Browsing by Subject "land use change"

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    Fifty years of land use change in the Swartland Western Cape South Africa: characteristics causes and consequences
    (Taylor & Francis, 2013) Halpern, A B W; Meadows, M E
    The Swartland is a largely agricultural region situated to the north of the greater Cape Town metropolitan area in the Western Cape, South Africa, and is known to have been subject to significant land use changes over many decades. This fertile land lies within the winter rainfall region of the Western Cape and has been used intensively for agriculture since European colonial occupation from the mid-seventeenth century onwards. Historically, the most prominent land use in the region was grain production, although there has been a substantial shift among many commercial farms in the region towards wine grapes. Quantitative assessments of the nature and extent of such changes, their underlying causal factors or, indeed, their environmental and economic impacts are lacking. This study presents an extension and re-evaluation of previous work in the region that considered land use change and its environmental implications (Meadows, Rahlao, & Dietrich, 2006) with the aim of providing a more detailed description of land use change in the Swartland during the period from 1960 to 2010 and to explore possible causes and implications of the observed changes. Five comparable sets of sequential aerial photographs for the Philadelphia area that may be considered representative of the broader Swartland landscape are analysed. GIS techniques are used to quantify the land use changes and the results show a marked recent shift from grain to grape, as well as a general increase in urbanization. The underlying structural causes of such trends are discussed and their possible environmental consequences are explored.
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    Potential impacts of climate change and land-use change on hydrological drought in the Western Cape (South Africa)
    (2022) Naik, Myra; Abiodun, Babatunde
    The Western Cape (South Africa) recently witnessed the most severe drought on record. The meteorological drought, which was characterised by below-normal rainfall for three consecutive years (2015 – 2017), cascaded to agricultural and then hydrological drought, resulting in devastating socio-economic consequences. While some studies indicate that climate change may increase the severity and frequency of droughts in the Western Cape in the future, there is a lack of information on how to mitigate the effects of future climate change on hydrological drought. This dissertation therefore investigated the extent to which land-use changes could be applied to reduce climate change impacts on future hydrological drought in this region. For the study, the revised Soil Water Assessment Tool (SWAT+) was calibrated and evaluated over four river basins in the Western Cape, and the climate simulation dataset from the COordinated Regional Downscaling EXperiment (CORDEX) was bias-corrected. Using the bias-corrected climate data as a forcing, the SWAT+ was used to project the impacts of future climate change on water yield and hydrological drought in the four basins and to quantify the sensitivity of the projection to four feasible land-use change scenarios in these basins. The relevant land-use scenarios are the expansion of mixed forests (FrLand), the restoration of grassland (GrLand), the restoration of shrubland (SrLand), and the expansion of cropland (CrLand). The model evaluation shows good agreement between the simulated and observed monthly streamflow at hydrological stations, and the bias correction of the CORDEX datasets improved the quality of the SWAT+ hydrological simulations in the four basins. The climate change projection depicts an increase in temperature and potential evapotranspiration but a decrease in precipitation and all the hydrological variables. Drying is projected across the Western Cape, and the magnitude of such drying increases with higher global warming levels (GWLs). The land-use changes alter the impacts of climate change by influencing the hydrological balance. While FrLand mitigates the impacts of climate change on the frequency of hydrological drought by increasing streamflow, soil water and percolation, CrLand mitigates the impacts by increasing surface runoff. However, the magnitudes of these land-use change impacts are very small compared to the climate change impacts. Hence, the results suggest that land-use changes may not be an efficient strategy for mitigating the climate change impacts on hydrological drought over the region. The findings obtained from this 2 research provide relevant information towards mitigating the severity of future droughts and improving water security in Western Cape River Basins.
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    The diatom record: Reconstructing historically recent environmental change in the Knysna estuary
    (2022) Antonopoulos, Helen Grace; Meadows, Michael Edward; Kirsten, Kelly L
    Estuaries are highly productive systems responsible for many vital ecosystem goods and services. Therefore, it is not surprising that the diversity and abundance of exploitable estuarine resources have attracted human settlers for centuries. Increased anthropogenic pressures have placed much stress on estuarine and coastal ecosystems. This is the case of the Knysna Estuary, which is South Africa's highestrated estuary in terms of biodiversity and conservation importance. This study represents the first highresolution diatom record from the Knysna Estuary encompassing the last ∼680 years. Diatom analysis was employed to reconstruct salinity, nutrients, and saprobity variables in addition to inferring community structure and trophic status over time by creating an age-depth model based on a combination of ²¹⁰Pb and radiocarbon dates. The record is divided into three distinctive phases, namely the Pre-Colonial (∼610 to ∼200 cal BP), Colonial (∼200 cal BP to ∼1900 CE), and Anthropogenically Impacted Lagoon Phase (∼1900 CE to Present). These phases correspond with the Little Ice Age (LIA), the arrival of colonialists, and anthropogenic impacts linked to rapid population growth and land use change. More specifically, the dominance of marine species illustrate that the first phase of the LIA is associated with drier conditions, whereas a growing dilute and eutrophic assemblage reveals a wetter second phase of the LIA coinciding with the arrival of colonialists in the 1700s. Consequently, it is challenging to disentangle natural climate change with the effects of deforestation and agriculture during the Colonial Phase. A shift towards an increasingly fresh, hypertrophic, and polysaprobic diatom assemblage is indicative of the intensification of agricultural practices in the catchment from ∼1900 CE to present, stormwater inflow, the inefficiency of the Knysna Waste Water Treatment Works (WWTW), and sewage entering the estuary via streams during the final phase of the estuary's development. This high-resolution record is of vital importance, as it is one of a few palaeoestuarine studies in the Southern Hemisphere to illuminate the effects of natural climate change and human-induced impacts on an estuarine system. Despite the limitations, this study illustrates that diatoms are a useful tool for tracking environmental change in estuaries.