Penrhyn Estuary Habitat Enhancement Plan: Overview and Synthesis of Results

The Penrhyn Estuary Habitat Enhancement Plan is an ambitious project undertaken to increase the quantity and quality of roosting and feeding grounds for migratory shorebirds. Undertaken to compensate for habitat loss due to... [ view full abstract ]

The Penrhyn Estuary Habitat Enhancement Plan is an ambitious project undertaken to increase the quantity and quality of roosting and feeding grounds for migratory shorebirds. Undertaken to compensate for habitat loss due to the expansion of Port Botany, the project saw the most recent reshaping of the foreshore along the northern section of Botany Bay, which has undergone significant change since the 1940s. Shorebird habitat has decreased due to airport development and subsequent expansion and Foreshore Beach is currently a fraction of its previous length. Penrhyn Estuary, created between 1975 and 1978 has a legacy of pollution and supports a variety of bird predators but is nonetheless the only remaining shorebird roosting and feeding habitat of significant size along the northern shoreline of Botany Bay.
The main aim of the habitat enhancement plan was to sustainably expand and protect available roosting and feeding grounds for migratory shorebirds protected under international agreements. Key design features included levelling of foreshore sand dunes to create saltmarsh habitat, with sand used to fill deeper parts of the estuary to expand existing intertidal sand flats. Saltmarsh species planted were optimal for use as roosting habitat and extensive weed removal and maintenance has been undertaken. Sound barriers, lighting and fencing around the estuary and port structure were designed to maximise use by shorebirds and deter predators. A flushing channel was designed to ensure adequate tidal exchange in the estuary and to provide habitat suitable for seagrass beds.
The monitoring plans undertaken included surveys of shorebirds, benthic infaunal communities, planted and transplanted saltmarsh, remnant and transplanted seagrasses off Foreshore Beach and water quality within and outside of Penrhyn Estuary. Surveys were done within the estuary and at reference locations within a BACI framework.
This paper integrates the results of monitoring of all components before and after habitat enhancement to examine overall success of the project to date. It compares the status of saltmarsh and benthic communities with numbers of shorebirds to date. Issues considered include adequacy of indicators chosen, criteria for success of individual components, their inherent variability and selection of effective indicators of long-term ecosystem sustainability.