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At least 307 records · Page 17Linked to original sources
USGS2022

Potential cheatgrass abundance within lightly invaded areas of the Great Basin

Context Anticipating where an invasive species could become abundant can help guide prevention and control efforts aimed at reducing invasion impacts. Information on potential abundance can be combined with information on the current status of an invasion to guide management towards currently uninvaded locations where the threat of invasion is high. Objectives We aimed to support management by developing predictive maps of potential cover for cheatgrass ( Bromus tectorum ), a problematic invader that can transform plant communities. We integrated our predictions of potential abundance with mapped estimates of current cover to quantify invasion potential within lightly invaded areas. Methods We used quantile regression to model cheatgrass abundance as a function of climate, weather, and disturbance, treating outputs as low to high invasion scenarios. We developed a species-specific set of covariates and validated model performance using spatially and temporally independent data. Results Potential cheatgrass abundance was higher in areas that had burned, at low elevations, and when fall germination conditions were more favorable. Our results highlight the extensive areas across the Great Basin where cheatgrass abundance could increase to levels that can alter fire behavior and cause other ecological impacts. Conclusions We predict potential cheatgrass abundance to quantify relative invasion risk. Our model results provide high and low scenarios of cheatgrass abundance to guide resource allocation and planning efforts across shrubland ecosystems of the Great Basin that remain relatively uninvaded. Combining information on an invasive species’ current and potential abundance can yield spatial predictions to guide resource allocation and management action.

California, Idaho, Nevada, Oregon, Utah↗
USGS2020

Contemporary fire regimes provide a critical perspective on restoration needs in the Mexico-United States borderlands

The relationship between people and wildfire has always been paradoxical: fire is an essential ecological process and management tool, but can also be detrimental to life and property. Consequently, fire regimes have been modified throughout history through both intentional burning to promote benefits and active suppression to reduce risks. Reintroducing fire and its benefits back into the Sky Island mountains of the United States-Mexico borderlands has the potential to reduce adverse effects of altered fire regimes and build resilient ecosystems and human communities. To help guide regional fire restoration, we describe the frequency and severity of recent fires over a 32-year period (1985-2017) across a vast binational region in the United States-Mexico borderlands and assess variation in fire frequency and severity across climate gradients and in relation to vegetation and land tenure classes. We synthesize relevant literature on historical fire regimes within 9 major vegetation types and assess how observed contemporary fire characteristics vary from expectations based on historical patterns. Less than 28% of the study area burned during the observation period, excluding vegetation types in warmer climates that are not adapted to fire (eg, Desertscrub and Thornscrub). Average severity of recent fires was low despite some extreme outliers in cooler, wetter environments. Midway along regional temperature and precipitation gradients, approximately 64% of Pine-Oak Forests burned at least once, with fire frequencies that mainly corresponded to historical expectations on private lands in Mexico but less so on communal lands, suggesting the influence of land management. Fire frequency was higher than historical expectations in extremely cool and wet environments that support forest types such as Spruce-Fir, indicating threats to these systems possibly attributable to drought and other factors. In contrast, fires were absent or infrequent across large areas of Woodlands (~73% unburned) and Grasslands (~88% unburned) due possibly to overgrazing, which reduces abundance and continuity of fine fuels needed to carry fire. Our findings provide a new depiction of fire regimes in the Sky Islands that can help inform fire management, restoration, and regional conservation planning, fostered by local and traditional knowledge and collaboration among landowners and managers.

Arizona, Sonora↗
USGS2022

Human and ecosystem health in coastal systems

U.S. coastal economies and communities are facing an unprecedented and growing number of impacts to coastal ecosystems including beach and fishery closures, harmful algal blooms, loss of critical habitat, as well as shoreline damage. This paper synthesizes our present understanding of the dynamics of human and ecosystem health in coastal systems with a focus on the need to better understand nearshore physical process interactions with coastal pollutants and ecosystems (e.g. fate and transport, circulation, depositional environment, climate change). It is organized around two major topical areas and six subtopic areas: 1) Identifying and mitigating coastal pollutants, including fecal pollution, nutrients and harmful algal blooms, and microplastics; and 2) Resilient coastal ecosystems, which focuses on coastal fisheries, shellfish and natural and nature-based features (NNBF). Societal needs and the tools and technologies needed to address them are discussed for each subtopic. Recommendations for scientific research, observations, community engagement, and policies aim to help prioritize future research and investments. A better understanding of coastal physical processes and interactions with coastal pollutants and resilient ecosystems (e.g. fate and transport, circulation, depositional environment, climate change) is a critical need. Other research recommendations include the need to quantify potential threats to human and ecosystem health through accurate risk assessments and to quantify the resulting hazard risk reduction of natural and nature-based features; improve pollutant and ecosystem impacts forecasting by integrating frequent and new data points into existing and novel models; collect environmental data to calibrate and validate models to predict future impacts on coastal ecosystems and their evolution due to anthropogenic stressors (land-based pollution, overfishing, coastal development), climate change, and sea level rise; and develop lower cost and rapid response tools to help coastal managers better respond to pollutant and ecosystem threats.

Shore and Beach↗
USGS2024

Assessing the sustainability of Pacific walrus harvest in a changing environment

Harvest sustainability is a primary goal of wildlife management and conservation, and in a changing world, it is increasingly important to consider environmental drivers of population dynamics alongside harvest in cohesive management plans. This is particularly pertinent for harvested species that acutely experience effects of climate change. The Pacific walrus ( Odobenus rosmarus divergens ), a crucial subsistence resource for Indigenous communities, is simultaneously subject to rapid habitat loss associated with diminishing sea ice and an increasing anthropogenic footprint in the Arctic. We developed a theta-logistic population modeling-management framework to evaluate various harvest scenarios combined with 4 potential climate and disturbance scenarios (ranging from optimistic to pessimistic, based largely on sea ice projections from general circulation models) to simulate Pacific walrus population dynamics to the end of the twenty-first century, focusing on the independent-aged female subset of the population. We considered 2 types of harvest strategies: 1) state-dependent harvest scenarios wherein we calculated harvest as a percentage of the population and updated annual harvests at set intervals as the population was reassessed, and 2) annually consistent harvest scenarios wherein annual harvest levels remain consistent into the future. All climate and disturbance scenarios indicated declines of varying severity in Pacific walrus abundance to the end of the twenty-first century, even in the absence of harvest. However, we found that a state-dependent annual harvest of 1.23% of the independent-aged female subset of the population (e.g., 1,280 independent-aged females harvested in 2020, similar to contemporary harvest levels) met our criterion for sustainability under all climate and disturbance scenarios, considering a medium risk tolerance level of 25%. This indicates that the present rate of Pacific walrus harvest is sustainable and will continue to be—provided the population is assessed at regular intervals and harvest is adapted to match changes in population dynamics. Our simulations indicate that a sustainable annually-consistent harvest is also possible but only at low levels if the population declines as expected. Applying a constant annual harvest of 1,280 independent-aged females failed to meet our criterion for sustainability under 3 of the 4 climate and disturbance scenarios we evaluated and had a higher probability of quasi-extinction than an equivalent state-dependent harvest scenario (1.23%). We highlight the importance of state-dependent management strategies and suggest our modeling framework is useful for managing harvest sustainability in a changing climate.

Journal of Wildlife Management↗
USGS2016

Vulnerabilities of national parks in the American Midwest to climate and land use changes

Many national parks in the American Midwest are surrounded by agricultural or urban areas or are in highly fragmented or rapidly changing landscapes. An environmental stressor is a physical, chemical, or biological condition that affects the functioning or productivity of species or ecosystems. Climate change is just one of many stressors on park natural resources; others include urbanization, land use change, air and water pollution, and so on. Understanding and comparing the relative vulnerability of a suite of parks to projected climate and land use changes is important for region-wide planning. A vulnerability assessment of 60 units in the 13-state U.S. National Park Service Midwestern administrative region to climate and land use change used existing data from multiple sources. Assessment included three components: individual park exposure (5 metrics), sensitivity (5 metrics), and constraints to adaptive capacity (8 metrics) under 2 future climate scenarios. The three components were combined into an overall vulnerability score. Metrics were measures of existing or projected conditions within park boundaries, within 10-kilometer buffers surrounding parks, and within ecoregions that contain or intersect them. Data were normalized within the range of values for all assessed parks, resulting in high, medium, and low relative rankings for exposure, sensitivity, constraints to adaptive capacity, and overall vulnerability. Results are consistent with assessments regarding patterns and rates of climate change nationwide but provide greater detail and relative risk for Midwestern parks. Park overall relative vulnerability did not differ between climate scenarios. Rankings for exposure, sensitivity, and constraints to adaptive capacity varied geographically and indicate regional conservation planning opportunities. The most important stressors for the most vulnerable Midwestern parks are those related to sensitivity (intrinsic characteristics of the park) and constraints on adaptive capacity (characteristics of the surrounding landscape) rather than exposure to external forces, including climate change. Output will allow individual park managers to understand which metrics weigh most heavily in the overall vulnerability of their park and can be used for region-wide responses and resource allocation for adaptation efforts.

Arkansas, Illinois, Indiana, Iowa, Kansas, Michiga↗
USGS2014

Ecological consequences of the expansion of N 2 -fixing plants in cold biomes

Research in warm-climate biomes has shown that invasion by symbiotic dinitrogen (N 2 )-fixing plants can transform ecosystems in ways analogous to the transformations observed as a consequence of anthropogenic, atmospheric nitrogen (N) deposition: declines in biodiversity, soil acidification, and alterations to carbon and nutrient cycling, including increased N losses through nitrate leaching and emissions of the powerful greenhouse gas nitrous oxide (N 2 O). Here, we used literature review and case study approaches to assess the evidence for similar transformations in cold-climate ecosystems of the boreal, subarctic and upper montane-temperate life zones. Our assessment focuses on the plant genera Lupinus and Alnus , which have become invasive largely as a consequence of deliberate introductions and/or reduced land management. These cold biomes are commonly located in remote areas with low anthropogenic N inputs, and the environmental impacts of N 2 -fixer invasion appear to be as severe as those from anthropogenic N deposition in highly N polluted areas. Hence, inputs of N from N 2 fixation can affect ecosystems as dramatically or even more strongly than N inputs from atmospheric deposition, and biomes in cold climates represent no exception with regard to the risk of being invaded by N 2 -fixing species. In particular, the cold biomes studied here show both a strong potential to be transformed by N 2 -fixing plants and a rapid subsequent saturation in the ecosystem’s capacity to retain N. Therefore, analogous to increases in N deposition, N 2 -fixing plant invasions must be deemed significant threats to biodiversity and to environmental quality.

Oecologia↗
USGS2002

Research plan for lands administered by the U.S. Department of the Interior in the Interior Columbia Basin and Snake River Plateau

This document presents a long-term research strategy designed to address current and future research needs for management of Department of the Interior-administered ecosystems in the Intermountain West. Although the research plan was developed in the context of the Interior Columbia Basin Ecosystem Management Project, the plan addresses many high-priority issues facing land managers throughout the Intermountain West. These issues pose management challenges that may be addressed with applied research both currently and in upcoming decades. Possessing a particular focus on semiarid ecosystems, the plan is a collection of research questions under five categories of research emphases: 1) restoration; 2) rangeland health; 3) aquatic-terrestrial connections; 4) development of monitoring and evaluation protocols; and 5) species and habitats at risk. The goal of the research strategy is to provide ideas for integrating emerging scientific understanding into future management in order to restore and maintain long-term ecosystem health and ecological integrity; provide consistent management direction over broad spatial and temporal scales; emphasize adaptive management over the long term; restore and maintain habitats for plant and animal species; and support economic and social needs of people, without compromising the above goals. Research questions are prioritized into three categories based on the immediacy of their need, feasibility of addressing the question rigorously under varying funding budgets, and magnitude of risk posed by not addressing the issue. The research strategy is intended to support and integrate with existing management efforts and strategies. As such, it melds observational studies with experimental manipulation, treating management actions as experiments whenever feasible. The research strategy focuses on disturbance processes and events that have been the primary drivers of change, to provide a predictive model for future changes. These drivers include fire, nonnative plants, herbivory, roads and associated human influences, and climate change. Whereas management in the western United States has striven to move from an inefficient species-based approach to a habitat-based approach, the plan focuses on ecosystem function and ecological processes as critical measures of habitat response. Because of the large amount and contiguity of public lands in the western United States, the region presents both a compelling opportunity to implement landscape-level science and a challenge to underst

Information and Technology Report↗
USGS2020

Temporospatial shifts in Sandhill Crane staging in the Central Platte River Valley in response to climatic variation and habitat change

Over 80% of the Mid-Continent Sandhill Crane ( Antigone canadensis ) Population (MCP), estimated at over 660,000 individuals, stops in the Central Platte River Valley (CPRV) during spring migration from mid-February through mid-April. Research suggests that the MCP may be shifting its distribution spatially and temporally within the CPRV. From 2002 to 2017, we conducted weekly aerial surveys of Sandhill Cranes staging in the CPRV to examine temporal and spatial trends in their abundance and distribution. Then, we used winter temperature and drought severity measures from key wintering and early migratory stopover locations to assess the impacts of weather patterns on annual migration chronology in the CPRV. We also evaluated channel width and land cover characteristics using aerial imagery from 1938, 1998, and 2016 to assess the relationship between habitat change and the spatial distribution of the MCP in the CPRV. We used generalized linear models, cumulative link models, and Akaike’s information criterion corrected for small sample sizes (AICc) to compare temporal and spatial models. Temperatures and drought conditions at wintering and migration locations that are heavily used by Greater Sandhill Cranes ( A. c. tabida ) best predicted migration chronology of the MCP to the CPRV. The spatial distribution of roosting Sandhill Cranes from 2015 to 2017 was best predicted by the proportion of width reduction in the main channel since 1938 (rather than its width in 2016) and the proportion of land cover as prairie-meadow habitat within 800 m of the Platte River. Our data suggest that Sandhill Cranes advanced their migration by an average of just over 1 day per year from 2002 to 2017, and that they continued to shift eastward, concentrating at eastern reaches of the CPRV. Climate change, land use change, and habitat loss have all likely contributed to Sandhill Cranes coming earlier and staying longer in fewer reaches of the CPRV, increasing their site use intensity. These historically unprecedented densities may present a disease risk to Sandhill Cranes and other waterbirds, including Whooping Cranes ( Grus americana ). Our models suggest that conservation actions may be maintaining Sandhill Crane densities in areas that would otherwise be declining in use. We suggest that management actions intended to mitigate trends in the distribution of Sandhill Cranes, including wet meadow restoration, may similarly benefit prairie- and braided river–endemic species of concern.

Nebraska↗
USGS2018

The relative importance of intrinsic and extrinsic drivers to population growth vary among local populations of Greater Sage-Grouse: An integrated population modeling approach

Consideration of ecological scale is fundamental to understanding and managing avian population growth and decline. Empirically driven models for population dynamics and demographic processes across multiple spatial scales can be powerful tools to help guide conservation actions. Integrated population models (IPMs) provide a framework for better parameter estimation by unifying multiple sources of data (e.g., count and demographic data). Hierarchical structure within such models that include random effects allow for varying degrees of data sharing across different spatiotemporal scales. We developed an IPM to investigate Greater Sage-Grouse ( Centrocercus urophasianus ) on the border of California and Nevada, known as the Bi-State Distinct Population Segment. Our analysis integrated 13 years of lek count data ( n > 2,000) and intensive telemetry (VHF and GPS; n > 350 individuals) data across 6 subpopulations. Specifically, we identified the most parsimonious models among varying random effects and density-dependent terms for each population vital rate (e.g., nest survival). Using a joint likelihood process, we integrated the lek count data with the demographic models to estimate apparent abundance and refine vital rate parameter estimates. To investigate effects of climatic conditions, we extended the model to fit a precipitation covariate for instantaneous rate of change ( r ). At a metapopulation extent (i.e. Bi-State), annual population rate of change λ ( e r ) did not favor an overall increasing or decreasing trend through the time series. However, annual changes in λ were driven by changes in precipitation (one-year lag effect). At subpopulation extents, we identified substantial variation in λ and demographic rates. One subpopulation clearly decoupled from the trend at the metapopulation extent and exhibited relatively high risk of extinction as a result of low egg fertility. These findings can inform localized, targeted management actions for specific areas, and status of the species for the larger Bi-State.

The Auk↗
USGS2025

Quantifying regional ecological dynamics using agency monitoring data, ecological site descriptions, and ecological site groups

Information about what ecological conditions are likely, causes or drivers of degradation, and potential management actions to restore degraded lands may support land conservation and restoration decisions. State-and-transition models (STMs) describe persistent plant and ecological conditions that are possible (the “state”) within a given abiotic setting and drivers or actions that can cause shifts between states (the “transitions”). These primarily conceptual models are widely used to inform resource and conservation decisions. Data-driven STMs have been developed for some lands, but not at regional or national scales. Here, we demonstrate a new repeatable workflow for developing data-driven STMs in the United States (US). The approach leverages predictive maps of Ecological Site Groups (ESGs), extensive field-based Federal monitoring databases, information from Ecological Site Description (ESD) STMs, soil erosion models, remotely sensed productivity, and other available spatial information (fire, land protection, and drought) to provide context and descriptions of the data-driven states, including likely drivers of transitions. Results of this workflow applied to one dryland ESG in the Upper Colorado River Basin in the southwestern US suggest that an Invaded state (16% of 1352 plots) and some occurrences of a Grassland state (30% of plots) are in a degraded or at-risk condition with reduced ecosystem services. The most common drivers of state transitions in the associated ESDs ( n = 26) are related to livestock grazing and fire. The Invaded state in the ESG has evidence of degraded habitat quality and accelerated run-off while the Grassland state occurrences show reduced richness, productivity, and elevated erosion risk by wind. Areas subject to wildfire and with lower protection status had greater probability of Invaded state occurrence, generally supporting drivers in ESDs. The workflow presented here can serve as a template for describing ecological dynamics at regional scales, and support prioritization of land for conservation and climate adaptation activities.

Rangeland Ecology & Management↗
USGS2023

Northwest Forest Plan — The first 25 years (1994–2018): Watershed condition status and trends

This report describes status and trends in watershed condition across the Northwest Forest Plan (NWFP) area over the first 25 years since its inception in 1994. The program charged with this task is the Aquatic and Riparian Effectiveness Monitoring Program (AREMP), which has assembled information from field data collection, spatial datasets, and a host of landscape models to evaluate the status and trends in aquatic resources in streams and watersheds. Field data included hydrologic measurements (stream wetted widths and temperatures), geomorphic responses (instream wood and sediment), and biological responses (macroinvertebrates and aquatic organism passage). Novel statistical models were used to estimate trends in these measured responses. A suite of complementary modeled results was also employed to describe hydrometeorological drivers (e.g., drought indices and stream discharge), forest cover (upslope and riparian vegetation), and geomorphic conditions (e.g., road-related estimates of chronic and shallow landslide sediment delivery risk). Collectively, information on these responses allowed us to rigorously evaluate instream responses and hypothesize watershed drivers of those responses across the NWFP area and over time. The majority of responses we observed indicated widespread and incremental improvements from active management of forests, forest roads, and road-stream crossings as envisioned by the aquatic conservation strategy of the NWFP. Additionally, many of the responses we observed were consistent with those expected under the influences of changing climates in the Pacific Northwest. Ultimately, the long-term, broad-scale information provided by AREMP is a critical foundation for evaluating the effectiveness of federal land management and the effects of changing climates on water resources that sustain the Pacific Northwest’s human and natural landscapes.

California, Oregon, Washington↗
USGS2013

Synthesis and interpretation of surface-water quality and aquatic biota data collected in Shenandoah National Park, Virginia, 1979-2009

Shenandoah National Park in northern and central Virginia protects 777 square kilometers of mountain terrain in the Blue Ridge physiographic province and more than 90 streams containing diverse aquatic biota. Park managers and visitors are interested in the water quality of park streams and its ability to support healthy coldwater communities and species, such as the native brook trout ( Salvelinus fontinalis ), that are at risk in the eastern United States. Despite protection from local stressors, however, the water quality of streams in the park is at risk from many regional stressors, including atmospheric pollution, decline in the health of the surrounding forests because of invasive forest pests, and global climate change. In 2010, the U.S. Geological Survey, in cooperation with the National Park Service, undertook a study to compile, analyze, and synthesize available data on water quality, aquatic macroinvertebrates, and fish within Shenandoah National Park. Specifically, the effort focused on creating a comprehensive water-resources database for the park that can be used to evaluate temporal trends and spatial patterns in the available data, and characterizing those data to better understand interrelations among water quality, aquatic macroinvertebrates, fish, and the landscape.

Virginia↗
USGS2023

Decision science as a framework for combining geomorphological and ecological modeling for the management of coastal systems

The loss of ecosystem services due to climate change and coastal development is projected to have significant impacts on local economies and conservation of natural resources. Consequently, there has been an increase in coastal management activities such as living shorelines, oyster reef restoration, marsh restoration, beach and dune nourishment, and revegetation projects. Coastal management decisions are complex and include challenging trade-offs. Decision science offers a useful framework to address such complex problems. Here, we provide a synthesis about how decision science can help to integrate research from multiple disciplines (physical and life sciences) with management of coastal and marine systems. Specifically, we discuss the importance of considering concepts and techniques from ecology, coastal geology, geomorphology, climate science, oceanography, and decision analysis when developing conservation plans for coastal restoration. We illustrate the process with several coastal restoration studies. Our capstone example is based on a recent barrier island restoration assessment project at Dauphin Island, Alabama, which included the development of geomorphological and ecological models. We show how decision science can be used as a framework to combine geomorphological and ecological modeling to help inform management decisions while considering uncertainty about system changes and risk tolerance. We also build on our examples through a review of recently developed techniques for spatial conservation planning for land acquisition decisions and the application of adaptive management for sequential decisions.

Alabama↗
USGS2003

A strategy for mapping mid-scale existing vegetation in support of national fire fuel assessment

Geospatial distribution of natural vegetation is among the very important environmental parameters required for applications ranging from global climate change to monitoring of natural hazards, monitoring of ecosystem vitality, and fire management practices. Increasingly sophisticated applications require vegetation datasets to cover large areas at a suitable scale and provide sufficiently detailed information. In this paper, we describe a research effort to develop a remote sensing methodology capable of producing 30-meter resolution, wall-to-wall coverage of existing vegetation types and structure variables in support of a multi-agency fire fuels and fire risks assessment project. Success of this remote sensing research effort is dependent on improved sensor and data qualities, a thorough understanding of regional and local vegetation ecology, successful integration of remote sensing with a large amount of field plot data, and flexible mapping algorithms. Preliminary results produced in the Wasatch Range and Uinta Mountains of central Utah include 28 vegetation types with an overall accuracy of 60% (average by life forms), percent canopy density (sub-pixel density) of forest, shrub, and herbaceous cover (correlation coefficient of 89, 60, and 55% respectively), and average top canopy height of forest, shrub, and herbaceous cover (correlation coefficient of 73, 50, 20% respectively). Techniques to improve the first-round results are discussed, including refinements of mapping models and use of relevant environmental gradients and potential vegetation classification associated with actual vegetation types.

Conference Paper↗
USGS2013

U.S. Geological Survey climate and land use change science strategy—A framework for understanding and responding to global change

Executive Summary The U.S. Geological Survey (USGS), a nonregulatory Federal science agency with national scope and responsibilities, is uniquely positioned to serve the Nation’s needs in understanding and responding to global change, including changes in climate, water availability, sea level, land use and land cover, ecosystems, and global biogeochemical cycles. Global change is among the most challenging and formidable issues confronting our Nation and society. Scientists agree that global environmental changes during this century will have far-reaching societal implications (Intergovernmental Panel on Climate Change, 2007; U.S. Global Change Research Program, 2009). In the face of these challenges, the Nation can benefit greatly by using natural science information in decisionmaking. Since the passage of the U.S. Global Change Research Act of 1990, the USGS has made substantial scientific contributions to understanding the interactive living and nonliving components of the Earth system. USGS natural science activities have led to fundamental advances in observing and understanding climate and land-cover change and the effects these changes have on ecosystems, natural-resource availability, and societal sustainability. Most of these major advances were pursued in partnership with other organizations within and outside the Department of the Interior. The inherent value of partnerships with other U.S. Global Change Research Program agencies and natural-resource managers is emphasized in all aspects of the planning and implementation of this Science Strategy for the coming decade. Over the next 10 years, the USGS will make substantial contributions to understanding how Earth systems interact, respond to, and cause global change. The USGS will work with science partners, decisionmakers, and resource managers at local to international levels (including Native American tribes) to improve understanding of past and present change; develop relevant forecasts; and identify those lands, resources, and communities most vulnerable to global change processes. Science will play an essential role in helping communities and land and resource managers understand local to global implications, anticipate effects, prepare for changes, and reduce the risks associated with decisionmaking in a changing environment. USGS partners and stakeholders will benefit from the data, predictive models, and decision-support products and services resulting from the implementation of this strategy. This Science Strategy recognizes core USGS strengths that are applied to key societal problems. It establishes seven goals for USGS global change science and strategic actions that may be implemented in the short term (1–5 years) and the longer term (5–10 years) to improve our understanding of the following areas of inquiry: Rates, causes, and impacts of past global changes; The global carbon cycle; Biogeochemical cycles and their coupled interactions; Land-use and land-cover change rates, causes, and consequences; Droughts, floods, and water availability under changing land-use and climatic conditions; Coastal response to sea-level rise, climatic change, and human development; and Biological responses to global change. In addition to the seven thematic goals, we address the central role of monitoring in accordance with the USGS Science Strategy recommendation that global change research should rely on existing “…decades of observational data and long-term records to interpret consequences of climate variability and change to the Nation’s biological populations, ecosystems, and land and water resources” (U.S. Geological Survey, 2007, p. 19). We also briefly describe specific needs and opportunities for coordinating USGS global change science among USGS Mission Areas and address the need for a comprehensive and sustained communications strategy.

Circular↗
USGS2021

Conservation of northwestern and southwestern pond turtles: Threats, population size estimates, and population viability analysis

Accurate status assessments of long-lived, widely distributed taxa depend on the availability of long-term monitoring data from multiple populations. However, monitoring populations across large temporal and spatial scales is often beyond the scope of any one researcher or research group. Consequently, wildlife managers may be tasked with utilizing limited information from different sources to detect range-wide evidence of population declines and their causes. When assessments need to be made under such constraints, the research and management communities must determine how to extrapolate from variable population data to species-level inferences. Here, using three different approaches, we integrate and analyze data from the peer-reviewed literature and government agency reports to inform conservation for northwestern pond turtles (NPT) Actinemys marmorata and southwestern pond turtles (SPT) Actinemys pallida . Both NPT and SPT are long-lived freshwater turtles distributed along the west coast of the United States and Mexico. Conservation concerns exist for both species; however, SPT may face more severe threats and are thought to exist at lower densities throughout their range than NPT. For each species, we ranked the impacts of 13 potential threats, estimated population sizes, and modeled population viability with and without long-term droughts. Our results suggest that predation of hatchlings by invasive predators, such as American bullfrogs Lithobates catesbeianus and Largemouth Bass Micropterus salmoides, is a high-ranking threat for NPT and SPT. Southwestern pond turtles may also face more severe impacts associated with natural disasters (droughts, wildfires, and floods) than do NPT. Population size estimates from trapping surveys indicate that SPT have smaller population sizes on average than do NPT ( P = 0.0003), suggesting they may be at greater risk of local extirpation. Population viability analysis models revealed that long-term droughts are a key environmental parameter; as the frequency of severe droughts increases with climate change, the likelihood of population recovery decreases, especially when census sizes are low. Given current population trends and vulnerability to natural disasters throughout their range, we suggest that conservation and recovery actions first focus on SPT to prevent further population declines.

Journal of Fish and Wildlife Management↗
USGS2014

A global assessment of the conservation status of the American Oystercatcher Haematopus palliatus

The American Oystercatcher Haematopus palliatus is the most widely distributed of the four oystercatcher species in the Western Hemisphere. Its range covers almost the entire Atlantic Coast from northeastern United States to southern Argentina; on the Pacific Coast it is found from northern Mexico to central Chile. This assessment covers the entire range of the species, and is not intended to serve as a substitute or update for conservation plans that cover the U.S. Atlantic and Gulf Coast populations. Readers are advised to refer to those plans, available at www.whsrn.org, for more detailed information about U.S. populations. The subspecific taxonomy of H. palliatus is far from clear, but five races are recognized in this assessment, primarily to facilitate reference to specific populations (Fig. 1). These are nominate H. p. palliatus (coasts of eastern and southern United States; eastern Mexico; Pacific and Caribbean coasts of Central America; the Caribbean; and northern and eastern South America); H. p. frazari (Gulf of California and western Mexico); H. p. pitanay (coast of western South America); H. p. durnfordi (coast of southeast South America) and H. p. galapagensis (Galapagos Islands). The Galapagos race may deserve species status. Based on a review of existing population estimates and an extrapolation of data from quantitative surveys throughout its range, revised estimates are given for the populations of all five subspecies, and a total population of about 43,000 individuals. The nominate race is the most abundant with an estimated population size of about 20,000 individuals, while the least abundant is H. p. galapagensis , with just 300 individuals estimated. Biogeographic population estimates were used to determine 1% threshold levels and identify sites of regional and global conservation importance. A total of 20 sites have been identified for H. p. palliatus , 5 for H. p. frazari , 10 for H. p. pitanay and 10 for H. p. durnfordi . No key sites were identified for H. p. galapagensis as it is found in low density scattered throughout the islands. Of these 45 sites, 14 have counts that surpass the 1% level of the global population, and are thus of global conservation significance for the species. Because the species is a dispersed breeder, the 1% threshold is of limited value in identifying key breeding sites. For the time being, these have been defined as sites holding 20 or more breeding pairs; 17 such sites have been identified, with all but four in the United States. It is hoped that a more rigorous approach for identifying key breeding sites can be developed in the future. As an obligate coastal species, American Oystercatcher is at risk from widespread habitat loss due to coastal development, and recreational activities that lead to nest disturbance and increased predation. This is exacerbated by the species’ low population size and low reproductive success. Climate change also poses a significant future threat, especially with regard to sea-level rise. To address these threats, conservation actions are proposed that focus on increased legal protection for the species and on the conservation of key sites and important habitats. Conservation could include implementing beneficial management practices, such as restoration of nest and roost sites, controlling predation, and reducing disturbance. Education and outreach programs are needed throughout the species’ range, especially for beach users and urban planners. Training programs will be necessary to ensure successful implementation of many of the priority conservation actions. Finally, a key first step in conserving this species across its range is the creation of a H. palliatus Working Group. Modelled after the U.S. American Oystercatcher Working Group this organization could unite researchers, conservationists, and educators from across the hemisphere to foster coordinated research, conservation action, and monitoring as outlined in this assessment.

International Wader Studies↗
USGS2024

Assessing the sustainability of Pacific walrus harvest in a changing environment

Harvest sustainability is a primary goal of wildlife management and conservation, and in a changing world it is increasingly important to consider environmental drivers of population dynamics alongside harvest in cohesive management plans. This is particularly pertinent for harvested species that are acutely experiencing effects of climate change. The Pacific walrus ( Odobenus rosmarus divergens ), a critical traditional subsistence resource for indigenous communities, is simultaneously subject to rapid habitat loss associated with diminishing sea ice and an increasing anthropogenic footprint in the Arctic. We developed a theta-logistic population modeling-management framework to evaluate various harvest scenarios combined with four potential climate/disturbance scenarios (ranging from optimistic–pessimistic) which simulates Pacific walrus population dynamics to the end of the 21 st century. We considered two types of harvest strategies: (1) adaptive harvest scenarios wherein harvest is calculated as a percentage of the population and annual harvests are updated at set intervals as the population is reassessed, and (2) non-adaptive harvest scenarios wherein annual harvest remains constant. All climate/disturbance scenarios indicated declines of varying severity in Pacific walrus abundance to the end of the 21 st century, even in the absence of harvest. However, we found that an adaptive annual harvest of 1.23% of the independent-aged female subset of the population (e.g., 1,280 independent-aged females harvested in 2020, representing contemporary harvest levels) met our criterion for sustainability (>70% probability of maintaining population abundance above maximum net productivity level) under all climate/disturbance scenarios, accepting a medium risk tolerance level of 25%. This suggests that the present rate of Pacific walrus harvest is sustainable and will continue to be—provided the harvest adapts to match changes in population dynamics. Our simulations suggest that a sustainable non-adaptive harvest is also possible, but only at low levels if the population declines as expected. Applying a constant annual harvest of 1,280 independent-aged females (equivalent to contemporary harvest levels of 1.23) exceeded our criterion for sustainability and resulted in a >5% chance of quasi-extinction by the end of the 21 st century under three of the four climate/disturbance scenarios we evaluated. Our results highlight the importance of adaptive co-management strategies, and we suggest such modeling frameworks are useful for managing for harvest sustainability in a changing climate.

BioRxiv↗