Browsing by Author "Midgley, Guy"

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    Are local range expansions in southerly populations of Aloidendron dichotomum early indicators of a future range shift?
    (2019) Grey, Kerry-Anne; Cunningham, Susan; Midgley, Guy; Foden, Wendy
    Aloidendron dichotomum is predicted to undergo a south and south-eastern range shift in response to anthropogenic climate warming. Despite this, its range is suggested to be limited by low temperature extremes at the cool range edge and no such range shift has yet been confirmed. However, eco-physiological knowledge necessary to predict and detect this range shift is lacking. This study aimed to determine whether physiological performance of A. dichotomum differs at a regional and local scale, and if so, whether regional and local temperatures explain physiological differences. Performance metrics and temperature data were collected during summer at 14 microsites in two sites at the cool range edge of A. dichotomum. Microsites were stratified by aspect and elevation. This study confirmed that A. dichotomum is performing CAM photosynthesis at its cool range edge. Further, the results provide evidence for the temperature dependence of A. dichotomum’s physiological performance. Higher performance was associated with warmer nights and the warmer north facing slopes. This is in keeping with our hypothesis that A. dichotomum individuals at the cool range edge would take advantage of higher temperatures more typical of their core range areas. Opposing this, higher carbon gain was found at Gannabos - the cooler of the two study sites. This may be due to the less variable rainfall pattern at Gannabos. Furthermore, performance was higher on the flats where temperatures were also cooler. This may be due to lower water runoff on the flats compared to the slopes. As a result, I suggest that the cool range edge of A. dichotomum is limited both by low temperatures and rainfall variability and that, with warming, constraints on these populations are being removed. This is substantiated by the observed high levels of juvenile recruitment in these populations relative to others, and in time, is likely to lead to range expansion in the region.
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    Climate change impacts and adaptation in South Africa
    (2014) Ziervogel, Gina; New, Mark; Archer van Garderen, Emma; Midgley, Guy; Taylor, Anna; Hamann, Ralph; Stuart-Hill, Sabine; Myers, Jonny; Warburton, Michele
    In this paper we review current approaches and recent advances in research on climate impacts and adaptation in South Africa. South Africa has a well-developed earth system science research program that underpins the climate change scenarios developed for the southern African region. Established research on the biophysical impacts of climate change on key sectors (water, agriculture, and biodiversity) integrates the climate change scenarios but further research is needed in a number of areas, such as the climate impacts on cities and the built environment. National government has developed a National Climate Change Response White Paper, but this has yet to translate into policy that mainstreams adaptation in everyday practice and longer-term planning in all spheres and levels of government. A national process to scope long-term adaptation scenarios is underway, focusing on cross-sectoral linkages in adaptation responses at a national level. Adaptation responses are emerging in certain sectors. Some notable city-scale and project-based adaptation responses have been implemented, but institutional challenges persist. In addition, a number of knowledge gaps remain in relation to the biophysical and socio-economic impacts of climate change. A particular need is to develop South Africa's capacity to undertake integrated assessments of climate change that can support climate-resilient development planning.
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    Climate variability in social-ecological systems of the Southern Cape: integrating farming and fishing perspectives
    (2018) Ward, Catherine Dale; Jarre, Astrid; Kemp, Georgina Cundill; Midgley, Guy
    Large scale shifts playing out on global climate levels are manifesting locally in the South Africa’s terrestrial and marine ecosystems, where it is difficult to predict how different habitats may respond to these changes in natural systems, particularly at local levels. For example, the highly complex nature of climate variability in the southern Cape and on the Agulhas Bank, coupled with the lack of long-term environmental monitoring data, has resulted in knowledge gaps on how climate impacts these local social-ecological systems. This thesis focuses on bringing together knowledge systems from farmers, handline fishers and local scientific weather sources to examine climate variability in terrestrial and marine social-ecological systems of the southern Cape, in order to bring local perspectives into conversation with scientific data outputs. Through examining different knowledge systems in parallel and overlaying different perspectives and observations, this thesis contributes towards a better understanding of complex systems change, linked through the common thread of climate variability under a resilience lens, at the local scale of the southern Cape and Agulhas Bank. This thesis also contextualises responses to change under the theme of climate variability from farmers’ and fishers’ perspectives, and shows how different theoretical discourses can work in a complementary fashion to address complexity. The terrestrial component of this thesis examined local agricultural perspectives by surveying southern Cape farmers, and built in terrestrial scientific data through looking at local climate in relation to farming perspectives. Observations on terrestrial rainfall and temperatures were collected through interviews with 50 farmers, along with shared rainfall records from 13 farming families and ten official weather stations in the area. Fisher perspectives in relation to climate variability were then integrated with marine scientific data to examine the marine component of the Agulhas Bank. Fisher observations of climate variability were examined by drawing on existing research conducted through the South Coast Interdisciplinary Research Project. Marine wind data were obtained through model outputs from NCEP-DOE Reanalysis and a recent scatterometer-based product. Overlaying these different bodies of knowledge reduced the uncertainties associated with any single set of observations and confirmed two environmental regime shifts in the region, in the mid-1990s and end-2000s. Local climate knowledge of farmers and fishers also overlapped and corroborated these environmental regime shifts. Changes in prevailing wind direction, rather than wind speed, were more prominent over time. While no clear trends of change over time were found in rainfall and temperature time series, decadal variability was present and after the mid-2000s, the onset of seasonal autumn rainfall was found to have shifted to a month later. Knowledge disconnects were broadly related to scale mismatches between fisher observations and marine data tendencies; complexities around freshwater availability; and shifting baselines of natural resources concerning present versus past variability observed by farmers and fishers. Responses to climate variability were complex and other stressors associated with economic and political challenges were usually seen as a greater threat to local livelihoods. However, climate stressors can push social-ecological systems into vulnerable states if not well integrated into adaptation strategies, which can have serious implications for future food and job security in the southern Cape. Local-based case studies such as this one increase understanding of local social-ecological systems under global change in an effort to contribute to future adaptation strategies in the southern Cape region.
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    The effects of environment and niche on the distributions of dwarf chameleons, present and future
    (2007) Houniet, Darren; Underhill, Les; Thuiller, Wilfried; Tolley, Krystal A; Midgley, Guy
    The niche and niche breadth of Dwarf Chameleons, Bradypodion, was assessed in terms of broad scale climatic factors. A niche-based modelling method was then used to construct present and future habitat suitability maps for 2050 and 2080, for species in the genus. Additionally, the relationship between environment and morphology was analysed for a representative Bradypodion species, the Cape Dwarf Chameleon, B. pumilum. The niche and niche breadth of species and phylogenetic clades were analysed and described via an ordination technique, the outlying mean index (OMI) analysis. Maxent (v2.3), a presence only niche modelling method, proved very useful in the construction of present and future habitat suitability maps for species within the genus. For analysis of the correspondence between environment and morphology for B. pumilum, regression trees were employed. Rainfall seasonality and maximum annual temperatures were shown to strongly effect the current distributions of the genus Bradypodion at both the species and clade level. Additionally, as closely related species inhabited similar environmental niches, the genus was shown to display a degree of niche conservatism. All species and clades were shown to respond to climate change scenarios for 2050 and 2080, but responses were individualistic. However, most demonstrated range contractions under predicted climate scenarios. Additionally, a strong correlation (p < 0.05) was found between the morphology of B. pumilum and its environment. Environmental factors explained over 40% of the variation in snout-vent length and tail length, and over 20% of the variation in head width and head height, thus supporting the hypothesis of a correspondence between vegetation and morphology in Bradypodion. These results have provided an understanding of the relationship between Bradypodion and their environments that could provide valuable information regarding their ecology. Additionally, the habitat suitability maps for 2050 and 2080 could prove useful in the construction of any future conservation plans for these species. Furthermore, the results support the hypothesis of a correspondence between environmental factors and morphological traits within the genus Bradypodion.
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    Modelling vegetation dynamics and their feedbacks over Southern Africa in response to climate change forcing
    (2004) Drew, Gillian; Hewitson, Bruce; Midgley, Guy
    The importance of vegetation feedbacks to the atmosphere has been highlighted in many recent research studies. The influence of climate on vegetation has long been established, and climate has regularly been used to predict vegetation distribution. However, the influence of vegetation on climate is a relatively new research area. The need to understand vegetation-atmosphere interactions is growing in light of the increasing atmospheric carbon dioxide concentrations and the change in climate associated with these increases. These linkages are analysed over southern Africa with the use of sophisticated computer models of the climate and vegetation. The models are used to explore some of the vegetation-atmosphere interactions for this region, but without attempting a definitive study of either system.
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    A socio-ecological approach for identifying and contextualising spatial ecosystem-based adaptation priorities at the sub-national level
    (Public Library of Science, 2016) Bourne, Amanda; Holness, Stephen; Holden, Petra; Scorgie, Sarshen; Donatti, Camila I; Midgley, Guy
    Climate change adds an additional layer of complexity to existing sustainable development and biodiversity conservation challenges. The impacts of global climate change are felt locally, and thus local governance structures will increasingly be responsible for preparedness and local responses. Ecosystem-based adaptation (EbA) options are gaining prominence as relevant climate change solutions. Local government officials seldom have an appropriate understanding of the role of ecosystem functioning in sustainable development goals, or access to relevant climate information. Thus the use of ecosystems in helping people adapt to climate change is limited partially by the lack of information on where ecosystems have the highest potential to do so. To begin overcoming this barrier, Conservation South Africa in partnership with local government developed a socio-ecological approach for identifying spatial EbA priorities at the sub-national level. Using GIS-based multi-criteria analysis and vegetation distribution models, the authors have spatially integrated relevant ecological and social information at a scale appropriate to inform local level political, administrative, and operational decision makers. This is the first systematic approach of which we are aware that highlights spatial priority areas for EbA implementation. Nodes of socio-ecological vulnerability are identified, and the inclusion of areas that provide ecosystem services and ecological resilience to future climate change is innovative. The purpose of this paper is to present and demonstrate a methodology for combining complex information into user-friendly spatial products for local level decision making on EbA. The authors focus on illustrating the kinds of products that can be generated from combining information in the suggested ways, and do not discuss the nuance of climate models nor present specific technical details of the model outputs here. Two representative case studies from rural South Africa demonstrate the replicability of this approach in rural and peri-urban areas of other developing and least developed countries around the world.
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    Wildfires in the Cape floristic region : exploring vegetation and weather as drivers of fire frequency
    (2009) Southey, Diane; Bond, William J; Underhill, Les; Midgley, Guy
    This study assessed the spatial and temporal patterns of wildfires in the Cape Floristic Region (CFR). It focused on the factors that influence fire frequency; namely vegetation age, ignition sources and weather conditions. This work was done to aid decisions on fire management in fynbos nature reserves. Fire intervals were extracted from historical fire records in four reserves in the CFR. The study sites were the Cederberg and Hottentots-Holland (western) reserves and the Swartberg and Outeniqua (eastern) reserves, and fire records were used from 1970 to 2007. A non-parametric technique and smoothing methods were used to highlight patterns in the extracted fire intervals. Comparisons of fire frequency were made between the study sites to analyse spatial patterns of burning. The impact of anthropogenic ignitions on fire frequency was analysed to explore the effect of people on fire patterns. The relationship between fuel age and fire size was analysed to determine the influence of vegetation age on fire patterns. Two novel methods were described in this thesis. The first method developed a technique to analyse temporal patterns in fire frequency while avoiding the impacts of temporal autocorrelation. The second method analysed the relationship between weather condition and fire events by utilising self-organising maps of synoptic states. A temporal change in the frequency of these synoptic states was tested for over the recording period. Synoptic states were used to produce two regional fire risk indicators for the CFR. I found that fire intervals in western study areas of CFR were shorter than fire intervals in eastern study areas. The effect of anthropogenic ignition sources shortened fire intervals in all study sites; however, this was relative to the natural fire frequency of each study site. Prescribed burning as a form of fire management contributed relatively little to the total area burned in all study sites. Fuel age has a significant correlation to fire size in only the drier (Swartberg) study site. A decreasing trend in fire return intervals was found in three study sites; Cederberg, Hottentots-Holland and Outeniqua. Synoptic states characteristic of the southern-most extent of a tropical easterly wave low were correlated to frequency fire events in the western study areas. Fires in the eastern study areas were correlated to a synoptic state characteristic of a tropical temperate trough. Easterly wave lows are associated with strong atmospheric convection whereas tropical temperate troughs are associated with pre-frontal conditions and strong, hot and dry winds. The frequencies of these synoptic states were shown to have increased in recent decade. The factors influencing fire frequency in the western CFR are predominantly sources of ignition, while the availability of fuels and suitable weather conditions restrict fires in the eastern CFR. Fire frequency has increased in the study sites where weather exerts the dominant control and this is due to the increase in synoptic states that promote wildfires. Historical records show that fire management has had little impact on the total area burned, thus fire management under climate change is unlikely to influence fire frequency.