Browsing by Author "Ngcobo, Simphiwe Innocent."

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An assessment of the potential impacts of climate variability on sugarcane production across Southern Africa.
(2023) Ngcobo, Simphiwe Innocent.; Jewitt, Graham Paul Wyndham.; Hill, Trevor Raymond.; Archer, Emma.
The scale and extent of changes to demographic, economic and environmental systems exacerbated by human activities have been rapid and pervasive enough that it has been established that a new geologic era termed the Anthropocene has already begun. One of the most critical and challenging consequences of the Anthropocene has been the accelerated release of greenhouse gases leading to global warming and, consequently, climate change (CC), which has impacted hydrological responses and available water resources by increasing surface temperatures and altering precipitation patterns across spatio-temporal scales. These changes have exacerbated the vulnerability of various systems that sustain livelihoods, placing them at high risk of collapse. One of these systems is sugarcane production, which is a crucially important agricultural activity in many parts of the world, including southern Africa. There is a consensus that as a region, southern Africa will be subjected to amplified hydrological impacts which will affect the sugarcane production landscape. Further the expansion and intensification of sugarcane production across southern Africa is highly likely due, in part, to the recognition of the economic and social importance of this activity for supporting livelihoods. Sugarcane yields have been declining over the past 25 years in the region because of the increased frequency of climatic extremes. Literature reviews showed that by amplifying precipitation variability, climate change will increase the exposure and vulnerability of sugarcane to water stress and will have a devastating impact on yields. However, knowledge gaps remain regarding climate change impacts on water resources and sugarcane yields. Further, few studies have addressed the vulnerability and adaptation potential of sugarcane production at sufficient spatio-temporal scales. To address these knowledge gaps, an initial review was conducted to understand the dynamics between global change and water resources across southern Africa. The review showed that although global drivers are intricately related, their water resources impacts are highly complex, indirectly coupled and spatially and temporally sensitive. Having established a general perspective of the impacts of global change in southern Africa, the multi-scale drivers of sugarcane production were analysed using of a frequency analysis. This approach allowed the determination of proximate and ultimate drivers in the uMngeni, uMlaas, and Umvoti catchments in South Africa, the Ubombo catchment in eSwatini, the Shire catchment in Malawi and the Kilombero catchment in Tanzania. The frequency analysis provided quantitative descriptions of the water resource impacts of sugarcane production across southern Africa. Applying a relationship between observed sugarcane yields and future low, medium, and high production scenarios, this study developed water use estimates for sugarcane over multiple growing cycles. Results indicated that ultimate drivers play the most dominant role in the expansion of sugarcane production within each catchment. Drawing from this analysis, a methodology of assessing yield declines was developed based on a yield gap analysis using the AquaCrop crop growth model. The results were used to develop recommendations to mitigate yield declines by offering safeguards for the sugarcane industry against climatic extremes. Modelling results suggested that yield trends can be attributed to existing crop management approaches instead of prevailing hydroclimatic regimes. The importance of recognising the vulnerability and adaptation potential in sugarcane production was highlighted in this study. It was concluded that if sugarcane growers are to adapt to the effects of extreme climatic events, they must consider shifting crop management approaches and be proactively included in related research. This research highlighted the importance of addressing the interactions between activities that drive land use change, such as sugarcane production, and the current impacts of climatic extremes on water resources. This is important in rapidly developing regions and climate change hotspots such as southern Africa. The development of innovative adaptation policies that will safeguard the already-pressured water resources and secure the sustainability of sugarcane production will become increasingly important under an altered climate.
Projected impacts of climate change on water quality constituents and implications for adaptive management.
(2013) Ngcobo, Simphiwe Innocent.; Jewitt, Graham Paul Wyndham.; Stuart-Hill, Sabine Ingrid.; Lorentz, Simon Antony.; Lumsden, Trevor Graeme.
The past few decades have seen, amongst other topical environmental issues, increased concerns regarding the imminent threat of global warming and the consequential impacts of climate change on environmental, social and economic systems. Numerous groundbreaking studies conducted independently and cooperatively have provided abundant and conclusive evidence that global climates are changing and that these changes will almost certainly impact natural and socio-economic systems. Increased global change pressures, which include, inter alia, climate change, have increased concerns over the supply of adequate quality freshwater. There is an inadequate body of knowledge pertaining to linking basic hydrological processes which drive water quality (WQ) variability with projected climate change. Incorporating such research into policy development and governance with the intention of developing adaptive WQ management strategies is also overlooked. Thus, the aim of this study was the assessment of projected climate change impacts on selected WQ constituents in the context of agricultural non-point source pollution and the development of the necessary adaptation strategies that can be incorporated into WQ management, policy development and governance. This assessment was carried out in the form of a case study in the Mkabela Catchment near Wartburg in KwaZulu-Natal, South Africa. The research involved applying climate change projections derived from seven downscaled Global Circulation Models (GCMs) used in the Fourth Intergovernmental Panel on Climate Change (IPCC) Assessment Report, in the ACRU-NPS water quality model to assess the potential impacts on selected water quality constituents (viz. sediment, nitrogen and phosphorus). Results indicated positive correlations between WQ related impacts and contaminant migration as generated from agricultural fertilizer applications. ACRU-NPS simulations indicated increases in runoff and associated changes in WQ variable generation and migration from upstream sources in response to downscaled GCM projections. However, there was limited agreement found between the simulations derived from the various downscaled GCM projections in regard to the magnitude and direction (i.e. percent changes between present and the future) of these changes in WQ variables. The rainfall distribution analyses conducted on a daily time-step resolution for each selected GCM also showed limited consistency between the GCM projections regarding rainfall changes between the present and the future. The implication was that since hydrological and climate change modelling can inform adaptation under climate change. However, adaptation to climate change in water quality management and policy development is going to require approaches that fully recognise the uncertainties presented by climate change and the associated modelling thereof. It was also considered crucial that equal attention be given to both climate change and natural variability, in order to ensure that adaptation strategies remain robust and effective under conditions of climate change and its respective uncertainties.