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At least 613 records · Page 34Linked to original sources
USGS2026

Adaptive capacity of freshwater organisms in North America: Current understanding and future applications

Freshwater species are increasingly threatened by climate change, yet our ability to assess their vulnerability remains incomplete. Typically, climate change vulnerability assessments (CCVAs) evaluate three components: exposure, sensitivity, and adaptive capacity. Adaptive capacity, defined as the ability of a species to adjust to changing conditions, provides critical insight into how species may persist under future scenarios and can strengthen conservation planning by highlighting opportunities for resilience and targeted management strategies. Trait-based approaches offer a promising path for managers to operationalize adaptive capacity by identifying measurable biological and ecological traits that influence climate change response strategies. However, these insights are rarely integrated into broader vulnerability frameworks that support conservation decision making. We build on previous research to synthesize current understanding of adaptive capacity for three freshwater taxa in North America: fishes, mussels, and crayfishes. Our objectives were to: (1) assess the relevance of adaptive capacity factors for fishes, mussels, and crayfishes; (2) identify key opportunities and gaps in linking trait-based information into adaptive capacity assessments; and (3) illustrate how incorporating adaptive capacity can enhance management decisions for freshwater species under climate change. We used an expert workshop, literature review, and case studies to identify relevant adaptive capacity factors, assess available information, and evaluate inclusion in management contexts. We found that all three taxa had sufficient information to inform adaptive capacity assessments. In addition to existing adaptive capacity factors, we identified Morphology as an important yet underutilized cross-cutting diagnostic category when information was limited. By explicitly linking trait-based approaches with adaptive capacity frameworks, we offer practical guidance for improving climate adaptation strategies and prioritizing management actions for freshwater biodiversity under accelerating global change.

Global Change Biology Communications↗
USGS2020

Climate change vulnerability assessment for Pacific Lamprey in rivers of the Western United States

Pacific Lamprey (Entosphenus tridentatus) are a native anadromous species that, like salmon, historically returned to spawn in large numbers in watersheds along the west coast of the United States (U.S.). Lamprey play a vital role in river ecosystems and are one of the oldest vertebrates that have persisted over time likely influencing the evolution of many aquatic species. Pacific Lamprey have declined in abundance and are restricted in distribution throughout Washington, Oregon, Idaho and California. A key uncertainty influencing Pacific Lamprey status is the impact of climate change. We modified the NatureServe Climate Change Vulnerability Index (CCVI) to accommodate climate predictions from the International Panel on Climate Change. Using downscaled information, we characterized changes in 15 rivers occupied by Pacific Lamprey in the western U.S. We evaluated this risk under Representative Concentration Pathways (RCP) 4.5 and 8.5 for two time periods (mid-century 2040–2069 and end-century 2070–2099). The CCVI scores generally increased when going from RCP 4.5 to RCP 8.5 in three Global Climate Models for both mid-century and end-century, which our analyses forecasts degraded stream temperature and hydrologic conditions under increasing greenhouse gas emissions. The geographically assessed results suggest that climate change impacts to Pacific Lamprey vulnerability are magnified in highly altered rivers. If we continue to observe greenhouse gas emission levels associated with the RCP 8.5, Pacific Lamprey will be at greater risk to climate change impacts. In order to mitigate the risk from climate change toward the end of the century, additional actions will need to be prioritized to rapidly reduce the impact of these threats such as increasing flow, creating backwater habitat, restoring riparian vegetation and reducing stream disturbances. The findings revealed the patterns of vulnerability for Pacific Lamprey across their U.S. range are informative for prioritizing river restoration actions when paired with regional implementation plans.

California, Washington, Oregon, Idaho↗
USGS2023

Long-term assessment of relationships between changing environmental conditions and the physiology of southern Beaufort Sea polar bears (Ursus maritimus)

Climate change is influencing polar bear ( Ursus maritimus ) habitat, diet, and behavior but the effects of these changes on their physiology is not well understood. Blood-based biomarkers are used to assess the physiologic health of individuals but their usefulness for evaluating population health, especially as it relates to changing environmental conditions, has rarely been explored. We describe links between environmental conditions and physiologic functions of southern Beaufort Sea polar bears using data from blood samples collected from 1984 to 2018, a period marked by extensive environmental change. We evaluated associations between 13 physiologic biomarkers and circumpolar (Arctic oscillation index) and regional (wind patterns and ice-free days) environmental metrics and seasonal and demographic co-variates (age, sex, season, and year) known to affect polar bear ecology. We observed signs of dysregulation of water balance in polar bears following years with a lower annual Arctic oscillation index. In addition, liver enzyme values increased over time, which is suggestive of potential hepatocyte damage as the Arctic has warmed. Biomarkers of immune function increased with regional-scale wind patterns and the number of ice-free days over the Beaufort Sea continental shelf and were lower in years with a lower winter Arctic oscillation index, suggesting an increased allocation of energetic resources for immune processes under these conditions. We propose that the variation in polar bear immune and metabolic function is likely indicative of physiologic plasticity, a response that allows polar bears to remain in homeostasis even as they experience changes in nutrition and habitat in response to changing environments.

Alaska↗
USGS2025

Mountain sentinels in a changing world: Review and conservation implications of weather and climate effects on mountain goats (Oreamnos americanus)

Climate change is occurring at an accelerated rate in high-elevation alpine and mountain ecosystems. Cold-adapted, mountain species are at risk due to forecasted change and knowledge is needed to respond to current and future conservation challenges. Mountain goats ( Oreamnos americanus ) are an iconic species of North American mountain cultures and landscapes, and due to specialized adaptations for life in cold, mountainous environments they are particularly sensitive to changes in weather and climate. As sentinels of change in alpine ecosystems, the study of mountain goats offers insight into the ecological effects and conservation challenges associated with climate change in these sensitive and biodiverse environments. Here, we synthesize existing knowledge about how climate change is expected to influence environmental conditions experienced by mountain goats and associated mechanistic changes to behavior, nutritional ecology, demography, health, and interspecific interactions. In many instances, climate change effects are likely to be negative and additive to existing threats (such as human disturbance, hunting, disease, predation) though benefits are expected in some cases. Changes in climate and mountain environments will necessitate re-examination and modification of population monitoring, management, and conservation strategies. Specifically, spatiotemporal (and other) aspects of monitoring and management may need to be adjusted to accommodate emerging and novel conservation challenges. Yet, key data and knowledge gaps remain and should be addressed to advance conservation and decision-making capabilities. For mountain goats and similarly climate-sensitive alpine herbivores, effective conservation will ultimately benefit from collaborations among diverse networks guided by well-planned, strategic visions focused on common ground – namely the resiliency and persistence of culturally and ecologically significant mountain species and the alpine environment they inhabit.

Alaska, Alberta, British Columbia, Idaho, Montana,↗
USGS2013

Evidence for 20th century climate warming and wetland drying in the North American Prairie Pothole Region

The Prairie Pothole Region (PPR) of North America is a globally important resource that provides abundant and valuable ecosystem goods and services in the form of biodiversity, groundwater recharge, water purification, flood attenuation, and water and forage for agriculture. Numerous studies have found these wetlands, which number in the millions, to be highly sensitive to climate variability. Here, we compare wetland conditions between two 30-year periods (1946–1975; 1976–2005) using a hindcast simulation approach to determine if recent climate warming in the region has already resulted in changes in wetland condition. Simulations using the WETLANDSCAPE model show that 20th century climate change may have been sufficient to have a significant impact on wetland cover cycling. Modeled wetlands in the PPR's western Canadian prairies show the most dramatic effects: a recent trend toward shorter hydroperiods and less dynamic vegetation cycles, which already may have reduced the productivity of hundreds of wetland-dependent species.

Prairie Pothole Region↗
USGS2006

Response of Everglades tree islands to environmental change

Tree islands are centers of biodiversity within the Florida Everglades, USA, but the factors controlling their distribution, formation, and development are poorly understood. We use pollen assemblages from tree islands throughout the greater Everglades ecosystem to reconstruct the timing of tree island formation, patterns of development, and response to specific climatic and environmental stressors. These data indicate that fixed (teardrop-shaped) and strand tree islands developed well before substantial human alteration of the system, with initial tree island vegetation in place between 3500 and 500 calibrated years before present (cal yr BP), depending on the location in the Everglades wetland. Tree island development appears to have been triggered by regional- to global-scale climatic events at 2800 cal yr BP, 1600–1500 cal yr BP, 1200–1000 cal yr BP (early Medieval Warm Period), and 500–200 cal yr BP (Little Ice Age). These periods correspond to drought intervals documented in Central and South America and periods of southward displacement of the Intertropical Convergence Zone. The records indicate a coherence of climate patterns in both subtropical North America and the Northern Hemisphere Neotropics. Water management practices of the 20th century altered plant communities and size of tree islands throughout the Everglades. Responses range from loss of tree islands due to artificially long hydroperiods and deep water to expansion of tree islands after flow reductions. These data provide evidence for the rapidity of tree island response to specific hydrologic change and facilitate prediction of the response to future changes associated with Everglades restoration plans.

Florida↗
USGS2004

Plant functional traits in relation to fire in crown-fire ecosystems

Disturbance is a dominant factor in many ecosystems, and the disturbance regime is likely to change over the next decades in response to land-use changes and global warming. We assume that predictions of vegetation dynamics can be made on the basis of a set of life-history traits that characterize the response of a species to disturbance. For crown-fire ecosystems, the main plant traits related to postfire persistence are the ability to resprout (persistence of individuals) and the ability to retain a persistent seed bank (persistence of populations). In this context, we asked (1) to what extent do different life-history traits co-occur with the ability to resprout and/or the ability to retain a persistent seed bank among differing ecosystems and (2) to what extent do combinations of fire-related traits (fire syndromes) change in a fire regime gradient? We explored these questions by reviewing the literature and analyzing databases compiled from different crown-fire ecosystems (mainly eastern Australia, California, and the Mediterranean basin). The review suggests that the pattern of correlation between the two basic postfire persistent traits and other plant traits varies between continents and ecosystems. From these results we predict, for instance, that not all resprouters respond in a similar way everywhere because the associated plant traits of resprouter species vary in different places. Thus, attempts to generalize predictions on the basis of the resprouting capacity may have limited power at a global scale. An example is presented for Australian heathlands. Considering the combination of persistence at individual (resprouting) and at population (seed bank) level, the predictive power at local scale was significantly increased.

Ecology↗
USGS2012

Revolutionary land use change in the 21st century: Is (rangeland) science relevant?

Rapidly increasing demand for food, fiber, and fuel together with new technologies and the mobility of global capital are driving revolutionary changes in land use throughout the world. Efforts to increase land productivity include conversion of millions of hectares of rangelands to crop production, including many marginal lands with low resistance and resilience to degradation. Sustaining the productivity of these lands requires careful land use planning and innovative management systems. Historically, this responsibility has been left to agronomists and others with expertise in crop production. In this article, we argue that the revolutionary land use changes necessary to support national and global food security potentially make rangeland science more relevant now than ever. Maintaining and increasing relevance will require a revolutionary change in range science from a discipline that focuses on a particular land use or land cover to one that addresses the challenge of managing all lands that, at one time, were considered to be marginal for crop production. We propose four strategies to increase the relevance of rangeland science to global land management: 1) expand our awareness and understanding of local to global economic, social, and technological trends in order to anticipate and identify drivers and patterns of conversion; 2) emphasize empirical studies and modeling that anticipate the biophysical (ecosystem services) and societal consequences of large-scale changes in land cover and use; 3) significantly increase communication and collaboration with the disciplines and sectors of society currently responsible for managing the new land uses; and 4) develop and adopt a dynamic and flexible resilience-based land classification system and data-supported conceptual models (e.g., state-and-transition models) that represent all lands, regardless of use and the consequences of land conversion to various uses instead of changes in state or condition that are focused on a single land use.

Rangeland Ecology and Management↗
USGS2014

Projecting climate effects on birds and reptiles of the Southwestern United States

We modeled the current and future breeding ranges of seven bird and five reptile species in the Southwestern United States with sets of landscape, biotic (plant), and climatic global circulation model (GCM) variables. For modeling purposes, we used PRISM data to characterize the climate of the Western United States between 1980 and 2009 (baseline for birds) and between 1940 and 2009 (baseline for reptiles). In contrast, we used a pre-selected set of GCMs that are known to be good predictors of southwestern climate (five individual and one ensemble GCM), for the A1B emission scenario, to characterize future climatic conditions in three time periods (2010–39; 2040–69; and, 2070–99). Our modeling approach relied on conceptual models for each target species to inform selection of candidate explanatory variables and to interpret the ecological meaning of developed probabilistic distribution models. We employed logistic regression and maximum entropy modeling techniques to create a set of probabilistic models for each target species. We considered climatic, landscape, and plant variables when developing and testing our probabilistic models. Climatic variables included the maximum and minimum mean monthly and seasonal temperature and precipitation for three time periods. Landscape features included terrain ruggedness and insolation. We also considered plant species distributions as candidate explanatory variables where prior ecological knowledge implicated a strong association between a plant and animal species. Projected changes in range varied widely among species, from major losses to major gains. Breeding bird ranges exhibited greater expansions and contractions than did reptile species. We project range losses for Williamson’s sapsucker and pygmy nuthatch of a magnitude that could move these two species close to extinction within the next century. Although both species currently have a relatively limited distribution, they can be locally common, and neither are presently considered candidates for prospective endangerment. We project range losses of over 40 percent, from its current extent of occurrence, for the plateau striped whiptail, Arizona black rattlesnake, and common lesser earless lizard. Currently, these reptile species are thought to be common or at least locally abundant throughout their ranges. The total contribution of plants in each distribution model was very small, but models that contained at least one plant always outperformed models with only physical variables (climatic or landscape). The magnitude of change in projected range increased further into the future, especially when a plant was in the model. Among bird species, those that had the strongest association with a landscape feature during the breeding season, such as terrain ruggedness and insolation, exhibited the smallest contractions in projected breeding range in the future. In contrast, bird species that had weak associations with landscape features, but strong climatic associations, suffered the greatest breeding range contractions. Thus, landscape effects appeared to buffer some of the negative effects of climate change for some species. Among bird species, magnitude of change in projected breeding range was positively related to the annual average temperature of their baseline distribution, thus species with the warmest breeding ranges exhibited the greatest changes in future breeding ranges. This pattern was not evident for reptiles, but might exist if additional species were included in the model. Our results provide managers with a series of projected range maps that will enable scientists, concerned citizens, and wildlife managers to identify what the potential effects of climate change will be on bird and reptile distributions in the Western United States. We hope that our results can be used in proactive ways to mitigate some of the potential effects of climate change on selected species.

Colorado Plateau;Sonoran Desert↗
USGS2002

Modeling and measuring snow for assessing climate change impacts in Glacier National Park, Montana

A 12-year program of global change research at Glacier National Park by the U.S. Geological Survey and numerous collaborators has made progress in quantifying the role of snow as a driver of mountain ecosystem processes. Spatially extensive snow surveys during the annual accumulation/ablation cycle covered two mountain watersheds and approximately 1,000 km2 . Over 7,000 snow depth and snow water equivalent (SWE) measurements have been made through spring 2002. These augment two SNOTEL sites, 9 NRCS snow courses, and approximately 150 snow pit analyses. Snow data were used to establish spatially-explicit interannual variability in snowpack SWE. East of the Continental Divide, snowpack SWE was lower but also less variable than west of the Divide. Analysis of snowpacks suggest downward trends in SWE, a reduction in snow cover duration, and earlier melt-out dates during the past 52 years. Concurrently, high elevation forests and treelines have responded with increased growth. However, the 80 year record of snow from 3 NRCS snow courses reflects a strong influence from the Pacific Decadal Oscillation, resulting in 20-30 year phases of greater or lesser mean SWE. Coupled with the fine-resolution spatial snow data from the two watersheds, the ecological consequences of changes in snowpack can be empirically assessed at a habitat patch scale. This will be required because snow distribution models have had varied success in simulating snowpack accumulation/ablation dynamics in these mountain watersheds, ranging from R2=0.38 for individual south-facing forested snow survey routes to R2=0.95 when aggregated to the watershed scale. Key ecological responses to snowpack changes occur below the watershed scale, such as snow-mediated expansion of forest into subalpine meadows, making continued spatially-explicit snow surveys a necessity.

Montana↗
USGS2021

Extreme events trigger terrestrial and marine ecosystem collapses: A tale of two regions

We outline the multiple, cross-scale, and complex consequences of terrestrial and marine ecosystem heatwaves in two regions on opposite sides of the planet: the southwestern USA and southwestern Australia, both encompassing Global Biodiversity Hotspots, and where ecosystem collapses or features of it have occurred in the past two decades. We highlight ecosystem shifts that have clearly demonstrated a substantial change from a baseline state over time, although not necessarily across their entire distribution, with evidence of collapse at local scales. Responses to temperature extremes, such as heatwaves, encompass processes at all scales, including population level (e.g. altered demography such as survival, recruitment, and fecundity, together resulting in structural changes), community level (e.g. species compositional shifts), and ecosystem level (e.g. carbon loss), as well as physical properties altered by vegetation loss (e.g. microclimate, fire behaviour on land). These changes impact all trophic levels with foundational species losses (such as seagrasses, kelp, and trees), flowing through to vertebrates (such as sea turtles, penguins, and cockatoos). Where extensive collapse has occurred, shifts in microclimate could affect important biosphere-to-atmosphere feedbacks including fluxes of energy, carbon, and water. Such extensive changes usually do not occur in isolation and frequently interact with other disturbance processes such as fire, storms, pathogen and pest outbreaks, and anthropogenic stressors. Interactions may alter the likelihood, extent, or severity of subsequent disturbances (linked disturbances) as well as condition the ecological response and recovery (compound disturbances). In addition, if ecosystem collapse is extensive enough (e.g. tree die-off), those changes also can impact climate and ecosystems elsewhere via ecoclimate teleconnections. Increasing rates of climatic extremes will drive a host of direct and indirect feedbacks certain to produce large-scale shifts in ecological functioning at unprecedented rates. Understanding how, why, and where these shifts will occur will be critical for effective ecosystem management and climate change mitigation.

Book chapter↗
USGS2020

Nutrients and warming interact to force mountain lakes into unprecedented ecological state

While deposition of reactive nitrogen (N) in the 20th century has been strongly linked to changes in diatom assemblages in high-elevation lakes, pronounced and contemporaneous changes in other algal groups suggest additional drivers. We explored the origin and magnitude of changes in two mountain lakes from the end of the Little Ice Age at ca. 1850, to ca. 2010, using lake sediments. We found dramatic changes in algal community abundance and composition. While diatoms remain the most abundant photosynthetic organisms, concentrations of diatom pigments decreased while pigments representing chlorophytes increased 200-300% since ca. 1950 and total algal biomass more than doubled. Some algal changes began ca. 1900, but shifts in most sedimentary proxies accelerated ca. 1950 commensurate with many human-caused changes to the Earth system. In addition to N deposition, aeolian dust deposition may have contributed phosphorus. Strong increases in summer air and surface water temperatures since 1983 have direct and indirect consequences for high elevation ecosystems. Such warming could have directly enhanced nutrient use and primary production. Indirect consequences of warming include enhanced leaching of nutrients from geologic and cryosphere sources, particularly as glaciers ablate. While we infer causal mechanisms, changes in primary producer communities appear to be without historical precedent and are commensurate with the post-1950 acceleration of global change.

Proceedings of the Royal Society B: Biological Sci↗
USGS2014

Change in agricultural land use constrains adaptation of national wildlife refuges to climate change

Land-use change around protected areas limits their ability to conserve biodiversity by altering ecological processes such as natural hydrologic and disturbance regimes, facilitating species invasions, and interfering with dispersal of organisms. This paper informs USA National Wildlife Refuge System conservation planning by predicting future land-use change on lands within 25 km distance of 461 refuges in the USA using an econometric model. The model contained two differing policy scenarios, namely a ‘business-as-usual’ scenario and a ‘pro-agriculture’ scenario. Regardless of scenario, by 2051, forest cover and urban land use were predicted to increase around refuges, while the extent of range and pasture was predicted to decrease; cropland use decreased under the business-as-usual scenario, but increased under the pro-agriculture scenario. Increasing agricultural land value under the pro-agriculture scenario slowed an expected increase in forest around refuges, and doubled the rate of range and pasture loss. Intensity of land-use change on lands surrounding refuges differed by regions. Regional differences among scenarios revealed that an understanding of regional and local land-use dynamics and management options was an essential requirement to effectively manage these conserved lands. Such knowledge is particularly important given the predicted need to adapt to a changing global climate.

Environmental Conservation↗
USGS2020

Paleoclimate ocean conditions shaped the evolution of corals and their skeletal composition through deep time

Identifying how past environmental conditions shaped the evolution of corals and their skeletal traits provides a framework for predicting their persistence and that of their non-calcifying relatives under impending global warming and ocean acidification. Here we show that ocean geochemistry, particularly aragonite–calcite seas, drives patterns of morphological evolution in anthozoans (corals, sea anemones) by examining skeletal traits in the context of a robust, time-calibrated phylogeny. The lability of skeletal composition among octocorals suggests a greater ability to adapt to changes in ocean chemistry compared with the homogeneity of the aragonitic skeleton of scleractinian corals. Pulses of diversification in anthozoans follow mass extinctions and reef crises, with sea anemones and proteinaceous corals filling empty niches as tropical reef builders went extinct. Changing environmental conditions will likely diminish aragonitic reef-building scleractinians, but the evolutionary history of the Anthozoa suggests other groups will persist and diversify in their wake.

Nature Ecology & Evolution↗
USGS2022

MASTREE+: Time-series of plant reproductive effort from six continents

Significant gaps remain in understanding the response of plant reproduction to environmental change. This is partly because measuring reproduction in long-lived plants requires direct observation over many years and such datasets have rarely been made publicly available. Here we introduce MASTREE+, a data set that collates reproductive time-series data from across the globe and makes these data freely available to the community. MASTREE+ includes 73,828 georeferenced observations of annual reproduction (e.g. seed and fruit counts) in perennial plant populations worldwide. These observations consist of 5971 population-level time-series from 974 species in 66 countries. The mean and median time-series length is 12.4 and 10 years respectively, and the data set includes 1122 series that extend over at least two decades (≥20 years of observations). For a subset of well-studied species, MASTREE+ includes extensive replication of time-series across geographical and climatic gradients. Here we describe the open-access data set, available as a.csv file, and we introduce an associated web-based app for data exploration. MASTREE+ will provide the basis for improved understanding of the response of long-lived plant reproduction to environmental change. Additionally, MASTREE+ will enable investigation of the ecology and evolution of reproductive strategies in perennial plants, and the role of plant reproduction as a driver of ecosystem dynamics.

Global Change Biology↗
USGS2025

Salmonid sensory system development is affected by climate change driven temperature increases

Increases in water temperature due to global climate change are known to alter the course and timing of fish development. The mechanosensory lateral line (LL) system mediates flow-sensing behaviors vital for survival in fishes, but the effects of increased water temperatures resulting from climate change on its development have not been examined. Here LL development was documented in a cold-water salmonid (brook trout, Salvelinus fontinalis ) reared at the thermograph of a long-term study stream (ambient) and two higher temperatures (+ 2 and + 4 °C) that reflect projected increases within their native range. At these two higher temperatures, fish reach crucial early life history transitions earlier (e.g., hatch, “swim-up” from gravel nests into the water column) and are larger in size through the parr (juvenile) stage. Early forming canal neuromast receptor organs are larger, and the process of canal morphogenesis is also accelerated suggesting potential consequences for neuromast function and presumably for LL-mediated behaviors. A potential mismatch between the timing of transitions in early life history stages, the ability to carry out LL-mediated behaviors (e.g., prey detection), and the timing of the seasonal emergence of their preferred prey, could have serious implications for cold-water salmonid ecology and survival.

Scientific Reports↗
USGS2019

Soil and stand structure explain shrub mortality patterns following global change–type drought and extreme precipitation

(Bradford) The probability of extreme weather events is increasing, with the potential for widespread impacts to plants, plant communities, and ecosystems. Reports of drought-related tree mortality are becoming more frequent along with increasing evidence that drought accompanied by high temperatures is especially detrimental. Simultaneously, extreme large precipitation events have become more frequent over the past century. Water-limited ecosystems may be more vulnerable to these extreme events than other ecosystems, especially when pushed outside of their historical range of variability. However, drought-related mortality of shrubs—an important component of dryland vegetation—remains understudied relative to tree mortality. In 2014, a landscape-scale die-off of the widespread shrub, big sagebrush (Artemisia tridentata Nutt.), was reported in southwest Wyoming, following extreme hot and dry conditions in 2012 and extremely high precipitation in September of 2013. Here, we examined how severe drought, extreme precipitation, soil texture and salinity, and potential competition contributed to this die-off event. At 98 plots within and around the die-off we quantified big sagebrush mortality, characterized soil texture and salinity, and simulated soil water conditions from 1916-2016 using an ecosystem water balance model. We found that the extreme weather conditions alone did not explain patterns of big sagebrush mortality and did not result in extreme (historically unprecedented) soil water conditions during the drought. Instead, plots with chronically dry soil conditions experienced greatest mortality following the global-change type (hot) drought in 2012. Furthermore, mortality was greater in locations with high potential run-on and low potential run-off where saturated soil conditions were simulated in September 2013, suggesting that extreme precipitation also played an important role in the die-off in these locations. In locations where drought alone contributed to mortality, competition negatively impacted big sagebrush. In locations that may have been affected by both drought and saturation, however, mortality was greatest where competition was lowest, suggesting that these locations may have already been less favorable to big sagebrush. Paradoxically, vulnerability to both extreme events (drought and saturation) was associated with finer-textured soils, and our results highlight the importance of soils in determining local variation the vulnerability of dryland plants to extreme events.

Wyoming↗
USGS2011

Evaluating the effects of future climate change and elevated CO 2 on the water use efficiency in terrestrial ecosystems of China

Water use efficiency (WUE) is an important variable used in climate change and hydrological studies in relation to how it links ecosystem carbon cycles and hydrological cycles together. However, obtaining reliable WUE results based on site-level flux data remains a great challenge when scaling up to larger regional zones. Biophysical, process-based ecosystem models are powerful tools to study WUE at large spatial and temporal scales. The Integrated BIosphere Simulator (IBIS) was used to evaluate the effects of climate change and elevated CO 2 concentrations on ecosystem-level WUE (defined as the ratio of gross primary production (GPP) to evapotranspiration (ET)) in relation to terrestrial ecosystems in China for 2009–2099. Climate scenario data (IPCC SRES A2 and SRES B1) generated from the Third Generation Coupled Global Climate Model (CGCM3) was used in the simulations. Seven simulations were implemented according to the assemblage of different elevated CO 2 concentrations scenarios and different climate change scenarios. Analysis suggests that (1) further elevated CO 2 concentrations will significantly enhance the WUE over China by the end of the twenty-first century, especially in forest areas; (2) effects of climate change on WUE will vary for different geographical regions in China with negative effects occurring primarily in southern regions and positive effects occurring primarily in high latitude and altitude regions (Tibetan Plateau); (3) WUE will maintain the current levels for 2009–2099 under the constant climate scenario (i.e. using mean climate condition of 1951–2006 and CO 2 concentrations of the 2008 level); and (4) WUE will decrease with the increase of water resource restriction (expressed as evaporation ratio) among different ecosystems.

Ecological Modelling↗