The use of gabions as a tool for ecological engineering
- Authors: Seath, Jessica Lauren
- Date: 2024-04-04
- Subjects: Ecological engineering South Africa Knysna Lagoon , Gabion , Barrier structure , Coastal zone management , Coastal engineering , Estuarine health South Africa Knysna Lagoon , Estuarine animals Monitoring South Africa Knysna Lagoon
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434987 , vital:73121
- Description: Anthropogenic activities are centred in coastal ecosystems, including the development of harbours and/or marinas. The artificial structures used in coastal development typically has a different composition, orientation and level of complexity to that of natural ecosystems contributing to loss of biodiversity and increased incidence of invasive species. Ecological engineering research is attempting to identify different types of structures and materials that can increase species diversity and target species of conservation concern in coastal systems. The aim of this study was to investigate the efficacy of gabions (rock filled structures) as an ecological engineering tool by comparing community structure on these structures with pre-existing seawall structures within a small harbour and marina in South Africa (Knysna Harbour). The objectives of the study were to compare the differences in; 1) fish and; 2) colonising organisms’ diversity and composition between two artificial structures. Thirteen gabion boxes were deployed in Knysna Harbour and together with corresponding seawalls, monitored quarterly over a period of 12 months (August 2020 – August 2021) to assess taxon and functional richness, diversity, abundance and composition of fish, invertebrate and algal species. Physico-chemical characteristics of the water body were also monitored quarterly. Remote underwater video systems were used to quantify MaxN (maximum number of a fish species in the frame at any one time during each set that gives an indication of relative abundance) and identify fish species. The results of the two-way crossed ANOVAs indicated that gabion habitats recruited greater numbers and more types of fish species and from more functional groups than the seawalls, especially omnivorous and carnivorous fish. Additionally, photoquadrats were used to quantify percentage cover, counts and to identify colonising taxa. The results of the two-way crossed ANOVAs indicated that gabions hosted greater numbers of species resulting in a higher overall diversity and abundance of colonising organisms than seawalls. By contrast, the seawalls supported more types of functional groups of colonising organisms than gabions, largely due to abundances of different algal species. The results from the crossed PERMANOVAs indicated that the composition of fish and colonising organisms were vastly different from one another, and that each habitat was supporting very different functional groups. Results indicate that whilst both gabions and seawalls contain several alien species, that the ratio of native to alien species is higher in gabion habitats. Additionally, this research observed that gabion structures hosted four species listed on the IUCN Red List of Threatened Species. This study has highlighted that the use of gabions (with their natural increased complexity) could be important to consider for the future of urban coastal development in harbours such as in Knysna Harbour. Ecological engineering projects using gabions have the potential to be used in South Africa in projects that aim at increasing biodiversity in urban coastal environments. As well as increasing the settlement and abundance of habitat-forming ecosystem engineers to ensure the long-term stability of these ecosystems. They can be used both in the development of new costal development projects as well as in an ad-hoc fashion where they can be interspersed on seawalls in harbours. Additionally, gabions have the potential to be used in projects that target species of conservation concern such as the endangered Knysna Seahorse (Hippocampus capensis). It is, however, important to monitor the invasion by non-native species in future ecological engineering projects in South Africa as well as their potential for creating ecological traps (a situation in which an organism may be convinced to settle in a low-quality habitat) for certain species. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-04
- Authors: Seath, Jessica Lauren
- Date: 2024-04-04
- Subjects: Ecological engineering South Africa Knysna Lagoon , Gabion , Barrier structure , Coastal zone management , Coastal engineering , Estuarine health South Africa Knysna Lagoon , Estuarine animals Monitoring South Africa Knysna Lagoon
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/434987 , vital:73121
- Description: Anthropogenic activities are centred in coastal ecosystems, including the development of harbours and/or marinas. The artificial structures used in coastal development typically has a different composition, orientation and level of complexity to that of natural ecosystems contributing to loss of biodiversity and increased incidence of invasive species. Ecological engineering research is attempting to identify different types of structures and materials that can increase species diversity and target species of conservation concern in coastal systems. The aim of this study was to investigate the efficacy of gabions (rock filled structures) as an ecological engineering tool by comparing community structure on these structures with pre-existing seawall structures within a small harbour and marina in South Africa (Knysna Harbour). The objectives of the study were to compare the differences in; 1) fish and; 2) colonising organisms’ diversity and composition between two artificial structures. Thirteen gabion boxes were deployed in Knysna Harbour and together with corresponding seawalls, monitored quarterly over a period of 12 months (August 2020 – August 2021) to assess taxon and functional richness, diversity, abundance and composition of fish, invertebrate and algal species. Physico-chemical characteristics of the water body were also monitored quarterly. Remote underwater video systems were used to quantify MaxN (maximum number of a fish species in the frame at any one time during each set that gives an indication of relative abundance) and identify fish species. The results of the two-way crossed ANOVAs indicated that gabion habitats recruited greater numbers and more types of fish species and from more functional groups than the seawalls, especially omnivorous and carnivorous fish. Additionally, photoquadrats were used to quantify percentage cover, counts and to identify colonising taxa. The results of the two-way crossed ANOVAs indicated that gabions hosted greater numbers of species resulting in a higher overall diversity and abundance of colonising organisms than seawalls. By contrast, the seawalls supported more types of functional groups of colonising organisms than gabions, largely due to abundances of different algal species. The results from the crossed PERMANOVAs indicated that the composition of fish and colonising organisms were vastly different from one another, and that each habitat was supporting very different functional groups. Results indicate that whilst both gabions and seawalls contain several alien species, that the ratio of native to alien species is higher in gabion habitats. Additionally, this research observed that gabion structures hosted four species listed on the IUCN Red List of Threatened Species. This study has highlighted that the use of gabions (with their natural increased complexity) could be important to consider for the future of urban coastal development in harbours such as in Knysna Harbour. Ecological engineering projects using gabions have the potential to be used in South Africa in projects that aim at increasing biodiversity in urban coastal environments. As well as increasing the settlement and abundance of habitat-forming ecosystem engineers to ensure the long-term stability of these ecosystems. They can be used both in the development of new costal development projects as well as in an ad-hoc fashion where they can be interspersed on seawalls in harbours. Additionally, gabions have the potential to be used in projects that target species of conservation concern such as the endangered Knysna Seahorse (Hippocampus capensis). It is, however, important to monitor the invasion by non-native species in future ecological engineering projects in South Africa as well as their potential for creating ecological traps (a situation in which an organism may be convinced to settle in a low-quality habitat) for certain species. , Thesis (MSc) -- Faculty of Science, Zoology and Entomology, 2024
- Full Text:
- Date Issued: 2024-04-04
Development role players' knowledge of ecological infrastructure in Eden district, South Africa
- Authors: Crisp, Abigail Gilmour
- Date: 2015
- Subjects: Climatic changes -- South Africa , Environmental management , Coastal engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8725 , vital:26424
- Description: Coastal disasters have been increasing in intensity and frequency around the world causing loss of life and millions of Rands’ worth of damage to infrastructure. Coastal communities are growing as more people are drawn to urban areas. These people depend on the services the coastal ecosystem provide but through degradation and land use change the supply of services is reduced. The ability of these communities and landscapes to bounce back from disturbance has been severely hampered. As a result communities are looking for ways in which they can protect their lives and their assets and become more resilient. Through development planning structures such as coastal foredunes, that offer a buffering capacity against storm surges, can be used to strengthen the resilience of coastal communities. The type of defences used in communities would be dependent on the knowledge of the decision makers. This study explores the discourses and practices that are present in development processes regarding ecological infrastructure (in its buffering capacity for risk reduction) as an option for adaptation to global environmental change in the coastal areas of Eden District. Qualitative data collection and analysis techniques were used. In-depth interviews were used to collect data, which was transformed into frequency data using content analysis. Descriptive statistics was then applied to the coded frequencies. The interpretation of the data was presented alongside the frequency data, via the descriptive statistics and quotations from interviews. It was determined that role players in development processes are aware of the complexities surrounding coastal social-ecological systems and understand the role foredunes play as ecological infrastructure within this system. Those who lack knowledge are aware of their knowledge gaps. Participants believe the study area is at risk due to human impacts and overall, participants felt that there is a general lack of awareness with regard to issues affecting our coastline, compounded by the absence of an enabling environment brought about by a lack of finances and time.
- Full Text:
- Date Issued: 2015
- Authors: Crisp, Abigail Gilmour
- Date: 2015
- Subjects: Climatic changes -- South Africa , Environmental management , Coastal engineering
- Language: English
- Type: Thesis , Masters , MTech
- Identifier: http://hdl.handle.net/10948/8725 , vital:26424
- Description: Coastal disasters have been increasing in intensity and frequency around the world causing loss of life and millions of Rands’ worth of damage to infrastructure. Coastal communities are growing as more people are drawn to urban areas. These people depend on the services the coastal ecosystem provide but through degradation and land use change the supply of services is reduced. The ability of these communities and landscapes to bounce back from disturbance has been severely hampered. As a result communities are looking for ways in which they can protect their lives and their assets and become more resilient. Through development planning structures such as coastal foredunes, that offer a buffering capacity against storm surges, can be used to strengthen the resilience of coastal communities. The type of defences used in communities would be dependent on the knowledge of the decision makers. This study explores the discourses and practices that are present in development processes regarding ecological infrastructure (in its buffering capacity for risk reduction) as an option for adaptation to global environmental change in the coastal areas of Eden District. Qualitative data collection and analysis techniques were used. In-depth interviews were used to collect data, which was transformed into frequency data using content analysis. Descriptive statistics was then applied to the coded frequencies. The interpretation of the data was presented alongside the frequency data, via the descriptive statistics and quotations from interviews. It was determined that role players in development processes are aware of the complexities surrounding coastal social-ecological systems and understand the role foredunes play as ecological infrastructure within this system. Those who lack knowledge are aware of their knowledge gaps. Participants believe the study area is at risk due to human impacts and overall, participants felt that there is a general lack of awareness with regard to issues affecting our coastline, compounded by the absence of an enabling environment brought about by a lack of finances and time.
- Full Text:
- Date Issued: 2015
- «
- ‹
- 1
- ›
- »