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At least 667 records · Page 37Linked to original sources
USGS2024

Climate change scenarios for air and water temperatures in the upper San Francisco Estuary: Implications for thermal regimes and Delta Smelt

Climate projections and their effects in the San Francisco Estuary have been evaluated as part of the US Geological Survey’s CASCaDE2 project. Understanding the ecological effects of climate change can help manage and maintain the ecological health and productivity of the San Francisco Estuary. In this study, we assessed downscaled air temperature data from 10 global climate models (GCMs) under two representative concentration pathway (RCP) trajectories for greenhouse gas concentrations for three regions of the San Francisco Estuary: Sacramento–San Joaquin Delta, Suisun and Grizzly bays, and Suisun Marsh. We also used previously derived regression models to estimate future water temperatures at 16 locations in the upper San Francisco Estuary. We used a thermal regime approach to summarize water temperature projections to investigate changes to the thermal regime of the upper San Francisco Estuary, and used the Delta Smelt (Hypomesus transpacificus) to demonstrate the effects that a warming climate may have on the habitat needs of this fish species. Our results suggested there were no major differences in the extent of air-temperature warming among the three regions. Annual average air temperatures were projected to increase approximately 2.0 °C and 4.7 °C by the end of the century for the low and high RCP scenarios, respectively. We found timing, frequency, and magnitude metrics varied by period and RCP scenario, while duration and variability metrics varied by space for water-temperature thermal regimes. For example, the spawning window for Delta Smelt (thermal-regime duration metric) is projected to expand in the future, with spawning starting earlier for both RCP scenarios for most sites. Although our thermal-regime analysis focused on the life history of Delta Smelt, similar approaches could be used to assess climate-change threats to a wide array of native and invasive terrestrial and aquatic species found in San Francisco Estuary.

California↗
USGS2012

The interactive effects of excess reactive nitrogen and climate change on aquatic ecosystems and water resources of the United States

Nearly all freshwaters and coastal zones of the US are degraded from inputs of excess reactive nitrogen (Nr), sources of which are runoff, atmospheric N deposition, and imported food and feed. Some major adverse effects include harmful algal blooms, hypoxia of fresh and coastal waters, ocean acidification, long-term harm to human health, and increased emissions of greenhouse gases. Nitrogen fluxes to coastal areas and emissions of nitrous oxide from waters have increased in response to N inputs. Denitrification and sedimentation of organic N to sediments are important processes that divert N from downstream transport. Aquatic ecosystems are particularly important denitrification hotspots. Carbon storage in sediments is enhanced by Nr, but whether carbon is permanently buried is unknown. The effect of climate change on N transport and processing in fresh and coastal waters will be felt most strongly through changes to the hydrologic cycle, whereas N loading is mostly climate-independent. Alterations in precipitation amount and dynamics will alter runoff, thereby influencing both rates of Nr inputs to aquatic ecosystems and groundwater and the water residence times that affect Nr removal within aquatic systems. Both infrastructure and climate change alter the landscape connectivity and hydrologic residence time that are essential to denitrification. While Nr inputs to and removal rates from aquatic systems are influenced by climate and management, reduction of N inputs from their source will be the most effective means to prevent or to minimize environmental and economic impacts of excess Nr to the nation’s water resources.

Biogeochemistry↗
USGS1993

The magnitude and rapidity of the climate change marking the end of the Pleistocene in the mid-latitudes of South America

The chi-squared test of independence and cluster analysis of Otsuka similarity coefficients of fossil beetle assemblages from the Chilean Lake Region in the mid-latitudes of South America support the following conclusions: (1) the mean summer temperature of the glacial climate was 4-5??C lower than today's climate; (2) the climatic change from glacial to interglacial mode was in a single step centered on about 14,000 yr B.P.; (3) the climatic change was rapid, and within 1500 years the biota of a moorland had been completely replaced by a biota of a rain forest; (4) by 12,500 yr B.P., the low elevation beetle fauna of the Chilean Lake Region was similar in composition to that of the present day; and (5) no reversal in the postglacial warming trend, equivalent in age to the Younger Dryas Stade, was detected.

Chilean Lake Region↗
USGS2014

Management and monitoring of the endangered Shenandoah salamander under climate change: Workshop report 10-12 April 2012

Here we report on a structured decision making (SDM) process to identify management strategies to ensure persistence of the federally endangered Shenandoah salamander (Plethodon shenandoah), given that it may be at increased extinction risk under projected climate change. The focus of this report is the second of two SDM workshops; in the first workshop, participants developed a prototype of the decision, including problem frame, management objectives and a suite of potential management strategies, predictive models to inform the decision and link alternatives with the objectives to identify potential solutions, and identified data needs to reduce key uncertainties in the decision. Participants in this second workshop included experts in National Park Service policy at multiple administrative levels, who refined objectives, further evaluated the initial management alternatives, and discussed policy constraints on implementing active management for the species and its high-elevation habitat. The conclusion of the second workshop was similar to that of the first: the current state of information and objectives suggest that there is some value in considering active management to reduce the long-term extinction risk for the species, though there are institutional conservative policies to implementing active management at range-wide scales. The workshop participants also emphasized a conservative NPS management philosophy, including caution in implementing management actions that may ultimately harm the system, a stated assumption that ecosystem changes were “natural” unless demonstrated otherwise (therefore not warranting active management to mitigate), and a need to demonstrate that extinction risk is tied to anthropogenic influence prior to taking active management to mitigate specific anthropogenic influences. Even within a protected area having minimal human disturbance, intertwined environmental variables and interspecific relationships that drive population trends challenge our ability to demonstrate direct links with (anthropogenically influenced) climate change and the decline of a species. Thus while this policy may reduce the potential for injurious management, it may also necessitate extraordinary resources to reduce uncertainty regarding fundamental drivers of species decline prior to taking action.

Natural Resource Report↗
USGS2016

Climate change and future fire regimes: Examples from California

Climate and weather have long been noted as playing key roles in wildfire activity, and global warming is expected to exacerbate fire impacts on natural and urban ecosystems. Predicting future fire regimes requires an understanding of how temperature and precipitation interact to control fire activity. Inevitably this requires historical analyses that relate annual burning to climate variation. Fuel structure plays a critical role in determining which climatic parameters are most influential on fire activity, and here, by focusing on the diversity of ecosystems in California, we illustrate some principles that need to be recognized in predicting future fire regimes. Spatial scale of analysis is important in that large heterogeneous landscapes may not fully capture accurate relationships between climate and fires. Within climatically homogeneous subregions, montane forested landscapes show strong relationships between annual fluctuations in temperature and precipitation with area burned; however, this is strongly seasonal dependent; e.g., winter temperatures have very little or no effect but spring and summer temperatures are critical. Climate models that predict future seasonal temperature changes are needed to improve fire regime projections. Climate does not appear to be a major determinant of fire activity on all landscapes. Lower elevations and lower latitudes show little or no increase in fire activity with hotter and drier conditions. On these landscapes climate is not usually limiting to fires but these vegetation types are ignition-limited. Moreover, because they are closely juxtaposed with human habitations, fire regimes are more strongly controlled by other direct anthropogenic impacts. Predicting future fire regimes is not rocket science; it is far more complicated than that. Climate change is not relevant to some landscapes, but where climate is relevant, the relationship will change due to direct climate effects on vegetation trajectories, as well as by feedback processes of fire effects on vegetation distribution, plus policy changes in how we manage ecosystems.

Geoscience Canada↗
USGS2023

Adapting to climate change on desert rangelands: A multi-site comparison of grazing behavior plasticity of heritage and improved beef cattle

Climate change is amplifying the spatiotemporal heterogeneity of desert rangeland forages through its impact on precipitation variability. Foraging behavior plasticity (an animal's ability to alter its behavior to cope with environmental variation) could be a key trait for climate adaptation of beef cattle in arid environments. We analyzed GPS-derived movement and activity data of Criollo and commercial beef cattle from eight studies conducted at sites in North and South America to determine whether seasonal and year-to-year behavior plasticity varied significantly between breeds. We calculated dormant/brown season or driest year percent change in foraging behavior relative to growing/green season or wettest year. Compared to commercial beef breeds, Criollo cattle exhibited significantly greater seasonal adjustment in daily distance traveled (20% increase vs. 2% decrease, P ≤ 0.02) and daily grazing effort (25% vs. 1.5% increase, P = 0.01) during the dormant/brown vs. growing/green season. Increase in daily area explored during the dormant/brown season was almost three times greater in Criollo vs. commercial beef cattle (P = 0.09). Seasonal adjustment in daily time spent grazing was similar for Criollo and commercial beef breeds. Increase in daily area explored during the dormant/brown season of dry vs. wet years was three times greater for Criollo vs. commercial beef breeds (P = 0.03). Criollo cattle tended (P = 0.09) to exhibit greater behavior adjustment than commercial beef counterparts in daily distance traveled during the dormant/brown season of dry vs. wet years (22% vs. 4% increase, respectively). No breed differences in adjustment of time spent grazing (P = 0.36) or grazing effort (P = 0.20) during dormant/brown season of dry vs. wet years were observed. Dry vs. wet year grazing behavior adjustments during the growing/green season were similar for both breeds. Grazing behavior plasticity observed in Criollo cows could be a critical trait for desert beef herds in the face of increasingly variable rainfall patterns occurring as a result of climate change.

Journal of Arid Environments↗
USGS2022

Understanding local adaptation to prepare populations for climate change

Adaptation within species to local environments is widespread in nature. Better understanding this local adaptation is critical to conserving biodiversity. However, conservation practices can rely on species’ trait averages or can broadly assume homogeneity across the range to inform management. Recent methodological advances for studying local adaptation provide the opportunity to fine-tune efforts for managing and conserving species. The implementation of these advances will allow us to better identify populations at greatest risk of decline because of climate change, as well as highlighting possible strategies for improving the likelihood of population persistence amid climate change. In the present article, we review recent advances in the study of local adaptation and highlight ways these tools can be applied in conservation efforts. Cutting-edge tools are available to help better identify and characterize local adaptation. Indeed, increased incorporation of local adaptation in management decisions may help meet the imminent demands of managing species amid a rapidly changing world.

BioScience↗
USGS2012

Climate change has indirect effects on resource use and overlap among coexisting bird species with negative consequences for their reproductive success

Climate change can modify ecological interactions, but whether it can have cascading effects throughout ecological networks of multiple interacting species remains poorly studied. Climate-driven alterations in the intensity of plant–herbivore interactions may have particularly profound effects on the larger community because plants provide habitat for a wide diversity of organisms. Here we show that changes in vegetation over the last 21 years, due to climate effects on plant–herbivore interactions, have consequences for songbird nest site overlap and breeding success. Browsing-induced reductions in the availability of preferred nesting sites for two of three ground nesting songbirds led to increasing overlap in nest site characteristics among all three bird species with increasingly negative consequences for reproductive success over the long term. These results demonstrate that changes in the vegetation community from effects of climate change on plant–herbivore interactions can cause subtle shifts in ecological interactions that have critical demographic ramifications for other species in the larger community.

Global Change Biology↗
USGS2022

Using landscape genomics to delineate future adaptive potential for climate change in the Yosemite toad (Anaxyrus canorus)

An essential goal in conservation biology is delineating population units that maximize the probability of species persisting into the future and adapting to future environmental change. However, future-facing conservation concerns are often addressed using retrospective patterns that could be irrelevant. We recommend a novel landscape genomics framework for delineating future “Geminate Evolutionary Units” (GEUs) in a focal species: (1) identify loci under environmental selection, (2) model and map adaptive conservation units that may spawn future lineages, (3) forecast relative selection pressures on each future lineage, and (4) estimate their fitness and likelihood of persistence using geo-genomic simulations. Using this process, we delineated conservation units for the Yosemite toad ( Anaxyrus canorus ), a U.S. federally threatened species that is highly vulnerable to climate change. We used a genome-wide dataset, redundancy analysis, and Bayesian association methods to identify 24 candidate loci responding to climatic selection ( R 2 ranging from 0.09 to 0.52), after controlling for demographic structure. Candidate loci included genes such as MAP3K5, involved in cellular response to environmental change. We then forecasted future genomic response to climate change using the multivariate machine learning algorithm Gradient Forests. Based on all available evidence, we found three GEUs in Yosemite National Park, reflecting contrasting adaptive optima: YF-North (high winter snowpack with moderate summer rainfall), YF-East (low to moderate snowpack with high summer rainfall), and YF-Low-Elevation (low snowpack and rainfall). Simulations under the RCP 8.5 climate change scenario suggest that the species will decline by 29% over 90 years, but the highly diverse YF-East lineage will be least impacted for two reasons: (1) geographically it will be sheltered from the largest climatic selection pressures, and (2) its standing genetic diversity will promote a faster adaptive response. Our approach provides a comprehensive strategy for protecting imperiled non-model species with genomic data alone and has wide applicability to other declining species.

California↗
USGS2026

Climate change and water quality influence on juvenile Atlantic sturgeon aggregation in the Altamaha River, Georgia

In the summer, juvenile Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus ) are vulnerable to extreme water quality conditions (i.e., temperature, dissolved oxygen [DO], and salinity) in the estuaries they inhabit. The effects of climate change on Atlantic sturgeon are largely unknown, but it may exacerbate these water quality issues. We used a 20-year dataset from the Altamaha River estuary, Georgia, USA to fit negative binomial mixed-effects models describing the relationship between water quality and catch per net hour of juvenile Atlantic sturgeon. Water temperature and DO were significant positive predictors of catch; salinity and sampling year were significant negative predictors. The interaction between temperature and DO was also significant. Water temperature, salinity, and year were significant in explaining variability in catch. Our modeling results suggest that response to water quality depends on fish age. Next, we used global climate projections to construct future climate scenarios incorporating warming water and increased salinity. By coupling these predictions with catch models, we forecast juvenile Atlantic sturgeon catch as a proxy for distribution. Water temperature increases of 1–5 °C led to predicted catch increases of 5–24%, although this result may be influenced by aggregation behavior or sampling limitations at high temperatures. Salinity increases of 1–2 ppt led to 9–17% decreases in catch, suggesting that saltwater intrusion may limit future Atlantic sturgeon estuarine habitat availability. Our study combines a long-term dataset with a robust statistical modeling approach to offer some of the first insights into future climate change effects on juvenile Atlantic sturgeon’s southern nursery habitats.

Georgia↗
USGS2003

Timing of autumn bird migration under climate change: advances in long–distance migrants, delays in short–distance migrants

As a response to increasing spring temperature in temperate regions in recent years, populations of many plant and animal species, including migratory birds, have advanced the seasonal start of their reproduction or growth. However, the effects of climate changes on subsequent events of the annual cycle remain poorly understood. We investigated long–term changes in the timing of autumn migration in birds, a key event in the annual cycle limiting the reproductive period. Using data spanning a 42–year period, we analysed long–term changes in the passage of 65 species of migratory birds through Western Europe. The autumn passage of migrants wintering south of the Sahara has advanced in recent years, presumably as a result of selection pressure to cross the Sahel before its seasonal dry period. In contrast, migrants wintering north of the Sahara have delayed autumn passage. In addition, species with a variable rather than a fixed number of broods per year have delayed passage, possibly because they are free to attempt more broods. Recent climate changes seem to have a simple unidirectional effect on the seasonal onset of reproduction, but complex and opposing effects on the timing of subsequent events in the annual cycle, depending on the ecology and life history of a species. This complicates predictions of overall effects of global warming on avian communities.

Proceedings of the Royal Society B: Biological Sci↗
USGS2019

Climate change, coral loss, and the curious case of the parrotfish paradigm: Why don't marine protected areas improve reef resilience?

Scientists have advocated for local interventions, such as creating marine protected areas and implementing fishery restrictions, as ways to mitigate local stressors to limit the effects of climate change on reef-building corals. However, in a literature review, we find little empirical support for the notion of managed resilience. We outline some reasons for why marine protected areas and the protection of herbivorous fish (especially parrotfish) have had little effect on coral resilience. One key explanation is that the impacts of local stressors (e.g., pollution and fishing) are often swamped by the much greater effect of ocean warming on corals. Another is the sheer complexity (including numerous context dependencies) of the five cascading links assumed by the managed-resilience hypothesis. If reefs cannot be saved by local actions alone, then it is time to face reef degradation head-on, by directly addressing anthropogenic climate change—the root cause of global coral decline.

Annual Review of Marine Science↗
USGS2017

Model-based scenario planning to inform climate change adaptation in the Northern Great Plains—Final report

Public Summary We worked with managers in two focal areas to plan for the uncertain future by integrating quantitative climate change scenarios and simulation modeling into scenario planning exercises. In our central North Dakota focal area, centered on Knife River Indian Villages National Historic Site, managers are concerned about how changes in flood severity and growing conditions for native and invasive plants may affect archaeological resources and cultural landscapes associated with the Knife and Missouri Rivers. Climate projections and hydrological modeling based on those projections indicate plausible changes in spring and summer soil moisture ranging from a 7 percent decrease to a 13 percent increase and maximum winter snowpack (important for spring flooding) changes ranging from a 13 percent decrease to a 47 percent increase. Facilitated discussions among managers and scientists exploring the implications of these different climate scenarios for resource management revealed potential conflicts between protecting archeological sites and fostering riparian cottonwood forests. The discussions also indicated the need to prioritize archeological sites for excavation or protection and culturally important plant species for intensive management attention. In our southwestern South Dakota focal area, centered on Badlands National Park, managers are concerned about how changing climate will affect vegetation production, wildlife populations, and erosion of fossils, archeological artifacts, and roads. Climate scenarios explored by managers and scientists in this focal area ranged from a 13 percent decrease to a 33 percent increase in spring precipitation, which is critical to plant growth in the northern Great Plains region, and a slight decrease to a near doubling of intense rain events. Facilitated discussions in this focal area concluded that greater effort should be put into preparing for emergency protection, excavation, and preservation of exposed fossils or artifacts and revealed substantial opportunities for different agencies to learn from each other and cooperate on common management goals. Follow up quantitative simulation modeling of grassland dynamics helped quantify the degree of change expected in vegetation production under the wide range of climate scenarios and suggested that (a) low grazing rates could be adversely affecting vegetation composition in the national park and (b) understanding of the management practices needed to maintain desired vegetation conditions is incomplete.

Montana, Nebraska, North Dakota, South Dakota, Wyo↗
USGS2023

Characterizing changes in the 1-percent annual exceedance probability streamflows for climate-change scenarios in the Housatonic River watershed of Massachusetts, Connecticut, and New York

Current methods for determining the 1-percent annual exceedance probability (AEP) for a streamflow assume stationarity (the assumption that the statistical distribution of data from past observations does not contain trends and will continue unchanged in the future). This assumption allows the 1-percent AEP to be determined based on historical streamflow records. However, the assumption of stationarity is challenged by observed trends in streamflow records. In response, the U.S. Geological Survey, in cooperation with the Federal Emergency Management Agency, studied potential changes to the 1-percent AEP streamflows at streamgages in the Housatonic River watershed in Massachusetts, Connecticut, and New York. The study used the Precipitation-Runoff Modeling System—a deterministic hydrologic model. Climate inputs to the model of temperature and precipitation were scaled to anticipated changes based on global climate models that could occur in 2030, 2050, and 2100. The model outputs were used to characterize the 1-percent AEP streamflows for 2030, 2050, and 2100 and compare the results to baseline conditions for 1950 to 2015. Results indicated that the 1-percent AEP streamflow for unregulated streams and rivers may increase from the 1950–2015 baseline period by 7.4, 11.7, and 17.3 percent in 2030, 2050, and 2100, respectively, because of climate change.

Connecticut, Massachusetts, New York↗
USGS2015

Many atolls may be uninhabitable within decades due to climate change

Observations show global sea level is rising due to climate change, with the highest rates in the tropical Pacific Ocean where many of the world’s low-lying atolls are located. Sea-level rise is particularly critical for low-lying carbonate reef-lined atoll islands; these islands have limited land and water available for human habitation, water and food sources, and ecosystems that are vulnerable to inundation from sea-level rise. Here we demonstrate that sea-level rise will result in larger waves and higher wave-driven water levels along atoll islands’ shorelines than at present. Numerical model results reveal waves will synergistically interact with sea-level rise, causing twice as much land forecast to be flooded for a given value of sea-level rise than currently predicted by current models that do not take wave-driven water levels into account. Atolls with islands close to the shallow reef crest are more likely to be subjected to greater wave-induced run-up and flooding due to sea-level rise than those with deeper reef crests farther from the islands’ shorelines. It appears that many atoll islands will be flooded annually, salinizing the limited freshwater resources and thus likely forcing inhabitants to abandon their islands in decades, not centuries, as previously thought.

Hawaii↗
USGS2022

Conservation under uncertainty: Innovations in participatory climate change scenario planning from U.S. national parks

The impacts of climate change (CC) on natural and cultural resources are far-reaching and complex. A major challenge facing resource managers is not knowing the exact timing and nature of those impacts. To confront this problem, scientists, adaptation specialists, and resource managers have begun to use scenario planning (SP). This structured process identifies a small set of scenarios—descriptions of potential future conditions that encompass the range of critical uncertainties—and uses them to inform planning. We reflect on a series of five recent participatory CC SP projects at four US National Park Service units and derive guidelines for using CC SP to support natural and cultural resource conservation. Specifically, we describe how these engagements affected management, present a generalized CC SP approach grounded in management priorities, and share key insights and innovations that (1) fostered participant confidence and deep engagement in the participatory CC SP process, (2) shared technical information in a way that encouraged informed, effective participation, (3) contextualized CC SP in the broader picture of relevant longstanding or emerging nonclimate stressors, (4) incorporated quantitative approaches to expand analytical capacity and assess qualitative findings, and (5) translated scenarios and all their complexity into strategic action.

Conservation Science and Practice↗
USGS2016

A case study on evaluating impacts of potential climate change on groundwater resources: Groundwater recharge in the Upper Colorado River Basin

An investigation of the change in groundwater recharge in response to potential climate change was performed for the UCRB using the SWB groundwater recharge model and downscaled climate data from the CMIP5 multi-model dataset. Climate projections from 97 downscaled CMIP5 datasets were assumed to be equally likely and recharge simulation results were combined. Results for the UCRB suggest that projected increases in actual ET from higher temperatures may be offset by increases in precipitation, resulting in increased groundwater recharge for many areas in the basin in future time periods.

Arizona, Colorado, New Mexico, Utah↗
USGS1999

Socioeconomic impacts of climate change on U.S. water supplies

A greenhouse warming would have major effects on water supplies and demands. A framework for examining the socioeconomic impacts associated with changes in the long-term availability of water is developed and applied to the hydrologic implications of the Canadian and British Hadley2 general circulation models (GCMs) for the 18 water resource regions in the conterminous United States. The climate projections of these two GCMs have very different implications for future water supplies and costs. The Canadian model suggests most of the nation would be much drier in the year 2030. Under the least-cost management scenario the drier climate could add nearly $105 billion to the estimated costs of balancing supplies and demands relative to the costs without climate change. Measures to protect instream flows and irrigation could result in significantly higher costs. In contrast, projections based on the Hadley model suggest water supplies would increase throughout much of the nation, reducing the costs of balancing water supplies with demands relative to the no-climate-change case.

Conference Paper↗