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At least 541 records · Page 30Linked to original sources
USGS2016

Vulnerability and adaptation to climate-related fire impacts in rural and urban interior Alaska

This paper explores whether fundamental differences exist between urban and rural vulnerability to climate-induced changes in the fire regime of interior Alaska. We further examine how communities and fire managers have responded to these changes and what additional adaptations could be put in place. We engage a variety of social science methods, including demographic analysis, semi-structured interviews, surveys, workshops and observations of public meetings. This work is part of an interdisciplinary study of feedback and interactions between climate, vegetation, fire and human components of the Boreal forest social–ecological system of interior Alaska. We have learned that although urban and rural communities in interior Alaska face similar increased exposure to wildfire as a result of climate change, important differences exist in their sensitivity to these biophysical, climate-induced changes. In particular, reliance on wild foods, delayed suppression response, financial resources and institutional connections vary between urban and rural communities. These differences depend largely on social, economic and institutional factors, and are not necessarily related to biophysical climate impacts per se. Fire management and suppression action motivated by political, economic or other pressures can serve as unintentional or indirect adaptation to climate change. However, this indirect response alone may not sufficiently reduce vulnerability to a changing fire regime. More deliberate and strategic responses may be required, given the magnitude of the expected climate change and the likelihood of an intensification of the fire regime in interior Alaska.

Alaska↗
USGS2018

Longevity and population age structure of the arroyo southwestern toad (Anaxyrus californicus) with drought implications

The arroyo southwestern toad is a specialized and federally endangered amphibian endemic to the coastal plains and mountains of central and southern California and northwestern Baja California. It is largely unknown how long these toads live in natural systems, how their population demographics vary across occupied drainages, and how hydrology affects age structure. We used skeletochronology to estimate the ages of adult arroyo toads in seven occupied drainages with varying surface water hydrology in southern California. We processed 179 adult toads with age estimates between 1 and 6 years. Comparisons between skeletochronological ages and known ages of PIT tagged toads showed that skeletochronology likely underestimated toad age by up to 2 years, indicating they may live to 7 or 8 years, but nonetheless major patterns were evident. Arroyo toads showed sexual size dimorphism with adult females reaching a maximum size of 12 mm greater than males. Population age structure varied among the sites. Age structure at sites with seasonally predictable surface water was biased toward younger individuals, which indicated stable recruitment for these populations. Age structures at the ephemeral sites were biased toward older individuals with cohorts roughly corresponding to higher rainfall years. These populations are driven by surface water availability, a stochastic process, and thus more unstable. Based on our estimates of toad ages, climate predictions of extreme and prolonged drought events could mean that the number of consecutive dry years could surpass the maximum life span of toads making them vulnerable to extirpation, especially in ephemeral freshwater systems. Understanding the relationship between population demographics and hydrology is essential for predicting species resilience to projected changes in weather and rainfall patterns. The arroyo toad serves as a model for understanding potential responses to climatic and hydrologic changes in Mediterranean stream systems. We recommend development of adaptive management strategies to address these threats.

California↗
USGS2004

Global climate change and wildlife in North America

It is widely accepted by the scientific community that the earth, which has always experienced climate variation, is now undergoing a period of rapid climate change that is enhanced by anthropogenic atmospheric carbon enrichment during the past 100 years. These climatic changes are accelerating and projections for the next 100 years indicate extensive warming in most (but not all) areas, changing patterns of precipitation, and a significant acceleration of sea level rise. Other likely components of ongoing climate change include changes in season lengths, decreasing range of nighttime versus daytime temperatures, declining snowpack, and increasing frequency and intensity of severe weather events. The many components of climate change, and especially the unprecedented rapid rate of change, are just as important as increasing temperatures. Wildlife species are closely adapted to their environments and readily respond to climate variation. However, as discussed in this technical review, the climate change now underway has extensive potential to affect wildlife throughout North America, either directly or indirectly through responses to changing habitat conditions. When considered in combination with other factors (e.g., pollution, ozone depletion, urbanization, etc.), the potential effect is even greater. The effects of climate change on populations and range distributions of wildlife are expected to be species specific and highly variable, with some effects considered negative and others considered positive. In North America the ranges of habitats and wildlife are predicted to generally move northward as temperatures increase. Variations in this overall pattern will be dependent upon specific local conditions, changing precipitation patterns, and the response of different species to different components of climate change. It follows that the structure of plant–animal communities will also change. Ignoring climate change is likely to increasingly result in failure to reach wildlife management objectives. Wildlife managers need to become knowledgeable about climate change, ways to cope with it, and ways to take advantage of it. Management options currently available include protecting coastal wetlands to allow for sea level rise, reducing the risks to wildlife from potential catastrophic events, adjusting yield and harvest models, accounting for known climatic variations, and taking climate change into consideration when selecting the location and other characteristics of conservation areas. Wildlife managers also need to expect the unexpected and reduce nonclimate stressors on ecosystems. Overall, wildlife managers can minimize negative impacts to wildlife and take advantage of positive aspects by planning ahead and employing adaptive management.

Technical Review↗
USGS2013

The National Climate Change and Wildlife Science Center annual report for 2012

Welcome to the inaugural edition of the U.S. Geological Survey (USGS) National Climate Change and Wildlife Science Center (NCCWSC) and the Department of the Interior (DOI) Climate Science Centers (CSCs) annual report. In 2008, Congress created the National Climate Change and Wildlife Science Center (NCCWSC) within the U.S. Geological Survey (USGS). The center was formed to respond to the demands of natural resource managers for rigorous scientific information and effective tools for assessing and responding to climate change. Located at the USGS National Headquarters in Reston, Va., the NCCWSC has invested more than $70 million in cutting-edge climate change research and, in response to Secretarial Order No. 3289,established and is managing eight regional Department of Interior (DOI) Climate Science Centers (CSCs). The mission of the NCCWSC is to provide natural resource managers with the tools and information they need to develop and execute management strategies that address the impacts of climate and other ongoing global changes on fish and wildlife and their habitats. The DOI CSCs are joint Federal-university partnerships that focus their scientific work on regional priorities identified by DOI Landscape Conservation Cooperatives (LCCs) as well as Federal, State, Tribal, and other resource managers. The CSCs provide access to a wide range of scientific capabilities through their network of university partners along with the USGS and other Federal agency scientists. The focus of the NCCWSC on multiregion and national priorities complements the regionally focused agendas of the CSCs.

Circular↗
USGS2017

Postglacial response of a stream in central Iowa to changes in climate and Drainage basin factors

Postglacial geomorphic development of the Buchanan Drainage, a small tributary to the South Skunk River, is reconstructed by documenting relationships among four allostratigraphic units and 17 radiocarbon dates. Formation and headward expansion of the valley was both episodic and time-transgressive. Response to downstream conditions in the South Skunk River largely controlled the early formation of the basin. Downcutting through Pleistocene deposits produced a gravelly lag deposit that was buried by alluvium in the downstream portion of the valley during the early Holocene (10,500-7700 yr B.P.). Lag deposits formed in a similar manner continued to develop in the upper portion of the drainageway into the late Holocene (3000-2000 yr B.P.). Episodes of aggradation during the middle Holocene (7700-6300 yr B.P.) and late Holocene (3000-2000 yr B.P.) were separated by a period of soil formation. Holocene geomorphic events in the drainageway coincide with some vegetational and climatic changes as documented in upland pollen sequences from central Iowa. Analysis of plant macrofossil assemblages recovered from alluvium indicates that during the middle Holocene forest contracted and prairie expanded into the uplands within the basin. Vegetational changes within the basin apparently had only minor influence on rates of hillslope erosion, and the widely accepted relationship between prairie (versus forest) vegetative cover and increased rates of hillslope erosion did not hold. Instead, greater amounts of erosion occurred under forested conditions when local water tables were higher and seepage erosion was more effective. ?? 1990.

Quaternary Research↗
USGS2023

Climate change and the global redistribution of biodiversity: Substantial variation in empirical support for expected range shifts

Background Among the most widely predicted climate change-related impacts to biodiversity are geographic range shifts, whereby species shift their spatial distribution to track their climate niches. A series of commonly articulated hypotheses have emerged in the scientific literature suggesting species are expected to shift their distributions to higher latitudes, greater elevations, and deeper depths in response to rising temperatures associated with climate change. Yet, many species are not demonstrating range shifts consistent with these expectations. Here, we evaluate the impact of anthropogenic climate change (specifically, changes in temperature and precipitation) on species’ ranges, and assess whether expected range shifts are supported by the body of empirical evidence. Methods We conducted a Systematic Review, searching online databases and search engines in English. Studies were screened in a two-stage process (title/abstract review, followed by full-text review) to evaluate whether they met a list of eligibility criteria. Data coding, extraction, and study validity assessment was completed by a team of trained reviewers and each entry was validated by at least one secondary reviewer. We used logistic regression models to assess whether the direction of shift supported common range-shift expectations (i.e., shifts to higher latitudes and elevations, and deeper depths). We also estimated the magnitude of shifts for the subset of available range-shift data expressed in distance per time (i.e., km/decade). We accounted for methodological attributes at the study level as potential sources of variation. This allowed us to answer two questions: (1) are most species shifting in the direction we expect (i.e., each observation is assessed as support/fail to support our expectation); and (2) what is the average speed of range shifts? Review findings We found that less than half of all range-shift observations (46.60%) documented shifts towards higher latitudes, higher elevations, and greater marine depths, demonstrating significant variation in the empirical evidence for general range shift expectations. For the subset of studies looking at range shift rates, we found that species demonstrated significant average shifts towards higher latitudes (average = 11.8 km/dec) and higher elevations (average = 9 m/dec), although we failed to find significant evidence for shifts to greater marine depths. We found that methodological factors in individual range-shift studies had a significant impact on the reported direction and magnitude of shifts. Finally, we identified important variation across dimensions of range shifts (e.g., greater support for latitude and elevation shifts than depth), parameters (e.g., leading edge shifts faster than trailing edge for latitude), and taxonomic groups (e.g., faster latitudinal shifts for insects than plants). Conclusions Despite growing evidence that species are shifting their ranges in response to climate change, substantial variation exists in the extent to which definitively empirical observations confirm these expectations. Even though on average, rates of shift show significant movement to higher elevations and latitudes for many taxa, most species are not shifting in expected directions. Variation across dimensions and parameters of range shifts, as well as differences across taxonomic groups and variation driven by methodological factors, should be considered when assessing overall confidence in range-shift hypotheses. In order for managers to effectively plan for species redistribution, we need to better account for and predict which species will shift and by how much. The dataset produced for this analysis can be used for future research to explore additional hypotheses to better understand species range shifts.

Journal of Environmental Evidence↗
USGS2019

Negative impacts of summer heat on Sierra Nevada tree seedlings

Understanding the response of forests to climate change is important for predicting changes in biodiversity and ecosystem services, including carbon storage. Seedlings represent a key demographic stage in these responses, because seedling establishment is necessary for population persistence and spread, and because the conditions allowing seedlings to survive and grow are often more restrictive than those adults can tolerate. However, detailed long‐term data on the responses of individual seedlings to climatic variation are rare. Here, we analyze a decade of seedling growth and survival data collected in 25 long‐term plots located in Sequoia and Yosemite National Parks. The forest types represented range from lower‐elevation mixed conifer, to red fir‐dominated, to high‐elevation western white pine stands. Twelve species, including two oaks and ten conifers, are found across these plots. Survival and transition to larger size classes are modeled within a Bayesian framework as a function of species, size, fire, and various climate variables. We initially expected that precipitation‐related variables would have a strong effect on seedling survival and growth in this Mediterranean‐climate region and that some species might respond positively to higher temperatures if they are adapted to warmer low‐elevation areas or to higher‐than‐average temperatures if they are high‐elevation species whose growing seasons are limited by cold. However, we found that higher July maximum temperature or temperature anomalies were associated with lower survival and growth for most species, while precipitation and snow effects were weaker and more variable. Higher precipitation had a positive effect on survival of most species, but snow effects and precipitation effects on growth could be negative. Given the estimated climate responses, under potential future scenarios of higher summer temperatures and altered precipitation, most species are predicted to have lower survival and reduced growth. This is likely to favor species that have relatively high survival and growth and less negative responses to climatic shift (such as several of the pines) and perhaps lead to a more open forest structure—or potentially transition to non‐forest vegetation types where seedling recruitment does not keep pace with adult mortality.

California↗
USGS2023

Vulnerability and resilience of ice-rich permafrost to thermal erosion gullying in the Arctic Foothills infrastructure corridor, Alaska

The Arctic and its permafrost terrains are inherently dynamic, complex, and sensitive environments. Understanding the past and current changes occurring in these systems is key in predicting future variations, including the response of permafrost to climate change and to surface disturbances resulting from natural processes or anthropogenic activities. Here, we focus on advancing our understanding of the drivers controlling terrain vulnerability and resilience to thermal erosion gullying proximal to linear infrastructure in the lowlands of the Arctic Foothills (Alaska). This builds upon our previous work (Stephani et al. 2023) in the infrastructure corridor that includes the Dalton Highway and Trans Alaska Pipeline System (TAPS). To identify locations affected by thermal erosion gullying and recognize changes in the ~80-km long corridor section that travels through the Arctic Foothills, we compared time series of high-resolution satellite imagery from 2001 to 2023. When we captured the timing of gullying onset and/or growth, we examined prevailing climatic conditions (Sagwon Station) prior to these terrain changes. We integrated our findings with our field-based data (e.g., drilling) described in Stephani et al. (2023).

Alaska↗
USGS2017

Nitrogenase activity by biological soil crusts in cold sagebrush steppe ecosystems

In drylands worldwide, biological soil crusts (BSC) form a thin photosynthetic cover across landscapes, and provide vital benefits in terms of stabilizing soil and fixing nitrogen (N) and carbon (C). Numerous studies have examined the effects of climate and disturbance on BSC functions; however, few have characterized these responses in rolling BSCs typical of northern ecosystems in the Intermountain West, US. With temperature increases and shifts in precipitation projected, it is unclear how BSCs in this region will respond to climate change, and how the response could affect their capacity to perform key ecosystem functions, such as providing ‘new’ N through biological N 2 fixation. To address this important knowledge gap, we examined nitrogenase activity (NA) associated with rolling BSCs along a climatic gradient in southwestern Idaho, US, and quantified how acetylene reduction rates changed as a function of climate, grazing (using exclosures), and shrub-canopy association. Results show that warmer, drier climates at lower elevations hosted greater cover of late successional BSC communities (e.g., mosses and lichens), and higher NA compared with colder, wetter climates at higher elevations. Highest NA (0.5–29.3 µmol C 2 H 4 m −2 h −1 ) occurred during the early summer/spring, when water was more available than in late summer/autumn. Activity was strongly associated with soil characteristics including pH and ammonium concentrations suggesting these characteristics as potentially strong controls on NA in BSCs. The relationship between grazing and NA varied with elevation. Specifically, lower elevation sites had lower NA at grazed locations, whereas higher elevation sites had higher NA with grazing. At both low and high ends of the elevation gradient, shrub-canopy associated BSCs maintained two to three times higher NA compared to BSCs in the interspace among shrubs. Taken together, our findings indicate that the controls and rates of NA in BSCs vary seasonally and strongly with climate in the Intermountain West, and that drier springs are likely to influence rates of NA more than warmer summers.

Idaho↗
USGS2002

A census of marine life: Unknowable or just unknown?

As an introduction to the entire volume, this article outlines the relationships among the five elements of the Census of Marine Life (CoML) that create new knowledge: (1) The Ocean Biogeographic Information System (OBIS), a marine component of the Global Biodiversity Information Facility, links marine databases around the world to provide an Internet accessible, dynamic interface for comparing species-level, geo-referenced biodiversity data in relation to ocean habitats. The entire CoML field project data will be managed in and accessible through OBIS. (2) The History of Marine Animal Populations (HMAP) is a unique new synthesis of historical and biological research that will document marine biodiversity, globally, up to 500 years ago, before significant human impact, and store it in formats compatible with modern data in OBIS. (3) The Scientific Committee on Oceanic Research Working Group 118 monitors and recommends advanced marine technologies, ready to be routinely used in CoML field projects. (4) CoML Initial Field Projects develop and calibrate these technologies in selected regions to facilitate and accelerate global biodiversity research. As calibrated technologies and protocols are adopted in many regions, qualitative and quantitative biodiversity discoveries accumulate. (5) The Future of Marine Animal Populations (FMAP) program will insure that the data in OBIS are suitable for modeling and predicting changes in global biodiversity in response to fishing, pollution, and climate change challenges. It will make datasets available for hindcasting and forecasting analyses linked to physical ocean observations and assist in documenting the impacts of conservation efforts on sustainability.

Oceanologica Acta↗
USGS2014

Polygonal tundra geomorphological change in response to warming alters future CO2 and CH4 flux on the Barrow Peninsula

The landscape of the Barrow Peninsula in northern Alaska is thought to have formed over centuries to millennia, and is now dominated by ice-wedge polygonal tundra that spans drained thaw-lake basins and interstitial tundra. In nearby tundra regions, studies have identified a rapid increase in thermokarst formation (i.e., pits) over recent decades in response to climate warming, facilitating changes in polygonal tundra geomorphology. We assessed the future impact of 100 years of tundra geomorphic change on peak growing season carbon exchange in response to: (i) landscape succession associated with the thaw-lake cycle; and (ii) low, moderate, and extreme scenarios of thermokarst pit formation (10%, 30%, and 50%) reported for Alaskan arctic tundra sites. We developed a 30 × 30 m resolution tundra geomorphology map (overall accuracy:75%; Kappa:0.69) for our ~1800 km² study area composed of ten classes; drained slope, high center polygon, flat-center polygon, low center polygon, coalescent low center polygon, polygon trough, meadow, ponds, rivers, and lakes, to determine their spatial distribution across the Barrow Peninsula. Land-atmosphere CO 2 and CH 4 flux data were collected for the summers of 2006–2010 at eighty-two sites near Barrow, across the mapped classes. The developed geomorphic map was used for the regional assessment of carbon flux. Results indicate (i) at present during peak growing season on the Barrow Peninsula, CO 2 uptake occurs at -902.3 10 6 gC-CO 2 day −1 (uncertainty using 95% CI is between −438.3 and −1366 10 6 gC-CO 2 day −1 ) and CH 4 flux at 28.9 10 6 gC-CH 4 day −1 (uncertainty using 95% CI is between 12.9 and 44.9 10 6 gC-CH 4 day −1 ), (ii) one century of future landscape change associated with the thaw-lake cycle only slightly alter CO 2 and CH 4 exchange, while (iii) moderate increases in thermokarst pits would strengthen both CO 2 uptake (−166.9 10 6 gC-CO 2 day −1 ) and CH 4 flux (2.8 10 6 gC-CH 4 day −1 ) with geomorphic change from low to high center polygons, cumulatively resulting in an estimated negative feedback to warming during peak growing season.

Alaska↗
USGS2017

Combined analysis of roadside and off-road breeding bird survey data to assess population change in Alaska

Management interest in North American birds has increasingly focused on species that breed in Alaska, USA, and Canada, where habitats are changing rapidly in response to climatic and anthropogenic factors. We used a series of hierarchical models to estimate rates of population change in 2 forested Bird Conservation Regions (BCRs) in Alaska based on data from the roadside North American Breeding Bird Survey (BBS) and the Alaska Landbird Monitoring Survey, which samples off-road areas on public resource lands. We estimated long-term (1993–2015) population trends for 84 bird species from the BBS and short-term (2003–2015) trends for 31 species from both surveys. Among the 84 species with long-term estimates, 11 had positive trends and 17 had negative trends in 1 or both BCRs; negative trends were primarily found among aerial insectivores and wetland-associated species, confirming range-wide negative continental trends for many of these birds. Three species with negative trends in the contiguous United States and southern Canada had positive trends in Alaska, suggesting different population dynamics at the northern edges of their ranges. Regional population trends within Alaska differed for several species, particularly those represented by different subspecies in the 2 BCRs, which are separated by rugged, glaciated mountain ranges. Analysis of the roadside and off-road data in a joint hierarchical model with shared parameters resulted in improved precision of trend estimates and suggested a roadside-related difference in underlying population trends for several species, particularly within the Northwestern Interior Forest BCR. The combined analysis highlights the importance of considering population structure, physiographic barriers, and spatial heterogeneity in habitat change when assessing patterns of population change across a landscape as broad as Alaska. Combined analysis of roadside and off-road survey data in a hierarchical framework may be particularly useful for evaluating patterns of population change in relatively undeveloped regions with sparse roadside BBS coverage.

Condor↗
USGS2020

Late Cenozoic climate change paces landscape adjustments to Yukon River capture

Late Cenozoic cooling and changes in glacial–interglacial cycle tempo are thought to increase global rates of erosion starting ~3 million years ago (Ma). Bedrock rivers set rates and patterns of erosion in most landscapes, but constraints on river response to late Cenozoic climate change remain elusive. Here, we determine cosmogenic isotope and luminescence ages of well-preserved bedrock terraces along the Fortymile River (Yukon River basin) to reconstruct an ~5 Myr history of fluvial adjustment to late Cenozoic climate and Yukon River headwater capture at 2.6 Ma. Post-capture Yukon River downcutting lowered the Fortymile River outlet, forcing subsequent bedrock incision throughout the Fortymile basin in two pulses, from 2.4 to 1.8 Ma and at ~1 Ma. These pulses of incision disrupted longer intervals of slow river channel sedimentation under near-consistent climate forcing from 4.8 to 2.4 Ma and from 1.8 to ~1 Ma. The Fortymile River delivers sediment to the Bering Sea, where provenance and accumulation rate changes since 4.3 Ma match observed variations in incision. Our results link alluviation and incision to late Cenozoic climate steadiness and change, respectively, and support the hypothesis that climate-forced changes in precipitation and runoff fundamentally control the pace of river incision and landscape erosion.

Alaska↗
USGS2016

Foreword: The dynamics of change in Alaska’s boreal forests: Resilience and vulnerability in response to climate warming

Long-term research by the Bonanza Creek (BNZ) Long Term Ecological Research (LTER) program has documented natural patterns of interannual and successional variability of the boreal forest in interior Alaska against which we can detect changes in system behavior. Between 2004 and 2010 the BNZ LTER program focused on understanding the dynamics of change through studying the resilience and vulnerability of Alaska's boreal forest in response to climate warming. The overarching question in this endeavor has been “How are boreal ecosystems responding, both gradually and abruptly, to climate warming, and what new landscape patterns are emerging?”

Alaska↗
USGS2012

Reference hydrologic networks II. Using reference hydrologic networks to assess climate-driven changes in streamflow

Reference hydrologic networks (RHNs) can play an important role in monitoring for changes in the hydrological regime related to climate variation and change. Currently, the literature concerning hydrological response to climate variations is complex and confounded by the combinations of many methods of analysis, wide variations in hydrology, and the inclusion of data series that include changes in land use, storage regulation and water use in addition to those of climate. Three case studies that illustrate a variety of approaches to the analysis of data from RHNs are presented and used, together with a summary of studies from the literature, to develop approaches for the investigation of changes in the hydrological regime at a continental or global scale, particularly for international comparison. We present recommendations for an analysis framework and the next steps to advance such an initiative. There is a particular focus on the desirability of establishing standardized procedures and methodologies for both the creation of new national RHNs and the systematic analysis of data derived from a collection of RHNs.

Hydrological Sciences Journal↗
USGS2015

Climate-induced changes in lake ecosystem structure inferred from coupled neo- and paleoecological approaches

Over the 20th century, surface water temperatures have increased in many lake ecosystems around the world, but long-term trends in the vertical thermal structure of lakes remain unclear, despite the strong control that thermal stratification exerts on the biological response of lakes to climate change. Here we used both neo- and paleoecological approaches to develop a fossil-based inference model for lake mixing depths and thereby refine understanding of lake thermal structure change. We focused on three common planktonic diatom taxa, the distributions of which previous research suggests might be affected by mixing depth. Comparative lake surveys and growth rate experiments revealed that these species respond to lake thermal structure when nitrogen is sufficient, with species optima ranging from shallower to deeper mixing depths. The diatom-based mixing depth model was applied to sedimentary diatom profiles extending back to 1750 AD in two lakes with moderate nitrate concentrations but differing climate settings. Thermal reconstructions were consistent with expected changes, with shallower mixing depths inferred for an alpine lake where treeline has advanced, and deeper mixing depths inferred for a boreal lake where wind strength has increased. The inference model developed here provides a new tool to expand and refine understanding of climate-induced changes in lake ecosystems.

Ecology↗