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At least 1,513 records · Page 84Linked to original sources

USGS2019

A three-pipe problem: Dealing with complexity to halt amphibian declines

Natural resource managers are increasingly faced with threats to managed ecosystems that are largely outside of their control. Examples include land development, climate change, invasive species, and emerging infectious diseases. All of these are characterized by large uncertainties in timing, magnitude, and effects on species. In many cases, the conservation of species will only be possible through concerted action on the limited elements of the system that managers can control. However, before an action is taken, a manager must decide how to act, which is, if done well, not easy. In addition to dealing with uncertainty, managers must balance multiple potentially competing objectives, often in cases when the management actions available to them are limited. Guidance in making these types of challenging decisions can be found in the practice known as decision analysis. We demonstrate how using a decision-analytic approach to frame decisions can help identify and address impediments to improved conservation decision making. We demonstrate the application of decision analysis to two high-elevation amphibian species. An inadequate focus on the decision-making process, and an assumption that scientific information is adequate to solve conservation problems, must be overcome to advance the conservation of amphibians and other highly threatened taxa.

Biological Conservation↗

USGS2021

Is there enough water? How bearish and bullish outlooks are linked to decision-maker perspectives on environmental flows

Policies that mandate environmental flows (e-flows) can be powerful tools for freshwater conservation, but implementation of these policies faces many hurdles. To better understand these challenges, we explored two key questions: (1) What additional data are needed to implement e-flows? and (2) What are the major socio-political barriers to implementing e-flows? We surveyed water and natural resource decision makers in the semi-arid Red River basin, Texas-Oklahoma, USA, and used social network analysis to analyze their communication patterns. Most respondents agreed that e-flows can provide important benefits and identified the same data needs. However, respondents sharply in their beliefs on other issues, and a clustering analysis revealed two distinct groups of decision makers. One cluster of decision makers tended to be bearish, or pessimistic, and believed that: current flow conditions are not adequate, there are many serious socio-political barriers to implementation, water conflicts will likely increase in the future, and climate change is likely to exacerbate these issues. The other cluster of respondents was bullish, or optimistic: they foresaw fewer future water conflicts and fewer socio-political barriers to implementation. Despite these differences, both clusters largely identified the same data needs and barriers to e-flows implementation. Our social network analysis revealed that the frequency of communication between clusters was not significantly different than the frequency of communication within clusters. Overall, our results suggest that the different perspectives of decision-makers could complicate efforts to implement e-flows and proactively plan for climate change. However, there are opportunities for collaboration on addressing common data needs and barriers to implementation. Overall, our study provides a key socio-environmental perspective on e-flows implementation from a semi-arid and socio-politically complex river basin and contextualizes the many challenges facing e-flows implementation in river basins globally.

Journal of Environmental Management↗

USGS2013

Genomic patterns of introgression in rainbow and westslope cutthroat trout illuminated by overlapping paired-end RAD sequencing

Rapid and inexpensive methods for genomewide single nucleotide polymorphism (SNP) discovery and genotyping are urgently needed for population management and conservation. In hybridized populations, genomic techniques that can identify and genotype thousands of species-diagnostic markers would allow precise estimates of population- and individual-level admixture as well as identification of 'super invasive' alleles, which show elevated rates of introgression above the genomewide background (likely due to natural selection). Techniques like restriction-site-associated DNA (RAD) sequencing can discover and genotype large numbers of SNPs, but they have been limited by the length of continuous sequence data they produce with Illumina short-read sequencing. We present a novel approach, overlapping paired-end RAD sequencing, to generate RAD contigs of >300–400 bp. These contigs provide sufficient flanking sequence for design of high-throughput SNP genotyping arrays and strict filtering to identify duplicate paralogous loci. We applied this approach in five populations of native westslope cutthroat trout that previously showed varying (low) levels of admixture from introduced rainbow trout (RBT). We produced 77 141 RAD contigs and used these data to filter and genotype 3180 previously identified species-diagnostic SNP loci. Our population-level and individual-level estimates of admixture were generally consistent with previous microsatellite-based estimates from the same individuals. However, we observed slightly lower admixture estimates from genomewide markers, which might result from natural selection against certain genome regions, different genomic locations for microsatellites vs. RAD-derived SNPs and/or sampling error from the small number of microsatellite loci (n = 7). We also identified candidate adaptive super invasive alleles from RBT that had excessively high admixture proportions in hybridized cutthroat trout populations.

Molecular Ecology↗

USGS2016

Where the wild things are: A research agenda for studying wildlife-wilderness relationship

We explore the connection between US designated wilderness areas and wildlife with the goal of establishing a research agenda for better understanding this complex relationship. Our research agenda has two components. The first, “wildlife for wilderness,” considers the impact of wildlife on wilderness character. Whereas studies show that wildlife is important in both the perception and actual enhancement of wilderness character, the context and particulars of this relationship have not been evaluated. For instance, is knowing that a rare, native species is present in a wilderness area enough to increase perceptions of naturalness (an important wilderness quality)? Or does the public need to observe the species or its sign (e.g., tracks) for this benefit? The second part of our research agenda, “wilderness for wildlife,” considers the types of research needed to understand the impact of wilderness areas on wildlife and biodiversity conservation. Several studies show the effect of one area being designated wilderness on one wildlife species. Yet, there has been no research that examines how the networks of wilderness areas in the National Wilderness Preservation System (NWPS) are used by a species or a community of species. Furthermore, we found no studies that focused on how the NWPS affects ecological or trophic interactions among species. We hope that by providing a research agenda, we can spur multiple lines of research on the topic of wildlife and wilderness.

Journal of Forestry↗

USGS2021

U.S. Geological Survey landscape science strategy 2020–2030

Across our Nation, multiple Federal, State, Tribal, and local governments are working with stakeholders and landowners to restore, conserve, and manage lands and resources to benefit fish, wildlife, and people. One of the largest Federal efforts is led by the U.S. Department of the Interior (DOI), with multiple DOI agencies working to conserve and manage public lands, resources, and cultural heritage for the benefit and enjoyment of current and future generations. As a science provider within the DOI, the U.S. Geological Survey (USGS) has an important role in developing actionable science products that can inform decision making on public lands and across all of our Nation’s landscapes. Our landscapes and resources are undergoing continual change from a complex and interacting suite of stressors that include traditional and nontraditional land uses, a changing climate, a dynamic economy, and a culturally diverse and ever-changing society. Landscape science seeks to understand how the physical, biological, and social components of ecosystems and landscapes interact with each other and are affected by these stressors across local to global scales. The USGS has developed this landscape science strategy to focus and strengthen the agency’s efforts to inform critical conservation, restoration, and management decisions for American landscapes. The strategy directly supports the overarching 21st-century science strategy of the USGS and expands our perspective and focus on partnerships, including with internal, external, traditional, and nontraditional partners. The vision for USGS landscape science is to integrate multiple disciplines and approaches to create and deliver relevant, timely, and scientifically sound products that enable our partners to make informed decisions about how to manage complex interacting natural and human systems across changing American landscapes. This strategy seeks to leverage the expertise, data, analytical capacity, and tools of the agency and to strengthen integration of science efforts across programs and scales. A cornerstone of the strategy is working closely with landowners and resource managers to identify the science that is needed to inform management actions, and then working collaboratively with those same partners to coproduce science and data products that are timely, practical, and useful for their decision making. Many individual efforts within the USGS already embrace landscape science ideas and practices. With the development of this strategy, we are seeking to build on these efforts and to focus agency attention and expertise on expanding, connecting, and institutionalizing core practices and approaches for landscape science that produces actionable science products and tools that decision makers can use to help conserve and manage American landscapes.

Circular↗

USGS2022

Multi-species, multi-country analysis reveals North Americans are willing to pay for transborder migratory species conservation

Migratory species often provide ecosystem service benefits to people in one country while receiving habitat support in other countries. The multinational cooperation that could help ensure continued provisioning of these benefits by migration may be informed by understanding the economic values people in different countries place on the benefits they derive from migratory wildlife. We conducted contingent valuation surveys to estimate the willingness of 3733 respondents from Canada, the United States and México to invest in conservation for two disparate migratory species, the northern pintail duck Anas acuta and the Mexican free-tailed bat Tadarida brasiliensis mexicana . With zero-inflated mixed-effects negative binomial regression (explaining 87% of the variation in willingness to pay for conservation), we found that respondents from each nation, after controlling for both household income and per capita national Gross Domestic Product, were willing to invest in conservation in other countries. This willingness to pay for conservation, even when respondents knew that funds would be used to support benefits accruing primarily in other countries, demonstrates the potential for support of multinational conservation policies and programmes that direct resources to locations where the most critical habitat is located, rather than where the funding is generated. These findings could be used to support the development or expansion of new and existing international conservation programmes for migratory species.

People and Nature↗

USGS2003

Genetic variation in natural and translocated populations of the endangered Delmarva fox squirrel (Sciurus niger cinereus)

The Delmarva fox squirrel, Sciurus niger cinereus , is a federally listed endangered subspecies whose range has been reduced by 90%. In an attempt to increase both population size and range, translocation sites were established beginning in the 1960's by moving squirrels from the natural range to sites outside the current range. Although translocations have served as the primary component of the DFS recovery program, there has been very little post-release examination of the genetics of the translocation sites. In this study, we developed ten microsatellite loci, screened the three polymorphic loci, and sequenced a 330 bp fragment of the mitochondrial control region in order to assess levels of genetic variation in natural and translocated regions of Delmarva fox squirrels and to compare them to Southeastern fox squirrels ( S. n. niger ). Although we found low levels of microsatellite polymorphism, there were no differences in heterozygosity between natural and translocated regions, or between Delmarva and Southeastern fox squirrels. We found high levels of polymorphism in the mitochondrial control region. Our patterns of haplotype diversity suggest incomplete lineage sorting of the two subspecies. In general, our data suggest that the current levels of genetic variation in the translocated sites are representative of those found in the natural population, and we encourage the continued use of translocations as a major component of Delmarva fox squirrel recovery.

Conservation Genetics↗

USGS2023

Climate change as a global amplifier of human–wildlife conflict

Climate change and human–wildlife conflict are both pressing challenges for biodiversity conservation and human well-being in the Anthropocene. Climate change is a critical yet underappreciated amplifier of human–wildlife conflict, as it exacerbates resource scarcity, alters human and animal behaviours and distributions, and increases human–wildlife encounters. We synthesize evidence of climate-driven conflicts occurring among ten taxonomic orders, on six continents and in all five oceans. Such conflicts disrupt both subsistence livelihoods and industrial economies and may accelerate the rate at which human–wildlife conflict drives wildlife declines. We introduce a framework describing distinct environmental, ecological and sociopolitical pathways through which climate variability and change percolate via complex social–ecological systems to influence patterns and outcomes of human–wildlife interactions. Identifying these pathways allows for developing mitigation strategies and proactive policies to limit the impacts of human–wildlife conflict on biodiversity conservation and human well-being in a changing climate.

Nature Climate Change↗

USGS2011

Characterization of salinity and selenium loading and land-use change in Montrose Arroyo, western Colorado, from 1992 to 2010

Salinity and selenium are naturally occurring and perva-sive in the lower Gunnison River Basin of Colorado, includ-ing the watershed of Montrose Arroyo. Although some of the salinity and selenium loading in the Montrose Arroyo study area is from natural sources, additional loading has resulted from the introduction of intensive irrigation in the water-shed. With increasing land-use change and the conversion from irrigated agricultural to urban land, land managers and stakeholders need information about the long-term effects of land-use change on salinity and selenium loading. In response to the need to advance salinity and selenium science, the U.S. Geological Survey, in cooperation with the Bureau of Reclamation, Colorado River Basin Salinity Control Forum, and Colorado River Water Conservation District, developed a study to characterize salinity and selenium loading and how salinity and selenium sources may relate to land-use change in Montrose Arroyo. This report characterizes changes in salinity and selenium loading to Montrose Arroyo from March 1992 to February 2010 and the magnitude of land-use change between unirrigated desert, irrigated agricultural, and urban land-use/land-cover types, and discusses how the respective loads may relate to land-use change. Montrose Arroyo is an approximately 8-square-mile watershed in Montrose County in western Colorado. Salinity and selenium were studied in Montrose Arroyo in a 2001 study as part of a salinity- and selenium-control lateral project. The robust nature of the historical dataset indicated that Montrose Arroyo was a prime watershed for a follow-up study. Two sites from the 2001 study were used to monitor salinity and selenium loads in Montrose Arroyo in the follow-up study. Over the period of 2 water years and respective irrigation seasons (2008-2010), 27 water-quality samples were collected and streamflow measurements were made at the historical sites MA2 and MA4. Salinity and selenium concen-trations, loads, and streamflow were compared between the pre-lateral-project and post-growth periods and between the post-lateral-project and post-growth periods. No significant differences in streamflow, salinity (concen-tration and load), or selenium (concentration and load) were found at MA4 between the pre-lateral project and post-growth periods or between the post-lateral-project and post-growth periods. The statistical analysis indicated no significant dif-ferences in streamflow or salinity (both concentration and load) between the pre-lateral-project and post-growth periods or between the post-lateral-project and post-growth periods at MA2; however, selenium concentrations and loads were significantly greater between the pre-lateral-project and post-growth periods and between the post-lateral-project and post-growth periods at MA2. Land-use change between MA4 and MA2 may have contributed to the determined differences in selenium values, but the specific mechanisms causing the increases between periods are unknown. The size of the urbanized area in Montrose Arroyo was quantified for 1993, 2002, and 2009 by using a geographic information system (GIS) with imagery from the specified years. The greatest change in land use from 1993 to 2009 was the increase of urban land due to conversion from irrigated agricultural land. The conversion of previously unirrigated desert to urban land or irrigated agriculture could become more common if urbanization and development expands into the eastern part of the watershed because a majority of the un-urbanized land in eastern Montrose Arroyo is unirrigated desert. By applying GIS to the City of Montrose 2008 com-prehensive growth plan, it was estimated that approximately 786 acres of previously irrigated agricultural land will be converted to urban land and 689 acres of unirrigated desert will be converted to urban land under the plan scenario. New development on previously unirrigated land in shale areas would likely increase the potential for mobilization of sele-nium and salinity from new sources to Montrose Arroyo and the Lower Gunnison River Basin.

Scientific Investigations Report↗

USGS2025

Evaluating mark–resight survey design performance using simulation: A case study of endangered Steller sea lions

Effective monitoring is fundamental to estimating wildlife population parameters with a level of accuracy and precision that is adequate to inform management decisions. However, managers must balance trade-offs between the costs of monitoring and the resulting data quality to identify cost-effective monitoring survey designs. As such, evaluating the expected performance of monitoring surveys relative to monitoring objectives prior to survey implementation is critical. In this study, we present a simulation framework for examining the accuracy and precision of age-specific survival estimates and the probability of detecting a change in survival within the context of mark–resight monitoring programs. We consider 90 survey designs that vary across marked cohort size, marking frequency, study duration, and resight probability (i.e., detection of marked individuals). We apply this approach to the design of a monitoring program for Steller sea lions ( Eumetopias jubatus ), which is complicated by heterogeneity in rookery accessibility, population sizes, and abundance trends across the species' range. To identify cost-effective survey designs in the absence of actual survey costs, we evaluated performance with respect to a relative-costs schema. Our results highlight survey designs that reliably meet pre-defined precision targets, with precision and accuracy strongly affected by marked cohort size, marking frequency, and study duration. We found that historical mark–resight survey effort for Steller sea lions has been sufficient to reliably achieve precision targets for younger age class survival probabilities only for rookeries where abundance has been stable or increasing. In contrast, the probability of achieving survival estimates with target levels of precision at rookeries where abundance has been declining is low (<25%) due to smaller marked cohort sizes, less frequent marking at remote sites, and fewer years of available data. Our results indicate that the precision of survival estimates for subpopulations of conservation concern can be improved by longer-term monitoring, although the constraints of monitoring small populations may limit the ability of biologists to detect changes in population dynamics on management-relevant time horizons. Our survey design evaluation framework can be applied in a variety of contexts to assist natural resource managers in developing cost-effective monitoring programs.

Alaska, California, Oregon↗

USGS2005

Uses of chloride/bromide ratios in studies of potable water

In natural ground water systems, both chlorine and bromine occur primarily as monovalent anions, chloride and bromide. Although dissolution or precipitation of halite, biological activity in the root zone, anion sorption, and exchange can affect chloride/bromide ratios in some settings, movement of the ions in potable ground water is most often conservative. Atmospheric precipitation will generally have mass ratios between 50 and 150; shallow ground water, between 100 and 200; domestic sewage, between 300 and 600; water affected by dissolution of halite, between 1000 and 10,000; and summer runoff from urban streets, between 10 and 100. These, and other distinctive elemental ratios, are useful in the reconstruction of the origin and movement of ground water, as illustrated by case studies investigating sources of salinity in ground water from Alberta, Kansas, and Arizona, and infiltration rates and pathways at Yucca Mountain, Nevada.

Groundwater↗

USGS1996

Hydrogeology of the area near the J4 test cell, Arnold Air Force Base, Tennessee

The U.S. Air Force operates a major aerospace systems testing facility at Arnold Engineering Development Center (AEDC) in Coffee County, Tennessee. Dewatering operations at one of the test facilities, the J4 test cell, has affected the local ground-water hydrology. The J4 test cell is approximately 100 feet in diameter, extends approximately 250 feet below land surface, and penetrates several aquifers. Ground water is pumped continuously from around the test cell to keep the cell structurally intact. Because of the test cell's depth, dewatering has depressed water levels in the aquifers surrounding the site. The depressions that have developed exhibit anisotropy that is controlled by zones of high permeability in the aquifers. Additionally, contaminants - predominately volatile organic compounds - are present in the ground-water discharge from the test cell and in ground water at several other Installation Restoration Program (IRP) sites within the AEDC facility. The dewatering activities at J4 are drawing these contaminants from the nearby sites. The effects of dewatering at the J4 test cell were investigated by studying the lithologic and hydraulic characteristics of the aquifers, investigating the anisotropy and zones of secondary permeability using geophysical techniques, mapping the potentiometric surfaces of the underlying aquifers, and developing a conceptual model of the ground-water-flow system local to the test cell. Contour maps of the potentiometric surfaces in the shallow, Manchester, and Fort Payne aquifers (collectively, part of the Highland Rim aquifer system) show anisotropic water-level depressions centered on the J4 test cell. This anisotropy is the result of features of high permeability such as chert-gravel zones in the regolith and fractures, joints, and bedding planes in the bedrock. The presence of these features of high permeability in the Manchester aquifer results in complex flow patterns in the Highland Rim aquifers near the J4 test cell. The occurrence, distribution, and orientation of these features has a great effect on ground-water flow to the J4 test cell. The depression caused by dewatering extends out horizontally through the aquifers along the most permeable pathways. Since the aquifers above the Chattanooga Shale are not separated by distinct confining units, areas in adjacent aquifers above and below these zones of high permeability in the Manchester aquifer are also dewatered. Conditions in all Highland Rim aquifers approximate steady-state equilibrium because ground-water withdrawal at the test cell has been continuous since the late 1960's. The average ground-water discharge from the dewatering system at the J4 test cell was 105 gallons per minute, for 1992-95. The ground-water capture areas in each aquifer extend into all or parts of landfill #2 and leaching pit #2 (IRP site 1), the main testing area (IRP site 7), and the old fire training area (IRP site 10). IRP sites 8 and 12 are outside the ground-water capture areas. Of the 35 sampled wells in the J4 area, 10 produced water samples containing chlorinated organic compounds such as 1,2-dichloroethane (1,2-DCA), 1,1-dichloroethylene (1,1-DCE), and trichloroethylene (TCE) in concentrations which exceeded the Tennessee Department of Environment and Conservation Maximum Contaminant Levels (MCL's) for public water-supply systems. The highest concentrations were detected in samples from well AEDC-274 with 45 micrograms per liter (mg/L) 1,2-DCA, 320 mg/L 1,1-DCE, and 1,200 mg/L TCE. These compounds are synthetic and do not occur naturally in the environment. A sample of the ground-water discharge from the J4 test cell also contained concentrations of these compounds that exceed MCL's. Chlorinated organic compounds, including 1,2-DCA; 1,1-DCE; and TCE also have been detected at IRP sites 1, 7, 8, nd 10. The six dewatering wells surrounding the J4 test cell penetrate the Chattanooga Shale and are open to the Highland Rim aquifer system, there

Water-Resources Investigations Report↗

USGS2022

Assessing the distribution and habitat needs of the Least Darter and sympatric species of the Ozark and Arbuckle Mountain ecoregions

Limited information is known about factors driving the distribution of Least Darter in Oklahaoma. The Least Darter occurs in the Ozark Highland and Arbuckle Uplift ecoregions of Oklahoma which represent the southern extent of its range. Least Darter was historically recorded in Oklahoma from groundwater-fed streams. Our study objectives were to determine the distribution of Least Darter and a subset of congeners across the two ecoregions of Oklahoma and assess factors driving patch occupancy of Least Darter at a fine spatial scale. We used temporally replicated snorkel surveys conducted in July through October 2018-2019 to determine occupany by Least Darter. We snorkeled and seined for four species in each reach including two life stages of Smallmouth Bass (subadult and adult). We sampled 153 sites (i.e., riffle-pool complexes) nested within 61 stream reaches (i.e., 200-500-m long) in the Arbuckle Uplift and Ozark Highland ecoregions. Detection probability was similar between ecoregions. Least Darter was detected at more sites when snorkeling compared to seining (24 versus 18). Smallmouth Bass, Redspot Chub and Southern Redbelly Dace were typically 2-3 times more likely to be detected by snorkeling than by seining. We found relationships between occupancy and habitat parameters that were both shared among species but also species-specific. Least Darter occurrence probability in the Ozark Highlands was lower than in the Arbuckle Uplift. Occurrence probability was higher for subadult Smallmouth Bass and Southern Redbelly Dace in 2018 compared to 2019. Occurrence probabilities of both Least Darter and Southern Redbelly Dace were higher in cooler habitat patches. Southern Redbelly Dace was negatively associated with a higher proportion of pool habitat across a reach. Lastly, subadult Smallmouth Bass and Redspot Chub were more likely to occur in deeper pools and in larger streams (i.e., drainage area). We sampled one study reach (~150-m long with shallow riffles or a waterfall on each end) in the Arbuckle Uplift (winter and summer sampling) and Ozark Highland (winter sampling) ecoregions to determine fine-scale habitat selection during the thermally harsh seasons. We developed transects across the reaches to quantify depth, velocity, substrate, cover and water temperature. We found Least Darter used higher water column velocities and shallower water depths with little vegetation during the winter. The average water depth used was similar during summer and winter (~ 20 cm deep). Least Darter used denser vegetation during the summer and tended to avoid coarse substrates in both seasons. If the conservation of Least Darter is a management goal, actions to mitigate increasing stream water temperatures (e.g., protection of springs and riparian corridors) and protecting stream morphologies that facilitate species separations (i.e., allow for a wide range of water depth and velocities) may be beneficial (e.g., fencing cattle from streams, promoting natural bankful flows during spring)

Oklahoma↗

USGS2005

Status and conservation of the fish fauna of the Alabama River system

The Alabama River system, comprising the Alabama, Coosa, and Tallapoosa subsystems, forms the eastern portion of the Mobile River drainage. Physiographic diversity and geologic history have fostered development in the Alabama River system of globally significant levels of aquatic faunal diversity and endemism. At least 184 fishes are native to the system, including at least 33 endemic species. During the past century, dam construction for hydropower generation and navigation resulted in 16 reservoirs that inundate 44% of the length of the Alabama River system main stems. This extensive physical and hydrologic alteration has affected the fish fauna in three major ways. Diadromous and migratory species have declined precipitously. Fish assemblages persisting downstream from large main-stem dams have been simplified by loss of species unable to cope with altered flow and water quality regimes. Fish populations persisting in the headwaters and in tributaries to the mainstem reservoirs are now isolated and subjected to effects of physical and chemical habitat degradation. Ten fishes in the Alabama River system (including seven endemic species) are federally listed as threatened or endangered. Regional experts consider at least 28 additional species to be vulnerable, threatened, or endangered with extinction. Conserving the Alabama River system fish fauna will require innovative dam management, protection of streams from effects of urbanization and water supply development, and control of alien species dispersal. Failure to manage aggressively for integrity of remaining unimpounded portions of the Alabama River system will result in reduced quality of natural resources for future generations, continued assemblage simplification, and species extinction.

Book chapter↗

USGS2005

Status and conservation of the fish fauna of the Alabama River system

American Fisheries Society Symposium↗

USGS2015

Hydrodynamic modeling to evaluate the influence of constructed side-channel habitat on larval drift of pallid strugeon in the Lower Missouri River

Larval drift is a critical phase of ontogeny for many species of lotic fishes. Downstream advection and dispersion of drifting larvae or eggs is controlled by the complex interaction of flow regime, channel planform, local channel morphology, and the resulting hydraulic gradients. In many regulated rivers, channel engineering and perturbations to the flow regime may disrupt natural dispersal processes and prevent successful recruitment of native fishes. Here, we explore the influence of flow regime and channel morphology on the downstream transport, dispersion, and retention of free embryos of pallid sturgeon (Scaphirhychus albus), an endangered species endemic to the Mississippi River basin and the focus of significant conservation effort on the Missouri River. The transition from drifting free embryo to exogenously feeding larvae has been identified as a potential life stage bottleneck for the pallid sturgeon. We use a two-dimensional hydrodynamic model to evaluate the sensitivity of drift and dispersion to in-channel navigation structures, constructed shallow-water habitat, and flood hydrology. In the simulations, larvae were treated as passively drifting particles and calculated retention times were used as an index of potential for settling and retention within specific environments. During low flows, retention of larvae is promoted by shallow, low velocity conditions provided by constructed side-channel habitats. At higher flows, retention is driven by overbank flows that inundate the floodplain. Based on insights gained from the analysis of field data and modeling outputs, we consider the effects of flow regime modifications or channel re-engineering on the distribution and retention of free embryos within the Lower Missouri River.

Lower Missouri River↗

USGS2023

Techniques for restoring damaged Mojave and western Sonoran ecosystems, including those for threatened desert tortoises and Joshua trees

Ecological restoration has potential for contributing to conservation activities for threatened Mojave desert tortoises ( Gopherus agassizii ) and Joshua trees ( Yucca brevifolia , Y. jaegeriana ) and their broader ecosystems in the Mojave and western Sonoran deserts. To be effective, restoration actions deployed strategically need to halt and reverse habitat degradation, replenish or enhance resources used by both species (e.g., large shrubs for protection of tortoises and nurse plants facilitating recruitment of Joshua tree seedlings), and ideally foster resilience during likely future environmental changes. We synthesized restoration techniques and their effectiveness in the Mojave and western Sonoran deserts, provide estimated costs of candidate techniques, and anticipate future research needs for effective restoration in changing climates and environments. Over 50 published studies in the Mojave and western Sonoran deserts demonstrate that restoration can improve soil features (e.g., biocrusts), increase cover of native perennial and annual plants, enhance native seed retention and seed banks, and reduce risk of fires to conserve mature shrubland habitat. We placed restoration techniques into three categories: restoration of site environments, revegetation, and management actions to limit further disturbance and encourage recovery. Within these categories, 11 major restoration techniques (and their variations) were evaluated by at least one published study and range from geomorphic (e.g., reestablishing natural topographic patterns) and abiotic structural treatments (e.g., vertical mulching) to active revegetation (e.g., outplanting, seeding). For example, 16 outplanting studies assessed performance of 46 species to begin identifying top-performing species, associated treatments (e.g., protection from herbivory) required to aid outplant survival, and potential for outplants to trigger formation of self-sustaining populations. Creosote bush (Larrea tridentata), a shrub that tortoises use for cover and that serves as a nurse plant for Joshua tree recruitment, achieved at least 50% survival in five of eight studies. Estimated costs for restoring desert habitats varied primarily with the severity of the disturbance, site factors including the diversity of vegetation that was lost, logistical factors such as accessibility of sites (influencing transportation costs), and the cost-effectiveness of the restoration techniques chosen. The review highlights six major research and adaptive management needs for advancing desert habitat restoration. These needs include: 1) continued development of innovative techniques and bet-hedging approaches to provide managers with “tool boxes” of candidate treatments to deploy in dynamic environmental and management conditions, 2) identifying how to optimize spatial deployment of limited restoration resources, 3) developing practical techniques for reducing non-native annual grasses across spatial scales, 4) improving linkages between habitat enhancements and short- and long-term indicators of tortoise usage and responses and Joshua tree population sustainability, 5) mitigating multiple, interacting stressors with cumulative impacts, and 6) integrating biotic (e.g., seeding) and abiotic (e.g., fencing, shade structures) treatments to complement each other at site and landscape scales in dynamic climates and environments. It is possible that bet-hedging approaches employing multiple treatment types (or phased treatments across years) and greater incorporation of abiotic treatments, which are less sensitive to timing of precipitation compared with biotic treatments, will become increasingly important under future climates projected to be drier and more variable. Existing research suggests that restoration can be deployed effectively even under adverse climatic conditions, but success requires identifying suitable techniques tailored to dynamic environments.

Arizona, California, Nevada, Sonora↗

USGS2009

Conservation of northern bobwhite on private lands in Georgia, USA under uncertainty about landscape-level habitat effects

Large-scale habitat enhancement programs for birds are becoming more widespread, however, most lack monitoring to resolve uncertainties and enhance program impact over time. Georgia?s Bobwhite Quail Initiative (BQI) is a competitive, proposal-based system that provides incentives to landowners to establish habitat for northern bobwhites (Colinus virginianus). Using data from monitoring conducted in the program?s first years (1999?2001), we developed alternative hierarchical models to predict bobwhite abundance in response to program habitat modifications on local and regional scales. Effects of habitat and habitat management on bobwhite population response varied among geographical scales, but high measurement variability rendered the specific nature of these scaled effects equivocal. Under some models, BQI had positive impact at both local farm scales (1, 9 km2), particularly when practice acres were clustered, whereas other credible models indicated that bird response did not depend on spatial arrangement of practices. Thus, uncertainty about landscape-level effects of management presents a challenge to program managers who must decide which proposals to accept. We demonstrate that optimal selection decisions can be made despite this uncertainty and that uncertainty can be reduced over time, with consequent improvement in management efficacy. However, such an adaptive approach to BQI program implementation would require the reestablishment of monitoring of bobwhite abundance, an effort for which funding was discontinued in 2002. For landscape-level conservation programs generally, our approach demonstrates the value in assessing multiple scales of impact of habitat modification programs, and it reveals the utility of addressing management uncertainty through multiple decision models and system monitoring.

Landscape Ecology↗