Climate change impacts on selected global rangeland ecosystem services

Rangelands are Earth's dominant land cover and are important providers of ecosystem services. Reliance on rangelands is projected to grow, thus understanding the sensitivity of rangelands to future climates is essential. We used a new ecosystem model of moderate complexity that allows, for the first time, to quantify global changes expected in rangelands under future climates. The mean global annual net primary production (NPP) may decline by 10 g C m^?2 year^?1 in 2050 under Representative Concentration Pathway (RCP) 8.5, but herbaceous NPP is projected to increase slightly (i.e., average of 3 g C m^?2 year^?1). Responses vary substantially from place‐to‐place, with large increases in annual productivity projected in northern regions (e.g., a 21% increase in productivity in the US and Canada) and large declines in western Africa (?46% in sub‐Saharan western Africa) and Australia (?17%). Soil organic carbon is projected to increase in Australia (9%), the Middle East (14%), and central Asia (16%) and decline in many African savannas (e.g., ?18% in sub‐Saharan western Africa). Livestock are projected to decline 7.5 to 9.6%, an economic loss of from $9.7 to $12.6 billion. Our results suggest that forage production in Africa is sensitive to changes in climate, which will have substantial impacts on the livelihoods of the more than 180 million people who raise livestock on those rangelands. Our approach and the simulation tool presented here offer considerable potential for forecasting future conditions, highlight regions of concern, and support analyses where costs and benefits of adaptations and policies may be quantified. Otherwise, the technical options and policy and enabling environment that are needed to facilitate widespread adaptation may be very difficult to elucidate.     

Climate change and community disassembly: impacts of warming on tropical and temperate montane community structure

Both tropical and temperate species are responding to global warming through range shifts, but our understanding of the consequences of these shifts for whole communities is limited. Here, we use current elevational range data for six taxonomic groups spanning 90° in latitude to examine the potential impacts of climate-driven range shifts on community change, or 'disassembly', across latitude. Elevational ranges are smaller at low latitudes for most groups and, as a consequence, tropical communities appear to be more sensitive to temperature increases compared with temperate communities. Under site-specific temperature projections, we generally found greater community disassembly in tropical compared with temperate communities, although this varied by dispersal assumptions. Mountain height can impact the amount of community disassembly, with greater change occurring on smaller mountains. Finally, projected community disassembly was higher for ectotherms than endotherms, although the variation among ectotherms was greater than the variation separating endotherms and ectotherms.     

Climate change impacts on West Nile virus transmission in a global context

West Nile virus (WNV), the most widely distributed virus of the encephalitic flaviviruses, is a vector-borne pathogen of global importance. The transmission cycle exists in rural and urban areas where the virus infects birds, humans, horses and other mammals. Multiple factors impact the transmission and distribution of WNV, related to the dynamics and interactions between pathogen, vector, vertebrate hosts and environment. Hence, among other drivers, weather conditions have direct and indirect influences on vector competence (the ability to acquire, maintain and transmit the virus), on the vector population dynamic and on the virus replication rate within the mosquito, which are mostly weather dependent. The importance of climatic factors (temperature, precipitation, relative humidity and winds) as drivers in WNV epidemiology is increasing under conditions of climate change. Indeed, recent changes in climatic conditions, particularly increased ambient temperature and fluctuations in rainfall amounts, contributed to the maintenance (endemization process) of WNV in various locations in southern Europe, western Asia, the eastern Mediterranean, the Canadian Prairies, parts of the USA and Australia. As predictions show that the current trends are expected to continue, for better preparedness, any assessment of future transmission of WNV should take into consideration the impacts of climate change.     

Climate change impacts on biodiversity in Switzerland: A review

A noticeable increase in mean temperature has already been observed in Switzerland and summer temperatures up to 4.8 K warmer are expected by 2090. This article reviews the observed impacts of climate change on biodiversity and considers some perspectives for the future at the national level.The following impacts are already evident for all considered taxonomic groups: elevation shifts of distribution towards mountain summits, spread of thermophilous species, colonisation by new species from warmer areas and phenological shifts. Additionally, in the driest areas, increasing droughts are affecting tree survival and fish species are suffering from warm temperatures in lowland regions. These observations are coherent with model projections, and future changes will probably follow the current trends.These changes will likely cause extinctions for alpine species (competition, loss of habitat) and lowland species (temperature or drought stress). In the very urbanised Swiss landscape, the high fragmentation of the natural ecosystems will hinder the dispersal of many species towards mountains. Moreover, disruptions in species interactions caused by individual migration rates or phenological shifts are likely to have consequences for biodiversity. Conversely, the inertia of the ecosystems (species longevity, restricted dispersal) and the local persistence of populations will probably result in lower extinction rates than expected with some models, at least in 21st century. It is thus very difficult to estimate the impact of climate change in terms of species extinctions. A greater recognition by society of the intrinsic value of biodiversity and of its importance for our existence will be essential to put in place effective mitigation measures and to safeguard a maximum number of native species.     

Hyperactivity in anorexia nervosa: warming up not just burning-off calories

Excessive physical activity is a common feature in Anorexia Nervosa (AN) that interferes with the recovery process. Animal models have demonstrated that ambient temperature modulates physical activity in semi-starved animals. The aim of the present study was to assess the effect of ambient temperature on physical activity in AN patients in the acute phase of the illness. Thirty-seven patients with AN wore an accelerometer to measure physical activity within the first week of contacting a specialized eating disorder center. Standardized measures of anxiety, depression and eating disorder psychopathology were assessed. Corresponding daily values for ambient temperature were obtained from local meteorological stations. Ambient temperature was negatively correlated with physical activity (p = −.405) and was the only variable that accounted for a significant portion of the variance in physical activity (p = .034). Consistent with recent research with an analogous animal model of the disorder, our findings suggest that ambient temperature is a critical factor contributing to the expression of excessive physical activity levels in AN. Keeping patients warm may prove to be a beneficial treatment option for this symptom.     

Climate change and pollutant impacts on Scottish vegetation

Summary

By the 2050s the UK is projected to be about 1.6°C warmer, when the atmospheric CO₂ concentration will be 525 ppmv. These changes will have profound effects on the Scottish flora and fauna. Vegetation primary productivity will increase, except in dry regions, and the productivity of upland forest plantations may increase by several Yield Classes. The spread of plant species may be less than expected, but a number of slow-growing ‘stress-tolerant’ species, including montane/alpine species, are likely to be lost. Nitrogen deposited as a result of emission of NO_X from vehicles and NH₃ from agriculture is now a major source of acidity, and problems of acidification and eutrophication are linked. Despite reductions in sulphur emissions, critical loads of acid deposition are likely to be exceeded for soils in most of the Scottish uplands until at least 2005. Critical levels affecting tree growth may be exceeded where forests are in cloud for 10% of the time in areas of the Great Glen. Much of the Scottish uplands receives 25–30 kg N ha^-1 yr^-1, which may be causing change in species composition. Background tropospheric ozone concentrations are increasing. Much of the Scottish uplands experiences mean summer ozone concentrations exceeding those in southern England, but with fewer exceedances of critical levels. However, many crops and some sensitive native species are probably being adversely affected.     

Climate warming interacts with other global change drivers to influence plant phenology: A meta-analysis of experimental studies

Shifts in plant phenology influence ecosystem structures and functions, yet how multiple global change drivers interact to affect phenology remains elusive. We conducted a meta-analysis of 242 published articles to assess interactions between warming (W) and other global change drivers including nitrogen addition (N), increased precipitation (IP), decreased precipitation (DP) and elevated CO₂ (eCO₂) on multiple phenophases in experimental studies. We show that leaf out and first flowering were most strongly affected by warming, while warming and decreased precipitation were the most pronounced drivers for leaf colouring. Moreover, interactions between warming and other global change drivers were common and both synergistic and antagonistic interactions were observed: interactions W + IP and W + eCO₂ were frequently synergistic, whereas interactions W + N and W + DP were mostly antagonistic. These findings demonstrate that global change drivers often affect plant phenology interactively. Incorporating the multitude of interactions into models is crucial for accurately predicting plant responses to global changes.     

Synergistic impacts of global warming on the resilience of coral reefs

Recent epizootics have removed important functional species from Caribbean coral reefs and left communities vulnerable to alternative attractors. Global warming will impact reefs further through two mechanisms. A chronic mechanism reduces coral calcification, which can result in depressed somatic growth. An acute mechanism, coral bleaching, causes extreme mortality when sea temperatures become anomalously high. We ask how these two mechanisms interact in driving future reef state (coral cover) and resilience (the probability of a reef remaining within a coral attractor). We find that acute mechanisms have the greatest impact overall, but the nature of the interaction with chronic stress depends on the metric considered. Chronic and acute stress act additively on reef state but form a strong synergy when influencing resilience by intensifying a regime shift. Chronic stress increases the size of the algal basin of attraction (at the expense of the coral basin), whereas coral bleaching pushes the system closer to the algal attractor. Resilience can change faster—and earlier—than a change in reef state. Therefore, we caution against basing management solely on measures of reef state because a loss of resilience can go unnoticed for many years and then become disproportionately more difficult to restore.     

Reduced diurnal temperature range does not change warming impacts on ecosystem carbon balance of Mediterranean grassland mesocosms

Daily minimum temperature (T_min) has increased faster than daily maximum temperature (T_max) in many parts of the world, leading to decreases in diurnal temperature range (DTR). Projections suggest that these trends are likely to continue in many regions, particularly in northern latitudes and in arid regions. Despite wide speculation that asymmetric warming has different impacts on plant and ecosystem production than equal‐night‐and‐day warming, there has been little direct comparison of these scenarios. Reduced DTR has also been widely misinterpreted as a result of night‐only warming, when in fact T_min occurs near dawn, indicating higher morning as well as night temperatures. We report on the first experiment to examine ecosystem‐scale impacts of faster increases in T_min than in T_max, using precise temperature controls to create realistic diurnal temperature profiles with gradual day–night temperature transitions and elevated early morning as well as night temperatures. Studying a constructed grassland ecosystem containing species native to Oregon, USA, we found that the ecosystem lost more carbon at elevated than ambient temperatures, but remained unaffected by the 3 °C difference in DTR between symmetric warming (constantly ambient + 3.5 °C) and asymmetric warming (dawn T_min = ambient + 5 °C, afternoon T_max = ambient + 2 °C). Reducing DTR had no apparent effect on photosynthesis, probably because temperatures were most different in the morning and late afternoon when light was low. Respiration was also similar in both warming treatments, because respiration temperature sensitivity was not sufficient to respond to the limited temperature differences between asymmetric and symmetric warming. We concluded that changes in daily mean temperatures, rather than changes in T_min/T_max, were sufficient for predicting ecosystem carbon fluxes in this reconstructed Mediterranean grassland system.     

Bacterial translocation in cirrhosis is not caused by an abnormal small bowel gut microbiota

Sepsis is common in liver cirrhosis, and animal studies have shown the gut to be the principal source of infection, through bacterial overgrowth and translocation in the small bowel. A total of 33 patients were recruited into this study, 10 without cirrhosis and 23 with cirrhotic liver disease. Six distal duodenal biopsies were obtained and snap frozen for RNA and DNA extraction, or frozen for FISH. Peripheral venous bloods were obtained from 30 patients, including 17 chronic liver disease patients. Samples were analysed by real-time PCR, to assess total bacteria, bifidobacteria, bacteroides, enterobacteria, staphylococci, streptococci, lactobacilli, enterococci, Helicobacter pylori and moraxella, as well as TNF-α, IL-8 and IL-18. There was no evidence of bacterial overgrowth with respect to any of the individual bacterial groups, with the exception of enterococci, which were present in higher numbers in cirrhotic patients (P?=?0.04). There were no significant differences in any of the cytokines compared to the controls. The small intestinal mucosal microbiota in cirrhotic patients was qualitatively and quantitatively normal, and this shifts the focus of disease aetiology to factors that reduce gut integrity, failure of mechanisms to remove translocating bacteria, or the large bowel as the source of sepsis.     

Climate change intensification of herbivore impacts on tree recruitment

Altered species interactions are difficult to predict and yet may drive the response of ecological communities to climate change. We show that declining snowpack strengthens the impacts of a generalist herbivore, elk (Cervus elaphus), on a common tree species. Thick snowpack substantially reduces elk visitation to sites; aspen (Populus tremuloides) shoots in these areas experience lower browsing rates, higher survival and enhanced recruitment. Aspen inside herbivore exclosures have greatly increased recruitment, particularly at sites with thick snowpack. We suggest that long-term decreases in snowpack could help explain a widespread decline of aspen through previously unconsidered relationships. More generally, reduced snowpack across the Rocky Mountains, combined with rising elk populations, may remove the conditions needed for recruitment of this ecologically important tree species. These results highlight that herbivore behavioural responses to altered abiotic conditions are critical determinants of plant persistence. Predictions of climate change impacts must not overlook the crucial importance of species interactions.     

肠道菌群改变与结核分枝杆菌感染相互作用的研究进展

人体内肠道菌群数量庞大,参与机体物质代谢以及免疫应答反应,成为目前众多研究的热点.肠道菌群对于维持呼吸系统稳态,特别是肺部的稳态发挥着重要作用.目前越来越多的结果证明肠道菌群对机体免疫系统具有诱导和调节作用,这种免疫反应的改变对于结核病的发病和治疗有着深远意义.本文梳理了近年来国内外发表的肠道菌群与结核病相关的文献,讨...     

Climate change and its impacts on Vietnam agriculture: A macroeconomic perspective

Vietnam is an important contributor to the world's food industry as a major exporter of rice, seafood, and coffee. Climate change poses a serious threat to Vietnam's agricultural sector since it adversely affects food security in Vietnam and globally. This study investigates the short- and long-term effects of climate change on Vietnam's agriculture, both in terms of production and values at the macro level. Using the Autoregressive Distributed Lag (ARDL) model and the Toda-Yamamoto (1995) Granger causality test with annual data from 1990 to 2019, we confirm the detrimental impacts of global warming on Vietnam's agricultural performance in both the short and long term. We also reveal the favorable effects of CO₂ emissions, land, and fertilizer on Vietnam's agricultural production and economics. Other factors, including rainfall and labor, however, adversely affect Vietnam's agricultural output and economic performance. Based on the study's results, we provide policy recommendations to assist the government limit the negative effects of climate change on the national economy, thereby promoting poverty alleviation and sustainable development in Vietnam.     

Fingerprinting the impacts of global change on tropical forests

Recent observations of widespread changes in mature tropical forests such as increasing tree growth, recruitment and mortality rates and increasing above-ground biomass suggest that ''global change'' agents may be causing predictable changes in tropical forests. However, consensus over both the robustness of these changes and the environmental drivers that may be causing them is yet to emerge. This paper focuses on the second part of this debate. We review (i) the evidence that the physical, chemical and biological environment that tropical trees grow in has been altered over recent decades across large areas of the tropics, and (ii) the theoretical, experimental and observational evidence regarding the most likely effects of each of these changes on tropical forests. Ten potential widespread drivers of environmental change were identified: temperature, precipitation, solar radiation, climatic extremes (including El Niño-Southern Oscillation events), atmospheric CO2 concentrations, nutrient deposition, O3/acid depositions, hunting, land-use change and increasing liana numbers. We note that each of these environmental changes is expected to leave a unique ''fingerprint'' in tropical forests, as drivers directly force different processes, have different distributions in space and time and may affect some forests more than others (e.g. depending on soil fertility). Thus, in the third part of the paper we present testable a priori predictions of forest responses to assist ecologists in attributing particular changes in forests to particular causes across multiple datasets. Finally, we discuss how these drivers may change in the future and the possible consequences for tropical forests.     

Climate change and Australia: Trends,projections and impacts

Abstract This review summarizes recent research in Australia on: (i) climate and geophysical trends over the last few decades; (ii) projections for climate change in the 21st century; (iii) predicted impacts from modelling studies on particular ecosystems and native species; and (iv) ecological effects that have apparently occurred as a response to recent warming. Consistent with global trends, Australia has warmed ～0.8°C over the last century with minimum temperatures warming faster than maxima. There have been significant regional trends in rainfall with the northern, eastern and southern parts of the continent receiving greater rainfall and the western region receiving less. Higher rainfall has been associated with an increase in the number of rain days and heavy rainfall events. Sea surface temperatures on the Great Barrier Reef have increased and are associated with an increase in the frequency and severity of coral bleaching and mortality. Sea level rises in Australia have been regionally variable, and considerably less than the global average. Snow cover and duration have declined significantly at some sites in the Snowy Mountains. CSIRO projections for future climatic changes indicate increases in annual average temperatures of 0.4–2.0°C by 2030 (relative to 1990) and 1.0–6.0°C by 2070. Considerable uncertainty remains as to future changes in rainfall, El Niño Southern Oscillation events and tropical cyclone activity. Overall increases in potential evaporation over much of the continent are predicted as well as continued reductions in the extent and duration of snow cover. Future changes in temperature and rainfall are predicted to have significant impacts on most vegetation types that have been modelled to date, although the interactive effect of continuing increases in atmospheric CO₂ has not been incorporated into most modelling studies. Elevated CO₂ will most likely mitigate some of the impacts of climate change by reducing water stress. Future impacts on particular ecosystems include increased forest growth, alterations in competitive regimes between C3 and C4 grasses, increasing encroachment of woody shrubs into arid and semiarid rangelands, continued incursion of mangrove communities into freshwater wetlands, increasing frequency of coral bleaching, and establishment of woody species at increasingly higher elevations in the alpine zone. Modelling of potential impacts on specific Australian taxa using bioclimatic analysis programs such as bioclim consistently predicts contraction and/or fragmentation of species' current ranges. The bioclimates of some species of plants and vertebrates are predicted to disappear entirely with as little as 0.5–1.0°C of warming. Australia lacks the long‐term datasets and tradition of phenological monitoring that have allowed the detection of climate‐change‐related trends in the Northern Hemisphere. Long‐term changes in Australian vegetation can be mostly attributed to alterations in fire regimes, clearing and grazing, but some trends, such as encroachment of rainforest into eucalypt woodlands, and establishment of trees in subalpine meadows probably have a climatic component. Shifts in species distributions toward the south (bats, birds), upward in elevation (alpine mammals) or along changing rainfall contours (birds, semiarid reptiles), have recently been documented and offer circumstantial evidence that temperature and rainfall trends are already affecting geographic ranges. Future research directions suggested include giving more emphasis to the study of climatic impacts and understanding the factors that control species distributions, incorporating the effects of elevated CO₂ into climatic modelling for vegetation and selecting suitable species as indicators of climate‐induced change.     

Climate adaptation is not enough: warming does not facilitate success of southern tundra plant populations in the high Arctic

Rapidly rising temperatures are expected to cause latitudinal and elevational range shifts as species track their optimal climate north and upward. However, a lack of adaptation to environmental conditions other than climate – for example photoperiod, biotic interactions, or edaphic conditions – might limit the success of immigrants in a new location despite hospitable climatic conditions. Here, we present one of the first direct experimental tests of the hypothesis that warmer temperatures at northern latitudes will confer a fitness advantage to southern immigrants relative to native populations. As rates of warming in the Arctic are more than double the global average, understanding the impacts of warming in Arctic ecosystems is especially urgent. We established experimentally warmed and nonwarmed common garden plots at Alexandra Fiord, Ellesmere Island in the Canadian High Arctic with seeds of two forb species (Oxyria digyna and Papaver radicatum) originating from three to five populations at different latitudes across the Arctic. We found that plants from the local populations generally had higher survival and obtained a greater maximum size than foreign individuals, regardless of warming treatment. Phenological traits varied with latitude of the source population, such that southern populations demonstrated substantially delayed leaf‐out and senescence relative to northern populations. Our results suggest that environmental conditions other than temperature may influence the ability of foreign populations and species to establish at more northerly latitudes as the climate warms, potentially leading to lags in northward range shifts for some species.     

Potential impacts of global climate change on freshwater fisheries

Despite uncertainty in all levels of analysis, recent and long-term changes in our climate point to the distinct possibility that greenhouse gas emissions have altered mean annual temperatures, precipitation and weather patterns. Modeling efforts that use doubled atmospheric CO₂ scenarios predict a 1–7°C mean global temperature increase, regional changes in precipitation patterns and storm tracks, and the possibility of “surprises” or sudden irreversible regime shifts. The general effects of climate change on freshwater systems will likely be increased water temperatures, decreased dissolved oxygen levels, and the increased toxicity of pollutants. In lotic systems, altered hydrologic regimes and increased groundwater temperatures could affect the quality of fish habitat. In lentic systems, eutrophication may be exacerbated or offset, and stratification will likely become more pronounced and stronger. This could alter food webs and change habitat availability and quality. Fish physiology is inextricably linked to temperature, and fish have evolved to cope with specific hydrologic regimes and habitat niches. Therefore, their physiology and life histories will be affected by alterations induced by climate change. Fish communities may change as range shifts will likely occur on a species level, not a community level; this will add novel biotic pressures to aquatic communities. Genetic change is also possible and is the only biological option for fish that are unable to migrate or acclimate. Endemic species, species in fragmented habitats, or those in east–west oriented systems will be less able to follow changing thermal isolines over time. Artisanal, commercial, and recreational fisheries worldwide depend upon freshwater fishes. Impacted fisheries may make it difficult for developing countries to meet their food demand, and developed countries may experience economic losses. As it strengthens over time, global climate change will become a more powerful stressor for fish living in natural or artificial systems. Furthermore, human response to climate change (e.g., increased water diversion) will exacerbate its already-detrimental effects. Model predictions indicate that global climate change will continue even if greenhouse gas emissions decrease or cease. Therefore, proactive management strategies such as removing other stressors from natural systems will be necessary to sustain our freshwater fisheries.     

Climate change impacts on ecosystem functioning: evidence from an Empetrum heathland

? The extent to which plants exert an influence over ecosystem processes, such as nitrogen cycling and fire regimes, is still largely unknown. It is also unclear how such processes may be dependent on the prevailing environmental conditions. ? Here, we applied mechanistic models of plant-environment interactions to palaeoecological time series data to determine the most likely functional relationships of Empetrum (crowberry) and Betula (birch) with millennial-scale changes in climate, fire activity, nitrogen cycling and herbivore density in an Irish heathland. ? Herbivory and fire activity preferentially removed Betula from the landscape. Empetrum had a positive feedback on fire activity, but the effect of Betula was slightly negative. Nitrogen cycling was not strongly controlled by plant population dynamics. Betula had a greater temperature-dependent population growth rate than Empetrum; thus climate warming promoted Betula expansion into the heathland and this led to reduced fire activity and greater herbivory, which further reinforced Betula dominance. ? Differences in population growth response to warming were responsible for an observed shift to an alternative community state with contrasting forms of ecosystem functioning. Self-reinforcing feedback mechanisms--which often protect plant communities from invasion--may therefore be sensitive to climate warming, particularly in arctic regions that are dominated by cold-adapted plant populations.