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Defining pyromes and global syndromes of fire regimes
Abstract and Figures
Fire is a ubiquitous component of the Earth system that is poorly understood. To date, a global-scale understanding of fire is largely limited to the annual extent of burning as detected by satellites. This is problematic because fire is multidimensional, and focus on a single metric belies its complexity and importance within the Earth system. To address this, we identified five key characteristics of fire regimes-size, frequency, intensity, season, and extent-and combined new and existing global datasets to represent each. We assessed how these global fire regime characteristics are related to patterns of climate, vegetation (biomes), and human activity. Cross-correlations demonstrate that only certain combinations of fire characteristics are possible, reflecting fundamental constraints in the types of fire regimes that can exist. A Bayesian clustering algorithm identified five global syndromes of fire regimes, or pyromes. Four pyromes represent distinctions between crown, litter, and grass-fueled fires, and the relationship of these to biomes and climate are not deterministic. Pyromes were partially discriminated on the basis of available moisture and rainfall seasonality. Human impacts also affected pyromes and are globally apparent as the driver of a fifth and unique pyrome that represents human-engineered modifications to fire characteristics. Differing biomes and climates may be represented within the same pyrome, implying that pathways of change in future fire regimes in response to changes in climate and human activity may be difficult to predict.
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... Traditional methods of fire monitoring, such as satellite-based approaches, have limitations in providing comprehensive data for the development of systematic methodologies to reduce the risk of fires. [1,2] In light of these challenges, the implementation of multi-agent robot systems presents a promising solution. By leveraging the capabilities of such systems, we can enhance fire detection and navigation, enabling faster response times, precise localization, and optimal path planning in dynamic environments. ...
... The template will number citations consecutively within brackets [1]. The sentence punctuation follows the bracket [2]. ...
Fire is a significant risk that can have devastating consequences, including loss of life, property damage, and environmental destruction. One way to reduce the risk of fires is through the use of fire extinguishers, which can help to cool down the heat or remove the oxygen from a fire to prevent it from continuing to burn. In this project, a multi-agent robot system consisting of two Turtlebot2 robots with the ROS was developed to autonomously locate and navigate to fire extinguishers in an unknown environment. The first robot, called Turtlebot A, moved through the environment and detected the location of the fire extinguisher, which was then defined as a goal for the second robot, called Turtlebot B. Turtlebot A also created a map of the environment using an RGB-D camera and sent it to Turtlebot B, which used it to plan a path and navigate to the fire extinguisher location while avoiding obstacles. The project demonstrated the potential of multi-agent robots to communicate with each other and work together to achieve a shared goal, as well as the capabilities of ROS for autonomous navigation and path planning
... Precipitation is likely a poor predictor of consumer dominance in high-latitude systems (e.g., boreal forests) with low potential evapotranspiration, low temperatures, and short growing seasons. In such lowenergy settings (Veldhuis et al., 2019), large herbivores may struggle to balance thermoregulatory and food requirements, while fuel continuity and density are sufficient to promote rare, intense, and large fires during hot and dry summer conditions (Archibald et al., 2013). Therefore, the Africa-based precipitation-only model likely overpredicts herbivore dominance in cold regions. ...
Large herbivores drive critical ecological processes, yet their long-term dynamics and effects are poorly understood due to the limitations of existing paleoherbivore proxies. To address these shortcomings, long-term records of paleoherbivores were constructed by (i) applying new analytical techniques to existing bison fossil datasets; and (ii) examining fecal steroid data that characterize temporal changes in ungulate abundance and community composition. These paleoherbivore reconstructions were analyzed in relation to their environmental contexts to better understand herbivore-ecosystem interactions through time in three separate studies: First, spatiotemporal changes in postglacial bison distribution and abundance in North America were examined by summarizing fossil bison observations. Bison observations were compared with simulated climate variables in a distribution modeling framework to project probable bison distributions in 1000-year intervals from the Last Glacial Maximum to present in light of changing climatic drivers over time. Since the Bolling-Allerod Interstadial (14.7-12.9 ka) the geographic distribution of bison is primarily explained by seasonal temperature patterns. Second, Holocene records of bison abundance were compared to paleofire reconstructions spanning the midcontinental moisture gradient to determine the relative dominance of herbivores and fire as biomass consumers. Bison dominated biomass consumption in dry settings whereas fire dominated consumption in wetter environments. Historical distributions of herbivory and burning resemble those of Sub-Saharan Africa, suggesting a degree of generality in the feedbacks and interactions that regulate long-term consumer dynamics. Third, the utility of fecal steroids in lake sediments for reconstructing past herbivore abundance and identity was tested by (i) characterizing the fecal steroid signatures of key North American ungulates, (ii) comparing these signatures with multiproxy data preserved in lake sediments from the Yellowstone Northern Range, and (iii) comparing influxes of fecal steroids over time to historical records of ungulate biomass and use. Bison and/or elk were abundant at Buffalo Ford Lake over the past c. 2300 years. Ungulate densities in the watershed were highest in the early 20 th century and likely contributed to decreases in forage taxa and possibly increased lake production. These results demonstrate long-term ecological impacts of herbivores and highlight opportunities for continued development of paleoherbivore proxies.
Climate change is exacerbating wildfire conditions, but evidence is lacking for global trends in extreme fire activity itself. Here we identify energetically extreme wildfire events by calculating daily clusters of summed fire radiative power using 21 years of satellite data, revealing that the frequency of extreme events (≥99.99th percentile) increased by 2.2-fold from 2003 to 2023, with the last 7 years including the 6 most extreme. Although the total area burned on Earth may be declining, our study highlights that fire behaviour is worsening in several regions—particularly the boreal and temperate conifer biomes—with substantial implications for carbon storage and human exposure to wildfire disasters.
Fire is a fundamental part of the Earth system, with impacts on vegetation structure, biomass, and community composition, the latter mediated in part via key fire-tolerance traits, such as bark thickness. Due to anthropogenic climate change and land use pressure, fire regimes are changing across the world, and fire risk has already increased across much of the tropics. Projecting the impacts of these changes at global scales requires that we capture the selective force of fire on vegetation distribution through vegetation functional traits and size structure. We have adapted the fire behavior and effects module, SPITFIRE (SPread and InTensity of FIRE), for use with the Functionally Assembled Terrestrial Ecosystem Simulator (FATES), a size-structured vegetation demographic model. We test how climate, fire regime, and fire-tolerance plant traits interact to determine the biogeography of tropical forests and grasslands. We assign different fire-tolerance strategies based on crown, leaf, and bark characteristics, which are key observed fire-tolerance traits across woody plants. For these simulations, three types of vegetation compete for resources: a fire-vulnerable tree with thin bark, a vulnerable deep crown, and fire-intolerant foliage; a fire-tolerant tree with thick bark, a thin crown, and fire-tolerant foliage; and a fire-promoting C4 grass. We explore the model sensitivity to a critical parameter governing fuel moisture and show that drier fuels promote increased burning, an expansion of area for grass and fire-tolerant trees, and a reduction of area for fire-vulnerable trees. This conversion to lower biomass or grass areas with increased fuel drying results in increased fire-burned area and its effects, which could feed back to local climate variables. Simulated size-based fire mortality for trees less than 20 cm in diameter and those with fire-vulnerable traits is higher than that for larger and/or fire-tolerant trees, in agreement with observations. Fire-disturbed forests demonstrate reasonable productivity and capture observed patterns of aboveground biomass in areas dominated by natural vegetation for the recent historical period but have a large bias in less disturbed areas. Though the model predicts a greater extent of burned fraction than observed in areas with grass dominance, the resulting biogeography of fire-tolerant, thick-bark trees and fire-vulnerable, thin-bark trees corresponds to observations across the tropics. In areas with more than 2500 mm of precipitation, simulated fire frequency and burned area are low, with fire intensities below 150 kW m−1, consistent with observed understory fire behavior across the Amazon. Areas drier than this demonstrate fire intensities consistent with those measured in savannas and grasslands, with high values up to 4000 kW m−1. The results support a positive grass–fire feedback across the region and suggest that forests which have existed without frequent burning may be vulnerable at higher fire intensities, which is of greater concern under intensifying climate and land use pressures. The ability of FATES to capture the connection between fire disturbance and plant fire-tolerance strategies in determining biogeography provides a useful tool for assessing the vulnerability and resilience of these critical carbon storage areas under changing conditions across the tropics.
Introduction
Climate change is predicted to increase the frequency of extreme single-day fire spread events, with major ecological and social implications. In contrast with well-documented spatio-temporal patterns of wildfire ignitions and perimeters, daily progression remains poorly understood across continental spatial scales, particularly for extreme single-day events (“blow ups”). Here, we characterize daily wildfire spread across North America, including occurrence of extreme single-day events, duration and seasonality of fire and extremes, and ecoregional climatic niches of fire in terms of Actual Evapotranspiration (AET) and Climatic Water Deficit (CWD) annual climate normals.
Methods
Remotely sensed daily progression of 9,636 wildfires ≥400 ha was used to characterize ecoregional patterns of fire growth, extreme single-day events, duration, and seasonality. To explore occurrence, extent, and impacts of single-day extremes among ecoregions, we considered complementary ecoregional and continental extreme thresholds (Ecoregional or Continental Mean Daily Area Burned + 2SD). Ecoregional spread rates were regressed against AET and CWD to explore climatic influence on spread.
Results
We found three-fold differences in mean Daily Area Burned among 10 North American ecoregions, ranging from 260 ha day ⁻¹ in the Marine West Coast Forests to 751 ha day ⁻¹ in Mediterranean California. Ecoregional extreme thresholds ranged from 3,829 ha day ⁻¹ to 16,626 ha day ⁻¹ , relative to a continental threshold of 7,173 ha day ⁻¹ . The ~3% of events classified as extreme cumulatively account for 16–55% of total area burned among ecoregions. We observed four-fold differences in mean fire duration, ranging from 2.7 days in the Great Plains to 10.5 days in Northwestern Forested Mountains. Regions with shorter fire durations also had greater daily area burned, suggesting a paradigm of fast-growing short-duration fires in some regions and slow-growing long-duration fires elsewhere. CWD had a weak positive relationship with spread rate and extreme thresholds, and there was no pattern for AET.
Discussion
Regions with shorter fire durations had greater daily area burned, suggesting a paradigm of fast-growing short-duration fires in some regions and slow-growing long-duration fires elsewhere. Although climatic conditions can set the stage for ignition and influence vegetation and fuels, finer-scale mechanisms likely drive variation in daily spread. Daily fire progression offers valuable insights into the regional and seasonal distributions of extreme single-day spread events, and how these events shape net fire effects.
Fire and large mammal herbivores (LMH) are the principal top‐down forces maintaining savanna structure. Nonetheless, experiments designed to investigate interactions between fire and LMH are rare in savannas, and relationships between environmental variation and biodiversity in the context of fire and LMH are poorly understood. This study addresses these gaps by manipulating the presence of LMH and early and late dry season fires in a tropical African savanna. In addition, this work simultaneously explores environmental variables including soil and foliar quality, vegetation cover, and nearby water sources to more holistically describe factors affecting savanna functioning and biodiversity. After 1 year of experimental treatments, changes in vegetation were already apparent. Shrub abundance and richness and grass richness were higher in the absence of LMH, while grass biomass increased three‐fold in burned plots as compared to unburned plots. Foliar nutrients tended to increase in open plots, while phenolics decreased. Amphibian abundance decreased with early burns and was higher with LMH. In contrast, small mammal abundance and richness increased without LMH and with time since fire. Richness and foraging of LMH were highest after late burns. These results demonstrate ecosystem‐wide effects of LMH, illustrating the importance of considering multiple taxa when designing fire management programs. For example, burning negatively affected amphibians and small mammals and changed vegetation at the same time it increased LMH foraging. In the long‐term, this experiment will shed light on interacting effects of fire and LMH on savanna biodiversity and function.
Abstract in Portuguese is available with the online material.
Fire ecology is a complex discipline that can only be understood by integrating biological, physical, and social sciences. The science of fire ecology explores wildland fire’s mechanisms and effects across all scales of time and space. However, the lack of defined, organizing concepts in fire ecology dilutes its collective impact on knowledge and management decision-making and makes the discipline vulnerable to misunderstanding and misappropriation. Fire ecology has matured as a discipline and deserves an enunciation of its unique emergent principles of organization. Most scientific disciplines have established theories, laws, and principles that have been tested, debated, and adopted by the discipline’s practitioners. Such principles reflect the consensus of current knowledge, guide methodology and interpretation, and expose knowledge gaps in a coherent and structured way. In this manuscript, we introduce five comprehensive principles to define the knowledge fire ecology has produced and provide a framework to support the continued development and impact of the fire ecology discipline.
New burned area datasets and top-down constraints from atmospheric concentration measurements of pyrogenic gases have decreased the large uncertainty in fire emissions estimates. However, significant gaps remain in our understanding of the contribution of deforestation, savanna, forest, agricultural waste, and peat fires to total global fire emissions. Here we used a revised version of the Carnegie-Ames-Stanford-Approach (CASA) biogeochemical model and improved satellite-derived estimates of area burned, fire activity, and plant productivity to calculate fire emissions for the 1997–2009 period on a 0.5° spatial resolution with a monthly time step. For November 2000 onwards, estimates were based on burned area, active fire detections, and plant productivity from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor. For the partitioning we focused on the MODIS era. We used burned area estimates based on Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner (VIRS) and Along-Track Scanning Radiometer (ATSR) active fire data prior to MODIS (1997–2000) and Advanced Very High Resolution Radiometer (AVHRR) derived estimates of plant productivity during the same period. Average global fire carbon emissions were 2.0 Pg yr<sup>−1</sup> with significant interannual variability during 1997–2001 (2.8 Pg yr<sup>−1</sup> in 1998 and 1.6 Pg yr<sup>−1</sup> in 2001). Emissions during 2002–2007 were relatively constant (around 2.1 Pg yr<sup>−1</sup>) before declining in 2008 (1.7 Pg yr<sup>−1</sup>) and 2009 (1.5 Pg yr<sup>−1</sup>) partly due to lower deforestation fire emissions in South America and tropical Asia. During 2002–2007, emissions were highly variable from year-to-year in many regions, including in boreal Asia, South America, and Indonesia, but these regional differences cancelled out at a global level. During the MODIS era (2001–2009), most fire carbon emissions were from fires in grasslands and savannas (44%) with smaller contributions from tropical deforestation and degradation fires (20%), woodland fires (mostly confined to the tropics, 16%), forest fires (mostly in the extratropics, 15%), agricultural waste burning (3%), and tropical peat fires (3%). The contribution from agricultural waste fires was likely a lower bound because our approach for measuring burned area could not detect all of these relatively small fires. For reduced trace gases such as CO and CH<sub>4</sub>, deforestation, degradation, and peat fires were more important contributors because of higher emissions of reduced trace gases per unit carbon combusted compared to savanna fires. Carbon emissions from tropical deforestation, degradation, and peatland fires were on average 0.5 Pg C yr<sup>−1</sup>. The carbon emissions from these fires may not be balanced by regrowth following fire. Our results provide the first global assessment of the contribution of different sources to total global fire emissions for the past decade, and supply the community with an improved 13-year fire emissions time series.
Here we integrate spatial information on annual burnt area, fire frequency, fire seasonality, fire radiative power and fire size distributions to produce an integrated picture of fire regimes in southern Africa. The regional patterns are related to gradients of environmental and human controls of fire, and compared with findings from other grass-fuelled fire systems on the globe. The fire regime differs across a gradient of human land use intensity, and can be explained by the differential effect of humans on ignition frequencies and fire spread. Contrary to findings in the savannas of Australia, there is no obvious increase in fire size or fire intensity from the early to the late fire season in southern Africa, presumably because patterns of fire ignition are very different. Similarly, the importance of very large fires in driving the total annual area burnt is not obvious in southern Africa. These results point to the substantial effect that human activities can have on fire in a system with high rural population densities and active fire management. Not all aspects of a fire regime are equally impacted by people: fire-return time and fire radiative power show less response to human activities than fire size and annual burned area.
Global warming is contentious and difficult to measure, even among the majority of scientists who agree that it is taking place. Will temperatures rise by 2ºC or 8ºC over the next hundred years? Will sea levels rise by 2 or 30 feet? The only way that we can accurately answer questions like these is by looking into the distant past, for a comparison with the world long before the rise of mankind. We may currently believe that atmospheric shifts, like global warming, result from our impact on the planet, but the earth's atmosphere has been dramatically shifting since its creation. This book reveals the crucial role that plants have played in determining atmospheric change - and hence the conditions on the planet we know today. Along the way a number of fascinating puzzles arise: Why did plants evolve leaves? When and how did forests once grow on Antarctica? How did prehistoric insects manage to grow so large? The answers show the extraordinary amount plants can tell us about the history of the planet -- something that has often been overlooked amongst the preoccuputations with dinosaur bones and animal fossils. David Beerling's surprising conclusions are teased out from various lines of scientific enquiry, with evidence being brought to bear from fossil plants and animals, computer models of the atmosphere, and experimental studies. Intimately bound up with the narrative describing the dynamic evolution of climate and life through Earth's history, we find Victorian fossil hunters, intrepid polar explorers and pioneering chemists, alongside wallowing hippos, belching volcanoes, and restless landmasses.
Fire is a natural environmental variable over most of Australia. It is a unique environmental variable in that it: tends to be self propagating; occurs for extremely limited periods in any one locality; may have devastating effects; occurs over a wide range of environments and plant communities.In many ecosystems fire is a normal environmental variable. Its immediate effects on vegetation depend on fire intensity but longer-term effects depend also on fire frequency and season of occurrence. Using these three variables, various fire regimes may be defined. Species may be adapted to these fire regimes but not to fire per se. Interaction between fire and an adaptive trait may facilitate survival or reproduction of a species but this effect alone does not guarantee that the species is adapted to a certain fire regime—this depends on many characteristics of the life cycle.Much of the relevant Australian literature is concerned with adaptive traits while relatively little considers adaptations of species. A knowledge of species' adaptation is necessary if we are to predict species' behaviour under various natural or imposed fire regimes.