4. Electronic Theses and Dissertations (ETDs) - Faculties submissions

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Behavioural and physiological responses of sable antelope to heat and aridity
(University of the Witwatersrand, Johannesburg, 2024-10) Haylock, Kiara Avelyen; Hetem, Robyn; Parrini, Francesca
The increased probability of longer, more extreme dry seasons, due to rapidly rising temperatures and the increased frequency and intensity of droughts, threatens water-dependent, selective grazers throughout Africa. Phenotypic plasticity such as behavioural adjustments and physiological flexibility may buffer the impacts of spatiotemporal variations in resource availability and climate. My project aimed to assess variations in home range size, movement distances, behavioural states of movement, fine-scale activity, microclimate selection and body temperature of sable antelope (Hippotragus niger niger), a water-dependent selective grazer, in relation to spatiotemporal variation in vegetation greenness and environmental heat load. To address the aim of my project, I measured body temperature and fine-scale activity using biologging in ten free-living GPS-collared sable antelopes in the semi-arid Bwabwata National Park of Namibia. Each collar was fitted with a miniature black globe thermometer to assess microclimate selection. A weather station with a standard black globe thermometer recorded black globe temperature and air temperature. Data collection spanned 24 months, from May 2016 to April 2018. The dry season was a critical period for sable antelopes, particularly the late dry season when high ambient temperatures compounded reduced resource availability. As conditions became hotter and browner with the progression of the dry season, home ranges elongated towards the Kavango River and increased in size by ~50% from the early dry to the late dry season. In response to increased 24-hour mean black globe temperature and increased exposure to brown vegetation, the 24-hour mean hourly displacement distance of sable antelopes increased with progression of the dry season, mostly due to the increased frequency of long, directed movements to the Kavango River during the late dry season. One sable antelope travelled between 13 and 30 kms every 4-5 days to access water from the river during the late dry season. Using Hidden Markov Models, four behavioural states were identified from the movement tracks of sable antelopes: resting, foraging, local movement and relocating. The long, directed movements to water, classified as a relocating behavioural state, predominated during the late dry season. Sable antelope displayed an increase in relocating behaviour and a decrease in foraging behaviour associated with high 24-hour mean black globe temperature and increased proportion of brown vegetation exposure. Sable antelopes also displayed an increase in local movement with increased exposure to brown vegetation and high 24-hour mean black globe temperature, but a decrease in resting behaviour with an increase in the proportion of brown vegetation exposure. Driven by decreasing vegetation greenness and increasing black globe temperatures, sable antelopes reduced their diurnal proportion of activity with progression of the dry season, associated with a reduction in activity during the heat of the day in response to increased exposure to brown vegetation, high 24-hour mean black globe temperature and an increased proportion of time spent in the shade. Sable antelopes did not fully compensate for lost diurnal activity, despite increased nocturnal activity during hot and dry conditions, as total 24-hour activity decreased with progression of the dry season. Sable antelopes also selected higher quality microclimates (i.e. microclimates that were on average 6.7 ± 0.2 oC cooler than direct sun) when increasingly exposed to brown vegetation and high 24-hour maximum black globe temperature. Fluctuations in 24-hour body temperature increased during the dry season with maximum amplitudes of body temperature rhythm of >5 oC within a single day during the late dry season. Sable antelopes displayed a reduction in minimum 24-hour body temperature in response to decreased 24-hour black globe temperature and increased exposure to brown vegetation during the early dry season, likely due to energy deprivation. While minimum body temperatures remained low during the late dry season, sable antelopes displayed an increase in maximum 24-hour body temperature in response to increased mean 24-hour black globe temperature and increased exposure to brown vegetation, likely due to water deprivation. High maximum 24-hour body temperatures, indicative of dehydration-induced hyperthermia, increased the likelihood of relocating movements to the Kavango River which in turn were associated with a subsequent decline in maximum 24-hour body temperatures. By linking body temperature to a behavioural state of movement, I am the first to demonstrate a direct link between access to a water resource and maximum body temperature in a free-living antelope species. The behavioural flexibility exhibited by sable antelopes during the dry season failed to buffer reduced resource availability as fluctuations in body temperature indicated that sable antelopes experienced nutritional and water stress. My findings highlight the importance of incorporating physiological measurements into behavioural and ecological studies to inform management decisions and improve conservation efforts in the face of climate change.
Modelling for Rainwater Harvesting Structures Using Geospatial Techniques
(University of the Witwatersrand, Johannesburg, 2024-10) Makaringe, Precious Nkhensani; Atif, Iqra
Climate change poses a significant threat, leading to droughts, floods, and hindering sustainable development. Water scarcity is a growing concern, particularly in developing countries like South Africa, where limited freshwater resources are further strained by climate variability. This research explores the potential of rainwater harvesting (RWH) as a strategy to address water scarcity in such regions. This study aims to model potential rainwater harvesting sites in Lynwood Park, Pretoria, South Africa, utilising geospatial techniques. Object-Based Image Classification (OBIC) was employed to extract building footprints from high-resolution satellite imagery. Microsoft and Google building footprints were utilised to determine the suitable automated building footprints for Lynnwood Park. ArcGIS Pro software served as the primary platform for spatial data analysis and mapping potential RWH sites. Data integration included high-resolution satellite imagery, a Digital Elevation Model (DEM), building footprints, and rainfall data. Additionally, questionnaires were distributed to estimate population and water demand within the study area. The research demonstrates the efficacy of geospatial tools in identifying suitable locations for RWH systems. Indicating that steeper slopes in the southern region of Lynnwood Park have limited collection from large rooftops, while the flatter north offered greater potential. Rainfall graphs and PRWH results suggest that over half of Lynwood Park's annual water demand could be met through rooftop rainwater collection. However, factors such as system losses due to evaporation, inefficiencies in collection and storage, and variability in rooftop sizes across different buildings would need to be incorporated into more detailed models, as well as water quality analysis for rooftop harvested water in future studies. This study highlights the potential of RWH as a viable water security strategy in water-scarce regions. The findings contribute to the development of geospatial approaches for RWH implementation, promoting water security and sustainability in a changing climate.
Morphological changes in the lungs and air sacs of the Japanese quail (Coturnix japonica) exposed to heat stress
(University of the Witwatersrand, Johannesburg, 2023-08) Abdulkadir, Abdurrahman; Reddy, Deran
The Japanese quail presents a potential protein food security alternative in rural sub-Saharan Africa because of its small size and easy husbandry. The nutritional and therapeutic value of its meat and egg makes it an interesting and better choice than chicken in some parts of the world. In addition, researchers used Japanese quail as an animal model of human genetic and developmental disorders because of its short generational interval. However, global warming threatens its welfare by propagating heat stress. The physiological response of Japanese quail under heat stress causes negative performance and sometimes instant mortality. Hence, in this study, lung of the quail under heat stress was microscopically examined as it is the most important organ for survival under heat stress. All other organs depend on the lungs for oxygen, and it is also the most crucial in evaporative cooling. A total of 38 Japanese quail were used in this study. A pilot study was conducted that used eight quails, to ensure the possibility of survival under the proposed experimental temperatures. Afterwards, 30 quails were randomly allocated — based on initial body mass— to five groups of six quails each. The control groups (CT and CT2) were maintained at a thermoneutral temperature of 25°C throughout the experiment while acute heat stress group (AH) were maintained at 38°C for 24 hours only. The chronic heat stress groups (CH1 and CH2) were maintained at 35°C for seven days and 28 days respectively. Body mass, cloacal temperature, and respiratory rate of quails were measured daily to monitor health and detect any serious ill health from heat exposure. Food and water were provided ad libitum. At the end of the experiment, all quails were terminated using an overdose of anaesthetic and lungs were harvested and processed for microscopy. Lung weight, volume and size were measured before sampling. Tissue samples were processed, and sections were cut with a microtome and stained with Mayers H&E, new pentachrome stain and Gomori’s one-step trichrome stain. Other tissue samples were triple immunolabelled with anti-α-SMA and Collagen 1 antibody and DAPI nuclear stain. Tissue samples were also processed for scanning and transmission electron microscopy. No significant difference in body mass, cloacal temperature, respiratory rate and lung parameters was found in heat-stressed quails compared with control. However, microscopic examination revealed blood congestion and excessive leakage of blood into airway of lungs in heat-stressed groups compared with the control. In addition, there was structural damage to parenchyma and blood vessels, which incites an inflammatory response causing deposition of collagen fibres in some areas of the lungs in heat-stressed groups. Interestingly, these effects occur in a time-dependent pattern. The most impact is seen in AH and CH1 groups while CH2 shows signs of recovery. In conclusion, Japanese quail lung was negatively impacted by heat stress, which can lead to instant mortality or long-term reduction of performance. Despite the evidence from this study suggesting that Japanese quail can adapt to the effects of heat stress if it survives the initial impact, a conscious effort must be made to alleviate or remove heat stress for quality outcomes.
The impact of climate change on the performance of banks in Southern Africa
(University of the Witwatersrand, Johannesburg, 2023) Ralebona, Phumudzo; Gwatidzo, Tendai
Using a sample of 12 countries from the SADC region, the study investigates the impact of climate change on the performance of commercial banks. The study this paper uses temperature and rainfall levels to measure climate change. Secondary data gathered through extraction of historical databases obtained from World Bank Development Indicators is used to deduce the relationship of these variables. The results suggest that climate change matters. The study finds that although there is a positive relationship between bank profitability and climate change, there is a threshold beyond which further increases in temperature and rainfall will adversely affect bank profitability. Also, banking sector concentration has a positive effect on banking profitability, while loan loss provisions and costs can erode profits if not managed properly. We also discover that there is no difference in how South Africa is affected by climate change compared to the rest of the SADC countries. A number of policy recommendations emanate from the study. First, it imperative for banks to begin to take into account climate change in the operational activities. Second, there is no country immune from the ravages of climate change. All countries in the SADC region must cooperate to address the serious challenges emanating from climate change. For example, the impact of climate for South African banks is not different to the banking sectors in other countries in the SADC region. Indeed, across most countries in the region natural disasters, such as droughts and floods, are becoming more frequent and also more devastating. Third, to address some of the challenges there is need to address the problems of, data scarcity and to use technology innovation to prevent natural disasters. These recommendations will equip the SADC region to be able to tackle the anticipated consequences of climate change on the financial institutions
Hydroponic farming for saffron cultivation in South Africa
(University of the Witwatersrand, Johannesburg, 2024) Smit, Johan
In South Africa, saffron has exclusively been cultivated using traditional farming methods. Although farmers face an increasing range of challenges and uncertainties, hydroponic farming offers an opportunity to alleviate many of these challenges, while simultaneously increasing output and reducing input expenses. The primary objective of the planned business venture was to investigate the possibility for hydroponic saffron farming in South Africa. The study focused on the development of a hydroponic system to cultivate saffron, aiming to mitigate the daily difficulties and risks faced by conventional farmers. The study adopted a qualitative exploratory research approach. The study gathered substantial information through interviews with farmers in both the traditional saffron and non-saffron hydroponic industries. Interviewing farmers provided insights into the perspectives of persons involved in both the traditional saffron industry and the non-saffron hydroponic growing sector. Three hydroponic cultivators and one saffron farmer were interviewed face-face. Another Saffron farmer was interviewed telephonically. The study examined the necessary requirements for hydroponic saffron cultivation in South Africa, covering technical factors for saffron cultivation, operational prerequisites, financials, market analysis, and challenges. The research findings highlighted the significance of hydroponic systems within an overall context. The main driving force for the transition from traditional farming to hydroponics was climate change among the participants. An essential challenge in hydroponic saffron growing is its relatively lower profitability compared to other crops like herbs, lettuce, and tomatoes. Including the concept of opportunity cost into the breakeven analysis will lead to a reduced repayment period, hence justifying the concept of saffron cultivation with a hydroponic system. In conclusion, cultivating saffron with hydroponics is a sustainable solution when considering opportunity costs due to the value of the spice, and the increasing uncertainty of climate change affecting output.
A documentation of the morphology of the lungs of the Sprague Dawley rat after chronic heat exposure
(University of the Witwatersrand, Johannesburg, 2023) Peya, Yolanda; Reddy, Deran
Climate change is a natural phenomenon that is exacerbated by mul4ple human ac4vi4es in the environment. These ac4vi4es lead to a rise in global temperatures. This increases the occurrence of heatwaves which pose a major threat to ecosystems, biodiversity, and the conserva4on of species on Earth. This study, aimed to document the effects of chronic heat exposure on the lungs of the Sprague Dawley rat using histological and immunofluorescence techniques. Twenty-four (24) rats were assigned to three groups; each exposed to different temperatures; (i) group A (n = 8) exposed to 25 °C (ii) group B (n = 8) exposed to 33 °C and (iii) group C (n = 8) exposed to 34 °C. This was done for a period of 4 weeks and the rats were euthanised therea`er. Methods employed included Intratracheal instillation, and histological and immunofluorescence techniques. This study found that rats in group A (25 °C) displayed no structural adapta4ons in comparison to groups B and C. Enlarged blood vessels with thick smooth muscle and prominent elas4c fibres, bronchus-associated lymphoid 4ssue (BALT), and increased collagen deposi4on were observed in group B (33 °C). These indicate the ac4va4on of immune responses and adapta4on to new environmental temperatures. In group C (34 °C), the lung morphology was severely damaged. There was an increased loss of epithelial integrity, oedema, pulmonary alveolar proteinosis (PAP), and a severe decrease in the lung- to-surface area ra4o. The significant changes caused by the 1 °C temperature difference between groups B (33 °C) and C (34 °C) illustrate the detrimental effects of chronic heat stress. It is evident that increasing environmental temperatures due to climate change is harmful to life and immediate interven4ons are necessary to combat rising temperatures
South African Podocarpaceae distribution interpreted from a physiological and population genetics perspective
(University of the Witwatersrand, Johannesburg, 2023-09) Twala, Thando Caroline; Fisher, Jolene T.; Glennon, Kelsey L.
Podocarpaceae (podocarp) are the most diverse conifer family with a Southern Hemisphere distribution. Podocarps occur in Afrotemperate and Afromontane forests at high elevations that are cool and humid. Podocarps once dominated the forest canopy but due to their slower growth rate and photosynthetic rates they have are in competition withangiosperms which have faster growing and higher photosynthetic rate. Due to the competition between podocarps and angiosperms, Bond (1989) proposed that podocarps were excluded to nutrient poor and unfavourable environments due to their limited competitive ability. However, podocarps persist under the forest canopy until conditions become favourable. This power dynamic shifts with climate oscillations where podocarps distributions expand and dominate when conditions become cooler. Owing to podocarps being the most diverse and widespread conifers they make for a good study system. This thesis focuses on understanding the climatic variables driving the current and future distribution of podocarps, how their seedling physiology may influence their ability to recruit and establish under climate change, and how this can influence their ability to disperse in their South African distribution. Ensemble species distribution modelling was used to characterise the current and future distribution of podocarps and identify the climatic variables that influence their distribution. The current and future environmental niche was quantified using environmental niche modelling. I found that variables predicting rainfall seasonality were the most important at determining the distribution of podocarps in South Africa. Afrocarpus falcatus and P. latifolius were predicted to have the largest geographic distribution, with P. henkelii and P. elongatus having restricted distributions. Both A. falcatus and P. latifolius were predicted to occur in the Limpopo, Mpumalanga, KwaZulu-Natal, Eastern Cape and Western Cape provinces of South Africa. Podocarpus henkelii was predicted to occur in the KwaZulu-Natal and Eastern Cape provinces. Podocarpus elongatus is endemic to the Western Cape Province. All four podocarps were predicted to expand to higher altitudes (up the escarpment) under climate change and contract in its coastal distribution. Although P. elongatus was predicted to occupy the smallest geographic distribution it was predicted to have the widest environmental niche than the other species, which was predicted to contract under climate change. The environmental niche of P. latifolius and P. henkelii was predicted to remain stable. Afrocarpus falcatus, P. latifolius, and P. henkelii showed niche conservatism, however, P. elongatus under RCP 4.5 → current and the RCP 8.5↔ current niche comparisons showed niche divergence. Podocarpus elongatus was predicted to expand to an environment it currently does not occupy. Ecophysiological and morphological experiments were conducted to understand how podocarp seedlings respond to drought and elevated temperatures. The experiments indicated that P. henkelii seedlings were more drought and heat tolerant than A. falcatus seedlings. Conditions are predicted to become hotter and drier in some parts of South Africa, and this study has shown that P. henkelii seedlings will be able to tolerate these conditions better than A. falcatus seedlings. Furthermore, this suggests that the distribution of P. henkelii is not constrained by its physiology but rather by other mechanisms such as competition, reproductive biology, and/or shade tolerance. Microsatellites were used to inform us about possible podocarp dispersal patterns in A. falcatus, P. latifolius and P. henkelii in South Africa. The results suggested that podocarp populations in South Africa were shown to have higher genetic diversity than other podocarps globally, however these results may be due to the limited number of microsatellites used in this study, smaller population sizes in comparison to other studies and methods used to measure population structure and diversity. As expected, the geographically widespread species (A. falcatus and P. latifolius) are more diverse than the geographically restricted P. henkelii. Geographically distant A. falcatus and P. henkelii populations showed higher differentiation than geographically proximal populations. In P. latifolius South African populations, there was strong isolation by distance. Although the distribution of podocarps is disjunct, there is dispersal between populations. Podocarps are resilient to climate change as was demonstrated by the work in this thesis, and by their paleodistribution expanding and contracting with climate oscillations. In this thesis I considered climate, ecophysiology and genetics as determinants of podocarps distribution. Under climate change, podocarps are predicted to expand to higher elevations to track favourable climatic conditions. Seasonal drought is the most important climatic determinant of podocarp distribution. The ability of these species to tolerate drought and heat stress suggests that the seedlings might be able to tolerate short periods of drought and heat stress, however prolonged exposure may lead to seedling mortality, but populations will then be maintained by adults. Populations show evidence of gene flow, indicating they will be able to persist through changing climates, as they have done in the past. This thesis has highlighted that the factors constraining podocarp distributions might be demographic, and future works should investigate the role of fire in podocarp seedling establishment and longevity, as well as their interactions with angiosperm competitors.
Characterizing microclimates as potential thermal buffers for reptiles, birds, and mammals in an arid-zone environment
(University of the Witwatersrand, Johannesburg, 2023) Warner, Grace M.; Alexander, Graham J.; Fuller, Andrea
Aridification, increases in air temperatures and frequency of extreme weather events, such as heat waves, are predicted to intensify under climate change, suggesting dire consequences for dryland animals. Microhabitats may buffer dryland animals against the changing climate, yet microclimatic data remains scarce from Africa and arid regions. The distribution, abundance, and thermal buffering capacity of five microhabitat types (burrows, nests, rock crevices, tree hollows and vegetation) were investigated across three habitat types (dunes, plains, and mountains) in the Kalahari. The distribution and abundance of microhabitats were assessed via strip transects, while thermal buffering capacity was evaluated by comparing miniature black globe temperatures from 70 representative sheltered microhabitats with 12 localised exposed-site microhabitats. The data generated have provided a baseline measure of the abundance and distribution of microhabitats in the Kalahari and have produced a year-long fine-resolution microclimatic thermal dataset. Microhabitat types and abundance were found to differ per habitat type and across topographic gradients. Abiotic drivers, such as soil type and fire frequency, along with drivers such as biotic community composition, were highlighted as potential causes of these microhabitat distribution patterns. Burrows were the best buffered microhabitat across all tested temporal and spatial gradients, providing an average maximum decrease of -29.5 ˚C during the day, and an average maximum increase of 20.1 ˚C during the night. Well-buffered microhabitats were rare within the field-site, whereas some of the poorest buffering microhabitats (Vegetation) were abundant and widespread. Thus, competition for well-buffered microhabitats may increase under climate change, whilst the risk of traversing large distances between microhabitats may become too great for smaller animals as exposure risk to extreme temperatures increases. Furthermore, birds and large mammals may likely be at a high risk of extreme temperature exposure, as their size and structural adaptations may restrict them from access to well-buffered microhabitats. Therefore, the need for the concurrent assessments of microhabitat distribution, abundance and buffering capacity in future species vulnerability assessments is highlighted, as it is the combination of these factors that are likely to impact population viability under climate change.
The Role of Natural Disasters in Shaping Individual Perceptions of Climate Change in Africa
(University of the Witwatersrand, Johannesburg, 2023-11-13) Van Niekerk, Courtney; Alence, Rod
This paper explores the relationship between individual perceptions of climate change and natural disasters in African states. This paper uses both qualitative and quantitative research methodology to explore 33 African states by observing the climate change perceptions as well as climate risk experienced by individuals through natural disasters. By using subnational Afrobarometer survey data and corresponding subnational natural disaster data, this paper finds individuals who have experienced natural disasters are less likely to express concerns for climate change.
Late Quaternary Palynological Studies at Lake St Lucia, KwaZulu-Natal
(University of the Witwatersrand, Johannesburg, 2023-08) Effiom, Angela Charles; Neumann, Frank; Bamford, Marion
Palynological studies were done on lacustrine sediments deposited during the last ~6300 and about ~2000 cal yrs BP in Mkhuze Swamp, which drains into the most northern part of Lake St Lucia located in the Indian Ocean Coastal Belt Biome of KwaZulu-Natal, eastern South Africa. The aim was to reconstruct the past vegetation and to infer past climate fluctuations as well as human disturbances to complement growing evidence from other disciplines about these questions in the area. Following standard palynological methods, samples from two cores Mkhuze River Delta (MKD-1, long core) and Mkhuze swamp (MK24-1, short core) were extracted and analyzed. Palynological results for both cores show a dominance of Poaceae (20-90%) suggesting a strong influence of grassy woodland savanna. Spirostachys pollen dominated the arboreal spectra of the pollen profile in MK24-1, but it dominated the arboreal pollen spectra for the last 2600 cal yrs BP in MKD-1 as Podocarpus pollen dominated the arboreal spectra from 6300-2600 cal yrs BP indicating a change from a forested environment to a more open woodland environment. The results also show that the mid Holocene was humid with high precipitation and high sea level while the late Holocene was warm, dry with Marine influence (more sea water flowing into the lake due to high evaporation and low fresh water supply caused by drought). Similar pollen fluctuations were observed in records from Lakes Eteza and Sibaya also located within the Indian Ocean Coastal Belt Biome. The presence of Pinus pollen at the top of the profiles suggests the onset of European settlement when pines were introduced for timber production. Other published pollen records from the region in the last ~7000 cal BP show a general trend from a mesic forested environment towards an open woodland environment with grasses which is due to climate change.

4. Electronic Theses and Dissertations (ETDs) - Faculties submissions

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