6.4 LOSS AND DEGRADATION OF COASTAL WETLANDS Coastal wetlands in the Manning estuary are under significant threat from development, modified hydrology and the impacts of climate change. Key activities and stressors include: • agricultural land use and associated floodplain draining and stock access • urban development and associated filling • degradation by pollutants such as acid drainage, increased nutrients and sediment loads • clearing and fragmentation of vegetation • climate change (particularly sea level rise) and drought • weed and pest invasion • inappropriate fire regimes • general ignorance of wetlands values30. Most estuarine habitats including mangroves and saltmarsh were rated poor or fair in the Rapid Site Assessment.31 Mangrove extent and connectivity has been reduced to narrow, patchy bands, rarely exceeding 10m wide, providing limited bank protection from high flows and boat wash. Distribution of saltmarsh identified through the Rapid Site Assessments was very low. Stock impact on coastal wetlands and fringing vegetation was found to be a widespread threat to estuary health. Stock frequently have access to estuarine shorelines and wetlands leading to soil degradation, erosion, reduced vegetation and poor water quality. Weed abundance within mapped wetlands was relatively low. Environmental weeds such as Lantana, Bitou Bush, Tree Pear, Coastal Morning Glory and Cassia were becoming established in some wetlands, particularly on the floodplain. Several Swamp Oak and Mangrove Forests were observed to be dominated by an understorey of the invasive weed Juncus acutus (Sharp Rush) which should be prioritised for treatment.32. Sambar deer, foxes, hares and gambusia fish are present in Cattai Wetlands. Deer trample and graze on wetland vegetation. Foxes prey on native species, particularly impacting threatened and migratory shorebirds near the north and south entrances.
30: Eco Logical Australia Pty Ltd, 2019 31: Swanson, 2020 32: Eco Logical Australia Pty Ltd, 2019
Stakeholders include: MidCoast Council, Hunter LLS, DPIE, DPI-Fisheries, NSW Government, NPWS, WRL; private landholders, Mid Coast 2 Tops Landcare, DPIE - Crown Lands, Recreational and Commercial Fishers, community. Related issues: Floodplain drainage and acid sulfate soils, biodiversity.
Manning River Estuary and Catchment Management Program (ECMP)
81
