Abstracts on Global Climate Change 2004

Modelling and measuring the spectral bidirectional reflectance factor of snow-covered sea ice: an intercomparison study

Broadband albedo is a very important geophysical parameter in the Earth surface-atmosphere interaction in either global climate change or hydrological cycle and snowmelt runoff studies. To derive the broadband albedo accurately from satellite optical sensor observation at limited bands and at a single observation angle, the bidirectional reflectance factor (BRF) has to be specified quantitatively. In the present albedo derivation algorithms from the satellite radiance data, the BRF is either modelled or observed. Questions may arise as to how well a BRF model can be in the broadband albedo derivation. To help answer such questions, we studied the performance of a snow-surface BRF model for two specific cases under large solar zenith angles (65degrees and 85degrees). We measured snow-surface spectral directional reflectance under clear skies. The snow physical properties, such as snow grain size and snow density, at the same sites were also measured. In situ snow physical data are used to simulate the snow-surface BRF and hemispherical directional reflectance factor (HDRF) through a multilayered azimuth- and zenith-dependent plane-parallel radiative transfer model. The field measurements and BRF and HDRF simulations all reveal the forward-scattering nature of snow surface under large solar incidence angles, but the BRF model results depict the strongest forward-scattering patterns under such solar zenith angles. Because the HDRF is simulated through coupling of the surface BRF with radiative transfer in the atmosphere, the resulting HDRF patterns agree with the field measurements better than the simulated BRF does. The deviation of the simulated HDRF from field-based clear-sky directional reflectance (FCDR) is within +/- 10% for the central (viewing zenith angle <45degrees) and lateral sides of the viewing hemisphere. This level of agreement between the simulated HDRF and FCDR also implies that the simulated BRF model can provide remote-sensing estimates of spectral albedo with an uncertainty of +/- 10% for the same part of the viewing hemisphere. Further improvement in BRF model performance requires better handling of single scattering properties of snow grains, surface roughness, and atmospheric correction. Also, better procedures and techniques in field measurement are necessary for more accurate assessment of the performance of BRF models. Copyright (C) 2004 John Wiley Sons, Ltd.

Paleoclimate and faunal evolution in the Plio-Pleistocene of Africa and South America

PALEOCLIMATE AND FAUNAL EVOLUTION IN THE PLIO-PLEISTOCENE OF AFRICA AND SOUTH AMERICA. Climatic change is often hypothesized to be a major variable in forcing evolutionary change. Recent work on Pliocene and Pleistocene fossil mammals from the Turkana Basin of Kenya and Ethiopia shows that climate may play an important role in the spread of savanna environments, and thus in the increasing abundance of mammals adapted to open and seasonally and conditions. If global climate change is behind some of these trends in East Africa, we hypothesize that similar patterns of faunal change may occur elsewhere. An analysis of fossil mammals from the Pampean region of Argentina shows an increase in the number of species adapted to open and seasonally and conditions through the Plio-Pleistocene. The South American pattern is not identical to the East African pattern, but both show a significant increase in open and and adapted mammals shortly after 2 million years ago, at the very beginning of the Pleistocene. Although global climate change may be invoked as a common cause of these intercontinental trends, local and regional geography and tectonics play a critical role in modulating the global signal.

Geographical potential of Argentine ants (Linepithema humile Mayr) in the face of global climate change

Determining the spread and potential geographical distribution of invasive species is integral to making invasion biology a predictive science. We assembled a dataset of over 1000 occurrences of the Argentine ant (Linepithema humile), one of the world’s worst invasive alien species. Native to central South America, Argentine ants are now found in many Mediterranean and subtropical climates around the world. We used this dataset to assess the species’ potential geographical and ecological distribution, and to examine changes in its distributional potential associated with global climate change, using techniques for ecological niche modelling. Models developed were highly predictive of the species’ overall range, including both the native distributional area and invaded areas worldwide. Despite its already widespread occurrence, L. humile has potential for further spread, with tropical coastal Africa and southeast Asia apparently vulnerable to invasion. Projecting ecological niche models onto four general circulation model scenarios of future (2050s) climates provided scenarios of the species’ potential for distributional expansion with warming climates: generally, the species was predicted to retract its range in tropical regions, but to expand at higher latitude areas.

The impact of surface-adsorbed phosphorus on phytoplankton Redfield stoichiometry

The Redfield ratio of 106 carbon: 16 nitrogen: 1 phosphorus in marine phytoplankton(1) is one of the foundations of ocean biogeochemistry, with applications in algal physiology(2), palaeoclimatology(3) and global climate change(4). However, this ratio varies substantially in response to changes in algal nutrient status(5) and taxonomic affiliation(6,7). Here we report that Redfield ratios are also strongly affected by partitioning into surface-adsorbed and intracellular phosphorus pools. The C: N: surface-adsorbed P (80 - 105 C: 15 - 18 N: 1 P) and total (71 - 80 C: 13 - 14 N: 1 P) ratios in natural populations and cultures of Trichodesmium were close to Redfield values and not significantly different from each other. In contrast, intracellular ratios consistently exceeded the Redfield ratio ( 316 - 434 C: 59 - 83 N: 1 intracellular P). These high intracellular ratios were associated with reduced N-2 fixation rates, suggestive of phosphorus deficiency. Other algal species also have substantial surface-adsorbed phosphorus pools, suggesting that our Trichodesmium results are generally applicable to all phytoplankton. Measurements of the distinct phytoplankton phosphorus pools may be required to assess nutrient limitation accurately from elemental composition. Deviations from Redfield stoichiometry may be attributable to surface adsorption of phosphorus rather than to biological processes, and this scavenging could affect the interpretation of marine nutrient inventories and ecosystem models.

Initial public perceptions of deep geological and oceanic disposal of carbon dioxide

Two studies were conducted to gauge likely public perceptions of proposals to avoid releasing carbon dioxide from power plants to the atmosphere by injecting it into deep geological formations or the deep ocean. Following a modified version of the mental model interview method, Study 1 involved face-to-face interviews with 18 nontechnical respondents. Respondents shared their beliefs after receiving basic information about the technologies and again after getting specific details. Many interviewees wanted to frame the issue in the broader context of alternative strategies for carbon management, but public understanding of mitigation strategies is limited. The second study, administered to a sample of 126 individuals, involved a closed-form survey that measured the prevalence of general beliefs revealed in study 1 and also assessed the respondent’s views of these technologies. Study results suggest that the public may develop misgivings about deep injection of carbon dioxide because it can be seen as temporizing and perhaps creating future problems. Ocean injection was seen as more problematic than geological injection. An approach to public communication and regulation that is open and respectful of public concerns is likely to be a prerequisite to the successful adoption of this technology.

Evolution of late glacial ice-marginal lakes on the northwestern Canadian Shield and their influence on the location of the Dubawnt Lake palaeo-ice stream

During deglaciation of the North American Laurentide Ice Sheet large proglacial lakes developed in positions where proglacial drainage was impeded by the ice margin. For some of these lakes, it is known that subsequent drainage had an abrupt and widespread impact on North Atlantic Ocean circulation and climate, but less is known about the impact that the lakes exerted on ice sheet dynamics. This paper reports palaeogeographic reconstructions of the evolution of proglacial lakes during deglaciation across the northwestern Canadian Shield, covering an area in excess of 1,000,000 km(2) as the ice sheet retreated some 600 km. The interactions between proglacial lakes and ice sheet flow are explored, with a particular emphasis on whether the disposition of lakes may have influenced the location of the Dubawnt Lake ice stream. This ice stream falls outside the existing paradigm for ice streams in the Laurentide Ice Sheet because it did not operate over fined-grained till or lie in a topographic trough. Ice margin positions and a digital elevation model are utilised to predict the geometry and depth of proglacial takes impounded at the margin at 30-km increments during deglaciation. Palaeogeographic reconstructions match well with previous independent estimates of lake coverage inferred from field evidence, and results suggest that the development of a deep lake in the Thelon drainage basin may have been influential in initiating the ice stream by inducing calving, drawing down ice and triggering fast ice flow. This is the only location alongside this sector of the ice sheet where large (>3000 km(2)), deep lakes (similar to120 m) are impounded for a significant length of time and exactly matches the location of the ice stream. It is speculated that the commencement of calving at the ice sheet margin may have taken the system beyond a threshold and was sufficient to trigger rapid motion but that once initiated, calving processes and losses were insignificant to the functioning of the ice stream. It is thus concluded that proglacial lakes are likely to have been an important control on ice sheet dynamics during deglaciation of the Laurentide Ice Sheet. (C) 2004 Elsevier B.V. All rights reserved.

RNA/DNA ratios as indicators of metabolic activity in four species of Caribbean reef-building corals

Global climate change and the anthropogenic degradation of tropical reef environments can have deleterious consequences for the health of reef-building corals. Bioindicators of coral status aid in efforts to identify those species and populations that are most threatened, which can help focus conservation efforts. The RNA/DNA ratio is an index of protein synthetic capacity and is expected to reflect an organism’s investment in growth. Here, we measured a decrease in the RNA/DNA ratio in both the symbiotic anemone Aiptasia pallida exposed to light-deprivation in the laboratory, and in natural populations of the coral Porites astreoides along a depth gradient, suggesting that the RNA/DNA ratio may have depended upon metabolic activity. Also, RNA/DNA ratios in the coral Montastraea annularis were higher in the winter and spring (when higher growth rates may have been supported) than in summer, at an inshore and an offshore reef in the Florida Keys. Site-specific disparity in bleaching patterns at these 2 reefs may partly explain the differences in their RNA/DNA ratios. Finally, significant interspecific variation was observed in 3 co-occurring species of the genus Montastraea: M. annularis, M. cavernosa and M, faveolata, demonstrating the potential for variability in protein synthetic capacity even between closely related species. These results support the use of the RNA/DNA ratio as an indicator of metabolic activity in natural populations of corals.

The influence of the global climate change on the forest ecosystems in the low tatras Mts

The paper presents the results of possible regional effects of global climate change on the tree species composition of mountain forest ecosystems. Our model area has been represented by the valleys: Vajskova and Lomnista in Low Tatras Mts region. The suitability of the current and future changed climatic conditions for particular species has been assessed by means of the analysis of the bioclimatic area of each examined tree species. The analysis has been done for the tree species as follows: Norway spruce (Picea abies), silver fir (Abies alba), European beech (Fagus sylvatica), mountain pine (Pinus mugo), sycamore maple (Acer pseudoplatanus), European ash (Fraxinus excelsior), European larch (Larix decidua), mountain ash (Sorbus aucuparia) and cembra pine (Pinus cembra). The results hint at the possibility of considerable changes in the tree composition of mountain forests in the future. The climatic changes will probably have a negative impact primarily on silver fir, Norway spruce and mountain pine - important commercial and stand building species, The effects of the climatic changes are also expected on other species.

Will OPEC lose from the Kyoto Protocol?

A range of energy-economy models forecast losses to members of the Organisation of Petroleum Exporting Countries (OPEC) should the Kyoto Protocol come into force. These forecasts are a powerful influence in the United Nations Framework Convention on Climate Change negotiations. They are used by OPEC to advance the agenda on the impacts of response measures, covertly arguing for compensation for lost oil revenues arising from implementation of the Protocol. This paper discusses this issue, and explores the key assumptions of these models and their uncertainties. Assumptions about carbon leakage, future availability of oil reserves, substitution, innovation, and capital turnover are considered. The paper suggests that losses will not affect OPEC countries equally, and that these losses are not likely to be as substantial as the models forecast. A range of policy measures are proposed to lessen any impact the Protocol may have on OPEC. (C) 2003 Elsevier Ltd. All rights reserved.

Declining extent of open-water refugia for top predators in Baffin Bay and adjacent waters

Global climate change is expected to severely impact Arctic ecosystems, yet predictions of impacts are complicated by region-specific patterns and nonuniform trends. Twentyfour open-water overwintering areas (or “microhabitats”) were identified to be of particular importance for eight seabird and marine mammal species in the eastern Canadian High Arctic and Baffin Bay. Localized trends in the available fraction of open-water were examined in March during 1979-2001, derived from approximate sea ice concentrations from satellite-based microwave telemetry. Declines in the fraction of open-water were identified at microhabitats in Baffin Bay, Davis Strait, coastal West Greenland, and Lancaster Sound. Increases in open-water were observed in Hudson Bay, Hudson Strait, and Foxe Basin. The biological importance of each microhabitat was examined based on species distribution and abundance. Potential consequences of reduced open-water for top marine predators include impacts on foraging efficiency and oxygen and prey availability.

Are climate change impacts already affecting tropical forest biomass?

Tropical forests contain large stocks of carbon and any change in the balance of inflows and outflows of carbon to the biomass of standing forest has potentially important consequences for the global carbon cycle and related greenhouse warming, as well as for tropical biodiversity. Despite unresolved controversies over observed changes in biomass and gas fluxes, current observations indicate the likelihood that additional climate change would have substantial impacts on tropical forests and would reinforce their contributions to global climate change. Climate change impacts are already affecting tropical forest biomass. (C) 2004 Elsevier Ltd. All rights reserved.

New evidence for a volcanically, tectonically, and climatically active Mars

Geological analysis of Mars imagery supports the hypothesis that the planet has been the site of recent (< 10 Ma) volcanic and tectonic processes and glacier flow, and makes most likely previous suggestions of continuing endogenic and exogenic activity. Tectonic structures which deform very slightly cratered (at MOC scales) surfaces of Tharsis Montes and surrounding regions Seem to attest to active tectonism (both extensional and transcurrent) on Mars. Exogenic processes in this region, such as a glacial origin for the aureole deposits on the northwestern flanks of the Tharsis Montes shield volcanoes, are supported by new data. The very recent age of these structures could be the first direct confirmation that drastic changes in obliquity are modulating the martian climate, such that an increase in obliquity would result in equatorial glaciers taking the place of the receding polar ice caps. If this and other concurring research is extended and confirmed. the ‘alive Mars’ Which would emerge would constitute a most appealing place for exobiology and comparative planetology. (C) 2004 Elsevier Inc. All rights reserved.

Impact analysis of climate change for an Alpine catchment using high resolution dynamic downscaling of ECHAM4 time slices

Global climate change affects spatial and temporal patterns of precipitation and so has a major impact on surface and subsurface water balances. While global climate models are designed to describe climate change on global or continental scales, their resolution is too coarse for them to he suitable for describing regional climate change. Therefore, regional climate models are applied to downscale the coarse meteorological fields to a much higher spatial resolution to take account of regional climate phenomena. The changes of atmospheric state due to regional climate change must be translated into surface and sub-surface water fluxes so that the impact on water balances in specific catchments can be investigated. This can be achieved by the coupled regional climatic/hydrological simulations presented here. The non-hydrostatic regional climate model MCCM was used for dynamic downscaling for two time slices of a global climate model Simulation with the GCM ECHAM4 (IPCC scenario IS92a, ‘business as usual) from 2.8 degrees x 2.8 degrees to 4 x 4 km(2) resolution for the years 1991-1999 and 203 1-2039. This allowed derivation of detailed maps showing changes in precipitation and temperature in a region of southern Germany and the central Alps. The performance of the downscaled ECHAM4 to reproduce the seasonality of precipitation in central Europe for the recent climate was investigated by comparison with dynamically downscaled ECMWF reanalyses in 20 x 20 km2 resolution. The downscaled ECHAM4 Fields underestimate precipitation significantly in summer. The ratio of mean monthly downscaled ECHAM4 and ECMWF, precipitation showed little variation. so it was used to adjust the course of precipitation for the ECHAM4/MCCM fields before it was applied in the hydrological model. The high resolution meteorological fields were aggregated to 8-hour time steps and applied to the distributed hydrological model WaSiM to simulate the water balance of the alpine catchment of the river Ammer (c. 700 km(2)) at 100 x 100 m(2) resolution. To check the reliability of the Coupled regional climatic/hydrological simulation results for the recent climate, they were compared with those of a station-based hydrological simulation for the period 1991-1999. This study shows the changes in the temperature and precipitation distributions in the catchment from the recent climate to the future climate scenario and how these will affect the frequency distribution of runoff.

Solving the climate problem - Technologies available to curb CO2 emissions

In an effort to avoid serious ecological disruption and global climate change,low-carbon energy strategies need to be implemented on a world-wide scale along with the introduction of carbon policies and carbon management.

Long-term changes in migration timing of adult Atlantic salmon (Salmo salar) at the southern edge of the species distribution

The Connecticut River historically represented the southernmost extent of the North American range of Atlantic salmon (Salmo salar), but the native population was extirpated 200 years ago by dam construction. An extensive restoration effort has relied upon stock transfers from more northerly rivers, especially the Penobscot River (Maine). Recent work has shown differences in age structure between donor and derivative populations. Here we focus on a related life-history trait, the timing of the adult migration. We examined 23 years of migration timing data collected at two capture locations in the Connecticut River drainage. We found that both dates of first capture and median capture dates have shifted significantly earlier by about 0.5 days(.)year(-1). To conclude whether this is a consequence of local adaptation or a coast-wide effect, we also quantified changes in migration timing of more northerly stocks (in Maine and Canada). We found that the changes in migration timing were not unique to the Connecticut River stock and instead observed coherent patterns in the shift towards earlier peak migration dates across systems. These consistent shifts are correlated with long-term changes in temperature and flow and may represent a response to global climate change.

The Earth Simulator: roles and impacts

The Earth Simulator Research Project started in March 2002 with the primary objective of producing reliable prediction data for global climate change. Within a couple of months after the start of operation, the Earth Simulator achieved an amazing performance of 35.86 Teraflops (about 90% of the peak performance of 40.96 Teraflops) in the Linpack benchmark test and, more surprisingly, 26.58 Teraflops for a typical application program of global atmospheric circulation model (called AFES) with a horizontal resolution of 10km. These facts ensure us that the real contribution of the Earth Simulator be far greater than originally expected. Undoubtedly, the Earth Simulator would work to make a paradigm shift in science, industry, and human thinking, as well as finding the best human’s wisdom to keep a sustainable symbiotic relationship with nature. (C) 2004 Elsevier B.V. All rights reserved.

Changes in lagoonal marsh morphology at selected northeastern Atlantic coast sites of significance to migratory waterbirds

Five lagoonal salt marsh areas, ranging from 220 ha to 3,670 ha, were selected from Cape Cod, Massachusetts to the southern DelMarVa peninsula, Virginia, USA to examine the degree to which Spartina marsh area and microhabitats had changed from the early or mid- 1900s to recent periods. We chose areas based on their importance to migratory bird populations, agency concerns about marsh loss and sea-level rise, and availability of historic imagery. We georeferenced and processed aerial photographs from a variety of sources ranging from 1932 to 1994. Of particular interest were changes in total salt marsh area, tidal creeks, tidal flats, tidal and non-tidal ponds, and open water habitats. Nauset Marsh, within Cape Cod National Seashore, experienced an annual marsh loss of 0.40% (19% from 1947 to 1994) with most loss attributed to sand overwash and conversion to open water. At Forsythe National Wildlife Refuge in southern New Jersey, annual loss was 0.27% (17% from 1932 to 1995), with nearly equal attribution of loss to open water and tidal pond expansion. At Curlew Bay, Virginia, annual loss was 0.20% (9% from 1949 to 1994) and almost entirely due to perimeter erosion to open water. At Gull Marsh, Virginia, a site chosen because of known erosional losses, we recorded the highest annual loss rate, 0.67% per annum, again almost entirely due to erosional, perimeter loss. In contrast, at the southernmost site, Mockhorn Island Wildlife Management Area, Virginia, there was a net gain of 0.09% per annum (4% from 1949 to 1994), with tidal flats becoming increasingly vegetated. Habitat. implications for waterbirds are considerable; salt marsh specialists such as laughing gulls (Larus atricilla), Forster’s terns (Sterna forsteri), black rail, (Laterallus jamaicensis), seaside sparrow (Ammodramus maritimus), and saltmarsh sharp-tailed sparrow (Ammodramus caudacutus) are particularly at risk if these trends continue, and all but the laughing gull are species of concern to state and federal managers.

Mineral stress: the missing link in understanding how global climate change will affect plants in real world soils

Many natural and agricultural ecosystems are characterized by sub-optimal availability of mineral nutrients and ion toxicities. Mineral stresses are likely to have important, complex, and poorly understood interactions with global climate change variables. For example, most terrestrial vegetation is supported by weathered soils with some combination of low P, low Ca, Al toxicity, and Mn toxicity. Each of these stresses has complex, yet distinct, interactions with global change variables, making it very difficult to predict how plants in these environments will respond to future climate scenarios. Important, yet poorly understood, interactions include the effects of transpiration on root acquisition of soluble nutrients, particularly Ca and Si, the effects of altered root architecture on the acquisition of immobile nutrients, particularly P, the effects of altered root exudate production on Al toxicity and transition metal acquisition, and the interaction of photochemical processes with transition metal availability. The interaction of Mn toxicity with light intensity and other global change variables is discussed as an example of the complexity and potential importance of these relationships. Current conceptual models of plant response to multiple resource limitations are inadequate. Furthermore, substantial genetic variation exists in plant responses to mineral stress, and traits improving adaptation to one stress may incur tradeoffs for adaptation to other stresses. Root traits under quantitative genetic control are of central importance in adaptation to many mineral stresses. An integration of quantitative genetics with mechanistic and conceptual models of plant response to mineral stresses is needed if we are to understand plant response to global change in real-world soils. (C) 2004 Elsevier B.V. All rights reserved.

Genomics and the physiologist: bridging the gap between genes and crop response

Plant physiologists have traditionally studied the relationship between crop performance (the phenotype) and the environment. Global change processes present multiple challenges to crop performance that can be met effectively by changing the crop environment through management, and by modifying the crop genome (the genotype) through plant breeding and molecular biology. In order to increase the reliability of crop performance prediction based upon genetic information, new tools are needed to more effectively relate observed phenotypes to genotypes. The emerging discipline of genomics offers promise of providing such tools, and may provide a unique opportunity to enhance genetic gains and stabilize global crop production. Genomics has developed from the confluence of genetics, automated laboratory tools for generating DNA- and RNA-based data, and methods of information management. Functional genomics concentrates on how genes function, alone and in networks, while structural genomics focuses on physical and structural aspects of the genome. The traditional strengths of physiology lie in interpreting whole plant response to environmental signals, dissecting traits into component processes, and predicting correlated responses when genes and pathways are perturbed. These complement information on the genetic control of signal transduction, gene expression, gene networks and candidate genes. Combining physiological and genetic information can provide a more complete model of gene-to-phenotype relationships and genotype-by-environment interactions. Phenotypic screening procedures that more accurately identify underlying genetic variation, and crop models that incorporate Mendelian genetic controls of key processes provide two tangible examples of fruitful collaboration between physiologists and geneticists. These point to a productive complementary relationship between disciplines that will speed progress towards stable and adequate food production, despite challenges posed by global climate change. (C) 2004 Published by Elsevier B.V.

Improving drought tolerance in maize: a view from industry

Significant yield losses in maize (Zea mays L.) from drought are expected to increase with global climate change as temperatures rise and rainfall distribution changes in key traditional production areas. The success of conventional crop improvement over the past 50 years for drought tolerance forms a baseline against which new genetic methods must be compared. Selection based on performance in multi-environment trials (MET) has increased grain yield under drought through increased yield potential and kernel set, rapid silk exertion, and reduced barrenness, though at a lower rate than under optimal conditions. Knowledge of the physiology of drought tolerance has been used to dissect the trait into a series of key processes. This has been complemented by genetic dissection through the identification of QTL associated with these same traits. Both have been used to identify suitable organ- and temporal-specific promoters and structural genes. Phenotyping capacity has not kept pace with the exponential increase in genotypic knowledge, and large-scale managed stress environments (MSE) are now considered essential to further progress. These environments provide ideal settings for conducting massively parallel transcript profiling studies, and for validating candidate regions and genes. Genetic and crop physiological models of key processes are now being used to confirm the value of traits for target environments, and to suggest efficient breeding strategies. Studies of gene to phenotype relationships suggest that most putative drought tolerance QTL identified thus far are likely to have limited utility for applied breeding because of their dependency on genetic background or their sensitivity to the environment, coupled with a general lack of understanding of the biophysical bases of these context dependencies. Furthermore, the sample of weather conditions encountered during progeny selection within the multi environment testing of conventional breeding programs can profoundly affect allele frequency in breeding populations and the stress tolerance of elite commercial products. We conclude that while gains in kernels per plant can be made by exploiting native genetic variation among elite breeding lines, improvements in functional stay-green or in root distribution and function may require additional genetic variation from outside the species. Genomic tools and the use of model plants are considered indispensable tools in this search for new ways of optimizing maize yield under stress. (C) 2004 Elsevier B.V. All rights reserved.

Dynamics of carbon sequestration in a coastal wetland using radiocarbon measurements

[ 1] Coastal wetlands are sensitive to global climate change and may play an important role in the global carbon cycle. However, the dynamics of carbon ( C) cycling in coastal wetlands and its response to sea level change associated with global warming is still poorly understood. In this study, we estimated the long-term and short-term rates of C accumulation, using C and C isotopic measurements of peat cores collected along a soil chronosequence, in a coastal wetland in north Florida. The long-term C accumulation rates determined by examining the C inventory and the radioactive decay of radiocarbon as a function of depth in the peat cores decrease with time from -130 +/- 9 g C/m(2)/yr over the last century to -13 +/- 2 g C/m(2)/yr over the millennium timescale. The short-term C accumulation rates estimated by examining the differences in the radiocarbon and C contents of the surfacial peat between archived ( 1985, 1988) and present ( 1996 and 1997) samples range from 42 to 193 g C/m(2)/yr in low marsh, from 18 to 184 g C/m(2)/yr in middle marsh, and from -50 to 181 g C/m(2)/yr in high marsh. The high end-values of our estimated short-term C accumulation rates are comparable to the estimated rates of C sequestration in coastal wetlands reported by Chmura et al. [ 2003], but are significantly higher than our estimated long-term rates in the marshes and are also much higher than the published rates of C sequestration in northern peatlands. The higher recent rates of C accumulation in coastal marshes, in comparison with the longer-term rates, are due to slow but continuous decomposition of organic matter in the peat over time. However, other factors such as increased primary production in the coastal wetland over the last decades or century, due to a rise in mean sea level and/or CO2 and nitrogen fertilization effect, could also have contributed to the large difference between the recent and longer-term rates. Our data indicate that salt marshes in this area have been and continue to be a sink for atmospheric carbon dioxide. Because of higher rates of C sequestration and lower CH4 emissions, coastal wetlands could be more valuable C sinks per unit area than other ecosystems in a warmer world.

Heat stress induces different forms of cell death in sea anemones and their endosymbiotic algae depending on temperature and duration

Bleaching of reef building corals and other symbiotic cnidarians due to the loss of their dinoflagellate algal symbionts (=zooxanthellae), and/or their photosynthetic pigments, is a common sign of environmental stress. Mass bleaching events are becoming an increasingly important cause of mortality and reef degradation on a global scale, linked by many to global climate change. However, the cellular mechanisms of stress-induced bleaching remain largely unresolved. In this study, the frequency of apoptosis-like and necrosis-like cell death was determined in the symbiotic sea anemone Aiptasia sp. using criteria that had previously been validated for this symbiosis as indicators of programmed cell death (PCD) and necrosis. Results indicate that PCD and necrosis occur simultaneously in both host tissues and zooxanthellae subject to environmentally relevant doses of heat stress. Frequency of PCD in the anemone endoderm increased within minutes of treatment. Peak rates of apoptosis-like cell death in the host were coincident with the timing of loss of zooxanthellae during bleaching. The proportion of apoptosis-like host cells subsequently declined while cell necrosis increased. In the zooxanthellae, both apoptosis-like and necrosis-like activity increased throughout the duration of the experiment (6 days), dependent on temperature dose. A stress-mediated PCD pathway is an important part of the thermal stress response in the sea anemone symbiosis and this study suggests that PCD may play different roles in different components of the symbiosis during bleaching.

Investigation of plasma irregularity sources associated with charged dust in the earth’s mesosphere

Noctilucent clouds (NLCs) and polar mesospheric summer echoes (PMSEs) are two phenomena at the forefront of near earth space science. NLCs are high altitude clouds in the earth’s mesosphere that are formed from aerosol particles. The increase in the occurence of NLCs over time is believed to have profound implications on global climate change. PMSEs are believed to be related to NLCs and are strong radar echoes from mesospheric turbulence in the 50 MHz to 1.3 GHz range. Currently, there is no universally accepted explanation for the irregularities thought to produce PMSEs. Recent simultaneous sounding rocket, radar, and lidar observations of NLCs and PMSEs have provided a more detailed description of the electrodynamics and plasma configuration inside NLCs and the relationship to PMSEs. Particularly important is the simultaneous observation of charged aerosols, electron depletions, and small-scale electric field irregularities in the PMSE generation region. This work considers the consequences of the recent experimental observations on ultimately understanding the generation mechanism for PMSEs and the relationship to NLCs. A model for the electrodynamics and plasma configuration in the charged aerosol boundary layer will be described that indicates that plasma flows are expected to exist in the equilibrium. The possible role of these plasma flows in producing electron turbulence and irregularities in the charged aerosol boundary layer that may ultimately result in PMSEs is discussed. (C) 2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

The response of two Glomus mycorrhizal fungi and a fine endophyte to elevated atmospheric CO2, soil warming and drought

Plantago lanceolata plants were grown under various environmental conditions in association with the mycorrhizal fungi Glomus mosseae, G. caledonium and a fine endophyte either individually or all together. Using a time-course approach, we investigated the effects of elevated atmospheric CO2 (eCO(2)), soil warming and drought and their interactions on root length colonized (RLC) by mycorrhizal fungi and extraradical mycorrhizal hyphal (EMH) production. Plant growth responded as would be expected to the environmental manipulations. There was no plant growth-independent effect of eCO(2) on mycorrhizal colonization; however, EMH production was stimulated by eCO(2), i.e. there was increased partitioning of below-ground carbon to the EMH. Soil warming directly stimulated both percent RLC by the Glomus species and EMH density; soil warming did not affect RLC by the fine endophyte. Drought decreased percent RLC for the fine endophyte, but not for the Glomus species. The presence of one mycorrhizal fungus did not affect the response of another to the environmental variables. There was no evidence of any interactive effects of the environmental variables on RLC, but there were significant environmental interactions on EMH production. In particular, the stimulatory effects of eCO(2) and soil warming on EMH density were not additive. The results are discussed in terms of the soil carbon cycle, highlighting some crucial gaps in our knowledge. If future environmental changes affect mycorrhizal fungal turnover and respiration, then this could have important implications for the terrestrial carbon cycle.

The impact of global climate change on tropical forest biodiversity in Amazonia

Aim To model long-term trends in plant species distributions in response to predicted changes in global climate. Location Amazonia. Methods The impacts of expected global climate change on the potential and realized distributions of a representative sample of 69 individual Angiosperm species in Amazonia were simulated from 1990 to 2095. The climate trend followed the HADCM2GSa1 scenario, which assumes an annual 1% increase of atmospheric CO2 content with effects mitigated by sulphate forcing. Potential distributions of species in one-degree grid cells were modelled using a suitability index and rectilinear envelope based on bioclimate variables. Realized distributions were additionally limited by spatial contiguity with, and proximity to, known record sites. A size-structured population model was simulated for each cell in the realized distributions to allow for lags in response to climate change, but dispersal was not included. Results In the resulting simulations, 43% of all species became non-viable by 2095 because their potential distributions had changed drastically, but there was little change in the realized distributions of most species, owing to delays in population responses. Widely distributed species with high tolerance to environmental variation exhibited the least response to climate change, and species with narrow ranges and short generation times the greatest. Climate changed most in north-east Amazonia while the best remaining conditions for lowland moist forest species were in western Amazonia. Main conclusions To maintain the greatest resilience of Amazonian biodiversity to climate change as modelled by HADCM2GSa1, highest priority should be given to strengthening and extending protected areas in western Amazonia that encompass lowland and montane forests.

Interpretation of Arctic aerosol properties using cluster analysis applied to observations in the Svalbard area

Atmospheric aerosols play an important role in global climate change, directly through radiative forcing and indirectly through their effect on cloud properties. Numerous measurements have been performed in the last three decades in order to characterize polar aerosols. Information about aerosol characteristics is needed to calculate induced changes in the Earth’s heat balance. However, this forcing is highly variable in space and time. Accurate quantification of forcing by aerosols will require combined efforts, assimilating information from different sources such as satellite, aircraft and surface-based observations. Adding to the complexity of the problem is that the measurements themselves are often not directly comparable as they vary in spatial/temporal resolution and in the basic properties of the aerosol that they measure. Therefore it is desirable to close the gap between the differences in temporal and spatial resolution and coverage among the observational approaches. In order to keep the entire information content and to treat aerosol variability in a consistent and manageable way an approach has to be achieved which enables one to combine these data. This study presents one possibility for linking together a complex Arctic aerosol data set in terms of parameters, timescale and place of measurement as well as meteorological parameters. A cluster analysis was applied as a pattern recognition technique. The data set is classified in clusters and expressed in terms of mean statistical values, which represent the entire database and its variation. For this study, different time-series of microphysical, optical and chemical aerosol parameters as well as meteorological parameters were analysed. The database was obtained during an extensive aerosol measurement campaign, the ASTAR 2000 (Arctic Study of Tropospheric Aerosol and Radiation) field campaign, with coordinated simultaneous ground-based and airborne measurements in the vicinity of Spitsbergen (Svalbard). Furthermore, longterm measurements at two ground-based sites situated at different altitudes were incorporated into the analysis. The approach presented in this study allows the necessary linking of routine long-term measurements with short-term extensive observations. It also involves integration of intermittent vertical aerosol profile measurements. This is useful for many applications, especially in climate research where the required data coverage is large.

Decomposition of soil and plant carbon from pasture systems after 9 years of exposure to elevated CO2: impact on C cycling and modeling

Elevated atmospheric CO2 may alter decomposition rates through changes in plant material quality and through its impact on soil microbial activity. This study examines whether plant material produced under elevated CO2 decomposes differently from plant material produced under ambient CO2. Moreover, a long-term experiment offered a unique opportunity to evaluate assumptions about C cycling under elevated CO2 made in coupled climate-soil organic matter (SOM) models. Trifolium repens and Lolium perenne plant materials, produced under elevated (60 Pa) and ambient CO2 at two levels of N fertilizer (140 vs. 560 kg ha(-1) yr(-1)), were incubated in soil for 90 days. Soils and plant materials used for the incubation had been exposed to ambient and elevated CO2 under free air carbon dioxide enrichment conditions and had received the N fertilizer for 9 years. The rate of decomposition of L. perenne and T. repens plant materials was unaffected by elevated atmospheric CO2 and rate of N fertilization. Increases in L. perenne plant material C : N ratio under elevated CO2 did not affect decomposition rates of the plant material. If under prolonged elevated CO2 changes in soil microbial dynamics had occurred, they were not reflected in the rate of decomposition of the plant material. Only soil respiration under L. perenne, with or without incorporation of plant material, from the low-N fertilization treatment was enhanced after exposure to elevated CO2. This increase in soil respiration was not reflected in an increase in the microbial biomass of the L. perenne soil. The contribution of old and newly sequestered C to soil respiration, as revealed by the C-13-CO2 signature, reflected the turnover times of SOM-C pools as described by multipool SOM models. The results do not confirm the assumption of a negative feedback induced in the C cycle following an increase in CO2, as used in coupled climate-SOM models. Moreover, this study showed no evidence for a positive feedback in the C cycle following additional N fertilization.

Is climate change affecting wolf populations in the High Arctic?

Gobal climate change may affect wolves in Canada’s High Arctic (80degrees N) acting through three trophic levels (vegetation, herbivores, and wolves). A wolf pack dependent on muskoxen and arctic hares in the Eureka area of Ellesmere Island denned and produced pups most years from at least 1986 through 1997. However, when summer snow covered vegetation in 1997 and 2000 for the first time since records were kept, halving the herbivore nutrition-replenishment period, muskox and hare numbers dropped drastically, and the area stopped supporting denning wolves through 2003. The unusual weather triggering these events was consistent with global-climate-change phenomena.

Climate change and the distribution of climatic resources for tourism in North America

Tourism is a major sector of the global economy, and it is strongly influenced by climate. At some travel destinations, climate represents the natural resource on which the tourism industry is predicated. Global climate change has the potential to alter the distribution of climate assets among tourism destinations, with implications for tourism seasonality, demand and travel patterns. Changes in the length and quality of the tourism season have considerable implications for the long-term profitability of tourism enterprises and competitive relationships between destinations. This analysis utilizes a ‘tourism climate index’ (TCI) that incorporates 7 climate variables relevant to general tourism activities (i.e. sightseeing) to assess the spatial and temporal distribution of climate resources for tourism in North America under baseline conditions (1961-1990) and 2 climate change scenarios (CGCM2-B2 and HadCM3-A1F1) for the 2050s and 2080s. The analysis found that a substantive redistribution of climate resources for tourism will be possible in the later decades of the 21st century, particularly in the warmer and wetter HadCM3-A1F1 scenario. The number of cities in the USA with ‘excellent’ or’ ideal’ TCI ratings (TCI > 80) in the winter months is likely to increase, so that southern Florida and Arizona could face increasing competition for winter sun holiday travelers and the seasonal ‘snowbird’ market (retirees from Canada and the northern states of the USA, who spend 2 to 6 mo in winter peak and optimal climate destinations). In contrast, lower winter TCI ratings in Mexico suggest it could become less competitive as a winter sun holiday destination. In Canada, a longer and improved warm-weather tourism season may enhance its competitiveness in the international tourism marketplace, with potentially positive implications for its current international tourism account deficit.

Effect of elevated CO2 concentration and vapour pressure deficit on isoprene emission from leaves of Populus deltoides during drought

To further our understanding of the influence of global climate change on isoprene production we studied the effect of elevated [CO2] and vapour pressure deficit (VPD) on isoprene emission rates from leaves of Populus deltoides Bartr. during drought stress. Trees, grown inside three large bays with atmospheres containing 430, 800, or 1200 mumol mol(-1) CO2 at the Biosphere 2 facility, were subjected to a period of drought during which VPD was manipulated, switching between low VPD ( approximately 1 kPa) and high VPD ( approximately 3 kPa) for several days. When trees were not water-stressed, elevated [CO2] inhibited isoprene emission and stimulated photosynthesis. Isoprene emission was less responsive to drought than photosynthesis. As water-stress increased, the inhibition of isoprene emission disappeared, probably as a result of stomatal closure and the resulting decreases in intercellular [CO2] (C-i). This assumption was supported by increased isoprene emission under high VPD. Drought and high VPD dramatically increased the proportion of assimilated carbon lost as isoprene. When measured at the same [CO2], leaves from trees grown at ambient [CO2] always had higher isoprene emission rates than the leaves of trees grown at elevated [CO2], demonstrating that CO2 inhibition is a long-term effect.

Vulnerability of waterborne diseases to climate change in Canada: A review

This project addresses two important issues relevant to the health of Canadians: the risk of waterborne illness and the health impacts of global climate change. The Canadian health burden from waterborne illness is unknown, although it presumably accounts for a significant proportion of enteric illness. Recently, large outbreaks with severe consequences produced by E. coli O157:H7 and Cryptosporidium have alarmed Canadians and brought demands for political action. A concurrent need to understand the health impacts of global climate changes and to develop strategies to prevent or prepare for these has also been recognized. There is mounting evidence that weather is often a factor in triggering waterborne disease outbreaks. A recent study of precipitation and waterborne illness in the United States found that more than half the waterborne disease outbreaks in the United States during the last half century followed a period of extreme rainfall. Projections of international global climate change scenarios suggest that, under conditions of global warming most of Canada may expect longer summers, milder winters, increased summer drought, and more extreme precipitation. Excess precipitation, floods, high temperatures, and drought could affect the risk of waterborne illness in Canada. The existing scientific information regarding most weather-related adverse health impacts and on the impacts of global climate change on health in Canada is insufficient for informed decision making. The results of this project address this need through the investigation of the complex systemic interrelationships between disease incidence, weather parameters, and water quality and quantity, and by projecting the potential impact of global climate change on those relationships.

The potential distribution of zebra mussels in the United States

The range expansion of zebra mussels (Dreissena polymorpha) in North America has been rapid and costly in both economic and ecological terms. joint social, political, and scientific ventures such as the 100th Meridian Initiative aim to reduce the spread of zebra mussels by eliminating the unintended transport of the species and preventing its westward expansion. Here we forecast the potential distribution of zebra mussels in the United States by applying a machine-learning algorithm for nonparametric prediction of species distributions (genetic algorithm for rule-set production, or GARP) to data about the current distribution of zebra mussels in the United States and 11 environmental and geological covariates. Our results suggest that much of the American West will be uninhabitable for zebra mussels. Nonetheless, some catchments along the West Coast and in the southeastern United States exhibit considerable risk of invasion and should be monitored carefully. Possible propagule dispersal to these places should be managed proactively.

Responses of foraminiferal isotopic variations at ODP Site 1143 in the southern South China Sea to orbital forcing

The foraminiferal delta(18)O and delta(13)C records for the past 5 Ma at ODP Site 1143 reveal the linear responses of the Plio-Pleistocene climatic changes in the southern South China Sea to orbital forcing at the obliquity and precession bands. The phase of the 5180 variations with the orbital forcing is opposite to that of the delta(13)C, which may be caused by the frequent El Nino events from the equatorial Pacific. The amplification of the Northern Hemisphere Ice Sheet at similar to3.3 Ma probably affected the development of the 100-ka climatic cycles. Its further spreading may spur the 100-ka climatic cycle to become the dominant cycle in the late Pleistocene. The “Mid-Pleistocene Transition” event has localized influence on the isotopic variations in the southern South China Sea. The foraminiferal delta(13)C records for the past 5 Ma at Site 1143 are highly coherent with the orbital forcing at the long eccentricity band, and lead the delta(18)O records at the shorter eccentricity band, highlighting the importance of the carbon cycle in the global climate change.

Can climate data from METEOSAT improve wildlife distribution models?

Global climate change generated by human activities is likely to affect agroecosystems in several ways: reinforcing intensification in northern and western Europe, and extensification in the Mediterranean countries. If we are to predict the consequences of global warming for wildlife, distribution models have to include climate data. The METEOSAT temporal series from EWBMS offers an attractive alternative to using climatic surfaces derived from ground stations. The aim of this paper is to test whether this climatic satellite data can improve the distribution models obtained previously by Suarez-Seoane et al. using habitat variables for three agro-steppe bird species: great bustard, little bustard and calandra lark in Spain. Rainfall, radiation balance, evapotranspiration and soil moisture images were incorporated together with the other variables used as predictors in the published stepwise GAM models. Changes in the predicted distributions from the habitat only and climate-habitats models were assessed by reference to the CORINE land cover categories. Inclusion of climatic variables from METEOSAT led to statistically superior models for all three species. There were large differences in the climatic variables selected and the original variables dropped among the species. Evapotranspiration variables were the most frequently selected. Maps of the differences between the habitat and climate-habitat models showed very different patterns for the three species. Inclusion of climate variables led to a wider range of land cover types being deemed suitable. Despite the statistical superiority of models, care is needed in deciding whether to use climatic variables because they may emphasize the fundamental rather than the realized niche. Used together, however, habitat and climate models can provide new insights into factors limiting species distributions and how they may respond to climate change.

Age-related environmental sensitivity and weather mediated nestling mortality in white storks Ciconia ciconia

We studied environmental sensitivity and mortality related to weather inclemency in white stork nestlings Ciconia ciconia in their southern European boundary (Donana, SW Spain). The study of homeothermy acquisition and fault bars (i.e. a measure of stress on feathers) revealed that stork nestlings were specially sensitive to environmental conditions occurring before 20 d of age. Accordingly, most of nestling mortality concentrated during this sensitive period: 91% of deaths corresponded to nestlings younger than 20 d, 73% concentrating on nestlings up to 10 d-old. Nestling mortality and total breeding failure were highly variable among years, being especially high when rainy periods coincided with the early live of nestlings (between 1 April and 15 May). Maximum temperatures had a positive correlation with breeding success and nestling survival but this effect disappeared when controlling for rainfall. Our results are in agreement with previous studies conducted in other white stork populations in other latitudes. We suggest that this could be the result of a low homeothermy capacity of young nestlings jointly with an early breeding phenology that expose white storks to rain, but not to high temperatures. In the context of global climate change we suggest that the current decrease on spring rainfall could increase nestling survival while punctual rainy springs could have a negative effect on the reproduction of white storks.

PARAGON - An integrated approach for characterizing aerosol climate impacts and environmental interactions

Aerosols exert myriad influences on the earth’s environment and climate, and on human health. The complexity of aerosol-related processes requires that information gathered to improve our understanding of climate change must originate from multiple sources, and that effective strategies for data integration need to be established. While a vast array of observed and modeled data are becoming available, the aerosol research community currently lacks the necessary tools and infrastructure to reap maximum scientific benefit from these data. Spatial and temporal sampling differences among a diverse set of sensors, nonuniform data qualities, aerosol mesoscale variabilities, and difficulties in separating cloud effects are some of the challenges that need to be addressed. Maximizing the long-term benefit from these data also requires maintaining consistently well-understood accuracies as measurement approaches evolve and improve. Achieving a comprehensive understanding of how aerosol physical, chemical, and radiative processes impact the earth system can be achieved only through a multidisciplinary, inter-agency, and international initiative capable of dealing with these issues. A systematic approach, capitalizing on modern measurement and modeling techniques, geospatial statistics methodologies, and high-performance information technologies, can provide the necessary machinery to support this objective. We outline a framework for integrating and interpreting observations and models, and establishing an accurate, consistent, and cohesive long-term record, following a strategy whereby information and tools of progressively greater sophistication are incorporated as problems of increasing complexity are tackled. This concept is named the Progressive Aerosol Retrieval and Assimilation Global Observing Network (PARAGON). To encompass the breadth of the effort required, we present a set of recommendations dealing with data interoperability; measurement and model integration; multisensor synergy; data summarization and mining; model evaluation; calibration and validation; augmentation of surface and in situ measurements; advances in passive and active remote sensing; and design of satellite missions. Without an initiative of this nature, the scientific and policy communities will continue to struggle with understanding the quantitative impact of complex aerosol processes on regional and global climate change and air quality.

Nitrogen input mediates the effect of free-air CO2 enrichment on mycorrhizal fungal abundance

Plots containing Lolium perenne L., Trifolium repens L. or a mixture of both plant species were exposed to elevated atmospheric CO2 (eCO(2)) for 10 consecutive seasons using free-air CO2 enrichment technology at ETH Zurich, Switzerland. The CO2 treatment was crossed with a two-level nitrogen (N) fertilization treatment. In the tenth year, soil samples were collected on three occasions through the growing season to assess the impact of eCO(2) and N fertilization on mycorrhizal fungal abundance. Soil moisture content, which varied with harvest date, was linked to the vegetation type and was higher under eCO(2). Root weight density was affected by vegetation type: lower for clover, higher for grass. Root weight density was stimulated by eCO(2) and decreased by high N fertilization. The percent root length colonized by mycorrhizal fungi was lowest in the clover plots and highest in the grass plots. High N significantly decreased root length colonized. There was no overall effect of eCO(2) on root length colonized; however, there was a significant eCO(2)x N interaction: eCO(2) increased root length colonized at high N, but decreased root length colonized at low N. Extraradical mycorrhizal hyphal density was linked to soil moisture content. Extraradical mycorrhizal hyphal density was not affected by eCO(2) or high N individually, but as for root length colonized, there was a significant eCO(2)x N interaction: eCO(2) increased extraradical mycorrhizal hyphal density at low N but not at high N. These environmental effects on root colonization and external mycorrhizal hyphae were independent of soil moisture content and root weight density. This field study demonstrated a significant mediating effect of N fertilization on the response of arbuscular mycorrhizal fungi to eCO(2) irrespective of any change in root biomass.

Risk and climate change: Perceptions of key policy actors in Canada

This article examines factors that predict perceptions of risk associated with global climate change. The research focuses on the perceptions of those associated with climate change policy making in the prairie region of Canada. The data are from an online survey (n = 851) of those policy actors. The analysis integrates several dominant approaches to the study of risk perception: psychometric approaches that examine the effects of cognitive structure; demographic assessments that examine, for example, differences in perception based on gender or family status; and political approaches that suggest that one’s position in the policy process may affect his or her perceived risk. Attitudes toward climate change are to a degree predicted by all of these factors, but only when indirect effects are observed. Sociodemographic characteristics have little direct effect on perceived risk, but do affect general beliefs that affect risk perceptions. Perceived risk is related more strongly to these general beliefs or world views than to more specific beliefs about the effects of climate change on weather patterns. Position within the policy process also contributes to our understanding of perceptions, with industry and governmental actors demonstrating similar attitudes, which contrast with environmental groups and university researchers.

Divergent pheromone-mediated insect behaviour under global atmospheric change

While the effects of global atmospheric changes on vegetation and resulting insect populations(‘bottom-up interactions’) are being increasingly studied, how these gases modify interactions among insects and their natural enemies (‘top-down interactions’) is less clear. As natural enemy efficacy is governed largely by behavioural mechanisms, altered prey finding and prey defence may change insect population dynamics. Here we show that pheromone-mediated escape behaviours, and hence the vulnerability of insects to natural enemies, are divergent under atmospheric conditions associated with global climate change. Chaitophorus stevensis, a common aphid on trembling aspen trees, Populus tremuloides, have diminished escape responses in enriched carbon dioxide (CO2) environments, while those in enriched ozone (O-3) have augmented escape responses, to alarm pheromone. These results suggest that divergent pheromone-mediated behaviours could alter predator-prey interactions in future environments.

Municipal heat wave response plans

Approximately 400 people die from extreme heat each year in the United States, and the risk of heat waves may increase as a result of global climate change. Despite the risk of heat-related morbidity and mortality, many cities lack written heat response plans. In a review of plans from 18 cities at risk for heat-related mortality, we found that many cities had inadequate or no heat response plans. This is an important area for further investigation and government attention.

Sea level rise affecting the Vietnamese Mekong Delta: Water elevation in the flood season and implications for rice production

In this study, we assessed the impact of sea level rise, one of the most ascertained consequences of global climate change, for water levels in the Vietnamese Mekong Delta (VMD). We used a hydraulic model to compute water levels from August to November-when flooding is presently critical-under sea level rise scenarios of 20 cm (= Delta20) and 45 cm (= Delta45), respectively. The outputs show that the contour lines of water levels will be shifted up to 25 km (Delta20) and 50 km (Delta45) towards the sea due to higher sea levels. At the onset of the flood season ( August), the average increment in water levels in the Delta is 14.1 cm (Delta20) and 32.2 cm (Delta45), respectively. At the peak of the flood season ( October), high discharge from upstream attenuates the increment in water level, but average water level rise of 11.9 cm (Delta20) and 27.4 cm (Delta45), respectively, still imply a substantial aggravation of flooding problems in the VMD. GIS techniques were used to delineate areas with different levels of vulnerability, i.e., area with high (2.3 mio ha = 60% of the VMD), medium (0.6 mio ha = 15%) and low (1 mio ha = 25%) vulnerability due to sea level rise. Rice production will be affected through excessive flooding in the tidally inundated areas and longer flooding periods in the central part of the VMD. These adverse impacts could affect all three cropping seasons, Mua (main rainfed crop), Dong Xuan (Winter-Spring) and He Thu (Summer-Autumn) in the VMD unless preventive measures are taken.

Predicting the distribution of ground beetle species (Coleoptera, Carabidae) in Britain using land cover variables

Predictions of plant and animal species distributions are important for conservation and for the assessment of large-scale ecosystem change. Land cover data are becoming more widely available for use in land management and conservation. We use a logistic regression modelling approach to investigate the utility of these data for modelling. The relationship between the distribution of 137 British ground beetles species and land cover was investigated using data from 1687 10 kin national grid squares. Land cover data were simplified using ordination and the axes used as predictors in logistic regression with presence absence data for individual beetle species as response variables. Significant regression models were generated for all species with first and second axis scores. The amounts of variation explained by models were generally low, but predictions derived from models generally matched the known distributions of the species in Britain. Species with coastal preferences were poorly modelled and predicted to occur throughout lowland Britain whilst a number of species occurring in southern Britain were predicted to occur into Scotland. A validation exercise comparing model predictions with new data from a survey of 59 10 km(2) produced mixed results with the distribution of grassland species being better predicted than riverine species. Jackknifing was used to assess the robustness of models for four species which differed in their apparent responses to the land cover variables. Methods for improving the predictive power of these models and their potential for use in assessing the impact of global climate change are discussed. (C) 2004 Elsevier Ltd. All rights reserved.

Wind-mediated diel variation in flow speed in a Jamaican back reef environment: Effects on ecological processes

The movement of water plays an important role in a number of physiological (e.g., metabolic rate, nutrient uptake) and ecological (e.g., foraging, fertilization) processes for coral reef organisms. In the back reef of Discovery Bay, Jamaica, daytime mean flow speeds were on average, 61% greater than at night during a given 24 hr period. Wind speed was a significant predictor of flow speed in these shallow water environments, with the variation in wind speed able to explain 30% of the variation in flow speed. Porter’s (1985) yearlong wind speed record in Discovery Bay indicated that the time of maximum daily wind speed occurred during daylight hours for 93% of the year. Activity of the fireworm, Hermodice carunculata (Pallas, 1766), represented by total abundance in six, 1 x 30 m transects was negatively correlated with flow speed. Atmospheric and oceanographic conditions enhancing wind-dependent water flow in back reef environments include prevalent tradewinds and negligible tidal currents, which suggests that the diel variation in flow speed documented for Discovery Bay may be a common phenomenon in similar environments. Such predictable environmental variability may be an important selective agent shaping the evolution of diel rhythms of reef invertebrates and algae. Therefore, recent atmospheric and climatological shifts (e.g., frequency of El Nino events, global climate change) may exert additional selective pressure on the organisms found in these environments.

Estimating burned area for Tropical Africa for the year 1990 with the NOAA-NASA Pathfinder AVHRR 8km land dataset

The international scientific community recognizes the long-term monitoring of biomass burning as important for global climate change, vegetation disturbance and land cover change research on the Earth’s surface. Although high spatial resolution satellite images may offer a more detailed view of land surfaces, their limited area coverage and temporal sampling have restricted their use to local research rather than global monitoring. Low spatial resolution images provide an invaluable source for the detection of burned areas in vegetation cover (scars) at global scale along time. However, the automated burned area mapping algorithm applicable at continental or global scale must be sufficiently robust to accommodate the global variation in burned scar signals. Here, the estimation of the percentage of a pixel area affected by a fire is crucial. In a first step, an empirical method is used which is based on a function between the change in Normalized Difference Vegetation Index (NDVI) and the surface area affected by fire. Next, a new statistical method, based on the Monte Carlo algorithm, is applied to compute probabilities of burned pixels percentages in different neighbourhood conditions.

Neighbour identity modifies effects of elevated temperature on plant performance in the High Arctic

Competition among plants in extreme environments such as the High Arctic has often been described as unimportant, or even nonexistent; environmental factors are thought to overrule any negative plant-plant interactions. However, few studies have actually addressed this question experimentally in the Arctic, and those that did found only little evidence for competition. Such species interactions will presumably become more important in the future, as Global Climate Change takes effect on terrestrial ecosystems. We investigated plant-plant interactions in the High Arctic, following the growth of Luzula confusa and Salix polaris in pure and mixed stands, and under elevated-temperature treatment over 2 years. To understand the mechanisms of competition, a parallel experiment was undertaken in phytotrons, manipulating competition, temperature and nutrient availability. Our findings indicate that competition is acting in the natural vegetation, and that climatic warming will alter the balance of interactions in favour of the dwarf shrub S. polaris. The phytotron experiment suggested that the mechanism is a higher responsiveness of Salix to nutrient availability, which increased under warming in the field. While Luzula showed a positive response to higher temperature in the lab, its performance in mixed stands in the field was actually reduced by warming, indicating a competitive repression of growth by Salix. The growth of Salix was also reduced by the presence of Luzula, but it was still able to profit from warming. Our findings suggest that climatic warming will result in greater shrub dominance of High Arctic tundra, but we also conjecture that grazing could reverse the situation to a graminoid-dominated tundra. These two divergent scenarios would have different implications for ecosystem feedbacks to climatic change.

Variation in climate warming along the migration route uncouples arrival and breeding dates

Migratory species are of special concern in the face of global climate change, since they may be affected by changes in the wintering area, along the migration route and at the breeding grounds. Here we show that migration and breeding times of a trans-Saharan migrant, the pied flycatcher Ficedula hypoleuca, closely follow local temperatures along the migration route and at the breeding grounds. Because of differences in long-term temperature trends of short within-spring periods, the migration period and the time interval between migration and breeding dates of this species have extended in SW Finland. Temperatures in northern parts of Central Europe have risen at the time when the first migrants arrive there, facilitating their migration northward. Temperatures later in the spring have not changed, and the last individuals arrive at the same time as before. The timing of breeding has not advanced because temperatures at the breeding site after arrival have not changed. These results show that the pied flycatchers can speed up their migration in response to rising temperatures along the migration route. Our results strongly indicate that the effects of climate change have to be studied at the appropriate time and geographical scales for each species and population concerned.

Climate change: Conflict of observational science, theory, and politics

Debate over whether human activity causes Earth climate change obscures the immensity of the dynamic systems that create and maintain climate on the planet. Anthropocentric debate leads people to believe that they can alter these planetary dynamic systems to prevent what they perceive as negative climate impacts on human civilization. Although politicians offer simplistic remedies, such as the Kyoto Protocol, global climate continues to change naturally. Better planning for the inevitable dislocations that have followed natural global climate changes throughout human history requires us to accept the fact that climate will change, and that human society must adapt to the changes. Over the last decade, the scientific literature reported a shift in emphasis from attempting to build theoretical models of putative human impacts on climate to understanding the planetwide dynamic processes that are the natural climate drivers. The current scientific literature is-beginning to report the history of past climate change, the extent of natural climate variability, natural system drivers, and the episodicity of many climate changes. The scientific arguments have broadened from focus upon human effects on climate to include the array of natural phenomena that have driven global climate change for eons. However, significant political issues with long-term social consequences continue their advance. This paper summarizes recent scientific progress in climate science and arguments about human influence on climate.

Coral reefs in a century of rapid environmental change

Coral reefs are the most diverse marine ecosystem and embrace possibly millions of plant, animal and protist species. Mutualistic symbioses are a fundamental feature of coral reefs that have been used to explain their structure, biodiversity and existence. Complex inter-relationships between hosts, habitats and symbionts belie closely coupled nutrient and community dynamics that create the circumstances for “something from nothing” (or the “oasis in a nutrient desert”). The flip side of these dynamics is a close dependency between species, which results in a series of non-linear relationships as conditions change. These responses are being highlighted as anthropogenic influences increase across the world’s tropical and subtropical coastlines. Caribbean as well as Indo-Pacific coral populations are now in a serious decline in many parts of the world. This has resulted in a significant reorganization of how coral reef ecosystems function. Among the spectra of changes brought about by humans is rapid climate change. Mass coral bleaching - the loss of the dinoflagellate symbionts from reef-building corals - and mortality has affected the world’s coral reefs with increasing frequency and intensity since the late 1970s. Mass bleaching events, which often cover thousands of square kilometres of coral reefs, are triggered by small increases (+1-3degreesC) in water temperature. These increases in sea temperature are often seen during warm phase weather conditions (e.g. ENSO) and are increasing in size and magnitude. The loss of living coral cover (e.g. 16% globally in 1998, an exceptionally warm year) is resulting in an as yet unspecified reduction in the abundance of a myriad of other species. Projections from general circulation models (GCM) used to project changes in global temperature indicate that conditions even under the mildest greenhouse gas emission scenarios may exceed the thermal tolerances of most reef-building coral communities. Research must now explore key issues such as the extent to which the thermal tolerances of corals and their symbionts are dynamic if bleaching and disease are linked; how the loss of high densities of reef-building coral will affect other dependent species; and, how the loss of coral populations will affect the millions of people globally who depend on coral reefs for their daily survival.

High-resolution vegetation and climate change associated with Pliocene Australopithecus afarensis

Plio-Pleistocene global climate change is believed to have had an important influence on local habitats and early human evolution in Africa. Responses of hominin lineages to climate change have been difficult to test, however, because this procedure requires well documented evidence for connections between global climate and hominin environment. Through high-resolution pollen data from Hadar, Ethiopia, we show that the hominin Australopithecus afarensis accommodated to substantial environmental variability between 3.4 and 2.9 million years ago. A large biome shift, up to 5degreesC cooling, and a 200- to 300-mm/yr rainfall increase occurred just before 3.3 million years ago, which is consistent with a global marine delta(18)O isotopic shift.

The gypsy moth life stage model: landscape-wide estimates of gypsy moth establishment using a multi-generational phenology model

A multi-generational model of gypsy moth phenology was developed from existing literature and used to assess the risk of establishment of this exotic pest across North America based on the suitability of 4457 locations in satisfying the temperature requirements for seasonal development. Approximately 595 million hectares of North America is estimated to be climatically suitable for gypsy moth establishment. Limits to the potential range exist in the southern United States because of limits to diapause development, and in northern Canada because of slower prediapause and larval development. A 1.5 degreesC increase in mean daily maximum and minimum temperatures, as might occur with global climate change, would result in a range expansion in the north, a range contraction in the south, and a net increase in range of approximately 16%. The model is described and the probable limitations to establishment are discussed. Crown Copyright (C) 2004 Published by Elsevier B.V. All rights reserved.

Environmental magnetic record of paleoclimate change from the Eocene-Oligocene stratotype section, Massignano, Italy

A high-resolution environmental magnetic study of the Massignano section, Italy (Global Stratotype Section and Point for the Eocene-Oligocene boundary), has been performed to test whether a clear magnetic signature associated with climatic change is recognizable in this record. Our results reveal the existence of alternating intervals with high and low magnetic mineral concentrations similar to the pattern of rock magnetic property variations observed from an environmental magnetic study of the CIROS-1 sediment core from Antarctica. These results suggest that an external forcing mechanism drove the sedimentary response to global climate change prior to the major Oi-1 cooling event at the Eocene-Oligocene boundary.

Nitrate assimilation in plant shoots depends on photorespiration

Photorespiration, a process that diminishes net photosynthesis by approximate to25% in most plants, has been viewed as the unfavorable consequence of plants having evolved when the atmosphere contained much higher levels of carbon dioxide than it does today. Here we used two independent methods to show that exposure of Arabidopsis and wheat shoots to conditions that inhibited photorespiration also strongly inhibited nitrate assimilation. Thus, nitrate assimilation in both dicotyledonous and monocotyledonous species depends on photorespiration. This previously undescribed role for photorespiration (i) explains several responses of plants to rising carbon dioxide concentrations, including the inability of many plants to sustain rapid growth under elevated levels of carbon dioxide; and (h) raises concerns about genetic manipulations to diminish photorespiration in crops.

Larval salamander response to uv radiation and predation risk: Color change and microhabitat use

Adaptations to avoid or cope with harmful ultraviolet radiation (UVR) have evolved in many amphibian species. Sublethal levels of UVR can select for simple responses in larval amphibians, such as dark pigmentation or preference for UVR-protected microhabitats (i.e., under cover or in deep water). This Study focuses on color response to UVR, and whether avoidance behaviors like refuge use and depth choice depend on larval body color. We quantified responses to ambient levels of UVR in four experiments in semi-field conditions using two sister species of salamander larvae that differ in their evolutionary history of UVR exposure. Both Ambystoma barbouri and A. texanum larvae darkened in response to UVR, and when given the choice of refuge, significantly increased the proportion of time spent in hiding. Additionally, both species used deeper microhabitats when exposed to UVR, but only A. barbouri larvae showed a preference for shallow waters when UVR was blocked out. Neither of these behaviors seemed to be color dependent, with larvae from both species taking refuge and preferring deep water in the presence of UVR, regardless of body color. Interesting behavioral trade-offs arose when larvae were confronted with conflicting selection pressures from UVR and predation risk. Risk from predatory fish forces larvae to shallow areas, while UVR forces larvae into deeper water. Thus, the combination of the two selection pressures creates a conflict in optimal depth choice. Faced with this conflict, A. barbouri preferred deeper, risky areas to shallow water with high UVR exposure. Ambystoma texanum responded to predation risk with a preference for shallow water, but did not significantly alter depth in response to UVR. Given the opportunity to mediate exposure to UVR and predation risk by altering depth choices, neither species changed color in response to either UVR or predation risk. Overall, these changes in behavior and color may affect larval feeding, competition, and predation rates and could thus alter aquatic community structure.

Biodiversity, biosphere reserves, and the big apple - A study of the New York Metropolitan Region

The objectives of this article were to assess the dimensions of biodiversity-urban society interactions within the New York Metropolitan Region, a 31-county area with a population of 21.5 million, and to explore pathways to reconcile dysfunctional relationships between these two ever-entwined systems. The article builds on the premise that urban biodiversity exists at a crucial nexus of ecological and societal interactions, linking local, regional, and global scales, and that urban ecologies are projected to become even more dynamic in the future, particularly as a result of global climate change. The pathway proposed to reconcile the biodiversity-urban society relationships is the incorporation of biosphere reserve strategies into regional environmental planning efforts focused on the New York/New Jersey Harbor/Estuary specifically and on the greater New York Metropolitan Region in general. The concepts of the “ecological footprint” and vulnerability to global environmental change are used to analyze the current interactions between biodiversity and urban society, and to evaluate the efficacy of adopting biosphere reserve strategies in the region. New York has long been at the forefront of American environmentalism and landscape planning. Coupled with this history is a still small but growing interest in regional environmental planning efforts (e.g., the U.S. EPA Harbor Estuary Program) and green infrastructure (e.g., the 2002 Humane Metropolis Conference organized by the Ecological Cities Project). The research presented here aims to contribute to these nascent activities. As a megacity, New York may serve as a model for other major cities of the world.

Photosynthetic down-regulation over long-term CO2 enrichment in leaves of sour orange (Citrus aurantium) trees

Understanding how trees are affected by a long-term increase in atmospheric CO2 is crucial to understanding the future impact of global climate change. Measurements of photosynthetic characteristics were made in sour orange trees (Citrus aurantium) growing under an enhanced CO2 atmosphere and N-replete soil for 14 yr to determine whether photosynthetic down-regulation had occurred. Photosynthesis, A : C-i gas exchange relationships and Rubisco activity and content were measured throughout the 14th year of the experiment. The CO2-induced enhancement ratio of photosynthesis was calculated and compared with estimates of the enhancement of cumulative wood biomass production. Content of the large subunit of Rubisco was significantly reduced by CO2 enrichment indicating that down-regulation had occurred. A high correlation between the CO2-induced enhancement of photosynthesis and the enhancement of cumulative wood biomass production suggested that the decline in wood biomass production was closely related to the decline in photosynthesis. These results indicate that long-term CO2 enrichment can result in photosynthetic down-regulation in leaves of trees, even under nonlimiting N conditions. (C) New Phytologist (2004). No claim to original US government works.

Response of different decomposer communities to the manipulation of moisture availability: potential effects of changing precipitation patterns

The potential impacts of changes in precipitation patterns associated with global climate change on the relationship between soil community diversity and litter decomposition were investigated. For a period of ca. 5 months, two decomposer communities in litterbags (1000 and 45 mum mesh size) containing spruce litter were subjected to two irrigation treatments: constant and fluctuating (drying/rewetting) moisture conditions. The latter were expected to induce moisture stress on the decomposer communities. The two mesh sizes were used to exclude different faunal components from the decomposer communities. The 1000 mum mesh excluded only the macrofauna, whereas the 45 mum mesh excluded both the macro- and mesofauna. In the short-term perspective of the present study, mesofauna abundance showed no response to imposed fluctuating moisture conditions. Irrespective of the presence of mesofauna, mass loss, microbial biomass and the control mechanisms, regulating carbon mineralization appeared unaffected by fluctuating moisture conditions. The reduction in the functional/structural diversity of the decomposer communities in the 45 mum litterbags resulted in strongly increased Nematoda abundance but it did not alter the response of Nematoda to fluctuating moisture conditions. Processes in the nitrogen (N)-cycle and mass loss were sensitive indicators of changes in the structural and functional complexity of decomposer communities. However, a negative effect of fluctuating moisture conditions on extractable N was coupled to the presence of mesofauna. Extremes in rainfall patterns, generated by climate change, may have a negative impact on the availability of nutrients, particularly N, for plants. This effect could be amplified by an additional impoverishment in the structural and functional complexity of the respective decomposer communities.

Global climate change and infectious disease

Cell death and degeneration in the symbiotic dinoflagellates of the coral Stylophora pistillata during bleaching

Rising sea temperatures are increasing the incidences of mass coral bleaching (the dissociation of the coral-algal symbiosis) and coral mortality. In this study, the effects of bleaching (induced by elevated light and temperature) on the condition of symbiotic dinoflagellates (Symbiodinium sp.) within the tissue of the hard coral Stylophora pistillata (Esper) were assessed using a suite of techniques. Bleaching of S. pistillata was accompanied by declines in the maximum potential quantum yield of photosynthesis (F-v/F-m, measured using pulse amplitude modulated [PAM] fluorometry), an increase in the number of Sytox-green-stained algae (indicating compromised algal membrane integrity and cell death), an increase in 2’,7’-dichlorodihydrofluroscein diacetate (H(2)DCFDA)stained algae (indicating increased oxidative stress), as well as ultrastructural changes (vacuolisation, losses of chlorophyll, and an increase in accumulation bodies). Algae expelled from S. pistillata exhibited a complete disorganisation of cellular contents; expelled cells contained only amorphous material. In situ samples taken during a natural mass coral bleaching event on the Great Barrier Reef in February 2002 also revealed a high number of Sytox-labelled algae cells in symbio. Dinoflagellate degeneration during bleaching seems to be similar to the changes resulting from senescence-phase cell death in cultured algae. These data support a role for oxidative stress in the mechanism of coral bleaching and highlight the importance of algal degeneration during the bleaching of a reef coral.

Identity and diversity of coral endosymbionts (zooxanthellae) from three Palauan reefs with contrasting bleaching, temperature and shading histories

The potential of corals to associate with more temperature-tolerant strains of algae (zooxanthellae, Symbiodinium) can have important implications for the future of coral reefs in an era of global climate change. In this study, the genetic identity and diversity of zooxanthellae was investigated at three reefs with contrasting histories of bleaching mortality, water temperature and shading, in the Republic of Palau (Micronesia). Single-stranded conformation polymorphism and sequence analysis of the ribosomal DNA internal transcribed spacer (ITS)1 region was used for genotyping. A chronically warm but partly shaded coral reef in a marine lake that is hydrographically well connected to the surrounding waters harboured only two single-stranded conformation polymorphism profiles (i.e. zooxanthella communities). It consisted only of Symbiodinium D in all 13 nonporitid species and two Porites species investigated, with the remaining five Porites harbouring C.. Despite the high temperature in this lake (> 0.5degrees above ambient), this reef did not suffer coral mortality during the (1998) bleaching event, however, no bleaching-sensitive coral families and genera occur in the coral community. This setting contrasts strongly with two other reefs with generally lower temperatures, in which 10 and 12 zooxanthella communities with moderate to low proportions of clade D zooxanthellae were found. The data indicate that whole coral assemblages, when growing in elevated seawater temperatures and at reduced irradiance, can be composed of colonies associated with the more thermo-tolerant clade D zooxanthellae. Future increases in seawater temperature might, therefore, result in an increasing prevalence of Symbiodinium phylotype D in scleractinian corals, possibly associated with a loss of diversity in both zooxanthellae and corals.

Quantifying the water vapour feedback associated with post-Pinatubo global cooling

There is an ongoing important debate about the role of water vapour in climate change. Predictions of future climate change depend strongly on the magnitude of the water vapour feedback and until now models have almost exclusively been relied upon to quantify this feedback. In this work we employ observations of water vapour changes, together with detailed radiative calculations to estimate the water vapour feedback for the case of the Mt. Pinatubo eruption. We then compare our observed estimate with that calculated from a relatively large ensemble of simulations from a complex coupled climate model. We calculate an observed water vapour feedback parameter of -1.6 Wm(-2) K-1, with uncertainty placing the feedback parameter between -0.9 to -2.5 Wm(-2) K-1. The uncertain is principally from natural climate variations that contaminate the volcanic cooling. The observed estimates are consistent with that found in the climate model, with the ensemble average model feedback parameter being -2.0 Wm(-2) K-1, with a 5-95% range of -0.4 to -3.6 Wm(-2) K-1 (as in the case of the observations, the spread is due to an inability to separate the forced response from natural variability). However, in both the upper troposphere and Southern Hemisphere the observed model water vapour response differs markedly from the observations. The observed range represents a 40%-400% increase in the magnitude of surface temperature change when compared to a fixed water vapour response and is in good agreement with values found in other studies. Variability, both in the observed value and in the climate model’s feedback parameter, between different ensemble members, suggests that the long-term water vapour feedback associated with global climate change could still be a factor of 2 or 3 different than the mean observed value found here and the model water vapour feedback could be quite different from this value; although a small water vapour feedback appears unlikely. We also discuss where in the atmosphere water vapour changes have their largest effect on surface climate.

Mycorrhizal fungi as drivers of ecosystem processes in heathland and boreal forest biomes

The importance of mycorrhizas in heathland and boreal forest biomes, which together cover much of the landmass of the Northern Hemisphere and store most of the global stocks of carbon, is reviewed. The taxonomic affinities of the organisms forming these symbiotic partnerships are assessed, and the distinctive structural features of the ericoid mycorrhizas of heathland dwarf shrubs and the ectomycorrhizas of boreal forest trees are described. It is stressed that neither in terms of the geographical distribution of the plants nor in terms of the occurrence of their characteristic mycorrhizas in the soil profile should these biomes be considered to be mutually exclusive. What unites them is their apparent affinity for acidic organic soils of inherently low accessibility of the major nutrients nitrogen (N) and phosphorus (P). These properties relate directly to the nature of the nutrient-poor recalcitrant litter produced by their host plants and through positive-feedback mechanisms that are reinforced by selective removal of labile nutrients by the mycorrhizas. We suggest that coevolution of these plant litter traits with mycorrhizal associations that are adapted to them has been one of the defining features of these ecosystems. Ericoid and ectomycorrhizal fungi have biochemical and physiological attributes that make them highly efficient at scavenging for organic sources of N and P in surface soil horizons. In so doing, they restrict supplies of these elements to the decomposer communities. Case studies involving exploitation of N and P in defined organic substrates are described. In both biomes the dominant plants depend upon the abilities of their fungal partners to recover nutrients, so the symbioses control nutrient cycles, productivity, species composition, and functioning of these ecosystems. It is in this context that the fungal symbionts are here considered to be drivers of nutritional processes in their respective biomes. Through their influences upon the quality of carbon residues mycorrhizal fungi must also affect the sink-source balance for this key element in soil. There is an urgent need for the evaluation of the relative contributions of symbiotic and saprotrophic components of the microflora to the processes of carbon storage and cycling in these biomes, particularly in the context of global climate change and impacts of anthropogenic pollutant N deposition.

Adaptation to temperate climates

Only model organisms live in a world of endless summer. Fitness at temperate latitudes reflects the ability of organisms in nature to exploit the favorable season, to mitigate the effects of the unfavorable season, and to make the timely switch from one life style to the other. Herein, we define fitness as Ry, the year-long cohort replacement rate across all four seasons, of the mosquito, Wyeomyia smithii, reared in its natural microhabitat in processor-controlled environment rooms. First, we exposed cohorts of W. smithii, from southern, midlatitude, and northern populations (30-50degreesN) to southern and northern thermal years during which we factored out evolved differences in photoperiodic response. We found clear evidence of evolved differences in heat and cold tolerance among populations. Relative cold tolerance of northern populations became apparent when populations were stressed to the brink of extinction; relative heat tolerance of southern populations became apparent when the adverse effects of heat could accumulate over several generations. Second, we exposed southern, midlatitude, and northern populations to natural, midlatitude day lengths in a thermally benign midlatitude thermal year. We found that evolved differences in photoperiodic response (1) prevented the timely entry of southern populations into diapause resulting in a 74% decline in fitness, and (2) forced northern populations to endure a warm-season diapause resulting in an 88% decline in fitness. We argue that reciprocal transplants across latitudes in nature always confound the effects of the thermal and photic environment on fitness. Yet, to our knowledge, no one has previously held the thermal year constant while varying the photic year. This distinction is crucial in evaluating the potential impact of climate change. Because global warming in the Northern Hemisphere is proceeding faster at northern than at southern latitudes and because this change represents an amelioration of the thermal environment and a concomitant increase in the duration of the growing season, we conclude that there should be more rapid evolution of photoperiodic response than of thermal tolerance as a consequence of global warming among northern, temperate ectotherms.

Elevated CO2 alters birch resistance to Lagomorpha herbivores

We studied the three-way interaction of elevated CO2, nitrogen (N), and temperature (T), and the two-way interaction of elevated CO2 and early-season defoliation on the secondary chemistry and resistance of Eurasian silver birch (Betula pendula) and North American paper birch (B. papyrifera) against the Eurasian hare (Lepus timidus) and the North American eastern cottontail rabbit (Sylvilagus floridanus), respectively. Elevated CO2 decreased the palatability of winter-dormant silver and paper birch stems to both hares and rabbits, respectively. But the effect on hares was only apparent at intermediate levels of N fertilization. Elevated T had no effect on palatability. The effects of elevated CO2, N, and T on levels of silver birch bark phenolics and terpenoids were dominated by two-way interactions between N and CO2, and N and T. Generally, however, N amendments elicited a parabolic response in carbon partitioning to most biosynthetic classes of silver birch phenolics (i.e. highest concentrations occurring at intermediate N). CO2 elevation was most enhancing at highest levels of N. On the other hand, T increases, more often than not, elicited reductions in phenolics, but especially so at the highest N level. In the case of B. papyrifera, elevated CO2 increased carbon partitioning to Folin-Denis stem and branch phenolics and condensed tannins. Early-season defoliation, on the other hand, had no effect on phenolics and tannins but lowered both N and energy levels of branches. Elevated CO2 substantially ameliorated the negative effects of severe defoliation on tree growth. These results support the hypothesis that continuing anthropogenic alterations of the atmosphere may trigger significant changes in plant phenotypic resistance to mammalian herbivores owing to an increasing net carbon balance between the highly vagile supply and demand capacities of plant carbon sources and sinks.

Determination of black carbon in natural organic matter by chemical oxidation and solid-state C-13 Nuclear Magnetic Resonance spectroscopy

Black carbon is an important component of natural organic matter that may play a significant role in global climate change. However, the complexity of natural organic matter has resulted in a milieu of methods and accompanying black carbon values that make it difficult to delineate the proportion of black carbon in soil and sedimentary total carbon budgets, Here we report on a chemical oxidation method that removes lignin and then facilitates black carbon to be estimated from solid-state C-13 Nuclear Magnetic Resonance (NMR) spectroscopy. The resulting black carbon values are lower in comparison to those reported by other researchers but may be a more accurate method for estimating black carbon in a range of natural organic matter samples from different environments. (C) 2004 Elsevier Ltd. All rights reserved.

Simulated long-term changes in river discharge and soil moisture due to global warming

By use of a coupled ocean-atmosphere-land model, this study explores the changes of water availability, as measured by river discharge and soil moisture, that could occur by the middle of the 21st century in response to combined increases of greenhouse gases and sulphate aerosols based upon the “IS92a” scenario. In addition, it presents the simulated change in water availability that might be realized in a few centuries in response to a quadrupling of CO2, concentration in the atmosphere. Averaging the results over extended periods, the radiatively forced changes, which are very similar between the two sets of experiments, were successfully extracted. The analysis indicates that the discharges from Arctic rivers such as the Mackenzie and Ob’ increase by up to 20% (of the pre-Industrial Period level) by the middle of the 21st century and by up to 40% or more in a few centuries. In the tropics, the discharges from the Amazonas and Ganga-Brahmaputra rivers increase substantially. However, the percentage changes in runoff from other tropical and many mid-latitude rivers are smaller, with both positive and negative signs. For soil moisture, the results of this study indicate reductions during much of the year in many semiarid regions of the world, such as the southwestern region of North America, the northeastern region of China, the Mediterranean coast of Europe, and the grasslands of Australia and Africa. As a percentage, the reduction is particularly large during the dry season. From middle to high latitudes of the Northern Hemisphere, soil moisture decreases in Summer but increases in winter.

The effects of infrared loading and water table on soil energy fluxes in northern peatlands

Increased radiative forcing is an inevitable part of global climate change, yet little is known of its potential effects on the energy fluxes in natural ecosystems. To simulate the conditions of global warming, we exposed peat monoliths (depth, 0.6 m; surface area, 2.1 m(2)) from a bog and fen in northern Minnesota, USA, to three infrared (IR) loading (ambient, +45, and +90 W m(-2)) and three water table (-16, -20, and -29 cm in bog and -1, -10 and -18 cm in fen) treatments, each replicated in three mesocosm plots. Net radiation (Rn) and soil energy fluxes at the top, bottom, and sides of the mesocosms were measured in 1999, 5 years after the treatments had begun. Soil heat flux (G) increased proportionately with IR loading, comprising about 3%-8% of Rn. In the fen, the effect of IR loading on G was modulated by water table depth, whereas in the bog it was not. Energy dissipation from the mesocosms occurred mainly via vertical exchange with air, as well as with deeper soil layers through the bottom of the mesocosms, whereas lateral fluxes were 10-20-fold smaller and independent of IR loading and water table depth. The exchange with deeper soil layers was sensitive to water table depth, in contrast to G, which responded primarily to IR loading. The qualitative responses in the bog and fen were similar, but the fen displayed wider seasonal variation and greater extremes in soil energy fluxes. The differences of G in the bog and fen are attributed to differences in the reflectance in the long waveband as a function of vegetation type, whereas the differences in soil heat storage may also depend on different soil properties and different water table depth at comparable treatments. These data suggest that the ecosystem-dependent controls over soil energy fluxes may provide an important constraint on biotic response to climate change.

Diurnal temperature range as an index of global climate change during the twentieth century

The usefulness of global-average diurnal temperature range (DTR) as an index of climate change and variability is evaluated using observations and climate model simulations representing unforced climate variability and anthropogenic climate change. On decadal timescales, modelled and observed intrinsic variability of DTR compare well and are independent of variations in global mean temperature. Observed reductions in DTR over the last century are large and unlikely to be due to natural variability alone. Comparison of observed and anthropogenic-forced model changes in DTR over the last 50 years show much less reduction in DTR in the model simulations due to greater warming of maximum temperatures in the models than observed. This difference is likely attributed to increases in cloud cover that are observed over the same period and are absent in model simulations.

Seasonal thermal signatures of heat transfer by water exchange in an underground vault

The temperature of a 10-point vertical profile at the rock-atmosphere interface has been monitored since 2000 September in an underground vault at Aburatsubo, Japan, where resistivity variations have been reported in association with earthquakes. The non-ventilated vault is characterized by an annual temperature variation of about 1.2degreesC peak to peak, compatible with thermal diffusion in the surrounding tuff rock, and by a long-term temperature increase of about 0.1degreesC per year, possibly due to a local or global climate change. Owing to a careful relative calibration of the 10 thermistors used in this experiment, these data establish that the ceiling temperature is higher than the floor temperature by 0.04 to 0.28degreesC. Transient temperature variations are observed in association with human presence or with typhoons, with a characteristic spatial pattern revealing structural heterogeneity. Variations with periods ranging from 1 day to 1 week, with an amplitude two time larger and a phase advance on the floor with respect to the ceiling, are observed from November to May. Variations with periods larger than 1 week, with an amplitude two times smaller and a phase lag on the floor with respect to the ceiling, are observed from June to October. These cycles are linked to the sign of the seasonal heat flux. We propose an interpretation in which heat transfer in the cavity is dominated by diffusion of water vapour from June to October (heat flux downwards, summer regime) and by convective water transport from November to May (heat flux upwards, winter regime). The water flow inferred from this model can be used to predict the water saturation of the rock as a function of time. Because of a permanent radiative heat flux from top to bottom, the upward water flow in the winter regime is larger than the downward water flow in the summer regime, resulting in a slow depletion of water from the rock below the cavity. This unbalanced water flow could contribute to an observed steady secular increase of rock resistivity, and possibly also to the long-term temperature increase of 0.1degreesC per year. It is important to understand these processes in the context of underground geophysical observatories, underground waste storage and contaminant transport, as well as for the preservation of cultural items such as cave paintings.

Reconstructing the Pleistocene geography of the Aphelocoma jays (Corvidae)

Understanding historical distributions of species and evolving lineages has been a topic of considerable interest, yet methods used to date have not provided detailed, quantitative distributional hypotheses. Here, we present a technique based on models of species’ ecological niches and Pleistocene climate reconstructions that provides such hypotheses, providing the example of reconstructions for the Aphelocoma jays. We demonstrate in general a greater degree than expected of stability in jay species’ distributional areas back through at least the most recent glaciation event, and that existing patterns of genetic differentiation may date to before the Late Pleistocene glaciations. More generally, the method offers the potential for reconstructing historical distributions of species or lineages, and providing a detailed geographic framework for addressing many biogeographic and systematic questions.

Scale-dependent climate signals drive breeding phenology of three seabird species

Breeding at the right time is essential for animals in seasonal climates in order to ensure that the energy demands of reproduction, particularly the nutritional requirements of growing young, coincide with peak food availability. Global climate change is likely to cause shifts in the timing of peak food availability, and in order to adapt successfully to current and future climate change, animals need to be able to adjust the time at which they initiate breeding. Many animals use environmental cues available before the breeding season to predict the seasonal peak in food availability and adjust their phenology accordingly. We tested the hypothesis that regulation of breeding onset should reflect the scale at which organisms perceive their environment by comparing phenology of three seabird species at a North Sea colony. As predicted, the phenology of two dispersive species, black-legged kittiwake (Rissa tridactyla) and common guillemot (Uria aalge), correlated with a large-scale environmental cue (the North Atlantic Oscillation), whereas a resident species, European shag (Phalacrocorax aristotelis), was more affected by local conditions (sea surface temperature) around the colony. Annual mean breeding success was lower in late years for European shags, but not for the other two species. Since correlations among climate patterns at different scales are likely to change in the future, these findings have important implications for how migratory animals can respond to future climate change.

Cadmium effects on mitochondrial function are enhanced by elevated temperatures in a marine poikilotherm, Crassostrea virginica Gmelin (Bivalvia : Ostreidae)

Marine intertidal mollusks, such as oysters, are exposed to multiple stressors in estuaries, including varying environmental temperature and levels of trace metals, which may interactively affect their physiology. In order to understand the combined effects of cadmium and elevated temperature on mitochondrial bioenergetics of marine mollusks, respiration rates and mitochondrial volume changes were studied in response to different cadmium levels (0-1000 mumol l(-1)) and temperatures (15, 25 and 35degreesC) in isolated mitochondria from the eastern oyster Crassostrea virginica acclimated at 15degreesC. It was found that both cadmium and temperature significantly affect mitochondrial function in oysters. Elevated temperature had a rate-enhancing effect on state 3 (ADP-timulated) and states 4 and 4+ (representative of proton leak) respiration, and the rate of temperature-dependent increase was higher for states 4 and 4+ than for state 3 respiration. Exposure of oyster mitochondria to 35degreesC resulted in a decreased respiratory control and phosphorylation efficiency (P/O ratio) compared to that of the-acclimation temperature (15degreesC), while an intermediate temperature (25degreesC) had no effect. Cadmium exposure did not lead to a significant volume change in oyster mitochondria in vitro. Low levels of cadmium (1-5 mumol l(-1)) stimulated the rate of proton leak in oyster mitochondria, while not affecting ADP-stimulated state 3 respiration. In contrast, higher cadmium levels (10-50 mumol l(-1)) had little or no effect on proton leak, but significantly inhibited state 3 respiration by 40-80% of the control rates. Elevated temperature increased sensitivity of oyster mitochondria to cadmium leading to an early inhibition of ADP-stimulated respiration and an onset of complete mitochondrial uncoupling at progressively lower cadmium concentrations with increasing temperature. Enhancement of cadmium effects by elevated temperatures suggests that oyster populations subjected to elevated temperatures due to seasonal warming or global climate change may become more susceptible to trace metal pollution, and vice versa.

Phasing of deglacial warming and laurentide ice sheet meltwater in the Gulf of Mexico

Evidence is emerging that the tropical climate system played a major role in global climate change during the last deglaciation. However, existing studies show that deglacial warming was asynchronous across the tropical band, complicating the identification of causal mechanisms. The Orca Basin in the northern Gulf of Mexico is ideally located to record subtropical Atlantic sea-surface temperature (SST) warming in relation to mellwater input from the Laurentide Ice Sheet. Paired delta(18)O and Mg/Ca data on the planktonic foraminifer Globigerinoides ruber from core EN32-PC6 are used to separate deglacial changes in SST and delta(18)O of seawater. SST as calculated from Mg/Ca data increased by >3 degreesC from ca. 17.2 to 15.5 ka in association with Heinrich event I and was not in phase with Greenland air temperature. Subtracting temperature effects from delta(18)O values in G. ruber reveals two excursions representing Laurentide meltwater input to the Gulf of Mexico, one of >1.5parts per thousand from ca. 16.1 to 15.6 ka and a second major spike of >2.5parts per thousand from ca. 15.2 to 13.0 ka that encompassed meltwater pulse 1A and peaked ca. 13.8 ka during the Bolling-Allerod. Conversion to salinity through the use of a Laurentide meltwater end member of -25parts per thousand indicates that near-surface salinity decreased by 2parts per thousand-4parts per thousand during these spikes. These results suggest that Gulf of Mexico SST warming preceded peak Laurentide Ice Sheet decay and the Bolling-Allerod interval by >2 k.y. and that heat was retained in the subtropical Atlantic during Heinrich event 1, consistent with modulation of deglaciall climate by thermohaline circulation.