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Results for “Climate Change Responses”

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At least 325 records · Page 18Linked to original sources
USGS2011

Flow regime, temperature, and biotic interactions drive differential declines of trout species under climate change

Broad-scale studies of climate change effects on freshwater species have focused mainly on temperature, ignoring critical drivers such as flow regime and biotic interactions. We use downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows and increased temperatures on four interacting species of trout across the interior western United States (1.01 million km 2 ), based on empirical statistical models built from fish surveys at 9,890 sites. Projections under the 2080s A1B emissions scenario forecast a mean 47% decline in total suitable habitat for all trout, a group of fishes of major socioeconomic and ecological significance. We project that native cutthroat trout Oncorhynchus clarkii , already excluded from much of its potential range by nonnative species, will lose a further 58% of habitat due to an increase in temperatures beyond the species' physiological optima and continued negative biotic interactions. Habitat for nonnative brook trout Salvelinus fontinalis and brown trout Salmo trutta is predicted to decline by 77% and 48%, respectively, driven by increases in temperature and winter flood frequency caused by warmer, rainier winters. Habitat for rainbow trout, Oncorhynchus mykiss , is projected to decline the least (35%) because negative temperature effects are partly offset by flow regime shifts that benefit the species. These results illustrate how drivers other than temperature influence species response to climate change. Despite some uncertainty, large declines in trout habitat are likely, but our findings point to opportunities for strategic targeting of mitigation efforts to appropriate stressors and locations.

Proceedings of the National Academy of Sciences of↗
USGS2022

Expression plasticity regulates intraspecific variation in the acclimatization potential of a reef-building coral

Phenotypic plasticity is an important ecological and evolutionary response for organisms experiencing environmental change, but the ubiquity of this capacity within coral species and across symbiont communities is unknown. We exposed ten genotypes of the reef-building coral Montipora capitata with divergent symbiont communities to four thermal pre-exposure profiles and quantified gene expression before stress testing 4 months later. Here we show two pre-exposure profiles significantly enhance thermal tolerance despite broadly different expression patterns and substantial variation in acclimatization potential based on coral genotype. There was no relationship between a genotype’s basal thermal sensitivity and ability to acquire heat tolerance, including in corals harboring naturally tolerant symbionts, which illustrates the potential for additive improvements in coral response to climate change. These results represent durable improvements from short-term stress hardening of reef-building corals and substantial cryptic complexity in the capacity for plasticity.

Nature Communications↗
USGS2017

The effect of Holocene temperature fluctuations on the evolution and ecology of Neotoma (woodrats) in Idaho and northwestern Utah

Animals respond to climatic change by adapting or by altering distributional patterns. How an animal responds is influenced by where it is positioned within its geographic range; the probability of extirpation is increased near range boundaries. Here, we examine the impact of Holocene climatic fluctuations on a small mammalian herbivore, the bushy-tailed woodrat (Neotoma cinerea), at five locations within south central Idaho and northwestern Utah. Previous work demonstrated that woodrats adapt to temperature shifts by altering body size. We focus here on the relationship between body mass, temperature, and location within the geographic range. Body mass is estimated by measuring fossil fecal pellets, a technique validated in earlier work. Overall, we find the predicted phenotypic response to climate change: Animals were larger during cold periods, and smaller during warmer episodes. However, we also identify several time periods when changes in environmental temperature exceeded the adaptive flexibility of N. cinerea. A smaller-bodied species, the desert woodrat (N. lepida) apparently invaded lower elevation sites during the mid-Holocene, despite being behaviorally and physically subordinate to N. cinerea. Analysis of contemporary patterns of body size and thermal tolerances for both woodrat species suggests this was because of the greater heat tolerance of N. lepida. The robust spatial relationship between contemporary body size and ambient temperature is used as a proxy to reconstruct local climate during the Holocene. ?? 2003 Elsevier Science (USA). All rights reserved.

Quaternary Research↗
USGS2021

Nonlinear shifts in infectious rust disease due to climate change

Range shifts of infectious plant disease are expected under climate change. As plant diseases move, emergent abiotic-biotic interactions are predicted to modify their distributions, leading to unexpected changes in disease risk. Evidence of these complex range shifts due to climate change, however, remains largely speculative. Here, we combine a long-term study of the infectious tree disease, white pine blister rust, with a six-year field assessment of drought-disease interactions in the southern Sierra Nevada. We find that climate change between 1996 and 2016 moved the climate optimum of the disease into higher elevations. The nonlinear climate change-disease relationship contributed to an estimated 5.5 (4.4–6.6) percentage points (p.p.) decline in disease prevalence in arid regions and an estimated 6.8 (5.8–7.9) p.p. increase in colder regions. Though climate change likely expanded the suitable area for blister rust by 777.9 (1.0–1392.9) km 2 into previously inhospitable regions, the combination of host-pathogen and drought-disease interactions contributed to a substantial decrease (32.79%) in mean disease prevalence between surveys. Specifically, declining alternate host abundance suppressed infection probabilities at high elevations, even as climatic conditions became more suitable. Further, drought-disease interactions varied in strength and direction across an aridity gradient—likely decreasing infection risk at low elevations while simultaneously increasing infection risk at high elevations. These results highlight the critical role of aridity in modifying host-pathogen-drought interactions. Variation in aridity across topographic gradients can strongly mediate plant disease range shifts in response to climate change.

California↗
USGS2023

Effects of climate change on the hydrologic and hydraulic response of the Caulks Creek basin, Wildwood, Missouri

The city of Wildwood, Missouri, has identified fluvial erosion along Caulks Creek as a management priority due to potential effects to infrastructure and property. The upper and middle reaches of Caulks Creek flow intermittently (only immediately after precipitation), whereas the lower reach flows perennially. This study examines the effects of climate change and added storage on the hydrologic and hydraulic response of the Caulks Creek Basin to design storms. The study uses hydrologic (Hydrologic Engineering Center Hydrologic Modeling System – HEC-HMS) and hydraulic (Hydrologic Engineering Center River Analysis System – HEC-RAS) models furnished by the Federal Emergency Management Agency (FEMA). HEC-HMS simulations were used to quantify the peak, volume, and timing of the flow response to a suite of design storms under both normal and wet antecedent conditions and for both the existing storage structures and new storage in the basin. The suite of design storms included all combinations of the following: (a) storm durations: 6-hour and 24-hour, (b) annual exceedance probabilities: 0.5, 0.2, 0.1, 0.04, 0.02, and 0.01, (c) climate conditions: current, 30-year, and 80-year predictions of future climate from the Coupled Model Intercomparison Project (CMIP) Climate Data Processing Tool. Additionally, for a selection of scenarios, results from the HEC-HMS simulations were used as boundary conditions for two-dimensional (2D) HEC-RAS simulations aimed at understanding how the distribution of velocity, shear stress, and stream power throughout the stream may be affected by projected changes in climate.

Missouri↗
USGS2013

Space can substitute for time in predicting climate-change effects on biodiversity

“Space-for-time” substitution is widely used in biodiversity modeling to infer past or future trajectories of ecological systems from contemporary spatial patterns. However, the foundational assumption—that drivers of spatial gradients of species composition also drive temporal changes in diversity—rarely is tested. Here, we empirically test the space-for-time assumption by constructing orthogonal datasets of compositional turnover of plant taxa and climatic dissimilarity through time and across space from Late Quaternary pollen records in eastern North America, then modeling climate-driven compositional turnover. Predictions relying on space-for-time substitution were ∼72% as accurate as “time-for-time” predictions. However, space-for-time substitution performed poorly during the Holocene when temporal variation in climate was small relative to spatial variation and required subsampling to match the extent of spatial and temporal climatic gradients. Despite this caution, our results generally support the judicious use of space-for-time substitution in modeling community responses to climate change.

Proceedings of the National Academy of Sciences↗
USGS2020

Accounting for temporal variability of streamflow in estimates of travel time

Retention, processing, and transport of solutes and particulates in stream corridors are influenced by the travel time of streamflow through stream channels, which varies dynamically with discharge. The effects of streamflow variability across sites and over time cannot be addressed by time-averaged models if parameters are based solely on the characteristics of mean streamflow. We develop methods to account for the effects of streamflow variability on travel time and compare our estimates to flow-weighted (“effective”) travel time at 100 streams in the southeastern United States. Velocity time series were generated for each stream from multiple-year (median 15.5 years), high-frequency (15 min interval) records of instantaneous streamflow and field measurements of velocity and inverted to produce time series of specific travel time [T/L]. The effective travel times for streams are 60–90% of the specific travel time of mean streamflow because a large fraction of the total streamflow volume is discharged during higher flows with higher velocities. We find that adjusting the specific travel time of mean streamflow at a site by a factor of 0.81 generally accounts for the effect of a skewed streamflow distribution, but at-site estimates of the coefficient of variation of streamflow are necessary to resolve differences in streamflow variability between streams or changes in variability over time. For example, the effective travel time of urban streams is less than the effective travel of forested streams in the southeastern United States as a result of increased streamflow variability in urban streams. Effective travel time accounts for both the variation in velocity with streamflow and the large fraction of streamflow discharged during high flows in most streams and provides time-averaged models with limited capability to account for effects of streamflow variability that otherwise they lack. This capability is needed for continental-scale modeling where streamflow variability is not uniform because of heterogeneous surficial geology, hydro-climatology, and vegetation and for applications where streamflow variability is not stationary as a response to climate change or hydrologic alteration.

Alabama, Georgia, North Carolina, Virginia, South ↗
USGS2024

Declining groundwater storage expected to amplify mountain streamflow reductions in a warmer world

Groundwater interactions with mountain streams are often simplified in model projections, potentially leading to inaccurate estimates of streamflow response to climate change. Here, using a high-resolution, integrated hydrological model extending 400 m into the subsurface, we find groundwater an important and stable source of historical streamflow in a mountainous watershed of the Colorado River. In a warmer climate, increased forest water use is predicted to reduce groundwater recharge resulting in groundwater storage loss. Losses are expected to be most severe during dry years and cannot recover to historical levels even during simulated wet periods. Groundwater depletion substantially reduces annual streamflow with intermittent conditions predicted when precipitation is low. Expanding results across the region suggests groundwater declines will be highest in the Colorado Headwater and Gunnison basins. Our research highlights the tight coupling of vegetation and groundwater dynamics and that excluding explicit groundwater response to warming may underestimate future reductions in mountain streamflow.

Nature Water↗
USGS2014

Vulnerability of breeding waterbirds to climate change in the Prairie Pothole Region, U.S.A.

The Prairie Pothole Region (PPR) of the north-central U.S. and south-central Canada contains millions of small prairie wetlands that provide critical habitat to many migrating and breeding waterbirds. Due to their small size and the relatively dry climate of the region, these wetlands are considered at high risk for negative climate change effects as temperatures increase. To estimate the potential impacts of climate change on breeding waterbirds, we predicted current and future distributions of species common in the PPR using species distribution models (SDMs). We created regional-scale SDMs for the U.S. PPR using Breeding Bird Survey occurrence records for 1971–2011 and wetland, upland, and climate variables. For each species, we predicted current distribution based on climate records for 1981–2000 and projected future distributions to climate scenarios for 2040–2049. Species were projected to, on average, lose almost half their current habitat (-46%). However, individual species projections varied widely, from +8% (Upland Sandpiper) to -100% (Wilson's Snipe). Variable importance ranks indicated that land cover (wetland and upland) variables were generally more important than climate variables in predicting species distributions. However, climate variables were relatively more important during a drought period. Projected distributions of species responses to climate change contracted within current areas of distribution rather than shifting. Given the large variation in species-level impacts, we suggest that climate change mitigation efforts focus on species projected to be the most vulnerable by enacting targeted wetland management, easement acquisition, and restoration efforts.

Minnesota, North Dakota, South Dakota↗
USGS2003

Response of benthic foraminifers to sewage discharge and remediation in Santa Monica Bay, California

Examination of a time series of foraminiferal assemblage distributions on the continental shelf and slope of Santa Monica Bay from 1955 to 1997-1998 suggests that the benthic microfauna have been greatly affected by the quality and character of the municipal sludge and wastewater discharged into the bay over the last half-century by the Hyperion Treatment Plant serving the greater Los Angeles area. Five species dominate both the living and dead foraminiferal assemblages of the 1997-1998 surface samples, including Eggerella advena, Trochammina pacifica, Bulimina denudata, Buliminella elegantissima, and Epistominella bradyana. Temporal patterns of relative species abundances for both living and dead assemblages, as well as toxicity tests measuring amphipod survival and sea urchin fertilization success, show improvement since the sewage treatment program was enhanced in 1986. None of these trends are evident 10 years earlier, coincident with the onset of a Pacific Decadal Oscillation warming trend. This fact suggests that remediation, and not climate change, is responsible for the faunal changes observed. Even with remediation, however, all foraminiferal faunal trends have not returned to early-outfall levels. The organic-waste indicating species T. pacifica shows a slow decline in abundance as sewage treatment and sludge disposal activities have improved, whereas a dramatic increase in the abundance of the pioneer colonizer of impacted regions, E. advena, has occurred, often with a reciprocal response by B. denudata. Also evident is a dramatic shift in the abundance of the once-dominant species Nonionella basispinata and Nonionella stella, which were unable to recolonize Santa Monica Bay since the two major outfalls (5- and 7-mile) began discharging. Temporal variations in species abundances, as well as range expansions, contractions, and the inability to recolonize areas previously, or presently, impacted, suggests that foraminifers are a useful tool in defining areas affected by waste discharge.

Marine Environmental Research↗
USGS2025

The North American greenhouse gas budget: Emissions, removals, and integration for CO2, CH4, and N2O (2010–2019): Results From the Second REgional Carbon Cycle Assessment and Processes Study (RECCAP2)

Accurate accounting of greenhouse-gas (GHG) emissions and removals is central to tracking progress toward climate mitigation and for monitoring potential climate-change feedbacks. GHG budgeting and reporting can follow either the Intergovernmental Panel on Climate Change methodologies for National Greenhouse Gas Inventory (NGHGI) reporting or use atmospheric-based “top-down” (TD) inversions or process-based “bottom-up” (BU) approaches. To help understand and reconcile these approaches, the Second REgional Carbon Cycle Assessment and Processes study (RECCAP2) was established to quantify GHG emissions and removals for carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O), for ten-land and five-ocean regions for 2010–2019. Here, we present the results for the North American land region (Canada, the United States, Mexico, Central America and the Caribbean). For 2010–2019, the NGHGI reported total net-GHG emissions of 7,270 TgCO 2 -eq yr −1 compared to TD estimates of 6,132 ± 1,846 TgCO 2 -eq yr −1 and BU estimates of 9,060 ± 898 TgCO 2 -eq yr −1 . Reconciling differences between the NGHGI, TD and BU approaches depended on (a) accounting for lateral fluxes of CO 2 along the land-ocean-aquatic continuum (LOAC) and trade, (b) correcting land-use CO 2 emissions for the loss-of-additional-sink capacity (LASC), (c) avoiding double counting of inland water CH 4 emissions, and (d) adjusting area estimates to match the NGHGI definition of the managed-land proxy. Uncertainties remain from inland-water CO 2 evasion, the conversion of nitrogen fertilizers to N 2 O, and from less-frequent NGHGI reporting from non-Annex-1 countries. The RECCAP2 framework plays a key role in reconciling independent GHG-reporting methodologies to support policy commitments while providing insights into biogeochemical processes and responses to climate change.

Global Biogeochemical Cycles↗
USGS2017

Ad hoc instrumentation methods in ecological studies produce highly biased temperature measurements

In light of global climate change, ecological studies increasingly address effects of temperature on organisms and ecosystems. To measure air temperature at biologically relevant scales in the field, ecologists often use small, portable temperature sensors. Sensors must be shielded from solar radiation to provide accurate temperature measurements, but our review of 18 years of ecological literature indicates that shielding practices vary across studies (when reported at all), and that ecologists often invent and construct ad hoc radiation shields without testing their efficacy. We performed two field experiments to examine the accuracy of temperature observations from three commonly used portable data loggers (HOBO Pro, HOBO Pendant, and iButton hygrochron) housed in manufactured Gill shields or ad hoc, custom‐fabricated shields constructed from everyday materials such as plastic cups. We installed this sensor array (five replicates of 11 sensor‐shield combinations) at weather stations located in open and forested sites. HOBO Pro sensors with Gill shields were the most accurate devices, with a mean absolute error of 0.2°C relative to weather stations at each site. Error in ad hoc shield treatments ranged from 0.8 to 3.0°C, with the largest errors at the open site. We then deployed one replicate of each sensor‐shield combination at five sites that varied in the amount of urban impervious surface cover, which presents a further shielding challenge. Bias in sensors paired with ad hoc shields increased by up to 0.7°C for every 10% increase in impervious surface. Our results indicate that, due to variable shielding practices, the ecological literature likely includes highly biased temperature data that cannot be compared directly across studies. If left unaddressed, these errors will hinder efforts to predict biological responses to climate change. We call for greater standardization in how temperature data are recorded in the field, handled in analyses, and reported in publications.

Ecology and Evolution↗
USGS2021

Demographic risk assessment for a harvested species threatened by climate change: Polar bears in the Chukchi Sea

Climate change threatens global biodiversity. Many species vulnerable to climate change are important to humans for nutritional, cultural, and economic reasons. Polar bears Ursus maritimus are threatened by sea-ice loss and represent a subsistence resource for Indigenous people. We applied a novel population modeling-management framework that is based on species life history and accounts for habitat loss to evaluate subsistence harvest for the Chukchi Sea (CS) polar bear subpopulation. Harvest strategies followed a state-dependent approach under which new data were used to update the harvest on a predetermined management interval. We found that a harvest strategy with a starting total harvest rate of 2.7% (˜85 bears/yr at current abundance), a 2:1 male-to-female ratio, and a 10-yr management interval would likely maintain subpopulation abundance above maximum net productivity level for the next 35 yr (approximately three polar bear generations), our primary criterion for sustainability. Plausible bounds on starting total harvest rate were 1.7–3.9%, where the range reflects uncertainty due to sampling variation, environmental variation, model selection, and differing levels of risk tolerance. The risk of undesired demographic outcomes (e.g., overharvest) was positively related to harvest rate, management interval, and projected declines in environmental carrying capacity; and negatively related to precision in population data. Results reflect several lines of evidence that the CS subpopulation has been productive in recent years, although it is uncertain how long this will last as sea-ice loss continues. Our methods provide a template for balancing trade-offs among protection, use, research investment, and other factors. Demographic risk assessment and state-dependent management will become increasingly important for harvested species, like polar bears, that exhibit spatiotemporal variation in their response to climate change.

Chukchi Sea↗
USGS2024

Declining ecological resilience and invasion resistance under climate change in the sagebrush region, United States

In water-limited dryland ecosystems of the Western United States, climate change is intensifying the impacts of heat, drought, and wildfire. Disturbances often lead to increased abundance of invasive species, in part, because dryland restoration and rehabilitation are inhibited by limited moisture and infrequent plant recruitment events. Information on ecological resilience to disturbance (recovery potential) and resistance to invasive species can aid in addressing these challenges by informing long-term restoration and conservation planning. Here, we quantified the impacts of projected future climate on ecological resilience and invasion resistance (R&R) in the sagebrush region using novel algorithms based on ecologically relevant and climate-sensitive predictors of climate and ecological drought. We used a process-based ecohydrological model to project these predictor variables and resulting R&R indicators for two future climate scenarios and 20 climate models. Results suggested widespread future R&R decreases (24%–34% of the 1.16 million km 2 study area) that are generally consistent among climate models. Variables related to rising temperatures were most strongly linked to decreases in R&R indicators. New continuous R&R indices quantified responses to climate change; particularly useful for areas without projected change in the R&R category but where R&R still may decrease, for example, some of the areas with a historically low R&R category. Additionally, we found that areas currently characterized as having high sagebrush ecological integrity had the largest areal percentage with expected declines in R&R in the future, suggesting continuing declines in sagebrush ecosystems. One limitation of these R&R projections was relatively novel future climatic conditions in particularly hot and dry areas that were underrepresented in the training data. Including more data from these areas in future updates could further improve the reliability of the projections. Overall, these projected future declines in R&R highlight a growing challenge for natural resource managers in the region, and the resulting spatially explicit datasets provide information that can improve long-term risk assessments, prioritizations, and climate adaptation efforts.

western United States↗
USGS2013

Potential increases in natural disturbance rates could offset forest management impacts on ecosystem carbon stocks

Forested ecosystems contain the majority of the world’s terrestrial carbon, and forest management has implications for regional and global carbon cycling. Carbon stored in forests changes with stand age and is affected by natural disturbance and timber harvesting. We examined how harvesting and disturbance interact to influence forest carbon stocks over the Superior National Forest, in northern Minnesota. Forest inventory data from the USDA Forest Service, Forest Inventory and Analysis program were used to characterize current forest age structure and quantify the relationship between age and carbon stocks for eight forest types. Using these findings, we simulated the impact of alternative management scenarios and natural disturbance rates on forest-wide terrestrial carbon stocks over a 100-year horizon. Under low natural mortality, forest-wide total ecosystem carbon stocks increased when 0% or 40% of planned harvests were implemented; however, the majority of forest-wide carbon stocks decreased with greater harvest levels and elevated disturbance rates. Our results suggest that natural disturbance has the potential to exert stronger influence on forest carbon stocks than timber harvesting activities and that maintaining carbon stocks over the long-term may prove difficult if disturbance frequency increases in response to climate change.

Minnesota↗
USGS2015

The source, discharge, and chemical characteristics of selected springs, and the abundance and health of associated endemic anuran species in the Mojave network parks

Hydrological and biological investigations were done during 2005 and 2006 in cooperation with the U.S. National Park Service to investigate the source, discharge, and chemical characteristics of selected springs and the abundance and health of endemic anuran (frog and toad) species at Darwin Falls in Death Valley National Park, Piute Spring in Mojave National Preserve, and Fortynine Palms Oasis in Joshua Tree National Park. Discharge from the springs at these sites sustains isolated riparian habitats in the normally dry Mojave Desert. Data were collected on water quantity (discharge) and quality, air and water temperature, and abundance and health of endemic anuran species. In addition, a single survey of the abundance and health of endemic anuran species was completed at Rattlesnake Canyon in Joshua Tree National Park. Results from this study were compared to limited historical data, where they exist, and can provide a baseline for future hydrological and biological investigations to evaluate the health and sustainability of the resource and its response to changing climate and increasing human use. Radiocarbon dating of the water yielded estimated ages of about 7,000 years at Piute Spring and about 3,000 years at Darwin Spring, and tritium-helium-3 dating indicated an age of less than 2 years at Fortynine Palms Oasis. Stable hydrogen-isotope ratios were used to interpret an average altitude of recharge of 2,348 meters for Darwin Spring (about 1,415 meters higher than the altitude of Darwin Spring), 1,668 meters for Piute Spring (about 766 meters higher than the altitude of Piute Spring), and 1,400 meters for the Upper Pool at Fortynine Palms Oasis (about 543 meters higher than the altitude of the Upper Pool). Water-quality data collected for this study did not appear to be sensitive to trends in precipitation or seasonality in the Darwin Falls and Piute Spring study areas; however, it was sensitive to trends in Fortynine Palms Oasis where salinity increased by more than 10 percent during the 2 years of this study. Such a rapid response is consistent with the comparatively short travel time of less than 2 years from recharge to discharge at Fortynine Palms Oasis. Of the 14 trace elements analyzed, only concentrations of uranium at Fortynine Palms Oasis and arsenic at Darwin Spring were above drinking water standards; both constituents are derived from natural sources in the drainage basin and, therefore, are likely to have accumulated as a result of natural processes. Endemic anuran species were surveyed at Darwin Falls for the western toad ( Anaxyrus boreas ) and the red-spotted toad ( Anaxyrus punctatus ), at Piute Spring for the red-spotted toad, and at Fortynine Palms Oasis for the red-spotted toad and California treefrog ( Pseudacris cadaverina ). Historically, red-spotted toads were at the edge of their range at Darwin Falls, but they were not detected during this study and have not been detected since the early 1980s. The 2006 western toad population at Darwin Falls was estimated at 381 adults (95-percent confidence interval [CI] of 314–482). The population of red-spotted toads at Piute Spring was estimated at 1,153 adults (95-percent CI of 935–1,503). However, an elevated rate of abnormalities (approximately 5 percent) was recorded in red-spotted toads as well as the presence of the chytrid fungus, Bactrochochytrium dendrobatidis , at Piute Spring. In Joshua Tree National Park, the California treefrog now occupies only three of the seven historically occupied drainages. Populations of California treefrogs at Fortynine Palms Oasis have declined more than 50 percent from 288 in 1969–71 to 109 in 2006. A similar decline was observed in the populations of red-spotted toads at Fortynine Palms Oasis from 300 adults in 1969–71 to 155 adults (95-percent CI of 90–139) in 2006. The red-spotted toads at Fortynine Palms Oasis also exhibited the presence of Bactrochochytrium dendrobatidis .

California↗
USGS2014

Photoperiod control of downstream movements of Atlantic salmon Salmo salar smolts

This study provides the first direct observations that photoperiod controls the initiation of downstream movement in Atlantic salmon Salmo salar smolts. Under simulated natural day length (LDN) conditions and seasonal increases in temperature, smolts increased their downstream movements five-fold for a period of 1 month in late spring. Under the same conditions, parr did not show changes in downstream movement behaviour. When given a shortened day length (10L:14D) beginning in late winter, smolts did not increase the number of downstream movements. An early increase in day length (16L:8D) in late winter resulted in earlier initiation and termination of downstream movements compared to the LDN group. Physiological status and behaviour were related but not completely coincident: gill Na + /K + -ATPase activity increased in all treatments and thyroid hormone was elevated prior to movement in 16L:8D treatment. The most parsimonious model describing downstream movement of smolts included synergistic effects of photoperiod treatment and temperature, indicating that peak movements occurred at colder temperatures in the 16L:8D treatment than in LDN, and temperature did not influence movement of smolts in the 10L:14D treatment. The complicated interactions of photoperiod and temperature are not surprising since many organisms have evolved to rely on correlations among environmental cues and windows of opportunity to time behaviours associated with life-history transitions. These complicated interactions, however, have serious implications for phenological adjustments and persistence of S . salar populations in response to climate change.

Journal of Fish Biology↗
USGS2019

Assessing rangeland health under climate variability and change

RANGELAND HEALTH IN A CHANGING WORLD Rangeland health is an integrated metric that describes a complex suite of ecosystem properties and processes as applied to resource management. While the concept of “healthy” landscapes has a long history, the term “rangeland health” was codified in the US in 1994 as part of an effort to move towards a national, data driven, rangeland condition assessment (National Research Council 1994). Rangeland health encompasses the status of both soils and ecological processes as well as the condition of those ecosystems relative to ecological thresholds (e.g. “healthy”, “at-risk”, or “unhealthy"; National Research Council 1994). This latter application ensures that rangeland health assessments not only evaluate the conditions of plants and soils, but also gauge those conditions with respect to known or hypothesized ecological dynamics (Bestelmeyer et al. 2013) for a given set of abiotic constraints (climate, soil, and topographic setting). Thus, an assessment of rangeland health should identify the “degree to which the integrity of the soil and the ecological processes are sustained” (National Research Council 1994, Us Department of Agriculture 1997). Rangeland health attributes and assessment procedures have become widely utilized tools for measuring and monitoring dryland ecosystems, and they may provide valuable perspectives on rangeland response to climate change, although long-term directional change in environmental conditions represents a challenge for traditional rangeland health assessment frameworks.

Book chapter↗