Browsing by Author "Dickens, Christopher William Spencer."

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Monitoring the health of the rivers of the Durban Metropolitan Area using fresh water invertebrates. A pilot study.
(2002) Nunkumar, Shamilla.; Dickens, Christopher William Spencer.; Olorunsogo, F.
This document is aimed at all parties involved with conservation, planning and management of rivers within the Greater Durban Metropolitan Area, South Africa. The intentions of this study were to provide information on the health of the rivers using freshwater invertebrates and to identify areas where investigative efforts should be focused. In doing so, this document incorporates two data processing methods or techniques used in biomonitoring, the South African Scoring System (SASS) Rapid Bioassessment Technique (RBA) version 4 and the Integrated Habitat Assessment System (IHAS version 2c). The history, current status and future prospects and potential benefits of biological indicators both globally and in South Africa are reviewed and discussed. The RBA (SASS4) involved the standardised collection of samples using the "kick and sweep" technique from defined habitat types at representative sites on river stretches using a standardised net following defined methods. The total score per site is calculated for each family represented in the sample, which is then summed to give the SASS4 score. Lower scores are given to families with a high level of tolerance for polluted waters. The Average Score Per Taxon (ASPT) computation is obtained by dividing the SASS4 total by the number of taxa (families) in the sample. Both scores were considered when determining water quality impairment. The number and abundance of the different taxa and the number of biotopes present were considered as other measures of the river condition. The presence of numerous families of highly tolerant organisms (sludge worms and leeches) usually indicated poor water quality as represented in the Umlaas River, iSiphingo River, Tongati River, and the Ohlanga River. Several different types (or taxa) of stoneflies, mayflies and caddisflies (higher biodiversity) indicated a healthy site for example the iLovu River. Moderate river sites were characterized by declination in invertebrate diversity. Invertebrate diversity declines as the degradation of water quality increases. The manner in which SASS4 scores varied with "degree of anthropogenic impact" showed that the assessment does yield results, which follow water quality changes, provided that when SASS4 scores are less than 50, little attention is given to ASPT. At intermediate and high impacted sites ASPT did not follow habitat quality. However at low impacted water quality sites both SASS and ASPT tended to be greatest where habitat quality was the best. This study has identified that water quality "appears" to have a greater effect on macro invertebrate communities than the physical habitat and SASS distinguished sites with differing levels of water quality. This method was not designed to enable the exact nature of the disturbance to be determined, and it was intended that once an impairment of water quality had been established, it would be further assessed via intensive chemical and other studies. The use of more ecological indicators for example the inclusion of IHAS (version 2c) allowed a more comprehensive assessment of river health and more confidence could be linked to the outcome.
The physiology of flowering with contributions by in vitro techniques.
(1987) Dickens, Christopher William Spencer.; Van Staden, Johannes.
Abstract cannot be copied from pdf document.
The Kunene River mouth : managing a unique environment.
(2007) Paterson, John Richard Bernard.; Dickens, Christopher William Spencer.; Densham, Drummond.
The Kunene River Mouth (KRM) is one of only two river mouths in Namibia. The Kunene river and river mouth is bisected by the international border between Namibia and Angola, and lies between two protected areas, Iona National Park in Angola and Skeleton Coast Park in Namibia. The governments of Namibia and Angola have signed a Memorandum of Understanding (MoU) to link these two parks as a transfrontier park. This study further proposes a transfrontier Marine Protected Area to protect the marine environment surrounding the KRM and the Angola Benguela Front. The KRM is a fluvially dominated freshwater river mouth. The area is a biogeographically important biodiversity hotspot. The remoteness and pristine character contribute to the aesthetic appeal of the area. This study provides a profile of the KRM addressing its conservation value in terms of both biodiversity and aesthetic value, making use of the concept of “sense of place”. An analysis of all current and potential stakeholders is presented and their interests, activities and potential threats are evaluated. The main stakeholders are Government: the Ministry of Environment and Tourism, the Angolan Government, Ministry of Fisheries and Marine Resources, Namwater, Ministry of Mines and Energy, and the Kunene Regional Council. The private sector presently has a small stake in the area, with the exception of the Northern Namibia Development Corporation who is prospecting for diamonds at the KRM. Although the area has great tourism potential there is no tourism development currently underway or planned. The threat analysis suggests that the KRM is under severe threat from inappropriate development, both locally as well as within the catchment. Mining and prospecting were identified as the greatest threat, whereas tourism poses the least threat to the area. It is suggested that appropriate tourism is the most suitable development for this sensitive area. There is currently no coherent management strategy in place for the KRM. The current environmental legislation is ineffective. The need for a stringent adaptive management regime is identified and management goals for the area are suggested. It is further suggested that the concepts of “Thresholds of Potential Concern” and “Limits of Acceptable Change” are useful to monitor indicators for biophysical components and development activities respectively and to maintain a “Desired State” for the area. This “Desired State” must be the result of a participatory process. To be effective stakeholders must reach consensus on the “Desired State”. An eight step participatory process is proposed to develop and implement an adaptive management and development strategy for the KRM.