- Title
- Ecological studies in the restoration of estuarine wetland habitats in Eastern Australia
- Creator
- Nelson, Peter
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2006
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- There is worldwide recognition that extensive loss and degradation of habitat in estuarine wetlands has occurred as a result of human activities. This has led to environmental and economic concerns which have results in increasing social pressure to conserve remaining sites and to actively rehabilitate and restore estuarine wetlands are being realised. This study reports on research aspects of two large estuarine rehabilitation projects; the Kooragang Island Wetland Rehabilitation Project in the Hunter River Estuary on the central coast (151°E, 33°S) and the Yarrahapinni Wetland Rehabilitation Project in the Macleay River Estuary (153°E, 31°S) on the mid north coast of New South Wales, Australia. The aims of the two projects shared similarities, but the estuaries differed substantially in their hydrology and geomorphology and they had different recent histories with the Hunter Estuary being highly developed for industry and settlement, and the Macleay Estuary remaining largely rural. A primary objective of the research was to measure change in selected environmental parameters in order to gauge the success, reported here, in restoring 'healthy' estuarine wetlands. This improvement in ecosystem health would be achieved by restoring natural tidal flows by opening the floodgates at Yarrahapinni and replacing restrictive culverts at Kooragang which have for decades isolated the wetlands from the natural estuarine tidal influences. Scientific experiments and empirical observations were designed to test the general hypothesis that reinstatement of tidal influence in the wetlands would result in changes in the biotic and abiotic parameters that would in substantial measure then become similar to their former state. The studies examined water quality and estuarine organisms in order to gauge the relationships between the parameters and the ecological health of the biotic communities. Comparisons were made between the biological communities in the degraded wetlands and nearby estuarine sites designated as controls, which were assumed to be similar to the endpoint of proposed restoration efforts. A 'successful' rehabilitation of the wetland would be indicated by similarity to the control sites. The dataset gathered fro the wetland and the comparative sites in the Macleay River Estuary became a long term examination of spatial and temporal change which allowed a rare opportunity to monitor estuarine and degraded wetland biotic and abiotic parameters over an extended period. Measurements were made on selected water quality parameters, cover of wetland plant species, benthic macroinvertebrate species abundance and waterbird species abundance. The study confirms that prior to the impoundment of the Yarrahapinni Wetland the dominant estuarine vegetation communities were mangrove, saltmarsh and possibly seagrass. When the study commenced there were only small remnants of the once very extensive areas of these estuarine communities in the impounded wetland. Comparisons of historical aerial photography documented the existence of around 200 hectares of mangrove and more than 230ha of saltmarsh in the wetland prior to impoundment. Greater than 99% of the area of these estuarine vegetation communities were lost following impoundment with a consequent loss of habitat for the dependent fauna. The Hunter River study involved the investigation of change in the vegetation communities on five Kooragang Island tidal creek floodplains. The two creeks where tidal flows were to be restored were designated as experimental sites, and the three creeks where flows were not to be restored, as controls. The experimental design was modified, however, when removal of restrictions to tidal flows on one of the experimental creeks caused flooding into the adjacent control creek. Vegetation communities changed in the tidal creek floodplains in response to the altered tidal regimes, whilst the control creek vegetation remained largely unchanged over five years. A large experimental plot was constructed to determine whether saltmarsh on excavated upland. Growth, establishment and recruitment of selected saltmarsh species were investigated on an area of land excavated from the pasture adjacent to the marsh. The aim of this investigation was to instigate issues such as the design, implementation and assessment of saltmarsh habitat rehabilitation and creation. Together thesis investigations in the two estuaries indicate that restoration and rehabilitation of estuarine habitats is possible and practical, and provide strong environmental values which in turn will provide social and economic benefits. The combined empirical and experimental investigations indicate that with the restoration of tidal flows, water quality will improve and vegetation will reset to a condition resembling the communities prior to the truncation or restriction of the tidal regimes. Whilst it is difficult to predict with accuracy the timeframe and the trajectory of the outcomes it is clear that the desired natural estuarine vegetation will return with careful management. Unlike other terrestrial restorations, any successional stages the restoration goes through will be an interaction of the temporal development of the mangrove and saltmarsh communities rather than one community necessarily preparing the ground for the later community. There is evidence that the intertidal ranges of the two communities overlap somewhat and that mangrove is the competitive dominant. There is no evidence that saltmarsh is a necessary precursor to mangrove in this range. Examination of selected components of the estuarine ecosystems indicate that, with the restoration of tidal flows there will be a positive effect on estuarine benthic invertabrates and estuarine waterbird community diversity and productivity in the rehabilitated habitats. With the restoration of natural estuarine flora and fauna communities there is predicted to be an increase in ecosystem resources such as fish and shellfish nurseries and a reduction in costly episodes related to poor water quality.
- Subject
- Eastern Australia; estuarine wetland habitats; Kooragang Island Wetlands; Hunter River
- Identifier
- http://hdl.handle.net/1959.13/1312838
- Identifier
- uon:22467
- Rights
- Copyright 2006 Peter Nelson
- Language
- eng
- Full Text
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| Thumbnail | File | Description | Size | Format | |||
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| View Details Download | ATTACHMENT01 | Thesis | 35 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 151 KB | Adobe Acrobat PDF | View Details Download |