North American grassland birds have experienced steeper population declines than any other avian guild, yet conservation efforts remain largely reactive and fragmented. We used nearly four decades of North American Breeding Bird Survey data to identify biome-scale spatial patterns (clustering) of grassland bird abundance for the Great Plains. Our results reveal an ecological core in the north-central Plains where community-level abundance is either increasing by >100% or remains high and stable, providing a strategic roadmap for a “Defend the Core” conservation approach. This approach flips the script from reactive triage centered on isolated population fragments to a proactive strategy of maintaining large-scale ecosystem integrity. Conversely, we found that population losses are more spatially clustered than wins, reflecting the relentless, one-way movement of woody encroachment and agricultural conversion. This asymmetry supports prioritizing intact landscapes, as current restoration rates are often outpaced by the scale of habitat loss. Notably, we found that community-level spatial clustering is a more robust indicator of biome condition than trends of individual flagship species, suggesting that managing for ecosystem integrity provides a more effective multi-species umbrella. Given our results, there is an opportunity for operationalizing a Great Plains Conservation Design that is ecosystem-centric and rooted in the sustainability of the private-land cattle production that maintains these open spaces. By leveraging avian abundance as a biological sensor, managers and producers can deploy a shared vision that matches the spatial scale of the threats, moving from reactive triage to proactive defense of core working grasslands in North America.

Abstract Invasive species can fundamentally alter fire regimes by modifying fuel characteristics, yet predicting their impacts on fire behavior remains challenging. Cogongrass ( Imperata cylindrica ), a highly invasive grass spreading across the southeastern US, has been associated with increased fuel loads and fire intensity, but it is unclear how its impacts on fuel load and fire behavior vary across environmental and seasonal gradients. We measured fuel characteristics across 159 cogongrass invaded and non-invaded plots spanning from central Florida to southern Mississippi across multiple seasons. Using these data, we developed custom fuel models in BehavePlus to predict cogongrass effects on surface fire behavior and tree torching across spatial and temporal gradients. Cogongrass invasion increased live fuel loads by up to 1.96 t/ha, with effects strongest in summer and at lower latitudes, and dead fuel loads by up to 1.88 t/ha across all sites. Latitude × invasion interactions indicated that fuel load differences between invaded and non-invaded plots diminished toward northern sites. Cogongrass-driven fuel load alterations elevated surface fire rate of spread (median + 0.75 m/min), and flame length (+ 0.16 m), with the largest increases observed in spring (rate of spread: + 2.60 m/min; flame length: + 0.80 m). Invasion also consistently increased the crown fire transition probability, with magnitudes mirroring those of surface fire effects. Our findings highlight the potential for cogongrass to substantially alter fire behavior across a range of environmental conditions, although the magnitude of these effects varies geographically and tends to be strongest at lower latitudes. These results underscore the importance of targeted management in regional fire planning of invaded landscapes.

Trees and shrubs are expanding into historically open ecosystems across the globe, threatening ecological function and ecosystem services. Across much of the eastern U.S., increasing woody cover has been associated with ecological degradation of forest and savanna ecosystems, and more recently, heightened large wildfire risk. Understanding patterns in woody cover increases will be paramount for assessing potential ecological outcomes and developing region-specific management approaches. Using remotely sensed land-use and vegetation cover data, we quantified changes in woody cover between 2001 and 2021 across land-use types in the eastern U.S. to determine the relative contribution of forest infilling and land-use conversion to woody cover increases. Woody cover increased across a range of land-use types in the eastern U.S. including wetlands, pasturelands, and forests. Infilling of deciduous forests and encroachment in open land-use types such as pasturelands dominated the northeast. In contrast, high levels of land-use conversion from non-woody land-use types to forests along with increasing woody cover in wetlands dominated the southeast. Our findings suggest that increasing woody cover in the eastern U.S. likely reflects both intentional increases of woody cover by silviculture as well as unintentional increases tied to wetland woody encroachment and forest densification. Our findings highlight areas to target ecological impact assessments and management efforts. Further, we demonstrate a growing need to assess the potential impacts of expanding pine plantation area on forest ecology and changing wildfire risk.

Hurricane Ian caused aboveground biomass density (AGBD) losses across Florida's forests in the United States, highlighting the need for accurate, large-scale monitoring tools. We combined Global Ecosystem Dynamics Investigation (GEDI) LiDAR data with synthetic aperture radar (SAR) and passive optical satellite imagery to model GEDI AGBD as a function of image-derived data, enabling predictions across the study area and producing continuous AGBD maps. Validation using in situ field data demonstrated high model performance, with an R2 of 0.93 and a root mean square difference (RMSD) of 39.3%. Spatial uncertainty reflecting bootstrap-derived variance remained consistent, with relative standard errors around 90% across the years analyzed. The data are accessible through a web application, RapidFEM4D, enabling researchers and stakeholders to assess AGBD maps for areas of interest. These datasets support monitoring forest recovery, assessing carbon dynamics, and guiding post-hurricane management and restoration. The RapidFEM4D platform facilitates access and analysis of Hurricane Ian's impact on Florida's forests, empowering stakeholders with actionable insights and offering a model for similar efforts in other hurricane-prone regions.

The almost complete eradication of fire from grasslands in North America has led to non-linear hysteretic transitions to shrub- and woodlands that the reintroduction of low-intensity fire is unable to reverse. We explore the ability of the extreme ends of variation in fire behavior to help overcome hysteretic threshold behaviors in huisache (Vachellia farnesiana) encroached grasslands. We contrasted experimental fire treatments with unburned control areas to assess the ability of extreme fires burned during drought to alter the density and structure of huisache. We found that extreme fires reduced the density of huisache by over 30% compared to control plots, both through driving huisache mortality and reducing the number of new recruits following treatments. For instance, extreme fire drove 48% huisache mortality compared to 4% in control treatments. For surviving plants, the number of stems increased but the crown area did not significantly change. Prescribed fire, conducted under the right conditions, can drive high mortality in one of the most notorious encroaching species in the southern U.S. Great Plains. With the fire conditions observed in this study likely to increase under future climate projections, utilizing extreme fire as a management tool for huisache will help scale up management to meet the growing extent of woody encroachment into grasslands.

Woody encroachment has driven drastic declines in grassland biodiversity and productivity. In the U.S. Great Plains, high-intensity prescribed fire is increasingly being used to shift encroaching redcedar woodlands to a grassland state. High-intensity fire treatments drive redcedar mortality and increase herbaceous biomass. However, it is unclear how grassland community composition recovers following stand-consuming fire. We contrast herbaceous community composition, basal cover, and species richness in woodlands treated with stand-consuming high-intensity fire to reference grassland and woodland sites to examine whether high-intensity fires facilitate restoration of grassland communities. To determine the long-term outcomes of high-intensity fire treatments, we use a space-for-time substitute to measure changes to herbaceous community and species richness over a time-since-fire gradient of 17 years. We found that herbaceous cover and species richness increased substantially in woodlands treated with stand-consuming high-intensity fire compared to unburned woodlands, and that these values were similar to those observed in both burned and unburned grasslands. Herbaceous community composition in woodlands treated with high-intensity fire also shifted towards grasslands, though some legacies of woodland communities persisted. Time-since-fire generally did not have a large influence on total herbaceous cover or species richness through time, though grass cover decreased in woodlands treated with high-intensity fire a decade post-treatment. Our findings suggest that a single high-intensity fire can support the restoration of herbaceous plant species richness and cover, and shift community composition to a grassland regime, though additional low-intensity fire treatments may be necessary to erode legacies from the encroached state.

Implementing strategies to navigate large-scale ecological transitions in grasslands is one of this century's greatest conservation challenges. In the US Great Plains, managing areas impacted by woody transitions have been reactive, short-lived, costly, and ineffective. Along with current technological innovation in rangeland monitoring, the promise of early warning science is to provide managers with sufficient time to be better prepared for novel signals of ecological change. Combining the science of early warning signals and frameworks such as the Resist - Accept - Direct (RAD) can provide land managers with guidelines to identify proactive strategies when facing ecological change. Using this approach, we found that opportunities to resist woody transitions decreased from 84 % to 60 % between 1990 and 2020 over the entire biome but remained highest in the northern and western Great Plains, which contributes to large scale conservation targets. These are key areas to prioritize resist opportunities. In contrast, 11 % of the biome exhibited early warning transition signals across all hierarchical scales by 2020, a fourfold increase since 1990. Lastly by 2020, 30 % of the biome exhibited early warning signals across multiple but not all scales. Here, efforts may be more effective when management is directed to conserve fragmented grassland legacies within a woody-dominated matrix and avoid large-scale monocultures of problematic encroaching woody species. Our multi-scale study indicates that 1) anchoring to the last remaining grassland core areas with no early warning of transitions and 2) strategically investing in these intact grasslands may provide the best results for grassland conservation.

Accurate mapping of aboveground biomass density (AGBD) is vital for ecological research and carbon cycle monitoring. Integrating multi-source remote sensing data offers significant potential to enhance the accuracy and coverage of AGBD estimates. This study evaluated three upscaling frameworks for integrating GEDI LiDAR, SAR, and optical satellite data to create wall-to-wall AGBD maps. The frameworks tested in this paper were: (1) a single-step approach using optical imagery, (2) a two-stage approach with GEDI-derived variables, and (3) a three-stage approach combining imagery and in situ-derived allometries. Internal validation showed that framework 1 achieved the lowest root mean square difference (%RMSD) of 53.3% and highest coefficient of determination (R2) of 0.53. An independent external validation of the AGBD map was performed using in situ observations, also revealing that framework 1 was the most accurate (%RMSD = 39.3% and R2 = 0.93), while frameworks 2 and 3 were less accurate (%RMSD = 54.7, 44.7 and R2 = 0.95, 0.90, respectively). Herein, we show that upscaling frameworks significantly impacted AGBD map uncertainty and the magnitude of estimate differences. Our findings suggest that upscaling framework 1 based on a single step approach was the most effective for capturing detailed AGBD variations, while careful consideration of model sensitivity and map uncertainties is essential for reliable AGBD estimation. This study provides valuable insights for advancing forest AGBD monitoring and highlights the potential for further enhancements in remote sensing methodologies.

Background The recent increase in large wildfires in the eastern United States makes it crucial to examine the subsequent risk to human life and property. In the eastern US, the wildland-urban interface (WUI), where wildfire risk is greatest, has expanded tremendously over the last three decades. Aims This study aimed to understand how increasing wildfires in the eastern US are manifesting in the WUI. Methods We quantified WUI growth and characterised large (>200 ha) wildfire regimes inside and outside the WUI at multiple spatial scales across the eastern US between 1986 and 2021. Key results WUI wildfires in the eastern US comprised 45% of all large wildfires and 55% of the area burned, were on average 46% larger than non-WUI wildfires, and are becoming more frequent in spring. Most increases in wildfire number and area burned occurred outside of the WUI. Conclusion The WUI plays an important role in large wildfire dynamics in the eastern US; however, increases in the number of large wildfires have occurred primarily outside the WUI. Implications Our findings highlight important interactions between human development and large wildfire occurrence in the eastern US and should be used to direct future region-specific assessments of changing wildfire risk.

Increasing wildfire activity has spurred an increasing push for the application of prescribed fire to reduce wildfire risk while simultaneously acting as a surrogate for fire's historical role as a fundamental ecosystem process. However, prescribed fires are often ignited using uniform ignitions to maintain operational control and there are concerns that they may not be able to replicate the landscape heterogeneity, particularly patterns in unburned patches, generated by historical fires. Fire refugia, unburned areas within fire perimeters, play an integral role in determining post-fire recovery and community structure. We assess patterns in fire refugia across 443 large (>200 ha) wildfire and prescribed fire perimeters using remotely sensed fire severity data in longleaf pine ( Pinus palustris) ) savannas of the Florida Panhandle. Contrary to concerns, large prescribed fires had a significantly greater proportion of unburned area than wildfires, driven by larger refugia patch sizes. Drier conditions promoted smaller and more numerous fire refugia patches. Our study demonstrates differences in wildfires versus prescribed fire outcomes on landscape structure, with implications for future longleaf pine savanna management.

AbstractLarge wildfires are increasing in the eastern United States; however, what factors are heightening large wildfire risk remains unclear. Increases in fuel loads from woody encroachment and canopy infilling have been associated with increasing wildfire risk in other US regions. Understanding if and where woody cover increases wildfire risk can help direct proactive fuels management. We characterize multi‐scale changes in woody cover through time and assess the relationship between woody cover and large wildfire (>200 ha) occurrence in the eastern US between 1990 and 2020. We found a 37% increase in woody cover across the eastern US, with increases occurring in every ecoregion. The odds of large wildfire increased as woody cover increased in most central and southern ecoregions, where large wildfires were typically more likely in areas with high woody cover (70%–100% cover). Our findings suggest fuels management will be an important tool for reducing large wildfire risk.

Conservation is increasingly focused on preventing losses in species' populations before they occur. Tracking changes in demographic parameters that can impact a population's resilience in response to drivers of global change can support early conservation efforts. We assessed trends in population productivity (late summer juveniles per 100 females) relative to drivers of global change in 40 pronghorn (Antilocapra americana) herds across sagebrush (Artemisia spp.) steppe in Wyoming. Pronghorn are an iconic rangeland species that have been exposed to increasing levels of anthropogenic, climatic, and land -use change. Using data collected across the state of Wyoming, we (1) assessed long-term trends in population productivity, (2) identified patterns in large-scale drivers of global change (i.e., climate, land cover change) across pronghorn habitat, and (3) determined the relationship between drivers of global change and population productivity over a 35 -year (1984-2019) period. While Wyoming hosts some of the most abundant populations of pronghorn in North America that have been largely stable in recent years, we found many herds are experiencing long-term declines in productivity. Long-term declines in productivity were associated with increases in oil and gas development and woody encroachment. Although increasing across almost all herd units, woody vegetation cover remains at low levels, suggesting that pre-emptive management may help to prevent losses in pronghorn populations.

Woody encroachment is one of the greatest threats to grasslands globally, depleting a suite of ecosystem services, including forage production and grassland biodiversity. Recent evidence also suggests that woody encroachment increases wildfire danger, particularly in the Great Plains of North America, where highly volatile Juniperus spp. convert grasslands to an alternative woodland state. Spot-fire distances are a critical component of wildfire danger, describing the distance over which embers from one fire can cause a new fire ignition, potentially far away from fire suppression personnel. We assess changes in spot-fire distances as grasslands experience Juniperus encroachment to an alternative woodland state and how spot-fire distances differ under typical prescribed fire conditions compared to conditions observed during wildfire. We use BehavePlus to calculate spot-fire distances for these scenarios within the Loess Canyons Experimental Landscape, Nebraska, U.S.A., a 73,000-ha ecoregion where private-lands fire management is used to reduce woody encroachment and prevent further expansion of Juniperus fuels. We found prescribed fire used to control woody encroachment had lower maximum spot-fire distances compared to wildfires and, correspondingly, a lower amount of land area at risk to spot-fire occurrence. Under more extreme wildfire scenarios, spot-fire distances were 2 times higher in grasslands, and over 3 times higher in encroached grasslands and Juniperus woodlands compared to fires burned under prescribed fire conditions. Maximum spot-fire distance was 450% greater in Juniperus woodlands compared to grasslands and exposed an additional 14,000 ha of receptive fuels, on average, to spot-fire occurrence within the Loess Canyons Experimental Landscape. This study demonstrates that woody encroachment drastically increases risks associated with wildfire, and that spot fire distances associated with woody encroachment are much lower in prescribed fires used to control woody encroachment compared to wildfires.

AbstractFire is a fundamental ecological process in rangeland ecosystems. Fire drives patterns in both abiotic and biotic ecosystem functions that maintain healthy rangelands, making it an essential tool for both rangeland and wildlife management. In North America, humanity’s relationship with fire has rapidly changed and shifted from an era of coexistence to one that attempts to minimize or eliminate its occurrence. Prior to Euro-American settlement, Indigenous people’s coexistence with fire led to regionally distinct fire regimes that differed in terms of their fire frequency, intensity, severity, seasonality, and spatial complexity. As the relative occurrence of prescribed fire and wildfire continue to change in North American rangelands, it is necessary for wildlife managers to understand the complex social-ecological interactions that shape modern fire regimes and their conservation outcomes. In this chapter, we discuss the fire eras of North American rangelands, introduce foundational relationships between fire and wildlife habitat, and discuss potential futures for fire in wildlife management.

The occurrence of hurricanes in the Southern U.S. is increasingly frequent and quantifying the damage caused to forests is crucial to assist in protection measures and understanding the dynamics of recovery. The aim of this study is to develop a data fusion framework based on NASA’s GEDI (Global Ecosystem Dynamics Investigation) and Landsat 8 OLI for mapping aboveground biomass density (AGBD, Mg/ha) that can be further used to damage severity and recovery in forested ecosystems impacted by Hurricane Ian in Florida. We used GEDI level 4A and L8 data for calibrating a Random Forest (RF) for predicting and mapping AGBD at four-months pre-Hurricane Ian disturbance across areas impacted by Hurricane Ian. The RF model showed good performance with R 2 = 0.79, absolute and relative RMSE of 29.17 Mg/ha (64.27%) and Bias of −1.14 Mg/ha (2.66%), respectively. This research highlights methodological opportunities for fusing GEDI and L8 data streams toward improved AGB mapping and for assessing the impact of Hurricane Ian disturbance in Florida through data fusion.

Abstract Large wildfires are increasing across numerous regions of the globe. While the West has remained a primary focus of wildfire research and resources in the U.S., recent signals suggest that wildfire risk is increasing in the eastern U.S. as well. We conducted an in‐depth assessment of large (>200 ha) wildfire regime characteristics (size, number, total hectares burned, seasonality, probability of occurrence, and ignition source) over a 36‐year period across the Eastern Temperate Forests of the U.S. to quantify geographic patterns in large‐wildfire regime and identify changing spatio‐temporal large wildfire patterns. We found increases in large wildfire size, occurrence, number, and total hectares burned in the southern and eastern regions of the Eastern Temperate Forests. In contrast, large wildfires declined or were minimal in northern ecoregions. We demonstrate increasing large wildfires across some of the most populated regions of the United States.

Abstract Fire is a fundamental ecological process in rangeland ecosystems. Fire drives patterns in both abiotic and biotic ecosystem functions that maintain healthy rangelands, making it an essential tool for both rangeland and wildlife management. In North America, humanity’s relationship with fire has rapidly changed and shifted from an era of coexistence to one that attempts to minimize or eliminate its occurrence. Prior to Euro-American settlement, Indigenous people’s coexistence with fire led to regionally distinct fire regimes that differed in terms of their fire frequency, intensity, severity, seasonality, and spatial complexity. As the relative occurrence of prescribed fire and wildfire continue to change in North American rangelands, it is necessary for wildlife managers to understand the complex social-ecological interactions that shape modern fire regimes and their conservation outcomes. In this chapter, we discuss the fire eras of North American rangelands, introduce foundational relationships between fire and wildlife habitat, and discuss potential futures for fire in wildlife management.

Fire can alter the trajectory for plant invasions; however, invasive plant responses to fire vary among regions and species. It is unclear how recent increases in large, mixed-severity wildfires in eastern ponderosa pine forests of North America have influenced patterns in plant species invasion. We sampled invasive plant species across three mixed-severity wildfire perimeters over 3666 sample sites in eastern ponderosa pine of western Nebraska, USA. Our analysis sought to determine whether invasive species occurred more frequently and at greater abundance in burned areas, and whether either frequency of occurrence or abundance of invasive plants could be explained by fire severity. We found complex relationships between mixed-severity wildfire and invasive plant species. Cheatgrass (Bromus tectorum) was the most common invasive species sampled, followed by Kentucky bluegrass (Poa pratensis) and smooth brome (Bromus inermis). Cheatgrass and Kentucky bluegrass were more common in burned areas. Cheatgrass occurrence was higher in low and moderate severity burned areas than in unburned locations. While cheatgrass occurred at a similar number of sample sites in unburned and high severity burned areas, cheatgrass cover was lower at high severity burned sites compared to unburned sites. Our results emphasize variation in invasive plant species occurrence and cover in relation to fire in eastern ponderosa pine savannas and the importance of making ecosystem specific decisions regarding invasive species management in response to wildfire.

Human alteration of fire regimes is a hallmark of the Anthropocene; yet few studies have fully explored the implications of utilizing high-intensity fires in grasslands and savannas to manage shrub encroachment. Decades of fire research in South Africa inspired a unique convergence of high-intensity fire experiments in the USA. In the Great Plains of North America, high-intensity fire trials were designed to remove traditional investigator constraints that minimised variability in fire intensity and to explore woody mortality thresholds across a broader suite of experimental conditions. At the same time, studies in the Kruger National Park, South Africa, similarly investigated high-intensity fires to examine previously unstudied relationships between high-intensity fires and woody encroachment. These scientific pursuits have contributed to theoretical advances in our understanding of fire-vegetation dynamics. In this paper, we synthesise these high-intensity fire experiments, the empirical evidence emerging from them and their importance for managing grassland and savanna ecosystems, and the lessons learned and challenges ahead to maintaining critical ranges of variation in fire regimes during the Anthropocene.