By following a climate-friendly diet, consumers have the potential to reduce climate change. However, despite the growing awareness of the climate-friendly food options that are available, consumers still choose foods with a high carbon footprint. Following a survey design, this study aimed to determine the extent to which four psychological processes (denial, conflicting goals and aspirations, tokenism, and interpersonal influence) limit consumers’ climate-friendly food choices in South Africa. Data were collected from 151 participants using the Climate-friendly Food Choices Scale and the Psychological Barriers Scale. Regression analysis indicated that conflicting goals and aspirations and denial were the two main psychological barriers to climate-friendly food choices. Overall the barriers were negatively associated with climate-friendly food choices. Gender did not produce a significant effect in the study. Different age groups varied with regards to the extent to which they experienced the psychological barriers, but they did not differ significantly with regards to how often they made climate-friendly food choices. / Psychology / M.A. (Psychology)

Understanding and modeling microbial responses and feedbacks to climate change is hampered by a lack of a framework in the pelagic environment by which to link local mechanism to large scale patterns. Where terrestrial ecology draws from landscape theory and practice to address issues of scale, the pelagic seascape concept is still in its infancy. We have applied the patch mosaic paradigm of landscape ecology to the study of the seasonal and interannual variability of the North Pacific to facilitate comparative analysis between pelagic ecosystems and provide spatiotemporal context for eulerian time-series studies. Using multivariate, 13-year climatologies of sea surface temperature, photosynthetically active radiation, and chlorophyll a derived from remote sensing observations, we classified hierarchical seascapes at monthly and interannual scales. These dynamic, objectively-determined seascapes offer improved hydrographic coherence relative to oceanic regions with subjectively defined and static boundaries (Chapter 2) and represent unique biogeochemical functioning (Chapter 2) and microbial communities (Chapter3). Furthermore they provide consilience between satellite studies and in situ observations (Chapter 4) and allow for objective comparison of ecosystem forcing (Chapters, 4 and 5). In Chapter 2, we rigorously tested the assumption that satellite-derived seascapes describe regions of biogeochemical coherence. The seasonal cycle of the North Pacific was characterized at three levels of spatiotemporal hierarchy and broader relevance of monthly ���resolved seascapes was assessed through analysis of variance (ANOVA) and multiple linear regression (MLR) analyses of nutrient, primary productivity, and pCO��� data. Distinct nutrient and primary productivity regimes were well-characterized in the coarsest two levels of hierarchy (ANOVA, R�� = 0.5-0.7). Finer scale partitioning was more relevant for pCO���. MLR analyses revealed differential forcing on pCO��� across seascapes and hierarchical levels and a 33 % reduction in mean model error with increased partitioning (from 18.5 ��atm to 12.0 ��atm pCO���). In Chapter 3 we verified the seascapes with in situ collections of microbial abundance and structure. Flow cytometry data was collected from two long term time series and several cruises spanning thousand kilometers of the NE Pacific; these data allowed us to quantify spatiotemporal patterns. In addition, multiple response permutation analysis revealed differences in community structure across discrete seascapes, in terms of both absolute and relative abundances. Principal component analysis of the assemblage supported seascape divisions and revealed structure along environmental gradients with strong associations with chlorophyll a and sea surface temperature and, to a lesser extent, with mixed layer depth and mean photosynthetically active radiation in the mixed layer. Differences of assemblage structure between seascapes and strength of environmental forcing were strong in the subarctic and transition zones, but less pronounced in the subtropics, suggesting satellite-detected changes in bulk properties that may be associated with local physiology or interannual shifts in seascape boundaries. Based on the work presented in Chapter 4, we discovered that interannual shifts in the boundaries of a transition seascape and two distinct oligotrophic subtropical seascapes affect the variability observed at benchmark time series Station ALOHA; the latter two seascapes oscillate in their contributions to the expansion of the entire subtropics. On interannual scales, in situ phytoplankton abundance (as measured by chl-a), net primary productivity (NPP), and the relative abundance of eukaryotic phytoplankton and Synechococcus sp. increased during periods of encroachment by the transition seascape. Conversely, the relative abundance of Prochlorococcus increased and chl ���a and NPP decreased when the highly oligotrophic seascape encroached on Station ALOHA. The dynamic range (~6 million km��) of subtropical expansion is born almost entirely by the transition zone - resulting in a transfer of ~1.2 Pg of total primary C production between a system primed for export production and one dominated by the microbial loop. In Chapter 5, we investigated multiple factors that contribute to the effectiveness of the biological pump in the transition seascape. Near-continuous measurements of net primary production (NPP), net community production (NCP) and several ecophysiological variables were collected in across subarctic, transition, and subtropical seascapes of the Northeast Pacific during August and September of 2008. Mesoscale processes and shifts in community structure contributed to high export efficiency in the subtropical seascape; the convergence of assemblage structure, high biomass, moderate NPP: NCP and high NCP contributed to biologically mediated air-sea exchange in the transition seascape. Furthermore, NPP and NCP were strongly spatially coupled in both the transition (r[subscript 1, 39]=0.70; p<0.0001) and subtropical seascapes (r[subscript 1, 45]= 0.68, p<0.0001), suggesting the possibility for empirical modeling efforts. This dissertation provides a first step to characterize the seascape variability in the NE Pacific and to understand the modulation of primary and export production in a critical transition region. The multivariate seascape approach described here provides spatiotemporal context for in situ studies and allows objective comparisons of systems' responses to climatic forcing. An integrated ocean observing system will require insight from in situ observations and experiments, ecosystem models, and satellite remote sensing. The results highlighted in this dissertation suggest that the pelagic seascape framework, through its capacity to scale both context and mechanism, may serve as an important and unifying component of such an observing system. / Graduation date: 2013

Early life stages of many marine and diadromous fish species use sandy beach surf zones, which occur along >50% of the world's marine coastlines. This extensive habitat can provide juvenile fishes with an abundant supply of potential prey and the ability to hide from predators in its shallow turbid waters. Chinook salmon is an anadromous species that migrates to the ocean during their first (subyearlings) or second (yearlings) year of life. The majority of subyearlings reside in estuaries during their first summer season; however, a small number of juveniles also use surf zones. Early marine residence is considered a critical period for Chinook salmon due to high mortality rates; however the role of surf zones in Chinook salmon life history is unclear. Therefore, I determined the distribution of juvenile Chinook salmon on beaches of the eastern North Pacific, compared the migration and growth patterns observed in surf zones and estuaries, identified the factors that accounted for variation in juvenile surf zone catch, explored the factors that influence growth rate variation in surf zones and estuaries, and modeled how growth rates in these coastal habitats may vary in the near future with predicted changes in climate. The majority (94%) of juveniles were caught in surf zones adjacent to estuaries with trough areas, which are beach sections where sand moved by currents and waves produce a trench-like shape. Surf zone fish were collected in significantly lower numbers than estuarine juveniles but entered brackish/ocean waters at similar sizes. Juveniles in surf zones consumed similar organisms (gammarid amphipods, crustacean larvae and insects) as in estuaries. Furthermore, stomach fullness indices (average = 2% of body weight) and growth rates (average = 0.4 mm day�����) were similar in surf zones and estuaries. At one surf zone, juvenile catch was positively correlated to short-term specific growth rates (14 days prior to capture). A bioenergetics modeling approach indicated that given current conditions, consumption rates accounted for more of the variation in growth than prey energetic content and temperature. Climate models predict future increases in fresh water temperature (1.5 to 5.8��C), sea surface temperature (1.2��C) and wave height (0.75 m) that could influence estuarine and surf zone use. Therefore, I developed a local mixing model based on these predictions to estimate future surf zone and estuarine water temperatures in two of the watersheds studied. Based on these temperature projections and the bioenergetics model, I predicted how juvenile specific growth rates would vary in both habitats. I determined that increases in water temperature in both habitats would reduce specific growth rates by 9 to 40% in surf zones and estuaries if diet composition and consumption rates remain similar to present conditions. To compensate for the decline in growth, juveniles may increase their consumption rates or consume more energetically rich prey, if available. If they are not able to compensate, their size at the end of the season may be reduced, which could reduce their overall survival. These results confirm that a small number of suyearling Chinook salmon use sandy beach surf zones, mostly adjacent to estuary mouths, where they experience growth conditions comparable to estuaries. My findings indicate that, in certain situations, juvenile Chinook salmon surf zone use can be influenced by surf zone growth conditions, while variation in growth rates are themselves most strongly influenced by variation in consumption rates in surf zones and estuaries. Predicted changes in coastal western North American climate will likely modify juvenile growth conditions in the next 50 years, and potentially reduce overall survival. Additional insights into the potential impacts of climate change on juvenile salmon will require estimates of changes in the composition, energetic quality and abundance of prey communities inhabiting coastal environments. / Graduation date: 2013

As is the case in many other regions in the world, sugarcane production in southern Africa is affected by a wide range of climatic conditions, which can vary considerably from location to location and from year to year. As a result, the season length and growth cycles of sugarcane in southern Africa differ greatly. Such conditions include the hot and dry regions of northern KwaZulu-Natal, Swaziland and Mpumalanga, where sugarcane is mostly irrigated, to the humid sub-tropical coastal belt extending from the far north coast of KwaZulu-Natal to areas in the Eastern Cape, as well as the cool frost prone midlands regions of KwaZulu-Natal. Owing to the wide range of climatic conditions in which sugarcane is grown in southern Africa, there are many different external factors that affect sugarcane production, including a range of pests and diseases, frost occurrences and variations in soil water. The objective of this research was to (1) identify a number of important variables that affect cane production in southern Africa, (2) employ suitable models to reflect these variables, and (3) simulate and map the extent and severity of these variables at a high spatial resolution over southern Africa. Such variables include the Eldana saccharina and Chilo sacchariphagus stalk borers, sugarcane rust fungus, heat units with selected base temperatures, frost, soil water content, soil compaction, irrigation water demand, conducive and non-conducive growing conditions, flowering proficiencies for sugarcane, sugarcane yields and yield increments per unit of irrigation. The distribution patterns of the above-mentioned variables relied greatly upon the various models employed to represent them, as well as the accuracy of the temperature and rainfall databases to which the various models were applied. Although not definitive, the models used to reflect the variables which had been identified were considered to be generally satisfactory. The resolution at which the variables which had been identified in this study were mapped, was also found to be adequate. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Parthenium hysterophorus (Asteraceae), classified as an emerging weed in South Africa, has become abundant throughout large parts of southern and eastern Africa. In South Africa it has invaded areas in KwaZulu-Natal, Mpumalanga, the North West Province and Limpopo. A biological control programme against parthenium weed was launched in South Africa in 2003, based on the success achieved in Australia. Zygogramma bicolorata, a leaf-feeding beetle native to Mexico, was imported into South Africa via Central Queensland, Australia where it was released in the 1980s. This thesis examines aspects of the thermal physiology of Z. bicolorata which, in conjunction with its native and exotic geographical distribution, was used to predict the potential distribution of the agent in South Africa, in relation to climate. To determine Z. bicolorata’s physiological capability, several physiological parameters were examined for mechanistic modelling purposes. These parameters included the beetle’s lethal thermal limits, critical thermal limits, lethal humidities (Chapter 2) and developmental rate at constant temperatures (Chapter 3). In Chapter 4, these physiological parameters were entered into the dynamic modelling program CLIMEX (CLIMEX programme ver. 2, CSIRO Entomology ©) and a map of the areas that are acceptable for the establishment of Z. bicolorata was produced. The CLIMEX model predicted that most of South Africa is favourable for the establishment of the beetle, except in the west of the country and in the north of Lesotho, extending into South Africa. All areas in which parthenium currently occurs were predicted to be very favourable for Z. bicolorata establishment and proliferation. Optimal release sites aimed at initial establishment were earmarked at three areas in the northeastern part of South Africa (Jozini, Ndumu Game Reserve and along the road from Swaziland to Mozambique). It is concluded that Z. bicolorata is climatically suited to South Africa, increasing the likelihood that populations will establish and proliferate when released. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.

Thesis (MScFor)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The aim of this project was to determine the site effect- especially water availability - and the effect of cambial age on selected anatomical properties of Pinus radiata, in order to be able to predict possible changes in wood quality due to an expected change in climate. A second objective was to correlate ring and fibre properties, in order to determine, if ring properties could be used as a proxy to describe wood quality. The samples consisted of 12 trees, sampled at an age of 1 to 16 from six selected sites in the Western Cape, which ranged from water stressed to moist. Apart from the water availability all other external factors, such as elevation etc. were kept as equal as possible. Anatomical wood properties such as fibre length and fibre diameter, lumen diameter, cell wall thickness, ring width and earlywood/latewood ratio were determined and their change with cambial age and water availability was evaluated. Fibre length, fibre diameter and cell wall thickness increased with increasing cambial age, and ring width and earlywood/latewood ratio decreased with increasing cambial age. No significant correlations were found between any of the ring or fibre properties and water availability. Most of the fibre properties were significantly correlated with ring width and earlywood/latewood ratio when age was not considered as covariate, but showed no correlation when the age effect was excluded. / AFRIKAANSE OPSOMMING: Die doel van die projek was om die perseel se effek te bepaal, veral water beskikbaarheid, ten opsigte van die effek van kambium ouderdom en geselekteerde anatomiese eienskappe van Pinus radiata, om sodoende die moontike verandering in hout kwaliteit as gevolg van verwagte klimaatsverandering te voorspel. ‘n Tweede doelwit was om die ring en vesel eienskappe te korreleer en ook te bepaal of ring eienskappe gebruik kan word om hout kwaliteit te beskryf. Die monsters het bestaan uit bome van ses geselekteerde persele in die Wes Kaap en het gevarieer van ‘n water tekort na klam. Behalwe vir water beskikbaarheid is al die ander eksterne faktore, soos hoogte ens., konstant gehou waar moontlik. Anatomiese hout eienskappe soos vesel lengte en deursnee, sel deursnee, selwand dikte, ring wydte en E/L verhouding was bepaal asook die verandering met kambium ouderdom en water beskikbaarheid. Vesel lengte , vesel deursnee en selwand dikte het toegeneem met toename in kambium ouderdom, en ring wydte en E/L verhouding het afgeneem met toename in kambium ouderdom. Toename in water beskikbaarheid het gelei to afname in vesel lengte en selwand dikte, waar vesel deursnee, sel deursnee, E/L verhouding en ring wydte toegeneem het. Meeste van die vesel eienskappe het betekenisvol gekorrelleer met ring wydte en E/L verhouding wanneer ouderdom nie as ko-variant gebruik is nie.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Understanding the effects of climate change is one of the cardinal issues within the natural resource management circles. Increased droughts are part of these changes. Afrotemperate forests, as well as their drier Afromontane counterparts suffer from periodic and seasonal droughts respectively. To better understand the effect of droughts on these forests, three key species namely Olea capensis (Iron wood), Podocarpus latifolius (Common Yellow wood) and Pterocelastrus tricuspidatus (Candle wood), were analysed using dendroecologic techniques. Two sites in the Southern Cape were selected according to a West-to-East moisture gradient, with the drier site being close to George and the medium moist site at the Diepwalle estate in the vicinity of Knysna. Growth ring measurements from each of the species were used to calculate basal area and basal area increment during the lifetime of the trees. Drought years for the sites were then selected based on the Standardised Precipitation and Evapotranspiration Index (SPEI), also indicated by the growth during the drought periods. Differences in growth patterns for all three species were observed. An event analysis was then used to quantify the difference in the resistance (Rt), recovery (Rc), resilience (Rs) and relative resilience (RRs). With values standardised around one (Rt, Rc and Rs) and zero (RRs), it was seen that the Candle wood had the highest (~0.92) resistance and the Yellow wood had the highest (~1.3) recovery after the drought. Iron wood stood apart from the other two species in the sense that it only reacted negatively towards the drought one year after the event in most cases. It was concluded that each of the species were significantly different in their reactions towards drought. This specific difference in drought reaction can give way to the possibility that the species together adapted to relieve the stress of a short drought by splitting the available resources over a longer period. / AFRIKAANSE OPSOMMING: Dit is van uiterse belang vir bestuur doeleindes om die veranderende klimaat oor die wêreld te verstaan, insluitend die droogtes wat daarmee gepaard gaan. Die Afrotemperate woud-tipe, asook sy droeër teenstaander, die Afromontane, lei gereeld aan sporadiese en seisonale droogtes. Om hierdie woud-tipe se reaksie tot droogtes beter te verstaan, was drie boom spesies naamlik Ysterhout (Olea capensis), Kershout (Pterocelastrus tricuspidatus) en gewone Geelhout (Podocarpus latifolius), gekies vir die gebruik in ‘n dendro-ekologiese studie. Twee areas was gekies van ‘n wes-tot-oos droogte gradient, met die droeër blok in die George omgewing en die meer vogtige een naby aan Knysna. Die jaarring metings van elke boom was gebruik om beide die basale oppervlakte en die basale oppervlak groei per jaar aan te teken. ‘n Gestandardiseerde reenval en evapotranspirasie indeks (SPEI) was gebruik om vas te stel jare waarin matige tot sterk droogtes gebeur het. Hierdie gekose jare het aanduiding gegee dat daar wel ‘n verskil waargeneem was in die groei patrone van elke spesie gedurende die droogtes. ‘n Gebeurtenis analise is gebruik om ‘n kwantitatiewe verskil te kon sien in die weerstand (Rt), herstel (Rc), weerstandbiedendheid (Rs) en relatiewe weerstandbiedendheid (RRs). Die was waargeneem dat Kerhout die hoogste weerstand (0.92) toon, terwyl die Geelhout ‘n hoër herstel waarde (1.3) gehad het. Ysterhout het apart van die ander twee spesies gestaan in dìe dat dit eers een jaar na die droogte ‘n reaksie getoon het teenoor die droogte. Dit was dus gevind dat daar spesifieke verskil is tussen al drie van die spesies teen opsigte van stres reaksies was. Hierdie verskil kan dan wel ook moontlik aandui dat hierdie spesies en woud-tipe op so ‘n anier aangepas is dat dit die stress gedurende ‘n kort droogte versprei oor ‘n langer tydperk.

Human activities have contributed to the increase in atmospheric greenhouse gases such as carbon dioxide (CO2). This anthropogenic gas emission has led to a rise in the average Earth temperature. Moreover, the ocean constitutes the major sink for anthropogenic CO2 and its dissolution in surface waters has already resulted in an increase of seawater acidity since the beginning of the industrial revolution. This is commonly called ocean acidification. The increase in water temperature could induce modifications of the physical and chemical characteristics of the ocean. Also, the structure and the functioning of marine ecosystems may be altered as a result of ocean acidification. <p>Phytoplankton productivity is one of the primary controls in regulating our climate, for instance via impact on atmospheric CO2 levels. Coccolithophores, of which Emiliania huxleyi is the most abundant species, are considered to be the most important pelagic calcifying organisms on Earth. Coccolithophores are characterized by calcium carbonate platelets (coccoliths) covering the exterior of the cells. They form massive blooms in temperate and sub-polar oceans and in particular along continental margin and in shelf seas. The intrinsic coupling of organic matter production and calcification in coccolithophores underlines their biogeochemical importance in the marine carbon cycle. Both processes are susceptible to change with ocean acidification and warming. Coccolithophores are further known to produce transparent exopolymer particles (TEP) that promote particle aggregation and related processes such as marine snow formation and sinking. Thus, the impact of ocean warming and acidification on coccolithophores needs to be studied and this can be carried out through a transdisciplinary approach.<p>The first part of this thesis consisted of laboratory experiments on E. huxleyi under controlled conditions. The aim was to estimate the effect of increasing water temperature and acidity on E. huxleyi and especially on the calcification. Cultures were conducted at different partial pressures of CO2 (pCO2); the values considered were 180, 380 and 750 ppm corresponding to past, present and future (year 2100) atmospheric pCO2. These experiments were conducted at 13°C and 18°C. The cellular calcite concentration decreases with increasing pCO2. In addition, it decreases by 34 % at 380 ppm and by 7 % at 750 ppm with an increase in temperature of 5°C. Changes in calcite production at future pCO2 values are reflected in deteriorated coccolith morphology, while temperature does not affect coccolith morphology. Our findings suggest that the sole future increase of pCO2 may have a larger negative impact on calcification than its interacting effect with temperature or the increase in temperature alone. The evolution of culture experiments allows a better comprehension of the development of a bloom in natural environments. Indeed, in order to predict the future evolution of calcifying organisms, it is required to better understand the present-day biogeochemistry and ecology of pelagic calcifying communities under field conditions.<p>The second part of this dissertation was dedicated to results obtained during field investigations in the northern Bay of Biscay, where frequent and recurrent coccolithophorid blooms were observed. Cruises, assisted by remote sensing, were carried out along the continental margin in 2006 (29 May – 10 June), 2007 (7 May – 24 May) and 2008 (5 May – 23 May). Relevant biogeochemical parameters were measured in the water column (temperature, salinity, dissolved oxygen, Chlorophyll-a and nutrient concentrations) in order to determine the status of the bloom at the time of the different campaigns. Calcification has been shown to be extremely important in the study area. In addition, TEP production was significant at some stations, suggesting that the northern Bay of Biscay could constitute an area of important carbon export. Mortality factors for coccolithophores were studied and the first results of lysis rates measured in this region were presented. <p>Results obtained during culture experiments and comparison with data reported in the literature help to better understand and to predict the future of coccolithophores in a context of climate change. Data obtained during either culture experiments or field investigations allowed a better understanding of the TEP dynamics. Finally, the high lysis rates obtained demonstrate the importance of this process in bloom decline. Nevertheless, it is clear that we only begin to understand the effects of global change on marine biogeochemistry, carbon cycling and potential feedbacks on increasing atmospheric CO2. Thus, further research with a combination of laboratory experiments, field measurements and modelling are encouraged.<p><p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania huxleyi, are mainly found in the sub-polar and temperate oceans, where they produce huge blooms visible from space. Coccolithophores are sensitive to ocean acidification that results from the ongoing accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere. The response of these organisms to global change appears to be related to the reduction of their ability to produce calcium carbonate at the cellular level. At the community levels, one anticipates changes in the carbon fluxes associated to their blooms as calcification is reduced. However, the consequences of such environmental changes on this species are speculative and require improvements in the description of the mechanisms controlling the organic and inorganic carbon production and export.<p><p>The first aspect of this work was to study the response of these organisms to artificially modified CO2 concentrations representative of the conditions occurring in the past (glacial) and those expected by the end of the century (2100). Two different levels were examined: the continuous monospecific cultures (chemostats) allowed us to work at the cellular level while the mesocosms gave light to the mechanisms taking place in an isolated fraction of the natural community. The second aspect of this work consisted of field studies carried out during four cruises (2002, 2003, 2004 and 2006) in the northern Bay of Biscay, where the occurrence of E. huxleyi blooms were observed in late spring and early summer. We describe the vertical profiles of biogeochemical variables (nutrients, chlorophyll-a, dissolved inorganic chemistry, particulate carbon, transparent exopolymer particles (TEP)) and study processes such as primary production, calcification and bacterial production. The properties of these blooms are compared with those reported in the literature and enriched with original measurements such as the abundance and concentration of TEP that could play an important role in carbon export to the deep ocean, modifying the properties of the settling ballasted aggregates.<p> / Doctorat en Sciences / info:eu-repo/semantics/nonPublished

Recurring drought conditions have always been an endemic feature of climate in South Africa, limiting maize development and production. However, recent projections of the future climate by the Intergovernmental Panel on Climate Change suggest that due to an increase of atmospheric greenhouse gases, the frequency and severity of droughts will increase in drought-prone areas, mostly in subtropical climates. This has raised major concern for the agricultural sector, particularly the vulnerable small-scale farmers who merely rely on rain for crop production. Farmers in the Luvuvhu River catchment are not an exception, as this area is considered economically poor, whereby a significant number of people are dependent on rain-fed farming for subsistence. This study was therefore conducted in order to improve agricultural productivity in the area and thus help in the development of measures to secure livelihoods of those vulnerable small-scale farmers. Two drought indices viz. Standardized Precipitation Evapotranspiration Index (SPEI) and Water Requirement Satisfaction Index (WRSI) were used to quantify drought. A 120-day maturing maize crop was considered and three consecutive planting dates were staggered based on the average start of the rainy season. Frequencies and probabilities during each growing stage of maize were calculated based on the results of the two indices. Temporal variations of drought severity from 1975 to 2015 were evaluated and trends were analyzed using the non-parametric Spearman’s Rank Correlation test at α (0.05) significance level. For assessing climate change impact on droughts, SPEI and WRSI were computed using an output from downscaled projections of CSIRO Mark3.5 under the SRES A2 emission scenario for the period 1980/81 – 2099/100. The frequency of drought was calculated and the difference of SPEI and WRSI means between future climate periods and the base period were assessed using the independent t-test at α (0.10) significance level in STATISTICA software. The study revealed that planting a 120-day maturing maize crop in December would pose a high risk of frequent severe-extreme droughts during the flowering to the grain-filling stage at Levubu, Lwamondo, Thohoyandou, and Tshiombo; while planting in October could place crops at a lower risk of reduced yield and even total crop failure. In contrast, stations located in the low-lying plains of the catchment (Punda Maria, Sigonde, and Pafuri) were exposed to frequent moderate droughts following planting in October, with favorable conditions noted following the December planting date. Further analysis on the performance of the crop under various drought conditions revealed that WRSI values corresponding to more intense drought conditions were detected during the December planting date for all stations. Moreover, at Punda Maria, Sigonde and Pafuri, it was observed that extreme drought (WRSI <50) occurred once in five seasons, regardless of the planting date. Temporal analysis on historical droughts in the area indicated that there had been eight agricultural seasons subjected to extreme widespread droughts resulting in total crop failure i.e. 1983/84, 1988/89, 1991/92, 1993/94, 2001/02, 2002/03, 2004/05 and 2014/15. Results of Spearman’s rank correlation test revealed weak increasing drought trends at Thohoyandou (ρ = of 0.5 for WRSI) and at Levubu and Lwamondo (ρ = of 0.4 for SPEI), with no significant trends at the other stations. The study further revealed that climate change would enhance the severity of drought across the catchment. This was statistically significant (at 10% significance level) for the near-future and intermediate-future climates, relative to the base period. Drought remains a threat to rain-fed maize production in the Luvuvhu River catchment area of South Africa. In order to mitigate the possible effects of droughts under climate change, optimal planting dates were recommended for each region. The use of seasonal forecasts during drought seasons would also be useful for local rain-fed maize growers especially in regions where moisture is available for a short period during the growing season. It was further recommended that the Government ensure proper support such as effective early warning systems and inputs to the farmers. Moreover, essential communication between scientists, decision makers, and the farmers can help in planning and decision making ahead of and during the occurrence of droughts. / Agriculture, Animal Health and Human Ecology / M. Sc. (Agriculture)