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Remote sensing as a monitoring solution for water hyacinth (Pontederia crassipes) in the context of the biological control programme at Hartbeespoort Dam

- Kinsler, David Louis

  • Authors: Kinsler, David Louis
  • Date: 2023-10-13
  • Subjects: Remote sensing , Water hyacinth South Africa Hartbeespoort , Aquatic weeds Biological control South Africa Hartbeespoort , Megamelus scutellaris , Eutrophication
  • Language: English
  • Type: Academic theses , Master's theses , text
  • Identifier: http://hdl.handle.net/10962/424599 , vital:72167
  • Description: Water hyacinth (Pontederia crassipes (C.Mart.) Solms (Pontederiaceae)) is a significant aquatic weed both globally and in South Africa. Despite notable success with biological control of other invasive macrophytes, the plant remains as a problematic weed in many aquatic systems in South Africa, particularly due to the eutrophic status of many of its water systems, as well as the plant’s tolerance to cooler climatic conditions than most of its existing biological control agents. Hartbeespoort Dam, located about 30 kilometres west of Pretoria, South Africa, has been infamously infested with water hyacinth for decades, which impacts the important socioeconomic utility of the dam and functioning of natural ecological processes in the system. The dam has a long history of efforts to control water hyacinth, which include widespread herbicidal spray, mechanical removal and classical biological control programmes since the early 1990s - mostly with limited or short-lived success. However, after the introduction of a new, cold-tolerant biological control agent, Megamelus scutellaris Berg (Hemiptera: Delphacidae) in 2018 with an inundative release strategy, the water hyacinth dropped significantly from a maximum cover of about 45 percent (819 hectares) down to less than two percent (40 hectares) over a three-month period (November 2019 – January 2020). This was significant, as it marked the first successful biological control of water hyacinth in a eutrophic, temperate system in South Africa. However, due to the scale of Hartbeespoort Dam (1820 hectares) and the high spatiotemporal variation of the floating mats across time and space, quantifying and monitoring these rapid changes has proved difficult. In response to this problem, this thesis proposed a remote sensing solution to address the need for accurate, timely and readily accessible monitoring data of the water hyacinth population on the dam. Leveraging the temporally frequent (< 5 days revisit time) Sentinel-2 multispectral satellite data, as well as the powerful cloud-computing resources of Google Earth Engine, this thesis developed and deployed a relatively simple and robust index-based decision tree classification method to demonstrate the value of these technologies as an effective monitoring and analysis tool for monitoring large macrophyte infestations. To this end, several challenges had to be overcome in order to produce easily accessible data that was accurate and reliable. For example, due to the size of the Sentinel-2 Level-1C image dataset from August 2015 to March 2021 (n = 654), an automated process of filtering out clouded images was required. Additionally, the co-presence of algal and cyanobacterial blooms necessitated the development of a novel index, coined the Algae Resistant Macrophyte Index (ARMI), to deal with the challenges of accurate macrophyte detection. The high spatiotemporal variability of the floating mats meant that a typical, location-based confusion matrix as a means of assessing the accuracy of the decision tree classifier required a different approach which compared the total classified areas with higher resolution images. This thesis aims to demonstrate the utility of remote sensing tools to provide effective monitoring information to managers, researchers and other stakeholders. There is scope to expand to more areas in South Africa and beyond and may prove an invaluable tool to augment and support on-going and future macrophyte monitoring programmes. , Thesis (MSc) -- Faculty of Science, Geography, 2023
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  • Date Issued: 2023-10-13

Wild Honeybush (Cyclopia intermedia) augmentation

- Michau, Paul-Luc

  • Authors: Michau, Paul-Luc
  • Date: 2022-04-06
  • Subjects: Herbal teas South Africa Joubertina , Tea trade South Africa Joubertina , Legumes Harvesting South Africa Joubertina , Legumes Planting South Africa Joubertina , Sustainable development South Africa Joubertina , Economic development Environmental aspects South Africa Joubertina , Natural resources Management South Africa Joubertina , Wild Honeybush (Cyclopia intermedia)‎
  • Language: English
  • Type: Master's thesis , text
  • Identifier: http://hdl.handle.net/10962/232635 , vital:50009
  • Description: Honeybush (Cyclopia spp.) is an endemic legume to the fynbos region of South Africa, and certain species of the genus are used to make health tonics. There are growing international markets for such products and, currently, wild populations of the species Cyclopia intermedia are disproportionately relied upon to support this increase. Due to the sensitivity and ecological complexity of the resource, serious concerns about sustainability and regulation have arisen. The social landscape of the resource is equally as complex, and solutions for alleviating pressure on wild populations, such as reducing or banning harvesting, and switching to commercial cultivation are untenable in every case. A possible option, which has been used in the wildflower industry, is to augment (increase) wild populations by planting seeds or seedlings directly into the veld. The main focus of this research was to explore the viability of using augmentation to boost wild populations of C. intermedia through field trials. In support of this broad aim, research objectives addressed understanding the ecological habitat conditions of the species, quantifying the economic potential of augmentation, characterizing wild populations and conducting seed germination tests. GIS methods were used to locate sites most representative of natural conditions on different post-fire aged veld on a farm in the Kouga mountains. The study characterized habitat conditions by collecting soil and vegetation samples at plots where honeybush was present and absent within close proximity. Vegetation diversity was only slightly higher in presence plots, and no clear pattern between absence and presence plots was observed for soil properties. However, post-fire site age did significantly influence certain nutrient levels. The augmentation trial results indicate that seedlings have a much higher survival rate than seeds on average. Survival success varied unpredictably between plots where wild honeybush was already present and adjacent plots where it was absent. Post-fire site age influenced seedling growth and seed survival positively with the newly burnt plots showing the best growth rates overall. The cost-benefit analysis reveals that seeds are a better option as they require low-cost inputs and carry less risk, unlike seedlings which may have higher survival but are more expensive. The study recommends using trials to assess survival before choosing an option. Out of five natural populations of honeybush that were assessed only one showed seedling recruitment and three young plants were found between two of the other sites. Growth characteristics of populations showed expected variability based on site conditions and disturbance history. Growth appears to be rapid in the first-year post disturbance, thereafter slowing down. Average stem numbers and basal circumference increased concurrently for both harvested and unharvested populations. Due to the influence of natural conditions such as slope aspect and soil properties on plant morphology, it is best to compare harvested and unharvested individuals from the same site and preferably within close proximity to minimize such differences. Using seed sourced from the same parent population is critical to preserving genetic integrity and little is understood about germination characteristics from wild C. intermedia populations. The study tested germination rates between green and brown seed and alternative collection methods. When comparisons were done within farms on two occasions collection and seed colour did have a significant influence. Overall, the influence of which farm the seeds were collected from appeared to play the biggest role in determining germination. , Thesis (MSc) -- Faculty of Science, Geography, 2022
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  • Date Issued: 2022-04-06

Spatial analysis of the impact of human activities on the marine environment in Algoa Bay, South Africa

- Maphoto, Tidimalo Mary Anne

  • Authors: Maphoto, Tidimalo Mary Anne
  • Date: 2021-10-29
  • Subjects: Marine resources conservation Algoa Bay South Africa , Spatial analysis (Statistics) , Human ecology , Nature Effect of human beings on , Marine ecology Algoa Bay South Africa , Integrated coastal zone management Algoa Bay South Africa , Marine spatial planning Algoa Bay South Africa
  • Language: English
  • Type: Master's theses , text
  • Identifier: http://hdl.handle.net/10962/192086 , vital:45194
  • Description: Background: Humans have a long history of using the marine environment in multiple ways and continued use has led to a decline in the ecosystem services provided by marine systems in many places. In addition, human activities have steadily increased with time and advances in technology, further increasing impacts on marine systems. To understand and manage these impacts, we need to assess the spatial distribution and intensity of human activities in the marine environment, and quantify, where possible, their cumulative impacts on marine ecosystems. The spatial consideration of human activities and their associated impacts is important for conservation planning, Integrated Ocean Management and Marine Spatial Planning (MSP) initiatives. The main deliverable of this research study was to develop a cumulative impacts layer of human activities in Algoa Bay, South Africa, to support the Algoa Bay Marine Spatial Planning Project. Objective and Relevance: This research analyses the spatial impacts of human activities on the Algoa Bay marine environment (excluding the seashore). Algoa Bay is located on the south coast of South Africa in the Eastern Cape. The research explores stakeholders' perceptions of their knowledge of the human activities that take place in the bay. This research is informed by an expert-based geographical information systems (GIS) approach and cumulative impact assessment in order to map the spatial impacts of the activities as part of marine spatial planning. "Experts" were defined as stakeholders that contributed valuable knowledge of the human activities and their impacts; this definition of expert included "professional" and "non-professional" contributors to knowledge. The spatial aspect of the research is a significant contribution to the field as it will help inform decision-making in the Algoa Bay Marine Spatial Planning Project. Design and Methods: A mixed-method approach was used to generate data. A snowball sampling approach was used to identify research participants from key informants. Primary data were collected through questionnaire surveys, interviews and a focus group. Secondary data sources consisted of GIS data and reports from scientific organizations. Findings and Conclusion: The research findings indicate that the top three pressures that cause the greatest impact on the Algoa Bay marine environment are fishing, pollution and shipping. The cumulative impact of these activities was highest near harbours in Algoa Bay. The marine ecosystems that were most impacted by pressures were the Agulhas Island and the Agulhas Mixed Shore. The Warm Temperate marine ecosystems had fairly low cumulative impacts. The research findings indicate that there is a complex mix of human activities that impact the marine environment. This research supports the findings of other researchers that reveal that the highest cumulative impact is in areas closer to the coast and harbours owing to high population densities. Value of Study: This study builds onto the existing data by expanding the knowledge base and including more stakeholders to integrate as many human activities as possible and bring a holistic picture of the ocean's uses to inform MSP in Algoa Bay. , Thesis (MSc) -- Faculty of Science, Geography, 2021
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  • Date Issued: 2021-10-29

An assessment of the wild cyclopia subternata (vleitee) resource

- Van der Walt, Wouter

  • Authors: Van der Walt, Wouter
  • Date: 2021-04
  • Subjects: Legumes -- South Africa , Fynbos -- South Africa , Fynbos ecology -- South Africa , Fynbos -- Harvesting -- South Africa , Biodiversity conservation -- South Africa , Traditional ecological knowledge -- South Africa , Wild Cyclopia Subternata (Vleitee) , Honeybush tea industry
  • Language: English
  • Type: thesis , text , Masters , MSc
  • Identifier: http://hdl.handle.net/10962/176874 , vital:42767
  • Description: Cyclopia spp. is used for the production of Honeybush tea, an herbal tea which is used in many cases as a substitute for rooibos tea. The wild harvesting of this fynbos plant still brings in up to 85% of the annual crop and as such needs to be carefully monitored in order to avoid over harvesting and the destruction of biodiversity within the Eastern and Western Cape mountain regions of Southern Africa. Due to the concerns of overharvesting and unsuitable use of the wild resource issues of supply security have been raised. There is a lack of formal knowledge relating to the plant, its harvesting, the industry and its economic potential. This study aimed to amend this scarcity by contributing to the knowledge of C. subternata as a wild harvested plant, the physical environment favoured by C. subternata, sustainable use through harvesting of the wild plant and harvesting methods specific to this honeybush species. The research concludes by presenting a guideline for best harvest practices of the wild C. subternata plant. , Thesis (MSc) -- Faculty of Science, Department of Geography, 2021
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  • Date Issued: 2021-04

Coastal landscape change on the Cape St Francis/St Francis Bay peninsula from 1960 to 2014

- Schroeder, Daniel Heiko

  • Authors: Schroeder, Daniel Heiko
  • Date: 2015
  • Subjects: Coast changes -- South Africa -- Saint Francis, Cape , Peninsulas -- South Africa -- Saint Francis, Cape , Human ecology -- South Africa -- Saint Francis, Cape , Geographic information systems -- South Africa -- Saint Francis, Cape , Surveying -- South Africa -- Saint Francis, Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:5086 , http://hdl.handle.net/10962/d1018203
  • Description: A large proportion of the human population, their settlements and socioeconomic activities occur on land directly adjacent to the coastline. The increased demand for coastal leisure and tourism has interfered with natural landscape features and their associated processes. The Cape St Francis/St Francis Bay peninsula located on the southeast coast of South Africa was rapidly developed and transformed from a little fishing village into an urban coastal developed area over a 50-year period (1961-2014). A system that once existed in a state of dynamic or non-equilibrium was interfered with through anthropogenic disturbances, resulting in more frequent and intense natural events, which ranged from floods to debris flows, decreased sand supply and resulting beach erosion. The aim of the project was to identify and map landscape features and changes on the peninsula using an interdisciplinary approach. The triangulated methods of a desktop study using Geographic Information Systems (GIS) and media reviews, a crowdsourcing/participatory approach based on interviews, and a one year land surveying period of measurable field based surveys of physical features gave a well balanced view. The research showed that the natural landscape has been altered dramatically by settlement and associated infrastructure development. In particular, the loss of dunefields and the artificial modification of river paths were major impact areas. Beach erosion is a continual issue for the peninsula residents, particularly in St Francis Bay.
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  • Date Issued: 2015

Mapping and prediction of archaeological sites of habitation by modern humans using GIS and expert mapping on the south coast of South Africa

- Kleyn, Philippa May

A preliminary assessment linking altered catchment land-cover to the health of four temporarily open/closed South African estuaries

- Masefield, Vincent Antony

  • Authors: Masefield, Vincent Antony
  • Date: 2014
  • Subjects: Estuarine ecology -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4877 , http://hdl.handle.net/10962/d1013096
  • Description: Estuaries worldwide are being subjected to various degrees of catchment degradation, which is having severe consequences on the integrity of these aquatic ecosystems and their ability to function properly. This thesis investigated the relationship between catchment land-cover and estuarine health in four temporarily open/closed estuarine systems (TOCEs) in South Africa, namely the Groot Brak, East Kleinemonde, Mdloti and Tongati. GIS techniques were employed to delineate catchments, lower sections of catchments, 1 km and 100 m buffer zones, and to quantify the extent of land-cover classes present within these delineations. Anthropogenic activities outlined by the Department of Water Affairs and Forestry (DWAF) Resource Directed Measures (RDM) studies and their associated land-cover classes were described. The possible links between catchment and buffer zone land-cover class composition and health of the estuaries were explored. Results indicated that there was a relationship between catchment and estuarine health within the Coastal Protection Zone (CPZ) (1 km and 100 m) buffers, but not at a broader catchment level. Out of natural, urban built-up and cultivation land-cover classes, natural land was determined to be the best predictor of estuarine health within the CPZs. A method of rapidly assessing South African TOCE condition was applied and could be used to prioritise these estuaries for rehabilitation and/or conservation.
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  • Date Issued: 2014

Livelihoods and natural resource use along the rural-urban continuum

- Ward, Catherine Dale

  • Authors: Ward, Catherine Dale
  • Date: 2013
  • Subjects: Natural resources -- South Africa , Human ecology -- South Africa , Cities and towns -- Growth -- South Africa , Natural resources -- Management -- South Africa , Rural poor -- South Africa , Urban poor -- South Africa , Sustainable development -- South Africa
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4727 , http://hdl.handle.net/10962/d1001669 , Natural resources -- South Africa , Human ecology -- South Africa , Cities and towns -- Growth -- South Africa , Natural resources -- Management -- South Africa , Rural poor -- South Africa , Urban poor -- South Africa , Sustainable development -- South Africa
  • Description: Over the last century, developing countries have undergone rapid urbanisation resulting in marked social, economic and environmental changes. Africa is the least urbanised continent in the world but trends indicate that it is also the most rapidly urbanising region, accompanied by rising urban poverty. Urbanisation processes are often most pronounced in smaller urban centres since they experience the most severe pressures of population growth. Little is known about the role natural resources play along the rural-urban continuum and even less is known about the contribution of these resources within an urban context, particularly in small urban centres. In many sub-Saharan African cities, urban agriculture (the informal production of food in urban areas) has been used as a strategy to cope with increasing poverty levels but its role remains widely debated and uncertain. This thesis seeks to analyse the impacts of urbanisation on livelihoods and natural resource use, including home gardening and the collection of wild resources, in two South African towns and data was collected along the rural-urban continuum in Queenstown (Eastern Cape province) and Phalaborwa (Limpopo Province). Practices and contributions associated with agriculture and wild resource use were found to be significantly higher in Phalaborwa and this could be attributed to favourable environmental conditions and accessibility to wild resources due to the surrounding Mopani Bushveld. Rural households in Queenstown and Phalaborwa were more reliant on natural resources than their urban counterparts, but still diverse and incorporated a number of land-based and cash income generating strategies. Urban households tended to rely on one primary cash income strategy such as wage employment or state grants. However, natural resources did appear to play a subtle role in urban settings and particularly in the townships, where exclusion of natural resource contributions saw poverty levels increase up to 5%. Home gardening was practised by a wide range of people and not restricted to any one income group and, not surprisingly, wealthy cultivators who had access to resources such as land, water and fertilizer enjoyed increased benefits such as high produce yields. The results obtained suggest that rural-urban dynamics are complex and natural resource use in local livelihoods is contextualised within environmental settings, social preferences and historical contexts. Increasing pressures from the influx of people into small urban centres calls for a better understanding to how these processes are affecting livelihoods and natural resources to ensure sustainable management in the future.
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  • Date Issued: 2013

Morphology, patterns and processes in the Oyster Bay headland bypass dunefield, South Africa

- McConnachie, Lauren Bernyse

  • Authors: McConnachie, Lauren Bernyse
  • Date: 2013
  • Subjects: Sand dune conservation -- South Africa -- Eastern Cape Sand dune ecology -- South Africa -- Eastern Cape Coastal ecology -- South Africa -- Eastern Cape Sedimentation and deposition -- South Africa -- Eastern Cape Beach erosion -- South Africa -- Eastern Cape Coastal zone management -- South Africa -- Eastern Cape Shore protection -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4804 , http://hdl.handle.net/10962/d1001904
  • Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed , Maiden name: Elkington, Lauren
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  • Date Issued: 2013

Morphology, patterns and processes in the Oyster Bay headland bypass dunefield, South Africa

- Elkington, Lauren

  • Authors: Elkington, Lauren
  • Date: 2013
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:20984 , http://hdl.handle.net/10962/5879
  • Description: Studies of the dunefield systems crossing the Cape St. Francis headland in the Eastern Cape have focused on the role that wind plays in sediment transfer in coastal dunefield systems, with limited consideration of the role of water. The aim of this study was to improve understanding of the morphology, processes and patterns within the Oyster Bay HBD system, focussing particularly on surface water and groundwater interactions and the role of surface water in sediment transfer across the dunefield system. An extensive field survey was conducted, to collect related data, complimented by spatial and temporal analysis of the study area using GIS. The key findings from this research were the apparent differences between the western and eastern regions of the dunefield with regard to specific drivers and the respective processes and responses. Wind is the major driver of change up to and across the crest of the dunefield. In the eastern region water (ground water, surface water and the Sand River System) is the primary agent of sediment flux through processes of aggregation and slumping as well as episodic events including debris flows. This study has highlighted a need for further quantitative studies that investigate the movement of sediment through dunefield systems such as this (where water is at or near the land surface). The paradigm that sediment flux is entirely due to wind is almost certainly simplistic, and deeper understanding of these systems is needed.
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  • Date Issued: 2013

The zoogeography of the cetaceans in Algoa Bay

- Melly, Brigitte Leigh

  • Authors: Melly, Brigitte Leigh
  • Date: 2011
  • Subjects: Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4858 , http://hdl.handle.net/10962/d1005534 , Cetacea -- South Africa -- Algoa Bay , Cetacea -- Behavior -- South Africa -- Algoa Bay , Cetacea -- South Africa -- Algoa Bay -- Geographical distribution , Cetacea -- Counting -- South Africa -- Algoa Bay
  • Description: The most recent study on cetaceans in Algoa Bay, South Africa, was conducted over 14 years ago. Consequently, knowledge of the cetacean species visiting this bay is currently based on incidental observations and stranding data. A number of developments in recent years: a deepwater port, proposed oil refinery, increased boating and fishing (commercial and recreational), a proposed Marine Protected Area, and the release of a whale-watching permit, all of which may impact these animals in some way, highlight the need for a baseline study on cetaceans. Therefore, the aim of this study was to determine the spatial and temporal distribution, and habitat preference of cetaceans in Algoa Bay. Boat-based surveys were conducted monthly between March 2009 and July 2010. At each sighting the GPS location, species, group size and composition, and behaviour were recorded. Using GIS, the sighting data was related to data layers of geographical variables such as sea surface temperature, depth and sea-floor substrate. Approximately 365 hours of search effort were completed over 57 surveys, with a total of 346 sightings. Species observed were: southern right whales (Eubalaena australis), humpback whales (Megaptera novaeangliae), Bryde’s whales (Balaenoptera brydei), Indian Ocean bottlenose dolphins (Tursiops aduncus), Indo-Pacific humpback dolphins (Sousa chinensis), and longbeaked common dolphins (Delphinus capensis). Southern right whales were observed during austral winter, utilising the shallow, protected areas of the bay as a mating and nursery ground. Humpback whales were also recorded extensively during winter, in more offshore waters, with a significant number of mother-calf pairs sighted. Bryde’s whales were recorded in offshore waters during summer and autumn, where they were primarily observed travelling and foraging. Bottlenose dolphins were the most prolific species sighted. They were recorded year-round throughout the inshore waters of the bay, with large group sizes (up to 500 animals), and displayed a wide variety of behaviours. Humpback dolphins were observed in extremely shallow and inshore waters (mean bottom depth of 6.6 m) along the south-west corner of the bay, in small groups of approximately three individuals. Common dolphins were the least observed species, and were mainly observed foraging in large groups of up to 800 individuals. The results of this study indicate how cetaceans utilise the bay in significantly different ways. Geographical and anthropogenic factors have influenced the spatial and temporal distribution of these animals and have resulted in habitat preferences, as well as potential key habitats, in the bay. Thus, this study has provided baseline information for future research and for better informed conservation and management strategies in Algoa Bay.
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  • Date Issued: 2011

Assessment and monitoring of land degradation using remote sensing and geographic information systems (GIS): a case study of Qoqodala within the Wit-Kei catchment in the Eastern Cape, South Africa

- Ngcofe, Luncedo Dalithemba Sanelisiwe

  • Authors: Ngcofe, Luncedo Dalithemba Sanelisiwe
  • Date: 2009
  • Subjects: Geographic information systems -- South Africa -- Eastern Cape , Remote sensing -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape
  • Language: English
  • Type: Thesis , Masters , MSc
  • Identifier: vital:4818 , http://hdl.handle.net/10962/d1005492 , Geographic information systems -- South Africa -- Eastern Cape , Remote sensing -- South Africa -- Eastern Cape , Land degradation -- South Africa -- Eastern Cape
  • Description: Land degradation is a global problem affecting many countries including South Africa. This study was conducted in order to assess and monitor the nature and extent of land degradation within Qoqodala in the Eastern Cape Province, of South Africa. The study used GIS and Remote Sensing techniques together with household interviews in determining extent, spatial characteristics and nature of land degradation within the study area. Vegetation cover and bare-ground change were the land degradation indicators assessed and monitored by this study. Through RGB band combination, Tasselled Cap Analysis and Unsupervised ISODATA classification techniques, Landsat images over the past eighteen years (1984, 1993, 1996, 2000 and 2002) have been analysed. The results showed that there is vegetation cover and bare-ground increase in the study area. The vegetation increase has been seen as a sign of land degradation increase due to the encroachment of indigenous vegetation by Euryops species (also known as Lapesi by the local community). The bare-ground land degradation indicator has also increased. The analyses of slope showed the spatial characteristics of bare-ground occurring on moderate to flat slopes while vegetation cover occurs on steep to very steep slopes. Furthermore the photographs captured during field visits show rills and gullies or dongas occurring on bare-ground. The interviewed respondents indicated that decline in food production, increase in dongas and vast increase in Euryops and a decline in grassland are the indicators of degradation that are observed in the study area. The occurrence of erosion features (rills and dongas) on bare-ground and the increase of vegetation shown by GIS and Remote Sensing techniques showed a positive correlation with field and household survey towards establishing the nature of land degradation. In this study Landsat images together with interviews proved to be a very useful tool for land degradation research. However the suggestion of a higher spatial resolution satellite image on small catchment studies is recommended
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  • Date Issued: 2009
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