SEARCH · USGS Science

Results for “Global Change Biology”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34Linked to original sources

USGS2013

Population-level thermal performance of a cold-water ectotherm is linked to ontogeny and local environmental heterogeneity

Negative effects of global warming are predicted to be most severe for species that occupy a narrow range of temperatures, have limited dispersal abilities or have long generation times. These are characteristics typical of many species that occupy small, cold streams. Habitat use, vulnerabilities and mechanisms for coping with local conditions can differ among populations and ontogenetically within populations, potentially affecting species‐level responses to climate change. However, we still have little knowledge of mean thermal performance for many vertebrates, let alone variation in performance among populations. Assessment of these sources of variation in thermal performance is critical for projecting the effects of climate change on species and for identifying management strategies to ameliorate its effects. To gauge how populations of the Rocky Mountain tailed frog ( Ascaphus montanus ) might respond to long‐term effects of climate change, we measured the ability of tadpoles from six populations in Glacier National Park (Montana, U.S.A.) to acclimate to a range of temperatures. We compared survival among populations according to tadpole age (1 year or 2 years) and according to the mean and variance of late‐summer temperatures in natal streams. The ability of tadpoles to acclimate to warm temperatures increased with age and with variance in late‐summer temperature of natal streams. Moreover, performance differed among populations from the same catchment. Our experiments with a cold‐water species show that population‐level performance varies across small geographic scales and is linked to local environmental heterogeneity. This variation could influence the rate and mode of species‐level responses to climate change, both by facilitating local persistence in the face of changes in thermal conditions and by providing thermally tolerant colonists to neighbouring populations.

Montana↗

USGS2023

Science to support conservation action in a large river system: The Willamette River, Oregon, USA

Management and conservation efforts that support the recovery and protection of large rivers are daunting, reflecting the complexity of the challenge and extent of effort (in terms of policy, economic investment, and spatial extent) needed to afford measurable change. These large systems have generally experienced intensive development and regulation, compromising their capacity to respond to disturbances such as climate change or wildfire. Functionally, large river and basin management require insights gained from social, ecological, geophysical, and hydrological sciences. This multi-disciplinary perspective can unveil the integrated relationship between a river network's biotic community and seasonally variable environmental conditions that are often influenced by human activities. Large rivers and their basins are constantly changing due to anthropogenic influences and as climate modifies patterns of temperature and precipitation. Because of these factors, the state of knowledge must advance to address changing conditions. The Willamette River, in western Oregon, USA, is a prime example of a basin that has experienced significant degradation and investment in rehabilitation in recent decades. Innovative science has facilitated development of fine-scale, spatially extensive datasets and models that can generate targeted conservation and rehabilitation actions that are prioritized across the entire river network. This prioritization allows investment decisions to be driven by site-specific conditions while simultaneously considering potentials for ecological improvement. Here, we review hydrologic, geomorphic, ecologic, and social conditions in the Willamette River basin through time—including pre-settlement, river development, and contemporary periods—and offer a future vision for consideration. Currently, detailed information about fish populations and habitat, hydrologic conditions, geomorphology, water quality, and land use can be leveraged to make informed decisions about protection, rehabilitation, and development. The time is ripe for strategic management and goal development for the entire Willamette River, and these efforts can be informed by comprehensive science realized through established institutions (e.g., public agencies, non-profit watershed groups, Tribes, and universities) focused on conservation and management. The approaches to science and social-network creation that were pioneered in the Willamette River basin offer insights into the development of comprehensive conservation-based planning that could be implemented in other large river systems globally.

Oregon↗

USGS2018

Plasticity in physiological condition of female brown bears across diverse ecosystems

Variation in life history strategies facilitates the near global distribution of mammals by expanding realized niche width. We investigated physiological plasticity in the spring body composition of adult female brown bears ( Ursus arctos ) across 4 diverse Alaskan ecosystems. Brown bears are a highly intelligent omnivore with a historic range spanning much of North America, Europe, and Asia. We hypothesized that body mass, fat mass, lean mass, and total caloric content would increase across populations with increasing food resource availability. Throughout their range, brown bears enter a period of torpor during winter months, decreasing their metabolic rate as an adaptation to this period of reduced food availability. They also give birth to and nourish offspring during this time. Due to this specific life history strategy, we further hypothesized that proportional body fat and the proportion of total calories derived from fat would be consistent across populations. Our results supported our first hypothesis: body, fat, and lean masses, and caloric content of bears across populations increased with the quality and abundance of available food. However, the proportional body fat content and proportion of calories from fat differed across populations indicating population-specific strategies to meet the demands of reduced seasonal food availability, offspring production and rearing, and climate as well as some plasticity to respond to environmental change or ecosystem perturbations. Investigations of body condition and energetics benefit from combined assessments of absolute, proportional, and caloric metrics to understand the nuances of brown bear physiological dynamics across and within populations.

Alaska↗

USGS2015

Energy development and avian nest survival in Wyoming, USA: A test of a common disturbance index

Global energy demands continue to result in new and emerging sources of anthropogenic disturbance to populations and systems. Here, we assessed the influence of natural gas development on a critical component of fitness (nest survival) for Brewer’s sparrow ( Spizella breweri ), sagebrush sparrow ( Artemisiospiza nevadensis ), and sage thrasher ( Oreoscoptes montanus ), three species of sagebrush-obligate songbirds that are of conservation concern, and assessed the efficacy of a commonly used index of oil and gas development intensity (well density) for estimating habitat transformation and predicting species’ responses. During 2008–2009 and 2011–2012 we monitored 926 nests within two natural gas fields in western Wyoming, USA. We calculated landscape metrics (habitat loss, amount of edge, patch shape complexity, and mean patch size) to identify the aspect of landscape transformation most captured by well density. Well density was most positively associated with the amount of sagebrush habitat loss within 1 square kilometer. Nest survival was relatively invariant with respect to well density for all three species. In contrast, nest survival rates of all three species generally decreased with surrounding habitat loss due to energy development. Thus, although well density and habitat loss were strongly correlated, well density resulted in overly conservative estimates of nest survival probability. Our results emphasize the importance of careful evaluation of the appropriateness of particular indices for quantifying the effects of human-induced habitat change. For managers concerned about the effects of natural gas development or similar forms of human land use to co-occurring breeding birds, we recommend minimizing the amount of associated habitat conversion.

Wyoming↗

USGS2021

A global perspective on the influence of the COVID-19 pandemic on freshwater fish biodiversity

The COVID-19 global pandemic and resulting effects on the economy and society (e.g., sheltering-in-place, alterations in transportation, changes in consumer behaviour, loss of employment) have yielded some benefits and risks to biodiversity. Here, we considered the ways the COVID-19 pandemic has influenced (or may influence) freshwater fish biodiversity (e.g., richness, abundance). In many cases, we could only consider potential impacts using documented examples (often from the media) of likely changes, because anecdotal observations are still emerging and data-driven studies are yet to be completed or even undertaken. We evaluated the potential for the pandemic to either mitigate or amplify widely acknowledged, pre-existing threats to freshwater fish biodiversity (i.e., invasive species, pollution, fragmentation, flow alteration, habitat loss and alteration, climate change, exploitation). Indeed, we identified examples spanning the extremes of positive and negative outcomes for almost all known threats. We also considered the pandemic's impact on freshwater fisheries demand, assessment, research, compliance monitoring, and management interventions (e.g., restoration), with disruptions being experienced in all domains. Importantly, we provide a forward-looking synthesis that considers the potential mechanisms and pathways by which the consequences of the pandemic may positively and negatively impact freshwater fishes over the longer term. We conclude with a candid assessment of the current management and policy responses and the extent to which they ensure freshwater fish populations and biodiversity are conserved for human and aquatic ecosystem benefits in perpetuity.

Biological Conservation↗

USGS2009

Ocean carbon and biogeochemistry scoping workshop on terrestrial and coastal carbon fluxes in the Gulf of Mexico, St. Petersburg, FL, May 6-8, 2008

Despite their relatively small surface area, ocean margins may have a significant impact on global biogeochemical cycles and, potentially, the global air-sea fluxes of carbon dioxide. Margins are characterized by intense geochemical and biological processing of carbon and other elements and exchange large amounts of matter and energy with the open ocean. The area-specific rates of productivity, biogeochemical cycling, and organic/inorganic matter sequestration are high in coastal margins, with as much as half of the global integrated new production occurring over the continental shelves and slopes (Walsh, 1991; Doney and Hood, 2002; Jahnke, in press). However, the current lack of knowledge and understanding of biogeochemical processes occurring at the ocean margins has left them largely ignored in most of the previous global assessments of the oceanic carbon cycle (Doney and Hood, 2002). A major source of North American and global uncertainty is the Gulf of Mexico, a large semi-enclosed subtropical basin bordered by the United States, Mexico, and Cuba. Like many of the marginal oceans worldwide, the Gulf of Mexico remains largely unsampled and poorly characterized in terms of its air-sea exchange of carbon dioxide and other carbon fluxes. In May 2008, the Ocean Carbon and Biogeochemistry Scoping Workshop on Terrestrial and Coastal Carbon Fluxes in the Gulf of Mexico was held in St. Petersburg, FL, to address the information gaps of carbon fluxes associated with the Gulf of Mexico and to offer recommendations to guide future research. The meeting was attended by over 90 participants from over 50 U.S. and Mexican institutions and agencies. The Ocean Carbon and Biogeochemistry program (OCB; http://www.us-ocb.org/) sponsored this workshop with support from the National Science Foundation, the National Oceanic and Atmospheric Administration, the National Aeronautics and Space Administration, the U.S. Geological Survey, and the University of South Florida. The goal of the workshop was to bring together researchers from multiple disciplines studying terrestrial, aquatic, and marine ecosystems to discuss the state of knowledge in carbon fluxes in the Gulf of Mexico, data gaps, and overarching questions in the Gulf of Mexico system. The discussions at the workshop were intended to stimulate integrated studies of marine and terrestrial biogeochemical cycles and associated ecosystems that will help to establish the role of the Gulf of Mexico in the carbon cycle and how it might evolve in the face of environmental change. The information derived from the plenary sessions, questions, and recommendations formulated by the participants will drive future research projects. Further discussion of carbon dynamics is needed to address scales of variability, the infrastructure required for study, and the modeling framework for cross-system integration. During the workshop, participants discussed and provided a number of priorities and recommendations, which are listed on p. 2 of the report. Participants recognized that the key to understanding the Gulf of Mexico system requires international collaboration with scientists from countries adjacent to the Gulf of Mexico. Improved collaboration across existing research community boundaries will be critical and should be encouraged by the funding agencies.

Open-File Report↗

USGS2026

Population trends of dabbling ducks wintering in the alluvial valleys of Arkansas and Mississippi

Population abundances, distributions, and compositions across a diversity of taxa are changing, partly as a consequence of human-induced global modifications. Although linking population fluctuations to anthropogenic-induced alterations can be challenging, it is increasingly clear that long-term monitoring is critical to understanding changing populations. For waterfowl, concerns over recent declines in breeding populations or possible redistribution from using traditional wintering grounds for some species support continued monitoring of regional populations. To further understand population trends on traditional wintering grounds, we examined abundance trends over time within the Mississippi and Arkansas portions of the Mississippi Alluvial Valley, using two sources of data: systematic aerial surveys and citizen science data. We found great annual variability in rates of population change ( r ranging from −1.04 to 0.71) in five species of dabbling ducks. Despite this annual variation, green-winged teal Anas carolinensis , mallards Anas platyrhynchos , northern pintail Anas acuta , and northern shoveler Spatula clypeata showed no significant trends in population size over approximately 15 years in Mississippi and Arkansas, but gadwall Mareca strepera showed a 4% annual increase in the citizen science data for Mississippi. Despite substantial variation in annual abundance, the timing of peak abundance was remarkably consistent from year to year, with peaks typically occurring in January. Our results demonstrate that autumn–winter population numbers of dabbling ducks can be quite variable interannually, but they lack a consistent trend in the Mississippi Alluvial Valley during the past two decades. Going forward, investigation into how citizen science data could be leveraged to increase the precision of trends within this landscape might be of benefit, and sampling efforts could perhaps be added towards the latter portion of the wintering period. As populations continue to adjust in a changing world, maintaining monitoring surveys in regions important to waterfowl is an effective and important means of evaluating trends.

Arkansas, Illinois, Kentucky, Louisiana, Mississip↗

USGS2020

Walleye growth declines following zebra mussel and Bythotrephes invasion

Invasive species represent a threat to aquatic ecosystems globally; however, impacts can be heterogenous across systems. Documented impacts of invasive zebra mussels ( Dreissena polymorpha ) and spiny water fleas ( Bythotrephes cederströmii ; hereafter Bythotrephes ) on native fishes are variable and context dependent across locations and time periods. Here, we use a hierarchical Bayesian analysis of a 35-year dataset on two fish species from 9 lakes to demonstrate that early life growth of ecologically important fishes are influenced by these aquatic invasive species. Walleye ( Sander vitreus ) in their first year of life grew more slowly in the presence of either invader after correcting for temperature (measured by degree days), and were on average 12 or 14% smaller at the end of their first summer following invasion by Bythotrephes or zebra mussels, respectively. Yellow perch ( Perca flavescens ) growth was less affected by invasion. Yellow perch on average grew more slowly in their first year of life following invasion by zebra mussels, although this effect was not statistically distinguishable from zero. Early life growth of both walleye and yellow perch was less tightly coupled to degree days in invaded systems, as demonstrated by increased variance surrounding the degree day-length relationship. Smaller first-year size is related to walleye survival and recruitment to later life stages and has important implications for lake food webs and fisheries management. Future research quantifying effects of zebra mussels and Bythotrephes on other population-level processes and across a wider gradient of lake types is needed to understand the mechanisms driving observed changes in walleye growth.

Minnesota↗

USGS1999

Le Conte's sparrows breeding in Conservation Reserve Program fields: precipitation and patterns of population change

The climate of the North American Great Plains is highly dynamic, with great year-to-year variability in precipitation and periodic, often extreme, wet and dry cycles (Bragg 1995). Drought is a major force of ecological disturbance on the Great Plains and has played a key role in directing the evolution of the grassland biota of this region (Knopf and Samson 1997). Although grassland birds may differ in their responses to enviromenental variations (Rotenberry and Wiens 1991), climatic variability and concomitant unpredictability of resources strongly influence populations of grassland birds across space and time (Wiens 1974, 1986; Cody 1985). Not surprisingly, breeding bird populations on the Great Plains are highly dynamic, exhibiting considerable annual variation in composition, abundance, and distribution (Johnson and Grier 1988, George et al. 1992, Zimmerman 1992, Igl and Johnson 1997). Recently, interest in grassland birds has increased with the recognition that many species are declining both continentally (Droege and Sauer 1994) and globally (Goriup 1988). Identification of the specific factors associated with grassland bird declines in North America, however, remains largely enigmatic (Herkert 1997), and it is complicated by the considerable annual fluctuations in grassland bird distribution and abundance (Igl and Johnson 1997). Although there is evidence that land-use changes on the breeding grounds may have contributed to grassland bird declines (e.g., Igl and Johnson 1997), there also is an indication that long-term drought conditions may have influenced recent population changes of some breeding birds on the Great Plains (Droege and Sauer 1989, Peterjohn and Sauer 1993, Bethke and Nudds 1995, Igl and Johnson 1997). Le Conte's Sparrow (Ammodramus leconteii) is a secretive grassland bird that breeds in central and southern Canada and the northcentral United States (Murray 1969). It winters primarily in the southern United States (Peterson 1980, 1990). Like populations of many grassland breeding birds in North America (Fretwell 1986, Igl and Johnson 1997), Le Conte's Sparrow populations exhibit numerical highs and lows depending on local moisture conditions (Peabody 1901, Stewart 1975, Knapton 1979, Zimmer 1979, Madden 1996). This observation, however, is based largely on anecdotal evidence or short-term observations. Long-term studies of Le Conte's Sparrow populations are limited. Le Conte's Sparrow is poorly represented on the North American Breeding Bird Survey (BBS) because of small sample sizes, poor coverage in the northern portion of its breeding range, and the species' furtive behavior (Sauer et al. 1995). Moreover, dramatic fluctuations in Le Conte's Sparrow abundance tend to obscure the species' long-term population trends on the BBS (Sauer et al. 1995). In this paper we examine long-term population changes of Le Conte's Sparrows breeding in perennial grassland fields enrolled in the Conservation Reserve Program (CRP) on the northern Great Plains. We discuss patterns of population change of Le Conte's Sparrows associated with changes in precipitation and moisture conditions.

Studies in Avian Biology↗

USGS2017

Comparing stream-specific to generalized temperature models to guide salmonid management in a changing climate

Global climate change is predicted to increase air and stream temperatures and alter thermal habitat suitability for growth and survival of coldwater fishes, including brook charr (Salvelinus fontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). In a changing climate, accurate stream temperature modeling is increasingly important for sustainable salmonid management throughout the world. However, finite resource availability (e.g. funding, personnel) drives a tradeoff between thermal model accuracy and efficiency (i.e. cost-effective applicability at management-relevant spatial extents). Using different projected climate change scenarios, we compared the accuracy and efficiency of stream-specific and generalized (i.e. region-specific) temperature models for coldwater salmonids within and outside the State of Michigan, USA, a region with long-term stream temperature data and productive coldwater fisheries. Projected stream temperature warming between 2016 and 2056 ranged from 0.1 to 3.8 °C in groundwater-dominated streams and 0.2–6.8 °C in surface-runoff dominated systems in the State of Michigan. Despite their generally lower accuracy in predicting exact stream temperatures, generalized models accurately projected salmonid thermal habitat suitability in 82% of groundwater-dominated streams, including those with brook charr (80% accuracy), brown trout (89% accuracy), and rainbow trout (75% accuracy). In contrast, generalized models predicted thermal habitat suitability in runoff-dominated streams with much lower accuracy (54%). These results suggest that, amidst climate change and constraints in resource availability, generalized models are appropriate to forecast thermal conditions in groundwater-dominated streams within and outside Michigan and inform regional-level salmonid management strategies that are practical for coldwater fisheries managers, policy makers, and the public. We recommend fisheries professionals reserve resource-intensive stream-specific models for runoff-dominated systems containing high-priority fisheries resources (e.g. trophy individuals, endangered species) that will be directly impacted by projected stream warming.

Michigan↗

USGS2015

Hydrographic surveys at seven chutes and three backwaters on the Missouri River in Nebraska, Iowa, and Missouri, 2011-13

The U.S. Geological Survey cooperated with the U.S. Army Corps of Engineers (USACE), Omaha District, to complete hydrographic surveys of seven chutes and three backwaters on the Missouri River yearly during 2011–13. These chutes and backwaters were constructed by the USACE to increase the amount of available shallow water habitat (SWH) to support threatened and endangered species, as required by the amended “2000 Biological Opinion” on the operation of the Missouri River main-stem reservoir system. Chutes surveyed included Council chute, Plattsmouth chute, Tobacco chute, Upper Hamburg chute, Lower Hamburg chute, Kansas chute, and Deroin chute. Backwaters surveyed included Ponca backwater, Plattsmouth backwater, and Langdon backwater. Hydrographic data from these chute and backwater surveys will aid the USACE to assess the current (2011–13) amount of available SWH, the effects river flow have had on evolving morphology of the chutes and backwaters, and the functionality of the chute and backwater designs. Chutes and backwaters were surveyed from August through November 2011, June through November 2012, and May through October 2013. During the 2011 surveys, high water was present at all sites because of the major flooding on the Missouri River. The hydrographic survey data are published along with this report in comma-separated-values (csv) format with associated metadata. Hydrographic surveys included bathymetric and Real-Time Kinematic Global Navigation Satellite System surveys. Hydrographic data were collected along transects extending across the channel from top of bank to top of bank. Transect segments with water depths greater than 1 meter were surveyed using a single-beam echosounder to measure depth and a differentially corrected global positioning system to measure location. These depth soundings were converted to elevation using water-surface-elevation information collected with a Real-Time Kinematic Global Navigation Satellite System. Transect segments with water depths less than 1 meter were surveyed using Real-Time Kinematic Global Navigation Satellite Systems. Surveyed features included top of bank, toe of bank, edge of water, sand bars, and near-shore areas. Discharge was measured at chute survey sites, in both the main channel of the Missouri River upstream from the chute and the chute. Many chute entrances and control structures were damaged by floodwater during the 2011 Missouri River flood, allowing a larger percentage of the total Missouri River discharge to flow through the chute than originally intended in the chute design. Measured discharge split between the main channel and the chute at most chutes was consistent with effects of the 2011 Missouri River flood damages and a larger percent of the total Missouri River discharge was flowing through the chute than originally intended. The U.S. Army Corps of Engineers repaired many of these chutes in 2012 and 2013, and the resulting hydraulic changes are reflected in the discharge splits.

Iowa, Missouri, Nebraska↗

USGS2003

Response of desert biological soil crusts to alterations in precipitation frequency

Biological soil crusts, a community of cyanobacteria, lichens, and mosses that live on the soil surface, occur in deserts throughout the world. They are a critical component of desert ecosystems, as they are important contributors to soil fertility and stability. Future climate scenarios predict alteration of the timing and amount of precipitation in desert environments. Because biological soil crust organisms are only metabolically active when wet, and as soil surfaces dry quickly in deserts during late spring, summer, and early fall, the amount and timing of precipitation is likely to have significant impacts on the physiological functioning of these communities. Using the three dominant soil crust types found in the western United States, we applied three levels of precipitation frequency (50% below-average, average, and 50% above-average) while maintaining average precipitation amount (therefore changing both timing and size of applied events). We measured the impact of these treatments on photosynthetic performance (as indicated by dark-adapted quantum yield and chlorophyll a concentrations), nitrogenase activity, and the ability of these organisms to maintain concentrations of radiation-protective pigments (scytonemin, beta-carotene, echinenone, xanthophylls, and canthaxanthin). Increased precipitation frequency produced little response after 2.5 months exposure during spring (1 April-15 June) or summer (15 June-31 August). In contrast, most of the above variables had a large, negative response after exposure to increased precipitation frequency for 6 months spring-fall (1 April-31 October) treatment. The crusts dominated by the soil lichen Collema, being dark and protruding above the surface, dried the most rapidly, followed by the dark surface cyanobacterial crusts (Nostoc-Scytonema-Microcoleus), and then by the light cyanobacterial crusts (Microcoleus). This order reflected the magnitude of the observed response: crusts dominated by the lichen Collema showed the largest decline in quantum yield, chlorophyll a, and protective pigments; crusts dominated by Nostoc-Scytonema-Microcoleus showed an intermediate decline in these variables; and the crusts dominated by Microcoleus showed the least negative response. Most previous studies of crust response to radiation stress have been short-term laboratory studies, where organisms were watered and kept under moderate temperatures. Such conditions would give crust organisms access to ample carbon to respond to imposed stresses (e.g., production of UV-protective pigments, replacement of degraded chlorophyll). In contrast, our longer-term study showed that under field conditions of high air temperatures and frequent, small precipitation events, crust organisms appear unable to produce protective pigments in response to radiation stress, as they likely dried more quickly than when they received larger, less frequent events. Reduced activity time likely resulted in less carbon available to produce or repair chlorophyll a and/or protective pigments. Our findings may partially explain the global observation that soil lichen cover and richness declines as the frequency of summer rainfall increases. ?? Springer-Verlag 2003.

Oecologia↗

USGS2014

Normative standards for land use in Vermont: Implications for biodiversity

The conversion of natural lands to developed uses poses a great threat to global terrestrial biodiversity. Natural resource managers, tasked with managing wildlife as a public trust, require techniques for predicting how much and where wildlife habitat is likely to be converted in the future. Here, we develop a methodology to estimate the “social carrying capacity for development” – SK d – for 251 towns across the state of Vermont, USA. SK d represents town residents’ minimum acceptable human population size and level of development within town boundaries. To estimate SK d across towns within the state of Vermont (USA), as well as the average state-wide SK d , we administered a visual preference survey ( n = 1505 responses) to Vermont residents, and asked respondents to rate alternative landuse scenarios in a fictional Vermont town on a scale of +4 (highly acceptable) to −4 (highly unacceptable). We additionally collected demographic data such as age and income, as well as ancillary information such as participation in town-planning meetings and location of residence. We used model selection and AIC to fit a cubic function to the response data, allowing us to estimate SK d at a town scale based on town demographic characteristics. On average, Vermonters had a SK d of 9.1% development on the landscape; this estimate is 68% higher than year 2000 levels for development (5.4%). Respondents indicated that management action to curb development was appropriate at 9.4% development (roughly the statewide SK d average). Management by local, regional, and state levels were considered acceptable for curbing development while federal level management of development was considered unacceptable. Given a scenario where development levels were at SK d , we predicted a 16,753 km 2 reduction in forested land (−11.16%) and a 1038 km 2 reduction in farmland (−60.45%). Such changes would dramatically alter biodiversity patterns state-wide. In a companion paper, we estimate how these changes would affect the distribution of wildlife species.

Vermont↗

USGS2020

Holocene paleoclimate change in the western US: The importance of chronology in discerning patterns and drivers

Sediment in lakes and meadows forms a powerful archive that can be used to reconstruct environmental change through time. Reconstructions of lake level, of chemical, biological, and hydrological conditions, and of surrounding vegetation provide detailed information about past climate conditions, both locally and regionally. Indeed, most of our current knowledge of centennial- to millennial-scale climate variability in the arid western United States, where information about past hydroclimate is particularly important, comes from such sediment-based reconstructions. The pressing need for robust, precise predictions of future conditions is a significant motivation for paleoclimate science, and current research questions frequently require Holocene reconstructions to be resolved at sub-centennial timescales. Increasingly, regional syntheses seek to identify synoptic-scale patterns similar to those defined from modern observations (seasonal, interannual, multi-decadal, etc.) or to compare with the output of climate model simulations. However, the age control on existing records, especially those more than about 20 years old, is often sufficient only for millennial-scale interpretation. Here we assess the age control for 84 published and unpublished records from lakes and meadows in the Great Basin, California, and desert southwest, and use Bayesian modeling to evaluate the 95% uncertainty ranges for the 42 best-dated records. In the Late Holocene, about half of the 42 records have <400-year mean uncertainty ranges; however, high-precision age control is especially critical for young records, used to develop an accurate understanding of a proxy’s response to known climate variations. In the Middle Holocene, records vary from 400 to >800-year mean uncertainty and records of the Early Holocene have 600- to >1400-year mean uncertainty ranges. We find that the largest control on modeled uncertainties is dating density, with at least 2 dates/kyr being optimal and suggest obtaining “range-finder” dates at the onset of a study to better predict the total number of dates needed for an adequate age model. Such a density avoids a commonly observed phenomenon of significant peaks in uncertainty arising in gaps between age control points. Analysis of the uncertainties associated with proxy shifts reveal that more than half are >400 years. Although such large uncertainties currently prevent sub-centennial interpretations in most cases, increased dating density, strategic use of limited funds (including budgeting for a 2 date/kyr minimum at the proposal stage), construction of age-depth models with Bayesian methods, and critical evaluation of chronological uncertainty will shed light on past climate variability at finer timescales, enhancing our understanding of global and regional drivers of western U.S. climate.

California, Idaho, Nevada, Oregon, Utah↗

USGS2022

Complex demographic responses to contrasting climate drivers lead to divergent population trends across the range of a threatened alpine plant

Alpine plants are likely to be particularly vulnerable to climate change because of their restricted distributions and sensitivity to rapid environmental shifts occurring in high-elevation ecosystems. The well-studied Haleakalā silversword (‘āhinahina, Argyroxiphium sandwicense subsp. macrocephalum ) already exhibits substantial climate-associated population decline, and offers the opportunity to understand the ecological and demographic mechanisms that underlie ongoing and predicted range shifts. We use nearly four decades of demographic monitoring for this threatened Hawaiian species, in combination with other biological, ecological and climate data to explore demographic responses across its entire range. We construct and independently validate population models for two elevation zones representing the species’ lower trailing and higher stable regions. Differences in population growth rate (lambda) between trailing and stable regions were influenced most strongly by lower survival of juvenile and small adult size classes, as well as by lower recruitment and lower survival of seedlings and large adults in the trailing region. Furthermore, seed production appears to have decreased from the 1980’s to present in the trailing region, and is now significantly less than in the stable region. Lambda and several underlying vital rates were significantly associated with wetter dry season conditions in the lower trailing region, indicating water limitation. In the higher elevation stable region, in contrast, lambda and vital rates were associated with warmer air temperatures, indicating cold limitation. These contrasting demographic patterns and climate dependencies lead to a high probability of extinction over the next century in the lower region, where most plants occur, but zero probability of the same in the higher region, according to stochastic population projections. Drier future scenarios further increase the probability of extinction at low elevations. The combined results illustrate the complexity in the demographic response and future viability that can occur across the range of a single species.

Global Ecology and Conservation↗

USGS2014

Acceptability of residential development in a regional landscape: Potential effects on wildlife occupancy patterns

The conversion of natural lands to developed uses may pose the single greatest human threat to global terrestrial biodiversity. Continued human growth and development over the next century will further exacerbate these effects of habitat loss and fragmentation. Natural resource managers are tasked with managing wildlife as a public trust, yet often have little say in land use decisions. Generally speaking, decision makers could benefit from an understanding of what different regulations mean in terms of wildlife distribution. In a previous paper ( Bettigole et al., 2013 ), we surveyed town residents throughout Vermont to measure how respondents feel about a range of development levels within their town boundaries. We estimated the “social carrying capacity for development” – or SK d – for 251 towns in Vermont. SK d provides an estimate of the level of developed land cover classes that town residents deem “acceptable” within their town boundaries. In this paper, we design a framework for linking the town-specific SK d estimates with the wildlife distribution patterns for three wide-ranging mammalian species: American black bear ( Ursus americanus ), fisher ( Martes pennanti ), and bobcat ( Lynx rufus ). We simulated landscape conditions at SK d for each town in Vermont, and then used existing occupancy models for the three target species to spatially map and compare occupancy rates in the baseline year 2000 with occupancy rates at SK d . With nearly 90% of Vermont towns willing to increase developed landcover classes within town boundaries compared to baseline levels, significant state-wide changes in occupancy rates were predicted for all three focal species. Average occupancy rates declined by −15.9% and −3.1% for black bear and bobcats, respectively. Average occupancy rates for fisher increased by 9.0%. This study provides a method for linking development standards within a town with wildlife occurrence. Across towns, the methodology spatially identifies areas that may be at risk of future development, as well as identifying areas where wildlife distribution patterns may face future change as a result of increased human population growth and development.

Biological Conservation↗

USGS2018

A North American Hydroclimate Synthesis (NAHS) of the Common Era

This study presents a synthesis of century-scale hydroclimate variations in North America for the Common Era (last 2000 years) using new age models of previously published multiple proxy-based paleoclimate data. This North American Hydroclimate Synthesis (NAHS) examines regional hydroclimate patterns and related environmental indicators, including vegetation, lake water elevation, stream flow and runoff, cave drip rates, biological productivity, assemblages of living organisms, and salinity. Centennial-scale hydroclimate anomalies are obtained by iteratively sampling the proxy data on each of thousands of age model realizations and determining the fractions of possible time series indicating that the century-smoothed data was anomalously wet or dry relative to the 100 BCE to 1900 CE mean. Results suggest regionally asynchronous wet and dry periods over multidecadal to centennial timescales and frequent periods of extended regional drought. Most sites indicate drying during previously documented multicentennial periods of warmer Northern Hemisphere temperatures, particularly in the western U.S., central U.S., and Canada. Two widespread droughts were documented by the NAHS: from 50 BCE to 450 CE and from 800 to 1100 CE. Major hydroclimate reorganizations occurred out of sync with Northern Hemisphere temperature variations and widespread wet and dry anomalies occurred during both warm and cool periods. We present a broad assessment of paleoclimate relationships that highlights the potential influences of internal variability and external forcing and supports a prominent role for Pacific and Atlantic Ocean dynamics on century-scale continental hydroclimate.

Global and Planetary Change↗

USGS2019

Long-term nitrogen addition shifts the soil nematode community to bacterivore-dominated and reduces its ecological maturity in a subalpine forest

Nitrogen deposition from anthropogenic sources is a global problem that reaches even the most remote ecosystems. Responses belowground vary by ecosystem, and have feedbacks to geochemical processes, including carbon storage. A long-term nitrogen addition study in a subalpine forest has shown carbon loss over time, atypical for a forest ecosystem. Loss of microbial biomass is likely linked to lower soil carbon, but the mechanism behind this is still unknown. One possible explanation is through increased turnover due to grazing by soil fauna. Because nematodes occupy many trophic levels and are sensitive to trophic and environmental changes, assessing their communities helps reveal belowground responses. In this study, we tested the hypothesis that long-term nitrogen fertilization affects nematode community structure and maturity beneath coniferous forests in the Rocky Mountains, indicating a faster cycling, bacterial-driven system. We identified and enumerated nematodes by trophic group and family from experimental plots. Total nematode abundance was 40–96% greater in fertilized plots compared to the control, but richness, diversity, and ecological maturity were lower. The differences in abundance were driven by opportunistic bacterivores (e.g., Rhabditidae) and plant parasites (e.g., Tylenchidae), which made up 23 and 13% of the community in fertilized compared to 7 and 5% in control plots, respectively. Nematode maturity indices showed that the nematode food webwas enriched (indicating high nutrient/resource status) and structured (all trophic levels present, including long-lived predators) in both treatments, but significantly more enriched in the fertilized treatment. Nonmetric multidimensional scaling of the relative abundance of nematode families demonstrated that nematode community composition differed between treatments, driven largely by opportunistic bacterivores (e.g., Rhabditidae) in the fertilized plots. The mechanism of the aboveground–belowground link between nitrogen deposition and nematode community composition is likely through increased microbial turnover, and sustained high-quality food for microbial grazing nematodes.

Soil Biology and Biochemistry↗