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At least 217 records · Page 12Linked to original sources
USGS2016

Developing integrated methods to address complex resource and environmental issues

Introduction This circular provides an overview of selected activities that were conducted within the U.S. Geological Survey (USGS) Integrated Methods Development Project, an interdisciplinary project designed to develop new tools and conduct innovative research requiring integration of geologic, geophysical, geochemical, and remote-sensing expertise. The project was supported by the USGS Mineral Resources Program, and its products and acquired capabilities have broad applications to missions throughout the USGS and beyond. In addressing challenges associated with understanding the location, quantity, and quality of mineral resources, and in investigating the potential environmental consequences of resource development, a number of field and laboratory capabilities and interpretative methodologies evolved from the project that have applications to traditional resource studies as well as to studies related to ecosystem health, human health, disaster and hazard assessment, and planetary science. New or improved tools and research findings developed within the project have been applied to other projects and activities. Specifically, geophysical equipment and techniques have been applied to a variety of traditional and nontraditional mineral- and energy-resource studies, military applications, environmental investigations, and applied research activities that involve climate change, mapping techniques, and monitoring capabilities. Diverse applied geochemistry activities provide a process-level understanding of the mobility, chemical speciation, and bioavailability of elements, particularly metals and metalloids, in a variety of environmental settings. Imaging spectroscopy capabilities maintained and developed within the project have been applied to traditional resource studies as well as to studies related to ecosystem health, human health, disaster assessment, and planetary science. Brief descriptions of capabilities and laboratory facilities and summaries of some applications of project products and research findings are included in this circular. The work helped support the USGS mission to “provide reliable scientific information to describe and understand the Earth; minimize loss of life and property from natural disasters; manage water, biological, energy, and mineral resources; and enhance and protect our quality of life.” Activities within the project include the following: Spanned scales from microscopic to planetary; Demonstrated broad applications across disciplines; Included life-cycle studies of mineral resources; Incorporated specialized areas of expertise in applied geochemistry including mineralogy, hydrogeology, analytical chemistry, aqueous geochemistry, biogeochemistry, microbiology, aquatic toxicology, and public health; and Incorporated specialized areas of expertise in geophysics including magnetics, gravity, radiometrics, electromagnetics, seismic, ground-penetrating radar, borehole radar, and imaging spectroscopy. This circular consists of eight sections that contain summaries of various activities under the project. The eight sections are listed below: Laboratory Facilities and Capabilities, which includes brief descriptions of the various types of laboratories and capabilities used for the project; Method and Software Development, which includes summaries of remote-sensing, geophysical, and mineralogical methods developed or enhanced by the project; Instrument Development, which includes descriptions of geophysical instruments developed under the project; Minerals, Energy, and Climate, which includes summaries of research that applies to mineral or energy resources, environmental processes and monitoring, and carbon sequestration by earth materials; Element Cycling, Toxicity, and Health, which includes summaries of several process-oriented geochemical and biogeochemical studies and health-related research activities; Hydrogeology and Water Quality, which includes descriptions of innovative geophysical, remote-sensing, and geochemical research pertaining to hydrogeology and water-quality applications; Hazards and Disaster Assessment, which includes summaries of research and method development that were applied to natural hazards, human-caused hazards, and disaster assessments; and Databases and Framework Studies, which includes descriptions of fundamental applications of geophysical studies and of the importance of archived data.

Circular↗
USGS2019

Chesapeake Bay impact structure—Development of "brim" sedimentation in a multilayered marine target

The late Eocene Chesapeake Bay impact structure was formed in a multilayered target of seawater underlain sequentially by a sediment layer and a rock layer in a continental-shelf environment. Impact effects in the “brim” (annular trough) surrounding and adjacent to the transient crater, between the transient crater rim and the outer margin, primarily were limited to the target-sediment layer. Analysis of published and new lithostratigraphic, biostratigraphic, sedimentologic, petrologic, and mineralogic studies of three core holes, and published studies of a fourth core hole, provided information for the interpretation of the impact processes, their interactions and relative timing, their resulting products, and sedimentation in the brim. Most studies of marine impact-crater materials have focused on those found in the central crater. There are relatively few large, complex marine craters, of which most display a wide brim around the central crater. However, most have been studied using minimal data sets. The large number of core holes and seismic profiles available for study of the Chesapeake Bay impact structure presents a special opportunity for research. The physical and chronologic records supplied by study of the sediment and rock cores of the Chesapeake Bay impact indicate that the effects of the initial, short-lived contact and compression and excavation stages of the impact event primarily were limited to the transient crater. Only secondary effects of these processes are evident in the brim. The preserved record of the brim was created primarily in the subsequent modification stage. In the brim, the records of early impact processes (e.g., outgoing tsunamis, overturned flap collapse) were modified or removed by later processes. Transported and rotated, large and small clasts of target sediments, and intervals of fluidized sands indicate that seismic shaking fractured and partially fluidized the Cretaceous and Paleogene target sediments, which led to their inward transport by collapse and lateral spreading toward the transient crater. The succeeding inward seawater-resurge flow quickly overtook and interacted with the lateral spreading, further facilitating sediment transport across the brim and into the transient crater. Variations in the cohesion and relative depth of the target sediments controlled their degree of disaggregation and redistribution during these events. Melt clasts and shocked and unshocked rock clasts in the resurge sediments indicate fallout from the ejecta curtain and plume. Basal parautochthonous remnant sections of target Cretaceous sediments in the brim thin toward the collapsed transient crater. Overlying seawater-resurge deposits consist primarily of diamictons that vary laterally in thickness, and vertically and laterally in maximum grain size. After cessation of resurge flow and re-establishment of pre-impact sea level, sandy sediment gravity flows moved from the margin to the center of the partially filled impact structure (shelf basin). The uppermost unit consists of stratified sediments deposited from suspension. Postimpact clayey silts cap the crater fill and record the return to shelf sedimentation at atypically large paleodepths within the shelf basin. An unresolved question involves a section of gravel and sand that overlies Neoproterozoic granite in the inner part of the brim in one core hole. This section may represent previously unrecognized, now parautochthonous Cretaceous sediments lying nonconformably above basement granite, or it may represent target sediments that were moved significant distances by lateral spreading above basement rocks or above a granite megaclast from the overturned flap. The Chesapeake Bay impact structure is perhaps the best documented example of the small group of multilayer, marine-target impacts formed in continental shelves or beneath epeiric seas.

Chesapeake Bay↗
USGS2026

Potential for bird-based biotic indices in watershed assessments: A review of methods, applications, and suggestions for improvement

Birds are sensitive to changes in environmental conditions, and metrics such as species diversity, abundance, and guild composition that describe community-level responses to anthropogenic disturbance can be useful indicators of ecosystem condition. We reviewed published studies (56) of bird-based biotic indices developed for diverse ecosystems in 14 countries to evaluate their efficacy for bioassessments. The major categories of indices used included the index of biotic integrity (IBI; 18% of studies), the bird community index (BCI; 13%), and the index of ecological condition (IEC; 7%), with numerous specialized variants comprising the remaining 62% of studies, including indices adapted for specific ecosystems such as grasslands, wetlands, and urban areas. Index performance varied geographically, highlighting the importance of localized calibration. While few studies applied bird indices at landscape and regional scales, applications that included guild-based classification and habitat-specific metrics demonstrated potential for bird-based ecosystem monitoring and assessment. Bird communities were reliable ecological indicators at regional scales when indices incorporated locally derived disturbance and habitat gradients. This regional reliability indicates that expanding bird-based indices to watershed extents is feasible, especially given the availability of extensive resources such as citizen science bird data. There is an abundance of citizen science bird monitoring programs that potentially provide data for use in watershed-scale avian IBIs. Avian indices that combine data from multiple taxa, community-based metrics, and variables describing habitat quality can provide rigorous tools for watershed bioassessment and evidence-based conservation policy implementation.

Environmental Reviews↗
USGS1960

Wetland and water supply

The Geological Survey has received numerous inquiries about the effects of proposed changes in the wetland environment. The nature of the inquiries suggests a general confusion in the public mind as to wetland values and an increasing concern by the public with the need for facts as a basis for sound decisions when public action is required. Perhaps the largest gap in our knowledge is in regard to the role played by the wetland in the natural water scheme. Specialists in such fields as agriculture and conservation have studied the wetland in relation to its special uses and values for farming and as a habitat for fish and wildlife. However, except as studied incidentally by these specialists, the role of the wetland with respect to water has been largely neglected. This facet of the wetland problem is of direct concern to the Geological Survey. We commonly speak of water in terms of its place in the hydrologic environment---as, for example, surface water or ground water. These terms imply that water can be neatly pigeonholed. With respect to the wetland environment nothing can be further from the truth. In fact, one objective of this discussion is to demonstrate that for the wetland environment surface water, ground water, and soil water cannot be separated realistically, but are closely interrelated and must be studied together. It should be noted that this statement holds true for the hydrologic environment in general, and that the wetland environment is by no means unique in this respect. Our second and principal objective is to identify some of the problems that must be studied in order to clarify the role of the wetland in relation to water supply. We have chosen to approach these objectives by briefly describing one area for which we have some information, and by using this example to point out some of the problems that need study. First, however, let us define what we, as geohydrologists, mean by wetland and briefly consider wetland classifications. For our purpose wetlands are land areas that are covered with shallow water or subjected to intermittent flooding and subsequent slow drainage, and which generally are characterized by an accumulation of organic matter hereafter termed swamp deposits.' These wetlands may be classified in a number of different ways depending on the purpose of the classifier. For example, the Fish and Wildlife Service classifies wetlands into 20 different types based on water quality (fresh or salty), drainage, and vegetation. At the risk of some oversimplification we might consider 4 types of wetland from the standpoint of hydrology: (1) fresh-water swamps in which the swamp deposits are underlain by glacial till or bedrock; (2)fresh-water swamps in which the swamp deposits are underlain by marine or lacustrine clay and silt; (3) fresh-water swamps in which the swamp deposits are underlain by glacial outwash or alluvium consisting mostly of sand or sand and gravel; and (4) salt .marshes and salt meadows. The three fresh-water types of wetland are of interest with respect to water supply, and of these, the type in which swamp deposits are underlain by glacial outwash is of particular interest in New England. In the Ipswich River basin above the Geological Survey gaging station at South Middleton, Mass., is an area of 44 square miles which forms the headwaters section of the basin. The relief of the area is low. About half the area consists of hills mostly underlain by bedrock but mantled by a thin layer of glacial till. The other half consists Of lowlands---including swamps, low terraces and plains---underlain by glacial outwash, Swampland, used hereafter as a synonym for wetland, forms about a fourth of the area. Some of the swamps occupy depressions in the till blanket and are situated at somewhat higher levels than the lowlands. The largest swamps, however, border the Ipswich River and its tributaries. Here the swamp deposits, which consist of muck and peat mixed with s

Circular↗
USGS2016

Quantifying the effects of research band resighting activities on staging terns in comparison to other disturbances

Avian research that involves potential disturbance to the study species may have unintended fitness consequences and could lead to biases in measurements of interest. The effects of band resighting on the behavior of mixed-species flocks of staging waterbirds were evaluated against recreational pedestrian activity that was expected to cause flushing. We found a model with additive effects of distance (near, 0-50 m, or far, 50-200 m) and disturbance type (researcher or pedestrian) best explained flock behaviors. The proportion of staging flocks that flushed in response to pedestrians was greatest when pedestrians were within 50 m of the flock. Virtually no flushes were observed in response to researchers, regardless of distance. These results could assist in alleviating concerns that accepted protocols used for intensive band resighting studies on staging seabirds of special conservation status, such as Roseate ( Sterna dougallii ) and Common ( S. hirundo ) terns, may have adverse effects. Our framework could be used by others to test the effects of similar research on sensitive species.

Waterbirds↗
USGS1992

U.S. Geological Survey Library classification system

The U.S. Geological Survey library classification system has been designed for an earth science library. It is a tool for assigning classification numbers to earth science and allied pure science library materials in order to collect these materials into related subject groups on the library shelves and arrange them alphabetically by author and title. It can also be used as a retrieval system to access these materials through the subject and visible geographic classification numbers. The classification scheme has been developed over the years since 1904 to meet the ever-changing needs of increased specialization and new areas of study in the earth sciences. This system contains seven schedules: Subject schedule Geological survey schedule Earth science periodical schedule Government documents periodical schedule General science periodical schedule Earth science maps schedule Geographic schedule A geographic number, from the geographic schedule, is distinguished from other numbers in the system in that it is always enclosed in parentheses; for example, (200) is the geographic number for the United States. The geographic number is used in conjunction with the six other previously listed schedules, and it represents slightly different nuances of meanings, in respect to geographic locale, for each schedule. When used with a subject number, the geographic number indicates the country, state, province, or region in which the research was made. The subject number, 203, geology, when combined with the geographic number, (200), for example 203(200), is the classification number for library materials on the geology of the United States. The geographic number, combined with the capital letter G, for example, G(211), is the classification number for an earth science periodical issued by a geological association or university geology department in the State of Maine. When the letter S is combined with a geographic number, for example, S(276), it represents a general science periodical for a university or association in California. When the letter P is combined with a geographic number, for example, P(200), it represents a governmental periodical issued by the United States Federal Government. Geographic numbers standing alone represent classification numbers for the publications of geological surveys; for example, (200) represents publications of the U.S. Geological Survey. Map call numbers have a geographic number preceded by the capital letter M, followed by an abbreviated subject number. For example: M(200)2 where: M = Map (200) = Geographic region of the United States 2 = Abbreviation for the subject number 203— geology. The introduction, which follows this abstract, provides detailed procedures on the construction of complete call numbers for works falling into the framework of the aforesaid classification schedules. The tables following the introduction can be quickly accessed through the use of the newly expanded subject index. The purpose of this publication is to provide the earth science community with a classification and retrieval system for earth science materials, to provide sufficient explanation of its structure and use, and to enable library staff and clientele to classify or access research materials in a library collection.

Bulletin↗
USGS1967

Geohydrologic reconnaissance of the Soquel-Aptos area, Santa Cruz County, California

This report summarizes existing knowledge on the geohydrology of the Soquel-Aptos area, near, and including the eastern part, of Santa Cruz, California, and outlines work necessary for making a complete appraisal of the water resources of the area. The area is underlain mostly by marine and continental sedimentary deposits of Tertiary and Quaternary age. A small section in the northeastern part of the area on the eastern side of the San Andreas fault is underlain by sedimentary and metamorphic rocks of Cretaceous or older age. Quartz diorite, probably of Cretaceous age, underlies a considerable part of the area, but crops out only in small exposures along canyon bottom south of the Zayante fault. The Soquel-Aptos area consists of two main structural blocks?one, downthrown on the northeast side of the Zayante fault; the other, upthrown on the southwest side of the fault. The main water-bearing formations in the southwestern structural block are the Santa Margarita and Purisima Formations. The Purisima, the most widespread of these units in this area, contains water under water-table and artesian conditions and furnishes water to most wells. The water-bearing character of the rocks in the northern structural block is unknown. Presently available geohydrologic data are too limited for detailed evaluation of the ground-water potential in the Soquel-Aptos area. Work needed for a detailed evaluation includes: (1) Geophysical exploration and test drilling at selected locations, (2) pumping tests of selected existing wells and possibly of specially drilled test wells, (3) study and reconnaissance measurements of spring and streamflow, (4) chemical analysis of water samples from selected wells, and (5) establishment of a program for monitoring water quality and water levels in key wells.

California↗
USGS1977

Quality of rivers of the United States, 1975 water year; based on the National Stream Quality Accounting Network (NASQAN)

The National Stream Quality Accounting Network (NASQAN) was established by the U.S. Geological Survey to provide a nationally uniform basis for continuously assessing the quality of U.S. rivers. Stations generally are at the downstream end of hydrologic accounting units in order to measure the quantity and quality of water flowing from the units. The 1975 water year was the first year of operation of the network that represents essentially all of the accounting units and thereby describes the water- quality of the entire country. Data are available on a large number of water-quality constituents measured at 345 stations during the 1975 water year. Temperature data (usually continuous or daily measurements) from NASQAN stations were fitted to a first order harmonic equation and the parameters for the harmonic function are reported for each station. Mean temperatures generally range from 5°-10°C in the North to more than 20°C along the southern border of the continental United States and in Hawaii and Puerto Rico; means were less than 10°C at 63 stations and greater than 25°C at only 7 stations. Amplitudes of the temperature curves are greatest (greater than 12°C) for the streams at midlatitudes and in the Great and Central Plains, and they are smallest for the subtropical and cold-climate streams. Considering chemical and biological characteristics of U.S. streams as described by NASQAN data, water quality is best (by many standards) in the Northeast, Southeast, and Northwest. Waters there generally are low in dissolved solids and major and minor chemical constituents, generally are soft (except in Florida), and carry relatively small amounts of sediment. These conditions mainly reflect the geology of the regions and the relatively large amounts of precipitation. However, many of these waters show the effects of pollution and carry moderate or high levels of major nutrients and have correspondingly high populations of attached and floating plants. High counts of indicator bacteria also show signs of local pollution, particularly in regions of the country with large human and animal populations. In the Northeast, some heavy metals are at moderate levels, but not above most water-quality criteria. Rivers of most of the Mid-Continent and Southwest reflect the arid or semi-arid climate, erodible soils, and agricultural activities. They are characterized by moderate to high levels of dissolved major and minor constituents, sediment, major nutrients, and biota (floating and attached aquatic plants and indicator bacteria). In addition, the most incidences of pesticides in stream and bottom sediments were found in these regions. A special analysis was made to study the patterns of dissolved solids, major nutrients, phytoplankton, and zinc in the Mississippi River above Memphis, Tennessee. It was found that flow volume is an important factor in influencing river quality, and that stations with low concentration of major nutrients generally had low phytoplankton populations as well.

Open-File Report↗
USGS1983

Mineral potential of selected felsic plutons in the eastern and southeastern Arabian Shield, Kingdom of Saudi Arabia

Sixteen well-defined geochemical anomalies associated with felsic plutons and (or) muscovite-bearing plutons of Proterozoic age have been identified in the eastern and southeastern Arabian Shield. The majority of these plutons are highly evolved, granitophile-element-enriched muscovite-bearing granites that are weakly peraluminous. A followup study of the mineral potential of these plutons included detailed geologic mapping, extensive geochemical sampling, ground traverses, and petrographic and petrologic studies. A total of 212 samples were collected for geochemical analysis, and a lesser number were collected for petrographic studies. Most of the plutons studied are similar to metallogenically specialized granites described elsewhere in the world and found associated with deposits of tin, tungsten, or molybdenum and other rare metals. Only four of the plutons, the Sitarah, Tarban, and Gaharra monzogranites and the Bwana granite, contained highly anomalous amounts of tin, tungsten, or molybdenum and altered zones- and (or) numerous quartz veins and otherwise appeared to have noteworthy mineral potential. Additional work on at least these four plutons is suggested.

Open-File Report↗
USGS1990

U.S. Geological Survey Library Classification System

The newly revised classification system presented here is for works in the U.S. Geological Survey Library. The classification system has been developed over the years since 1904 to meet the ever changing needs of increased specialization and new areas of study in the earth sciences.

Open-File Report↗
USGS2014

Water quality at a biosolids-application area near Deer Trail, Colorado, 1993-1999

The Metro Wastewater Reclamation District (Metro District) in Denver, Colo., applied biosolids resulting from municipal sewage treatment to farmland in eastern Colorado beginning in December 1993. In mid-1993, the U.S. Geological Survey in cooperation with the Metro District began monitoring water quality at the biosolids-application area about 10 miles east of Deer Trail, Colo., to evaluate baseline water quality and the combined effects of natural processes, land uses, and biosolids applications on water quality of the biosolids application area. Water quality was characterized by baseline and post-biosolids-application sampling for selected inorganic and bacteriological constituents during 1993 through 1998, with some additional specialized sampling in 1999. The study included limited sampling of surface water and the unsaturated zone, but primarily focused on groundwater. See report for complete abstract.

Colorado↗
USGS1984

Bedrock aquifers in the northern San Rafael Swell area, Utah, with special emphasis on the Navajo Sandstone

This report presents the results of a study of bedrock aquifers in the northern San Rafael Swell area, Utah (fig. 1), with special emphasis on the Navajo Sandstone of Triassic(?) and Jurassic age. The study was made by the U.S. Geological Survey in cooperation with the Utah Department of Natural Resources, Division of Water Rights. Fieldwork was done mainly during March 1979-July 1980, with supplemental testing and observations during August-December 1980. The principal objectives of this study were to determine: (1) Well yields of the bedrock formations, (2) the capability of formations to yield, over the long term, water chemically suitable for presently (1980) known uses, and (3) effects of withdrawals from wells on the surface-water supply in the Colorado River Basin.

Utah↗
USGS1976

Problems in shallow land disposal of solid low-level radioactive waste in the united states

Disposal of solid low-level wastes containing radionuclides by burial in shallow trenches was initiated during World War II at several sites as a method of protecting personnel from radiation and isolating the radionuclides from the hydrosphere and biosphere. Today, there are 11 principal shallow-land burial sites in the United States that contain a total of more than 1.4 million cubic meters of solid wastes contaminated with a wide variety of radionuclides. Criteria for burial sites have been few and generalized and have contained only minimal hydrogeologic considerations. Waste-management practices have included the burial of small quantities of long-lived radionuclides with large volumes of wastes contaminated with shorter-lived nuclides at the same site, thereby requiring an assurance of extremely long-time containment for the entire disposal site. Studies at 4 of the 11 sites have documented the migration of radionuclides. Other sites are being studied for evidence of containment failure. Conditions at the 4 sites are summarized. In each documented instance of containment failure, ground water has probably been the medium of transport. Migrating radionuclides that have been identified include 90 Sr, 137 Cs, 106 Ru, 239 Pu, 125 Sb, 60 Co, and 3 H. Shallow land burial of solid wastes containing radionuclides can be a viable practice only if a specific site satisfies adequate hydrogeologic criteria. Suggested hydrogeologic criteria and the types of hydrogeologic data necessary for an adequate evaluation of proposed burial sites are given. It is mandatory that a concomitant inventory and classification be made of the longevity, and the physical and chemical form of the waste nuclides to be buried, in order that the anticipated waste types can be matched to the containment capability of the proposed sites. Ongoing field investigations at existing sites will provide data needed to improve containment at these sites and help develop hydrogeologic criteria for new sites. These studies have necessitated the development of special drilling, sampling, well construction, and testing techniques. A recent development in borehole geophysical techniques is downhole spectral gammaray analysis which not only locates but identifies specific radionuclides in the subsurface. Field investigations are being supplemented by laboratory studies of the hydrochemistry of the transuranic elements, the kinetics of solid-liquid phase interactions, and the potential complexing of radionuclides with organic compounds and solvents which mobilize normally highly sorbable nuclides. Theoretical studies of digital predictive solute transport models are being implemented to assure their availability for application to problems and processes identified in the field and laboratory.

Bulletin of the International Association of Engin↗
USGS2026

Region-specific understanding of virus transmission to support salmonid health at hatcheries in three regions of the Pacific Northwest, North America

Juvenile salmonid mortality due to infectious haematopoietic necrosis virus (IHNV) can be a major burden on fish hatcheries. We consider possible IHNV transmission routes and specialist–generalist patterns across three regions in the Pacific Northwest of North America: Coastal Washington and Oregon (CWO), Lower Columbia River Basin (LCRB) and Snake River Basin (SRB) to obtain multi-region inference about IHNV transmission and specialization. While individual regions have been studied previously, our consideration of three regions to identify consistent trends or localized patterns is novel. The most consistent patterns we found were that most exposure to IHNV was from migrating adult salmonids and that the IHNV lineage MD specialized in steelhead and rainbow trout. Our results were consistent with LCRB being a source of IHNV and the SRB and CWO being sinks. Results specific to particular regions include the role of local geography on exposure and influence of hatchery complexes on transmission, which highlights the need to understand local hatchery operations before disease ecology can be understood and suitable hatchery management can be planned. Results demonstrate the need for spatially and temporally explicit quantitative approaches to understand disease dynamics and inform management.

Oregon, Washington↗
USGS2024

Social vulnerability and water insecurity in the western US: A systematic review of framings, indicators, and uncertainty

Water insecurity poses a complex challenge for the western United States. Large populations are exposed and susceptible to physical and social factors that can leave them with precarious access to sufficient water supplies. Consideration of social issues by water managers can help ensure equitable supply. However, how social factors affect water insecurity conditions remains unclear. This paper reviews literature on how social vulnerability influences water insecurity in the western United States. Through a meta-analysis, indicators measuring how dimensions of social vulnerability influence water insecurity were classified and hierarchical clustering was used to characterize the relationships among these vulnerability dimensions for the largest water-users—the agricultural and municipal sectors. The study then assessed uncertainty associated with social vulnerability dimensions and their indicators. There is greatest evidence for the influence of demographic characteristics, socioeconomic status, and exposure. Indicators of these determinants were mainly significant and exacerbated conditions of water insecurity. Evidence for indicators of social dependence and special needs populations was limited, although studies assessing these factors showed significant agreement on their influence on water insecurity. Conceptual framings of social vulnerability and water security determined which indicators were measured, whereas studies of the water-use sectors focused on differing associations of social vulnerability. These findings indicate the importance of recognizing the different contexts posed by water-use sectors and diverse conceptual framings. Further, some determinants such as living conditions remain important but underexplored drivers of a community's experience of water insecurity. Understanding the uncertainty associated with these measures has implications to equitable decision making.

Water Resources Research↗
USGS2014

Consequences of habitat change and resource selection specialization for population limitation in cavity-nesting birds

Resource selection specialization may increase vulnerability of populations to environmental change. One environmental change that may negatively impact some populations is the broad decline of quaking aspen Populus tremuloides , a preferred nest tree of cavity-nesting organisms who are commonly limited by nest-site availability. However, the long-term consequences of this habitat change for cavity-nesting bird populations are poorly studied. I counted densities of woody plants and eight cavity-nesting bird species over 29 years in 15 high-elevation riparian drainages in Arizona, USA. I also studied nest-tree use and specialization over time based on 4946 nests across species. Aspen suffered a severe decline in availability over time, while understorey woody plants and canopy deciduous trees also declined. The decline of plants resulted from increased elk Cervus canadensis browsing linked to declining snowfall. Woodpeckers exhibited very high specialization (>95% of nests) on aspen for nesting, and densities of all six species declined with aspen over time. Mountain chickadees Poecile gambeli and house wrens Troglodytes aedon exhibited increasingly less specialization on aspen. Chickadees strongly increased in density over time, despite a relatively high specialization on aspen. House wren densities declined moderately over time, but nest-box addition experiments demonstrated that nest-site availability was not limiting their population. House wren densities increased with understorey vegetation recovery in elk exclosures via increased generality of nest-site use, demonstrating that the decline in understorey vegetation on the broader landscape was the cause of their population decline. Synthesis and applications . Management should target species that specialize in resource selection on a declining resource. Species with greater resource selection generalization can reduce population impacts of environmental change. Resource generalization can allow a species like the wren to take advantage of habitat refuges, such as those provided by the elk exclosures. Yet, resource generalization cannot offset the negative impacts of broad-scale declines in habitat quality on the landscape, as demonstrated by the general decline of wrens. Ultimately, aspen is an important habitat for biodiversity, and land management programmes that protect and aid recovery of aspen habitats may be critical.

Journal of Applied Ecology↗
USGS2013

Introduction to the special issue on ‘Frontiers in gas geochemistry’

The study of the geochemistry of gases pervades the Earth and Environmental Sciences. This is due in no small measure to the well-established thermodynamic properties of gases which allow their application to a variety of processes occurring over a wide spectrum of natural conditions. In this respect, both major and associated minor gases have been proven useful: indeed, the trace gases have been particularly important given their role as sensitive geochemical tracers. Examples where gas geochemistry places key constraints on geochemical processes include the degassing history of the solid Earth to form the atmosphere and oceans, the origin and migration characteristics of hydrocarbon deposits, the scale of climate variability, the P–T characteristics of geothermal reservoirs, and the dynamics of the earthquake cycle and volcanic activity, to name but a few. This volume continues this rich tradition with an eclectic selection of papers aimed at exploring and exploiting gas geochemistry over a myriad set of research themes.

Chemical Geology↗
USGS2016

Special section introduction on MicroMars to MegaMars

The study of Earth's surface and atmosphere evolved from local investigations to the incorporation of remote sensing on a global scale. The study of Mars has followed the opposite progression, beginning with telescopic observations, followed by flyby and orbital missions, landers, and finally rover missions in the last ∼20 years. This varied fleet of spacecraft (seven of which are currently operating as of this writing) provides a rich variety of datasets at spatial scales ranging from microscopic images to synoptic orbital remote sensing.

Icarus↗