Peatlands are globally important carbon sinks and stores. Climate change threatens to alter carbon cycling in some regions of the Northern Hemisphere, causing them to become net sources of atmospheric carbon, exerting a positive feedback upon global climate. Furthermore, enhanced drying, increased human activity and vegetation succession in response to a warming climate have increased the frequency of wildfires in some peat-bearing regions, including areas underlain by permafrost. Such events can cause thousands of years’ worth of formerly stable carbon to be rapidly released into the atmosphere, imparting further climate warming.

The future response of peatlands to climate warming and wildfire remains uncertain, and as a result peatlands are rarely included in Earth System Models, despite their importance in the global carbon system. Understanding how changes in climate and anthropogenic activity in the past affected peatland ecosystem functioning will improve our understanding of how these sensitive ecosystems may respond to future projected changes and thus reduce this uncertainty.

Our project aims to assess how warming, drought and wildfire have impacted the resilience of peatlands and permafrost in the Northern Hemisphere over the past c. 2000 years. Several peat cores spanning a latitudinal gradient covering several regions including Russia, Poland, the Baltic states and Scandinavia will be analysed using multiple palaeoecological proxies at high resolution to reconstruct past changes in wildfire frequency, hydrology and vegetation. This will allow us to define baselines and threshold values for ecosystem shifts relevant to future projected changes in climate.

How to cite: Andrews, L., Słowiński, M., Roberts, H., Marcisz, K., Kołaczek, P., Halaś, A., Łuców, D., and Lamentowicz, M.: Identifying tipping points and threshold values for ecosystem functioning in northern peatlands during the climate crisis (PEATFLAMES), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15670, https://doi.org/10.5194/egusphere-egu23-15670, 2023.

Recent wildfire activity in semi-arid regions like western North America exceeds the range of historical records. High-resolution paleoclimate archives such as stalagmites could illuminate the link between hydroclimate, vegetation change, and fire activity in pre-anthropogenic climate states beyond the timescale of existing tree-ring records. Here we present an analysis of levoglucosan, a combustion-sensitive anhydrosugar, and lignin oxidation products (LOPs) in a stalagmite from White Moon Cave in the California Coast Range in order to reconstruct fire activity and vegetation composition across the 8.2 kyr event. Elevated levoglucosan concentrations suggest increased fire activity while altered LOP compositions indicate a shift toward more woody vegetation during the event, with the shift in vegetation preceding the increase in fire activity. These changes are concurrent with increased hydroclimate volatility as shown by carbon and calcium isotope proxies. Together, these records suggest that climate whiplash (oscillations between extreme wetness and aridity) and fire activity in California, both projected to increase with anthropogenic climate change, were tightly coupled during the early Holocene.

How to cite: Oster, J., Homann, J., de Wet, C., Breitenbach, S., and Hoffmann, T.: Linked fire activity and climate whiplash in California during the early Holocene, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2097, https://doi.org/10.5194/egusphere-egu23-2097, 2023.

Even though wildfires are an important ecological component of larch-dominated boreal forests in eastern Siberia, intensifying fire regimes may induce large-scale shifts in forest structure and composition. Recent paleoecological research suggests that such a state change, apart from threatening human livelihoods, may result in a positive feedback on intensifying wildfires and increased permafrost degradation [1]. Common fire-vegetation models mostly do not explicitly include detailed individual-based tree population dynamics. However, setting a focus on patterns of forest structure emerging from interactions among individual trees in the unique forest system of eastern Siberia may provide beneficial perspectives on the impacts of changing fire regimes. LAVESI (Larix Vegetation Simulator) has been previously introduced as an individual-based, spatially explicit vegetation model for simulating fine-scale tree population dynamics [2]. It has since been expanded with wind-driven pollen dispersal, landscape topography, and the inclusion of multiple tree species. However, until now, it could not be used to simulate effects of changing fire regimes on those detailed tree population dynamics.

We present simulations of annually computed tree populations during the past c. 20,000 years in LAVESI, while applying a newly implemented fire module. Wildfire ignitions can stochastically occur depending on the monthly fire weather. Within the affected area, fire intensity is mediated by surface moisture. Fire severity depends on the intensity, with scaled impacts on trees, seeds and the litter layer. Each tree has a chance to survive wildfires based on a resistivity estimated from its height and species-specific traits of bark thickness, crown height, and their ability to resprout. The modelled annual fire probability compares well with a local reconstruction of charcoal influx in lake sediments. Simulation results at a study site in Central Yakutia, Siberia, indicate that the inclusion of wildfires leads to a higher number of tree individuals and increased population size variability compared to simulations without fires. In the Late Pleistocene forests establish earlier when wildfires can occur. The new fire component enables LAVESI to serve as a tool to analyze effects of varying fire return intervals and fire intensities on long-term tree population dynamics, improving our understanding of potential state transitions in the Siberian boreal forest.

References:

[1] Glückler R. et al.: Holocene wildfire and vegetation dynamics in Central Yakutia, Siberia, reconstructed from lake-sediment proxies, Frontiers in Ecology and Evolution 10, 2022.

[2] Kruse S. et al.: Treeline dynamics in Siberia under changing climates as inferred from an individual-based model for Larix, Ecological Modelling 338, 101–121, 2016.

How to cite: Glückler, R., Gloy, J., Dietze, E., Herzschuh, U., and Kruse, S.: Simulating wildfire impacts on boreal forest structure over the past 20,000 years since the Last Glacial Maximum in Central Yakutia, Siberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13603, https://doi.org/10.5194/egusphere-egu23-13603, 2023.

Climate change and atmospheric CO₂ levels can influence wildfire properties through separate and potentially contrasting impacts on vegetation and climate. One way to examine the sensitivity of global wildfire properties to changes in climate and CO₂ levels is using an out-of-sample experiment, such as the Last Glacial Maximum (LGM; 21 ka BP). Charcoal records show reduced burning at the LGM, when CO₂ levels were ~ 185 ppm and the climate was cooler and drier. In this analysis, we isolated out the potential effects of LGM CO₂ levels and LGM climate on the spatial patterns of global wildfire properties.

Using three statistical models, we conducted simulations of the spatial distribution of global burnt area, fire size and fire intensity under four scenarios: modern climate/modern CO₂ levels, LGM climate/LGM CO₂ levels, modern climate/LGM CO₂ levels and LGM/ modern CO₂ levels. We used outputs from three coupled ocean–atmosphere models representative of the range of simulated LGM climates. The ecophysiological effect of CO₂ levels was explicitly accounted for through vegetation inputs. Gross primary productivity (GPP) and land cover were derived for the LGM and modern climate keeping either CO₂ levels at 395 ppm (modern), or setting them to 185 ppm, using the P Model, a first-principles model of GPP which allows continuous acclimation of photosynthetic parameters to environmental variations, and the BIOME4 equilibrium global vegetation model.

Our results show a reduction in burnt area under LGM CO₂ levels, both with modern and LGM climate inputs. In the case of the warmest of the LGM climate scenarios, this reduction was of the same magnitude as the combined LGM climate/LGM CO₂ levels scenario. However, the driest and coldest LGM climate scenario produced a reduction in burnt area even with modern CO₂ levels, and the largest reduction in burnt area with LGM CO₂.  The reduction was primarily driven by changes in vapour pressure deficit (VPD). Fire size increased under LGM climates, due to changes in wind and VPD. The lower CO₂ values at the LGM had no impact on fire size. Fire intensity increased under LGM climates and LGM CO₂ levels, with both effects of similar amplitude and changes driven primarily by VPD, GPP and diurnal temperature range. 

We compared our outputs with sedimentary charcoal records from the Reading Palaeofire Database (RPD). Overall, the burnt area LGM CO₂ levels/LGM climate scenario showed the greatest agreement, though depending on how cold and dry the LGM climate was, this agreement was either equal to LGM CO₂ levels or LGM climate alone. These results suggest that whilst there was reduced global burning at the LGM, there may have been larger and more intense fires. They also highlight the importance of the ecophysiological effect of CO₂ levels on fuels, a major control of burnt area and fire intensity regardless of climate. They point to the importance of including this effect in process-based fire models, as well as the importance of accurately estimating the amplitude of projected change for different climate variables in order to increase the reliability of future projections.

How to cite: Haas, O., Prentice, I. C., and Harrison, S. P.: Examining the response of different wildfire properties to changes in climate and CO2 levels at the Last Glacial Maximum, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4520, https://doi.org/10.5194/egusphere-egu23-4520, 2023.

The Black Summer bushfires (2019-2020) cost the Australian economy over 100 billion dollars and burnt a total of 18 million hectares. In just one season, around 20% of Australia's Eucalyptus forests burnt down and billions of animals perished. Recent catastrophic fires in Australia and North America have made scientists and policymakers question how the disruption of First Nations' burning practices has impacted fuel loads. For instance, we have learnt from modern Australian Indigenous communities, historical literature, and art works that Indigenous peoples have used cultural burning to rejuvenate patches of land and preserve open vegetation for hunting and cultural purposes. The advent of British invasion brought a change in the type of fire regimes and landscape management across much of the continent, which may have led to an increase in flammable fuels in forest settings. However, the actual degree of land-cover modification by early settlers has only been often debated in the academic literature and within management stakeholders.

The quantification of past land cover is needed to address such debates. Pollen is the key proxy to track past vegetation changes, but pollen spectra suffer from some important biases e.g. taphonomy, pollen productivity, dispersal capability. Estimating past vegetation cover from sedimentary pollen composition requires to correct for productivity and dispersal biases using empirical-based models of the pollen-vegetation relationship. Such models for quantitative vegetation reconstruction (e.g. REVEALS) have yet been mostly applied in the Northern Hemisphere in the last 15 years - here we present recent applications of this methodology from Australia. We show the quantification of land cover changes through pre- and post- British invasion on multiple records (n=51) across the southeastern Australian region. This represents the first regional application of REVEALS within the Australian continent.

We provide the first empirical evidence that the regional landscape before British invasion was a cultural landscape with limited tree cover as it was maintained by Indigenous Australians through cultural burning. Our findings suggest that the removal of Indigenous vegetation management has altered woodland fuel structure and that much of the region was predominantly open before colonial invasion. The post-colonial land modification has resonance in wildfire occurrence and management under the pressing challenges posed by climate change.

How to cite: Mariani, M., Connor, S., Fletcher, M.-S., Haberle, S., Stevenson, J., Kershaw, P., Herbert, A., Theuerkauf, M., and Bowman, D.: Feeding the flames: how colonialism led to unprecedented wildfires across SE Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3238, https://doi.org/10.5194/egusphere-egu23-3238, 2023.

Fires constitute a key source of emissions of greenhouse gasses and aerosols. Fire emissions can be quantified using models, and these estimates are influenced by the spatial resolution of the model and its input data. Here we present a novel global model based on the Global Fire Emissions Database (GFED) modelling framework for the estimation of fuel consumption and fire carbon emissions at a spatial resolution of 500 m. The model was primarily based on observation-derived data products from MODIS, reanalysis data for meteorology, and an updated field measurement synthesis database for constraining fuel load and fuel consumption. Compared to coarser models, typically with a resolution of 0.25°, the 500-m spatial resolution allowed for increased spatially resolved emissions and a better representation of local-scale variability in fire types. The model includes a separate module for the calculation of emissions from fire-related forest loss, using 30-m Landsat-based forest loss data. We estimated annual carbon emissions of 2.1 Pg C yr^-1, of which around 24% was from fire-related forest loss. Fuel consumption was on average a factor 10 higher in case of fire-related forest loss compared to fires without forest loss. Up to now, emission estimates from our new model are based on MODIS burned area with a 500-m resolution, leading to global emissions similar to GFED4s. However, novel high-resolution burned area datasets based on the Landsat and Sentinel-2 missions reveal substantially more global burned area. Our 500-m global fire model provides a suitable framework for converting these burned area products to emissions, with the prospect of substantially higher global emissions.

How to cite: van Wees, D., van der Werf, G. R., Randerson, J. T., Rogers, B. M., Chen, Y., Veraverbeke, S., Giglio, L., and Morton, D. C.: A global model for estimating fuel consumption and fire carbon emissions at 500-m spatial resolution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6184, https://doi.org/10.5194/egusphere-egu23-6184, 2023.

Wildfires are becoming a growing concern in the UK, as climate change increases the occurrence and persistence of periods of hot, dry weather. Vegetation type and management play an important but contested role in UK fire risk and resilience, and questions remain over the best ways to prevent large fires developing. Remote sensing can provide vital data on fire size, severity, and recovery times, but method effectiveness is dependent on understanding specific ecosystems. This research uses ground validation of four wildfires in the UK Peak District National Park to deliver insights which improve interpretation of satellite data in wildfire monitoring. These insights are then applied to a three-year remote sensing database of large wildfires in England and Wales, to give novel results on the links between vegetation type and management, and fire size and severity. Ecosystem resilience and recovery is further explored through analysing the vegetation growth post-fire at three of the four Peak District study sites. This project therefore develops and validates remote sensing methodology in wildfire research by combining field data with satellite imagery to yield new understandings of the relationships between vegetation and fire. 

How to cite: Lees, K. and Lenton, T.: The role of vegetation in UK upland wildfires: Risk, Resilience, and Remote Sensing, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7449, https://doi.org/10.5194/egusphere-egu23-7449, 2023.

Emissions from vegetation fires in tropical forests have the potential to turn the global land carbon sink into a source, affect atmospheric chemistry, and hence air quality. While natural forest fires are a rare phenomenon in tropical forests of South America and are usually of rather low intensity, deforestation fires and small land clearings in systems with high fuel loads can cause intense fires and high emissions. However, the high moisture content in tropical forests causes incomplete combustion and higher emissions of carbon monoxide (CO) than of carbon dioxide. The interacting effects of land use change, fuel load and moisture on fire intensity and emissions is, however, difficult to quantify at large scales because not all of those components are readily available from Earth observations in a consistent way. 

Here, we make use of several satellite products on vegetation, fire activity and atmospheric composition to quantify the effects of land use, fuel loads, fuel moisture on fuel consumption, emission factors and hence on emissions and atmospheric trace gas concentration. First, we use observations of active fires and fire radiative power from the VIIRS and Sentinel-3 SLSTR sensors to map different fire types (forest fires, deforestation fires, small land clearing and agricultural fires, savannah fires). Second, we integrate satellite products of canopy height, above-ground biomass, leaf area index, land cover and soil moisture in a novel data-model fusion framework to estimate fuel loads and moisture in vegetation, surface litter and woody debris. We then combine in a bottom-up approach the fire types with fuel loads and moisture to estimate fuel consumption and fire emissions using default emission factors. Third, we use observations from Sentinel-5p TROPOMI and the Integrated Forecast Systems (IFS) of the Copernicus Atmosphere Monitoring Service to compare the bottom-up estimates with distributions of CO and NOx in the atmosphere, which allows optimising emissions and associated emission factors.

Our reconciled estimates of fire emissions outperform previous CO estimates e.g. from the Global Fire Assimilation System, which demonstrates an improved estimation of fire carbon emissions. The results show that the high fire intensity and emissions in tropical deforestation fires originate from the burning of high loads of woody biomass and coarse woody debris. The high fuel moisture content causes higher emission factors of CO in tropical forests than in savannah fires and hence higher absolute emissions of CO. Our new model approaches and satellite products allow to provide an integrated assessments on the effects of fuel and fire behaviour on fire emissions.

How to cite: Forkel, M., Andela, N., Huijnen, V., Wessollek, C., Awotwi, A., Kinalczyk, D., Marrs, C., and de Laat, J.: Effects of land use, fuel loads and fuel moisture on fire intensity and fire emissions in South America derived by reconciling bottom-up and top-down satellite observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11297, https://doi.org/10.5194/egusphere-egu23-11297, 2023.

Wildfire risk prediction relies on the often-heuristic assessment of diverse fire potential indices, fuel maps, fire weather indices and prior fire activity data. Here we present a model nowcasting daily wildfire genesis probability and expected wildfire sizes in the contiguous US.

Predictors were selected and developed to account for climate, vegetation, topographic and human effects on wildfire genesis. Climate factors are represented by multiple fuel wetting and drying processes at daily to seasonal-scale antecedences, snowpack, and wind. We use GPP to predict fuel mass and recent growth, and dominant vegetation type. Human factors include population, landscape accessibility and ignition sources such as powerlines.

The first stage of the model predicts wildfire genesis probability as a zero-inflated process with an explicit probability of fire preclusion, whilst the second stage models fire sizes according to a generalised extreme value distribution. Nonlinear effects are accounted for via global optimisation for the domain for which each variable drives changes in fire genesis behaviour and the appropriate variable transform.

The model has good predictive and explanatory power, as shown by various performance metrics and the meaningful nonlinear relationships identified in the optimisation process. We show that this method can resolve seasonal wildfire risk dynamics well over smaller ecoregions than the observational record permits, allowing us to quantify the extent to which fire risk is determined by seasonal-scale versus daily-scale effects.

How to cite: Keeping, T., Harrison, S., and Prentice, I.: A New Method for Nowcasting Wildfire Risk, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7937, https://doi.org/10.5194/egusphere-egu23-7937, 2023.

The assessment of global burned area from remote sensing is an essential climate variable driving land surface GHG emissions and energy/water budget. Gridded 0.25° or 0.5° monthly burned area have been largely used for biosphere/atmosphere interactions modelling, while recent fire/weather analysis or model developments increasingly request fire events, defined as a fire patch with intrinsic fire spread properties. Pixel level information, the finest resolution from global burned area, defined by their burn date, can be aggregated within a spatio-temporal threshold and delineate these fire events. Uncertainties in burn date, the coarse resolution of pixel resolution, multiple ignition points, or the specified values in spatio-temporal thresholds can however lead to various final fire event delineation. Currently, three major global fire event database exist (FRY, Fire Atlas, GlobFire), mostly derived from MCD64A1 pixel level 500m-resolution burned area. We propose here a new version of FRY, based on MCD64A1 and FireCCI51 at 250m, with an updated pixel aggregation method allowing for single ignition fire patches. Fire patch morphology indicators as elongation, direction, complexity have been conserved from v1.0, with additional information as ignition points from minimum burn date from burned area and more timely-accurate hotspots (VIIRS and MCD14ML), rate of spread, fire Radiative power and burn severity, as well as fraction of land cover affected, based on user requirements. The dataset is delivered as a yearly shapefile, with an attribute table referencing all information on ignition, spread and final shape. Global comparison of major information from FRYv2.0 (fire size distribution, fire number, ROS) will illustrate the effects of increasing spatial resolution and better timing from hotspots provided in this new version, freely available for the scientific community for the period 2001-2020.

How to cite: Mouillot, F., Chen, W., Campagnolo, M., and Ciais, P.: FRYv2.0 : a global fire patch morphology database from FireCCI51 and MCD64A1, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9575, https://doi.org/10.5194/egusphere-egu23-9575, 2023.

The Fire Weather Index (FWI) is used worldwide to estimate the danger of wildfires. The FWI system integrates meteorological parameters and empirically combines them into several moisture codes, each representing a different fuel type. These moisture codes are then used in combination with wind speed to estimate a fire danger. Originally, the FWI system was developed for a standard jack pine forest, however, it is widely used by fire managers to assess the fire danger in different environments as well. Furthermore, it is often also used to assess the vulnerability of organic soils, such as peatlands, to ignition and depth of burn. The utility of which is often questioned.

This research aims at improving the original FWI for northern peatlands by replacing parts of the original, purely weather-based FWI system with satellite-informed model estimates of peat moisture and water level. These come from a data assimilation output combining the NASA catchment model, including the peat modules PEATCLSM, and Soil Moisture and Ocean Salinity (SMOS) L-band brightness temperature observations. The predictive power of the new, peat-specific FWI (PEAT-FWI) is evaluated against the original FWI against fire data of the global fire atlas from 2010 through 2018 over the major northern peatlands areas. For the evaluation, the fires are split up in early and late season fires, as it is hypothesized that late fires are more hydrological driven, and the predictive power of the PEAT-FWI will thus differ between the two types of fires. Our results indeed indicate that the PEAT-FWI improves the predictive capability of estimating fire risk over northern peatlands in particular for late fires. By using a receiver operating characteristics (ROC) curve to evaluate the predictive power of the FWI against a random estimate, the area under the curve increases by up to 10% for the PEAT-FWI compared to the original FWI. The recent version 7 release of the operational Soil Moisture Active Passive (SMAP) Level-4 Soil Moisture Data Assimilation Product now includes PEATCLSM, thus, the proposed PEAT-FWI is straightforward to include in operational FWI products.

How to cite: Mortelmans, J., Felsberg, A., De Lannoy, G., Veraverbeke, S., Field, R., Andela, N., and Bechtold, M.: PEAT-FWI: Improving the Fire Weather Index for peatlands with Hydrological Modeling and L-band Microwave Observations, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3310, https://doi.org/10.5194/egusphere-egu23-3310, 2023.

Boreal forests store about one third of the world’s forest carbon and may store even more carbon in the future because of the positive effects of rising atmospheric CO₂ concentrations on photosynthesis and plant growth. However, fire frequency and severity have also been increasing in boreal forests in the last decades, which might offset their carbon sink potential. In Eastern Siberia, the dry and hot summers of 2020 and 2021 showed exceptionally high fire activity. However, even large fires that can spread for several months, eventually come to an end. This can be because of a change in the weather or because fires run out of fuels. Here, we aim to quantify the controls of fire growth in Eastern Siberia using high resolution landscape variables and hourly ERA-5 meteorological variables. We harmonized the burned area product from the Fire Climate Change Initiative and active fire product from the Visible Infrared Imaging Radiometer Suite, and derived fire perimeters from them for the period between 2012 and 2021. Along these fire perimeters, we then identified spatial changes in landscape variables (i.e. a decline in tree cover or increase in surface water) and temporal changes in hourly vapor pressure deficit and wind. By doing so, we could attribute causes of why fires stopped spreading.

How to cite: Janssen, T. and Veraverbeke, S.: Identifying the limits to fire growth in Eastern Siberia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11559, https://doi.org/10.5194/egusphere-egu23-11559, 2023.

Tropospheric ozone (O₃) is a key greenhouse gas and pollutant that is receiving increasing attention globally.  While there are many sources of tropospheric O₃, precursors from human activity (Anthro) and open biomass burning (BB) are the only ones that can be controlled. As such, it is crucial for policymakers to understand the relative contributions of the two. However, determining the contribution of O₃ can be challenging as it cannot be directly observed. It must be calculated by chemical transportation model (CTM) simulation which could be biased for unreal emission inventory, or estimated by real observations that assumes too simple chemical and transportation processes.

In this paper, we propose a solution by developing a deep learning (DL) model that combines both CTM simulations and observations. The DL model is able to learn a generalized relationship between unobservable O₃ contribution from Anthro or BB sectors and observable mixing ratio of tracers simulated by CTM with full chemistry and transportation processes. The DL model then, when applied to observed tracers, could avoid the bias from model to provide an accurate estimation of the contributions in reality.

Our results indicate the contribution from BB to tropospheric remote ozone mixing ratio is no larger than that from Anthro emission from a global perspective, even when uncertainties are deliberately tuned to bias BB. Therefore, the reduction of anthropogenic emissions should be the top priority for controlling global background O₃ levels, at least for the time period of 2016-2018 studied.

How to cite: Ma, C., Cheng, Y., and Su, H.: Biomass Burning Contributes Less to Remote Tropospheric Ozone than Human Activity, Indicated by a Deep Learning Approach, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13307, https://doi.org/10.5194/egusphere-egu23-13307, 2023.

Roughly half of global fire emissions originate from savannas, and emission factors (EF) are used to quantify the amount of trace gases and aerosols emitted per unit dry matter burned. It is well known that these EFs vary substantially even within a single biome but so far quantifying their dynamics has been hampered by a lack of EF measurements. Therefore, global emission inventories currently use a static averaged EF for the entire savanna biome. To increase the spatiotemporal coverage of EF measurements, we collected over 4500 EF bag measurements of CO₂, CO, CH₄ and N₂O using an unmanned aerial system (UAS) and measured fuel parameters and fire severity proxies during 129 individual landscape fires. These measurements spanned various widespread savanna ecosystems in Africa, South America and Australia, with early and late dry season campaigns. We trained random forest (RF) regressors to estimate daily dynamic EFs for CO₂, CO, CH₄ and N₂O at 500×500-meter resolution based on satellite and reanalysis data. The RF models reduced the difference between measured and modelled EFs by 60-85% compared to static biome averages. The introduction of EF dynamics resulted in a spatial redistribution of CO, CH₄ and N₂O emissions compared to the Global Fire Emissions Database version 4 (GFED4s) with higher emissions in higher rainfall savanna regions. While the impact from using dynamic EFs on the global annual emission estimates from savannas was relatively modest (+2% CO, -5% CH₄ and -18% N₂O), the impact on local EFs may exceed 60% under dry seasonal conditions.

How to cite: Vernooij, R., Eames, T., Russel-Smith, J., Yates, C., Beatty, R., Evans, J., Edwards, A., Ribeiro, N., wooster, M., Strydom, T., Giongo, M., Borges, M., Barradas, C., Menezes, M., van Wees, D., and van der Werf, G.: Drivers of spatial and temporal variability in savanna fire emission factors, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1975, https://doi.org/10.5194/egusphere-egu23-1975, 2023.

Wildfire is a global scale ecosystem phenomenon with substantial impact on the carbon cycle, climate warming, and ecosystem resilience. Fire and the hydrological cycle are strongly interlinked, with water availability determining the amount and combustibility of fuel, and fire influencing infiltration, runoff rates and evapotranspiration. Consequently, understanding soil moisture (SM) and vegetation water content (VWC) dynamics pre- and post-fire is fundamental for predicting fire occurrence, fire severity, and ecosystem recovery. Fire can modulate SM and VWC dynamics by influencing interception of rainfall, soil porosity, plant water uptake, and runoff; however, much evidence for fire effects on the hydrological cycle is obtained at the field- to watershed-scale. Therefore, we ask the following research question: What are the effects of large-scale fire events on SM and VWC dynamics across biomes globally?

Here we use over six years of global SM, VWC and vapor pressure deficit (VPD) derived from different remote sensing datasets to investigate the effects of large-scale fires on SM and VWC dynamics. We apply a dry down framework, only analyzing consecutive observations of decreasing soil moisture, to describe post-fire response rates for SM, VWC and VPD relative to a pre-fire reference state.

We find large scale evidence that the post-fire rate of change of SM over time is more negative, indicating faster water loss. Vegetation recovery, indicated by a positive change in VWC over time, exceeds the pre-fire reference state, which suggests that post-fire recovery is predominantly faster than undisturbed seasonal vegetation growth, likely due to succession of fast-growing plant species. Furthermore, fire affects ecosystem hydrology on shorter timescales as well, reducing diurnal VWC variation over a wide range of SM and VWC conditions. Our findings confirm several trends previously only observed at smaller scales and suggest global remote sensing of SM and VWC can substantially contribute to understanding the dynamics of post-fire plant and soil water status.

How to cite: Baur, M. J., Friend, A. D., and Pellegrini, A. F. A.: Large-scale fire events substantially impact plant-soil water relations across ecosystem types, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1406, https://doi.org/10.5194/egusphere-egu23-1406, 2023.

Fire is an integral component of ecological dynamics, playing an important role in biome distribution and biomass variability. Nonetheless, fires can also pose a  threat to both ecosystems and humans, by imposing severe economic and social consequences, and potentially contributing to biodiversity loss, carbon loss and soil erosion, whose effects can last from months to years.

The Mediterranean basin is a fire-prone region where vegetation is in general well adapted to fire, with several species showing resistance to fire itself or being able to recover quickly following fire events. However, as a consequence of climate change, more intense and frequent summer hot and dry conditions are expected to occur, which can promote more frequent and severe wildfires, with return periods potentially outpacing recovery times. Understanding recovery dynamics is therefore crucial to assess the impact of changing fire regimes in ecological dynamics and stability of ecosystems. 

In our study, we use the “Enhanced Vegetation Index” (EVI), remotely-sensed by MODIS sensor with a temporal span of 22 years, to evaluate vegetation dynamics before, during and following large fire seasons. We use a mono-parametric recovery model to assess recovery times in different burn scars across the Mediterranean basin, covering different fire regimes and land cover types. We find a tendency for slower recovery in areas that burned more often, which may indicate a decrease in ecosystems’ resilience in the past 22 years.

This study was performed under the frameworks of the 2021 FirEUrisk project (funded by European Union’s Horizon 2020 research and innovation programme under the Grant Agreement no. 101003890) and of the PhD MIT Portugal MPP2030-FCT programme (Grant no.22405886350).

How to cite: Ermitão, T., Gouveia, C., Bastos, A., and Russo, A.: Assessing changes in post-fire vegetation resilience in Mediterranean basin over the past 22 years, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-412, https://doi.org/10.5194/egusphere-egu23-412, 2023.

Advances in wildfire modeling have focused on refining atmospheric interactions for obvious links between local airflows, combustion dynamics, fire line advance and smoke plume transport. Yet, lasting impacts of wildfires on landscapes are linked primarily with changes in soil characteristics and alteration of ecological and hydrologic processes. Quantitative assessment of wildfire impacts requires metrics for fire-surface thermal interactions beyond qualitative surrogates such as burn severity used for ecological assessment. The highly transient and localized nature of wildfire intensity and its coarse spatial and temporal representation hinder quantitative translation of wildfire dynamics to soil heat fluxes even with the most advanced wildfire models (e.g., QuicFire, WRF-Fire, WFDS). Inspired by the pioneering works of Byram, Rothermel and Albini, we seek to derive high resolution information on fire line intensities from highly resolved fuel maps informed by fire line dynamics derived from numerical wildfire model representation. This hybrid downscaling approach (limited by the quality and resolution of fuel maps) offers a means for constraining soil surface heat fluxes at resolutions relevant to quantifying critical temperatures and duration at depth to estimate pyrolysis of soil organic carbon and the degree of soil structure alteration. Examples will be presented and discussed. 

How to cite: Or, D., Vahdat-Aboueshagh, H., Furtak-Cole, E., and A. McKenna, S.: Towards mechanistic representation of wildfire effects on soil – downscaling to quantify subsurface heat fluxes, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10389, https://doi.org/10.5194/egusphere-egu23-10389, 2023.

Wildfires burn on average 448 million hectares globally every year, releasing around 2.2 Pg of carbon (C) into the atmosphere [1, 2]. The net effect of wildfires in the C cycle goes, however, beyond emissions and involves many other interacting processes. Among those, there is a significant knowledge gap on the role of post-fire soil organic carbon (SOC) erosion as a carbon sink mechanism.

Post-fire erosive response is greatly enhanced by the direct and indirect effects of wildfires on soil and vegetation, such as the loss of protective cover and soil structure or the development of a water-repellent layer [3]. In addition, biomass and soil organic matter undergo quantitative and qualitative changes during wildfires, such as the formation of pyrogenic carbon, highly resistant to degradation. The resulting PyC and non-PyC carbon fractions, with contrasting physical properties and chemical stability, will be differently redistributed and mineralized during the erosion process [4]. Ultimately, post-fire SOC erosion will act as a carbon sink when the post-fire burial and stabilization of eroded carbon, together with the recovery of net primary production and soil organic carbon content, exceed the SOC losses during its post-fire transport [5]. All these processes have been scarcely investigated and poorly quantified to the date. In this presentation, we will provide new insights into this potential C sink mechanism, critically reviewing the state of the art and highlighting key research gaps.

References

[1] Boschetti et al., 2021. Global Wildfire Information System (GWIS). https://gwis.jrc.ec.europa.eu/apps/country.profile/downloads

[2] Randerson et al., 2012. J Geophys Res. https://doi.org/10.1029/2012JG002128

[3] Shakesby & Doerr, 2006. Earth-Sci Revs. https://doi.org/10.1016/j.earscirev.2005.10.006

[4] Doetterl et al., 2016. Earth-Sci Revs. https://doi.org/10.1016/j.earscirev.2015.12.005

[5] Santín et al., 2015. Glob Change Biol. https://doi.org/10.1111/gcb.12800

How to cite: Girona-García, A., Santín, C., Vieira, D., and Doerr, S.: Which is the role of post-fire SOC erosion in the C cycle?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5803, https://doi.org/10.5194/egusphere-egu23-5803, 2023.

Fire is a major disturbance in the boreal forests of the high northern latitude. Fire extent and severity have been increasing in recent decades, and the occurrence of overwintering ‘zombie’ fires has been linked to recent fire extremes. Overwintering fires are fires which were seemingly extinguished at the end of the boreal fire season yet smolder during winter to re-emerge as a flaming fire in the subsequent spring. So far, overwintering fires have only been investigated using satellite imagery. Here, for the first time, we show preliminary results from a field campaign that measured in situ impacts of fires that overwintered from 2014 to 2015 in the Canadian Northwest Territories. We measured among other the burn depth in organic soils, and characterized micro-topography. We also qualitatively assessed how fires may have overwintered. We compared nine overwintering fire sites, which burned during both 2014 and 2015, with six sites that only burned in 2014 and five nearby unburned sites. The average burn depth (±SD) of the overwintering fires was 6.8 ± 1.6 cm and significantly deeper compared to 6.1 ± 1.2 cm in the single fire sites (P < 0.01). Somewhat surprisingly, the majority of overwintering fires occurred in mesic sites with large productive trees. Only two overwintering sites were sampled in mesic-subhygric to subhygric sites dominated by black spruce (Picea mariana). The unburned control sites often featured a micro-topography of hummocks and hollows. This micro-topography was leveled in overwintering fires sites because of severe burning in organic soils. In overwintering sites, most of the organic layer was consumed. This may have led to prolonged smoldering in the root systems of trees. Our results are the first to quantify the burn depth of overwintering fires, and also show that overwintering does not only happen through deep smoldering in organic soils, yet can also occur from smoldering in tree boles and root systems of burned and fallen trees.

How to cite: Hessilt, T. D., Veraverbeke, S., Ogden, E., Paul, J., Turetsky, M., van Gerrevink, M., Alfaro-Sanchez, R., Melnik, O., Scholten, R. C., and Baltzer, J.: First results of a field campaign focused on overwintering zombie fires, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17450, https://doi.org/10.5194/egusphere-egu23-17450, 2023.

An increase in fire-prone conditions in non-fire adapted regions is rooted in climatic and anthropogenic changes. Such pyrogeographical shifts are observable, for example, in alpine regions. In 2021, Austria, experienced a fire larger than 100 ha for the first time in a century in the Schneeberg-Rax mountain region. In depth understanding of post-fire effects on carbon cycling at such non-fire adapted sites is still scarce. To help close this knowledge gap, post-fire changes were investigated at the abovementioned site, including soil organic matter composition and soil chemical conditions. 

Samples were taken immediately after the fire, 3 months, 6 months and 12 months thereafter from four sampling sites. Selected sites consisted of 1. a pine forest affected by a crown fire, 2. a pine and beech mixed forest affected by a surface fire, and two non-fire affected controls with similar site conditions (vegetation, slope, altitude, and exposition). Samples were analyzed for pH, carbon content, elemental composition, leachable dissolved organic carbon and trace elements, organic matter composition, and environmentally persistent free radical concentrations. 

pH increased after the fire at both sites investigated. This increase was the strongest (up to 1.5 units) immediately after the fire but was still substantial 1 year after the fire. Carbon contents decreased approximately 2fold in the crown fire affected soil compared to the control soil, but remained similar between surface fire affected soil and the respective control. However, aromaticity of bulk carbon and the leachable fraction increased in both fire-affected soils, which can be related to the formation of pyrogenic carbon during the fire. Pyrogenic carbon is a highly aromatic and recalcitrant carbon pool produced during incomplete combustion of biomass. Pyrogenic carbon can also contain substantial amounts of environmentally persistent free radicals (EPFR), which can form reactive oxygen species, which can induce oxidative stress on microbiota. Our EPFR measurements showed an increase by at least 1.5 orders of magnitude of EPFR in fire affected soils. This study suggests that changes in soil carbon cycling can be expected following fires in non-adapted alpine forests. 

How to cite: Torres, M., Poyntner, C., Chaudhuri, S., Pignitter, M., Schmidt, H., Hofmann, T., and Sigmund, G.: Fire impacts on soil carbon in a non-fire adapted alpine forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2233, https://doi.org/10.5194/egusphere-egu23-2233, 2023.

Background:

Fires burn roughly 3% of Earth’s land surface each year and are predicted to become more frequent and severe as human-caused climate change progresses. Fires can drive ecosystem N loss by volatilizing N bound in plant biomass to the atmosphere and by leaving behind ash rich in ammonium (NH₄⁺) and organic N that can run off when it rains. While N volatilization and runoff account for a large fraction of N loss after fires, budget imbalances suggest soil emissions of nitric oxide (NO) and nitrous oxide (N₂O) may also be significant N loss pathways after fire. Identifying sources of NO and N₂O is important because NO is a precursor for tropospheric O₃ which causes high rates of asthma hospitalizations,and N₂O is a powerful greenhouse gas with 300× the warming potential of CO₂. Soil emissions of NO and N₂O are largely governed by the microbial processes of nitrification and denitrification. Under aerobic conditions typical of dry soils, nitrifying organisms such as ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) oxidize NH₄⁺ to nitrate (NO₃^-) and release NO and N₂O as byproducts. AOA and AOB process N with different efficiencies, suggesting shifts in AOA:AOB ratios may change N emissions. Specifically, AOB are dominant in soils with high NH₄⁺and pH and produce higher NO and N₂O emissions. Since such soil conditions are frequently observed after fires, we hypothesize NO and N₂O emissions will increase as AOB communities become dominant. To test this, we collected soil cores from 5 plots in the Sequoia National Park, CA over a time series starting two weeks after a high severity chaparral fire. We selectively inhibited AOA and AOB communities to measure their contributions to NO and N₂O emissions. We also measured the isotopic composition of N₂O emissions from these soils using an LGR isotopic N₂O analyzer to better understand the processes responsible for post-fire N₂O production.

Results/Conclusions

One month after the fire, soil bulk emissions of NO over 72hrs were 1.5 times higher in the burned plots (101.4 ± 22.4 µg N-NO/g soil burned; 67.1 ± 19.3 µg N-NO/g soil unburned; ±SE). Bulk soil emissions of N₂O over 72hrs were 7.5 times lower in burned plots compared to before the fire (0.0616 ± 0.04 ng N-N₂O/g soil burned; 0.463 ± 0.19 ng N-N₂O/g soil unburned; ±SE). Although the effects of fire on nitrifier communities were not significant at one month post-fire (Control: p=0.14, AOA: p=0.09, AOB: p=0.162), both AOA and AOB contributions to NO emissions increased in response to fire. Results for nitrifier contributions to N₂O emissions were highly variable and non-significant with no clear trends as all N₂O emissions were near zero. Further analysis over the time series may yield clearer results as microbial communities have more time to recover. Pairing these data with isotopic information (in progress) may yield one of the most in-depth understandings of post-fire NO and N₂O emissions to date.

How to cite: Stephens, E., Greene, A., Krichels, A., and Homyak, P.: Wildfires alter nitrifier communities and increase soil emissions of NOx but not N2O in California chaparral, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3695, https://doi.org/10.5194/egusphere-egu23-3695, 2023.

During the last decade, the world faced record-breaking giant fires as observed in Australia and California, a trend that is expected to increase in the forthcoming years due to climate change (Palinkas, 2020; Sharples et al., 2016; van Oldenborgh et al., 2021). In addition to their large ecological impacts, wildfires are more and more regarded for their potential threat to human health through air pollution (Xu et al., 2020). However, water pollution resulting from wildfires represents an underestimated pathway for wildfires-induced health risk (Abraham et al., 2017). This latter impact is related to the heat generated by wildfires that can propagate towards several centimeters in the soil and transform/destroy soil components. In addition to weakening soil physical stability, such transformation/destruction can change the speciation of potentially toxic elements (PTEs) that are associated with these soil components, leading to enhanced mobility towards waterways (Abraham et al., 2017; Terzano et al., 2021). One notable PTE is chromium, which is naturally present in soils mostly as trivalent Cr(III), but can represent an environmental and health issue when occurring as hexavalent Cr(VI). Recent studies reported Cr(III) oxidation to Cr(VI) upon laboratory-heating of Cr(III)-doped Fe-oxyhydroxides (Burton et al., 2019a; 2019b). Besides, Cr(III) oxidation to Cr(VI) upon controlled heating was also demonstrated for different types of soils (Burton et al., 2019b; Rascio et al., 2022; Thery et al., 2023). All these considerations suggest a significant effect of wildfires on Cr(III) oxidation to Cr(VI) in soils, with a possible influence on Cr mobility that could further impact freshwater quality. This risk of freshwater Cr(VI) pollution is expected to particularly concern ultramafic catchments because of the related occurrence of Cr-rich soils.

We have tried to address this question by performing laboratory-heating of several soils types (Ferralsols, Cambisols and Vertisols) developed on various geological settings (ultramafic, mafic and volcano-sedimentary) in New Caledonia, a French overseas territory which is a good representative of wildfires-threatened tropical ultramafic catchments (Toussaint, 2020). The results obtained revealed a significant influence of soil heating on Cr(III) oxidation to Cr(VI), followed by an enhanced Cr(VI) mobility, in all soil types. However, the magnitude of Cr(III) to Cr(VI) oxidation and Cr mobility depended on the actual nature of the soil, Ferralsols showing the highest Cr(VI) release compared to Cambisols and Vertisols. These differences were further interpreted on the basis of the changes in Cr speciation (including redox) induced by laboratory-heating of the investigated soils, as revealed by synchrotron-based X-ray absorption spectroscopy analyses. Finally, a simple risk assessment relying on the hypothesized concentration of suspended particulate matter (SPM) issued from burned soils in the related waterways allowed to emphasize a risk of wildfires-induced freshwater Cr(VI) pollution for ultramafic catchments composed of Ferralsols (Thery et al., 2023). Beyond the single case of New Caledonia, the results of this study point to the need to foster collaborative studies in order to further evaluate this risk of wildfires-induced freshwater Cr(VI) pollution at tropical ultramafic catchments on a global scale.

How to cite: Juillot, F., Thery, G., Quantin, C., Bollaert, Q., Meyer, M., Quiniou, T., Jourand, P., Ducousso, M., Fritsch, E., and Morin, G.: Wildfires, chromium and freshwater quality at tropical ultramafic catchments : A prospective study on laboratory-heated soils from New Caledonia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13941, https://doi.org/10.5194/egusphere-egu23-13941, 2023.

Within the framework of the project IMPOSE (Emit now, mitigate later? IMPlications of temperature OverShoots for the Earth system) six idealized emission-overshoot simulations have been performed with the Earth System Model NorESM2-LM2 and used as forcing for the 2^nd generation dynamic global vegetation model LPJ-GUESS with its fire-model SIMFIRE-BLAZE to investigate the impact of different CO₂ overshoots on global wildfire regimes.

The simulations describe a set of scenarios with high, medium, and low accumulative CO₂ emissions and each of which has a short (immediate) and a long (100 years) peak of accumulative CO₂ emissions before declining towards a baseline simulation of 1500 PgC accumulatively emitted within the first 100 years.

The results show that the height of the overshoot has an impact on global fire regimes while its duration does not seem to play a significant role 200 years after peak CO₂. Overall, we can see that changes in vegetation composition following the temperature anomaly are the main driver for changes in global wildfire frequency. While in the low overshoot scenarios burnt area has almost converged towards the baseline simulation, the extremest scenarios show the lowest burnt area at the end of the simulation period, indicating that vegetation changes, especially in low latitudes, have been most significant and/or are still ongoing.

How to cite: Nieradzik, L., Lee, H., Miller, P., Schwinger, J., and Wårlind, D.: Changes in global fire regimes under idealized overshoot scenarios, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7379, https://doi.org/10.5194/egusphere-egu23-7379, 2023.

Lightning is an important atmospheric process for igniting forest fires – often in remote locations where they are not easily suppressed – which results in potentially large emissions of many pollutants and short-lived climate forcers. Lightning also generates reactive nitrogen, resulting in the production of tropospheric ozone, the third most important greenhouse gas. Furthermore, the changing climate is expected to change the frequency and location of lightning. As such, lightning is an important component of climate models. The Canadian Atmospheric Model, CanAM, is one such climate model that did not contain an 'online' lightning parameterization. Fire ignition in CanAM was done via an unchanging climatological lightning input. In this study, we have added a new logistical regression lightning model (Etten-Bohm et al, 2021) into CanAM, creating the capacity for future lightning predictions with CanAM under different climate scenarios. The modelled lightning and fire area burned were evaluated against measurements in a historical period with good results. Then we simulate lightning and fire area burned in a future climate scenario in order to provide an estimate on how lightning and its impacts will change in the future. This study also presents the first time that CanAM’s land fire model was used online with its atmosphere to fully simulate fires in the global earth system.

Reference:

Etten-Bohm, M., J. Yang, C. Schumacher, and M. Jun : Evaluating the relationship between lightning and the large-scale environment and its use for lightning prediction in global climate models, JGR-atmospheres, 126, e2020JD033990, 2021.

How to cite: Whaley, C., Schumacher, C., Etten-Bohm, M., Arora, V., Plummer, D., Cole, J., Lazare, M., and Akingunola, A.: Lightning in a changing climate and its impacts on fire area burned, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9791, https://doi.org/10.5194/egusphere-egu23-9791, 2023.

Fire-enabled dynamic global vegetation models (DGVMs) can be used to study how fire activity responds to its main drivers, including climate/weather, vegetation and human activities, at coarse spatial scales. Such models can also be used to examine the effects of fire on vegetation, and, when embedded in Earth system models, investigate the feedback of fire on the climate system. Thus they are valuable tools for studying wildfires. Accordingly, the Fire Model Intercomparison Project (FireMIP) was established to evaluate and utilise these models using consistent protocols.

Here we present the second round of FireMIP simulations to focus historic wildfire drivers (1901 to present). A six-member ensemble of simulations from fire-enabled DGVMs was compared to remotely-sensed burnt area observations and to the previous round of historical FireMIP simulations. We found that the model skill when simulating spatial patterns of burnt area shows modest improvements compared to the previous FireMIP round, and that the simulations mostly reproduce the decreasing trend in global burnt area found over the last two decades. However, whilst the broad global patterns are reasonable, there are considerable discrepancies with regards to regional agreement and timing of burnt area. Furthermore, the models show diverging trends in the pre-satellite era.

To investigate further and inform future model development, we explored the residuals between simulated burnt area from the FireMIP models and remotely-sensed burnt area as a function of climate, vegetation, anthropogenic and topographic variables using generalised additive models (GAMs). We found some common responses across the models, with many over-predicting fire activity in arid/low productivity areas and all models under-predicting at low road density. However, with respect to other variables, such as wind speed and cropland fraction, the models residuals showed divergent responses. It is anticipated that these results should aid further development of global fire models in terms of driving variables, process representations and model structure.

How to cite: Forrest, M., Burton, C., Drüke, M., Hantson, S., Li, F., Melton, J., Nieradzik, L., Rabin, S., Sitch, S., Yue, C., and Hickler, T.: Causes of uncertainty in simulated burnt area by fire-enabled DGVMs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12604, https://doi.org/10.5194/egusphere-egu23-12604, 2023.

Climate change is expected to cause prolonged and more severe droughts in Europe, increasing landscape fire occurrence. Since The Netherlands has a high population density in areas typified as ‘Wildland-Urban Interface’, a genuine risk for Dutch society arises. Landscape management, such as prescribed burning, can reduce fire risk. Prescribed burning is executed by intentionally burning the low and understory vegetation, limiting fuel for a landscape fire, under controlled conditions. In this interdisciplinary research, conducted by a team of (early career) researchers from climate science, cultural studies, hydrology, mathematics and spatial economics, we aim to assess whether prescribed burning can be used in The Netherlands as a fire risk reduction tool in natural areas with a high fire risk.

The Netherlands has a well-developed flood management system. However, it lacks such holistic approaches to landscape fire management. Landscape managers and researchers can learn from Dutch flood management by applying the secondary objective, improvement of spatial quality, to prescribed burning. In this research we assess the potential for improving spatial quality through prescribed burning, by adapting the spatial quality framework of the Dutch Room for the River project. Our framework looks at the three pillars burning effectiveness, ecological robustness, and cultural meaning at the potential prescribed burning sites. Burning effectiveness is highest in natural areas (Natura 2000 sites), with high fire risk and the presence of low vegetation. Ecological robustness measures the disturbance prescribed burning could cause in a landscape. Disturbance depends on the burning frequency and intensity, as well as on the type of vegetation that is burned and the usage of the area. In groundwater protection areas, seepage of harmful elements could cause more disturbance. These areas are therefore excluded from the analysis. From the perspective of cultural meaning, social perceptions influence the measure’s performance. Cultural significance and landscape identification provide various perspectives on fires and prescribed burning. Categorizing the different levels of engagement, based on an engagement pyramid, can deliver a basis for implementing prescribed burning.

Preliminary analyses result in a selection of 15 Natura 2000 sites in The Netherlands where prescribed burning could be feasible, varying from the Voornes Duin (14 km²) to the Veluwe (885 km²). These areas are mostly vegetated with coniferous and mixed forests. Prescribed burning potentially causes more disturbance in grasslands. However, since none of the 15 areas contain more than 24% grassland, prescribed burning could still be feasible at all locations. In the area of the Veluwe, qualitative interviews with the local population indicate support for fire management, such as prescribed burning, as they are aware of the risks imposed by landscape fires.

The final research results can contribute to the improvement of fire management in both The Netherlands and other North-Western European countries with similar vegetation and climate change effects.

How to cite: van Manen, N., Buxó, A., Egberts, L., Houwaard, L., Jacobsen, L., Keesom, J., Reijners, M., van Slooten, D., Teunisse, A., and van Tilburg, A.: Assessing the feasibility of prescribed burning as a fire risk reduction tool for The Netherlands, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11992, https://doi.org/10.5194/egusphere-egu23-11992, 2023.

Agricultural expansion and ongoing climate change are rapidly altering the fire regime of natural ecosystems along the Cerrado-Amazon biome boundary. While agricultural intensification has driven a decrease in fire ignitions in some regions, agricultural expansion has increased fire usage in other landscapes for deforestation and managing pasturelands. These contrasting patterns of fire activity across different land-use frontiers limits our ability to accurately predict where and when fires may occur, particularly under the context of climate change.

To predict fire activity with land-use transitions, we modelled fire probability as a function of the age of different land-use transitions across the Amazon and Cerrado. We investigated annual land-use and associated burned areas based on the MapBiomas Collection 6.0 and MapBiomas Fire Collection 1.0 data, respectively, from 1986 to 2020. This allowed us to quantify how the time-since conversion of native vegetation (forest, savanna, and grassland) to pasture and farming influence fire occurrence. Additionally, we explored the joint impact of land-use change and climate extremes in fire activity in terms of estimated vapor pressure deficit (VPD) and maximum cumulative water deficit (MCWD), two common measures of flammability and drought impact. 

Our results confirm that transition age is a strong predictor of fire probability. They also suggest that fire probability increases (decreases) at different rates before (after) clearing in Amazon and Cerrado. The role of climate extremes in modulating burning activity associated with land-use transitions varied by biome, post-fire land use, and the size of the burned area associated with the conversion. These findings provide insight into incorporating the effect of land-use transition age on ignition probability for fire modelling in combination with climate drivers. From an operational point of view, our results aim to contribute to environmental policies capable of sustaining ecosystem integrity at the ecotone between the Amazon and Cerrado biomes.

How to cite: Ribeiro, A. F. S., Santos, L., Uribe, M. R., Silvestrini, R. A., Rattis, L., Macedo, M. N., Morton, D. C., Randerson, J. T., Seneviratne, S. I., Zscheischler, J., and Brando, P. M.: How changes in ignition sources influence fire probability in the Amazon and Cerrado biomes: a perspective based on frontier age, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3332, https://doi.org/10.5194/egusphere-egu23-3332, 2023.