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At least 127 records · Page 7Linked to original sources
USGS2022

Potential effects of energy development on environmental resources of the Williston Basin in Montana, North Dakota, and South Dakota—Physiography, climate, land use, and demographics

The Williston Basin has been a leading domestic oil and gas producing region. As energy demands have increased, so has energy development. A group of 13 Federal agencies and Tribal groups formed the Bakken Federal Executive Group to address common challenges associated with energy development, with a focus on understanding the cumulative environmental challenges attributed to oil and gas development throughout the basin. To better understand the natural resources in the Williston Basin, the U.S. Geological Survey, in cooperation with the Bureau of Land Management, began work to synthesize existing information on science topics that will support management decisions related to energy development. This report is a compilation of information regarding the natural setting, energy development history, demographics, and related investigations related to energy development in the Williston Basin of Montana, North Dakota, and South Dakota. Completed and ongoing investigations include the topical areas of unconventional oil and gas assessments, water quality, water availability, air quality, effects on human health, and ecological effects.

Montana, North Dakota, South Dakota↗
USGS2019

A Methodology to Assess the National and Regional Impacts of U.S. Wind Energy Development on Birds and Bats

This scientific investigations report describes an effort by the U.S. Geological Survey (USGS) that used research, monitoring data, and modeling to develop a methodology to assess both the current and future population-level consequences of wind energy development on species of birds and bats that are present in the United States during any part of their life cycle. The methodology is currently applicable to birds and bats, focuses primarily on the effects of collisions with turbines, and can be applied to any species that breeds in, migrates through, or otherwise uses any part of the United States. The methodology assesses species at the national and regional scales and identifies those species potentially in need of more detailed study, as well as those species that are likely at low risk from wind energy development. This approach is fundamentally different from existing methods focusing on impacts at individual facilities. This report supersedes USGS Scientific Investigations Report 2015–5066 by the same authors, which described a preliminary version of the methodology. Following reviews of the preliminary methodology by a panel of external experts, public comments, and additional internal review, the methodology was revised and finalized. The three components of the refined methodology described in this new report rely on publicly available fatality information, population estimates, species range maps, turbine location data, biological characteristics of species, and population models. First, three metrics are combined to determine direct and indirect relative effects from wind energy facilities to generate a list of species scores. Second, a generic population model estimates the expected change in population trend caused by the additive mortality from collisions with wind turbines. Third, the methodology combines an estimate of observed fatalities and an estimate of potential biological removal to assess the possibility of a decrease in population size. The latter two components are quantitative. In a test case, the methodology was used to analyze data for six bird species and three bat species. Components of the methodology are based on simplifying assumptions and require information that, for many species, may be sparse or unreliable or may require further study. These assumptions should be carefully considered when using outputs from the methodology. Increases in the quality of data for fatalities from collisions with wind turbines, species distributions, abundance, and demography will likely improve results for uses of the methodology. The methodology’s design identifies and prioritizes a subset of the bird and bat species that may experience population-level impacts from collisions with wind turbines, both currently and from future wind energy development in the United States. Results of an assessment using this methodology could focus future research to improve our understanding of those impacts and to guide avoidance and minimization strategies. In addition, this methodology can be used to identify species for more intensive demographic modeling or to highlight those species that may not require any additional research because effects of wind energy development on their populations are projected to be small. The effects of wind energy facilities on nine unidentified species used in the test case described in this report have not been assessed. Their data were simply used to show the application of the methodology to real-world data and the types of outputs it would produce.

Scientific Investigations Report↗
USGS2022

The potential of wave energy conversion to mitigate coastal erosion from hurricanes

Wave energy conversion technologies have recently attracted more attention as part of global efforts to replace fossil fuels with renewable energy resources. While ocean waves can provide renewable energy, they can also be destructive to coastal areas that are often densely populated and vulnerable to coastal erosion. There have been a variety of efforts to mitigate the impacts of wave- and storm-induced erosion; however, they are either temporary solutions or approaches that are not able to adapt to a changing climate. This study explores a green and sustainable approach to mitigating coastal erosion from hurricanes through wave energy conversion. A barrier island, Dauphin Island, off the coast of Alabama, is used as a test case. The potential use of wave energy converter farms to mitigate erosion due to hurricane storm surges while simultaneously generating renewable energy is explored through simulations that are forced with storm data using the XBeach model. It is shown that wave farms can impact coastal morphodynamics and have the potential to reduce dune and beach erosion, predominantly in the western portion of the island. The capacity of wave farms to influence coastal morphodynamics varies with the storm intensity.

Alabama↗
USGS1977

Tactical approach for determining impact of energy development on wildlife in Wyoming: special report number 1

The U.S. Fish and Wildlife Service, within the Department of Interior, is responsible for providing national leadership in the management and protection of the nation's fish and wildlife resources, their habitat, and environment. Specifically, the Office of Biological Services obtains and assimilates biological and environmental data and identifies additional informational needs and means necessary to provide biological input into major natural resource decisions. The Wyoming Coal Coordinator for the U.S Fish and Wildlife Service is assigned the duty of becoming attuned to the ramifications of energy development within the State and its potential impact upon wildlife. In order for the Coal Coordinator to fulfill his obligations in becoming an "energy expert" for the Fish and Wildlife Service in Wyoming, it will be necessary for him to develop a means of obtaining an overview of the energy development situation. Similarly, in order for him to identify those area of critical concern to wildlife resources, it will be necessary that he determine or predict where energy development will occur, the nature of this development, and the cumulative effects of energy development upon wildlife. Likewise, in order to identify where wildlife data gaps occur and to determine future wildlife information needs, it will be necessary for him to compile and synthesize relevant existing data resources. It therefore becomes apparent that a need exists for him to gather and interpret pertinent information in a systematic way to meet these ends. The following is an account of the tactical number in which the Wyoming Coal Coordinator intends to approach the duties outlined above the rationale to be followed in meeting these needs. First, a general discussion on assessing impacts on wildlife is provided to form a basis for obtaining an overview. Secondly, a series of reports which will be generated to summarize existing information and to help identify potential problem areas is outlined. These reports will be further utilized to determine wildlife data gaps and future information needs related to wildlife and future energy development.

Wyoming↗
USGS2013

Energy cost of vessel disturbance to Kittlitz's Murrelets Brachyramphus brevirostris

We evaluated the energy cost of vessel disturbance for individual Kittlitz’s Murrelets Brachyramphus brevirostris in Glacier Bay National Park and Preserve in Alaska, USA. We used Monte Carlo simulations to model the daily energy expense associated with flight from vessels by both breeding and non-breeding birds and evaluated risk based on both the magnitude of costs incurred and the degree to which the costs may be chronic. We used two scenarios of vessel disturbance for average- and peak-vessel traffic. Because they are more likely to fly away from vessels, non-breeding birds had a greater increase in energy expenditure when disturbed (up to 30% increase under the average scenario and >50% increase under the peak scenario) than breeders (up to 10% and 30% increases under the average and peak scenarios, respectively). Likewise, non-breeding birds were more likely to experience chronic increases in energy expense (i.e. a greater percentage of days with an increase in energy expenditure) than breeding birds. Our modeling results indicated that breeding and non-breeding birds were both susceptible to fitness consequences (e.g. reduced reproductive success and survival) resulting from the energy cost.

Alaska↗
USGS2017

Using science to inform management and improve biological conservation in the Desert Renewable Energy Conservation Plan

The Mojave and Colorado deserts of southern California have been viewed as vast wilderness since early exploration and, until recently, were considered the most untrammeled among western landscapes in the contiguous lower 48 states (United States Department of Agriculture 1893; Leu et al. 2008). However, the factors that define desert wilderness—small human population, temperature differentials that create unrelenting winds, low rainfall, and cloudless skies—are attractive for renewable energy development. The demand for clean, renewable energy is a national and regional priority and has increased demand for large-scale solar and wind farms in the deserts, particularly in California. The need to balance these national and state energy priorities with existing natural resource and land conservation policies has emerged as a landscape-scale land-use planning initiative known as the Desert Renewable Energy Conservation Plan (DRECP). One of the primary goals for the DRECP was to establish Development Focus Areas (DFAs) where high-quality renewable energy potential of up to 20 gigawatts (GW) could be implemented by the year 2040. DFAs were designed to provide expedited project approvals in locations where environmental impacts could be managed and mitigated, and proximity to transmission corridors provides for the efficient dissemination of energy to users. The DRECP also aims to identify protections for natural resources, recreation, and cultural resources. This plan identifies 37 covered species that receive special consideration in the DRECP. Among the special considerations are climate adaptation requirements, such as the ability to maintain population connectivity through wildlife corridors, while protecting several special recreation areas and 32,000 known cultural sites that are dispersed throughout the region. We evaluated several particular aspects of the DRECP design and process. In particular, we examined land designations in relation to published studies on Mohave ground squirrel (Xerospermophilus mohavensis) habitat and genetic diversity patterns of a suite of broadly distributed desert animal species. The squirrel and its habitat are of particular interest because the entire range of the squirrel is encompassed by the DRECP. We describe the framework of the DRECP, provide a case study of how the DRECP accommodates the needs of the Mohave ground squirrel and its habitat, illustrate DFAs in relation to the genetic diversity of a broad range of terrestrial biota, and conclude with some observations on how land-use issues were resolved across the landscape under various scenarios.

Conference Paper↗
USGS2024

An invasive predator substantially alters energy flux without changing food web functional state or stability

Understanding how invasive species affect the stability and function of ecosystems is critical for conserving ecosystems. Here, we quantified the effect of an actively suppressed invasive species on the Yellowstone Lake, U.S.A. ecosystem using a food-web energetics approach. 2. We compared energy flux, functional state, and stability of four food web states: a pre-invasion network, and three post-invasion networks undergoing active invasive species suppression: initial invasion; expansion; decline. 3. Invasion caused > 25% change (±) in energy flux for most consumers, and total flux increased twofold post-invasion. Flux to the species of conservation concern, Yellowstone cutthroat trout ( Oncorhynchus virginalis bouvieri ), was 2.8-times less post-invasion vs pre-invasion while invasive lake trout ( Salvelinus namaycush ) flux was up to 17.3-times higher compared to the initial invasion network. The dominant functional state and food web stability did not change post-invasion, likely due to introduction of a generalist predator and the stabilizing effect of suppression. 4. Lake trout invasion in Yellowstone Lake caused large changes to energy flux, shifting dominant fluxes away from the species of conservation concern, despite not changing functional state or stability. We demonstrate that changes in energy flux may signal invasions in ecosystems, but functional state or stability may not necessarily reflect the magnitude of invasion influences. 5. Implications for conservation: For invaded fish communities, a better understanding of how the invasive species controls the food web beyond just the direct influence on prey results can be achieved by investigating energy flux, functional state, and food-web stability. Furthermore, evaluating the effect of suppression beyond the invasive species can demonstrate the far-reaching value of suppression management actions for conservation.

Wyoming↗
USGS2021

Migrating whooping cranes avoid wind-energy infrastructure when selecting stopover habitat

Electricity generation from renewable-energy sources has increased dramatically worldwide in recent decades. Risks associated with wind-energy infrastructure are not well understood for endangered whooping cranes or other vulnerable crane populations. From 2010 to 2016, we monitored 57 whooping cranes with remote-telemetry devices in the United States Great Plains to determine potential changes in migration distribution (i.e., avoidance) caused by presence of wind-energy infrastructure. During our study, the number of wind towers tripled in the whooping crane migration corridor and quadrupled in the corridor’s center. Median distance of whooping crane locations from nearest wind tower was 52.1 km, and 99% of locations were >4.3 km from wind towers. A habitat selection analysis revealed that whooping cranes used areas ≤5.0 km (95% CI = 4.8–5.4) from towers less than expected (i.e., zone of influence) and that whooping cranes were 20 times (95% CI: 14–64) more likely to use areas outside compared to adjacent to towers. Eighty percent of whooping crane locations and 20% of wind towers were located in areas with the highest relative probability of whooping crane use based on our model, which comprised 20% of the study area. Whooping cranes selected for these places, whereas developers constructed wind infrastructure at random relative to desirable whooping crane habitat. As of early 2020, 4.6% of the study area and 5.0% of the highest-selected whooping crane habitat were within the collective zone of influence. The affected area equates to habitat loss ascribed to wind-energy infrastructure; losses from other disturbances have not been quantified. Continued growth of the whooping crane population during this period of wind infrastructure construction suggests no immediate population-level consequences. Chronic or lag effects of habitat loss are unknown but possible for long-lived species. Preferentially constructing future wind infrastructure outside of the migration corridor or inside of the corridor at sites with low probability of whooping crane use would allow for continued wind-energy development in the Great Plains with minimal additional risk to highly selected habitat that supports recovery of this endangered species.

Kansas, Montana, Nebraska, North Dakota, Oklahoma,↗
USGS2023

Wind-energy development alters pronghorn migration at multiple scales

Migration is a critical behavioral strategy necessary for population persistence and ecosystem functioning, but migration routes have been increasingly disrupted by anthropogenic activities, including energy development. Wind energy is the world's fastest growing source of electricity and represents an important alternative to hydrocarbon extraction, but its effects on migratory species beyond birds and bats are not well understood. We evaluated the effects of wind-energy development on pronghorn migration, including behavior and habitat selection, to assess potential effects on connectivity and other functional benefits including stopovers. We monitored GPS-collared female pronghorn from 2010 to 2012 and 2018 to 2020 in south-central Wyoming, USA, an area with multiple wind-energy facilities in various stages of development and operation. Across all time periods, we collected 286 migration sequences from 117 individuals, including 121 spring migrations, 123 fall migrations, and 42 facultative winter migrations. While individuals continued to migrate through wind-energy facilities, pronghorn made important behavioral adjustments relative to turbines during migration. These included avoiding turbines when selecting stopover sites in spring and winter, selecting areas farther from turbines at a small scale in spring and winter, moving more quickly near turbines in spring (although pronghorn moved more slowly near turbines in the fall), and reducing fidelity to migration routes relative to wind turbines under construction in both spring and fall. For example, an increase in distance to turbine from 0 to 1 km translated to a 33% and 300% increase in the relative probability of selection for stopover sites in spring and winter, respectively. The behavioral adjustments pronghorn made relative to wind turbines could reduce the functional benefits of their migration, such as foraging success or the availability of specific routes, over the long term.

Wyoming↗
USGS2017

Estimating daily lake evaporation from biweekly energy‐budget data

Estimates of daily lake evaporation based on energy‐budget data are poor because of large errors associated with quantifying change in lake heat storage over periods of less than about 10 days. Energy‐budget evaporation was determined during approximately biweekly periods at a northern Minnesota, USA, lake for 5 years. Various combinations of shortwave radiation, air temperature, wind speed, lake‐surface temperature, and vapour‐pressure difference were related to energy‐budget evaporation using linear‐regression models in an effort to determine daily evaporation without requiring the heat‐storage term. The model that combined the product of shortwave radiation and air temperature with the product of vapour‐pressure difference and wind speed provided the second best fit based on statistics but provided the best daily data based on comparisons with evaporation determined with the eddy‐covariance method. Best‐model daily values ranged from −0.6 to 7.1 mm/day over a 5‐year period. Daily averages of best‐model evaporation and eddy‐covariance evaporation were nearly identical for all 28 days of comparisons with a standard deviation of the differences between the two methods of 0.68 mm/day. Best‐model daily evaporation also was compared with two other evaporation models, Jensen–Haise and a mass‐transfer model. Best‐model daily values were substantially improved relative to Jensen–Haise and mass‐transfer values when daily values were summed over biweekly energy‐budget periods for comparison with energy‐budget results.

Northern Minnesota↗
USGS2006

Evaluation of energy expenditure in adult spring Chinook salmon migrating upstream in the Columbia River Basin: an assessment based on sequential proximate analysis

The upstream migration of adult anadromous salmonids in the Columbia River Basin (CRB) has been dramatically altered and fish may be experiencing energetically costly delays at dams. To explore this notion, we estimated the energetic costs of migration and reproduction of Yakima River-bound spring Chinook salmon Oncorhynchus tshawytscha using a sequential analysis of their proximate composition (i.e., percent water, fat, protein, and ash). Tissues (muscle, viscera, and gonad) were sampled from fish near the start of their migration (Bonneville Dam), at a mid point (Roza Dam, 510 km upstream from Bonneville Dam) and from fresh carcasses on the spawning grounds (about 100 km above Roza Dam). At Bonneville Dam, the energy reserves of these fish were remarkably high, primarily due to the high percentage of fat in the muscle (18-20%; energy content over 11 kJ g-1). The median travel time for fish from Bonneville to Roza Dam was 27 d and ranged from 18 to 42 d. Fish lost from 6 to 17% of their energy density in muscle, depending on travel time. On average, fish taking a relatively long time for migration between dams used from 5 to 8% more energy from the muscle than faster fish. From the time they passed Bonneville Dam to death, these fish, depending on gender, used 95-99% of their muscle and 73-86% of their viscera lipid stores. Also, both sexes used about 32% of their muscular and very little of their visceral protein stores. However, we were unable to relate energy use and reproductive success to migration history. Our results suggest a possible influence of the CRB hydroelectric system on adult salmonid energetics.

Oregon, Washginton↗
USGS2024

True metabolizable energy of foods consumed by lesser scaup (Aythya affinis)

The energy derived from available foods is an important factor used in conservation planning for migratory species. Estimating true metabolizable energy (TME) of available foods has become a common method for resource managers to increase reliability in energetic carrying-capacity estimates. Lesser scaup ( Aythya affinis ; hereafter scaup), have experienced a population decline concurrent with suspected decreases in foraging habitat quality and quantity at spring stopover sites in the upper Midwest, USA. Unfortunately, few TME estimates are available for common diet items of scaup. We estimated nitrogen-adjusted TME (TME N ) of 5 common foods of scaup by conducting feeding trials on wild females and males. True metabolizable energy varied by food taxa, but not by pretrial body mass or sex. Mean TME N (kcal/g[dry] ± SE) was greatest for wild millet ( Echinochloa crus-galli ; 2.20 ± 0.14), followed by chironomids ( Chironomus spp.; 1.41 ± 0.49), amphipods ( Gammarus spp .; 1.33 ± 0.23 ) , planorbid snails (Planorbidae; 0.17 ± 0.07), and fingernail clams (Sphaeriidae; −0.79 ± 0.27). Our results, combined with scaup diet literature indicated that the management of spring staging areas for high-energy invertebrates (i.e., chironomids and amphipods) would provide improved opportunity for energy acquisition during migration. Further study could help determine if the acclimation of scaup to particular diets, especially bivalves, increases their TME N values.

Wildlife Society Bulletin↗
USGS2016

Light Goose Conservation Order effects on nontarget waterfowl behavior and energy expenditure

When the Light Goose Conservation Order (LGCO) was established during 1999 in the Rainwater Basin of Nebraska, USA, LGCO activities were limited to 4 days/week and 16 public wetlands were closed to the LGCO to limit disturbance to nontarget waterfowl during this energetically important time period. However, the effects of LGCO activities on waterfowl behavior and energy expenditure are relatively unknown in this critical waterfowl staging area. To evaluate LGCO effects on target and nontarget species, we paired wetlands open and closed to LGCO and recorded waterfowl behavior and hunter encounters during springs 2011 and 2012. We constructed hourly energy expenditure models based on behavior data collected for mallards ( Anas platyrhynchos ) and northern pintails ( A. acuta ). In 2011, dabbling ducks ( Anas spp.) spent more time feeding and less time resting in wetlands closed to hunting during early season when the majority of hunting encounters occurred; behaviors did not differ between hunt categories during late season when hunting activities subsided. However, in 2012, dabbling ducks spent more time feeding and less time resting in wetlands open to hunting during early and late seasons. We detected no differences in behaviors of lesser snow geese ( Chen caerulescens ) or greater white-fronted geese ( Anser albifrons ) between hunting categories in early season. Mallards had slightly greater energy expenditure on wetlands closed to hunting ( = 38.94 ± 0.31 kJ/bird/hr), compared with wetlands open to hunting ( = 37.87 ± 0.32 kJ/bird/hr); therefore, greater energy spent by mallards cannot be attributed to hunting disturbance. We also detected no differences in dabbling duck behavior or energy expenditure between days open or closed to hunting in the region. A refuge system of wetlands closed to LGCO activities in the Rainwater Basin may be an important management strategy in providing reduced disturbance for nontarget waterfowl species in some years. Published 2016. This article is a U.S. Government work and is in the public domain in the USA.

Nebraska↗
USGS2018

Assessment of potential risks from renewable energy development and other anthropogenic factors to wintering Golden Eagles in the western United States

Wind and other energy development are expanding rapidly and on an unprecedented scale within the range of the Golden Eagle ( Aquila chrysaetos ) while other anthropogenic-related changes, wildfires, invasive plants, drought, and climate change are altering or destroying native habitats occupied by Golden Eagles. However, the potential effects of these factors on North American Golden Eagle populations are largely unknown and the most recent evidence indicates that the population in the western United States is declining slightly. Impediments to evaluating the potential effects of energy development projects on wintering Golden Eagles include issues of scale and a paucity of available information about eagle winter use areas and ecology. We applied a predictive model of eagle winter distribution developed for Idaho and Montana, to Idaho, Utah, Nevada and eastern Oregon to help identify potential wintering areas and identify risks that occur in those areas. The model identifies ~40% of the four state study area as potentially suitable eagle winter habitat and provides a basis for spatial assessment of possible risk factors to eagles wintering there. We used eBird and Christmas Bird Count citizen science datasets for an independent evaluation of the accuracy of our predictive distribution model. The model was robust, accurately predicting the presence of wintering Golden Eagles significantly more often than expected. We used digital environmental datasets (layers) of potential risk factors, in conjunction with model predicted eagle distribution, to better understand and estimate the extent of risks to the wintering eagle population in the study area. These layers represent available data for some of the factors previously identified as risks in the landscape to wintering Golden Eagles. The majority of predicted eagle wintering areas occurred where there was little habitat fragmentation (<10%). All predicted winter areas contained at least one potential risk factor (e.g., potential for energy development); 39.4% of predicted winter areas contained at least two known risk factors. The greatest number of risks often occurred where the human footprint was highest and where eagles were less likely to occur during winter. Our results can be used to help prioritize field surveys for identifying important Golden Eagle winter areas in the western United States and determine potential locations where energy development is least likely to have negative effects on wintering eagles. Survey efforts can be allocated in consideration of management and conservation objectives based on predicted habitat suitability and risk factors. For example, surveys for areas of high suitability and low risk can identify places to focus management for conservation of eagle winter areas. Further, sites proposed for wind energy development could be reviewed initially based on model predicted eagle wintering areas and then surveyed to determine if permitting for development is appropriate.

Book chapter↗
USGS1998

Evaporation from a small prairie wetland in the Cottonwood Lake area, North Dakota - An energy-budget study

Evaporation from Wetland P1 in the Cottonwood Lake area of North Dakota, USA was determined by the energy-budget method for 1982–85 and 1987. Evaporation rates were as high as 0.672 cm day −1 . Incoming solar radiation, incoming atmospheric radiation, and long-wave radiation emitted from the water body are the largest energy fluxes to and from the wetland. Because of the small heat storage of the water body, evaporation rates closely track solar radiation on short time scales. The effect of advected energy related to precipitation is small because the water quickly heats up by solar radiation following precipitation. Advected energy related to ground water is minimal because ground-water fluxes are small and ground-water temperature is only about 7 °C. Energy flux related to sediment heating and thermal storage in the sediments, which might be expected to be large because the water is clear and shallow, affects evaporation rates by less than 5 percent.

North Dakota↗
USGS2011

Balancing energy development and conservation: A method utilizing species distribution models

Alternative energy development is increasing, potentially leading to negative impacts on wildlife populations already stressed by other factors. Resource managers require a scientifically based methodology to balance energy development and species conservation, so we investigated modeling habitat suitability using Maximum Entropy to develop maps that could be used with other information to help site energy developments. We selected one species of concern, the Lesser Prairie-Chicken (LPCH; Tympanuchus pallidicinctus ) found on the southern Great Plains of North America, as our case study. LPCH populations have been declining and are potentially further impacted by energy development. We used LPCH lek locations in the state of Kansas along with several environmental and anthropogenic parameters to develop models that predict the probability of lek occurrence across the landscape. The models all performed well as indicated by the high test area under the curve (AUC) scores (all >0.9). The inclusion of anthropogenic parameters in models resulted in slightly better performance based on AUC values, indicating that anthropogenic features may impact LPCH lek habitat suitability. Given the positive model results, this methodology may provide additional guidance in designing future survey protocols, as well as siting of energy development in areas of marginal or unsuitable habitat for species of concern. This technique could help to standardize and quantify the impacts various developments have upon at-risk species.

Environmental Management↗
USGS2025

The effects of carnivory and herbivory on the energy balance of Arctic grizzly bears

Omnivores often face tradeoffs between selecting for spatially dispersed energy-dense vertebrate prey versus densely distributed herbivorous resources that have limited energetic value per unit intake. Arctic grizzly bears ( Ursus arctos ) are large omnivores within a resource-limited ecosystem that are known to exhibit smaller body masses and occur at lower densities than grizzly bears in other regions of North America. We evaluated the energy balance of Arctic grizzly bears during a portion of the fall hyperphagic period in two ecologically differing regions on Alaska’s northern Arctic coast by monitoring mass change, food intake, activity, and energy expenditure of 12 individuals over 17–22 days. Bears in coastal areas were more carnivorous than bears in the foothills that were predominantly herbivorous and frugivorous. Carnivory was associated with greater movement, body fat, and energy expenditure and two of four carnivorous bears lost mass. Overall, the mean body fat of the bears in this study was 34% lower than other grizzly bear populations in North America in the fall. Furthermore, the bears in this study exhibited relatively small changes in body mass (x̄ = 3%, range =−2 to 11%) that were 60% lower than other grizzly bear populations which typically gain substantial mass in the fall in preparation for denning. Our results, while representing a snapshot from a small number of bears during the fall hyperphagic period, are consistent with previous studies and indicate limited availability of energy-dense food resources during this time for grizzly bears in this region of the Arctic.

Alaska↗
USGS2026

Uncertainty quantification of geologic energy storage in depleted gas reservoirs using material balance equations embedded in a hierarchical errors-in-variables model

The storage potential for gas in geologic settings, such as depleted hydrocarbon reservoirs and solution-mined salt caverns, is becoming salient to future energy infrastructure planning. Technologies such as carbon capture, utilization, and storage, carbon dioxide-enhanced oil recovery, and natural gas and hydrogen storage help meet growing energy demands, reduce carbon emissions to meet climate goals, and provide energy security amid geopolitical uncertainties. Therefore, estimates of underground gas storage capacity could be useful for efficiently navigating the energy transitions. Material balance is a fundamental method in reservoir engineering for estimating original gas in place and potential storage capacity at the scale necessary for national assessments of subsurface pore space resources. However, the deterministic method cannot accommodate multiple data sources or quantify uncertainty in predictions. In this study, a method that embeds material balance equations within a hierarchical errors-in-variables model is proposed which allows the estimation of the distributions of reservoir properties needed for assessments. Uncertainties associated with these reservoir properties have traditionally been expert-elicited, whereas the uncertainty estimates from the proposed models are data-driven. Capacity and uncertainty estimates can be used in a probabilistic resource assessment, supplementing information traditionally used by assessors or even replacing this expert elicitation step when data are unavailable. Various regression models are compared in a case study of the Michigan Basin, a large contributor to the United States’ current natural gas storage capacity. In particular, errors-in-variables models help ameliorate regression dilution and can quantify uncertainty in predictions of pressure in addition to storage capacity. Overfitting is addressed by quantifying generalization error and model averaging in simple and stratified cross-validation against reported working gas capacity, representing the varying quality and quantity of available data. Incorporating a statistical framework into existing numerical methods in reservoir engineering can improve the quality of estimation, and in particular, this method brings rigor to uncertainty quantification as part of a larger effort by the U.S. Geological Survey to assess domestic energy gas storage resources in depleted hydrocarbon reservoirs.

Mathematical Geosciences↗