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USGS2024

Incorporating projected climate conditions to map future riparian refugia

Identifying areas expected to remain buffered from climate change and maintain biodiversity and ecological function (i.e., climate refugia) is important for climate adaptation planning. As structurally diverse transitional zones between terrestrial and aquatic environments, riparian areas are often biological hotspots and provide critical corridors for species movement, particularly in arid and semi-arid regions. In our study region in the western and central USA, identifying riparian areas that could serve as climate refugia is a priority for wildlife managers. We mapped areas with connected riparian habitats that, based on landscape diversity and projected changes in summer temperatures and landscape runoff, are expected to serve as climate refugia. To incorporate uncertainty and balance the need for near- and long-term planning, we mapped potential refugia for 2 future time periods (2040–2069, 2070–2099) based on 2 climate models that represented divergent but plausible climate outcomes. The approach we developed is not constrained by physiology or behavior of target species and can be used to identify areas expected to fare comparatively well under a wide range of future climate scenarios. Our approach can also be used to identify areas where restoration could increase riparian connectedness and climate resilience.

Colorado, Indiana, Kansas, Montana, North Dakota, ↗

USGS2017

Importance of scale, land cover, and weather on the abundance of bird species in a managed forest

Climate change and habitat loss are projected to be the two greatest drivers of biodiversity loss over the coming century. While public lands have the potential to increase regional resilience of bird populations to these threats, long-term data are necessary to document species responses to changes in climate and habitat to better understand population vulnerabilities. We used generalized linear mixed models to determine the importance of stand-level characteristics, multi-scale land cover, and annual weather factors to the abundance of 61 bird species over a 20-year time frame in Chippewa National Forest, Minnesota, USA. Of the 61 species modeled, we were able to build final models with R-squared values that ranged from 26% to 69% for 37 species; the remaining 24 species models had issues with convergence or low explanatory power (R-squared < 20%). Models for the 37 species show that stand-level characteristics, land cover factors, and annual weather effects on species abundance were species-specific and varied within guilds. Forty-one percent of the final species models included stand-level characteristics, 92% included land cover variables at the 200 m scale, 51% included land cover variables at the 500 m scale, 46% included land cover variables at the 1000 m scale, and 38% included weather variables in best models. Three species models (8%) included significant weather and land cover interaction terms. Overall, models indicated that aboveground tree biomass and land cover variables drove changes in the majority of species. Of those species models including weather variables, more included annual variation in precipitation or drought than temperature. Annual weather variability was significantly more likely to impact abundance of species associated with deciduous forests and bird species that are considered climate sensitive. The long-term data and models we developed are particularly suited to informing science-based adaptive forest management plans that incorporate climate sensitivity, aim to conserve large areas of forest habitat, and maintain an historical mosaic of cover types for conserving a diverse and abundant avian assemblage.

Minnesota↗

USGS2021

The influence of floral resources and microclimate on pollinator visitation in an agro-ecosystem

As agriculture expands to meet the needs of a growing global population, natural ecosystems are threatened by deforestation and habitat fragmentation. Tropical agroforestry systems offer a sustainable alternative to traditional agriculture by providing food for production while also supporting biodiversity and ecosystem services. Previous studies have shown that these systems may even improve crop pollination, but the mechanisms of how these improvements occur are still poorly understood. Using coffee as a focal crop, we explored how microclimatic conditions affected nectar traits (sugar and caffeine concentration) important for pollinator visitation. We also studied how microclimate, floral traits, floral availability at the coffee plant level, availability of floral resources provided by other plant species in the agroecosystem (neighborhood floral availability), and the presence of other bees affected the amount of time bees spent foraging on coffee flowers and the proportion of coffee pollen carried on their bodies. We explored these factors using the two dominant coffee species farmed on Puerto Rico, Coffea canephora and C. arabica , under sun and shade management. We found that high nectar sugar concentration and temperature were important predictors of short floral visits (<15 seconds), while increased number of bees and open coffee flowers were important predictors of longer floral visits (16-180 seconds). High nectar caffeine concentration was an important predictor of longer visits on C. arabica flowers while the opposite was observed for C. canephora flowers. For both species, high coffee floral availability was the main predicting factor for the proportion of coffee pollen on the bees bodies. Surprisingly, neither neighborhood floral availability nor the type of coffee plantation (agroforest/shade or sun) were important predictors of bee visitation. These results suggest non-coffee flowering plants in coffee plantations were neither competitors nor facilitators of coffee plantes for pollinators. Additionally, most of the bees surveyed were carrying 80% pollen from one species ( C. arabica or C. canephora ), likely resulting in little heterospecific pollen deposition between Coffea and non-Coffea flowers. Shade trees in coffee plantations do not detract from pollinator visitation to coffee flowers, suggesting that the provision of multiple ecological and wildlife conservation benefits by shade trees is not in conflict with a growers ability to maximize the benefits of insect pollination on fruit production.

Adjuntas Lares,Las Marias, Maricao, Puerto Rico Ut↗

USGS2025

Fine-scale spatial risk models to predict avian collisions with power lines

1. Avian fatalities caused by collisions with overhead power lines are an important conservation issue worldwide. Although mitigation strategies can help reduce mortalities, given their considerable cost and the vast scale of power line infrastructure, cost-effective action requires that these efforts be prioritised to areas with the highest potential risk to birds. To date, this risk assessment has usually been guided by potentially biased information on the location of recorded fatalities. 2. Here we use five years of GPS tracking data from endangered Tasmanian wedge-tailed eagles to develop an alternative approach to risk assessment: fine-scale spatial risk models based on behavioural analyses. We built and cross-validated a model that generates spatially explicit predictions of the probability that eagles would cross power lines at hazardous altitudes throughout the entire Tasmanian electricity distribution network. 3. In our model, probability of power line crossings was most strongly associated with the proportion of forest edges, wet forest, open habitat, freshwater sources, and rural residential developments in the area surrounding the power lines. Cross-validation indicated that the model effectively predicted where Tasmanian wedge-tailed eagles cross power lines at low altitude. 4. Model validation suggested our approach was a powerful predictor of the locations of power line collisions involving eagles. The locations of almost all (94%) confirmed eagle fatalities were in the half of the total Tasmanian power line area assigned the higher risk by the model, and 50% of incidents occurred in the 30% of the power line area estimated to be highest risk. 5. Synthesis and applications . Our study illustrates a framework for using bird movement data to provide insights into avian behaviour and the risk they encounter around power line infrastructure. Electricity delivery industries can use these models to identify the electrical infrastructure that poses the highest risk to avian survival and prioritise mitigation efforts, thereby optimizing the benefit of investments to reduce detrimental effects on biodiversity. Our model can direct pre-emptive mitigation across Tasmania’s 20,310 km of distribution infrastructure to meet management targets aiming to reduce the negative effects of power lines on the Tasmanian wedge-tailed eagle.

Tasmania↗

USGS2023

Groundwater discharge by evapotranspiration from the Amargosa Wild and Scenic River and contributing areas, Inyo and San Bernardino Counties, California

The Amargosa Wild and Scenic River, located in the southwestern Mojave Desert in Inyo and San Bernardino Counties, California, is a Federally protected waterway that supports the biodiversity of the region. Water in the river primarily comes from interbasin groundwater flow that originates as precipitation in the Spring Mountains. The precipitation enters the regional groundwater system and flows westerly beneath Pahrump, Chicago, and California Valleys before discharging into the Amargosa Wild and Scenic River system. In Pahrump Valley, groundwater discharge occurs as evapotranspiration (ET), spring discharge, and groundwater pumping, and in Chicago and California Valleys, groundwater discharge occurs as ET and spring discharge. Remaining groundwater flows into the Amargosa Wild and Scenic River and its main tributary, the China Ranch Wash, or is discharged from regional springs downgradient from Chicago and California Valleys. The Amargosa Wild and Scenic River and the China Ranch Wash sustain areas of deep-rooted vegetation (phreatophytes) that consume regional groundwater. Discharge from regional springs in the area only flows on the land surface for short distances before seeping back into the ground where the water generally is consumed by evaporation from moist soil or by transpiration of plants. Intermittent Amargosa River flow out of the study area is the only other form of discharge. In arid regions such as the Mojave Desert, groundwater discharge by evapotranspiration (ET g ) often is the only significant form of discharge in a regional water budget, and therefore, an estimate of annual ET g is a good approximation of the total annual groundwater discharge. In this study area, however, total annual discharge is annual ET g plus the annual surface-water discharge of the Amargosa River that exits the study area. Therefore, the annual ET g from Chicago and California Valleys and along the Amargosa Wild and Scenic River and the China Ranch Wash, plus the discharge of the Amargosa River, is a good approximation of the total annual groundwater discharge required to sustain the riparian habitats and surface-water flow in the Amargosa Wild and Scenic River. The Amargosa Conservancy and Inyo County, Calif., are interested in quantifying the total annual groundwater discharge required to sustain the riparian habitats and surface-water flow in the Amargosa Wild and Scenic River and entered into a cooperative agreement with the U.S. Geological Survey to estimate ET g from the Amargosa Wild and Scenic River study area. The study area consists of open-water bodies, areas with perennially moist soil, and areas with phreatophytes, all of which are discharging regional groundwater in Chicago and California Valleys, along the Amargosa Wild and Scenic River, and in the China Ranch Wash. Annual ET g for the Amargosa Wild and Scenic River study area is estimated to be 10,139,000 cubic meters. The estimate was determined by delineating boundaries of open water, perennially moist soil, and phreatophytes, multiplying the areas by appropriate site-scale ET g to derive annual ET g for each ET unit, and then adding the annual ET g for all ET units in the GDAs and study area. Boundaries of discharge areas were visually delineated using high-resolution aerial imagery and refined by field verification. Open water and moist soil ET g were estimated in previous investigations, and phreatophyte ETg was estimated from a quadratic relation between site-scale ET g and a vegetation index of the study area. The quadratic relation was derived from four points. Two points were based on the site-scale ET g estimated for this study and two points corresponded to theoretical minimum and maximum points. Site-scale ET g was measured at two ET-monitoring sites using the eddy-covariance method. At one site, located in sparse shrubs, ET g was 0.121 meters per year, and at the other site, located in dense wetland vegetation, ET g was 1.056 meters per year. A scaled normalized difference vegetation index (NDVI) that encompasses the study area was created from 0.6-meter resolution multispectral (4-band) aerial imagery from 2020 and was used as an indicator of plant density or cover.

California↗

USGS2025

Elk personality and anthropogenic food subsidy: Managing conflict and migration loss

The continued decline of long-distance ungulate migrations threatens to decouple important ecological processes that increase biodiversity and wildlife abundance. Past research has focused on preserving migration paths where habitat fragmentation and loss disrupt movement corridors. However, shifting residency-migration trade-offs are the stronger driver of migration loss in some populations. Suburban residential developments may provide ungulates with anthropogenic food sources and refuge from predators, which can increase population growth among short-distance migrants relative to long-distance migrants. This trend can increase wildlife vehicle collisions and other human–wildlife conflicts while simultaneously reducing hunting opportunities. Yet, individual animals vary in their tolerance of human disturbance. We investigated how interindividual variation relative to conflict and human habituation influences elk migration and space use on shared winter range. We used a clustering algorithm applied to GPS collar data to identify elk use of anthropogenic food resources in suburban habitat. Cluster locations identified all known anthropogenic subsidy locations during the study period. Elk that used suburban anthropogenic food sources also migrated 60% shorter distances between summer and winter ranges than elk with no known use of these food subsidies. Elk use of protected wintering grounds was spatially structured such that conflict-prone, short-distance migrants disproportionately used areas with more human activity. Clustering algorithms applied to GPS collar data may allow managers to identify foci of concentrated use that generates human–wildlife conflict, and where prion deposition and environmental contamination facilitate the spread of chronic wasting disease, particularly in suburban areas with anthropogenic food subsidies. The apparent spatial structuring of shared winter range according to the conflict potential and migration strategy of individual elk may also permit managers to assess relative recruitment among cryptic population segments using different migration strategies and facilitate targeted, adaptive management actions. These associations between conflict, human habituation, and migration shed light on the urbanization of wildlife species, inform efforts to manage human–wildlife conflict and disease spread, and emphasize that a multipronged approach beyond maintaining habitat corridors may be necessary to conserve long-distance migrations for species that can become human-habituated.

Wyoming↗

USGS2012

Ecological impacts of non-native species

Non-native species are considered one of the greatest threats to freshwater biodiversity worldwide (Drake et al. 1989; Allen and Flecker 1993; Dudgeon et al. 2005). Some of the first hypotheses proposed to explain global patterns of amphibian declines included the effects of non-native species (Barinaga 1990; Blaustein and Wake 1990; Wake and Morowitz 1991). Evidence for the impact of non-native species on amphibians stems (1) from correlative research that relates the distribution or abundance of a species to that of a putative non-native species, and (2) from experimental tests of the effects of a non-native species on survival, growth, development or behaviour of a target species (Kats and Ferrer 2003). Over the past two decades, research on the effects of non-native species on amphibians has mostly focused on introduced aquatic predators, particularly fish. Recent research has shifted to more complex ecological relationships such as influences of sub-lethal stressors (e.g. contaminants) on the effects of non-native species (Linder et al. 2003; Sih et al. 2004), non-native species as vectors of disease (Daszak et al. 2004; Garner et al. 2006), hybridization between non-natives and native congeners (Riley et al. 2003; Storfer et al. 2004), and the alteration of food-webs by non-native species (Nystrom et al. 2001). Other research has examined the interaction of non-native species in terms of facilitation (i.e. one non-native enabling another to become established or spread) or the synergistic effects of multiple non-native species on native amphibians, the so-called invasional meltdown hypothesis (Simerloff and Von Holle 1999). Although there is evidence that some non-native species may interact (Ricciardi 2001), there has yet to be convincing evidence that such interactions have led to an accelerated increase in the number of non-native species and cumulative impacts are still uncertain (Simberloff 2006). Applied research on the control, eradication, and management of non-native species has only just begun but some promising results have already emerged (see below), giving hope to a very difficult conservation issue. This chapter provides an overview of the role of non-native species in amphibian declines and summarizes the current state of knowledge of non-native species that are known, or considered to be, a threat to amphibian species and populations. The biological and socio-economic issues of non-native species control are examined and brief case studies of successful eradication programmes are provided.

Book chapter↗

USGS2012

Ecological impacts of non-native species

Book chapter↗

USGS2023

Empirical evidence for effects of invasive American Bullfrogs on occurrence of native amphibians and emerging pathogens

Invasive species and emerging infectious diseases are two of the greatest threats to biodiversity. American Bullfrogs ( Rana [ Lithobates ] catesbeiana ), which have been introduced to many parts of the world, are often linked with declines of native amphibians via predation and spreading emerging pathogens such as amphibian chytrid fungus ( Batrachochytrium dendrobatidis [Bd]) and ranaviruses. Although many studies have investigated the potential role of bullfrogs in declines of native amphibians, analyses that account for shared habitat affinities and imperfect detection have found limited support for clear effects. Similarly, the role of bullfrogs in shaping the patch-level distribution of pathogens is unclear. We used eDNA methods to sample 233 sites in the southwestern USA and Sonora, Mexico (2016–2018) to estimate how presence of bullfrogs affects occurrence of 4 native amphibians, Bd, and ranaviruses. Based on 2-species, dominant-subordinate occupancy models fitted in a Bayesian context, federally threatened Chiricahua Leopard Frogs ( R. chiricahuensis ) and Western Tiger Salamanders ( Ambystoma mavortium ) were 8 times (32% vs. 4%) and 2 times (36% vs. 18%), respectively, less likely to occur at sites where bullfrogs occurred. Evidence for negative effects of bullfrogs on Lowland Leopard Frogs ( R. yavapaiensis ) and Northern Leopard Frogs ( R. pipiens ) was less clear, possibly because of smaller numbers of sites where these native species still occur and because bullfrogs often occur at lower densities in streams, the primary habitat for Lowland Leopard Frogs. At the community level, Bd was most likely to occur where bullfrogs co-occurred with native amphibians, which could increase risk to native species. Ranaviruses were estimated to occur at 33% of bullfrog-only sites, 10% of sites where bullfrogs and native amphibians co-occurred, and only 3% of sites where only native amphibians occurred. Of the 85 sites where we did not detect any of the 5 target amphibian species, we also did not detect Bd or ranaviruses; this suggests other hosts do not drive the distribution of these pathogens in our study area. Our results provide landscape-scale evidence that bullfrogs reduce occurrence of native amphibians and increase occurrence of pathogens, information that can clarify risks and aid the prioritization of conservation actions.

Ecological Applications↗

USGS2019

Managing for multiple species: Greater sage‐grouse and sagebrush songbirds

Human activity has altered 33–50% of Earth's surface, including temperate grasslands and sagebrush rangelands, resulting in a loss of biodiversity. By promoting habitat for sensitive or wide‐ranging species, less exigent species may be protected in an umbrella effect. The greater sage‐grouse ( Centrocercus urophasianus ; sage‐grouse) has been proposed as an umbrella for other sagebrush‐obligate species because it has an extensive range that overlaps with many other species, it is sensitive to anthropogenic activity, it requires resources over large landscapes, and its habitat needs are known. The efficacy of the umbrella concept, however, is often assumed and rarely tested. Therefore, we surveyed sage‐grouse pellet occurrence and sagebrush‐associated songbird abundance in northwest Colorado, USA, to determine the amount of habitat overlap between sage‐grouse and 4 songbirds (Brewer's sparrow [ Spizella breweri ], sage thrasher [ Oreoscoptes montanus ], sagebrush sparrow [ Artemisiospiza nevadensis ]), and green‐tailed towhee [ Pipilo chlorurus ]). During May and June 2013–2015, we conducted standard point count breeding surveys for songbirds and counted sage‐grouse pellets within 300 10‐m radius plots. We modeled songbird abundance and sage‐grouse pellet occurrence with multi‐scaled environmental features, such as sagebrush cover and bare ground. To evaluate sage‐grouse as an umbrella for sagebrush‐associated passerines, we determined the correlation between probability of sage‐grouse pellet occurrence and model‐predicted songbird densities per sampling plot. We then classified the sage‐grouse probability of occurrence as high (probability >0.5) and low (probability ≤0.5) and mapped model‐predicted surfaces for each species in our study area. We determined average songbird density in areas of high and low probability of sage‐grouse occurrence. Sagebrush cover at intermediate scales was an important predictor for all species, and ground cover was important for all species except sage thrashers. Areas with a higher probability of sage‐grouse occurrence also contained higher densities of Brewer's sparrows, green‐tailed towhees, and sage thrashers, but predicted sagebrush sparrow densities were lower in these areas. In northwest Colorado, sage‐grouse may be an effective umbrella for Brewer's sparrows, green‐tailed towhees, and sage thrashers, but sage‐grouse habitat does not appear to capture areas that support high sagebrush sparrow densities. A multi‐species focus may be the best management and conservation strategy for several species of concern, especially those with conflicting habitat requirements.

Colorado↗

USGS2021

Evaluation of regulatory action and surveillance as preventive risk-mitigation to an emerging global amphibian pathogen Batrachochytrium salamandrivorans (Bsal)

The emerging amphibian pathogen Batrachochytrium salamandrivorans (Bsal) is a severe threat to global urodelan (salamanders, newts, and related taxa) biodiversity. Bsal has not been detected, to date, in North America, but the risk is high because North America is one of the global hotspots for urodelan biodiversity. The North American and United States response to the discovery of Bsal in Europe was to take a risk-based approach to preventive management actions, including interim regulations on importation of captive salamanders and a large-scale surveillance effort. Risk-based approaches to decision-making can extend to adaptive management cycles by periodically incorporating new information that reduces uncertainty in an estimate of risk or to assess the effect of mitigation actions which reduce risk directly. Our objectives were to evaluate the effects of regulatory action on the introduction of Bsal to the U.S., quantify how a large-scale surveillance effort impacted consequence risk, and to combine other new information on species susceptibility to re-evaluate Bsal risk to the U.S. Import regulations effectively reduced import volume of targeted species, but new research on species susceptibility suggests the list of regulated species was incomplete regarding Bsal reservoir species. Not detecting Bsal in an intensive surveillance effort improved confidence that Bsal was not present, however, the overall risk-reduction impact was limited because of the expansive area of interest (conterminous United States) and limited time frame of sampling. Overall, the preventive actions in response to the Bsal threat did reduce Bsal risk in the U.S. and we present an updated risk assessment to provide information for adaptive decision-making.

Biological Conservation↗

USGS2018

Slow and steady wins the race? Future climate and land use change leaves the imperiled Blanding's turtle (Emydoidea blandingii) behind

Climate change is accompanied by shifts in species distributions, as portions of current ranges become less suitable. Maintaining or improving landscape connectivity to facilitate species movements is a primary approach to mitigate the effects of climate change on biodiversity. However, it is not clear how ongoing changes in land use and climate may affect the existing connectivity of landscapes. We evaluated shifts in habitat suitability and connectivity for the imperiled Blanding's turtle ( Emydoidea blandingii ) in Wisconsin using species distribution modeling in combination with different future scenarios of both land use change and climate change for the 2050s. We found that climate change had significant effects on both habitat suitability and connectivity, however, there was little difference in the magnitude of effects among different economic scenarios. Under both our low- and high-CO 2 emissions scenarios, suitable habitat for the Blanding's turtle shifted northward. In the high-emissions scenario, almost no suitable habitat remained for Blanding's turtle in Wisconsin by the 2050s and there was up to a 100,000-fold increase in landscape resistance to turtle movement, suggesting the landscape essentially becomes impassable. Habitat loss and landscape resistance were exponentially greater in southern versus northern Wisconsin, indicating a strong trailing edge effect. Thus, populations at the southern edge of the range are likely to “fall behind” shifts in suitable habitat faster than northern populations. Given its limited dispersal capability, loss of suitable habitat may occur at a rate far faster than the Blanding's turtle can adjust to changing conditions via shifts in range.

Wisconsin↗

USGS2021

Reproductive plasticity as an advantage of snakes during island invasion

Most invasive species are not studied during their initial colonization of ecosystems to which they were recently introduced. Rather, research is typically performed after invasive species are well established and causing harm to the native biodiversity. Thus, novel adaptations of invasive species during their initial invasions are rarely identified. The California kingsnake ( Lampropeltis californiae ) is an invasive species in the Canary Islands that originated via escape or release from captive populations. Previous studies have demonstrated several morphological differences between the native California population and the invasive populations on Gran Canaria Island, particularly in regard to color pattern and body mass. In this study, we assessed the reproductive condition of 1,538 museum specimens of L. californiae from the native range, and 668 from Gran Canaria. Our results show that 57.1% of female L. californiae from Gran Canaria were gravid versus 13.4% of those from California. Moreover, average follicle size and clutch size were both greater in the invasive range (20.3 and 65%). In addition, there was a marked phenological shift in the invasive populations, among which follicles appeared 60 days sooner than in the native range. These differences can possibly be attributed to a larger body mass in the invasive populations, a lack of interspecific competition, origination from the pet trade, increased selection for large clutch sizes, and/or increased climate suitability in the invaded habitats. Overall, these reproductive and phenological attributes appear to constitute advantages for L. californiae during the invasion of this newly encountered ecosystem. The phenomenon of reproductive plasticity might generally be advantageous for rapid irruption of snakes on islands.

Conservation Science and Practice↗

USGS2022

Population viability analysis for a pond-breeding amphibian under future drought scenarios in the southeastern United States

Climate change effects are contributing to widespread declines of amphibians, and pond-breeding species may be particularly sensitive to future drought conditions that restrict wetland hydroperiods and decrease opportunities for successful breeding and recruitment. Pond-breeding amphibian populations can compensate for periodic droughts via episodic booms in recruitment, but studies predict that increased future drought conditions will negatively impact long-term persistence for several species. The southeastern United States is a global hotspot of amphibian biodiversity where future trends in drought conditions are uncertain. This study applied a population viability analysis (PVA) framework for an at-risk amphibian, the gopher frog ( Lithobates [ Rana ] capito ), to (i) explore population sensitivity to the frequency of droughts that restrict reproductive events, relative to changes in other demographic rates, and (ii) forecast future population viability over 30 years, given plausible scenarios varying in the frequency and duration of droughts adapted from recent historical patterns in the southeastern United States. Population persistence was highly sensitive to frequency of reproductive success. Persistence was fairly insensitive to all demographic parameters when reproductive success was ≥ 0.7 (i.e., ≤ 3 drought years per decade, on average), but sensitivity to survival of terrestrial stages (juvenile, adults) and initial abundance increased as reproductive success decreased. Persistence probabilities were relatively high (0.63–0.99) across a range of plausible future drought scenarios, with higher persistence probabilities (> 0.89) for all scenarios where drought years did not increase from recent historical conditions. Our results indicate gopher frog populations are likely resilient to periodic droughts that occur in 4 or fewer years per decade, but extirpation of some populations is possible if recent drought patterns repeat or increase during the next 30 years. Estimates of future risk to gopher frog populations can inform forthcoming status assessments and designation decisions of the U.S. Fish and Wildlife Service. More broadly, PVAs incorporating drought dynamics can identify climate thresholds that at-risk, pond-breeding amphibian populations can tolerate, which can inform management actions (e.g., maintaining a range of hydroperiods across proximate wetlands) that provide sufficient frequent breeding opportunities for long-term persistence even under drought conditions.

Global Ecology and Conservation↗

USGS2024

Flexible migration and habitat use strategies of an endangered waterbird during hydrological drought

Wildlife species confront threats from climate and land use change, exacerbating the influence of extreme climatic events on populations and biodiversity. Migratory waterbirds are especially vulnerable to hydrological drought via reduced availability of surface water habitats. We assessed how whooping cranes ( Grus americana ) modified habitat use and migration strategies during drought to evaluate their resilience to changing conditions and adaptive capacity. We categorized >8000 night-roost sites used by 146 cranes from 2010 to 2022 and examined relative use during non-drought, moderate drought, and extreme drought conditions. We found cultivated and uncultivated palustrine and lacustrine wetlands were generally used less during droughts than non-drought conditions. Conversely, impounded palustrine and lacustrine systems and rivers served more frequently as drought refugia (i.e., used more during drought than non-drought conditions). Night roosts occurred primarily on private lands (86% overall); public land use decreased with latitude and increased with drought severity, with greatest use (56%) occurring during severe autumn drought in the southern Great Plains. Quantifying use of identified critical habitats in the United States indicated that Cheyenne Bottoms State Waterfowl Management Area and Quivira National Wildlife Refuge were used less during drought, and the Central Platte River and Salt Plains National Wildlife Refuge received similar use during drought compared to non-drought conditions. Our findings provide insights into compensatory use of habitats, where impounded surface water may function in a complementary fashion with natural wetlands. Collectively, these and other types of wetlands distributed across the migration corridor provided a reliable network of habitat available across the Great Plains. A diversity of wetlands available during variable environmental conditions would be useful in supporting continued recovery of whooping cranes and likely have benefits for a wide array of migratory birds.

Conservation Science and Practice↗

USGS2009

Prevention, early detection and containment of invasive, nonnative plants in the Hawaiian Islands: current efforts and needs

Introduction: Invasive, non-native plants (or environmental weeds) have long been recognized as a major threat to the native biodiversity of oceanic islands (Cronk & Fuller, 1995; Denslow, 2003). Globally, several hundred non-native plant species have been reported to have major impacts on natural areas on oceanic islands (Kueffer et al ., 2009). In Hawaii, at least some 50 non-native plant species reach dominance in natural areas (Kueffer et al ., 2009) and many of them are known to impact ecosystem processes or biodiversity. One example is the invasive Australian tree fern ( Cyathea cooperi ), which has been shown to be very efficient at utilizing soil nitrogen and can grow six times as rapidly in height, maintain four times more fronds, and produce significantly more fertile fronds per month than the native Hawaiian endemic tree ferns, Cibotium spp. (Durand & Goldstein, 2001a, b). Additionally, while native tree ferns provide an ideal substrate for epiphytic growth of many understory ferns and flowering plants, the Australian tree fern has the effect of impoverishing the understory and failing to support an abundance of native epiphytes (Medeiros & Loope, 1993). Other notorious examples of invasive plant species problematic for biodiversity and ecosystem processes in Hawaii include miconia ( Miconia calvescens ), strawberry guava ( Psidium cattleianum ), albizia ( Falcataria moluccana ), firetree ( Morella faya ), clidemia ( Clidemia hirta ), kahili ginger ( Hedychium gardnerianum ), and fountain grass ( Pennisetum setaceum ), to name just a few. Fireweed ( Senecio madagascariensis ) is a recent example of a seriously problematic invasive species for Hawaii’s agriculture and is damaging certain high-elevations native ecosystems as well. The threat of invasive plants has long been recognized in Hawaii and is well documented (e.g. Cox, 1999; Loope & Kraus, 2009 in press; Loope et al ., 2004; Mooney & Drake, 1986; Stone & Scott, 1985; Stone et al. , 1992). In many respects, Hawaii may be near the forefront among national and international efforts to address the burgeoning threat of invasive plants, perhaps especially in the field of outreach and education (Holt, 1996; Van Driesche & Van Driesche, 2000). However, given the scale of the problem many challenges still need to be addressed and gaps in the existing management system need to be identified. In particular, it appears that new non-native plant species are still introduced to the Hawaiian Islands at a high rate with little or no regard for their potential invasiveness. In fact, a Pacific-wide and a global survey of non-native plants on oceanic islands have both shown that on Hawaii among all archipelagos by far the highest number of problematic invasive species known from other areas in the world is already present (Denslow et al . 2009, Kueffer et al . 2009). Hawaii lacks an effective mechanism for tracking what species are present or incoming. For instance, early detection nursery surveys conducted on Maui in 2008 found over 300 species of cultivated vascular plants that have not previously been recorded in Hawaii (Starr et al. , in prep.). In spite of an innovative Hawaii Biological Survey (e.g. Eldredge & Evenhuis, 2003), there is no mechanism for recording presence of a species until it becomes naturalized. Some of these new introductions may quickly become serious pests. Fireweed, first recorded in Hawaii on the Big Island in the early 1980s, is now considered one of the Kueffer & Loope 2009 5/48 worst weeds of pastures and is also invading natural areas from near sea level to above 10,000 feet. Although the cultivated and as yet non-invasive Cortaderia selloana has been present in Hawaii for 50 years or more, the morphologically similar Cortaderia jubata was simultaneously found to be present on Maui and invading on a large scale in 1989. It played an important role in inspiring the establishment of the Maui Invasive Species Committee (MISC) in 1997, and MISC now spends roughly $200,000 per year removing and containing C. jubata to keep it from becoming widespread in high elevation conservation lands of East and West Maui. The existence of many similar examples shows that to date regulatory action to prevent new invasive plant species from establishing and spreading in Hawaii has not yet been as successful as it needs to be. In particular, because some problematic invasive species known from other areas in the world (Kueffer et al ., 2009; Weber, 2003) have not yet been recorded from Hawaii, preventive measures against the introduction and spread of such likely invasive species is therefore an urgent need for Hawaii. Indeed, regulation of importation and early detection and eradication of introduced species before they become abundant and widespread are widely considered the most cost-efficient and often only effective measures against the threat of new invasive species (Kueffer & Hirsch Hadorn, 2008; Wittenberg & Cock, 2001). Timing seems favorable for Hawaii to achieve effective protection against the threat of new invasive species through prevention, early detection, and eradication/containment. Through the establishment and evolution of Invasive Species Committees (ISCs) on each major Hawaiian island, the institutional capacity has been built up for prevention, early detection, containment, and outreach at an island scale. Weed risk assessment (Daehler et al ., 2004) and early detection methodologies (Starr et al. , in review-a, b) have been developed and tested specifically for Hawaii. Containment strategies have been successful (e.g., Special Ecological Areas in Hawaii Volcanoes National Park), and so have eradications of particular species on an island scale (e.g. mullein ( Verbascum thapsus ) and other species on Maui, fireweed ( Senecio madagascariensis ) on Kauai). These successful management strategies may be further strengthened through recently developed novel approaches in research (e.g. remote sensing, species distribution modelling, and molecular genetics tools). Another major recent achievement is the gained support of the plant industry for preventive measures against invasive species (see p. 13ff). Last but not least, regulatory action is also moving forward. Passage of House Bill 2517 by the 2008 Hawaii House and Senate and prompt signing of the bill into law by the Governor provides hope that action to ban the sale of a meaningful suite of restricted weeds can quickly proceed through the rulemaking phase into the implementation phase. This report documents these achievements and experiences and provides a range of perspectives on how to further develop prevention, early detection and containment of invasive species in Hawaii. The report is based on a symposium and workshop held at the 2008 Hawaii Conservation Conference in Honolulu on 31 July 2008.

Hawaii↗

USGS2014

Acceptability of residential development in a regional landscape: Potential effects on wildlife occupancy patterns

The conversion of natural lands to developed uses may pose the single greatest human threat to global terrestrial biodiversity. Continued human growth and development over the next century will further exacerbate these effects of habitat loss and fragmentation. Natural resource managers are tasked with managing wildlife as a public trust, yet often have little say in land use decisions. Generally speaking, decision makers could benefit from an understanding of what different regulations mean in terms of wildlife distribution. In a previous paper ( Bettigole et al., 2013 ), we surveyed town residents throughout Vermont to measure how respondents feel about a range of development levels within their town boundaries. We estimated the “social carrying capacity for development” – or SK d – for 251 towns in Vermont. SK d provides an estimate of the level of developed land cover classes that town residents deem “acceptable” within their town boundaries. In this paper, we design a framework for linking the town-specific SK d estimates with the wildlife distribution patterns for three wide-ranging mammalian species: American black bear ( Ursus americanus ), fisher ( Martes pennanti ), and bobcat ( Lynx rufus ). We simulated landscape conditions at SK d for each town in Vermont, and then used existing occupancy models for the three target species to spatially map and compare occupancy rates in the baseline year 2000 with occupancy rates at SK d . With nearly 90% of Vermont towns willing to increase developed landcover classes within town boundaries compared to baseline levels, significant state-wide changes in occupancy rates were predicted for all three focal species. Average occupancy rates declined by −15.9% and −3.1% for black bear and bobcats, respectively. Average occupancy rates for fisher increased by 9.0%. This study provides a method for linking development standards within a town with wildlife occurrence. Across towns, the methodology spatially identifies areas that may be at risk of future development, as well as identifying areas where wildlife distribution patterns may face future change as a result of increased human population growth and development.

Biological Conservation↗

USGS2010

The potential influence of changing climate on the persistence of salmonids of the inland west

The Earth's climate warmed steadily during the 20th century, and mean annual air temperatures are estimated to have increased by 0.6°C (Intergovernmental Panel on Climate Change, 2007). Although many cycles of warming and cooling have occurred in the past, the most recent warming period is unique in its rate and magnitude of change (Siegenthaler and others, 2005) and in its association with anthropogenic emissions of greenhouse gases (Intergovernmental Panel on Climate Change , 2007). The climate in the western United States warmed in concert with the global trend but at an accelerated rate (+0.8°C during the 20th century; Saunders and others, 2008). The region could also prove especially sensitive to future changes because the relatively small human population is growing rapidly, as are demands on limited water supplies. Regional hydrological patterns are dominated by seasonal snow accumulation at upper elevations. Most of the region is relatively dry, and both terrestrial and aquatic ecosystems are strongly constrained b y water availability (Barnett and others, 2008; Brown and others, 2008). Stream environments are dynamic and climatically extreme, and salmonid fishes are the dominant elements of the native biodiversity (McPhail and Lindsey, 1986; Waples and others, 2008). Salmonids have broad economic and ecologic importance, but a century of intensive water resource development, nonnative fish stocking, and land use has significantly reduced many populations and several taxa are now protected under the Endangered Species Act (Thurow and others, 1997; Trotter, 2008). Because salmonids require relatively pristine, cold water environments and are often isolated in headwater habitats, members of this group may be especially vulnerable to the effects of a warming climate (Keleher and Rahel, 1996; Rieman and others, 2007; Williams and others, 2009). Warming during the 20th century drove a series of environmental trends that have profound implications for many aspects of salmonid habitat, including disturbance regimes such as wildfire, and unfavorable changes to thermal and hydrologic properties of aquatic systems. Warmer air temperatures have been associated with decreased winter snow accumulations, have accelerated snowmelt, and have advanced the timing of peak runoff by several days to weeks across most of western North America (Stewart and others, 2005; Barnett and others, 2008). Less snow and earlier runoff decrease aquifer recharge, make less water available for groundwater inputs to streams, and are contributing to widespread decreases in summer low flows (Stewart and others, 2005; Rood and others, 2008; Luce and Holden 2009). Interannual variability in stream flow is increasing, as is the persistence of multi-year extreme conditions (McCabe and others, 2004; Pagano and Garen 2005). In many areas of western North America, flood risks have increased in association with warmer temperatures during the 20th century (Hamlet and Lettenmaier, 2005). Streams where midwinter temperatures are near freezing have proven especially sensitive to increased flooding because of associated transitional hydrological patterns (mixtures of rainfall and snowmelt) and propensity for occasional rain-on-snow events to rapidly melt winter snowpack and generate large floods (Hamlet and Lettenmaier, 2005). Stream temperatures in many areas are increasing (Peterson and Kitchell, 2001; Morrison and others, 2002; Bartholow, 2005; Kaushal and others, 2010), due to both air temperature increases and reduced summer flows that make streams more sensitive to warmer air temperatures (Isaak and others, 2010). In recent decades, wildfires have become more common across much of the western United States during periods of more frequent droughts (Westerling and others, 2006; Hoerling and Eischeid, 2007), and local stream temperature can increase in postfire environments (Gresswell, 1999; Dunham and others, 2007). Fire-related temperature increase within streams is commonly a transient phenomenon, lasting only until riparian vegetation has recovered (Gresswell, 1999); however, ongoing climate change could preclude recovery to higher stature, prefire vegetation types in some areas (McKenzie and others, 2004; van Mantgem and Stephenson, 2007), resulting in a loss of critical riparian shading. Additionally, when wildfires occur in steep mountain topographies, the vegetation that stabilize s soils on hillslopes is often killed and landslides become more prevalent (Gresswell, 1999). Landslides int o stream channels form debris flows composed of sediment slurries and dead trees that can scour channels to bedrock and further exacerbate stream heating, delay recovery of riparian areas, or extirpate fish populations (Gresswell, 1999; May and Gresswell, 2003; Dunham and others, 2007). Changes in stream environments will shift habitat distributions, sometimes unpredictably, in both time and space for many salmonid fishes. Water temperature fundamentally influences aquatic ecosystem health because distribution, reproduction, fitness, and survival of ectothermic organisms are inextricably linked to the thermal regime of the environment. Historically, research has focused on defining lethal thermal limits of salmonids (Eaton and others, 1995; Selong and others, 2001; Todd and others, 2008); however, water temperature is known to be important in biological processes at a variety of spatial scales and levels of biological organization (Rahel and Olden, 2008; McCullough and others, 2009). For instance, trout are affected directly by water temperature through feeding, metabolism, and growth rates, and indirectly by factors such as prey availability and species interactions (Wehrly and others, 2007; Rahel and Olden, 2008). Where cold water temperatures currently limit habitat suitability and distributions of some species (for example, at the highest and most northerly distributional extents; Nakano and others, 1996; Coleman and Fausch, 2007), a warming climate may gradually increase the quality and extent of suitable habitat. Over time, previously constrained populations are expected to expand into these new habitats and increase in number. Some evidence suggests this may already be happening in Alaska, where streams in recently deglaciated areas are being colonized by emigrants from nearby salmon and char populations (Milner and others, 2000). Unfortunately, many of the sensitive salmonid species that are often the focus of western managers are unlikely to benefit from future water temperature increases. Warmer stream temperatures will facilitate invasion by nonnative species that are broadly established in downstream areas into upstream areas where they will compete with native species (Rieman and others, 2006; Rahel and Olden, 2008; Fausch and others, 2009). In other cases, warmer stream temperatures will render thermally suitable habitats unsuitable in downstream areas and effect net losses of habitat because upstream distributions are often constrained by streams that are too small or steep (Hari and others, 2006; Isaak and others, 2010). Both scenarios are realistic for fish species like bull trout ( Salvelinus confluentus ) (Rieman and others, 2006; Rieman and others, 2007), the various subspecies of cutthroat trout ( Oncorhynchus clarkii ) (Williams and others, 2009), Gila trout ( Oncorhynchus gilae gilae ) (Kennedy and others, 2008), and Apache trout ( Oncorhynchus gilae apache ) (Rinne and Minckley, 1985; Carmichael and others, 1993). As native species are increasingly confined to smaller and more isolated habitats by a gradually warming climate, the effects of wildfires (whether related to lethal changes in water quality during a fire, channel debris flows, or chronic postfire warming ) could have greater proportional effects on remaining habitats (for example, Brown and others, 2001; Rieman and others, 2007). If these changes were accompanied by additional hydrologic alterations associated with changes to the magnitude, frequency, duration, timing, and rate of change of discharge patterns (Jager and others, 1999; Henderson and others, 2000), populations may begin to lose some of their historic resilience and become ever more susceptible to local extirpations. As dramatic and extensive as climatic and environmental trends are for salmonid habitats, global climate models (GCMs) project that many of these trends will continue and even accelerate until at least the middle of the 21st century (Intergovernmental Panel on Climate Change, 2007). Current projections suggest mean annual air temperatures will increase by an additional 1–3°C, and early indications are that climate trajectory is at the higher end of this range (Pittock, 2006; Raupach and others, 2007). Although predicted changes vary considerably, even the most conservative estimates suggest a warming rate that will be twice that observed during the 20th century. Projections for the midcentury are most certainly due to the effects of greenhouse gases already emitted or predicted in the short term, uncertainties of the effects of longer-term greenhouse gas emissions, short-term climate cycles, and process errors associated with climate models (Cox and Stephenson, 2007). Projections of changes in total precipitation are less certain than those for air temperatures, but most GCMs project relatively small changes in the Northwest, with the exception of slightly drier summer periods (Mote and others, 2008; Karl and others, 2009). In the Southwest, however, significant decreases (such as 15–30 percent ) are projected during most periods of the year, and this area is one of the few for which Intergovernmental Panel on Climate Change (2007) precipitation projections have a high level of certainty (Hoerling and Eischeid, 2007; Karl and others, 2009). Clearly, managers of native salmonids in the wester n United States should consider adjusting management strategies to accommodate a warmer and possibly drier future (Williams and others, 2009). Tools are needed to forecast where important changes may occur and how conservation efforts should be prioritized. In this Open-File Report, we document our initial efforts in this regard for 10 species and subspecies of inland trout and Montana Arctic grayling ( Thymallus arcticus ) across the western United States.

Arizona, California, Colorado, Idaho, Montana, Nev↗