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USGS2005

Identifying calcium sources at an acid deposition-impacted spruce forest: A strontium isotope, alkaline earth element multi-tracer approach

Depletion of calcium from forest soils has important implications for forest productivity and health. Ca is available to fine feeder roots from a number of soil organic and mineral sources, but identifying the primary source or changes of sources in response to environmental change is problematic. We used strontium isotope and alkaline earth element concentration ratios of trees and soils to discern the record of Ca sources for red spruce at a base-poor, acid deposition-impacted watershed. We measured 87 Sr/ 86 Sr and chemical compositions of cross-sectional stemwood cores of red spruce, other spruce tissues and sequential extracts of co-located soil samples. 87 Sr/ 86 Sr and Sr/Ba ratios together provide a tracer of alkaline earth element sources that distinguishes the plant-available fraction of the shallow organic soils from those of deeper organic and mineral soils. Ca/Sr ratios proved less diagnostic, due to within-tree processes that fractionate these elements from each other. Over the growth period from 1870 to 1960, 87 Sr/ 86 Sr and Sr/Ba ratios of stemwood samples became progressively more variable and on average trended toward values that considered together are characteristic of the uppermost forest floor. In detail the stemwood chemistry revealed an episode of simultaneous enhanced uptake of all alkaline earth elements during the growth period from 1930 to 1960, coincident with reported local and regional increases in atmospheric inputs of inorganic acidity. We attribute the temporal trends in stemwood chemistry to progressive shallowing of the effective depth of alkaline earth element uptake by fine roots over this growth period, due to preferential concentration of fine roots in the upper forest floor coupled with reduced nutrient uptake by roots in the lower organic and upper mineral soils in response to acid-induced aluminum toxicity. Although both increased atmospheric deposition and selective weathering of Ca-rich minerals such as apatite provide possible alternative explanations of aspects of the observed trends, the chemical buffering capacity of the forest floor-biomass pool limits their effectiveness as causal mechanisms.

Biogeochemistry↗

USGS2009

Applications of a broad-spectrum tool for conservation and fisheries analysis: Aquatic gap analysis

Natural resources support all of our social and economic activities, as well as our biological existence. Humans have little control over most of the physical, biological, and sociological conditions dictating the status and capacity of natural resources in any particular area. However, the most rapid and threatening influences on natural resources typically are anthropogenic overuse and degradation. In addition, living natural resources (i.e., organisms) do not respect political boundaries, but are aware of their optimal habitat and environmental conditions. Most organisms have wider spatial ranges than the jurisdictional boundaries of environmental agencies that deal with them; even within those jurisdictions, information is patchy and disconnected. Planning and projecting effects of ecological management are difficult, because many organisms, habitat conditions, and interactions are involved. Conservation and responsible resource use involves wise management and manipulation of the aspects of the environment and biological communities that can be effectively changed. Tools and data sets that provide new insights and analysis capabilities can enhance the ability of resource managers to make wise decisions and plan effective, long-term management strategies. Aquatic gap analysis has been developed to provide those benefits. Gap analysis is more than just the assessment of the match or mis-match (i.e., gaps) between habitats of ecological value and areas with an appropriate level of environmental protection (e.g., refuges, parks, preserves), as the name suggests. Rather, a Gap Analysis project is a process which leads to an organized database of georeferenced information and previously available tools to examine conservation and other ecological issues; it provides a geographic analysis platform that serves as a foundation for aquatic ecological studies. This analytical tool box allows one to conduct assessments of all habitat elements within an area of interest. Aquatic gap analysis naturally focuses on aquatic habitats. The analytical tools are largely based on specification of the species-habitat relations for the system and organism group of interest (Morrison et al. 2003; McKenna et al. 2006; Steen et al. 2006; Sowa et al. 2007). The Great Lakes Regional Aquatic Gap Analysis (GLGap) project focuses primarily on lotic habitat of the U.S. Great Lakes drainage basin and associated states and has been developed to address fish and fisheries issues. These tools are unique because they allow us to address problems at a range of scales from the region to the stream segment and include the ability to predict species specific occurrence or abundance for most of the fish species in the study area. The results and types of questions that can be addressed provide better global understanding of the ecological context within which specific natural resources fit (e.g., neighboring environments and resources, and large and small scale processes). The geographic analysis platform consists of broad and flexible geospatial tools (and associated data) with many potential applications. The objectives of this article are to provide a brief overview of GLGap methods and analysis tools, and demonstrate conservation and planning applications of those data and tools. Although there are many potential applications, we will highlight just three: (1) support for the Eastern Brook Trout Joint Venture (EBTJV), (2) Aquatic Life classification in Wisconsin, and (3) an educational tool that makes use of Google Earth (use of trade or product names does not imply endorsement by the U.S. Government) and Internet accessibility.

Gap Analysis Bulletin↗

USGS2010

Estimation of late twentieth century land-cover change in California

We present the first comprehensive multi-temporal analysis of land-cover change for California across its major ecological regions and primary land-cover types. Recently completed satellite-based estimates of land-cover and land-use change information for large portions of the United States allow for consistent measurement and comparison across heterogeneous landscapes. Landsat data were employed within a pure-panel stratified one-stage cluster sample to estimate and characterize land-cover change for 1973–2000. Results indicate anthropogenic and natural disturbances, such as forest cutting and fire, were the dominant changes, followed by large fluctuations between agriculture and rangelands. Contrary to common perception, agriculture remained relatively stable over the 27-year period with an estimated loss of 1.0% of agricultural land. The largest net declines occurred in the grasslands/shrubs class at 5,131 km 2 and forest class at 4,722 km 2 . Developed lands increased by 37.6%, composing an estimated 4.2% of the state’s land cover by 2000.

California↗

USGS2013

Predicting breeding shorebird distributions on the Arctic Coastal Plain of Alaska

The Arctic Coastal Plain (ACP) of Alaska is an important region for millions of migrating and nesting shorebirds. However, this region is threatened by climate change and increased human development (e.g., oil and gas production) that have the potential to greatly impact shorebird populations and breeding habitat in the near future. Because historic data on shorebird distributions in the ACP are very coarse and incomplete, we sought to develop detailed, contemporary distribution maps so that the potential impacts of climate-mediated changes and development could be ascertained. To do this, we developed and mapped habitat suitability indices for eight species of shorebirds (Black-bellied Plover [Pluvialis squatarola], American Golden-Plover [Pluvialis dominica], Semipalmated Sandpiper [Calidris pusilla], Pectoral Sandpiper [Calidris melanotos], Dunlin [Calidris alpina], Long-billed Dowitcher [Limnodromus scolopaceus], Red-necked Phalarope [Phalaropus lobatus], and Red Phalarope [Phalaropus fulicarius]) that commonly breed within the ACP of Alaska. These habitat suitability models were based on 767 plots surveyed during nine years between 1998 and 2008 (surveys were not conducted in 2003 and 2005), using single-visit rapid area searches during territory establishment and incubation (8 June, 1 July). Species specific habitat suitability indices were developed and mapped using presence-only modeling techniques (partitioned Mahalanobis distance) and landscape environmental variables. For most species, habitat suitability was greater at lower elevations (i.e., near the coast and river deltas) and lower within upland habitats. Accuracy of models was high for all species, ranging from 65 -98%. Our models predicted that the largest fraction of suitable habitat for the majority of species occurred within the National Petroleum Reserve-Alaska, with highly suitable habitat also occurring within coastal areas of the Arctic National Wildlife Refuge west to Prudhoe Bay.

Alaska↗

USGS2012

Global exploration and production capacity for platinum-group metals from 1995 through 2015

Platinum-group metals (PGMs) are required in a variety of commercial, industrial, and military applications for many existing and emerging technologies, yet the United States is highly dependent on foreign sources of PGMs. Information on global exploration for PGMs since 1995 has been used in this study as a basis for identifying locations where the industry has determined that exploration has provided data sufficient to warrant development of a new mine or expansion of an existing operation or where a significant increase in capacity for PGMs is anticipated by 2015. Discussions include an overview of the industry and the selected sites, factors affecting mineral supply, and circumstances leading to the development of mineral properties with the potential to affect mineral supply. Of the 52 sites or regional operations that were considered in this analysis, 16 sites were producing before 1995, 28 sites commenced production from 1995 through 2010, and 8 sites were expected to begin production from 2011 through 2015 if development plans came to fruition. The United States imports PGMs primarily from Canada, Russia, South Africa, and Zimbabwe to meet increasing demand for these materials in a variety of specialized and high-tech applications. Feed sources of PGMs are changing in South Africa and Russia, which together accounted for about 89 percent of platinum production and 82 percent of palladium production in 2009. A greater amount of South African PGM capacity is likely to come from deeper, higher cost Upper Group Reef seam 2 deposits and deposits in the Eastern Bushveld area. Future Russian PGM capacity is likely to come from ore zones with generally lower PGM content and different platinum-to-palladium ratios than the nickel-rich ore that dominated PGM supply in the 1990s. Because PGM supply from Canada and Russia is derived as a byproduct of copper and nickel mining, the PGM supply from these countries is influenced by economic, environmental, political, and technological factors affecting exploration for and development of copper and nickel, as well as factors affecting the PGM industry. The recovery of PGMs from mill tailings since 2004 and the recycling of PGMs from catalytic converters, electrical components, and jewelry has increased since 1995 so that recycled PGMs recovered from these products accounted for about 30 percent of the supply of platinum worldwide and 29 percent of the supply of palladium worldwide in 2010. Economic and geopolitical conditions have influenced PGM supply and demand. The global recession of 2008 and 2009 temporarily decreased demand for PGMs and constrained PGM mine exploration and development, at least through 2010. Legislation regulating the structure of the mining sector has affected mining in Russia, South Africa, and Zimbabwe. Stricter vehicle emissions standards in established markets since the 1980s have led to mandatory use of pollution control devices, such as catalytic converters, that contain PGMs and are required on vehicles in expanding markets, such as China and India. It is expected that South Africa, Russia, Canada, and Zimbabwe will continue to be the principal sources of PGM at least for the next decade. Based on this review of the PGM industry, the world’s platinum capacity, expressed in terms of recoverable platinum metal, increased from 1995 through 2010 by 77,000 kilograms (kg) in South Africa, 9,000 kg in Zimbabwe, 6,000 kg in Russia, 2,000 kg in Botswana, and 2,000 kg in Canada. For the same period, palladium capacity worldwide increased by 44,000 kg in South Africa, 22,000 kg in Russia, 8,000 kg in Canada, 8,000 kg in the United States, 7,000 kg in Zimbabwe, and 3,000 kg in Botswana. Platinum capacity worldwide is expected to further increase by 24,000 kg in South Africa, 9,000 kg in Russia, 3,000 kg in Canada, and 2,000 kg in Zimbabwe from 2011 through 2015. Palladium capacity worldwide is likewise expected to increase an additional 16,000 kg in Russia, 14,000 kg in South Africa, 4,000 kg in Zimbabwe, and 1,000 kg in Canada if new or expanded mine and associated processing capacity comes into production as planned. It is likely that the magnitude of these changes in PGM capacity has been influenced by such factors as the global economy, electrical capacity shortages and mine safety concerns in South Africa, and geopolitical conditions in the major PGM producing countries.

Scientific Investigations Report↗

USGS2015

Groundwater chemistry in the vicinity of the Puna Geothermal Venture Power Plant, Hawai‘i, after two decades of production

We report chemical data for selected shallow wells and coastal springs that were sampled in 2014 to determine whether geothermal power production in the Puna area over the past two decades has affected the characteristics of regional groundwater. The samples were analyzed for major and minor chemical species, trace metals of environmental concern, stable isotopes of water, and two organic compounds (pentane and isopropanol) that are injected into the deep geothermal reservoir at the power plant. Isopropanol was not detected in any of the groundwaters; confirmed detection of pentane was restricted to one monitoring well near the power plant at a low concentration not indicative of source. Thus, neither organic compound linked geothermal operations to groundwater contamination, though chemical stability and transport velocity questions exist for both tracers. Based on our chemical analysis of geothermal fluid at the power plant and on many similar results from commercially analyzed samples, we could not show that geothermal constituents in the groundwaters we sampled came from the commercially developed reservoir. Our data are consistent with a long-held view that heat moves by conduction from the geothermal reservoir into shallow groundwaters through a zone of low permeability rock that blocks passage of geothermal water. The data do not rule out all impacts of geothermal production on groundwater. Removal of heat during production, for example, may be responsible for minor changes that have occurred in some groundwater over time, such as the decline in temperature of one monitoring well near the power plant. Such indirect impacts are much harder to assess, but point out the need for an ongoing groundwater monitoring program that should include the coastal springs down-gradient from the power plant.

Hawaii↗

USGS2013

Calcification rates of the massive coral Siderastrea siderea and crustose coralline algae along the Florida Keys (USA) outer-reef tract

Coral reefs are degrading on a global scale, and rates of reef-organism calcification are predicted to decline due to ocean warming and acidification. Systematic measurements of calcification over space and time are necessary to detect change resulting from environmental stressors. We established a network of calcification monitoring stations at four managed reefs along the outer Florida Keys Reef Tract (FKRT) from Miami to the Dry Tortugas. Eighty colonies (in two sequential sets of 40) of the reef-building coral, Siderastrea siderea , were transplanted to fixed apparatus that allowed repetitive detachment for buoyant weighing every 6 months. Algal-recruitment tiles were also deployed during each weighing interval to measure net calcification of the crustose coralline algal (CCA) community. Coral-calcification rates were an order of magnitude greater than those of CCA. Rates of coral calcification were seasonal (summer calcification was 53% greater than winter), and corals in the Dry Tortugas calcified 48% faster than those at the other three sites. Linear extension rates were also highest in the Dry Tortugas, whereas percent area of the coral skeletons excavated by bioeroding fauna was lowest. The spatial patterns in net coral calcification revealed here correlate well with Holocene reef thickness along the FKRT and, in part, support the “inimical waters hypothesis” proposed by Ginsburg, Hudson, and Shinn almost 50 yrs ago to explain reef development in this region. Due to the homogeneity in coral-calcification rates among the three main Keys sites, we recommend refinement of this hypothesis and suggest that water-quality variables (e.g., carbonate mineral saturation state, dissolved and particulate organic matter, light attenuation) be monitored alongside calcification in future studies. Our results demonstrate that our calcification monitoring network presents a feasible and worthwhile approach to quantifying potential impacts of ocean acidification, warming, and/or deteriorating water quality on the process of calcification.

Florida↗

USGS1996

Evaluation and modification of five techniques for estimating stormwater runoff for watersheds in west-central Florida

Several traditional techniques have been used for estimating stormwater runoff from ungaged watersheds. Applying these techniques to watersheds in west-central Florida requires that some of the empirical relations be extrapolated beyond tested ranges. As a result, there is uncertainty as to the accuracy of these estimates. Sixty-six storms occurring in 15 west-central Florida watersheds were initially modeled using the Rational Method, the U.S. Geological Survey Regional Regression Equations, the Natural Resources Conservation Service TR-20 model, the U.S. Army Corps of Engineers HEC-1 model, and the U.S. Environmental Protection Agency Storm Water Management Model. The techniques were applied according to the guidelines specified in the user manuals or standard engineering textbooks as though no field data were available and the selection of input parameters was not influenced by observed data. Computed estimates were compared with observed runoff to evaluate the accuracy of the techniques. One watershed was eliminated from further evaluation when it was determined that the area contributing runoff to the stream varies with the amount and intensity of rainfall. Therefore, further evaluation and modification of the input parameters were made for only 62 storms in 14 watersheds. Runoff ranged from 1.4 to 99.3 percent of rainfall. The average runoff for all watersheds included in this study was about 36 percent of rainfall. The average runoff for the urban, natural, and mixed land use watersheds was about 41, 27, and 29 percent of rainfall, respectively. Initial estimates of peak discharge using the Rational Method produced average watershed errors that ranged from an underestimation of 50.4 percent to an overestimation of 767 percent. The coefficient of runoff ranged from 0.20 to 0.60. Calibration of the technique produced average errors that ranged from an underestimation of 3.3 percent to an over estimation of 1.5 percent. The average calibrated coefficient of runoff for each watershed ranged from 0.02 to 0.72. The average values of the coefficient of runoff necessary to calibrate the urban, natural, and mixed land use watersheds were 0.39, 0.16, and 0.08, respectively. The U.S. Geological Survey regional regression equations for determining peak discharge produced errors that ranged from an underestimation of 87.3 percent to an overestimation of 1,140 percent. The regression equations for determining runoff volume produced errors that ranged from an underestimation of 95.6 percent to an overestimation of 324 percent. Regression equations developed from data used for this study produced errors that ranged between an underestimation of 82.8 percent and an overestimation of 328 percent for peak discharge and from an underestimation of 71.2 percent to an overestimation of 241 percent for runoff volume. Use of the equations developed for west-central Florida streams produced average errors for each type of watershed that were lower than errors associated with use of the U.S. Geological Survey regional equations. Initial estimates of peak discharges and runoff volumes using the Natural Resources Conservation Service TR-20 model, produced average errors of 44.6 and 42.7 percent, respectively, for all the watersheds. Curve numbers and times of concentration were adjusted to match estimated and observed peak discharges and runoff volumes. The average change in the curve number for all the watersheds was a decrease of 2.8 percent. The average change in the time of concentration was an increase of 59.2 percent. The shape of the input dimensionless unit hydrograph also had to be adjusted to match the shape and peak time of the estimated and observed flood hydrographs. Peak rate factors for the modified input dimensionless unit hydrographs ranged from 162 to 454. The mean errors for peak discharges and runoff volumes were reduced to 18.9 and 19.5 percent, respectively, using the average calibrated input parameters for each watershed. Initial estimates of peak discharges and runoff volumes using the U.S. Army Corp of Engineers Hydrologic Engineering Center-1 model, produced average errors of 105 and 26.8 percent respectively, for all the watersheds. Curve numbers and lag times were adjusted to match estimated and observed peak discharges and runoff volumes. The average change in the curve number for all the watersheds was a decrease of 2.5 percent. The average change in the lag time was an increase of 169 percent. The mean errors for peak discharges and runoff volumes were reduced to 5.8 and 1.4 percent, respectively, using the average calibrated input parameters for each watershed. The observed and estimated peak discharges and runoff volumes could be matched by adjusting curve numbers and lag time using the U.S. Army Corp of Engineers Hydrologic Engineering Center-1 model; however, the shape of the estimated flood hydrograph and timing of the peak could not be matched. The input dimensionless unit hydrograph must also be changed to increase the accuracy of the Hydrologic Engineering Center-1 model for watersheds in west-central Florida. The source code has to be modified and recompiled to enter different dimensionless unit hydrographs into the HEC-1 program. During application of the U.S. Environmental Protection Agency Storm Water Management Model, two separate infiltration methods were evaluated. Initial estimates of peak discharges and runoff volumes produced mean errors of 46.5 and 6.8 percent, respectively, for all watersheds using the Green-Ampt infiltration method, and 48.8 and 9.5 percent, respectively, using the Horton infiltration method. The mean errors were reduced to 18 and 0.3 percent for the Green-Ampt method and 20.9 and 7.2 percent for the Horton method using the average calibrated input parameters for each watershed. Estimates of peak discharges and runoff volumes were initially made for watersheds in west-central Florida using recommended procedures, then compared to observed peak discharges and runoff volumes. Subsequently, the procedures were modified to increase accuracy for this area. The same methods used during the study could be used in other parts of the world to evaluate the accuracy of standard methods for estimating stormwater runoff.

Florida↗

USGS2024

Cross-scale analysis reveals interacting predictors of annual and perennial cover in Northern Great Basin rangelands

Exotic annual grass invasion is a widespread threat to the integrity of sagebrush ecosystems in Western North America. Although many predictors of annual grass prevalence and native perennial vegetation have been identified, there remains substantial uncertainty about how regional-scale and local-scale predictors interact to determine vegetation heterogeneity, and how associations between vegetation and cattle grazing vary with environmental context. Here, we conducted a regionally extensive, one-season field survey across burned and unburned, grazed, public lands in Oregon and Idaho, with plots stratified by aspect and distance to water within pastures to capture variation in environmental context and grazing intensity. We analyzed regional-scale and local-scale patterns of annual grass, perennial grass, and shrub cover, and examined to what extent plot-level variation was contingent on pasture-level predictions of site favorability. Annual grasses were widespread at burned and unburned sites alike, contrary to assumptions of annual grasses depending on fire, and more common at lower elevations and higher temperatures regionally, as well as on warmer slopes locally. Pasture-level grazing pressure interacted with temperature such that annual grass cover was associated positively with grazing pressure at higher temperatures but associated negatively with grazing pressure at lower temperatures. This suggests that pasture-level temperature and grazing relationships with annual grass abundance are complex and context dependent, although the causality of this relationship deserves further examination. At the plot-level within pastures, annual grass cover did not vary with grazing metrics, but perennial cover did; perennial grasses, for example, had lower cover closer to water sources, but higher cover at higher dung counts within a pasture, suggesting contrasting interpretations of these two grazing proxies. Importantly for predictions of ecosystem response to temperature change, we found that pasture-level and plot-level favorability interacted: perennial grasses had a higher plot-level cover on cooler slopes, and this difference across topography was starkest in pastures that were less favorable for perennial grasses regionally. Understanding the mechanisms behind cross-scale interactions and contingent responses of vegetation to grazing in these increasingly invaded ecosystems will be critical to land management in a changing world.

Ecological Applications↗

USGS2010

Response of a macrotidal estuary to changes in anthropogenic mercury loading between 1850 and 2000

Methylmercury (MeHg) bioaccumulation in marine food webs poses risks to fish-consuming populations and wildlife. Here we develop and test an estuarine mercury cycling model for a coastal embayment of the Bay of Fundy, Canada. Mass budget calculations reveal that MeHg fluxes into sediments from settling solids exceed losses from sediment-to-water diffusion and resuspension. Although measured methylation rates in benthic sediments are high, rapid demethylation results in negligible net in situ production of MeHg. These results suggest that inflowing fluvial and tidal waters, rather than coastal sediments, are the dominant MeHg sources for pelagic marine food webs in this region. Model simulations show water column MeHg concentrations peaked in the 1960s and declined by almost 40% by the year 2000. Water column MeHg concentrations respond rapidly to changes in mercury inputs, reaching 95% of steady state in approximately 2 months. Thus, MeHg concentrations in pelagic organisms can be expected to respond rapidly to mercury loading reductions achieved through regulatory controls. In contrast MeHg concentrations in sediments have steadily increased since the onset of industrialization despite recent decreases in total mercury loading. Benthic food web MeHg concentrations are likely to continue to increase over the next several decades at present-day mercury emissions levels because the deep active sediment layer in this system contains a large amount of legacy mercury and requires hundreds of years to reach steady state with inputs.

Environmental Science & Technology↗

USGS2010

Influence of environmental factors on biotic responses to nutrient enrichment in agricultural streams

The influence of environmental factors on biotic responses to nutrients was examined in three diverse agricultural regions of the United States. Seventy wadeable sites were selected along an agricultural land use gradient while minimizing natural variation within each region. Nutrients, habitat, algae, macroinvertebrates, and macrophyte cover were sampled during a single summer low-flow period in 2006 or 2007. Continuous stream stage and water temperature were collected at each site for 30 days prior to sampling. Wide ranges of concentrations were found for total nitrogen (TN) (0.07-9.61 mg/l) and total phosphorus (TP) (<0.004-0.361 mg/l), but biotic responses including periphytic and sestonic chlorophyll a (RCHL and SCHL, respectively), and percent of stream bed with aquatic macrophyte (AQM) growth were not strongly related to concentrations of TN or TP. Pearson's coefficient of determination ( R 2 ) for nutrients and biotic measures across all sites ranged from 0.08 to 0.32 and generally were not higher within each region. The biotic measures (RCHL, SCHL, and AQM) were combined in an index to evaluate eutrophic status across sites that could have different biotic responses to nutrient enrichment. Stepwise multiple regression identified TN, percent canopy, median riffle depth, and daily percent change in stage as significant factors for the eutrophic index ( R 2 = 0.50, p < 0.001). A TN threshold of 0.48 mg/l was identified where eutrophic index scores became less responsive to increasing TN concentrations, for all sites. Multiple plant growth indicators should be used when evaluating eutrophication, especially when streams contain an abundance of macrophytes.

Arkansas;Idaho;Minnesota;Missouri;Nevada;Oklahoma;↗

USGS2019

Impacts to wildlife of wind energy siting and operation in the United States

Electricity from wind energy is a major contributor to the strategy to reduce greenhouse gas emissions from fossil fuel use and thus reduce the negative impacts of climate change. Wind energy, like all power sources, can have adverse impacts on wildlife. After nearly 25 years of focused research, these impacts are much better understood, although uncertainty remains. In this report, we summarize positive impacts of replacing fossil fuels with wind energy, while describing what we have learned and what remains uncertain about negative ecological impacts of the construction and operation of land-based and offshore wind energy on wildlife and wildlife habitat in the U.S. Finally, we propose research on ways to minimize these impacts. TO SUMMARIZE: 1 Environmental and other benefits of wind energy include near-zero greenhouse gas emissions, reductions of other common air pollutants, and little or no water use associated with producing electricity from wind energy. Various scenarios for meeting U.S. carbon emission reduction goals indicate that a four- to five-fold expansion of land-based wind energy from the current 97 gigawatts (GW) by the year 2050 is needed to minimize temperature increases and reduce the risk of climate change to people and wildlife. 2 Collision fatalities of birds and bats are the most visible and measurable impacts of wind energy production. Current estimates suggest most bird species, especially songbirds, are at low risk of population-level impacts. Raptors as a group appear more vulnerable to collisions. Population-level impacts on migratory tree bats are a concern, and better information on population sizes is needed to evaluate potential impacts to these species. Although recorded fatalities of cave-dwelling bat species are typically low at most wind energy facilities, additional mortality from collisions is a concern given major declines in these species due to white-nose syndrome (WNS). Assessments of regional and cumulative fatality impacts for birds and bats have been hampered by the lack of data from areas with a high proportion of the nation’s installed wind energy capacity. Efforts to expand data accessibility from all regions are underway, and this greater access to data along with improvements in statistical estimators should lead to improved impact assessments. 3 Habitat impacts of wind energy development are difficult to assess. An individual wind energy facility may encompass thousands of acres, but only a small percentage of the landscape within the project area is directly transformed. If a project is sited in previously undisturbed habitat, there is concern for indirect impacts, such as displacement of sensitive species. Studies to date indicate displacement of some species, but the long-term population impacts are unknown. 4 Offshore wind energy development in the U.S. is just beginning. Studies at offshore wind facilities in Europe indicate some bird and marine mammal species are displaced from project areas, but substantial uncertainty exists regarding the individual or population-level impacts of this displacement. Bird and bat collisions with offshore turbines are thought to be less common than at terrestrial facilities, but currently the tools to measure fatalities at offshore wind energy facilities are not available. The wind energy industry, state and federal agencies, conservation groups, academia, and scientific organizations have collaborated for nearly 25 years to conduct the research needed to improve our understanding of risk to wildlife and to avoid and minimize that risk. Efforts to reduce the uncertainty about wildlife risk must keep up withthe pace and scale of the need to reduce carbon emissions. This will require focusing our research priorities and increasing the rate at which we incorporate research results into the development and validation of best practices for siting and operating wind energy facilities.

Issues in Ecology↗

USGS2012

Hydrogeology, water chemistry, and transport processes in the zone of contribution of a public-supply well in Albuquerque, New Mexico, 2007-9

The National Water-Quality Assessment Program (NAWQA) of the U.S. Geological Survey began a series of groundwater studies in 2001 in representative aquifers across the Nation in order to increase understanding of the factors that affect transport of anthropogenic and natural contaminants (TANC) to public-supply wells. One of 10 regional-scale TANC studies was conducted in the Middle Rio Grande Basin (MRGB) in New Mexico, where a more detailed local-scale study subsequently investigated the hydrogeology, water chemistry, and factors affecting the transport of contaminants in the zone of contribution of one 363-meter (m) deep public-supply well in Albuquerque. During 2007 through 2009, samples were collected for the local-scale study from 22 monitoring wells and 3 public-supply (supply) wells for analysis of major and trace elements, arsenic speciation, nutrients, dissolved organic carbon, volatile organic compounds (VOCs), dissolved gases, stable isotopes, and tracers of young and old water. To study groundwater chemistry and ages at various depths within the aquifer, the monitoring wells were divided into three categories: (1) each shallow well was screened across the water table or had a screen midpoint within 18.3 m of the water level in the well; (2) each intermediate well had a screen midpoint between about 27.1 and 79.6 m below the water level in the well; and (3) each deep well had a screen midpoint about 185 m or more below the water level in the well. The 24-square-kilometer study area surrounding the "studied supply well" (SSW), one of the three supply wells, consists of primarily urban land within the MRGB, a deep alluvial basin with an aquifer composed of unconsolidated to moderately consolidated deposits of sand, gravel, silt, and clay. Conditions generally are unconfined, but are semiconfined at depth. Groundwater withdrawals for public supply have substantially changed the primary direction of flow from northeast to southwest under predevelopment conditions, to west to east under modern conditions. Analysis of age tracers indicates that groundwater from most sampled wells is dominated by old (pre-1950) water, ranging in mean age from about 4,000 years to more than 22,000 years, but includes a fraction of young (post-1950) recharge. Patterns in chemical and isotopic data are consistent with the conclusions that shallow groundwater in the area typically includes a fraction that evaporated prior to recharge and (or) flushed accumulated solutes out of the unsaturated zone during recharge, and that shallow groundwater has mixed to deeper parts of the aquifer, which receives recharge mainly by seepage from the Rio Grande. Among shallow and intermediate wells that produced water with a fraction of young recharge, that fraction ranged between 1.5 and 46 percent. Samples from the two deep wells had groundwater ages exceeding 18,000 years, with no fraction of young recharge. Two supply wells (including the SSW) had a fraction of young recharge, which ranged between about 3 and 11 percent, despite mean groundwater ages exceeding 10,000 years. The fraction of young recharge to the SSW varied seasonally, probably because seasonal pumping patterns affected local hydraulic gradients and (or) because of flow through the well bore when the SSW is not pumping. Well-bore flow data collected during winter (low-pumping season) indicated that about 61 percent of the water pumped from the SSW entered the well from the intermediate part of the aquifer, and that the remaining 39 percent entered from the deep part of the aquifer. Volatile organic compounds (VOCs) were detected in samples from most shallow and intermediate monitoring wells and from two of three supply wells, including the SSW. Detected VOCs were primarily chlorinated solvents or their degradation products. Many of the wells in which most of these VOCs were detected are located near known sites of solvent contamination that were targeted for sampling because trichloroethylene (TCE) and cis-1,2-dichloroethylene had been detected in the SSW, and several of these wells may have become contaminated at least partly because of enhanced vertical migration associated with the pumping of and (or) direct migration down deep well bores. Except for TCE in the sample from a shallow monitoring well, all detections of VOCs were at concentrations below Maximum Contaminant Levels (MCLs) set by the U.S. Environmental Protection Agency. Concentrations of all VOCs detected in the supply wells were less than one-tenth of the corresponding MCLs. However, the presence of VOCs in all but deep groundwater, including the detection of chloroform (a chlorination byproduct) in several shallow wells, indicates that groundwater in the study area commonly is affected by human activities, even to substantial depths. The only natural contaminant detected at concentrations near or above its MCL was arsenic, which has been detected at elevated concentrations across broad areas of the MRGB. Concentrations of arsenic, present primarily as arsenate, exceeded the MCL of 10 micrograms per liter (μg/L) in water from the two deep wells (one of which had the highest concentration, 35 μg/L), from one intermediate well, and from two supply wells, including the SSW. Water-quality and solid-phase data from this study are consistent with elevated arsenic concentrations in groundwater being related to pH-dependent desorption of arsenic from ferric oxyhydroxides in sediments in deep parts of the aquifer. Concentrations of nitrate ranged between 1.3 and 5.4 milligrams per liter (mg/L) in water from shallow wells screened across the water table, but were less than 0.9 mg/L in water from all but one deeper well. Nitrogen isotopes and chloride/bromide ratios for shallow wells were consistent with natural soil nitrogen. Nitrate concentrations and nitrogen isotopes indicated that denitrification is occurring at intermediate aquifer depths, and that the progress of the denitrification reaction typically is greatest for wells that include a fraction of groundwater associated with particular recharge sources or with known sites of contamination contributing organic compounds that can provide a carbon source for microbial respiration. Overall, hydrologic and chemical data from the study area indicate that young recharge is reaching the aquifer across broad areas and is migrating from shallow to intermediate depths of the aquifer as a result of mixing that is associated with human development of groundwater. Consequently, groundwater that human activities in the urban study area have affected is present at depths that are within the screened intervals of public-supply wells, resulting in detections of VOCs and implying greater vulnerability to anthropogenic contamination than might be assumed based on the dominantly old age of the regional groundwater. However, the fractions of old groundwater that public-supply wells produce substantially dilute the anthropogenic contaminants, while contributing natural contaminants (primarily arsenic) to the wells. Based on data from the SSW, vulnerability of public-supply wells to natural and anthropogenic contaminants in the area changes through time, including with seasonal changes in pumping stresses that alter the fractions of young and old water being contributed to wells.

New Mexico↗

USGS2022

A comparison of monitoring designs to assess wildlife community parameters across spatial scales

Dedicated long-term monitoring at appropriate spatial and temporal scales is necessary to understand biodiversity losses and develop effective conservation plans. Wildlife monitoring is often achieved by obtaining data at a combination of spatial scales, ranging from local to broad, to understand the status, trends, and drivers of individual species or whole communities and their dynamics. However, limited resources for monitoring necessitates tradeoffs in the scope and scale of data collection. Careful consideration of the spatial and temporal allocation of finite sampling effort is crucial for monitoring programs that span multiple spatial scales. Here we evaluate the ability of five monitoring designs - stratified random, weighted effort, indicator unit, rotating panel, and split panel - to recover parameter values that describe the status (occupancy), trends (change in occupancy), and drivers (spatially-varying covariate and an autologistic term) of wildlife communities at two spatial scales. Using an amphibian monitoring program that spans a network of U.S. National Parks as a motivating example, we conducted a simulation study for a regional community occupancy sampling program to compare the monitoring designs across varying levels of sampling effort (ranging from 10 to 50%). We found that the stratified random design outperformed the other designs for most parameters of interest at both scales, and was thus generally preferable in balancing the estimation of status, trends, and drivers across scales. However, we found that other designs had improved performance in specific situations. For example, the rotating panel design performed best at estimating spatial drivers at a regional level. Thus, our results highlight the nuanced scenarios in which various design strategies may be preferred, and offer guidance as to how managers can balance common tradeoffs in large-scale and long-term monitoring programs in terms of the specific knowledge gained. Monitoring designs that improve accuracy in parameter estimates are needed to guide conservation policy and management decisions in the face of broad-scaled environmental challenges, but the preferred design is sensitive to the specific objectives of a monitoring program.

Ecological Applications↗

USGS2007

Effects of intraborehole flow on groundwater age distribution

Environmental tracers are used to estimate groundwater ages and travel times, but the strongly heterogeneous nature of many subsurface environments can cause mixing between waters of highly disparate ages, adding additional complexity to the age-estimation process. Mixing may be exacerbated by the presence of wells because long open intervals or long screens with openings at multiple depths can transport water and solutes rapidly over a large vertical distance. The effect of intraborehole flow on groundwater age was examined numerically using direct age transport simulation coupled with the Multi-Node Well Package of MODFLOW. Ages in a homogeneous, anisotropic aquifer reached a predevelopment steady state possessing strong depth dependence. A nonpumping multi-node well was then introduced in one of three locations within the system. In all three cases, vertical transport along the well resulted in substantial changes in age distributions within the system. After a pumping well was added near the nonpumping multi-node well, ages were further perturbed by a flow reversal in the nonpumping multi-node well. Results indicated that intraborehole flow can substantially alter groundwater ages, but the effects are highly dependent on local or regional flow conditions and may change with time.

Hydrogeology Journal↗

USGS2012

Developing spatially explicit footprints of plausible land-use scenarios in the Santa Cruz Watershed, Arizona and Sonora

The SLEUTH urban growth model is applied to a binational dryland watershed to envision and evaluate plausible future scenarios of land use change into the year 2050. Our objective was to create a suite of geospatial footprints portraying potential land use change that can be used to aid binational decision-makers in assessing the impacts relative to sustainability of natural resources and potential socio-ecological consequences of proposed land-use management. Three alternatives are designed to simulate different conditions: (i) a Current Trends Scenario of unmanaged exponential growth, (ii) a Conservation Scenario with managed growth to protect the environment, and (iii) a Megalopolis Scenario in which growth is accentuated around a defined international trade corridor. The model was calibrated with historical data extracted from a time series of satellite images. Model materials, methodology, and results are presented. Our Current Trends Scenario predicts the footprint of urban growth to approximately triple from 2009 to 2050, which is corroborated by local population estimates. The Conservation Scenario results in protecting 46% more of the Evergreen class (more than 150,000 acres) than the Current Trends Scenario and approximately 95,000 acres of Barren Land, Crops, Deciduous Forest (Mesquite Bosque), Grassland/Herbaceous, Urban/Recreational Grasses, and Wetlands classes combined. The Megalopolis Scenario results also depict the preservation of some of these land-use classes compared to the Current Trends Scenario, most notably in the environmentally important headwaters region. Connectivity and areal extent of land cover types that provide wildlife habitat were preserved under the alternative scenarios when compared to Current Trends.

Arizona;Sonora↗

USGS2014

Factors affecting temporal variability of arsenic in groundwater used for drinking water supply in the United States

The occurrence of arsenic in groundwater is a recognized environmental hazard with worldwide importance and much effort has been focused on surveying and predicting where arsenic occurs. Temporal variability is one aspect of this environmental hazard that has until recently received less attention than other aspects. For this study, we analyzed 1245 wells with two samples per well. We suggest that temporal variability, often reported as affecting very few wells, is perhaps a larger issue than it appears and has been masked by datasets with large numbers of non-detect data. Although there was only a slight difference in arsenic concentration variability among samples from public and private wells (p = 0.0452), the range of variability was larger for public than for private wells. Further, we relate the variability we see to geochemical factors—primarily variability in redox—but also variability in pH and major-ion chemistry. We also show that in New England there is a weak but statistically significant indication that seasonality may have an effect on concentrations, whereby concentrations in the first two quarters of the year (January–June) are significantly lower than in the second two quarters (July–December) (p < 0.0001). In the Central Valley of California, though not statistically significant (p = 0.4169), arsenic concentration is lower in the first quarter of the year but increases in subsequent quarters. In both regions, these changes appear to follow groundwater levels. It is possible that this difference in arsenic concentrations is related to groundwater level changes, pumping stresses, evapotranspiration effects, or perhaps mixing of more oxidizing, lower pH recharge water in wetter months. Focusing on the understanding the geochemical conditions in aquifers where arsenic concentrations are concerns and causes of geochemical changes in the groundwater environment may lead to a better understanding of where and by how much arsenic will vary over time.

Science of the Total Environment↗

USGS2021

Pervasive changes in stream intermittency across the United States

Non-perennial streams are widespread, critical to ecosystems and society, and the subject of ongoing policy debate. Prior large-scale research on stream intermittency has been based on long-term averages, generally using annually aggregated data to characterize a highly variable process. As a result, it is not well understood if, how, or why the hydrology of non-perennial streams is changing. Here, we investigate trends and drivers of three intermittency signatures that describe the duration, timing, and dry-down period of stream intermittency across the continental United States (CONUS). Half of gages exhibited a significant trend through time in at least one of the three intermittency signatures, and changes in no-flow duration were most pervasive (41% of gages). Changes in intermittency were substantial for many streams, and 7% of gages exhibited changes in annual no-flow duration exceeding 100 days during the study period. Distinct regional patterns of change were evident, with widespread drying in southern CONUS and wetting in northern CONUS. These patterns are correlated with changes in aridity, though drivers of spatiotemporal variability were diverse across the three intermittency signatures. While the no-flow timing and duration were strongly related to climate, dry-down period was most strongly related to watershed land use and physiography. Our results indicate that non-perennial conditions are increasing in prevalence over much of CONUS and binary classifications of 'perennial' and 'non-perennial' are not an accurate reflection of this change. Water management and policy should reflect the changing nature and diverse drivers of changing intermittency both today and in the future.

Environmental Research Letters↗