland and forests (36.91%). The probability of forest fires in summer increased with high temperatures and drought intensity, with high temperatures playing a dominant role. The highest forest fire hazard occurred in summer (>0.98). The probability of a forest fire occurring under extreme meteorological conditions in summer and fall was more than twice as high as that in the same zone under non-extreme conditions. Droughts play a significant role in the occurrence and spread of forest fires during fall. These results can provide decision-making support for forest fire warnings and fire fighting in the Northeast China forest zone.

Spatiotemporal patterns and drivers of extreme fire severity in Spain for the period 1985–2018

Extreme fire severity patterns driven by climate change have deep consequences on vegetation, subsequent fire regimes and have consequences on the effectiveness of extinction. In this work, we aimed to determine if extreme fire severity defined as the 90th percentile of RdNBR has changed in Spain in the last 3 decades, if extreme fire severity patterns have differed among the different vegetation types and what drivers have influenced extreme fire severity in both summer and non-summer fires. We have used perimeters of large wildfires (≥100 ha, n = 1719) from 1985 to 2018 in four pyroregions and the main dominant vegetation types. We have analyzed time series for each pyroregion and vegetation type to determine if there were significant trends and breakpoints in extreme fire severity. We have also analyzed the effects of drought, weather, topography and vegetation on extreme fire severity in seasonal wildfires.Extreme fire severity increased in summer fires from 1985 to 2018, especially in the East and North pyroregions, while the Southwest pyroregion reached highest values in summer. There has been an increase of severity in shrubland, mosaic vegetation and conifer forests in summer. Broadleaved forests had the lowest values of fire severity and did not show any trend in the period considered. The most important drivers of extreme fire severity are, in order of importance, pyroregion, elevation, slope, vapor pressure deficit (VPD) and vegetation type for summer fires, and VPD, vegetation types, pyroregion, windspeed and drought for non-summer fires. Global change is increasing climate-related events. Our results indicate that extreme fire severity in summer has been on the rise in recent decades in Spain, suggesting that, in a climate warming context, without strategic management of these increasingly flammable landscapes, further increases may be likely.

Anatomy of a post-wildfire recovery: Responses of mammals to a Black Summer wildfire in a fox-free landscape

Wildfires are predicted to increase in frequency and severity with climate change. Devising effective strategies to ensure wildfires do not hasten a decline in wildlife populations hinges on developing a deeper understanding of how species are affected by recent wildfires. I investigated the response of eight species of medium-sized mammals over a 4-year period (2020–2023) following a wildfire in the Australian Black Summer fire season. Pre-wildfire population levels were not known. These species differed in their ability to survive the passage of fire; from being able to flee the fire front, to remaining in protective shelters, to favouring unburnt forest types, to none of these strategies. Camera trapping was conducted from 5 months to 4 years after the fire across 62 sites in wet and dry sclerophyll forest (burnt and unburnt) and rainforest (unburnt) to characterise both initial survival and subsequent reproduction-led post-fire occupancy. There was consistency in the response of species in year 1. Those assumed to be able to flee the fires showed medium-high post-fire occupancy regardless of whether a site was burnt. Those that use protective shelters and unburnt forest also showed high occupancy. One species without these options showed greatly reduced occupancy in year 1 relative to years 3 and 4. Most species showed evidence of increased detection across years, which is inferred to reflect increased abundance, and was expected given substantially above average rainfall for three years following the fire. The feral cat was the only predator sufficiently widespread to be of concern in species’ recovery but was rarely detected in years 1 and 2, relative to years 3 and 4. This study provides evidence that many species, including three threatened species, have the ability to survive the passage of fire, and show high post-fire occupancy. The study landscape contained abundant habitat elements (unburnt rainforest, boulder fields) that promote survival through a wildfire and post-fire recovery, providing insights to guide future conservation actions.

Benefits to Native Grasses from a Summer Fire Still Present 12 Years Later

Benefits to Native Grasses from a Summer Fire Still Present 12 Years Later

Multiparameter Detection of Summer Open Fire Emissions: The Case Study of GAW Regional Observatory of Lamezia Terme (Southern Italy)

In Southern Mediterranean regions, the issue of summer fires related to agriculture practices is a periodic recurrence. It implies a significant increase in carbon dioxide (CO2) emissions and other combustion-related gaseous and particles compounds emitted into the atmosphere with potential impacts on air quality and global climate. In this work, we performed an analysis of summer fire events that occurred on August 2021. Measurements were carried out at the permanent World Meteorological Organization (WMO)/Global Atmosphere Watch (GAW) station of Lamezia Terme (Code: LMT) in Calabria, Southern Italy. The observatory is equipped with greenhouse gases and black carbon analyzers, an atmospheric particulate impactor system, and a meteo-station for atmospheric parameters to characterize atmospheric mechanisms and transport for land and sea breezes occurrences. High mole fractions of carbon monoxide (CO) and carbon dioxide (CO2) coming from quadrants of inland areas were correlated with fire counts detected via the MODIS satellite (GFED-Global Fire Emissions Database) at 1 km of spatial resolution. In comparison with the typical summer values, higher CO and CO2 were observed in August 2021. Furthermore, the growth in CO concentration values in the tropospheric column was also highlighted by the analyses of the L2 products of the Copernicus SP5 satellite. Wind fields were reconstructed via a Weather Research and Forecasting (WRF) output, the latter suggesting a possible contribution from open fire events observed at the inland region near the observatory. So far, there have been no documented estimates of the effect of prescribed burning on carbon emissions in this region. This study suggested that data collected at the LMT station can be useful in recognizing and consequently quantifying emission sources related to open fires.

Few large or many small fires: Using spatial scaling of severe fire to quantify effects of fire‐size distribution shifts

AbstractAs wildfire activity increases and fire‐size distributions potentially shift in many forested regions worldwide, anticipating the spatial patterns of burn severity expected with future fire activity is critical for ecological understanding and informing management and policy. Because spatial patterns of burn severity are influenced by a complex mixture of drivers, they remain difficult to predict for any given burned landscape. At broader extents, however, spatial scaling relationships relating high‐severity patch size and shape to overall fire size, when combined with scenarios regarding regional area burned and fire‐size distributions, offer a means to anticipate the spatial configuration of burn severity in future fires. Here, leveraging a satellite burn‐severity dataset for 1615 fire events occurring across the northwest United States between 1985 and 2020, we present an approach for simulating expected patch‐level burn‐severity patterns at the scale of a region or fire regime of interest. We demonstrate this approach in a historically climate‐limited fire regime within the Pacific Northwest, USA, where relatively infrequent but large and severe fires shape biomass‐rich forests, and where fire potential is projected to increase as summer fire seasons become warmer and drier. We quantify how, for a given total burned area, the range of cumulative burn‐severity patterns is expected to vary with the size distributions of fire events. Our results illustrate how shifts in fire‐size distributions toward larger fire events will lead to increasingly large high‐severity burn patches with interior areas that are increasingly far from unburned seed sources following fire. In contrast, the same total area burned in more numerous but smaller fire events will result in qualitatively different cumulative patterns of burn severity, characterized by smaller high‐severity patches and closer proximity to postfire seed sources across burned landscapes. These results have important implications in forested regions, informing management actions ranging from prefire planning (e.g., fire response preparedness) to real‐time decision‐making (e.g., fire suppression vs. managed wildfire use) and postfire responses (e.g., replanting to restore tree cover and/or promoting early‐seral habitat). The approach we present is generalizable and can be applied across regions and fire regimes to anticipate potential future fire effects.

Niche-based approach to explore the impacts of environmental disturbances on biodiversity.

Globally, species are increasingly at risk from compounding threatening processes, an increasingly prominent driver of which is environmental disturbances. To facilitate effective conservation efforts following such events, methods that evaluate potential impacts across multiple species and provide landscape-scale information are needed to guide targeted responses. Often, the geographic overlap between a disturbance and species' distribution is calculated and then used as a proxy for potential impact. However, such methods do not account for the important influence of environmental heterogeneity throughout species' ranges. To address this shortcoming, we quantified the effects of environmental disturbances on species' environmental niche space. Using the Australian 2019 and 2020 Black Summer fires as a case study, we applied a niche-centric approach to examine the potential impacts of these fires on 387 vertebrate species. We examined the utility of established and novel niche metrics to assess the potential impacts of large-scale disturbance events on species by comparing the potential effects of the fires as determined by our various niche measures to those derived from geographic-based measures of impact. We examined the quality of environmental space affected by the disturbance by quantifying the position in niche space where the disturbance occurred (center or margin), the uniqueness of the environmental space that was burned, and the degree to which the remaining, unburned portion of the niche differed from a species' original prefire niche. There was limited congruence between the proportion of geographic and niche space affected, which showed that geographic-based approaches in isolation may have underestimated the impact of the fires for 56% of modeled species. For each species, when combined, these metrics provided a greater indication of postdisturbance recovery potential than geographic-based measures alone. Accordingly, the integration of niche-based analyses into conservation assessments following large-scale disturbance events will lead to a more nuanced understanding of potential impacts and guide more informed and effective conservation actions.

Severe and Short Interval Fires Rearrange Dry Forest Fuel Arrays in South-Eastern Australia

Fire regimes have shaped extant vegetation communities, and subsequently fuel arrays, in fire-prone landscapes. Understanding how resilient fuel arrays are to fire regime attributes will be key for future fire management actions, given global fire regime shifts. We use a network of 63-field sites across the Sydney Basin Bioregion (Australia) to quantify how fire interval (short: last three fires <10 years apart, long: last two fires >10 years apart) and severity (low: understorey canopy scorched, high: understorey and overstorey canopy scorched), impacted fuel attribute values 2.5 years after Australia’s 2019–2020 Black Summer fires. Tree bark fuel hazard, herbaceous (near-surface fuels; grasses, sedges <50 cm height) fuel hazard, and ground litter (surface fuels) fuel cover and load were higher in areas burned by low- rather than high-severity fire. Conversely, midstorey (elevated fuels: shrubs, trees 50 cm–200 m in height) fuel cover and hazard were higher in areas burned by high- rather than low-severity fire. Elevated fuel cover, vertical connectivity, height and fuel hazard were also higher at long rather than short fire intervals. Our results provide strong evidence that fire regimes rearrange fuel arrays in the years following fire, which suggests that future fire regime shifts may alter fuel states, with important implications for fuel and fire management.

Resilience to summer bushfire in the threatened orchid, Caladenia tessellata, in terms of pollination success, herbivory, and mycorrhizal associations

Abstract In some biogeographic regions, many threatened plant species occur in habitats that periodically experience bushfire. However, we currently have relatively little information on how important plant–animal and plant–fungus interactions are affected by these fires. For the threatened sexually deceptive orchid Caladenia tessellata we test whether pollination rate, frequency of florivory, and the species of mycorrhizae the plant associates with differ between burnt and unburnt sites. Interestingly, pollination rates were unaffected by fire, demonstrating that populations of the thynnine wasp pollinator can persist post-fire. However, there was a significant negative relationship between number of flowers in a population and pollination success, which is likely a by-product of a deceptive pollination strategy. Despite the presence of vertebrate herbivores, florivory rates were low in both burnt and unburnt sites. Caladenia tessellata associated primarily with the mycorrhiza Serendiptia australiana, regardless of fire history. While our results suggest resilience to a one-off summer fire for the ecological interactions that we measured, it would be interesting to investigate the effects of fire frequency and time of year. High reproductive rates in small populations of C. tessellata suggest these populations may be viable and that retaining them is a high priority for conservation.

Entangled Plumwoods: Stewardship as Grassroots Conservation Humanities

Hundreds of thousands of hectares of bushland and accompanying biodiversity were lost over a few short weeks during the Black Summer fires of 2019–2020 along the east coast of Australia. On the night of 19 December 2019, fire swept up the escarpment from the coast, slowed down with the thick understory of temperate rainforest and burnt through the lower dry sclerophyll forest on Plumwood Mountain. The aftermath of the bare, burnt landscape meant a significant change in the structure and diversity of vegetation, while the consequences of the fire also brought about fundamental changes to Plumwood as a conservation and heritage organisation. Plumwood Mountain as a place, the individual plumwood tree as an agentive being, Val Plumwood as a person and Plumwood as an organisation are all an entangled form of natureculture and indicative of a practice-based conservation humanities approach. Conservation as part of the environmental humanities can offer an alternative to mainstream models of conservation with the potential to instigate active participation on the ground, engaging in a different form of stewardship.

The Other Side of Fire in a Changing Environment: Evidence from a Mediterranean Country

In forested ecosystems all over the world, usually, fire is the main disturbance, and due to global climate change, its effects are worsening in many areas. Although fire impacts have been studied for many years, integrative analyses of their effects on various ecosystem services (ES) at different scales are uncommon. This study tries to assess the ecological role of fire in a changing environment, focusing on a Mediterranean country. Data were collected by the use of an online questionnaire in Greece, where the summer fires in the last decades have had significant impacts on the environment and the economy and, in many cases, there were many human and animal victims from them. The sample size of the survey was 384 workers in the primary production sector from all over the country. The study showed that fire has several effects on animal husbandry, the quality of soil nutrients and fertility, the overall vegetation cover, and on general biodiversity. It seems that the degree to which fire has an effect on ecosystem components depends on the intensity, frequency, and length of the fires. Additionally, the frequency, intensity, and length of fire affect the impacts of fire on herbaceous plant, woody vegetation, soil physical qualities, and on the different animals’ habitats.

Investigating the Presence of Biomass Burning Events at Ny-Ålesund: Optical and Chemical Insights from Summer-Fall 2019

Summer 2019 is remembered as one of the most intense biomass burning (BB) seasons on record for the Northern Hemisphere. During the MOSAiC expedition, a smoke-dominated layer was identified in the upper troposphere over the North Pole region. The origin of this layer remains unclear, and no evidence has been found to indicate the intrusion of such particles into the Arctic Boundary Layer. The main aim of this work was to evaluate if biomass burning events in the summer 2019 were detectable at Gruvebadet Atmospheric Laboratory, close to Ny-Å lesund (Svalbard Islands) during the second half of 2019. This paper proposes an innovative approach to discriminate biomass burning events based on optical measurements combined with chemical analysis and air mass back-trajectories. Monthly background values of optical coefficients were defined using multi-annual (2018–2021) statistics and twelve possible events were identified. Source apportionment through positive matrix factorization (PMF) identified that the biomass burning factor by PMF accounted for only 2% of the total investigated concentration. The specific biomass burning tracers such as levoglucosan and phenolic compounds were compared with optical measurements and with the PMF results. Air mass trajectory analysis revealed that the early summer fires detected at Ny-Å lesund originated mainly from North America, as also confirmed by the presence of BB factor of PMF, levoglucosan and also vanillic species (softwood combustion tracers). In contrast, the chemical composition and air masses analysis of the highest peak detected in early December suggested residential heating as plausible source, further amplified by the onset of the harsh winter season and the expansion of the polar vortex towards mid-latitudes.

Care and crisis: disaster experiences of Australian parents since 1974

ABSTRACT The historical influence of environmental factors on families has received relatively little scholarly attention. In this article we explore the impact of the ‘natural’ or ‘more-than-human’ world on Australian families through one of the most powerful examples of environmental influence: disasters. We take three case studies as our focus: Cyclone Tracy (1974), the 2011 Queensland Floods and the 2019-20 Black Summer Fires. Our primary source materials are oral history interviews with Australian parents, some of which are archived interviews in cultural collections and some of which are contemporary interviews newly-created for this research. Through these case studies spanning half a century, we analyse change and continuity in the ways in which disasters have been experienced and remembered by Australian parents. While parents consistently shoulder an additional burden during disaster by caring for children, the ways they do so are distinctly gendered and have remained so across time. But as disasters increase in frequency, ferocity and severity in an era of climate change, the way parents understand, respond and prepare for environmental crises is shifting. Australian parents increasingly see their childrearing duties as encompassing consideration of extreme weather in locating or renovating a family home, practicing evacuation drills, and anticipating potential disasters in planning family holidays. Awareness of climate risks is even influencing reproductive decisions about family size or whether to become a parent. We hypothesise that shifts in individual parent‘s disaster experiences may be collectively changing Australian cultural ideals of ‘good’ parenthood in the twenty-first century. Research conducted at the intersection of the history of the family and environmental history is becoming urgently significant in the present-day, as we seek to make sense of rapid environmental change and its personal and cultural impacts on our human lives.

Untangling fuel, weather and management effects on fire severity: Insights from large-sample LiDAR remote sensing analysis of conditions preceding the 2019-20 Australian wildfires

Evaluation of fire severity reduction strategies requires the quantification of intervention outcomes and, more broadly, the extent to which fuel characteristics affect fire severity. However, investigations are currently limited by the availability of accurate data on fire severity predictors, particularly relating to fuel. Here, we used airborne LiDAR data collected before the 2019-20 Australian Black Summer fires to investigate the contribution of fuel structure to fire severity under a range of weather conditions. Fire severity was estimated using the Relative Burn Ratio calculated from Sentinel-2 optical remote sensing imagery. We modelled the effects of various fuel structure estimates and other environmental predictors using Random Forest models. In addition to variables estimated at each observation point, we investigated the influence of surrounding landscape characteristics using an innovative method to estimate fireline progression direction. Our models explained 63–76% of fire severity variance using parsimonious predictor sets. Fuel cover in the understorey and canopy, and vertical vegetation heterogeneity, were positively associated with fire severity. Up-fire burnt area and recent planned and unplanned fire reduced fire severity, whereby unplanned fire provided a longer-lasting reduction of fire severity (up to 15 years) than planned fire (up to 10 years). Although fuel structure and land management effects were important predictors, weather and canopy height effects were dominant. By mapping continuous interactions between weather and fuel-related variables, we found strong evidence of diminishing fuel effects below 20–40% relative air humidity. While our findings suggest that land management interventions can provide meaningful fire severity reduction, they also highlight the risk of warmer and drier future climates constraining these advantages.

Contrasting immediate impact of prescribed fires and experimental summer fires on soil organic matter quality and microbial properties in the forest floor and mineral soil in Mediterranean black pine forest

Prescribed fire (PB) is used to achieve ecological objectives and to reduce fuel hazard thus limiting detrimental impacts of wildfire and appropriate selection of prescription window is critical for these goals. Operational use of PB in the Mediterranean forest is scarce and information about its effects on soil remains incomplete. This study for the first time i) compared the immediate impact of spring and autumn PB and experimental summer fire on key properties of forest floor and mineral topsoil in Mediterranean black pine forest, and ii) assessed the capacity of PB to reduce fuel, with limited immediate impacts on soil. PB significantly reduced the 32.5 % of pre-fire forest floor depth, while summer fire consumed 88.5 % and exposed about 30 % of the mineral soil surface. Mean maximum temperature during fire at the mineral soil surface was 23 °C in PB, in contrast to 128 °C in summer fire, while soil heating at 2 cm depth was negligible in both cases. PB did not cause immediate changes in OM quality parameters, and chemical (C and N concentrations, C/N and pH) and microbiological properties (Cmic, Cmic/C, and β-glucosidase, acid phosphatase and alkaline phosphatase activities) in forest floor or mineral topsoil (0–2 cm). By contrast, summer fire greatly increased OM recalcitrance and reduced Cmic, Cmic/C and enzyme activities in forest floor immediately after fire. In the mineral topsoil, only microbial properties were significantly reduced. The maximum temperature reached during fire in forest floor and topsoil was associated with most of the overall changes in properties in both layers. The findings suggest that prescribed fire can significantly reduce fuel with limited initial impacts on soil. Although these findings are encouraging for operational use of prescribed burning in the ecosystem under study, long-term monitoring of repeated application of the technique on soil properties and other ecosystem components is necessary.

Stability of C3 and C4 Grass Patches in Woody Encroached Rangeland after Fire and Simulated Grazing

As the woody legume, Prosopis glandulosa (honey mesquite) has encroached into grasslands and rangelands in the southern Great Plains, USA, two grass species, C4 shortgrass, Buchloe dactyloides (buffalograss), and C3 mid-grass, Nassella leucotricha (Texas wintergrass), have increased in dominance. Occurrence of more productive C4 mid-grasses and herbaceous diversity have declined. We measured effects of various combinations of spring clipping (to simulate cattle grazing) and summer and/or winter fire treatments on the stability of monoculture patches of these two grass species over an eight-year period, with the goal of reducing Nassella and increasing C4 mid-grass cover. All fire treatments top-killed most Prosopis trees that subsequently resprouted. Buchloe cover declined in the No Clip + No Fire treatment but remained intact with clipping and/or fire. Frequent clipping reduced Nassella cover across all fire treatments. Buchloe encroachment into Nassella patches was greatest in the Clip + Alternate Season fire treatment. C4 mid-grass cover increased to 15–25% in Nassella patches in several fire-only or Clip + Fire treatments; greatest gains were observed in treatments that included summer fire. In contrast, C4 mid-grass gains were lower in Buchloe patches. These results suggest that C4 mid-grass restoration was linked with treatments that reduced Nassella cover.

The warming city: the increasing risk of summer fires in Delhi.

Rising temperatures are mainly associated with wildfires, but the incidence of fire may also increase in the urban context. Yet, fire in Delhi, India, as elsewhere in the towns and cities of the Global South, remains largely invisible, despite the nearly 11 million people each year who are burnt severely enough to require medical attention. This paper focuses on whether summer temperatures in Delhi are rising and whether higher temperatures and lower humidity contribute to a greater number of fires in urban areas. The data strongly suggest a relationship between the warming city, a growing number of summer fires, and mounting temperatures around the world. Delhi, however, is only one example of an urban reality that is common to much of the Global South. Similar questions about the incidence of fire and whether the number is increasing need to be asked of other towns and cities that share the same vulnerabilities.

Australia’s Black Summer wildfires recovery: A difference-in-differences analysis using nightlights

This study examines how communities of New South Wales (NSW), Australia, recovered from the extreme wildfire event of 2019–2020 (i.e., the Black Summer fires). Using monthly night-time radiance as an indicator of economic activity in a geographic area (i.e., a mesh block) from January 2017 to June 2021, I conducted a spatio-temporal and socio-economic analysis of economic recovery after the 2019–2020 wildfires using the difference-in-differences method. This is the first study to examine the intersectional role of space with time and socio-economic characteristics for extreme wildfire recovery. The findings reveal that wildfire-affected locations had about 0.038σ and 0.026σ lower night-time radiance in major cities and rural hinterlands (i.e., inner regions), respectively, than the unaffected areas. These numbers translate to approximately 30% reduction in economic activities in both areas. The findings remain consistent when using Facebook’s movement range data. The pace of recovery varied spatially across time and socio-economic groups. In rural hinterlands of NSW, wildfire-affected communities, both poor and non-poor, followed a slower recovery trajectory than wildfire-affected city dwellers. In major cities, the economic recovery of poor communities lagged behind non-poor communities. Accounting for such spatial, temporal and socio-economic heterogeneity in the natural hazard recovery process can support the design of equitable wildfire risk reduction and management strategies and programs. If unaddressed, gaps in wildfire recovery can increase location and economic group specific vulnerabilities to future wildfires. Note that nightlights are not a good proxy for economic activity in heavily forested remote and rural areas; thus limiting the application of the use of high frequency satellite data for wildfire recovery analysis only in major cities and rural hinterlands.

How the extreme 2019–2020 Australian wildfires affected global circulation and adjustments

Abstract. Wildfires are a significant source of absorbing aerosols in the atmosphere. Extreme fires in particular, such as those during the 2019–2020 Australian wildfire season (Black Summer fires), can have considerable large-scale effects. In this context, the climate impact of extreme wildfires unfolds not only because of the emitted carbon dioxide but also due to smoke aerosol released up to an altitude of 17 km. The overall aerosol effects depend on a variety of factors, such as the amount emitted, the injection height, and the composition of the burned material, and is therefore subject to considerable uncertainty. In the present study, we address the global impact caused by the exceptionally strong and high-reaching smoke emissions from the Australian wildfires using simulations with a global aerosol–climate model. We show that the absorption of solar radiation by the black carbon contained in the emitted smoke led to a shortwave radiative forcing of more than +5 W m−2 in the southern mid-latitudes of the lower stratosphere. Subsequent adjustment processes in the stratosphere slowed down the diabatically driven meridional circulation, thus redistributing the heating perturbation on a global scale. As a result of these stratospheric adjustments, a positive temperature perturbation developed in both hemispheres, leading to additional longwave radiation emitted back to space. According to the model results, this adjustment occurred in the stratosphere within the first 2 months after the event. At the top of the atmosphere (TOA), the net effective radiative forcing (ERF) averaged over the Southern Hemisphere was initially dominated by the instantaneous positive radiative forcing of about +0.5 W m−2, for which the positive sign resulted mainly from the presence of clouds above the Southern Ocean. The longwave adjustments led to a compensation of the initially net positive TOA ERF, which is seen in the Southern Hemisphere, the tropics, and the northern mid-latitudes. The simulated changes in the lower stratosphere also affected the upper troposphere through a thermodynamic downward coupling. Subsequently, increased temperatures were also obtained in the upper troposphere, causing a global decrease in relative humidity, cirrus amount, and the ice water path of about 0.2 %. As a result, surface precipitation also decreased by a similar amount, which was accompanied by a weakening of the tropospheric circulation due to the given energetic constraints. In general, it appears that the radiative effects of smoke from single extreme wildfire events can lead to global impacts that affect the interplay of tropospheric and stratospheric budgets in complex ways. This emphasizes that future changes in extreme wildfires need to be included in projections of aerosol radiative forcing.

Impact of experimental forest fragmentation and fire on the funnel-web spider, Atrax sutherlandi.

Habitat fragmentation is one of the leading causes of biodiversity loss and in many regions of the world, climate change now interacts with habitat fragmentation in, as yet, unknown ways. The Wog Wog habitat fragmentation experiment, located in New South Wales, Australia, is one of the longest experiments of its kind, running for over 35 years. The experiment provides an excellent opportunity to examine the effects of habitat fragmentation on population changes over long time scales. In this project, I am studying the impacts of both habitat fragmentation and the Australian Black Summer Fires of 2019-2020 on the population of the funnel-web spider, Atrax sutherlandi. The fires burned for more than four months, burning more than 45 million acres of land, 30 million of which were forested, including Wog Wog. These bushfires are estimated to have killed over one billion invertebrates. I created models to examine differences in pre- and post-fire presence and abundance in fragments versus continuous forest using data collected post-fire and for five years before the fires. Here we show that habitat fragmentation and fire do not interact to impact the funnel-web spider. Our results show that funnel-web presence and abundance did not differ before or after the fires or in habitat fragments compared to continuous forest. A potential explanation for the lack of an impact of fire is that funnel-webs live in burrows in the ground, which may protect them from fire. Also, a previous study from Wog Wog shows that habitat fragmentation did not impact funnel-web abundance in the period of time before the fire, likely because the spiders are generalists and invertebrate food webs remained intact in habitat fragments. Future studies should follow funnel-webs as the burned fragment communities continue to recover. To see the complete thesis, please visit https://scholar.colorado.edu/concern/undergraduate_honors_theses/mk61rj17t.