Browsing by Author "Ngetar, Njoya Silas."

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Analysis of rhino poaching incidences and management strategies in South Africa.
(2016) Moneron, Sade Leigh.; Ngetar, Njoya Silas.
The illegal hunting and global trade in wildlife and wildlife products is a transnational, highly organised crime that threatens the survival of many endangered species. The rhinoceros is a well-known example of this trade as the demand for rhino horn for use in East Asia has resulted in the global decline of rhino populations, resulting in the Western Black rhino in Africa (Diceros bicornis longipes) officially being declared extinct in 2011. Although poaching has always existed, the number of African rhinos killed by poachers has escalated in the past eight years with at least 1 338 rhinos killed by poachers across Africa in 2015. This is the highest level since the rhino poaching crisis began in 2008, resulting in at least 5 940 African rhinos being killed. The majority of these incidences occurred within South Africa. South Africa plays a leading role in the conservation of the African rhino, currently conserving 83% of the African rhino population. However, it has been suggested that should poaching continue to increase as it has done over the past few years the rhino population in South Africa may begin to decline as early as 2016. South Africa’s upsurge in rhino poaching over the last few years has given rise to a kaleidoscope of debates on how to reduce poaching. An understanding of the different management strategies and their effectiveness would play a large role in identifying which method or combinations of methods work best to reduce poaching. The second chapter of this dissertation thus critically analyses the past, current and proposed strategies that are relevant to reducing incidences of rhino poaching using empirical literature from various scholars and stakeholders and attempts to provide insight into which strategy or combination of strategies is best suited to reduce poaching. As poaching involves a combination of aspects, it is clear that no one strategy or management tool will address all of these aspects on its own, and if implemented in isolation will not be successful. A combination of strategies that address all aspects of poaching needs to be working concurrently to decrease poaching levels. Law enforcement is one such management strategy crucial in the reduction of poaching and with increasing poaching incidents, law enforcement efforts in the form of deployment of anti-poaching unit, focused on high risk areas would provide for a more efficient and effective use of resources in reducing poaching incidences. The third chapter of this dissertation sought to investigate the spatial and temporal patterns of rhino poaching in the Hluhluwe-iMfolozi Park (HiP) between 1990 and 2013 and examine the relationships between observed patterns of poaching and biophysical and human variables using Geographic Information Systems (GIS). The results reveal poaching hot spots, and spatial and temporal variation in poaching incidences. Biophysical and human variables were also found to influence poaching densities differently depending on where they occurred spatially or temporally. The successful use of GIS in this analysis validates its potential as a geospatial tool for understanding the spatial and temporal distribution patterns of rhino poaching in the HiP. Understanding these patterns is crucial for future anti-poaching planning and mitigation of poaching activities with protected areas.
Causes of wetland erosion at Craigieburn, Mpumalanga Province, South Africa.
(2011) Ngetar, Njoya Silas.; Hughes, Jeffrey Colin.; Ellery, William Nolan.; Garland, Gerald George.
Wetland degradation, which includes deterioration in functional performance and erosion, is a problem around the world. This has engendered a quest for causes and attempts to prevent the problem or to rehabilitate wetlands already degraded or undergoing degradation. The Craigieburn wetland system in Mpumalanga Province, South Africa has undergone erosion due to two downstream discontinuous gullies that have drained and considerably reduced the size of the wetland system. Measurements from 1954 to 1997 aerial photographs showed that over 40 years, the upper gully migrated headward over a distance of 30 m, while the lower gully eroded 522 m headward raising the question as to what caused their erosion? Prior to this study, the predominant view was that human activities, namely poor land use management within the wetland system, increased human occupation, and overgrazing on the adjacent catchment that caused a reduction in vegetation cover, were responsible for this wetland erosion. Detailed field observation, aerial photograph interpretation, soil analyses for mineralogy, chemistry and particle size distribution, landscape mapping, dumpy level survey of the wetland valley and statistical analysis were undertaken to establish the relationships between gullying and possible contributing factors. Human impacts on wetland gully development between 1954 and 1997 were estimated using the number of individual homes, and total lengths of footpaths, animal tracks and dirt roads. Agricultural activities and the stocking rate of livestock were excluded due to the poor quality of aerial photographs and lack of historical records. Results of multiple regression correlating lengths of the two gullies (upper and lower gullies) and the sum of these human factors gave a high correlation (adjusted R² = 0.92 and 0.90, respectively) but a low significance (p = 0.18 and 0.21, respectively). However, time has played a significant role in the erosion of both the upper gully (R² = 0.82, p = 0.02) and the lower gully (R² = 0.98, p = 0.02) at Craigieburn. X-ray diffraction and X-ray fluorescence spectrometry of weathered parent materials showed that the area has undergone deep weathering, supplying sediments to the wetland valley through surface run-off. The accumulation of these sediments resulted in localized over-steepening of certain sections of the valley floor with raised gradients of 0.0336 and 0.0337 at the two headcuts relative to the upper and lower non-eroding sections with lower gradients. These localized steep sections increased flow velocity and stream power and therefore stream erosivity thus triggering gully erosion. In addition to localized areas of raised valley floor, results from multiple regression showed a significant relationship (p = 0.002) between areas of earthflow scars and gully length, especially at the lower gully, thus further suggesting that physical factors are largely responsible for gully erosion at Craigieburn. Long-term climate change has resulted in the formation of two terraces, an older, D1 (USU-760, 1.67 ± 0.89 ka) and a younger, D2 (USU 761, 0.32 ± 0.08 ka). The former probably eroded during the medieval warming around 1230 AD while the younger terrace, which likely formed during the last half of the Little Ice Age, has been eroding since the renewed warming thereafter. This erosion has been exacerbated by short-term periodic or seasonal climatic changes, especially episodic summer rainfall events, which have likely played a key role in the headward migration of the two gullies. The result has been shrinkage of the wetland system by about 15 m on both sides of the valley, leaving behind a greyish soil colour indicating wet and reducing conditions in the past. These, together with dried relict mottles left behind in the soil matrix at the margin of the shrunken wetland system suggest past seasonal fluctuation of the water table engendering the belief that the wetland system once extended beyond its present limit. The overwhelming contribution of these physical factors, in addition to the fact that the two gullies predate human occupation of the study area catchment and environs, strongly argues for their responsibility in gully initiation and development at Craigieburn. Human presence and activities, which only became evident in the catchment from the 1950s onwards, may be secondary contributory factors. This conclusion encourages a rethink of previous views that human occupation and activities are solely responsible for this wetland gully erosion at Craigieburn and provides a rationale for including physical processes and climate change as factors when investigating causes of wetland erosion elsewhere. Such an understanding should be used to inform any rehabilitation or conservation efforts that are related to wetland ecosystems.
A GIS based approach to identify road traffic fatal accident hotspots in the greater Durban city from 2011 - 2015.
(2017) Nyoni, Rudolphine.; Ngetar, Njoya Silas.
Road safety is a serious problem across the globe and its severity is more prominent in developing countries, especially in Africa. South Africa is no exception and road safety is one of the major challenges the greater Durban City in the KwaZulu-Natal Province will have to overcome in order to achieve its vision of being Africa’s most livable city by 2020. The prime goal of road safety is to reduce the number and severity of traffic accidents by identifying, implementing and evaluating measures to improve road safety. Road safety improvements are supposed to be applied to accident hotspots where they have the most significant impact, thus, identification of hotspots is an essential step in safety management. This study employed GIS spatial statistics tools to examine and map the trends and spatiotemporal distribution of fatal accident hotspots in the greater Durban city from 2011 - 2015. A total of 546 fatal accidents occurred that led to 594 fatalities. It was observed that the highest number of fatal accidents occurred in 2011, a year which marks the beginning of the UN Decade of Action for Road Safety. However, there was a declining trend from 2011-2013, with 2013 recording the lowest fatal accidents. Since 2013, fatal accidents saw an increasing trend until 2015. The majority (52.4%) of fatal accidents occurred on weekends, while 39.2% were recorded in March, May, June and December. Furthermore, the time period between 18:00-23:59 recorded the highest number of fatal accidents (33%). Ninety two and a half percent (92.5%) of fatal accidents resulted from human error, 67.9% of these resulted from a vehicle-pedestrian collision due to pedestrians entering the roadway when unsafe to do so. Dual carriageways accounted for 30.4% of the total fatal accidents, followed by freeways (26.7%) and single carriageways (25.8%). Spatial clustering of fatal accidents and spatial densities of fatal accident hotspots were evaluated using Global Moran's I and Anselin Local Moran’s I spatial autocorrelation, Kernel Density Estimation (KDE) and Getis-Ord Gi* statistics respectively. Moran’s I and Anselin Local Moran’s I show that the occurrence of fatal accidents were random, with the exception of 2012 which had a 1% less likelihood that clustering occurred. Ranking of hotspots using KDE was done with the help of pixel values of the observed locations while ranking of hotspots using Getis-Ord Gi* was done with the help of z-scores associated with statistical significance. Results of hotspot analysis delineated 22 hotspot locations at 90% - 99% confidence levels. Based on the Getis-Ord Gi* hotspot results, the N2 freeway is of critical concern as it appears consistently throughout the five-year period under study and accounting for 49.2% (29) of the total recorded fatalities. Fatal accident hotspots in the study area follow a Northeasterly-Southwesterly trend as determined by the directional distribution (standard deviation ellipse) function in ArcMap. The results can be effectively utilised by various agencies for adopting better planning and management strategies to reduce and prevent road traffic fatal accidents in the greater Durban City.
Post-dam sediment dynamics below the Inanda Dam at the Mgeni estuary, KwaZulu Natal (South Africa)
(2002) Ngetar, Njoya Silas.; Garland, Gerald George.
The Inanda Dam, situated some 32 to 35km upstream of the Mgeni River estuary on the Indian Ocean 5 km north of Durban, was constructed between 1984 and 1989. This impoundment deprived the downstream section of a great volume of water and sediment supply, initiating significant downstream changes. This situation is compounded by sand winning which directly extracts about 210,000 tonnes of sediment from the Lower Mgeni further depriving the estuary of sediment. A 1997 study predicted that assuming a continuous competent discharge and low contribution of sediments from the tributaries, the channel would gradually scour. Other predictions included a reduction in the total sediments reaching the estuary, continued flushing of existing channel sediments downstream towards the estuary, site-specific channel bed erosion at times of peak water release, gradual build up of sediments near the estuary mouth, gradual fining of bed-load channel and estuarine sediments, and ongoing re-establishment of the central island. The main aim of this study was thus to investigate downstream changes in the Mgeni river estuary below the Inanda dam with regards to sediments, water discharge and channel morphology from 1997 to test these assertions. Results show a decrease in competent discharge below the Inanda dam since 1997, resulting in a corresponding decrease in sand and an increase in mud fractions, with the mud content being associated predominantly with heavy minerals. This is reflected in the poorly sorted sediment. The plotting of cross-sectional survey revealed site-specific erosion, as well as estuarine bank failure to be an on-going process, and indicate points of bed scouring and accretion. A number of reasons have been identified as geomorphological explanations for the changes since 1997. These include among others, a lower hydraulic gradient at the estuary, occasional minor flood events, a weak bank material composition along some portions of the estuarine bank, the Tnanda dam , which impounds coarse sediments and large volume of water and increased tidal activity at the Mgeni estuary. It is concluded that although some of the probable responses predicted in 1997 have happened, sufficient relaxation time may not yet have elapsed for others to become evident.
The role of remote sensing in invasive alien plant species detection and the assessment of removal programs in two selected reserves in the eThekwini Municipality, KwaZulu-Natal Province.
(2016) Adam, Yusuf.; Ngetar, Njoya Silas.; Ramdhani, Syd.
One of the major current concerns by conservationists is alien invasive plants due to their rapid spread and threat to biodiversity. The detection of Invasive Alien Plant Species (IAPs) can aid in monitoring and managing their invasion on ecosystems. In South Africa approximately 10 million hectares of land have been invaded. To combat this invasion, the Working for Water program was initiated in 1995 aimed at manually removing them. Multispectral imagery can facilitate identification, assess removal initiatives and improve efficiency of IAP removal. The aim of this study is to determine the most appropriate sensor to detect three IAPs (Acacia podalyriifolia, Chromolaena odorata and Litsea glutinosa) and assess clearing programs of these species in two protected areas (Paradise Valley and Roosfontein Nature Reserves) within the eThekwini municipality, in KwaZulu-Natal province, South Africa using remote sensing. The three satellite sensors examined in this study included Landsat 7 ETM+, SPOT 5 and WorldView-2. The study also assessed four image classifiers (Parallelepiped, Maximum Likelihood, Spectral Angle Mapper and Iterative Self Organising Data Analysis Technique) in the detection of the selected IAPs. These sensors and techniques were compared based on their level of accuracy at detecting selected IAPs. The results of the study showed that WorldView-2 imagery and the Maximum Likelihood classifier had the highest overall accuracy (66.67%) , resulting in the successful classification of two (Acacia podalyriifolia and Chromolaena odorata) out of the three target species. This is due to the high spatial resolution of WorldView-2 imagery. This combination was then used to asses clearing of the selected IAPs by examining species distribution and density before and after clearing. Here the overall accuracies for the Paradise Valley and Roosfontein Nature Reserves were successful with accuracies above 85%. The density and distribution of all three IAPs decreased substantially in both sites except for the L. glutinosa species located in the Paradise Valley Nature Reserve which showed no significant decrease. These results show that geospatial data (especially remote sensing data) can be successfully used in both the detection of IAPs and the assessment of their removal.