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At least 271 records · Page 15Linked to original sources
USGS1992

Environmental influences on major waterfowl diseases

The decline of North American waterfowl resources since the 1960s is well-known to this audience and need not be detailed to establish that population numbers for several key waterfowl species are at or near their lowest levels since records have been kept. Loss of habitat is an accepted major cause for the decline of waterfowl numbers and the wildlife conservation community is responding with initiatives to prevent further loss of existing wetland acreage, restoration for degraded wetlands and creation of new wetlands. Numerous joint ventures focusing on key waterfowl habitat requirements are being developed under the North American Waterfowl Plan. The importance of habitat loss also is reflected in many of the presentations at this conference on wetland conservation, including one special session devoted solely to that topic. A basic premise of the focus on wetlands is that restoration of waterfowl populations is habitat dependent. This is a tenable thesis if other factors suppressing waterfowl numbers are dealt with and the habitat base being enhanced sustains waterfowl rather than contributes to their death. My presentation addresses disease as a factor suppressing waterfowl numbers and the relation of habitat quantity and quality with waterfowl disease.

Transactions of the North American Wildlife and Na↗
USGS2024

Significant challenges to the sustainability of the California coast considering climate change

Climate change is an existential threat to the environmental and socioeconomic sustainability of the coastal zone and impacts will be complex and widespread. Evidence from California and across the United States shows that climate change is impacting coastal communities and challenging managers with a plethora of stressors already present. Widespread action could be taken that would sustain California’s coastal ecosystems and communities. In this perspective, we highlight the main threat to coastal sustainability: the compound effects of episodic events amplified with ongoing climate change, which will present unprecedented challenges to the state. We present two key challenges for California’s sustainability in the coastal zone: 1) accelerating sea-level rise combined with storm impacts, and 2) continued warming of the oceans and marine heatwaves. Cascading effects from these types of compounding events will occur within the context of an already stressed system that has experienced extensive alterations due to intensive development, resource extraction and harvesting, spatial containment, and other human use pressures. There are critical components that could be used to address these immediate concerns, including comanagement strategies that include diverse groups and organizations, strategic planning integrated across large areas, rapid implementation of solutions, and a cohesive and policy relevant research agenda for the California coast. Much of this has been started in the state, but the scale could be increased, and timelines accelerated. The ideas and information presented here are intended to help expand discussions to sharpen the focus on how to encourage sustainability of California’s iconic coastal region.

California↗
USGS2023

Ancient infrastructure offers sustainable agricultural solutions to dryland farming

For 1000 years, human populations in dryland regions of the North American Southwest (NAS) extensively constructed diverse forms of agricultural infrastructure, including canals, linear rock alignments, check dams, stock ponds, and other earthworks and rock structures. The long-term hydrological impacts of these and the demographic and socio-political drivers of construction and maintenance have yet to be fully documented or vetted. This paper summarizes existing knowledge attained from the United Stated portion of the NAS, but a lot is still unknown about Northwest Mexico. There remain outstanding questions related to understanding how ancient agriculture might improve modern adaptability and resilience. The detailed ecological and topographical variability of this arid landscape illustrates the essential need for infrastructure in maintaining water and managing the impacts of climate change on the hydrological cycle. We describe pros and cons of different types of infrastructure and examine socio-environmental trade-offs between robustness and vulnerability produced by reliance on infrastructure, drawing from existing literature to examine timescales longer than a human lifespan. The development of historically-informed management approaches to increase dryland climate resilience benefits from incorporating constraints and opportunities mediated by past landscape modifications. We present a plan for leveraging existing knowledge, available science, and potential, to extend our knowledge base and further explore causal relationships.

Book chapter↗
USGS1998

Water-quality assessment of the Central Arizona Basins, Arizona and northern Mexico – Environmental setting and overview of water quality

The Central Arizona Basins study area in central and southern Arizona and northern Mexico is one of 60 study units that are part of the U.S. Geological Survey's National Water-Quality Assessment program. The purpose of this report is to describe the physical, chemical, and environmental characteristics that may affect water quality in the Central Arizona Basins study area and present an overview of water quality. Covering 34,700 square miles, the study area is characterized by generally north to northwestward-trending mountain ranges separated by broad, gently sloping alluvial valleys. Most of the perennial rivers and streams are in the northern part of the study area. Rivers and streams in the south are predominantly intermittent or ephemeral and flow in response to precipitation such as summer thunderstorms. Effluent-dependent streams do provide perennial flow in some reaches. The major aquifers in the study area are in the basin-fill deposits that may be as much as 12,000 feet thick. The 1990 population in the study area was about 3.45 million, and about 61 percent of the total was in Maricopa County (Phoenix and surrounding cities). Extensive population growth over the past decade has resulted in a twofold increase in urban land areas and increased municipal water use; however, agriculture remains the major water use. Seventy-three percent of all water with drawn in the study area during 1990 was used for agricultural purposes. The largest rivers in the study area-the Gila, Salt, and Verde-are perennial near their headwaters but become intermittent downstream because of impoundments and artificial diversions. As a result, the Central Arizona Basins study area is unique compared to less arid basins because the mean surface-water outflow is only 528 cubic feet per second from a total drainage area of 49,650 square miles. Peak flows in the northern part of the study area are the result of snowmelt runoff; whereas, summer thunderstorms account for the peak flows in the southern part. Ground water is the primary water supply in most of Arizona and the only source of drinking water used by communities in the southern half of the study area. Years of overpumping have caused water tables in basin fill to drop below once-perennial streams leaving streambeds dry, water too deep to pump economically, pumping of poorer quality water with depth, and earth fissures resulting from subsidence after dewatering of sediments. Natural processes-such as leaching of trace elements and major ions from geologic formations-and human activities-such as mining, agriculture, and urban development-have major effects on the quality of surface-water and ground-water resources in the Central Arizona Basins study area. Surface-water quality standards in Arizona are based on the designated use of the water such as full or partial body contact, fish consumption, aquatic and wildlife uses, and agriculture. Maintaining the biological integrity (health) of surface waters in Arizona is an important part of ensuring that these waters are suitable for designated uses. Important water-quality issues for surface water that are somewhat unique to Arizona include: (1) streamflows and riparian environments sustained by effluent from municipal wastewater-treatment plants that contains high concentrations of nutrients, potentially toxic trace elements and organic compounds, and fecal bacteria; (2) industrial, mining, agricultural, and municipal sources of contamination from Mexico; and (3) unpredictable high flows from major summer thunder storms causing stream-channel changes; high suspended-sediment concentrations and loads; sewage overflows; and breaching, erosion, and washout of landfills and mining operations. The quality of water in aquifers that are protected for drinking- water use is subject to standards that are in most cases equal to or more stringent than the primary drinking-water regulations of the U.S. Environmental Protection Agency. The general che

Arizona↗
USGS2013

Ecological thresholds as a basis for defining management triggers for National Park Service vital signs: case studies for dryland ecosystems

Threshold concepts are used in research and management of ecological systems to describe and interpret abrupt and persistent reorganization of ecosystem properties (Walker and Meyers, 2004; Groffman and others, 2006). Abrupt change, referred to as a threshold crossing, and the progression of reorganization can be triggered by one or more interactive disturbances such as land-use activities and climatic events (Paine and others, 1998). Threshold crossings occur when feedback mechanisms that typically absorb forces of change are replaced with those that promote development of alternative equilibria or states (Suding and others, 2004; Walker and Meyers, 2004; Briske and others, 2008). The alternative states that emerge from a threshold crossing vary and often exhibit reduced ecological integrity and value in terms of management goals relative to the original or reference system. Alternative stable states with some limited residual properties of the original system may develop along the progression after a crossing; an eventual outcome may be the complete loss of pre-threshold properties of the original ecosystem. Reverting to the more desirable reference state through ecological restoration becomes increasingly difficult and expensive along the progression gradient and may eventually become impossible. Ecological threshold concepts have been applied as a heuristic framework and to aid in the management of rangelands (Bestelmeyer, 2006; Briske and others, 2006, 2008), aquatic (Scheffer and others, 1993; Rapport and Whitford 1999), riparian (Stringham and others, 2001; Scott and others, 2005), and forested ecosystems (Allen and others, 2002; Digiovinazzo and others, 2010). These concepts are also topical in ecological restoration (Hobbs and Norton 1996; Whisenant 1999; Suding and others, 2004; King and Hobbs, 2006) and ecosystem sustainability (Herrick, 2000; Chapin and others, 1996; Davenport and others, 1998). Achieving conservation management goals requires the protection of resources within the range of desired conditions (Cook and others, 2010). The goal of conservation management for natural resources in the U.S. National Park System is to maintain native species and habitat unimpaired for the enjoyment of future generations. Achieving this goal requires, in part, early detection of system change and timely implementation of remediation. The recent National Park Service Inventory and Monitoring program (NPS I&M) was established to provide early warning of declining ecosystem conditions relative to a desired native or reference system (Fancy and others, 2009). To be an effective tool for resource protection, monitoring must be designed to alert managers of impending thresholds so that preventive actions can be taken. This requires an understanding of the ecosystem attributes and processes associated with threshold-type behavior; how these attributes and processes become degraded; and how risks of degradation vary among ecosystems and in relation to environmental factors such as soil properties, climatic conditions, and exposure to stressors. In general, the utility of the threshold concept for long-term monitoring depends on the ability of scientists and managers to detect, predict, and prevent the occurrence of threshold crossings associated with persistent, undesirable shifts among ecosystem states (Briske and others, 2006). Because of the scientific challenges associated with understanding these factors, the application of threshold concepts to monitoring designs has been very limited to date (Groffman and others, 2006). As a case in point, the monitoring efforts across the 32 NPS I&M networks were largely designed with the knowledge that they would not be used to their full potential until the development of a systematic method for understanding threshold dynamics and methods for estimating key attributes of threshold crossings. This report describes and demonstrates a generalized approach that we implemented to formalize understanding and estimating of threshold dynamics for terrestrial dryland ecosystems in national parks of the Colorado Plateau. We provide a structured approach to identify and describe degradation processes associated with threshold behavior and to estimate indicator levels that characterize the point at which a threshold crossing has occurred or is imminent (tipping points) or points where investigative or preventive management action should be triggered (assessment points). We illustrate this method for several case studies in national parks included in the Northern and Southern Colorado Plateau NPS I&M networks, where historical livestock grazing, climatic change, and invasive species are key agents of change. The approaches developed in these case studies are intended to enhance the design, effectiveness, and management-relevance of monitoring efforts in support of conservation management in dryland systems. They specifically enhance National Park Service (NPS) capacity for protecting park resources on the Colorado Plateau but have applicability to monitoring and conservation management of dryland ecosystems worldwide.

Colorado Plateau↗
USGS2018

Development of a species status assessment process for decisions under the U.S. Endangered Species Act

Decisions under the U.S. Endangered Species Act (ESA) require scientific input on the risk that the species will become extinct. A series of critiques on the role of science in ESA decisions have called for improved consistency and transparency in species risk assessments and clear distinctions between science input and policy application. To address the critiques and document the emerging practice of the U.S. Fish and Wildlife Service (USFWS), we outline an assessment process based on principles and practices of risk and decision analyses that results in a scientific report on species status. The species status assessment (SSA) process has three successive stages: 1) document the life history and ecological relationships of the species in question to provide the foundation for the assessment, 2) describe and hypothesize causes for the current condition of the species, and 3) forecast the species' future condition. The future condition refers to the ability of a species to sustain populations in the wild under plausible future scenarios. The scenarios help explore the species' response to future environmental stressors and to assess the potential for conservation to intervene to improve its status. The SSA process incorporates modeling and scenario planning for prediction of extinction risk and applies the conservation biology principles of representation, resiliency, and redundancy to evaluate the current and future condition. The SSA results in a scientific report distinct from policy application, which contributes to streamlined, transparent, and consistent decision-making and allows for greater technical participation by experts outside of the USFWS, for example, by state natural resource agencies. We present two case studies based on assessments of the eastern massasauga rattlesnake Sistrurus catenatus and the Sonoran Desert tortoise Gopherus morafkai to illustrate the process. The SSA builds upon the past threat-focused assessment by including systematic and explicit analyses of a species' future response to stressors and conservation, and as a result, we believe it provides an improved scientific analysis for ESA decisions.

Journal of Fish and Wildlife Management↗
USGS2017

Earth Stewardship: An initiative by the Ecological Society of America to foster engagement to sustain Planet Earth

The Ecological Society of America (ESA) has responded to the growing commitment among ecologists to make their science relevant to society through a series of concerted efforts, including the Sustainable Biosphere Initiative (1991), scientific assessment of ecosystem management (1996), ESA’s vision for the future (2003), Rapid Response Teams that respond to environmental crises (2005), and the Earth Stewardship Initiative (2009). During the past 25 years, ESA launched five new journals, largely reflecting the expansion of scholarship linking ecology with broader societal issues. The goal of the Earth Stewardship Initiative is to raise awareness and to explore ways for ecologists and other scientists to contribute more effectively to the sustainability of our planet. This has occurred through four approaches: (1) articulation of the stewardship concept in ESA publications and Website, (2) selection of meeting themes and symposia, (3) engagement of ESA sections in implementing the initiative, and (4) outreach beyond ecology through collaborations and demonstration projects. Collaborations include societies and groups of Earth and social scientists, practitioners and policy makers, religious and business leaders, federal agencies, and artists and writers. The Earth Stewardship Initiative is a work in progress, so next steps likely include continued nurturing of these emerging collaborations, advancing the development of sustainability and stewardship theory, improving communication of stewardship science, and identifying opportunities for scientists and civil society to take actions that move the Earth toward a more sustainable trajectory.

Book chapter↗
USGS2022

Long-term assessments are critical to determining persistence and shoreline protection from oyster reef nature-based coastal defenses

Nature-based coastal defense using bivalve reefs provides a potentially self-sustaining approach for regions facing high coastal land loss, relative sea level rise and increasing frequency and intensity of storms. Success of such nature-based coastal defense depends on the reef-building species' life history, habitat requirements, and ability to thrive through short-term and longer-term environmental variation, yet few projects have reported on outcomes beyond the first few years. In coastal Louisiana, USA, Crassostrea virginica (oyster) is an ecosystem engineer, creating self-sustaining, vertically accreting reefs that also provide ecosystem services. Here, we examine the short (< 3 years) and medium (> 10 years) term outcomes of experimental reefs constructed in 2009 for nature-based coastal defense in a Louisiana, USA estuarine lake. Oyster reef density, demography, along with adjacent salt marsh, and shoreline movement were compared at six fringing shoreline reefs and paired reference sites over the first three years post-construction (2009–2011), and a decade later (2019–2020). Oyster density measured in 2019–2020 (< 60 ind m −2 ) was less than 10% of density measured during 2009–2011 (> 1000 ind m −2 ). This density difference largely reflected a lack of new recruits and small oysters (< 75 mm shell height) in later samples, with adult oyster densities similar between 2011, 2019 and 2020. Lack of smaller oysters in recent sampling likely reflected the impact of multiple extended low salinity events in this region in recent years, including the record-breaking low salinity in 2019. No differences in shoreline characteristics were detected in marsh vegetation, soil properties or nutrient concentrations between reef and reference sites during early and later years. Similarly, shoreline erosion at both reef and reference sites immediately post-construction, and 10 years later, was high (~1 m y −1 ) indicating a lack of shoreline protection from these reefs. These findings highlight the need to consider both current and future conditions, including the effect of extreme years, when implementing nature-based coastal defense. On the other hand, the persistence of reproductive-sized oysters on the reef 10 years post creation, indicate reef resilience and potential for reef development and shoreline benefits, should better site conditions return in future years. Determining restoration success within variable and dynamic environments requires frequent monitoring which is required to understand responses to short and longer-term environmental variation.

Louisiana↗
USGS2010

Preliminary assessment of factors influencing riverine fish communities in Massachusetts

The U.S. Geological Survey, in cooperation with the Massachusetts Department of Conservation and Recreation (MDCR), Massachusetts Department of Environmental Protection (MDEP), and the Massachusetts Department of Fish and Game (MDFG), conducted a preliminary investigation of fish communities in small- to medium-sized Massachusetts streams. The objective of this investigation was to determine relations between fish-community characteristics and anthropogenic alteration, including flow alteration and impervious cover, relative to the effect of physical basin and land-cover (environmental) characteristics. Fish data were obtained for 756 fish-sampling sites from the Massachusetts Division of Fisheries and Wildlife fish-community database. A review of the literature was used to select a set of fish metrics responsive to flow alteration. Fish metrics tested include two fish-community metrics (fluvial-fish relative abundance and fluvial-fish species richness), and five indicator species metrics (relative abundance of brook trout, blacknose dace, fallfish, white sucker, and redfin pickerel). Streamflows were simulated for each fish-sampling site using the Sustainable Yield Estimator application (SYE). Daily streamflows and the SYE water-use database were used to determine a set of indicators of flow alteration, including percent alteration of August median flow, water-use intensity, and withdrawal and return-flow fraction. The contributing areas to the fish-sampling sites were delineated and used with a Geographic Information System (GIS) to determine a set of environmental characteristics, including elevation, basin slope, percent sand and gravel, percent wetland, and percent open water, and a set of anthropogenic-alteration variables, including impervious cover and dam density. Two analytical techniques, quantile regression and generalized linear modeling, were applied to determine the association between fish-response variables and the selected environmental and anthropogenic explanatory variables. Quantile regression indicated that flow alteration and impervious cover were negatively associated with both fluvial-fish relative abundance and fluvial-fish species richness. Three generalized linear models (GLMs) were developed to quantify the response of fish communities to multiple environmental and anthropogenic variables. Flow-alteration variables are statistically significant for the fluvial-fish relative-abundance model. Impervious cover is statistically significant for the fluvial-fish relative-abundance, fluvial-fish species richness, and brook trout relative-abundance models. The variables in the equations were demonstrated to be significant, and the variability explained by the models, as measured by the correlation between observed and predicted values, ranges from 39 to 65 percent. The GLM models indicated that, keeping all other variables the same, a one-unit (1 percent) increase in the percent depletion or percent surcharging of August median flow would result in a 0.4-percent decrease in the relative abundance (in counts per hour) of fluvial fish and that the relative abundance of fluvial fish was expected to be about 55 percent lower in net-depleted streams than in net-surcharged streams. The GLM models also indicated that a unit increase in impervious cover resulted in a 5.5-percent decrease in the relative abundance of fluvial fish and a 2.5-percent decrease in fluvial-fish species richness.

Massachusetts↗
USGS2021

Temporal influences on selenium partitioning, trophic transfer, and exposure in a major U.S. river

Hydrologic and irrigation regimes mediate the timing of selenium (Se) mobilization to rivers, but the extent to which patterns in Se uptake and trophic transfer through recipient food webs reflect the temporal variation in Se delivery is unknown. We investigated Se mobilization, partitioning, and trophic transfer along approximately 60 river miles of the selenium-impaired segment of the Lower Gunnison River (Colorado, USA) during six sampling trips between June 2015 and October 2016. We found temporal patterns in Se partitioning and trophic transfer to be independent of those in dissolved Se concentrations and that the recipient food web sustained elevated Se concentrations from earlier periods of high Se mobilization. Using an ecosystem-scale Se accumulation model tailored to the Lower Gunnison River, we predicted that the endangered Razorback Sucker ( Xyrauchen texanus ) and Colorado Pikeminnow ( Ptychocheilus lucius ) achieve whole-body Se concentrations exceeding aquatic life protection criteria during periods of high runoff and irrigation activity (April–August) that coincide with susceptible phases of reproduction and early-life development. The results of this study challenge assumptions about Se trophodynamics in fast-flowing waters and introduce important considerations for the management of Se risks for biota in river ecosystems.

Colorado↗
USGS2013

U.S. Geological Survey Energy and Minerals science strategy: A resource lifecycle approach

Executive Summary The economy, national security, and standard of living of the United States depend heavily on adequate and reliable supplies of energy and mineral resources. Based on population and consumption trends, the Nation’s use of energy and minerals can be expected to grow, driving the demand for ever broader scientific understanding of resource formation, location, and availability. In addition, the increasing importance of environmental stewardship, human health, and sustainable growth places further emphasis on energy and mineral resources research and understanding. Collectively, these trends in resource demand and the interconnectedness among resources will lead to new challenges and, in turn, require cutting-edge science for the next generation of societal decisions. The long and continuing history of U.S. Geological Survey contributions to energy and mineral resources science provide a solid foundation of core capabilities upon which new research directions can grow. This science strategy provides a framework for the coming decade that capitalizes on the growth of core capabilities and leverages their application toward new or emerging challenges in energy and mineral resources research, as reflected in five interrelated goals. Goal 1.—Understand fundamental Earth processes that form energy and mineral resources Goal 2.—Understand the environmental behavior of energy and mineral resources and their waste products Goal 3.—Provide inventories and assessments of energy and mineral resources Goal 4.—Understand the effects of energy and mineral development on natural resources and society Goal 5.—Understand the reliability and availability of energy and mineral supplies Within each goal, multiple actions are identified. The level of specificity and complexity of these actions varies, consistent with the reality that even a modest refocus can yield large payoffs in the near term whereas more ambitious plans may take years to reach fruition. As such, implementation of these actions is largely dependent on available resources and the sequencing of prerequisite steps. This science strategy places an emphasis on interdisciplinary collaboration and leveraging of expertise across the U.S. Geological Survey and with external partners.

Circular↗
USGS2022

Bright spots for inland fish and fisheries to guide future hydropower development

Hydropower production is one of the greatest threats to fluvial ecosystems and freshwater biodiversity. Now that we have entered the Anthropocene , there is an opportunity to reflect on what might constitute a ‘sustainable’ Anthropocene in the context of hydropower and riverine fish populations. Considering elements of existing practices that promote favorable social-ecological outcomes (i.e., ‘bright spots’) is timely given that there are plans to expand hydropower capacity in previously undammed rivers, intensify dam development in some of the world's largest river systems, and re-license existing facilities. We approach this from a pragmatic perspective: for the foreseeable future, hydropower will likely remain an important source of renewable electricity. To offer support for moving toward a more ‘sustainable’ Anthropocene, we provide syntheses of best practices during the siting, design, construction, operation, and compensation phases of hydropower development to minimize impacts on inland fish. For each phase, we offer positive examples (or what might be considered ‘bright spots’) pertaining to some of the approaches described within our syntheses, acknowledging that these projects may not be viewed as without ecological and (or) societal detriment by all stakeholders. Our findings underscore the importance of protecting critical habitat and free-flowing river reaches through careful site selection and basin-scale planning, infrastructure designs that minimize reservoir effects and facilitate safe passage of fish, construction of hydropower plants using best practices that minimize long-term damage, operating guidelines that mimic natural flow conditions, and compensation that is lasting, effective, inclusive, and locally relevant. Learning from these ‘bright spots’ may require engagement of diverse stakeholders, professionals, and governments at scales that extend well beyond a given site, river, or even basin. Indeed, environmental planning that integrates hydropower development into broader discussions of conserving regional biodiversity and ecosystem services will be of utmost importance.

Water Biology and Security↗
USGS2021

Decision-support framework for linking regional-scale management actions to continental-scale conservation of wide-ranging species

Anas acuta (Northern pintail; hereafter pintail) was selected as a model species on which to base a decision-support framework linking regional actions to continental-scale population and harvest objectives. This framework was then used to engage stakeholders, such as Landscape Conservation Cooperatives’ (LCCs’) habitat management partners within areas of importance to pintails, while maximizing cross-taxa effects from the framework. The mathematical framework for the model had been previously developed for pintails. A key assumption incorporated into the model is that density dependence in survival occurs during the post-hunting (winter) period, where resources are hypothesized to be limiting. Because few data are available to directly inform this process, the approach used was to build a hierarchical Bayesian integrated population model (IPM) that simultaneously uses data from bird-band recoveries, breeding population counts, and harvest surveys to estimate values of parameters of an annual population projection model, including population size, survival rate, reproductive rate, and process and observation error variances, that are logically consistent with each other, given the mathematical structure imposed through the IPM. The main accomplishments of this study are (1) development of an IPM for pintail to guide harvest and habitat management, (2) development of a Prairie Parkland Region breeding submodel to predict pintail productivity, (3) development of statistical methodology to estimate pintail productivity (as measured by the ratio of juvenile to adults in hunter-collected wing samples) and winter survival and to relate these estimates to covariates, and (4) illustration of how to use a model and estimated parameter values to predict pintail population size and sustainable harvest as a function of habitat. Estimation of pintail survival from bird-banding data shows that there has been relatively little variation in survival over the period 1960–2013. A productivity model showed strong effects of breeding ground conditions, wintering-ground precipitation, and density dependence on pintail productivity. Thus, most temporal variation in pintail demographic rates has been due to effects on reproduction and not survival, including effects of breeding or wintering-ground habitat. These results indicate that habitat conservation efforts may be most effective if they focus on maintaining or increasing breeding and wintering-ground habitat to increase pintail productivity rather than pintail survival. Environmental perturbations in excess of historical experience, such as what could occur under climate change, might have meaningful effects on survival but cannot be estimated with current data. Direct effects of climate, land use, or management are likely to be greater on productivity than survival, but substantial uncertainty remains about predictions of equilibrium population size and sustainable yield.

Open-File Report↗
USGS2021

Incorporating climate change in a harvest risk assessment for polar bears Ursus maritimus in Southern Hudson Bay

Arctic marine mammals are harvested by Indigenous people for subsistence and are socially and culturally important. For ice-dependent species like the polar bear Ursus maritimus , management and conservation require understanding interactions between harvest and sea-ice loss due to climate change. We developed a demographic model to evaluate harvest risk for polar bears in Southern Hudson Bay, Canada, where the annual ice-free season has increased by approximately one month in recent decades. The model was based on the theta-logistic equation and allowed for density-dependent changes (through carrying capacity [ K ]) and density-independent changes (through population growth rate [ r ]). Model parameters were estimated using a Bayesian Monte Carlo method that included capture-recapture, aerial survey, and harvest data. Harvest management followed a state-dependent approach under which new estimates of abundance were used to update the harvest level every five years. Under a middle-of-the-road environmental scenario that assumed K and r would decline in proportion to projected sea-ice declines, annual removal of 0.02–0.03 of females resulted in a 0.8 probability of maintaining subpopulation abundance above maximum net productivity level for three polar bear generations (~34 years), our primary criterion for sustainability. Under more pessimistic and optimistic environmental scenarios, comparable female harvest rates were 0.01 and 0.055, respectively. Our coupled modeling-management framework can be used to inform tradeoffs between protection and sustainable use for wildlife populations experiencing habitat loss.

Southern Hudson Bay↗
USGS2009

Application of the Hydroecological Integrity Assessment Process for Missouri Streams

Natural flow regime concepts and theories have established the justification for maintaining or restoring the range of natural hydrologic variability so that physiochemical processes, native biodiversity, and the evolutionary potential of aquatic and riparian assemblages can be sustained. A synthesis of recent research advances in hydroecology, coupled with stream classification using hydroecologically relevant indices, has produced the Hydroecological Integrity Assessment Process (HIP). HIP consists of (1) a regional classification of streams into hydrologic stream types based on flow data from long-term gaging-station records for relatively unmodified streams, (2) an identification of stream-type specific indices that address 11 subcomponents of the flow regime, (3) an ability to establish environmental flow standards, (4) an evaluation of hydrologic alteration, and (5) a capacity to conduct alternative analyses. The process starts with the identification of a hydrologic baseline (reference condition) for selected locations, uses flow data from a stream-gage network, and proceeds to classify streams into hydrologic stream types. Concurrently, the analysis identifies a set of non-redundant and ecologically relevant hydrologic indices for 11 subcomponents of flow for each stream type. Furthermore, regional hydrologic models for synthesizing flow conditions across a region and the development of flow-ecology response relations for each stream type can be added to further enhance the process. The application of HIP to Missouri streams identified five stream types ((1) intermittent, (2) perennial runoff-flashy, (3) perennial runoff-moderate baseflow, (4) perennial groundwater-stable, and (5) perennial groundwater-super stable). Two Missouri-specific computer software programs were developed: (1) a Missouri Hydrologic Assessment Tool (MOHAT) which is used to establish a hydrologic baseline, provide options for setting environmental flow standards, and compare past and proposed hydrologic alterations; and (2) a Missouri Stream Classification Tool (MOSCT) designed for placing previously unclassified streams into one of the five pre-defined stream types.

Open-File Report↗
USGS2013

Development of a stock-recruitment model and assessment of biological reference points for the Lake Erie walleye fishery

We developed an updated stock–recruitment relationship for Lake Erie Walleye Sander vitreus using the Akaike information criterion model selection approach. Our best stock–recruitment relationship was a Ricker spawner–recruit function to which spring warming rate was added as an environmental variable, and this regression model explained 39% of the variability in Walleye recruitment over the 1978 through 2006 year-classes. Thus, most of the variability in Lake Erie Walleye recruitment appeared to be attributable to factors other than spawning stock size and spring warming rate. The abundance of age-0 Gizzard Shad Dorosoma cepedianum, which was an important term in previous models, may still be an important factor for Walleye recruitment, but poorer ability to monitor Gizzard Shad since the late 1990s could have led to that term failing to appear in our best model. Secondly, we used numerical simulation to demonstrate how to use the stock recruitment relationship to characterize the population dynamics (such as stable age structure, carrying capacity, and maximum sustainable yield) and some biological reference points (such as fishing rates at different important biomass or harvest levels) for an age-structured population in a deterministic way.

North American Journal of Fisheries Management↗
USGS1998

Recharge-area delineation and hydrology, McCraken Springs, Fort Knox Military Reservation, Meade County, Kentucky

McCraken Springs, consisting of three perennial springs - Main, Bat Cave, and Rocky Springs—and several intermittent springs, are used as a source of public water by the Fort Knox Military Reservation in Meade County, Ky. The water supply provided by McCraken Springs is potentially vulnerable to natural and induced stresses on the karst aquifer and to degradation by contaminants introduced by stormwater entering sinkholes and a large sinking stream in the Springs' recharge area. The U.S. Department of the Army is preparing a spring-basin protection plan for McCraken Springs, in accordance with State water-supply regulations and as specified under U.S. Environmental Protection Agency Guidelines for the Wellhead Protection Program (U.S. Environmental Protection Agency, 1991). In order to provide the information needed to prepare the plan, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, conducted a hydrogeologic study of the McCraken Springs in 1997-98. This report presents the results of that investigation. Ground-water-tracer tests and the results of potentiometric-surface mapping were used to identify ground-water basins drained by major perennial springs and to delineate the approximate boundaries of the recharge area for McCraken Springs. Additional hydrologic data were collected to determine the discharge and recharge characteristics of the Springs. Karst aquifers and springs are widely recognized as being more sensitive to degradation to point- and nonpoint-source contamination than most granular and fractured-rock aquifers (Field, 1990). Delineation of the geographic area contributing recharge to a water-supply spring is a principal step in identifying potential sources of ground-water contamination and developing a strategy to ensure the availability and protect the sustainability of the water supply. Conventional methods of aquifer testing and numerical modeling are not sufficient to determine the flow boundaries of ground-water basins in conduit-dominated karst aquifers. Previous studies published by Quinlan and Ewers (1989); Mull and others (1990); Bayless and others (1994); and Schindel and others (1995) demonstrate the utility of ground-water tracer tests, used in combination with potentiometric-surface mapping, to identify flow directions in karst aquifers, and to delineate karst ground-water-basin boundaries.

Kentucky↗
USGS2009

Simulations of Groundwater Flow and Particle Tracking Analysis in the Area Contributing Recharge to a Public-Supply Well near Tampa, Florida, 2002-05

Shallow ground water in the north-central Tampa Bay region, Florida, is affected by elevated nitrate concentrations, the presence of volatile organic compounds, and pesticides as a result of groundwater development and intensive urban land use. The region relies primarily on groundwater for drinking-water supplies. Sustainability of groundwater quality for public supply requires monitoring and understanding of the mechanisms controlling the vulnerability of public-supply wells to contamination. A single public-supply well was selected for intensive study based on the need to evaluate the dominant processes affecting the vulnerability of public-supply wells in the Upper Floridan aquifer in the City of Temple Terrace near Tampa, Florida, and the presence of a variety of chemical constituents in water from the well. A network of 29 monitoring wells was installed, and water and sediment samples were collected within the area contributing recharge to the selected public-supply well to support a detailed analysis of physical and chemical conditions and processes affecting the water chemistry in the well. A three-dimensional, steady-state groundwater flow model was developed to evaluate the age of groundwater reaching the well and to test hypotheses on the vulnerability of the well to nonpoint source input of nitrate. Particle tracking data were used to calculate environmental tracer concentrations of tritium and sulfur hexafluoride and to calibrate traveltimes and compute flow paths and advective travel times in the model area. The traveltime of particles reaching the selected public-supply well ranged from less than 1 day to 127.0 years, with a median of 13.1 years; nearly 45 percent of the simulated particle ages were less than about 10 years. Nitrate concentrations, derived primarily from residential/commercial fertilizer use and atmospheric deposition, were highest (2.4 and 6.11 milligrams per liter as nitrogen, median and maximum, respectively) in shallow groundwater from the surficial aquifer system and lowest (less than the detection level of 0.06 milligram per liter) in the deeper Upper Floridan aquifer. Denitrification occurred near the interface of the surficial aquifer system and the underlying intermediate confining unit, within the intermediate confining unit, and within the Upper Floridan aquifer because of reducing conditions in this part of the flow system. However, simulations indicate that the rapid movement of water from the surficial aquifer system to the selected public-supply well through karst features (sinkholes) and conduit layers that bypass the denitrifying zones (short-circuits), coupled with high pumping rates, allow nitrate to reach the selected public-supply well in concentrations that resemble those of the overlying surficial aquifer system. Water from the surficial aquifer system with elevated concentrations of nitrate and low concentrations of some volatile organic compounds and pesticides is expected to continue moving into the selected public-supply well, because calculated flux-weighted concentrations indicate the proportion of young affected water contributing to the well is likely to remain relatively stable over time. The calculated nitrate concentration in the selected public-supply well indicates a lag of 1 to 10 years between peak concentrations of nonpoint source contaminants in recharge and appearance in the well.

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