A framework for the economic valuation of wetland rehabilitation: case studies from South Africa
- Authors: Browne, Michelle
- Date: 2022-04-06
- Subjects: Wetland restoration South Africa , Wetland management South Africa , Ecosystem management South Africa , Ecosystem services South Africa , Ecosystem management Economic aspects South Africa , Wetland restoration Cost effectiveness South Africa
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/263560 , vital:53638 , DOI 10.21504/10962/263561
- Description: Wetlands are recognised as having the potential to contribute long-term benefits to society; wetland rehabilitation is undertaken to recover these benefits in response to widespread wetland degradation. Increasingly, there have been calls to value the benefits of wetland rehabilitation to justify further investment. Such is the case in South Africa. Furthermore, recent global agendas and targets for ecosystem restoration, such as the declaration of the Decade of Restoration 2021-2030, suggest increasing pressure on governments to implement rehabilitation and imply a concomitant increase in decision-making regarding where and how to rehabilitate. In response to these information needs, this thesis explores the economic valuation of wetland rehabilitation through a narrative review of the foundational theory of values and valuation, a quantitative review of applied wetland rehabilitation economic valuation studies, and the evaluation of five wetland rehabilitation projects from South Africa. Projects were selected as case studies to represent various rehabilitation goals and explore different contexts (urban-rural; beneficiary groups), the timing of the evaluation (ex ante, ex post) and value types and valuation methods. The final chapter of the thesis integrates the case study experiences with the findings of the theoretical research components to propose a framework for the valuation of wetland rehabilitation, which can be applied in South Africa, and more generally, to further demonstrate the values of wetland rehabilitation, and as a tool to guide wetland rehabilitation decision-making. While initially grounded in mainstream economics, the research led into a number of fields including philosophy, social-ecological systems and social-ecological relations thinking, several environmental science areas and livelihood and human well-being frameworks. A deeper look into economic theory and history revealed an evolution of thinking on the meaning of ‘value’ and view of ‘nature’ and numerous critiques of standard neoclassical economics. From the insights gained and the case study experiences, this thesis argues that the neoclassical economic perspective, especially combined with a monetary metric, is too restrictive, and arguably too abstract in its assumptions of human behaviour and reliance on mathematical models, as an overarching framework for the valuation of wetland rehabilition. This is not to suggest that standard economic valuation concepts and methods cannot be useful, as the research case studies illustrated, but rather that wetland valuation must be approached from a value pluralism perspective. To this end, the proposed framework offers a way to think beyond, or in addition to, standard economic approaches in articulating the values of wetland rehabilitation. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
- Authors: Browne, Michelle
- Date: 2022-04-06
- Subjects: Wetland restoration South Africa , Wetland management South Africa , Ecosystem management South Africa , Ecosystem services South Africa , Ecosystem management Economic aspects South Africa , Wetland restoration Cost effectiveness South Africa
- Language: English
- Type: Academic theses , Doctoral theses , text
- Identifier: http://hdl.handle.net/10962/263560 , vital:53638 , DOI 10.21504/10962/263561
- Description: Wetlands are recognised as having the potential to contribute long-term benefits to society; wetland rehabilitation is undertaken to recover these benefits in response to widespread wetland degradation. Increasingly, there have been calls to value the benefits of wetland rehabilitation to justify further investment. Such is the case in South Africa. Furthermore, recent global agendas and targets for ecosystem restoration, such as the declaration of the Decade of Restoration 2021-2030, suggest increasing pressure on governments to implement rehabilitation and imply a concomitant increase in decision-making regarding where and how to rehabilitate. In response to these information needs, this thesis explores the economic valuation of wetland rehabilitation through a narrative review of the foundational theory of values and valuation, a quantitative review of applied wetland rehabilitation economic valuation studies, and the evaluation of five wetland rehabilitation projects from South Africa. Projects were selected as case studies to represent various rehabilitation goals and explore different contexts (urban-rural; beneficiary groups), the timing of the evaluation (ex ante, ex post) and value types and valuation methods. The final chapter of the thesis integrates the case study experiences with the findings of the theoretical research components to propose a framework for the valuation of wetland rehabilitation, which can be applied in South Africa, and more generally, to further demonstrate the values of wetland rehabilitation, and as a tool to guide wetland rehabilitation decision-making. While initially grounded in mainstream economics, the research led into a number of fields including philosophy, social-ecological systems and social-ecological relations thinking, several environmental science areas and livelihood and human well-being frameworks. A deeper look into economic theory and history revealed an evolution of thinking on the meaning of ‘value’ and view of ‘nature’ and numerous critiques of standard neoclassical economics. From the insights gained and the case study experiences, this thesis argues that the neoclassical economic perspective, especially combined with a monetary metric, is too restrictive, and arguably too abstract in its assumptions of human behaviour and reliance on mathematical models, as an overarching framework for the valuation of wetland rehabilition. This is not to suggest that standard economic valuation concepts and methods cannot be useful, as the research case studies illustrated, but rather that wetland valuation must be approached from a value pluralism perspective. To this end, the proposed framework offers a way to think beyond, or in addition to, standard economic approaches in articulating the values of wetland rehabilitation. , Thesis (PhD) -- Faculty of Commerce, Economics and Economic History, 2022
- Full Text:
Development and assessment of gastric-retentive sustained release metronidazole microcapsules
- Authors: Makan, Anjana
- Date: 2017
- Subjects: Metronidazole , Drug delivery systems , Helicobacter pylori , High performance liquid chromatography , Gas chromatography , Drugs , Drugs Controlled release
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59240 , vital:27491
- Description: Helicobacter pylori is one of the most common pathogenic bacterial infections and is the leading cause of gastritis, gastroduodenal ulcer disease and gastric cancers. Studies have revealed the prevalence of Helicobacter pylori is high in many countries around the globe. Although Helicobacter pylori is highly sensitive to antimicrobial agents in vitro the clinical eradication rate of the disease is still low. The instability of API at gastric pH, low concentration of API in the gastric mucosa and short gastric residence times are the main reasons for poor eradication rates. The high prevalence rate of this disease necessitates the design and development of gastric-retentive site specific oral dosage forms for the optimized delivery of existing therapeutic molecules and may be an approach to improving the eradication rate of Helicobacter pylori. Metronidazole (MTZ) is a 5-nitroimidazole derivative that exhibits antibiotic and antiprotozoal activity. MTZ is used in combination with other compounds for the treatment of Helicobacter pylori in peptic ulcer disease. MTZ is a potential candidate for inclusion in a sustained release gastric-retentive delivery system that acts in the stomach and since it is unstable in the intestinal/colonic environment enhancing gastric residence time would be a therapeutic advantage. MTZ is a cost-effective therapy that exhibits good anti-microbial activity and has a favourable pharmacokinetic profile. A sustained release gastric-retentive formulation is therefore proposed as an approach to enhance the local delivery of MTZ and improve treatment outcomes for patients infected with Helicobacter pylori. A stability indicating Reversed-Phase High Performance Liquid Chromatography (RP- HPLC) method for the quantitation of MTZ in pharmaceutical dosage forms was developed and optimised using a Central Composite Design (CCD) approach. The RP-HPLC method was found to be linear, accurate, precise, sensitive, selective, and was applied to the analysis of MTZ in commercially available medicines. Preformulation studies were conducted as preparative work prior to manufacture gastric- retentive sustained release MTZ microcapsules. The experiments conducted were tailored for the development of sustained release MTZ microcapsules using a solvent evaporation method. The particle size and shape of the microcapsules was investigated using Scanning Electron Microscopy (SEM). MTZ- excipient compatibility studies were performed using Fourier Transform Infra-red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). The results revealed that no definite interaction between MTZ and intended excipients to be used for manufacture of MTZ formulations occurred. A solvent evaporation procedure was used for the manufacture of MTZ microcapsules. Preliminary formulations were manufactured using two different grades of Methocel® at various levels. In addition the impact of processing parameters on performance was also investigated. The formulations were assessed in terms of in vitro release, buoyancy, yield, encapsulation efficiency and microcapsule size. Formulation optimisation was undertaken using a CCD approach and numerical optimisation was used to predict an optimised formulation composition that would produce minimal initial MTZ release, maximum MTZ release at 12 hours and maximum buoyancy, encapsulation efficiency and yield. The kinetics of MTZ release from microcapsules was established by fitting in vitro release data to different mathematical models. Higuchi model and first-order model appeared to best fit the data as majority of the formulation batches had highest R2 values for these models. Short-term stability assessment of the optimised formulation was established by undertaking stability studies at 25°C/60% RH and 40°C/75%RH. No significant changes in any of the CQA were observed over 30 days of stability testing. A gas chromatographic (GC) method was developed and validated for the quantitation of residual acetone and n-hexane. The optimised formulation contained 213.60 ppm/g acetone and 25.23 ppm/g n-hexane which are well below the limits set for residual solvents. In conclusion, gastric-retentive sustained release MTZ microcapsules with potential for further development and optimisation have been successfully developed and assessed in these studies. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
- Authors: Makan, Anjana
- Date: 2017
- Subjects: Metronidazole , Drug delivery systems , Helicobacter pylori , High performance liquid chromatography , Gas chromatography , Drugs , Drugs Controlled release
- Language: English
- Type: Master's theses , text
- Identifier: http://hdl.handle.net/10962/59240 , vital:27491
- Description: Helicobacter pylori is one of the most common pathogenic bacterial infections and is the leading cause of gastritis, gastroduodenal ulcer disease and gastric cancers. Studies have revealed the prevalence of Helicobacter pylori is high in many countries around the globe. Although Helicobacter pylori is highly sensitive to antimicrobial agents in vitro the clinical eradication rate of the disease is still low. The instability of API at gastric pH, low concentration of API in the gastric mucosa and short gastric residence times are the main reasons for poor eradication rates. The high prevalence rate of this disease necessitates the design and development of gastric-retentive site specific oral dosage forms for the optimized delivery of existing therapeutic molecules and may be an approach to improving the eradication rate of Helicobacter pylori. Metronidazole (MTZ) is a 5-nitroimidazole derivative that exhibits antibiotic and antiprotozoal activity. MTZ is used in combination with other compounds for the treatment of Helicobacter pylori in peptic ulcer disease. MTZ is a potential candidate for inclusion in a sustained release gastric-retentive delivery system that acts in the stomach and since it is unstable in the intestinal/colonic environment enhancing gastric residence time would be a therapeutic advantage. MTZ is a cost-effective therapy that exhibits good anti-microbial activity and has a favourable pharmacokinetic profile. A sustained release gastric-retentive formulation is therefore proposed as an approach to enhance the local delivery of MTZ and improve treatment outcomes for patients infected with Helicobacter pylori. A stability indicating Reversed-Phase High Performance Liquid Chromatography (RP- HPLC) method for the quantitation of MTZ in pharmaceutical dosage forms was developed and optimised using a Central Composite Design (CCD) approach. The RP-HPLC method was found to be linear, accurate, precise, sensitive, selective, and was applied to the analysis of MTZ in commercially available medicines. Preformulation studies were conducted as preparative work prior to manufacture gastric- retentive sustained release MTZ microcapsules. The experiments conducted were tailored for the development of sustained release MTZ microcapsules using a solvent evaporation method. The particle size and shape of the microcapsules was investigated using Scanning Electron Microscopy (SEM). MTZ- excipient compatibility studies were performed using Fourier Transform Infra-red Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD). The results revealed that no definite interaction between MTZ and intended excipients to be used for manufacture of MTZ formulations occurred. A solvent evaporation procedure was used for the manufacture of MTZ microcapsules. Preliminary formulations were manufactured using two different grades of Methocel® at various levels. In addition the impact of processing parameters on performance was also investigated. The formulations were assessed in terms of in vitro release, buoyancy, yield, encapsulation efficiency and microcapsule size. Formulation optimisation was undertaken using a CCD approach and numerical optimisation was used to predict an optimised formulation composition that would produce minimal initial MTZ release, maximum MTZ release at 12 hours and maximum buoyancy, encapsulation efficiency and yield. The kinetics of MTZ release from microcapsules was established by fitting in vitro release data to different mathematical models. Higuchi model and first-order model appeared to best fit the data as majority of the formulation batches had highest R2 values for these models. Short-term stability assessment of the optimised formulation was established by undertaking stability studies at 25°C/60% RH and 40°C/75%RH. No significant changes in any of the CQA were observed over 30 days of stability testing. A gas chromatographic (GC) method was developed and validated for the quantitation of residual acetone and n-hexane. The optimised formulation contained 213.60 ppm/g acetone and 25.23 ppm/g n-hexane which are well below the limits set for residual solvents. In conclusion, gastric-retentive sustained release MTZ microcapsules with potential for further development and optimisation have been successfully developed and assessed in these studies. , Thesis (MSc) -- Faculty of Pharmacy, Pharmacy, 2017
- Full Text:
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