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USGS2013

Vegetation projections for Wind Cave National Park with three future climate scenarios: Final report in completion of Task Agreement J8W07100052

Introduction The effects of climate change on the natural resources protected by Parks will likely be substantial, but geographically variable, due to local variation in climate trajectories and differences among ecosystems in their vulnerability to climate change. The projections of general circulation models (GCMs) indicate the possible magnitude and direction of future climate change for a region, but the utility of these projections for more local scales, those of individual National Park Service (NPS) units, are more uncertain because the coarse-scale GCMs lack much of the topographic detail that alters local climates. In addition, complex, interacting effects of temperature, precipitation, atmospheric CO 2 concentrations, fire, and herbivores on the vegetation that is the foundational natural resource of many NPS units present challenges in assessing the effects of projected future climates on plant and animal assemblages managed by the NPS. In spring 2009, Wind Cave National Park (WICA) served as a case study in a workshop assessing the use of scenario planning as a tool for park management planning in the face of rapidly changing climate. One outcome of the workshop was the recognized need for quantitative models to better understand the range of possible vegetation changes under different future climates and management decisions. This report addresses this need; it describes our adaptation of a dynamic global vegetation model (DGVM) to WICA vegetation and the resulting projections of future vegetation under three future climate scenarios and 11 management scenarios determined by Park natural resource managers. Wind Cave National Park lies along a narrow transition zone between the ponderosa pine (Pinus ponderosa) forests of the Black Hills and the mixed grass prairie that once extended with few interruptions over the lower, gentler terrain, subject to warmer, drier climate to the east and south of the Park. The location and character of this transition is strongly influenced by fire frequency and intensity (Brown and Sieg 1999). Furthermore, the mixed grass prairie occupies a broader transition zone between eastern tallgrass prairie and the shortgrass prairie of the western Great Plains. The dominance of species characteristic of these two prairie types varies with soil moisture availability, evaporative demand, and recent grazing history (Cogan et al. 1999). In addition, Wind Cave lies near the midpoint of a long gradient of C 3 (cool season) grass dominance to the north and C 4 (warm season) grass dominance to the south. The ecotonal position of WICA may make it particularly sensitive to climate change. For example, small changes in fire frequency and/or intensity and the vigor of trees vs. grass could dramatically shift the proportions of these two lifeforms. The Park hydrology is also sensitive to changes in the balance between infiltration of precipitation and evapotranspiration, as on average, only a small fraction of annual precipitation reaches the deeper soil layers that feed permanent streamflow. The resources at risk at Wind Cave NP include the Cave itself, as well as small backcountry caves, a genetically important bison herd, and other prairie species including the black-tailed prairie dog and endangered black-footed ferrets. All of these resources will be directly affected by climate change impacts on vegetation and hydrology. Natural resource management challenges at WICA are substantial, diverse, and intertwined. Aboveground, the park has been recognized as exemplary for its high quality vegetation (Marriot et al. 1999), though the park is relatively small for the diversity of vegetation types and species that it supports. Even without a changing climate, maintaining the integrity of the plant communities is complicated by the park’s legislated responsibility to maintain viable populations of bison, elk and pronghorn. In addition, the federally endangered black-footed ferret was recently re-introduced to the park. This species requires large extents of prairie dog towns for prey and habitat. Prairie dogs impact vegetation by constant clipping, grazing and soil disturbance, thereby affecting plant composition and productivity. Moreover, naturally high interannual climate variability and the strong influence of precipitation on grass productivity in this region combine to yield high interannual variability in the amount of forage available for the wildlife that the park is tasked to maintain. Finally, fire, which is now primarily controlled by WICA and NPS Northern Great Plains fire management programs, is intertwined with all other natural resource issues at WICA, as it can impact prairie dog colony and forest expansion, ungulate foraging behavior, invasive plant species, and hydrological processes. Although not capable of capturing all of these complexities, dynamic vegetation models do provide a means for quantitatively projecting vegetation futures in future climates under plausible fire and grazing regimes. Our work uses the DGVM MC1 to simulate the effects of future climate projections and management practices on the vegetation of WICA. MC1 is designed to project potential vegetation as influenced by natural processes and hence is appropriate for national parks, where conservation of native biota and ecosystems is of great importance. Since the initial application of MC1 to a small portion of WICA (Bachelet et al. 2000), the model has been altered to improve model performance with the inclusion of dynamic fire. Applying this improved version to WICA required substantial recalibration, during which we have made a number of improvements to MC1 that will be incorporated as permanent changes. In this report we document these changes and our calibration procedure following a brief overview of the model. We compare the projections of current vegetation to the current state of the park and present projections of vegetation dynamics under future climates downscaled from three GCMs selected to represent the existing range in available GCM projections. In doing so, we examine the consequences of different management options regarding fire and grazing, major aspects of biotic management at Wind Cave.

South Dakota↗

USGS2025

Success of restoration strategies in preventing extirpation of 2 critically endangered coral species

An unprecedented marine heatwave in 2023 caused widespread coral bleaching and mortality throughout the Caribbean. In the Florida Keys (USA), 2 foundation species, elkhorn coral ( Acropora palmata ) and staghorn coral ( Acropora cervicornis ), were severely affected. These species have been the primary focus of reef restoration in Florida for decades. Substantial losses of these species occurred in outplanted populations, in ocean-based nurseries, and among remnant wild colonies, leading to uncertainty over their future in the Florida Keys, given recent observed trends in climate conditions. However, the past 2 decades of restoration activity created a community of experts, a network of ocean-based and land-based coral-rearing infrastructure, and 2 independent land-based coral gene banks that prevented regional extirpation and preserved much of the genetic richness of these critically endangered coral species. Without the past decades of effort and the emergency response associated with the 2023 bleaching event, Florida acroporids would largely have been lost. This outcome afforded by the restoration network in Florida demonstrates the value of proactively establishing resources prior to major disturbances. We identified several critical strategies that, in the context of existing climate change, are preventing the extirpation of coral species in Florida, including extending collaborative restoration efforts to solidify a network of trained experts; establishing trust-focused relationships among management agencies and restoration groups; testing direct interventions to reduce light and temperature stress early during thermal anomalies; developing redundant ocean-based and land-based nurseries; and establishing living coral gene banks prior to major threats to prevent the extirpation of coral species.

Florida↗

USGS2019

Establishing an Agassiz’s Desert Tortoise monitoring program within the Coachella Valley multiple species habitat conservation plan area: Final report to the Coachella Valley conservation commission on work performed near the Orocopia Mountains

In support of the goals of the Coachella Valley Multiple Species Habitat Conservation Plan and Natural Community Conservation Plan (CVMSHCP/NCCP), a population of Agassiz’s desert tortoises ( Gopherus agassizii ) was marked and studied to establish a desert tortoise monitoring program near the Orocopia Mountains beginning in early 2017 and ending in the summer of 2018, following the epic drought of 2012‒2016. This effort compliments a similar effort in the nearby mouth of Cottonwood Canyon in 2015‒2016. Surveys were performed to locate tortoises, tortoise burrows, and tortoise remains at the eastern end of the CVMSHCP area north of the Orocopia Mountains and south of Interstate 10 in Riverside County, California. Although the area is considered Critical Habitat for the recovery of tortoise populations, it was heavily impacted by military training activities in the early 1940s and continues to be impacted by off-highway vehicle use. Data were collected from all live and dead tortoise specimens encountered. Only 22 live tortoises were found during transects covering approximately 21 km 2 of habitat surveyed. The sex ratio of live adult tortoises was strongly biased toward males and the sex ratio of recently (4‒5 years) dead carcasses during the long drought was strongly biased toward females. High female mortality may have resulted from the interaction of drought (including increased predation) and the reproductive strategy of tortoises. We located only one new live tortoise in the drought year of 2018 when there was no germination of winter annual food plants. A subsample of nine tortoises was outfitted with radio transmitters, and females (n = 4) were X-radiographed at approximately 10-day intervals from April–July. Mean clutch size was about 4 eggs as is typical for tortoises in this region. Additional tortoises were located opportunistically in and around the Santa Rosa Mountains (located in the southern end of the CVMSHCP area), and these tortoises were also marked for future identification. Blood samples were taken from adult tortoises and scute clips were taken from a subset of juveniles for ongoing studies to determine genetic diversity and relationships of desert tortoises within the CVMSHCP/NCCP area and beyond. The low tortoise density and high adult female mortality observed by us and others in the area may compromise the long-term viability of the population, especially given published predictions of the negative effects of future droughts on tortoises in the region.

California↗

USGS2020

Genetic analysis of the diet of red‐footed boobies (Sula sula) provisioning chicks at Ulupa'u Crater, O'ahu

The diet of red‐footed boobies ( Sula sula ) provisioning chicks was quantified using 106 regurgitations collected from 81 adults over two study years with contrasting oceanographic conditions: 2014 and 2015. A total of 1,049 prey items were sorted into three broad categories (fish, squid, and other, consisting of highly‐digested ‘mush’ and parasitic isopods) and assigned a categorical freshness value of 1 (perfect condition), 2 (superficial digestion), or 3 (highly digested and incomplete). A total of 492 undigested prey items (freshness 1 and 2) were measured and sampled for genetic identification with 401 (82%) successfully identified. Rarefaction analyses suggested robust diet sampling, with 32 documented species: 29 fishes and three squids. While the prey‐specific index of relative importance highlighted that fish dominated the diet in 2014 (32.3% fish, 15.1% squid) and in 2015 (29.9% fish, 22.3% squid), diet composition varied significantly between the two study years. The purpleback flying squid ( Stenoteuthis oulaniensis ) accounted for 98.7% (232 of 236) of the identified squid specimens. Mantle lengths were significantly longer in 2015 (7.2 ± 1.1 SD cm) than in 2014 (6.3 ± 1.7 SD cm). These results indicate a higher relative abundance and size of the epipelagic squids available to foraging red‐footed boobies in 2015, during warm‐water conditions associated with the positive phase of the El Niño Southern Oscillation. Due to their diverse diet, red‐footed boobies are useful bioindicators of epipelagic nekton assemblages during changing oceanographic conditions. Moreover, their reliance on the purpleback flying squid makes these seabirds ideal samplers of the juveniles of this poorly studied species. Understanding how interannual and longer‐term oceanographic variability affects central‐place foraging seabirds and the recruitment and abundance of their squid prey is critical for precautionary ecosystem‐based fisheries management of oceanic islands and the surrounding marine environment.

Hawaii↗

USGS2011

Geographic distribution of the mid-continent population of sandhill cranes and related management applications

The Mid-continent Population (MCP) of sandhill cranes ( Grus canadensis ) is widely hunted in North America and is separated into the Gulf Coast Subpopulation and Western Subpopulation for management purposes. Effective harvest management of the MCP requires detailed knowledge of breeding distribution of subspecies and subpopulations, chronology of their use of fall staging areas and wintering grounds, and exposure to and harvest from hunting. To address these information needs, we tagged 153 sandhill cranes with Platform Transmitting Terminals (PTTs) during 22 February–12 April 1998–2003 in the Central and North Platte River valleys of south-central Nebraska. We monitored PTT-tagged sandhill cranes, hereafter tagged cranes, from their arrival to departure from breeding grounds, during their fall migration, and throughout winter using the Argos satellite tracking system. The tracking effort yielded 74,041 useable locations over 49,350 tag days; median duration of tracking of individual cranes was 352 days and 73 cranes were tracked >12 months. Genetic sequencing of mitochondrial DNA (mtDNA) from blood samples taken from each of our random sample of tagged cranes indicated 64% were G. c. canadensis and 34% were Grus canadensis tabida . Tagged cranes during the breeding season settled in northern temperate, subarctic, and arctic North America (U.S. [23%, n = 35], Canada [57%, n = 87]) and arctic regions of northeast Asia (Russia [20%, n = 31]). Distribution of tagged cranes by breeding affiliation was as follows: Western Alaska–Siberia (WA–S, 42 ± 4% [SE]), northern Canada–Nunavut (NC–N, 21 ± 4%), west-central Canada–Alaska (WC–A, 23 ± 4%) and East-central Canada–Minnesota (EC–M, 14 ± 3%). All tagged cranes returned to the same breeding affiliation used during the previous year with a median distance of 1.60 km (range: 0.08–7.7 km, n = 53) separating sites used in year 1 and year 2. Fall staging occurred primarily in central and western Saskatchewan (69%), North Dakota (16%), southwestern Manitoba (10%), and northwestern Minnesota (3%). Space-use sharing indices showed that except for NC–N and WC–A birds, probability of finding a crane from one breeding affiliation within the home range of another breeding affiliation was low during fall staging. Tagged cranes from WC–A and EC–M breeding affiliations, on average, spent 25 and 20 days, respectively, longer on fall staging areas in the northern plains than did WA–S and NC–N birds. Cranes in the NC–N, WA–S, and WC–A affiliations spent 99%, 74%, and 64%, respectively, of winter in western Texas in Hunting Zone A; EC–M cranes spent 83% of winter along the Texas Gulf Coast in Hunting Zone C. Tagged cranes that settled within the breeding range of the Gulf Coast Subpopulation spent 28% and 42% of fall staging and winter within the range of the Western Subpopulation, indicating sufficient exchange of birds to potentially limit effectiveness of MCP harvest management. Harvests of EC–M and WC–A cranes during 1998–2003 were disproportionately high to their estimated numbers in the MCP, suggesting more conservative harvest strategies may be required for these subpopulations in the future, and for sandhill cranes to occupy major parts of their historical breeding range in the Prairie Pothole Region. Exceptionally high philopatry of MCP cranes of all 4 subpopulations to breeding sites coupled with strong linkages between crane breeding distribution, and fall staging areas and wintering grounds, provide managers guidance for targeting MCP crane harvest to meet management goals. Sufficient temporal or spatial separation exists among the 4 subpopulations on fall staging areas and wintering grounds to allow harvest to be targeted at the subpopulation level in all states and provinces (and most hunting zones within states and provinces) when conditions warrant. Knowledge gained from our study provides decision-makers in the United States, Canada, Mexico, and Russia with improved guidance for developing sound harvest regulations, focusing conservation efforts, and generating collaborative efforts among these nations on sandhill crane research and management to meet mutually important goals.

Nebraska↗

USGS2013

Roles of patch characteristics, drought frequency, and restoration in long-term trends of a widespread amphibian

Despite the high profile of amphibian declines and the increasing threat of drought and fragmentation to aquatic ecosystems, few studies have examined long-term rates of change for a single species across a large geographic area. We analyzed growth in annual egg-mass counts of the Columbia spotted frog (Rana luteiventris) across the northwestern United States, an area encompassing 3 genetic clades. On the basis of data collected by multiple partners from 98 water bodies between 1991 and 2011, we used state-space and linear-regression models to measure effects of patch characteristics, frequency of summer drought, and wetland restoration on population growth. Abundance increased in the 2 clades with greatest decline history, but declined where populations are considered most secure. Population growth was negatively associated with temporary hydroperiods and landscape modification (measured by the human footprint index), but was similar in modified and natural water bodies. The effect of drought was mediated by the size of the water body: populations in large water bodies maintained positive growth despite drought, whereas drought magnified declines in small water bodies. Rapid growth in restored wetlands in areas of historical population declines provided strong evidence of successful management. Our results highlight the importance of maintaining large areas of habitat and underscore the greater vulnerability of small areas of habitat to environmental stochasticity. Similar long-term growth rates in modified and natural water bodies and rapid, positive responses to restoration suggest pond construction and other forms of management can effectively increase population growth. These tools are likely to become increasingly important to mitigate effects of increased drought expected from global climate change.

Conservation Biology↗

USGS2018

Greater sage-grouse science (2015–17)—Synthesis and potential management implications

Executive Summary The greater sage-grouse ( Centrocercus urophasianus ; hereafter called “sage-grouse”), a species that requires sagebrush (Artemisia spp.), has experienced range-wide declines in its distribution and abundance. These declines have prompted substantial research and management investments to improve the understanding of sage-grouse and its habitats and reverse declines in distribution and population numbers. Over the past two decades, the U.S. Fish and Wildlife Service (USFWS) has responded to eight petitions to list the sage-grouse under the Endangered Species Act of 1973, with the completion of the most recent listing determination in September 2015. At that time, the USFWS determined that the sage-grouse did not warrant a listing, primarily because of the large scale science-based conservation and planning efforts completed or started by Federal, State, local agencies, private landowners, and other entities across the range. The planning efforts culminated in the development of the 2015 Bureau of Land Management (BLM) and U.S. Forest Service Land Use Plan Amendments, which provided regulatory certainty and commitment from Federal land-management agencies to limit, mitigate, and track anthropogenic disturbance and implement other sage-grouse conservation measures. After these policy decisions, the scientific community has continued to refine and expand the knowledge available to inform implementation of management actions, increase the efficiency and effectiveness of those actions, and continue developing an overall understanding of sage-grouse populations, habitat requirements, and their response to human activity and other habitat changes. The development of science has been driven by multiple prioritization documents including the “Greater Sage-Grouse National Research Strategy” (Hanser and Manier, 2013) and, most recently, the “Integrated Rangeland Fire Management Strategy Actionable Science Plan” (Integrated Rangeland Fire Management Strategy Actionable Science Plan Team, 2016). In October 2017, after a review of the 2015 Federal plans relative to State sage-grouse plans, in accordance with Secretarial Order 3353, the BLM issued a notice of intent to consider whether to amend some, all, or none of the 2015 land use plans. At that time, the BLM requested the U.S. Geological Survey (USGS) to inform this effort through the development of an annotated bibliography of sage-grouse science published since January 2015 and a report that synthesized and outlined the potential management implications of this new science. Development of the annotated bibliography resulted in the identification and summarization of 169 peer-reviewed scientific publications and reports. The USGS then convened an interagency team (hereafter referred to as the “team”) to develop this report that focuses on the primary topics of importance to the ongoing management of sage-grouse and their habitats. The team developed this report in a three-step process. First, the team identified six primary topic areas for discussion based on the members’ collective knowledge regarding sage-grouse, their habitats, and threats to either or both. Second, the team reviewed all the material in the “Annotated Bibliography of Scientific Research on Greater Sage-Grouse Published since January 2015” to identify the science that addressed the topics. Third, team members discussed the science related to each topic, evaluated the consistency of the science with existing knowledge before 2015, and summarized the potential management implications of this science. The six primary topics identified by the team were: Multiscale habitat suitability and mapping tools Discrete anthropogenic activities Diffuse activities Fire and invasive species Restoration effectiveness Population estimation and genetics

Open-File Report↗

USGS2018

Assessing historical and projected carbon balance of Alaska: A synthesis of results and policy/management implications

We summarize the results of a recent interagency assessment of land carbon dynamics in Alaska, in which carbon dynamics were estimated for all major terrestrial and aquatic ecosystems for the historical period (1950–2009) and a projection period (2010–2099). Between 1950 and 2009, upland and wetland (i.e., terrestrial) ecosystems of the state gained 0.4 Tg C/yr (0.1% of net primary production, NPP), resulting in a cumulative greenhouse gas radiative forcing of 1.68 × 10 −3 W/m 2 . The change in carbon storage is spatially variable with the region of the Northwest Boreal Landscape Conservation Cooperative (LCC) losing carbon because of fire disturbance. The combined carbon transport via various pathways through inland aquatic ecosystems of Alaska was estimated to be 41.3 Tg C/yr (17% of terrestrial NPP). During the projection period (2010–2099), carbon storage of terrestrial ecosystems of Alaska was projected to increase (22.5–70.0 Tg C/yr), primarily because of NPP increases of 10–30% associated with responses to rising atmospheric CO 2 , increased nitrogen cycling, and longer growing seasons. Although carbon emissions to the atmosphere from wildfire and wetland CH 4 were projected to increase for all of the climate projections, the increases in NPP more than compensated for those losses at the statewide level. Carbon dynamics of terrestrial ecosystems continue to warm the climate for four of the six future projections and cool the climate for only one of the projections. The attribution analyses we conducted indicated that the response of NPP in terrestrial ecosystems to rising atmospheric CO 2 (~5% per 100 ppmv CO 2 ) saturates as CO 2 increases (between approximately +150 and +450 ppmv among projections). This response, along with the expectation that permafrost thaw would be much greater and release large quantities of permafrost carbon after 2100, suggests that projected carbon gains in terrestrial ecosystems of Alaska may not be sustained. From a national perspective, inclusion of all of Alaska in greenhouse gas inventory reports would ensure better accounting of the overall greenhouse gas balance of the nation and provide a foundation for considering mitigation activities in areas that are accessible enough to support substantive deployment.

Alaska↗

USGS2016

Inter-population differences in salinity tolerance and osmoregulation of juvenile wild and hatchery-born Sacramento splittail

The Sacramento splittail ( Pogonichthys macrolepidotus ) is a minnow endemic to the highly modified San Francisco Estuary of California, USA and its associated rivers and tributaries. This species is composed of two genetically distinct populations, which, according to field observations and otolith strontium signatures, show largely allopatric distribution patterns as recently hatched juveniles. Juvenile Central Valley splittail are found primarily in the nearly fresh waters of the Sacramento and San Joaquin rivers and their tributaries, whereas San Pablo juveniles are found in the typically higher-salinity waters (i.e. up to 10‰) of the Napa and Petaluma Rivers. As the large salinity differences between young-of-year habitats may indicate population-specific differences in salinity tolerance, we hypothesized that juvenile San Pablo and Central Valley splittail populations differ in their response to salinity. In hatchery-born and wild-caught juvenile San Pablo splittail, we found upper salinity tolerances, where mortalities occurred within 336 h of exposure to 16‰ or higher, which was higher than the upper salinity tolerance of 14‰ for wild-caught juvenile Central Valley splittail. This, in conjunction with slower recovery of plasma osmolality, but not ion levels, muscle moisture or gill Na + ,K + -ATPase activity, in Central Valley relative to San Pablo splittail during osmoregulatory disturbance provides some support for our hypothesis of inter-population variation in salinity tolerance and osmoregulation. The modestly improved salinity tolerance of San Pablo splittail is consistent with its use of higher-salinity habitats. Although confirmation of the putative adaptive difference through further studies is recommended, this may highlight the need for population-specific management considerations.

California↗

USGS2016

Consequences of changes in vegetation and snow cover for climate feedbacks in Alaska and northwest Canada

Changes in vegetation and snow cover may lead to feedbacks to climate through changes in surface albedo and energy fluxes between the land and atmosphere. In addition to these biogeophysical feedbacks, biogeochemical feedbacks associated with changes in carbon (C) storage in the vegetation and soils may also influence climate. Here, using a transient biogeographic model (ALFRESCO) and an ecosystem model (DOS-TEM), we quantified the biogeophysical feedbacks due to changes in vegetation and snow cover across continuous permafrost to non-permafrost ecosystems in Alaska and northwest Canada. We also computed the changes in carbon storage in this region to provide a general assessment of the direction of the biogeochemical feedback. We considered four ecoregions, or Landscape Conservations Cooperatives (LCCs; including the Arctic, North Pacific, Western Alaska, and Northwest Boreal). We examined the 90 year period from 2010 to 2099 using one future emission scenario (A1B), under outputs from two general circulation models (MPI-ECHAM5 and CCCMA-CGCM3.1). We found that changes in snow cover duration, including both the timing of snowmelt in the spring and snow return in the fall, provided the dominant positive biogeophysical feedback to climate across all LCCs, and was greater for the ECHAM (+3.1 W m −2 decade −1 regionally) compared to the CCCMA (+1.3 W m −2 decade −1 regionally) scenario due to an increase in loss of snow cover in the ECHAM scenario. The greatest overall negative feedback to climate from changes in vegetation cover was due to fire in spruce forests in the Northwest Boreal LCC and fire in shrub tundra in the Western LCC (−0.2 to −0.3 W m −2 decade −1 ). With the larger positive feedbacks associated with reductions in snow cover compared to the smaller negative feedbacks associated with shifts in vegetation, the feedback to climate warming was positive (total feedback of +2.7 W m −2 decade regionally in the ECHAM scenario compared to +0.76 W m −2 decade regionally in the CCCMA scenario). Overall, increases in C storage in the vegetation and soils across the study region would act as a negative feedback to climate. By exploring these feedbacks to climate, we can reach a more integrated understanding of the manner in which climate change may impact interactions between high-latitude ecosystems and the global climate system.

Environmental Research Letters↗

USGS2017

The role of driving factors in historical and projected carbon dynamics of upland ecosystems in Alaska

It is important to understand how upland ecosystems of Alaska, which are estimated to occupy 84% of the state (i.e., 1,237,774 km 2 ), are influencing and will influence state‐wide carbon (C) dynamics in the face of ongoing climate change. We coupled fire disturbance and biogeochemical models to assess the relative effects of changing atmospheric carbon dioxide (CO 2 ), climate, logging and fire regimes on the historical and future C balance of upland ecosystems for the four main Landscape Conservation Cooperatives (LCCs) of Alaska. At the end of the historical period (1950–2009) of our analysis, we estimate that upland ecosystems of Alaska store ~50 Pg C (with ~90% of the C in soils), and gained 3.26 Tg C/yr. Three of the LCCs had gains in total ecosystem C storage, while the Northwest Boreal LCC lost C (−6.01 Tg C/yr) because of increases in fire activity. Carbon exports from logging affected only the North Pacific LCC and represented less than 1% of the state's net primary production (NPP). The analysis for the future time period (2010–2099) consisted of six simulations driven by climate outputs from two climate models for three emission scenarios. Across the climate scenarios, total ecosystem C storage increased between 19.5 and 66.3 Tg C/yr, which represents 3.4% to 11.7% increase in Alaska upland's storage. We conducted additional simulations to attribute these responses to environmental changes. This analysis showed that atmospheric CO 2 fertilization was the main driver of ecosystem C balance. By comparing future simulations with constant and with increasing atmospheric CO 2 , we estimated that the sensitivity of NPP was 4.8% per 100 ppmv, but NPP becomes less sensitive to CO 2 increase throughout the 21st century. Overall, our analyses suggest that the decreasing CO 2 sensitivity of NPP and the increasing sensitivity of heterotrophic respiration to air temperature, in addition to the increase in C loss from wildfires weakens the C sink from upland ecosystems of Alaska and will ultimately lead to a source of CO 2 to the atmosphere beyond 2100. Therefore, we conclude that the increasing regional C sink we estimate for the 21st century will most likely be transitional.

Alaska↗

USGS2020

Inter-population differences in salinity tolerance of adult wild Sacramento splittail: osmoregulatory and metabolic responses to salinity

The Sacramento splittail ( Pogonichthys macrolepidotus ) is composed of two genetically distinct populations endemic to the San Francisco Estuary (SFE). The allopatric upstream spawning habitat of the Central Valley (CV) population connects with the sympatric rearing grounds via relatively low salinity waters, whereas the San Pablo (SP) population must pass through the relatively high-salinity Upper SFE to reach its allopatric downstream spawning habitat. We hypothesize that if migration through SFE salinities to SP spawning grounds is more challenging for adult CV than SP splittail, then salinity tolerance, osmoregulatory capacity, and metabolic responses to salinity will differ between populations. Osmoregulatory disturbances, assessed by measuring plasma osmolality and ions, muscle moisture and Na + -K + -ATPase activity after 168 to 336 h at 11‰ salinity, showed evidence for a more robust osmoregulatory capacity in adult SP relative to CV splittail. While both resting and maximum metabolic rates were elevated in SP splittail in response to increased salinity, CV splittail metabolic rates were unaffected by salinity. Further, the calculated difference between resting and maximum metabolic values, aerobic scope, did not differ significantly between populations. Therefore, improved osmoregulation came at a metabolic cost for SP splittail but was not associated with negative impacts on scope for aerobic metabolism. These results suggest that SP splittail may be physiologically adjusted to allow for migration through higher-salinity waters. The trends in interpopulation variation in osmoregulatory and metabolic responses to salinity exposures support our hypothesis of greater salinity-related challenges to adult CV than SP splittail migration and are consistent with our previous findings for juvenile splittail populations, further supporting our recommendation of population-specific management.

California↗

USGS2004

Demographic estimation methods for plants with dormancy

Demographic studies in plants appear simple because unlike animals, plants do not run away. Plant individuals can be marked with, e.g., plastic tags, but often the coordinates of an individual may be sufficient to identify it. Vascular plants in temperate latitudes have a pronounced seasonal life–cycle, so most plant demographers survey their study plots once a year often during or shortly after flowering. Life–states are pervasive in plants, hence the results of a demographic study for an individual can be summarized in a familiar encounter history, such as 0VFVVF000. A zero means that an individual was not seen in a year and a letter denotes its state for years when it was seen aboveground. V and F here stand for vegetative and flowering states, respectively. Probabilities of survival and state transitions can then be obtained by mere counting. Problems arise when there is an unobservable dormant state, i.e., when plants may stay belowground for one or more growing seasons. Encounter histories such as 0VF00F000 may then occur where the meaning of zeroes becomes ambiguous. A zero can either mean a dead or a dormant plant. Various ad hoc methods in wide use among plant ecologists have made strong assumptions about when a zero should be equated to a dormant individual. These methods have never been compared among each other. In our talk and in Kéry et al. (submitted), we show that these ad hoc estimators provide spurious estimates of survival and should not be used. In contrast, if detection probabilities for aboveground plants are known or can be estimated, capturerecapture (CR) models can be used to estimate probabilities of survival and state–transitions and the fraction of the population that is dormant. We have used this approach in two studies of terrestrial orchids, Cleistes bifaria (Kéry et al., submitted) and Cypripedium reginae (Kéry & Gregg, submitted) in West Virginia, U.S.A. For Cleistes, our data comprised one population with a total of 620 marked ramets over 10 years, and for Cypripedium , two populations with 98 and 258 marked ramets over 11 years. We chose the ramet (= single stem or shoot) as the demographic unit of our study since there was no way distinguishing among genets (genet = genetical individual, i.e., the “individual” that animal ecologists are mostly concerned with). This will introduce some non–independence into the data, which can nevertheless be dealt with easily by correcting variances for overdispersion. Using ramets instead of genets has the further advantage that individuals can be assigned to a state such as flowering or vegetative in an unambiguous manner. This is not possible when genets are the demographic units. In all three populations, auxiliary data was available to show that detection probability of aboveground plants was m 0.995 We fitted multistate models in program MARK by specifying three states (D, V, F), even though the dormant state D does not occur in the encounter histories. Detection probability is fixed at 1 for the vegetative (V) and the flowering state (F) and at zero for the dormant state (D). Rates of survival and of state transitions as well as slopes of covariate relationships can be estimated and LRT or the AIC machinery be used to select among models. To estimate the fraction of the population in the unobservable dormant state, the encounter histories are collapsed to 0 (plant not observed aboveground) and 1 (plant observed aboveground). The Cormack–Jolly–Seber model without constraints on detection probability is used to estimate detection probability, the complement of which is the estimated fraction of the population in the dormant state. Parameter identifiability is an important issue in multi state models. We used the Catchpole–Morgan–Freeman approach to determine which parameters are estimable in principle in our multi state models. Most of 15 tested models were indeed estimable with the notable exception of the most general model, which has fully interactive state- and time-dependent survival and state transition rates. This model would become identifiable if at least some plants would be excavated in years when they do not show up aboveground. Our analyses for three analyzed populations of Cleistes and Cypripedium yielded annual ramet survival rates ranging from 0.86–0.96. Estimates of the average fraction dormant ranged from 0.02–0.30, but with up to half a population in the dormant state in some years. Ultrastructural modeling enables interesting hypotheses to be tested about the relationships of demographic rates with climatic covariates for instance. Such covariate modeling makes the CR approach particularly interesting for evolutionary–ecological questions about, e.g., the adaptive significance of the dormant state.

Animal Biodiversity and Conservation↗

USGS2019

Using environmental DNA (eDNA) to assess the presence of cavefish and cave crayfish populations in caves of the Ozark Highlands

Many cavefishes and cave crayfishes are considered of conservation concern; however, sampling these species is inherently difficult given their occupied environments. The goal of our project was to verify the presence of select karst organisms while developing the foundation for sampling approaches that might be useful to conservation and management agencies. Our project objectives were to develop assays to amplify deoxyribonucleic acid (DNA) from several species of Ozark cavefishes and cave crayfishes and complete an initial surveillance of locations across the Ozark Highlands using environmental DNA (eDNA). Using DNA either provided by agency cooperators or that we extracted from tissue samples, we PCR amplified and then sequenced the Cytochrome Oxidase 1 (CO1) gene for cave crayfishes and the NADH Dehydrogenase Subunit 2 (ND2) gene for cavefishes. We developed species-specific primers and probes for five cave crayfishes and two cavefishes. From February 2017 to May 2017, we sampled 1–5 sampling units from 42 caves, wells, and springs (i.e., sites) using eDNA and traditional visual surveys. We measured physicochemical parameters at each sampling unit to estimate detection probability associated with both techniques. We also calculated two occupancy covariates for each site using geospatial data. We successfully amplified Troglichthys rosae DNA from the environment and detected DNA representing this species at 24 of 40 sites. At 16 of the sites where we detected T. rosae DNA, we did not visually observe the species. Although our assay for Typlichthys eigenmanni successfully amplified the target DNA from the environment, it also resulted in false absences where the species was visually confirmed. Using eDNA to detect cave crayfishes was much more difficult. The assay for Cambarus subterraneus did not work for eDNA samples and we were unable to pick up DNA from the environment, even at locations where it was visually confirmed. Alternatively, the eDNA surveys worked well for C. tartarus and we were able to amplify DNA at every site where it was visually observed. Our assay for C. aculabrum was based on a single sample obtained from GenBank, and did not amplify eDNA from field samples. Lastly, our eDNA results from samples in the known range of Orconectes stygocaneyi suggested the species may be found at an additional cave. Detection using eDNA based on our O. stygocaneyi assay was likely low because it was designed from a pseudogene; however, positive eDNA samples were sequenced to confirm species-specific DNA. Detection probability of both cavefishes and cave crayfishes varied by survey technique and was influenced by water volume, water clarity, water velocity, and substrate. Detection of cavefishes and cave crayfishes via visual surveys decreased when water volume increased, whereas detection using eDNA increased with greater water volume. Detection between taxa using either sample method was highest in habitats classified by fine substrates, except for eDNA detection of crayfishes which was greatest in coarse substrates. Detection of cavefishes increased with water clarity, but detection of cave crayfishes increased with turbidity. Detection probability of both cavefishes and crayfishes using eDNA increased slightly with water velocity, but decreased with visual surveys as water velocity increased. Occupancy by both taxa was positively related to particular geologic series. Crayfish occupancy was negatively related to fine-scale anthropogenic disturbance (i.e., 500-m buffer around the site), whereas crayfish showed no relationship with disturbance. Our results suggest possible range extensions, provide insights to factors driving detection using both sample techniques, and suggest areas where recharge zones may be shared among caves. Future efforts focused on a comprehensive evaluation of genetic diversity among cave crayfishes to improve assay design could improve detection and the applicability of eDNA as a supplemental and non-invasive sampling approach.

Cooperator Science Series↗

USGS2021

Connectivity of Mojave Desert tortoise populations—Management implications for maintaining a viable recovery network

Executive Summary The historic distribution of Mojave desert tortoises ( Gopherus agassizii ) was relatively continuous across the range, and the importance of tortoise habitat outside of designated tortoise conservation areas (TCAs) to recovery has long been recognized for its contributions to supporting gene flow between TCAs and to minimizing impacts and edge effects within TCAs. However, connectivity of Mojave desert tortoise populations has become a concern because of recent and proposed development of large tracts of desert tortoise habitat that cross, fragment, and surround designated conservation areas. This paper summarizes the underlying concepts and importance of connectivity for Mojave desert tortoise populations by reviewing current information on connectivity and providing information to managers for maintaining or enhancing desert tortoise population connectivity as they consider future proposals for development and management actions. Maintaining an ecological network for the Mojave desert tortoise, with a system of core habitats (TCAs) connected by linkages, is necessary to support demographically viable populations and long-term gene flow within and between TCAs. There are four points for wildlife and land-management agencies to consider when making decisions that could affect connectivity of Mojave desert tortoise populations (for example, in updating actions in resource management plans or amendments that could help maintain or restore functional connectivity in light of the latest information): Management of all desert tortoise habitat for persistence and connectivity . Desert tortoise populations continue to decline within most TCAs, and it is unlikely that trends are better in populations outside protected areas. Fragmentation exacerbates negative population trends by breaking large continuous populations into smaller isolated populations. Connectivity within large populations can enhance resilience to localized disturbances due to rescue by neighboring individuals. In contrast, smaller fragmented populations are resistant to rescue by their isolation and thus could suffer irreversible declines to extirpation from a variety of threats and stochastic events. Enhanced threat reduction to reverse declines within TCAs and to maintain occupied habitat in the surrounding matrix would help reduce the variability in population growth rates and improve the resilience of protected populations even while implementing efforts to improve connectivity. Each TCA has unique strengths and weaknesses regarding its ability to support minimum sustainable populations based on areal extent and its ability to support population increases based on landscape connection with adjacent populations. Considering how proposed projects (inside or outside of TCAs) affect connectivity and the ability of TCAs to support at least 5,000 adult tortoises (the numerical goal for each TCA) could help managers to maintain the resilience of TCAs to population declines. The same project, in an alternative location, could have very different impacts on local and regional populations. For example, within the habitat matrix surrounding TCAs, narrowly delineated corridors may not allow for natural population dynamics if they do not accommodate overlapping home ranges along most of their widths so that tortoises reside, grow, find mates, and produce offspring that can replace older tortoises. In addition, most habitat outside TCAs may receive more surface disturbance than habitat within TCAs. Therefore, managing the entire remaining matrix of desert tortoise habitat for permeability may be better than delineating fixed corridors. These concepts apply, especially given uncertainty about long-term condition of habitat, within and outside of TCAs under a changing climate. Ultimately, questions such as “ What are the critical linkages that need to be protected ?” could be better framed as “ How can we manage the remaining habitat matrix in ways that sustain ecological processes and habitat suitability for special status species ?” Land-management decisions made in the context of the latter question may be more conducive to maintenance of a functional ecological network. Limitations on landscape-level disturbance across habitat managed for the desert tortoise Clearly delineating habitat linkages and differentiating them from non-delineated areas by the uses that are permitted or prohibited within them by specific management guidelines can help achieve functional connectivity. Such guidelines would be most effective if they considered and accounted for all surface disturbances (for example, temporary disturbances such as fiberoptic lines or off-highway vehicle routes, right-of-ways, utility-scale solar development, urbanization) to the extent possible. A weighted framework that varies with the permanence or severity of the disturbance, and can be additive to quantify cumulative effects, could be useful (Xiong, 2020). For example, minor roads can alter tortoise movements independently of other features (Peaden and others, 2017; Hromada and others, 2020), but if the isolated dirt road is accompanied by a powerline that encourages raven predation (Xiong, 2020), then the two features together may be additive. Ignoring minor or temporary disturbance on the landscape could result in a cumulatively large impact that is not explicitly acknowledged (Goble, 2009); therefore, understanding and quantifying all surface disturbance on a given landscape is prudent. In California, the Bureau of Land Management established 0.1–1.0 percent caps on new surface-disturbance for TCAs and mapped linkages that address the issues described in number 1 of this list. Nevada, Utah, and Arizona currently do not have surface-disturbance limits. Limits comparable to those in the Desert Renewable Energy Conservation Plan (DRECP) would be 0.5 percent within TCAs and 1 percent within the linkages modeled by Averill-Murray and others (2013). Limits in some areas of California within the Desert Renewable Energy Conservation Plan, such as Ivanpah Valley, are more restrictive, at 0.1 percent. Continuity across the state line in Nevada could be achieved with comparable limits in the adjacent portion of Ivanpah Valley, as well as the Greater Trout Canyon Translocation Area and the Stump Springs Regional Augmentation Site. These more restrictive limits would help protect remaining habitat in the major interstate connectivity pathway through Ivanpah Valley and focal areas of population augmentation that provide additional population connectivity along the western flank of the Spring Mountains. In a recent study that analyzed 13 years of desert tortoise monitoring data, nearly all desert tortoise observations were at sites in which 5 percent or less of the surrounding landscape within 1 kilometer was disturbed (Carter and others, 2020a). To help maintain tortoise habitability and permeability across all other non-conservation-designated tortoise habitat, all surface disturbance could be limited to less than 5-percent development per square kilometer because the 5-percent threshold for development is the point at which tortoise occupation drops precipitously (Carter and others, 2020a). However, although individual desert tortoises were observed at development levels up to 5 percent, we do not know the fitness or reproductive characteristics of these individuals. This level of development also may not allow for long-term persistence of healthy populations that are of adequate size needed for demographic or functional connectivity; therefore, a conservative interpretation suggests that, ideally, development could be lower. Lower development levels would be particularly useful in areas within the upper 5th percentile of connectivity values modeled by Gray and others (2019). Reducing ancillary threats in places where connectivity is restricted to narrow strips of habitat, for example, narrow mountain passes or vegetated strips between solar development, could enhance the functionality of these vulnerable linkages. In such areas, maintaining multiple, redundant linkages could further enhance overall connectivity. Minimization of mortality from roads and maximization of passage under roads . Roads pose a significant threat to the long-term persistence of local tortoise populations, and roads of high traffic volume lead to severe population declines, which ultimately fragments populations farther away from the roads. Three points (a.–c.) pertain to reducing direct mortality of tortoises on the many paved roads that cross desert tortoise habitat and to maintaining a minimal level of permeability across these roads: Tortoise-exclusion fencing tied into culverts, underpasses, overpasses, or other passages below roads in desert tortoise habitat, would limit vehicular mortality of tortoises and provide opportunities for movement across the roads. Installation of shade structures on the habitat side of fences installed in areas with narrow population-depletion zones would limit overheating of tortoises that may pace the fence. Passages below highways could be maintained or retrofitted to ensure safe tortoise access, for example, by filling eroded drop-offs or modifying erosion-control features such as rip-rap to make them safer and more passable for tortoises. Wildlife management agencies could work with transportation departments to develop construction standards that are consistent with hydrologic/erosion management goals, while also incorporating a design and materials consistent with tortoise survival and passage and make the standards widely available. The process would be most effective if the status of passages was regularly monitored and built into management plans. Healthy tortoise populations along fenced highways could be supported by ensuring that land inside tortoise-exclusion fences is not so degraded that it leads to degradation of tortoise habitat outside the exclusion areas. For example, severe invasive plant infestations inside a highway exclusion could cause an increase of invasive plants outside the exclusion area and degrade habitat; therefore, invasive plants inside road rights of way could be mown or treated with herbicide to limit their spread into adjacent tortoise habitat and minimize the risk of these plants carrying wildfires into adjacent habitat. Adaptation of management based on new information . Future research will continue to build upon and refine models related to desert tortoise population connectivity and develop new ones. New models could consider landscape levels of development and be constructed such that they share common foundations to support future synthesis efforts. If model development was undertaken in partnership with entities that are responsible for management of desert tortoise habitat, it would facilitate incorporation of current and future modeling results into their land management decisions. There are specific topics that may be clarified with further evaluation: The effects of climate change on desert tortoise habitat, distribution, and population connectivity; The effects of large-scale fires, especially within repeatedly burned habitat, on desert tortoise distribution and population connectivity; The ability of solar energy facilities or similar developments to support tortoise movement and presence by leaving washes intact; leaving native vegetation intact whenever possible, or if not possible, mowing the site, allowing vegetation to re-sprout, and managing weeds; and allowing tortoises to occupy the sites; and The design and frequency of underpasses necessary to maintain functional demographic and genetic connectivity across linear features, like highways.

Arizona, California, Nevada↗

USGS2012

Short-term impacts of a 4-lane highway on black bears in eastern North Carolina

Among numerous anthropogenic impacts on terrestrial landscapes, expanding transportation networks represent one of the primary challenges to wildlife conservation worldwide. Larger mammals may be particularly vulnerable because of typically low densities, low reproductive rates, and extensive movements. Although numerous studies have been conducted to document impacts of road networks on wildlife, inference has been limited because of experimental design limitations. During the last decade, the North Carolina Department of Transportation (NCDOT) rerouted and upgraded sections of United States Highway 64 between Raleigh and the Outer Banks to a 4-lane, divided highway. A new route was selected for a 24.1-km section in Washington County. The new section of highway included 3 wildlife underpasses with adjacent wildlife fencing to mitigate the effects of the highway on wildlife, particularly American black bears (Ursus americanus). We assessed the short-term impacts of the new highway on spatial ecology, population size, survival, occupancy, and gene flow of black bears. We tested our research hypotheses using a before-after control-impact (BACI) study design. We collected data during 2000–2001 (preconstruction phase) and 2006–2007 (postconstruction phase) in the highway project area and a nearby control area (each approx. 11,000 ha), resulting in 4 groups of data (i.e., pre- or postconstruction study phase, treatment or control area). We captured and radiocollared 57 bears and collected 5,775 hourly locations and 4,998 daily locations. Using mixed-model analysis of variance and logistic regression, we detected no differences in home ranges, movement characteristics, proximity to the highway alignment, or habitat use between the 2 study phases, although minimum detectable effect sizes were large for several tests. However, after completion of the new highway, bears on the treatment area became less inactive in morning, when highway traffic was low, compared with bears on the control area (F 1, 43 = 6.05, P = 0.018). We used DNA from hair samples to determine if population size and site occupancy decreased following highway construction. For each study phase, we collected black bear hair from 70 hair snares on each study area during 7 weekly sampling periods and generated genotypes using 10 microsatellite loci. We used the multilocus genotypes to obtain capture histories for 226 different bears and used capture-mark-recapture models to estimate population size. Model-averaged estimates of population size decreased on the treatment area from 87.7 bears before construction to 31.6 bears after construction (64% reduction) and on the control area from 163.6 bears to 108.2 bears (34% reduction). Permutation procedures indicated this reduction was proportionally greater for the treatment area (P = 0.086). We also applied a spatially explicit capture-recapture technique to test our research hypothesis. The model with the most support indicated a greater change in density on the treatment area (69% reduction) compared with the control area (24% reduction). We did not observe a treatment effect based on survival of radiocollared bears. We used bear visits to hair snares as detections in multi-season occupancy models and found that occupancy decreased more on the treatment area (preconstruction: Ψ = 0.84; postconstruction: Ψ = 0.44; 48% decline) than the control area (preconstruction: Ψ = 0.91; postconstruction: Ψ = 0.81; 11% decline), primarily as a function of a greater probability of site extinctions (ε) on the treatment area (ε = 0.57) than the control area (ε = 0.17). Finally, individual- and population-based analyses of contemporary gene flow did not indicate the highway was a barrier to movements. Black bear use of the 3 wildlife underpasses was infrequent (17 verified crossings based on remote cameras, track surveys, and telemetry). Only 4 of 8 bears with home ranges near the highway were documented crossing the highway (n = 36 crossings), of which 2 were killed in vehicle collisions. Six additional bears were killed in vehicle collisions from May 2007 to November 2008, after we completed field work. Harvest data indicated that hunting mortality alone could explain the population decline on the control area. On the treatment area, however, hunting mortality only accounted for an approximately 40% population decline; the additional 30% decline we observed likely was caused by other mortality. We speculate vehicle collisions were primarily responsible. We conclude that impacts of the new highway on resident black bears occurred at the population level, rather than the individual or genetic level, but that the impact was smaller than harvest mortality. Increased activity by remaining bears when traffic volumes were low indicated behavioral plasticity. Bear use of the underpasses seemed sufficient to maintain gene flow between areas north and south of the new highway. Effectiveness of wildlife underpasses to reduce mortality of black bears may be enhanced if mitigation includes continuous fencing between crossing structures. For small, isolated populations of threatened or endangered large mammals, the potential demographic impacts of highways are an essential consideration in the transportation planning process. Control of mortality factors and maintaining demographic connectivity are particularly important.

California↗

USGS2020

Population and habitat analyses for greater sage-grouse (Centrocercus urophasianus) in the bi-state distinct population segment—2018 update

Executive Summary The Bi-State Distinct Population Segment (Bi-State DPS) of greater sage-grouse ( Centrocercus urophasianus , hereinafter “sage-grouse”) represents a genetically distinct and geographically isolated population that straddles the border between Nevada and California. The primary threat to these sage-grouse populations is the expansion of single-leaf pinyon ( Pinus monophylla ) and Utah juniper ( Juniperus osteosperma ) into sagebrush ecosystems, which fragments and reduces population connectivity and survival. Other important threats include low water availability during brood-rearing, particularly during drought, and increased predation by common ravens ( Corvus corax ), a generalist predator often associated with anthropogenic resource subsidies. Although the Bi-State DPS occurs at high elevations relative to sage-grouse range-wide, changes in historical wildfire cycles and the conversion of native shrubs to invasive annual grasslands still threaten these populations. The Bi-State DPS has undergone multiple federal status assessments and associated litigation. For example, in October of 2013, the Bi-State DPS was proposed for listing as threatened under the Endangered Species Act of 1973 by the U.S. Fish and Wildlife Service (USFWS), then withdrawn in April 2015. The withdrawal decision was challenged, and in May 2018, a Federal district court ordered the withdrawal decision to be vacated, and USFWS was required to re-open the October 2013 listing evaluation. In response, the U.S. Geological Survey (USGS), with State and Federal collaborators, embarked on a multipronged analysis to provide current and best available science regarding population status of sage-grouse within the Bi-State DPS. Using data from a long-term monitoring program, we carried out four analytical study objectives, and here, we provide preliminary results of these analyses. First, we used integrated population modeling (IPM) to predict annual population abundance and annual finite rate of population change for the Bi-State DPS, as a whole, and for each subpopulation between 1995 and 2018. Because sage-grouse exhibit population cycles (periodic increases and decreases in abundance across approximately 6- to 10-year wavelengths), we estimated trends across three nested temporal scales that represent one (11 years), two (18 years), and three (24 years) complete population cycles. These estimates of relatively long-term averaged population change account for temporal (that is, interannual) variation. Our model predicted population abundance for the Bi-State DPS during 2018 at 3,305 individuals (2,247–4,683), with the majority occupying Bodie Hills and Long Valley. The model also predicted cyclic dynamics in abundance through time with evidence of 24-year population growth and slight trends of decline over the past 18 years. Specifically, across the Bi-State DPS as a whole, we estimated annual average at 0.99, 0.99, and 1.02 over the one, two, and three population cycles, which equated to a 10.5 percent, 16.6 percent decrease, and 60.0 percent increase in abundance over the 11-, 18-, and 24-year cycles. Estimated abundance in 2018 had not reached numbers lower than those predicted during 1995. However, we found spatial variation in population trends across the three cycles. Bodie Hills subpopulation comprised the greatest (1,521) and exhibited average annual greater than 1.0 across all periods resulting in average annual increases of 7 percent. This relatively large subpopulation has grown 5 times larger than what was predicted in 1995 while experiencing cyclical dynamics within that period. Conversely, other smaller subpopulations within the Bi-State DPS exhibited average annual equal to or less than 1.0 resulting in estimated 10-year risks of extirpation ranging from 2.0 to 76.1 percent. In general, evidence of decline among smaller subpopulations was greatest for the most recent period (2008–18) compared to a period that encompassed three full population cycles (24-year). This difference coincides with an intense period of drought that began in 2012. For comparative purposes as part of this first objective, we conducted a similar analysis for populations of sage-grouse within Nevada and California but outside the Bi-State DPS. We developed a region-wide and distance-weighted IPM using lek count from Nevada Department of Wildlife (NDOW) and California Department of Fish and Wildlife (CDFW) databases and with telemetry data collected by USGS across 12 sage-grouse subpopulations. Our models predicted similar patterns in population cycling outside the Bi-State DPS but with much stronger evidence of long-term declines across 24 years. Specifically, median averaged across each year of the 11-, 18-, and 24-year periods resulted in average annual values of 0.94, 0.97, and 0.99, respectively. These values equate to 41.0 percent, 38.5 percent, and 21.3 percent declines over the corresponding periods. Second, we used lek count data in a state-space modeling framework to compare trends in population abundance across different spatial scales (that is, leks versus Bi-State DPS). This hierarchical framework allowed us to disentangle declines associated with climate conditions as opposed to other local level factors that might signal the need for management intervention. Specifically, we identified 7 leks that were both declining and recently decoupled from larger spatial scale trends, typically governed by climatic conditions (referred to as soft or hard signals). The goal of this analysis was to provide an early warning system that might have implications for conservation actions at local scales. Third, we developed phenological (spring, summer–fall, and winter) and reproductive life stage (nesting, early brood-rearing, and late-brood rearing) based resource selection functions using various environmental covariates. We report rankings of variable importance for each season and life stage, developed maps of habitat selection indices (HSI), binned categories representing low, moderate, and high classes of quality (where any category greater than or equal to low indicated selected habitat) for each phenological season and life stage, and produced composite maps by selected phenological and reproductive stage to estimate annual habitat. Fourth, we used for each lek within the Bi-State DPS to carry out a spatial analysis that quantified substantial changes in the distribution of occupied habitat across long- (24-year) and short- (11-year) term periods. Owing to differences among available datasets, the long-term analysis primarily reflected spatial shifts among subpopulations comprising the majority of the Bi-State DPS (that is, Bodie Hills and Long Valley) while the short-term analysis also quantified changes among subpopulations along the periphery. Over long and short-term periods, the overall distribution of occupied habitat (as measured by 99 percent utilization distributions intersecting any quantified habitat) was reduced by 20,573 ha and 55,492 ha, respectively. Occupied core areas (as measured by 50 percent utilization distributions intersecting any quantified habitat) over long-term periods were solely located in Bodie Hills and Long Valley. Although nearly all subpopulations experienced contractions in occupied overall and core distribution, Bodie Hills experienced spatial expansion that occurred with concomitant spatial contraction at Long Valley over both periods. Subpopulations at the northern (Pine Nuts), central (Sagehen) and southern (White-Mountains) extents of the Bi-State DPS also experienced spatial contraction over the short-term period. These findings, coupled with those of population trends, indicate long-term patterns in redistribution of sage-grouse from Long Valley and peripheral subpopulations to Bodie Hills. That is, sage-grouse subpopulations at the periphery are declining while the largest population at the core is increasing, which could have meaningful impacts on overall metapopulation persistence. We provide evidence for loss of occupied habitat (reduced distribution) given local extirpation of subpopulations. Fifth, we calculated percentages of selected phenological, life stage, and annual habitat that each subpopulation contributed to the Bi-State DPS. We then intersected these maps with a composite estimate of occupied habitat from the fourth objective and calculated percentages of selected habitat likely occupied by sage-grouse that each subpopulation contributed to the Bi-State DPS. These values provide evidence for loss of occupied habitat and subsequent reductions in spatial distribution given reductions in abundance and, in some cases, extirpation of leks within subpopulations. Lastly, we carried out an initial in-depth analysis of selection for irrigated pastures and wet meadows during the brood-rearing stage for the Long Valley subpopulation. We chose this subpopulation because it represents a population core, representing 26.5 percent of total sage-grouse within the Bi-State DPS, and has exhibited long-term declines in abundance and distribution. This subpopulation is highly sensitive to precipitation and other factors that influence water availability. Models predicted higher use of the interior portions of irrigated pastures and wet meadows during late brood-rearing period, which represented a potentially risky use of habitat that was exacerbated during periods of low moisture (for example, drought, reduced water delivery, or both). Sage-grouse typically used edges of riparian areas and pastures, largely because the interior of these mesic areas consisted of considerably less overhead concealment cover (for example, shrubs) that likely resulted in a higher risk of mortality. We found that a lack of water delivery to pastures in the form of overwinter precipitation or diversion ditches increased the movements of sage-grouse to the interior of pastures. Although further investigation of water delivery impacts on chick survival are warrented, our initial findings regarding resource selection may explain recent declines in population growth at Long Valley.

California, Nevada↗