Government Guidelines and Legislation
Freshwater Wetlands on Coastal Floodplains - Endangered Ecological Community Profile
August 2007
Source:
Department of Environment and Climate Change
www.threatenedspecies.environment.nsw.gov.au
Scientific name: Freshwater wetlands on coastal floodplains of the NSW North Coast, Sydney Basin and South East Corner bioregions
Conservation status in NSW: Endangered Ecological Community
Description
Freshwater wetlands are associated with coastal areas subject to periodic flooding and in which standing fresh water persists for at least part of the year in most years. They typically occur on silts, muds or humic loams in low-lying parts of floodplains, alluvial flats, depressions, drainage lines, backswamps, lagoons and lakes but may also occur in backbarrier landforms where floodplains adjoin coastal sandplains. Generally occur below 20 m elevation on level areas.
Freshwater Wetlands on the Coastal Floodplain are dominated by herbaceous plants and have very few woody species. The structure and composition of the community varies both spatially and temporally depending on the water regime:
- Those that lack standing water most of the time are usually dominated by dense grassland or sedgeland vegetation, often forming a turf less than 0.5 metre tall and dominated by amphibious plants including Paspalum distichum (water couch), Leersia hexandra (swamp rice-grass), Pseudoraphis spinescens (mud grass) and Carex appressa (tussock sedge).
- Where they are subject to regular inundation and drying the vegetation may include large emergent sedges over 1 metre tall, such as Baumea articulata, Eleocharis equisetina and Lepironia articulata, as well as emergent or floating herbs such as Hydrocharis dubia (frogbit), Philydrum lanuginosum (frogsmouth), Ludwigia peploides subsp. montevidensis (water primrose), Marsilea mutica (nardoo) and Myriophyllum spp. (milfoils).
- As standing water becomes deeper or more permanent, amphibious and emergent plants become less abundant, while floating and submerged aquatic herbs become more abundant. These latter species include Azolla filiculoides var. rubra, Ceratophyllum demersum (hornwort), Hydrilla verticillata (water thyme), Lemna spp. (duckweeds), Nymphaea gigantea (giant waterlily), Nymphoides indica (water snowflake), Ottelia ovalifolia (swamp lily) and Potamageton spp. (pondweeds).
The threatened aquatic plants, Aldrovanda vesiculosa and Najas marina, also occur within this community. For a comprehensive list of species that characterize the community, see: http://www.nationalparks.nsw.gov.au/npws.nsf/Content/freshwater_wetlands_endangered
Location and habitat
Distribution
Freshwater wetlands are known from along the majority of the NSW coast. However, this Endangered Ecological Community (EEC) is distinct from the EEC Sydney Freshwater Wetlands which are associated with sandplains in the Sydney Basin bioregion.
Extensively cleared and modified, the extent of Freshwater Wetlands remaining in the 1990’s were:
- 3% in the NSW North Coast bioregion,
- 66% in the lower Hunter – Central coast region,
- 40% on the Cumberland Plain,
- 70% in the Sydney – South Coast region, and
- 30% in the Eden region.
There is less than 150 ha remaining on the Tweed lowlands (estimate in 1985); about 10,600 ha on the lower Clarence floodplain (in 1982); about 11,200 ha on the lower Macleay floodplain (in 1983); about 3,500 ha in the lower Hunter – Central Hunter region (in 1990s); less than 2,700 ha on the NSW south coast from Sydney to Moruya (in the mid 1990s), including about 660 ha on the Cumberland Plain (in 1998) and about 100 ha on the Illawarra Plain (in 2001); and less than 1000 ha in the Eden region (in 1990).
Freshwater Wetlands on Coastal Floodplains are poorly reserved. They are known to occur in Ukerebagh, Tuckean, Tabbimoble Swamp, Hexham Swamp, Pambalong and Pitt Town Nature Reserves and Bungawalbin, Scheyville and Seven Mile Beach National Parks.
Regional information
This species is found in the following catchment management authority regions. Click on a region name to see more details about the distribution, vegetation types and habitat preference of the species in that region.
Threats
- Land clearing
- Continuing fragmentation and degradation
- Flood mitigation and drainage works
- Filling associated with urban and industrial development
- Pollution and eutrophication from urban and agricultural runoff
- Weed invasion
- Overgrazing, trampling by livestock
- Soil disturbance by pigs
- Activation of acid sulfate soils
- Dumping of landfill, rubbish and garden refuse
- Native fauna is threatened by predation, particularly by mosquito fish and cane toads
- Anthropogenic climate change
What needs to be done to recover this threatened community?
- Instigate enforcement and education campaigns to reduce dumping.
- Instigate pig control programs.
- Install stormwater control mechanisms to prevent off-site impacts from adjacent development.
- Control access of cattle to wetlands by installing fencing.
- Undertake weed control as required using removal methods that will not damage the community.
- Protect and actively manage wetlands through conservation mechanisms such as placing covenants on land and the preparation/implementation of site-specific vegetation management plans.
- Restore natural drainage conditions.
