Abstracts on Global Climate Change

Jul 2005

A 25 m.y. isotopic record of paleodiet and environmental change from fossil mammals and paleosols from the NE margin of the Tibetan Plateau

Wang, Y Deng, T


We use the carbon and oxygen isotopic compositions of fossil tooth enamel and paleosols to reconstruct the late Cenozoic history of vegetation and environmental change in the Linxia Basin at the northeastern margin of the Tibetan Plateau. The delta(13)C values of fossil enamel from a diverse group of herbivores and of paleosol carbonate and organic matter indicate that C4 grasses were either absent or insignificant in the Linxia Basin prior to similar to 2-3 Ma and only became a significant component of local ecosystems in the Quaternary. This is in striking contrast to what was observed in Pakistan, Nepal, Africa and the Americas where C4 plants expanded rapidly in the late Miocene as indicated by a positive delta(13)C shift in mammalian tooth enamel and paleosols. The delta(18)O results from the same herbivore species show several significant shifts in climate in the late Cenozoic. Most notably, a positive delta(18)O shift after similar to 7 Ma indicates a shift to warmer and/or drier conditions and is comparable in timing and direction to the delta(18)O shift observed in paleosol carbonates in Pakistan and Nepal. This late Miocene climate change observed in the Indian sub-continent and in the Linxia Basin, however, seems to be a regional manifestation of a global climate change. The lack of evidence for C4 plants in the Linxia Basin prior to similar to 2-3 Ma suggests that the East Asian summer monsoon, which brings precipitation into northern China during the summer and creates optimal conditions for the growth of C4 grasses, was probably not strong enough to affect this part of China throughout much of the Neogene. This implies that the Himalayan-Tibetan Plateau may not have reached the present-day elevation across its vast extent to support a strong East Asian monsoon system before similar to 2-3 Ma. Our data also suggest that regional climatic conditions played an important role in controlling the expansion of C4 plants. (c) 2005 Elsevier B.V. All rights reserved.

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Arctic surface, cloud, and radiation properties based on the AVHRR Polar Pathfinder dataset. Part II: Recent trends

Wang, XJ Key, JR

JOURNAL OF CLIMATE 18:14 2575-2593

Over the past 20 yr, some Arctic surface and cloud properties have changed significantly. Results of an analysis of satellite data show that the Arctic has warmed and become cloudier in spring and summer but has cooled and become less cloudy in winter. The annual rate of surface temperature change is 0.057 degrees C for the Arctic region north of 60 degrees N. The surface broadband albedo has decreased significantly in autumn, especially over the Arctic Ocean, indicating a later freeze-up and snowfall. The surface albedo has decreased at an annual rate of -0.15% (absolute). Cloud fraction has decreased at an annual rate of -0.6% (absolute) in winter and increased at annual rates of 0.32% and 0.16% in spring and summer, respectively. On an annual time scale, there is no trend in cloud fraction. During spring and summer, changes in sea ice albedo that result from surface warming tend to modulate the radiative effect of increasing cloud cover. On an annual time scale, the all-wave cloud forcing at the surface has decreased at an annual rate of -0.335 W m(-2). indicating an increased cooling by clouds. There are large correlations between surface temperature anomalies and climate indices such as the Arctic Oscillation (AO) index for some areas, implying linkages between global climate change and Arctic climate change.

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Does inland aquatic biodiversity have a future in Asian developing countries?

Gopal, B


Inland aquatic ecosystems and their biodiversity in Asia represent a wide spectrum along a complex continuum of interacting ecological, economic, socio-cultural and political gradients all of which determine their present and future. Whereas the diversity of biophysical environments ensures a rich inland aquatic biodiversity, their present status has been greatly influenced by human societies that have depended on them for millennia. Besides high population densities and developmental pressures, socio-cultural factors, economic considerations and various policies concerning land and water resources are major factors responsible for the degradation of habitats and loss of biodiversity. The looming global climate change may only worsen the situation unless remedial measures are taken on a large scale and urgently. The future of aquatic biodiversity in Asian countries will depend upon a radical change in national policies on water, and upon research that can support the development of appropriate policies.

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Species-energy relationship in the deep sea: a test using the Quaternary fossil record

Hunt, G Cronin, TM Roy, K


Little is known about the processes regulating species richness in deep-sea communities. Here we take advantage of natural experiments involving climate change to test whether predictions of the species-energy hypothesis hold in the deep sea. In addition, we test for the relationship between temperature and species richness predicted by a recent model based on biochemical kinetics of metabolism. Using the deep-sea fossil record of benthic foraminifera and statistical meta-analyses of temperature-richness and productivity-richness relationships in 10 deep-sea cores, we show that temperature but not productivity is a significant predictor of species richness over the past c. 130 000 years. Our results not only show that the temperature-richness relationship in the deep-sea is remarkably similar to that found in terrestrial and shallow marine habitats, but also that species richness tracks temperature change over geological time, at least on scales of c. 100 000 years. Thus, predicting biotic response to global climate change in the deep sea would require better understanding of how temperature regulates the occurrences and geographical ranges of species.

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What affects the magnitude of change in first arrival dates of migrant birds?

Tryjanowski, P Kuzniak, S Sparks, TH


We analysed which among four factors (mean first arrival date, migration distance, changes in population size, detectability of species) influenced the magnitude of change (regression coefficient) in the first arrival dates of 30 migrant bird species in western Poland during 1983-2003. An examination suggested that several of these factors could be important: the regression coefficient was positively related to mean first arrival date (early species advancing their arrival date more) and negatively with change in population size (species in decline changing less). Moreover, significant differences in regression coefficient were detected between short and long distance migrants and between low detectable and highly detectable species. Undertaking a principal components analysis on the four factors produced an axis explaining 59% of the variance and whose positive values were associated with late arriving, long distance and low detectable species which were more likely to be in decline. However, the multi-collinearity of these factors is a problem that cannot be resolved here and we recommend that further work from different areas is needed to tease apart these effects.

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Gradient analysis, the next generation: towards more plant-relevant explanatory variables

Lookingbill, TR Urban, DL


The long history of gradient analysis is anchored in the observation that species turnover can be described along elevation gradients. This model is unsatisfying in that elevation is not directly relevant to plants and the ubiquitous “elevation gradient” is composed of multiple intertwined environmental factors. We offer an approach to landscape-scale vegetation analysis that disentangles the elevation gradient into its constituent parts through focused field sampling and statistical analysis. We illustrate the approach for an old-growth watershed in the Oregon Western Cascades. Our initial model of this system supports the common observation that forest community types are highly associated with specific elevation bands. By replacing elevation and other crude environmental proxy variables with estimates of more direct and resource gradients (radiation, temperature, and soil moisture), we create a vegetative model with stronger explanatory power than the proxy model in both cross-validation analysis and validation using an independent data set. The resulting model is also more biologically interpretable, which provides more meaningful insight into potential forest response to environmental change (e.g., global climate change scenarios). Acquiring a better mechanistic understanding of the relationship between plant communities and environmental predictor variables presents the next great challenge to community ecologists conducting gradient studies at landscape scales.

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Elevation, substrate, and the potential for climate-induced tree migration in the White Mountains, New Hampshire, USA

Lee, TD Barrett, JP Hartman, B


We assessed the potential for climate-induced migration of tree species along elevation gradients in the White Mountains of New Hampshire. To do so, we determined the extent to which tree species abundances were associated with elevation, site, and substrate-related variables over a range of elevations (530-880 m) that included the transition from northern hardwoods to spruce-fir forest in the White Mountain National Forest (USA). One-hundred and ten, 400 m(2) plots were established along three elevational transects; transects were separated from each other by at least 9 km. In each plot, site and substrate characteristics were measured and all stems >= 2.5 cm dbh were tallied. Species importance values were calculated and those of the five most abundant tree species -balsam fir, red spruce, sugar maple, American beech, and yellow birch - were regressed on elevation and site-substrate characteristics. Plots were ordinated using detrended correspondence analysis and their first and second axis scores were regressed on elevation and site-substrate characteristics. Both elevation and site-substrate characteristics - parent material type in particular - were important predictors of importance value. Balsam fir and red spruce abundance increased with elevation and, at all elevations, reached greatest abundance on shallow-to-rock parent materials. Fir showed greater abundance on north-facing than on south-facing slopes. Sugar maple and American beech declined with elevation and both, but especially sugar maple, were associated with fine and compact tills. Yellow birch, which did not show any association with substrate characteristics, increased to about 770 m, then declined. The frequency of different parent material types changed with elevation, with deep, fine and compact tills becoming less frequent - and shallow soils (rock within 50 cm of soil surface) becoming more frequent - with elevation. If the tree species-substrate associations described here are causal, then the elevational patterns of species abundance observed today are a consequence of both edaphic and climatic factors. As a consequence, vegetation response to climatic warming may be complex. While warming may result in upward migration of yellow birch and American beech, sugar maple, confronted with reduced availability of suitable substrate at high elevations, will likely show little upward response. Red spruce and balsam fir may persist on thin soils at lower elevations unless displaced by eastern hemlock. Thus, climatic warming will likely alter traditionally recognized tree assemblages in this region. (c) 2005 Elsevier B.V. All rights reserved.

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Genetic diversity and regional identity in the Australian remnant Nothofagus moorei

Taylor, KJ Lowe, AJ Hunter, RJ Ridgway, T Gresshoff, PM Rossetto, M


Nothofagus moorei (F. Muell.) Krasser has a disjunct and narrow distribution in south-eastern Australian cool temperate rainforest. To assess the conservation-genetic priorities for this species, the genetic diversity of 20 populations sampled from the largest remnant patches at northern and southern distributional extremes, the McPherson and Barrington ranges (a total of 146 individuals), was investigated by using inter simple sequence repeats (ISSR). Regeneration in northern regions of N. moorei has been documented to be predominantly by vegetative means, but our results indicate little evidence of clonality outside the multi-stemmed rings of trees. In addition, genetic diversity was considerably higher in the northern (McPherson, h = 0.1613) than in the southern range (Barrington, h = 0.1159), and genetic differentiation was significantly positively correlated with geographic distance in the former region, but not the latter. Total intraspecific variation was moderate, as measured by Shannon’s diversity index, I = 0.2719, and Nei’s gene diversity, h = 0.1672, and is considered at the high end of spectrum for estimates of narrow endemic species. An analysis of molecular variation indicated that the majority of genetic variation is partitioned among individuals within population (60%; P < 0.001), rather than among populations within regions (10%; P < 0.001). However, a large and significant component of the measured diversity was partitioned between northern and southern regions (29%; P < 0.001). Several hypotheses are outlined to explain these differences and management implications are discussed. However, given the narrow range, poor dispersal mechanism and restriction to cool temperate rainforest, the continued existence of N. moorei is most threatened by environmental instability and habitat loss resulting from global climate change. In this context the northern regions of the species are most at risk and extinction of such populations would lead to a significant loss of genetic variation for the species as a whole.

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Alluvial stratigraphic evidence for channel incision during the Mediaeval Warm Period on the central Great Plains, USA

Daniels, JM Knox, JC

HOLOCENE 15:5 736-747

Alluvial valley fills from tributaries to the upper Republican River, southwest Nebraska, USA, provide soil- and morpho-stratigraphic evidence for an episode of channel incision that occurred between c. I 100 and 800 C-14 yr BP, based on 11 new radiocarbon ages. This local episode of channel incision correlates with other alluvial stratigraphic studies from the central Great Plains and demonstrates regionally synchronous fluvial behaviour. Proxy records of palaeohydrologic conditions in and around the Great Plains (including lacustrine, aeolian and geomorphological sources) indicate that channel incision correlates with a multicentennial episode of common, widespread drought. Temporally, this drought episode corresponds to the period recognized in many regions as the Mediaeval Warm Period (MWP). Therefore, this research demonstrates: (1) a relationship in the semi-arid central Great Plains between drought and increased fluvial incision; and (2) a local/regional geomorphic response to a particular episode of global climate change.

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A multigenerational game model to analyze sustainable development

Haurie, A


This paper deals with a multigeneration game that provides a new rationale for representing time preference in very long term cost benefit analysis, as it happens typically in the economics of global climate change. One defines an intergenerational game where each generation has a random life duration and transfers the control of the economic system to the next generation at the end of its life. The payoff to a generation is a discounted sum of the expected consumption by the whole infinite sequence of generations, starting with the current one. The equilibrium is characterized by a dynamic programming equation; a unique solution is proved to exist; a numerical technique is proposed and implemented on a continuous time simplified version of the model DICE94. The results show the influence of this form of altruism on the asymptotic steady states of the economy subject to a global climate change effect.

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Equity and justice in climate change adaptation amongst natural-resource-dependent societies

Thomas, DSG Twyman, C


Issues of equity and justice are high on international agendas dealing with the impacts of global climate change. But what are the implications of climate change for equity and justice amongst vulnerable groups at local and sub-national levels? We ask this question for three reasons: (a) there is a considerable literature suggesting that the poorest and most vulnerable groups will disproportionately experience the negative effects of 21st century climate change; (b) such changes are likely to impact significantly on developing world countries, where natural-resource dependency is high; and (c) international conventions increasingly recognise the need to centrally engage resource stakeholders in agendas in order to achieve their desired aims, as part of more holistic approaches to sustainable development. These issues however have implications for distributive and procedural justice, particularly when considered within the efforts of the UNFCCC. The issues are examined through an evaluation of key criteria relating to climate change scenarios and vulnerability in the developing world, and second through two southern African case studies that explore the ways in which livelihoods are differentially impacted by (i) inequitable natural-resource use policies, (ii) community-based natural-resource management programmes. Finally, we consider the placement of climate change amongst the package of factors affecting equity in natural-resource use, and whether this placement creates a case for considering climate change as ‘special’ amongst livelihood disturbing factors in the developing world. (C) 2004 Elsevier Ltd. All rights reserved.

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Impacts of climate and land-cover changes in arid lands of Central Asia

Lioubimtseva, E Cole, R Adams, JM Kapustin, G


Despite the growing understanding of the global climate change, great uncertainties exist in the prediction of responses of and regions to global and regional, natural and human-induced climate change. Meteorological data series show a steady increase of annual and winter temperatures in Central Asia since the beginning of the 20th century that might have a strong potential impact on the region’s natural ecosystems, agricultural crops, and human health. Analyses of the NOAA AVHRR temporal series since the 1980s showed a decrease in aridity from 1991-2000 compared to 1982-1990. While most climate models agree that the temperature in and Central Asia will increase by 1-2 degrees C by 2030-2050, precipitation projections vary from one model to another and projected changes in the aridity index for different model runs show no consistent trend for this region. Local and regional human impacts in and zones can significantly modify surface albedo, as well as water exchange and nutrient cycles that could have impacts on the climatic system both at the regional and global scales. (c) 2005 Elsevier Ltd. All rights reserved.

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A regional, multi-sectoral and integrated assessment of the impacts of climate and socio-economic change in the UK

Holman, IP Rounsevell, MDA Shackley, S Harrison, PA Nicholls, RJ Berry, PM Audsley, E


Policy makers and stakeholders are increasingly demanding impact assessments which produce policy-relevant guidance on the local impacts of global climate change. The ‘Regional Climate Change Impact and Response Studies in East Anglia and North West England’ (RegIS) study developed a methodology for stakeholder-led, regional climate change impact assessment that explicitly evaluated local and regional (sub-national) scale impacts and adaptation options, and cross-sectoral interactions between four major sectors driving landscape change (agriculture, biodiversity, coasts and floodplains and water resources). The ‘Drivers-Pressure-State-Impact-Response’ (DPSIR) approach provided a structure for linking the modelling and scenario techniques. A 5 x 5 km grid was chosen for numerical modelling input (climate and socio-economic scenarios) and output, as a compromise between the climate scenario resolution (10 x 10 km) and the detailed spatial resolution output desired by stakeholders. Fundamental methodological issues have been raised by RegIS which reflect the difficulty of multi-sectoral modelling studies at local scales. In particular, the role of scenarios, error propagation in linked models, model validity, transparency and transportability as well as the use of integrated assessment to evaluate adaptation options to climate change are examined. Integrated assessments will provide new insights which will compliment those derived by more detailed sectoral assessments.

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The mystery of masting in trees

Koenig, WD Knops, JMH


This article describes the ecological and economic consequences of masting anddiscusses what causes seed production to vary so widely. A review of the latest research into proposed mechanisms that govern the synchronous production ofseed across geographic areas, and on the uncertain effects of global climate change on ecosystems in which masting plays a crucial role, is presented.

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