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A brief guidance publication that explains how to evaluate reports of petroleum concentrations in animal tissue. Sections on background, sampling and handling of samples, reports and interpretation, when to analyze for hydrocarbons, and how to interpret the magnitude of the concentrations.
This river corridor assessment documents sediment mobility and river response to flood disturbance along a 140-kilometer segment of the main-stem Klamath River below Iron Gate Dam, California. Field and remote sensing methods were used to assess fundamental indicators of active sediment transport and river response to a combination of natural runoff events and reservoir releases during the study period from 2005 to 2019. Discharge measurements at two gaged sites and bed-material samples at two ungaged sites provided direct and indirect evidence of mobile bed conditions, scour and fill, and surface flushing of fine sediment. Available remote-sensing datasets collected in 2005, 2009, 2010, and 2016 were used to determine sediment storage, flood inundation boundaries, and provide indirect evidence of flood-induced scour. These datasets validate channel-maintenance flows defined by Shea and others (2016). During the study period, flows greater than or equal to 6,030 cubic feet per second mobilized the substrate, caused localized scour, and flushed fine sediment from bar surfaces. Flows greater than or equal to 10,400 cubic feet per second stripped vegetation from bars and floodplains and produced deeper scour. Flood disturbance within the study reach is produced by the combined effect of natural flows and reservoir releases, which resulted in mobile bed conditions during the study period. Periodic scour and substrate disturbance are considered by the U.S. Fish and Wildlife Service to be integral for managing disease-induced mortality of juvenile and adult salmonids. Substrate conditions conducive to parasites that host infectious diseases, particularly Ceratonova shasta, occur periodically. Additional studies are required to determine whether disease prevalence can be mitigated by well-timed reservoir releases. Study results are useful for interpreting linkages among physical and biological processes and for evaluating the effectiveness of flow management targeted to improve river bed conditions for endangered salmonid populations.
In this chapter we review the techniques used to measure two important parameters of waterfowl populations, size of breeding population and recruitment. If waterfowl are to be managed toward goals defined in terms of population sizes such as those in the recently signed North American Waterfowl Management Plan (U.S. Fish and Wildlife Service [USFWS] and Canadian Wildlife Service [CWS] 1986), there must be some measure of population size for the various species. Waterfowl managers usually measure population size during the breeding season, although for some species and in some areas winter inventories may be used. Population size is a function of natality and mortality. Other chapters in this volume deal in detail with the biology of those processes. This chapter discusses procedural aspects of measurement and reviews some of the operational systems that have been used to estimate population size and recruitment, especially in North America.
Lists alphabetically, by author, 128 informative references on the life history, biology, economic status, and control of the re-winged blackbird (Agelaius phoeniceus). A brief description is given for those reference titles that do not clearly indicate the content of the paper.
Estimating population abundances and patterns of change over time are important in both ecology and conservation. Trend assessment typically entails fitting a regression to a time series of abundances to estimate population trajectory. However, changes in abundance estimates from year-to-year across time are due to both true variation in population size (process variation) and variation due to imperfect sampling and model fit. State-space models are a relatively new method that can be used to partition the error components and quantify trends based only on process variation. We compare a state-space modelling approach with a more traditional linear regression approach to assess trends in uncorrected raw counts and detection-corrected abundance estimates of forest birds at Hakalau Forest National Wildlife Refuge, Hawai‘i. Most species demonstrated similar trends using either method. In general, evidence for trends using state-space models was less strong than for linear regression, as measured by estimates of precision. However, while the state-space models may sacrifice precision, the expectation is that these estimates provide a better representation of the real world biological processes of interest because they are partitioning process variation (environmental and demographic variation) and observation variation (sampling and model variation). The state-space approach also provides annual estimates of abundance which can be used by managers to set conservation strategies, and can be linked to factors that vary by year, such as climate, to better understand processes that drive population trends.
The Lower Rio Grande Valley (LRGV) of southern Texas is located on the United States-Mexico borderland and represents a 240-kilometer (150-mile) linear stretch that ends at the Gulf of Mexico. The LRGV represents a unique transition between temperate and tropical conditions and, as such, sustains an exceptionally high diversity of plants and animals—some of them found in few, or no other, places in the United States. Examples include Leopardus pardalis albescens (northern ocelot) and Falco femoralis septentrionalis (northern aplomado falcon)—both endangered in the United States and emblematic of the LRGV. The U.S. Fish and Wildlife Service (USFWS) manages three national wildlife refuges (Santa Ana, Lower Rio Grande Valley, and Laguna Atascosa) that together make up the South Texas Refuge Complex, which actively conserves biodiversity in about 76,006 hectares (187,815.5 acres) of native riparian and upland habitats in the LRGV. These diminished habitats harbor many rare, threatened, and endangered species. This report updates the widely used 1988 USFWS biological report titled “Tamaulipan Brushland of the Lower Rio Grande Valley of South Texas: Description, Human Impacts, and Management Options” by synthesizing nearly 400 peer-reviewed scientific publications that have resulted from biological and sociological research conducted specifically in the four Texas counties of the LRGV in the past nearly 30 years. This report has three goals: (1) synthesize scientific insights gained since 1988 related to the biology and management of the LRGV and its unique biota, focusing on flora and fauna of greatest conservation concern; (2) update ongoing challenges facing Federal and State agencies and organizations that focus on conservation or key natural resources in the LRGV; and (3) redefine conservation opportunities and land-acquisition strategies that are feasible and appropriate today, given the many new and expanding constraints that challenge conservation activities in the LRGV. The LRGV faces every contemporary conservation challenge of the 21st century, but ongoing human population growth and its associated demands, international border issues, and oil, gas, and alternative energy development dominate impacts that affect conservation in the LRGV. Continued careful syntheses of existing and future information collected in the LRGV are needed on many biological and sociological topics to guide conservation activities. Quick response will no doubt be necessary to face contemporary and difficult-to-predict challenges such as climate change, diminished water availability and quality, spread of invasive species, and habitat loss and fragmentation. Complexities of a guarded international borderland add pressure to small patches of native habitat that remain in many places of the LRGV, particularly along the Rio Grande. Large connected corridors of restored native habitat could be the best option to maintain, and even enhance, the exceptional biodiversity of the LRGV in the face of exceptional human demand.
In 1985, the U.S. Department of the Interior began a program to study the effects of irrigation drainage in the Western United States. These studies were done to determine whether irrigation drainage was causing problems related to human health, water quality, and fish and wildlife resources. Results of a study in 1991-93 of irrigation drainage associated with the Uncompahgre Project area, located in the lower Gunnison River Basin, and of the Grand Valley, located along the Colorado River, are described in this report. The focus of the report is on the sources, distribution, movement, and fate of selenium in the hydrologic and biological systems and the effects on biota. Generally, other trace- constituent concentrations in water and biota were not elevated or were not at levels of concern. Soils in the Uncompahgre Project area that primarily were derived from Mancos Shale contained the highest concentrations of total and watrer-extractable selenium. Only 5 of 128 alfalfa samples had selenium concentrations that exceeded a recommended dietary limit for livestock. Selenium data for soil and alfalfa indicate that irrigation might be mobilizing and redistributing selenium in the Uncompahgre Project area. Distribution of dissolved selenium in ground water is affected by the aqueous geochemical environment of the shallow ground- water system. Selenium concentrations were as high as 1,300 micrograms per liter in water from shallow wells. The highest concentrations of dissolved selenium were in water from wells completed in alluvium overlying the Mancos Shale of Cretaceous age; selenium concentrations were lower in water from wells completed in Mancos Shale residuum. Selenium in the study area could be mobilized by oxidation of reduced selenium, desorption from aquifer sediments, ion exchange, and dissolution. Infiltration of irrigation water and, perhaps nitrate, provide oxidizing conditions for mobilization of selenium from alluvium and shale residuum and for transport to streams and irrigation drains that are tributary to the Gunnison, Uncompahgre, and Colorado Rivers. Selenium concentrations in about 64 percent of water samples collected from the lower Gunnison River and about 50 percent of samples from the Colorado River near the Colorado-Utah State line exceeded the U.S. Environmental Protection Agency criterion of 5 micrograms per liter for protection of aquatic life. Almost all selenium concentrations in samples collected during the nonirrigation season from Mancos Shale areas exceeded the aquatic-life criterion. The maximum selenium concentrations in surface-water samples were 600 micrograms per liter in the Uncompahgre Project area and 380 micrograms per liter in the Grand Valley. Irrigation drainage from the Uncompahgre Project and the Grand Valley might account for as much as 75 percent of the selenium load in the Colorado River near the Colorado-Utah State line. The primary source areas of selenium were the eastern side of the Uncompahgre Project and the western one-half of the Grand Valley, where there is extensive irrigation on soils derived from Mancos Shale. The largest mean selenium loads from tributary drainages were 14.0 pounds per day from Loutsenhizer Arroyo in the Uncompahgre Project and 12.8 pounds per day from Reed Wash in the Grand Valley. Positive correlations between selenium loads and dissolved-solids loads could indicate that salinity-control projects designed to decrease dissolved-solids loads also could decrease selenium loads from the irrigated areas. Selenium concentrations in irrigation drainage in the Grand Valley were much higher than concentrations predicted by simple evaporative concentration of irrigation source water. Selenium probably is removed from pond water by chemical and biological processes and incorporated into bottom sediment. The maximum selenium concentration in bottom sediment was 47 micrograms per gram from a pond on the eastern side of the Uncompahgre Project.
Streambed-sediment samples from 13 sites and biological-tissue samples from 11 sites in the Gila River Basin in central Arizona were analyzed for 32 organochlorine compounds in streambed sediment and 28 compounds in biological tissue during 1996 as part of the U.S. Geological Survey's National Water-Quality Assessment program. The objectives of the study were to determine the occurrence and distribution of organochlorine compounds and their relation to land use. Sampling sites were categorized on the basis of major land uses in the basin or the source of water in the stream. Because land uses were mixed or had changed over time, some land-use categories were combined. Sites were categorized as forest/rangeland (6), forest/urban (1), urban (4), or agricultural/urban (2). Thirteen organochlorine compounds were detected in streambed-sediment samples, and 10 were detected in tissue samples. The number of compounds found in streambed-sediment samples from individual sites ranged from 0 to 10, and the range for individual tissue samples was 0 to 7. Comparison of the number of detections in streambed-sediment samples to the number of detections in tissue samples from particular sites where both were sampled yielded five instances where more compounds were detected in streambed sediment, six instances where more compounds were detected in tissue, and five instances where the number of detections in streambed sediment and tissue were equal. The frequency of detection of particular compounds for sites where both streambed sediment and tissue were sampled resulted in five compounds being detected more frequently in streambed sediment, five more frequently in tissue, and three compounds that were equally frequent in streambed sediment and in tissue. Few contaminants were detected in samples from the forest/rangeland sites; greater numbers of compounds were detected at the urban sites and at the forest/urban site. The greatest number of compounds and the highest concentrations of many contaminants were detected at agriculture/urban sites. The compound detected most frequently in streambed-sediment and tissue samples was p,p'-DDE. Streambed-sediment guideline values for the protection of aquatic life for p,p'-DDE and total DDT were exceeded at both agricultural/urban sites, The streambed-sediment guideline value for the protection of aquatic life for total chlordane was exceeded at one agricultural/urban site, one urban site, and the forest/urban site. The streambed-sediment guideline value for the protection of aquatic life for total PCB’s was exceeded at one agricultural/urban site. Guideline values for the protection of fish-eating wildlife for total DDT and for toxaphene were exceeded only in samples from the two agricultural/urban sites. The guideline value for the protection of fish-eating wildlife for total PCB’s was equaled or exceeded in samples from two sites—one urban and one agricultural/urban site. Screening values established by the U.S. Environmental Protection Agency for the protection of human health for edible portions of fish were exceeded by total DDT and by toxaphene in fish-tissue samples from both agricultural/urban sites. The human-health criterion for total PCB’s was exceeded in two fish-tissue samples from an agricultural site and from an urban site. Tissue samples analyzed in this study were for whole fish, and thus, concentration data are not entirely comparable to the screening values of the U.S. Environmental Protection Agency. Because these exceedences were an order of magnitude above the criteria, however, it is possible that concentrations in the edible portions of fish from these locations could present a human- health risk. Analyses of samples of edible portions of fish from these locations would be needed to adequately assess the presence or absence of a human-health risk. The similarity of the results of this study to the results of other studies of organochlorine compounds in the environment suggests that there is a correlation between contaminants in sediment and biological-tissue samples and land uses. As with other studies of the occurrence and distribution of organochlorine contaminants in streambed sediments and biological tissue, this study shows that many organochlorine compounds continue to persist in the environment and thus could pose a threat to aquatic life, fish-eating wildlife, and possibly to humans who consume contaminated fish.
We used structured decision-making to develop a 2-part framework to assist managers in the proactive management of disease outbreaks in Montana, USA. The first part of the framework is a model to estimate the probability of disease outbreak given field observations available to managers. The second part of the framework is decision analysis that evaluates likely outcomes of management alternatives based on the estimated probability of disease outbreak, and applies managers' values for different objectives to indicate a preferred management strategy. We used pneumonia in bighorn sheep (Ovis canadensis) as a case study for our approach, applying it to 2 populations in Montana that differed in their likelihood of a pneumonia outbreak. The framework provided credible predictions of both probability of disease outbreaks, as well as biological and monetary consequences of management actions. The structured decision-making approach to this problem was valuable for defining the challenges of disease management in a decentralized agency where decisions are generally made at the local level in cooperation with stakeholders. Our approach provides local managers with the ability to tailor management planning for disease outbreaks to local conditions. Further work is needed to refine our disease risk models and decision analysis, including robust prediction of disease outbreaks and improved assessment of management alternatives.
Changing magnitude, frequency, and timing of precipitation can influence aquatic-system hydrological, geochemical, and biological processes, in some cases resulting in system-wide shifts to an alternate state. Since the early 1990s, the southern Prairie Pothole Region has been subjected to an extended period of increased wetness resulting in marked changes to aquatic systems defining this region. We explored numerous lines of evidence to identify: (1) how the recent wet period compared to historical variability, (2) hydrological, geochemical, and biological responses, and (3) how these responses might represent a state shift in the region’s wetland ecosystems. We analyzed long-term climate records and compared how different hydrological variables responded in this wet period compared to decades before the observed shift. Additionally, we used multi-decadal records of waterfowl population and subsurface tile drain records to explore wildlife and human responses to a shifting climate. Since 1993, a novel precipitation regime corresponded with increased pond numbers, ponded-water depths, lake levels, stream flows, groundwater heights, soil-moisture, waterfowl populations, and installation of subsurface tile drains in agricultural fields. These observed changes reflect an alteration in water storage and movement across the landscape that in turn has altered solute sources and concentrations of prairie-pothole wetlands and has increased pond permanence. Combined, these changes represent significant evidence for a state shift in the ecohydrological functioning of the region’s wetland ecosystems, a shift that may require a significant refinement of the previously developed “wetland continuum” concept.
Many wildlife monitoring programmes collect annual data on population abundance. The resulting abundance estimates fluctuate over time partly because of true population change and partly because of observation error. These two components of variation can be separated by fitting the estimates to a population dynamics model within a Bayesian state-space modelling framework. By constraining the population trajectory to be biologically realistic, more precise estimates can be obtained. Independent biological knowledge can be incorporated through choice of model structure and by specifying informative prior distributions on demographic parameters. We illustrate the approach using a 31-year point transect study of the Hawai’i ’ākepa ( Loxops coccineus ). We fitted five models, each making different assumptions about how population change, recruitment and/or adult survival varied over time. Overall, the ’ākepa geometric mean growth rate was 1.02, indicating an increasing population over the 31-year time series, although there were periods of slow decline potentially associated with low recruitment and more rapid recovery associated with pulses of high recruitment. Abundance estimates derived from the population models were substantially more precise than the ‘raw’ point transect estimates: 95% credible interval (CrI) was on average 51.7% (s.d. = 14.1%) narrower.
There are two species of free-roaming feral equids in North America: horses ( Equus caballus ) and donkeys or “burros” ( E . asinus ). Both species were introduced as domestic animals to North America in the early 1500s and currently inhabit rangelands across the western United States, Canada, and all continents except Antarctica. Despite their global distribution, little is known about their fine scale spatial ecology. Contemporary research tools to assess space use include global positioning system (GPS) tracking collars, but older models were problematic due to stiff collar belting causing poor fit. We tested modern designs of GPS collars on n = 105 horses and n = 60 burros for 4 years in five populations (3 horse, 2 burro) across the western United States, to assess whether collars posed welfare risks to horses or burros. We found no difference in survival of collared versus uncollared mares and jennies, and no difference in survival of their foals. In 4036 of 4307 observations for horses (93.7%) and 2115 of 2258 observations for burros (93.6%), collars were observed symmetrical, maintaining proper fit on the neck. Fur effects from collars (sweaty neck, indented fur, broken fur) were seen in 3% of horse observations and 25% of burro observations. Superficial effects (chafes and marks on skin surface) were seen in 2% of horse observations and 11% of burro observations; no severe effects from collars were seen. Body condition was not affected by collars; mean body condition of collared horses was 4.70 ± 0.54 (mean ± s.d) and 4.71 ± 0.65 for collared burros. Behavior results indicated minimal effects; collared horses stood slightly more than uncollared, and collared burros stood and foraged more in one population, but not in the other. For 6.3% of observations of horses and 6.4% of observations of burros, we found an effect of time wearing a collar on the cumulative sum of fur effects which increased over time (burros: r s = 0.87, P = <0.0001; horses: r s = 0.31, P = 0.002). Burros also showed an increase over time in the number of superficial effects, but horses did not. Collars occasionally moved into the wrong position, shifting forward over the ears; we observed this on 19 horses and 1 burro. Of those, most collars went over the ears in summer ( n = 12). All collars were equipped with a remote release mechanism as well as a timed-release mechanism for redundancy, thus removed when observed in wrong position to avoid rubbing or discomfort. Our finding of no consequential physical effects in 98% of horse observations, and 89% of burro observations suggests the consequences of collars on free-roaming equid welfare and survival is biologically insignificant, although collars should be monitored regularly and continue to be equipped with a remote release mechanism to remove a collar if needed. With frequent welfare-driven, visual monitoring, collaring of free-roaming equids can be a safe and useful tool to increase our understanding of their spatial ecology, demography, habitat use, behavior, and interactions with other wildlife.
Eradication of Mycobacterium bovis relies on accurate detection of infected animals, including potential domestic and wildlife reservoirs. Available diagnostic tests lack the sensitivity and specificity necessary for accurate detection, particularly in infected wildlife populations. Recently, an in vitro diagnostic test for cattle which measures plasma interferon-gamma (IFN-γ) levels in blood following in vitro incubation with M. bovis purified protein derivative has been enveloped. This test appears to have increased sensitivity over traditional testing. Unfortunately, it does not detect IFN-γ from Cervidae. To begin to address this problem, the IFN-γ gene from elk ( Cervus elaphus ) was cloned, sequenced, expressed, and characterized. cDNA was cloned from mitogen stimulated peripheral blood mononuclear cells. The predicted amino acid (aa) sequence was compared to known sequences from cattle, sheep, goats, red deer ( Cervus elaphus ), humans, and mice. Biological activity of the recombinant elk IFN-γ (rElkIFN-γ) was confirmed in a vesicular stomatitis virus cytopathic effect reduction assay. Production of monoclonal antibodies to IFN-γ epitopes conserved between ruminant species could provide an important tool for the development of reliable, practical diagnostic assays for detection of a delayed type hypersensitivity response to a variety of persistent infectious agents in ruminants, including M. bovis and Brucella abortus . Moreover, development of these reagents will aid investigators in studies to explore immunological responses of elk that are associated with resistance to infectious diseases.
From butterflies to lizards and from sharks to seabirds, wildlife exhibit tactics to survive the impacts of tropical cyclones, also known as hurricanes, cyclones, or typhoons depending on where they occur. Some species seek refuge during the storm by moving, some remain in place and ride it out, and others move longer distances, avoiding the main impacts of the storm altogether. Tropical cyclones can have direct impacts on wildlife (e.g. mortality) but can also have indirect effects by altering resources and habitat, with downstream impacts on abundance and recruitment. Using examples from across taxa and ecosystems, we explore the pathways by which tropical cyclones can influence wildlife populations and communities. We describe tactics demonstrated by wildlife that enable them to survive the immediate impacts of the storm, as well as the longer-term impacts after the storm. We give examples of tropical cyclones as a selective pressure and as a facilitator for the introduction of invasive species. We also describe how tropical cyclones may provide a net benefit to some native species. The ecological and evolutionary impacts of tropical cyclones on wildlife can be complex, as they are often intertwined with concurrent pressures from land-use change, human development, and climate change. As the frequency of intense tropical cyclones is predicted to increase globally, identifying the mechanisms by which wildlife cope with such disturbances can aid in understanding and mitigating the impacts of climate change on wildlife.
The U.S. Environmental Protection Agency (EPA) is authorized under Section 404 of the Clean Water Act (33 U.S.C. 1344) to participate in the regulation of the discharge of dredged or fill material into waters of the United States. This regulatory authority is exercised in partnership with the U.S. Army Corps of Engineers, which has responsibility for permit issuance, and in consultation with the U.S. Fish and Wildlife Service and the National Marine Fisheries Service. Through amendments to the original statute, a series of legal actions and court decisions, and the development of operating guidance among the responsible agencies, Section 404 has evolved into the primary mechanism afforded Federal authorities for the protection of wetlands. EPA recognizes the importance of wetlands in achieving the goals of the Clean Water Act, which are to protect and maintain the chemical, physical, and biological integrity of the Nation’s waters. EPA Administrator Lee Thomas has identified wetlands protection as among the highest of Agency priorities. EPA recognizes that bottomland hardwood (BLH) wetlands have vital and unique attributes that, if lost, would severely impact the physical, chemical, and biological integrity of the Nation's waters. As part of a broad program to better protect the Nation's wetlands, EPA has therefore identified bottomland hardwood wetlands as a priority resource requiring special attention on a national basis. Recognizing the importance of implementing an effective, nationally consistent, and scientifically defensible regulatory program, EPA, in October 1984, issued Interim Operating Guidance to its field personnel for implementing the Section 404 regulatory program in bottomland hardwood wetlands. With the goal of improving and finalizing that guidance, EPA is sponsoring a series of workshops designed to answer key questions concerning BLH wetlands, based on the best scientific and technical information currently available. The first two workshops were directed toward summarizing existing scientific and technical knowledge concerning the functions of BLH ecosystems, the characteristics that are important to each function, and the impact of various development activities on those characteristics. The first workshop, which was held in St. Francisville, Louisiana, in December, 1984, examined a wetland zonation concept as a framework for gaining a greater understanding of BLH structure and function. The workshop set out to determine whether characterization of BLH resources as a series of relatively distinct zones, defined by concomitant variation in hydrologic regime, soils, and vegetation, might provide the basis for a useful and scientifically sound regulatory framework. For examp1e, if certain zones are of particular importance to one or more wetland functions that the Clean Water Act was intended to protect, then the zonation concept might be useful from the perspective of how various activities should be regulated. Discussions during the first workshop, however, indicated that the zonation concept provides, at best, only an incomplete picture of the structure and function of BLH ecosystems. In many cases, BLH functions are not limited to or closely correlated with particular zones and, furthermore, many factors other than zone are important determinants of BLH functions. With these responses in mind, the second workshop, held at Lake Lanier, Georgia, in July, 1985, was designed to elicit information on two questions. First, if zones are not an adequate framework for understanding the functions of BLH systems, what characteristics (predictors) can be used to assess the extent to which a particular site performs these functions? And second, what are the impacts of various development activities that often occur in BLH ecosystems on those characteristics and thus on the functions themselves? At the second workshop, individual workgroups dealing with particular subject areas (e.g., hydrology, water quality, fisheries, wildlife, ecosystem processes, and cultural/recreational/economic resources) were able to identify site characteristics that are important determinants of the performance of various functions. For example, the Hydrology Workgroup identified flood storage as one of three major hydrologic functions that BLH ecosystems perform. The workgroup then identified the most important characteristic (e.g., surface area of the site, soil saturation, and others) that determine flood storage and the likely impact of several common activities (e.g., conversion to soybean production and levee construction) on these characteristics. Some of the workgroups also provided estimates of the aggregate impact of activities, acting through all of the characteristics, on certain functions. The workgroups also identified key characteristics that could be used to identify high-value wetlands for various functions. In addition, the workgroups pointed out a number of topics needing further examination and discussion. First, all of the workgroups identified the need to develop the technical basis and information sources to address the problem of cumulative impacts in the regulatory process. Second, most of the workgroups noted the important of contextual variables in assessing the function of a particular site. For example, the location of a BLH site in relationship to other tracts of habitat is an important variable for many wildlife species. Similarly, the extent to which a site retains or transforms contaminants is depended not only on the characteristics of the site, but also on its position in a watershed relative to contaminant inputs. And finally, several of the workgroups pointed out that assessing the impact of an activity on a function is not as simple as "adding up" the impact on individual characteristics, but may depend instead on complex interactions among characteristics. Addressing these questions, as summarized in the objectives and discussions that follow, was the focus of the third workshop, the results of which are described in this report.
Biodiversity offsetting, or compensatory mitigation, is increasingly being used in temperate grassland ecosystems to compensate for unavoidable environmental damage from anthropogenic developments such as transportation infrastructure, urbanization, and energy development. Pursuit of energy independence in the United States will expand domestic energy production. Concurrent with this increased growth is increased disruption to wildlife habitats, including avian displacement from suitable breeding habitat. Recent studies at energy-extraction and -generation facilities have provided evidence for behavioral avoidance and thus reduced use of habitat by breeding waterfowl and grassland birds in the vicinity of energy infrastructure. To quantify and compensate for this loss in value of avian breeding habitat, it is necessary to determine a biologically-based currency so that the sufficiency of offsets in terms of biological equivalent value can be obtained. We describe a method for quantifying the amount of habitat needed to provide equivalent biological value for avifauna displaced by energy and transportation infrastructure, based on the ability to define five metrics: impact distance, impact area, pre-impact density, percent displacement, and offset density. We calculate percent displacement values for breeding waterfowl and grassland birds and demonstrate the applicability of our avian-impact offset method using examples for wind and oil infrastructure. We also apply our method to an example in which the biological value of the offset habitat is similar to the impacted habitat, based on similarity in habitat type (e.g., native prairie), geographical location, land use, and landscape composition, as well as to an example in which the biological value of the offset habitat is dissimilar to the impacted habitat. We provide a worksheet that informs potential users how to apply our method to their specific developments and a framework for developing decision-support tools aimed at achieving landscape-level conservation goals.
Marshes, swamps, ponds, and bogs are teeming biological nurseries for migratory birds, fish, and aquatic plants. They also provide natural flood and erosion control. These predominantly wet areas, or wetlands as they are commonly called, now represent only about 5 percent of the land surface of the lower 48 States. Out of 221 million acres of wetlands that once existed in the conterminous United States, the U.S. Fish and Wildlife Service (FWS) estimates that only about 103.3 million acres remain. Each year, development, drainage, and agriculture eliminate another 290,000 acres - an area a little less than half the size of Rhode Island. From the 1950's to the 1970's, conversion of wetlands to farmland caused 87 percent of all wetland losses. The FWS has long recognized the importance of America's wetlands because they form breeding and wintering grounds for great numbers of migratory birds. In 1977, the FWS began the National Wetlands Inventory (NWI), a systematic effort to classify and map America's remaining wetlands.
Marshes, swamps, ponds, and bogs are teeming biological nurseries for migratory birds, fish, and aquatic plants. They also provide natural flood and erosion control. These predominantly wet areas, or wetlands as they are commonly called, now represent only about 5 percent of the land surface of the lower 48 States. Out of 221 million acres of wetlands that once existed in the conterminous United States, the U.S. Fish and Wildlife Service (FWS) estimates that only about 103.3 million acres remain. Each year, development, drainage, and agriculture eliminate another 290,000 acres-an area a little less than half the size of Rhode Island. From the 1950's to the 1970's, conversion of wetlands to farmland caused 87 percent of all wetland losses. The FWS has long recognized the importance of America's wetlands because they form breeding and wintering grounds for great numbers of migratory birds. In 1977, the FWS began the National Wetlands Inventory (NWI), a systematic effort to classify and map America's remaining wetlands.