<p> Severe drought plays a critical role in altering the magnitude and interannual variability of the net terrestrial carbon sink. Drought events immediately decrease net primary production (NPP), and drought length and magnitude tend to enhance this negative impact. However, satellite and in-situ measurements have also indicated that ecosystem recovery from extreme drought can extend several years beyond the return to normal climate conditions. If an ecosystem&rsquo;s drought recovery time exceeds the time interval between successive droughts, these legacy effects may reinforce the impact of future drought. Since the frequency and severity of extreme climate events are expected to increase with climate change, both the immediate and prolonged impact of drought may contribute to amplified climate warming by decreasing the strength of the land carbon sink. However, it is unknown whether terrestrial biosphere models capture the impact of drought legacy effects on carbon stocks and cycling. Using a suite of twelve land surface models from the Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP), we assessed model ability to simulate drought legacy effects by analyzing the modeled NPP response to drought events across forested regions of the US and Europe. We found that modeled drought legacy effects last about one year (2% reduction in NPP), with complete NPP recovery in the second post-drought year. Since observations suggest that legacy effects extend up to four years post-drought, with a 9% growth reduction in the first post-drought year, models appear to underestimate both the timescales and magnitude of drought legacy effects. We further explored vegetation sensitivity to climate anomalies through global, time-lagged correlation analysis of NPP and climatic water deficit. Regional differences in the lag time between climate anomaly and NPP response are prevalent, but low sensitivities (correlations) characterize the entire region. Significant correlations coincided with characteristic lag times of 0 to 6 months, indicating relatively immediate NPP response to moisture anomalies. Model ability to accurately simulate vegetation&rsquo;s response to drought and sensitivity to climate anomalies is necessary in order to produce reliable forecasts of land carbon sink strength and, consequently, to predict the rate at which climate change will progress in the future. Thus, the discrepancies between observed and simulated vegetation recovery from drought points to a potential critical model deficiency.</p><p>

<p> The structure and functioning of ecosystems across the globe are rapidly changing due to several components of global environmental change (GEC). My dissertation aims to illustrate how regional and local aspects of GEC impact diverse assemblages of species and species interactions. All organisms are embedded in complex networks of species interactions, and future efforts to predict and mitigate the impacts of GEC on ecological communities will be facilitated by such studies that incorporate a suite of species and species interactions. This study advances our understanding of how GEC will impact ecological communities by investigating two questions about GEC: 1) How will shifts in global climate cycles (e.g., El Nino Southern Oscillation), as a consequence of global warming, impact a diverse assemblage of butterflies that exist across a heterogeneous landscape? 2) What are the consequences of woody plant encroachment on complex, specialized interactions between plants, insect herbivores, and natural enemies (e.g., insect parasitoids)? Furthermore, I helped develop a tool to identify characteristics of ecological communities that are essential for promoting the diversity of trophic interactions. While the loss of species diversity is well recognized, interactions among species are vanishing at an astonishing rate, yet we know little about factors that determine the diversity of interactions within a community. Using data from a long-term butterfly monitoring dataset, I was able to demonstrate the utility of large-scale climate indices (e.g., ENSO) for modeling biotic/abiotic relationships for migratory butterfly species. Next, I used encroaching juniper woodlands in the Intermountain West to uncover that population age structure of dominant tress, such as juniper, can affect plant-insect dynamics and have implications for future control efforts in the expanding woodlands. Additionally, reductions of understory plant diversity, as a consequence of juniper expansion, resulted in significantly lower parasitism rates and parasitoid species diversity. Finally, simulated food webs revealed that species diversity and, to a lesser degree, consumer diet breadth, promote the diversity of trophic interactions. As ecosystems across the globe experience changes and the loss of species diversity continues, these findings offer insight into how GEC will impact species and species interactions.</p><p>

The purpose of the study was to contribute to the body of knowledge regarding the corporate sectors’ ability to operate within a carbon constrained society through the institutionalisation of effective corporate governance principles and practices. The research attempted to answer the question: To what extent and under what circumstances should corporate governance influence corporate response to climate change? Climate change risks impact on long-term sustainability of businesses and the competitiveness of some nations. The level of impact of climate change risk to a company is subject to a number of factors, including the nature of its business, the impact of local and international legislation, and the company’s ability to respond to climate change. South Africa is not isolated from climate change risks. Its mining sector is vulnerable to climate change because it is an energy intense sector, and coal is particularly vulnerable to carbon constrain legislation. The study was based on a qualitative research methodology where secondary data were sourced from company documents. The study showed that, on average, mining companies need to improve their climate change corporate governance mechanisms and practices. It was also shown that some of the companies have good systems in place. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

The record of climate change in Signedalen and Krossfjorden, northwest Spitsbergen, since the Late Weichselian glacial maximum, has been constructed using an integrated analysis of lacustrine, terrestrial and marine sediments. Thirty-four piston cores were taken from two series of linked lakes in Signedalen, fed by three small cirque glaciers. Six further cores were taken from the fjord inlet, Signehamna, into which meltwater from the linked glacier-fed lakes and a further two glaciers drain. Signehamna drains into Lilliehookfjorden, which with Mollerfjorden, combines to form Krossfjorden, from which 16 .cores were made available. Cores were analysed for moisture content, loss-on-ignition, bulk density, grain size, magnetic susceptibility, infra-red stimulated luminescence, by X-radiography and by radioisotopic dating methods, 210Pb and 14C. Bathymetric maps were constructed following echo sounding survey of the lakes. Seventy-two water samples from the linked lakes were used to assess contemporary environmental conditions, and to aid interpretation of sedimentary structures within core sediments. Results of lichenometric survey of moraine ridges and pro-talus deposits in and around Signedalen were analysed using discriminant analysis, and compared with Werner's (1988) lichen growth curve in order to establish a chronology of moraine stabilisation. Seismic records of Krossfjorden have revealed evidence of glacier advance at least as far as the sill separating Krossfjorden from the outer parts of the fjord and shelf associated with the Late Weichselian glacial maximum (Sexton et al., in press). Overlying the basal unit of a possible till , or sediments associated with rapid glacier retreat, is a blanket of homogeneous sediment formed by ice-distal deposition during the Holocene. There is no evidence of Younger Dryas glacier expansion preserved in the marine sediments, or in terrestrial moraines. Denudation rates calculated from lacustrine sediment accumulation infer the presence of smaller glaciers in Signedalen during the Younger Dryas than at present. The early to mid Holocene appears to have been characterised by relatively warm conditions, with much reduced glacier presence in Signedalen. Evidence of Neoglacial cooling, between approximately 3,000 yr BP and 1,500 yr BP, is found in lichenometric recorckof talus deposits, although precise dating of the inception, and duration of this cooling is problematic. No moraine sediments are recorded from this period. The Little Ice Age maximum, dated by licheno~etry to AD 1890, was the most extensive glacier advance to have affected the cirque glaciers of Signedalen and the tidewater glaciers of Krossfjorden, and is associated with the highest denudation rates recorded in the lacustrine sediments. It also appears to have been responsible for the formation of rock glaciers within the protalus deposits of Signedalen. Since this date, a general retreat of glaciers has been interrupted periodically by still-stands or slight readvances when climatic conditions deteriorated.

No description available.

Responsible for CO2 emissions of the order of 1 Gt, about 2-3 % of the global total, the shipping sector is part of the challenge to reduce emissions, in order to avoid dangerous climate change. Aiming to inform the sector’s response to the challenge, this research addresses two knowledge gaps. Current methods of estimating carbon emissions from shipping are subject to large uncertainties and lacking with respect to a set of greenhouse gas accounting criteria. Based on Automatic Identification System (AIS) data, a new methodology is developed to monitor fuel consumption and ensuing carbon emissions around the globe. Results from applying the method to a sample fleet of 13 vessels and validating it against fuel consumption records covering a time interval of one year demonstrate that, for the first time, estimating shipping emissions from individual ship AIS movement data has become possible at the global scale. Lacking information on the performance of carbon abatement technologies is the second knowledge gap. Due to its geographical and temporal variability, wind power technology is particularly dependent on a transparent assessment to exploit its carbon saving potential as a freely available and renewable energy source. Numerical performance models of two wind power technologies - a Flettner rotor and a towing kite - are combined with wind velocity data from a weather model to calculate their propulsive power contribution. Average results along five analysed sample routes range between 0.3 MW and 1.0 MW for a single Flettner rotor andbetween 0.1 MW and 0.9 MW for the modelled towing kite. Both methodologies are ready for further use. Applying the AIS-based method to data covering the world fleet may provide a concise, up-to-date view of greenhouse gas emissions from shipping when and where they take place. The wind power technology model can be applied to any shipping route around the world. Next steps towards fully exploring and optimising the potential of wind power technology are outlined. A better understanding of greenhouse gas emissions from shipping and of mitigation options gained from applying the models may, in turn, contribute to the sector’s successful response to the climate change challenge.

Increasing atmospheric CO2 concentrations associated with climate change will likely influence a wide variety of ecosystems. Terrestrial research has examined the effects of increasing CO2 concentrations on the functionality of plant systems; with studies ranging in scale from the short-term responses of individual leaves, to long-term ecological responses of complete forests. While terrestrial plants have received much attention, studies on the responses of marine plants (seagrasses) to increased CO2(aq) concentrations remain relatively sparse, with most research limited to small-scale, ex situ experimentation. Furthermore, few studies have attempted to address similarities between terrestrial and seagrass responses to increases in CO2(aq). The goals of this dissertation are to expand the scope of marine climate change research, and examine how the tropical seagrass, Thalassia testudinum responds to increasing CO2(aq) concentrations over multiple spatial and temporal scales. Manipulative laboratory and field experimentation reveal that, similar to terrestrial plants, seagrasses strongly respond to increases in CO2(aq) concentrations. Using a novel field technique, in situ field manipulations show that over short time scales, seagrasses respond to elevated CO2(aq) by increasing leaf photosynthetic rates and the production of soluble carbohydrates. Declines in leaf nutrient (nitrogen and phosphorus) content were additionally detected, paralleling responses from terrestrial systems. Over long time scales, seagrasses increase total above- and belowground biomass with elevated CO2(aq), suggesting that, similar to terrestrial research, pervasive increases in atmospheric and oceanic CO2(aq) concentrations stand to influence the productivity and functionality of these systems. Furthermore, field experiments reveal that seagrass epiphytes, which comprise an important component of seagrass ecosystems, additionally respond to increased CO2(aq) with strong declines in calcified taxa and increases in fleshy taxa. Together, this work demonstrates that increasing CO2(aq) concentrations will alter the functionality of seagrass ecosystems by increasing plant productivity and shifting the composition of the epiphyte community. These results have implications for future rates of carbon storage and sediment production within these widely distributed systems.

In this dissertation we analyze the effects of low carbon energy technology R&D portfolios on the cost of climate change mitigation. We use the results to create the analytical foundation for a decision support system aimed at effectively communicating the effects of uncertainty to decision makers. Specifically, we focus on three main areas. The first is generating a correlated probability distribution around detailed energy price forecasts. The second is showing how the availability of advanced energy technologies and combinations of them affect the marginal abatement cost curve. The third is creating the analytic foundation for a decision support system (DSS) by using an integrated assessment model to analyze the effects of combinations of low carbon energy technologies on CO2 concentration stabilization costs and then combining the results with probabilistic data from expert elicitations to analyze R&D portfolios. The third part also involves creating a multivariate regression model to represent the relationship between variables for additional analysis.

Climate change-induced increases in air temperature pose a substantial risk to birds inhabiting arid environments. Terrestrial endotherms, such as birds, can respond to high temperatures by moving to cooler microsites, increasing heat dissipation behaviour and/or suppressing activity. Previous studies have suggested that larger bird species may have a greater suppression of activity (e.g. foraging) than smaller species at high air temperatures. However, this body mass effect may be confounded by drinking behaviour, since different species have diverse drinking ecologies. Using four species of lark that inhabit the Tankwa Karoo National Park, I investigated whether foraging activity and other heat-influenced behaviours were influenced by body mass or drinking behaviour when comparisons were constrained within a single family. These lark species were: Red-capped Lark (24 g), Spikedheeled Lark (25 g), Karoo Lark (29 g) and Large-billed Lark (45 g). There was a two-fold difference in body mass between the lightest (Red-capped Lark) and the heaviest (Large-billed Lark). Moreover, two of these lark species drink surface water (drinking larks; Red-capped and Large-billed Lark) and two do not (non-drinking larks; Spike-heeled and Karoo Lark). I also collected data on other passerines present in the Tankwa Karoo for comparison to the larks. Black bulb thermometers were used to measure the thermal landscape and a combination of instantaneous scan samples and focal observations to record bird behaviour. Black bulb temperatures were as much as 8.16 °C cooler in shaded than in sunny locations. Similarly, black bulb temperatures were as much as 8.02 °C cooler off the ground than on the ground. The results from scan sample data showed limited support that foraging was negatively correlated (although non-significant) with mass between lark species as temperatures increased; however, data from focal observations suggested larks that obtain all water from food had a greater reduction in foraging as temperatures increase than larks that drink free surface water. Within scan samples, heat dissipation and shade-seeking behaviour appeared to be more strongly influenced by whether the species drinks free surface water or not than by differences in body mass. Furthermore, drinking larks dissipate heat at lower temperatures and seek shade at higher temperatures than non-drinking larks. Foraging intensity was higher in the sunny microsites as compared to shaded microsites for all species, suggesting that drinking larks might gain an energetic benefit due to increased heat tolerance. Therefore, non-drinking species may be vulnerable to foraging-thermoregulation trade-offs under climate change. However, ongoing drying trends in the Tankwa Karoo and reduced availability of surface water may make drinking species more vulnerable to climate change in the future than non-drinking species.

Men's and women's time-use in relation to wellbeing is well-investigated and understood within the context of the developed world. There has been limited research into the gendered experiences of time-use and three dimensional (3D) wellbeing in rural communities of sub-Saharan Africa and particularly so in semi-arid areas. As a result, failure to appreciate how time-use and wellbeing are experienced by the rural population in semi-arid areas impedes a full understanding of how rural inhabitants spend their time and how this makes them worse off or better off in different aspects of their wellbeing. This subsequently challenges the appropriateness of efforts to improve the lived experience of rural inhabitants. The study aimed to make a contribution to the knowledge gap on time-use and wellbeing by assessing how time-use relates to the experiences of material, subjective and relational aspects of wellbeing in a semi-arid area. It hypothesised that if men and women who are household-heads spend their time-use differently this has implications on their experiences of material, subjective and relational wellbeing. The study adopted a quantitative approach to primary data collection, analysis and interpretation of results. A questionnaire survey consisting of 93 randomly selected male and female headed households was conducted using stratified sampling techniques. Data was analysed using Microsoft Excel and SPSS software including regression analysis and statistical tests (Mann Witney U test) from which descriptive and statistical results were presented in tables and graphs following regression analysis. The study yielded several findings including the importance of personal care for improved subjective wellbeing despite the trade-off with material wellbeing; the importance of age and social grants for ensuring a better experience of material wellbeing; the importance of social connections particularly for widows and widowers; as well as the significance of time spent on leisure and work-outside for improving relational wellbeing. In addition, women's disproportionally high time spent on domestic work leaves them feeling subjectively worse-off while the persistence of traditional gender role division seems to have a determining effect on the time-use and wellbeing experiences of household-heads in the study area. Overall, the study highlights time-use related opportunities and constraints for improving the wellbeing of rural inhabitants in Onesi, Namibia.