Coastal saltmarsh in the NSW North Coast, Sydney Basin and South East Corner bioregions - endangered ecological community listing

NSW Scientific Committee - final determination



Final Determination

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list the Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions, as an ENDANGERED ECOLOGICAL COMMUNITY in Part 3 of Schedule 1 of the Act. Listing of endangered ecological communities is provided for by Part 2 of the Act.

The Scientific Committee has found that:

1. Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions is the name given to the ecological community occurring in the intertidal zone on the shores of estuaries and lagoons including when they are intermittently closed along the NSW coast. Coastal saltmarsh has been recorded from sites along the NSW coast. (NSW North Coast, Sydney Basin and South East Corner Bioregions).

2. Characteristic vascular plant species of Coastal Saltmarsh are:

Baumea junceaIsolepis nodosa
Juncus kraussiiSamolus repens
Sarcocornia quinquefloraSelliera radicans
Sporobolus virginicusSuaeda australis
Triglochin striataZoysia macrantha

The total list of species is larger, with many species present in low abundance or at few sites. A more extensive list of species is provided by Adam et al. (1988). The sediment surface may support a diversity of both micro-algae and macro-algae.

3. Communities with similar floristic composition, but with a different fauna, are found supratidally on exposed headlands (Adam et al. 1988). These headland communities and those of inland saline areas are not included within this Determination of the Coastal Saltmarsh Ecological Community.

4. Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions provide habitat for a diverse invertebrate fauna, which includes both marine (crabs and molluscs) and terrestrial (insects and spiders) elements. During tidal flooding a number of fish species utilise saltmarsh habitats. Grazing by macropods may occur between tidal events. Some coastal saltmarshes provide important high tide roosts for migratory wading birds, and a range of other birds also utilise coastal saltmarsh as habitat. Diversity of macrofauna in mangrove forests adjacent to saltmarsh has been found to be greater than in mangroves that do not border saltmarsh (Yerman & Ross 2004)

5. Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions is frequently found as a zone landward of mangrove stands. Occasional scattered mature Avicennia marina trees occur through saltmarsh at some sites, and Avicennia (and less frequently Aegiceras corniculatum) seedlings may occur throughout saltmarsh. In brackish areas dense stands of tall reeds (Phragmites australis, Bulboschoenus spp., Schoenoplectus spp., Typha spp.) may occur as part of the community.

6. West et al. (1985) estimated the total area of coastal saltmarsh in NSW was approximately 5700 hectares distributed in fragmented patches mostly less than 100 hectares. Since this estimate, further reduction and fragmentation have occurred.

7. Species composition within Coastal Saltmarsh varies with elevation. Sarcocornia quinqueflora dominates at lower, and hence more frequently flooded, levels than Sporobolus virginicus which dominates the mid saltmarsh, while Juncus kraussii and Baumea juncea are upper saltmarsh species. There is also geographic variation, with much more extensive stands of Sporobolus virginicus being found in northern NSW, and conversely more extensive Sarcocornia quinqueflora stands in the south. Coastal Saltmarsh in southern NSW is generally more species rich than further north, with Austrostipa stipoides, Gahnia filum, Limonium australe and Sclerostegia arbuscula forming a characteristic southern suite of species. A number of other species with restricted distribution in Coastal Saltmarsh include Distichlis distichophylla (endangered), Halosarcia pergranulata subsp. pergranulata, Wilsonia backhousei (vulnerable) and Wilsonia rotundifolia (endangered).

8. Saltmarshes are globally threatened, and many of the threatening processes identified by Adam (2002) operate in NSW including infilling, modified tidal flow, weed invasion, damage by domestic and feral animals, human disturbance, altered fire regimes and climate change.

9. Historically, substantial areas of saltmarsh have been infilled for roads and aerodromes and for residential, recreational, waste disposal, industrial and agricultural purposes. With increased recognition of the ecological value of saltmarshes, the threat of further large-scale reclamation is less, but smaller scale infilling still occurs (Harty and Cheng 2003).

10. Patterns of tidal flow have been restricted by artificial structures in many NSW saltmarshes (Williams and Watford 1997), while discharge of stormwater alters salinity regimes, increases nutrient levels and facilitates the spread of Phragmites and weeds.

11. In recent decades there has been widespread invasion of saltmarsh in southeast Australia by mangroves (Mitchell and Adam 1989, Saintilan and Williams 1999, 2000). The factors driving mangrove invasion are still unclear. The mangrove invasion limits the use of saltmarshes by birds that would normally make use of this habitat and has been a factor in their decline (Saintilan 2003, Straw 1999, 2000).

12. A large number of weed species occur in NSW saltmarshes (Adam 1981, Adam et al. 1988). In terms of change to the community structure and function, the most serious weed is Juncus acutus; other major weeds include Baccharis halimifolia, Cortaderia selloana and Hydrocotyle bonariensis. The upper saltmarsh zone may be dominated by introduced annuals or shortlived perennials, including Parapholis incurva, Plantago coronopus and Polypogon monspeliensis.

13. Damage to saltmarshes by recreational vehicles, including four wheel drives, is widespread, and deep wheel ruts persist for many years even after exclusion of vehicles. Use of BMX and mountain bikes is increasing, and even saltmarshes within conservation reserves have been seriously damaged (Adam 2002).

14. Grazing and trampling by domestic stock and feral herbivores occurs at a number of sites. Stock grazing has been shown to substantially change the vegetation composition and structure (Adam 1990), while on muddy substrates trampling can cause loss of plant cover and modify drainage patterns.

15. Saltmarshes have frequently been used for casual rubbish dumping and are at risk from waterborne pollution - including oil and chemical spills, both from shipping and road accidents, and catchment runoff of nutrients and agricultural chemicals.

16. Upper saltmarsh stands dominated by Juncus kraussii and Baumea juncea have high flammable fuel loads. While the natural incidence of fire in saltmarshes is likely to have been low, a number of saltmarshes have been burnt in recent years. The recovery of these sites is relatively slow and the long-term impacts of burning are uncertain.

17. Global warming and increased relative sea level are likely to pose an increasing threat to the survival of many areas of Coastal Saltmarsh (Adam 2002, Hughes 2003).

18. Coastal Saltmarsh occurs in a number of conservation reserves including the Ramsar listed sites at Towra Point and Kooragang Island Nature Reserves. Reserve status, however, does not confer protection from mangrove and weed invasion, recreational vehicles, pollution, fire or sea level rise without active management.

19. In view of the above the Scientific Committee is of the opinion that the Coastal Saltmarsh in the NSW North Coast, Sydney Basin and South East Corner Bioregions is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival cease to operate.

 

Dr Lesley Hughes

Deputy Chairperson

Scientific Committee

 

Proposed Gazettal date: 04/06/04

Exhibition period: 04/06/04 - 16/07/04

 

Reference:

Adam P (1981) Australian saltmarshes. Wetlands (Australia) 1, 8-10.

Adam P (1990) Saltmarsh ecology. Cambridge University Press, Cambridge.

Adam P (2002) Saltmarshes in a time of change. Environmental Conservation 29, 39-61.

Adam P, Wilson NC, Huntley B (1988) The phytosociology of coastal saltmarsh vegetation in New South Wales. Wetlands (Australia) 7, 35-85.Harty C, Cheng D (2003) Ecological assessment and strategies for the management of mangroves in Brisbane Water - Gosford, New South Wales, Australia. Landscape and Urban Planning 62, 219-240.

Hughes L (2003) Climate change and Australia: Trends, projections and impacts. Austral Ecology 28, 423-443.

Mitchell ML, Adam P (1989) The decline of saltmarsh in Botany Bay. Wetlands (Australia) 8, 55-60.

Saintilan N (2003) The less obvious impacts of human settlement. In 'Straw P. (Ed). Status and Management of Migratory Shorebirds in Sydney. Sydney Olympic Park Authority.

Saintilan N, Williams RJ (1999) Mangrove transgression into saltmarsh environments in south-east Australia. Global Ecology and Biogeography 8, 117-124.

Saintilan N, Williams RJ (2000) The Decline of Saltmarshes in Southeast Australia: Results of Recent Survey. Wetlands (Australia) 18, 49-54.

Straw P (1999) Hunter River Estuary Wader Habitat Investigation. Unpublished report to NSW National Parks and Wildlife Service.

Straw P (2000) Hunter River Estuary Wader Habitat Investigation Stage 2. Unpublished report to NSW National Parks and Wildlife Service.

West R, Thorogood CA, Walford TJ, Williams RJ (1985) An estuarine inventory for New South Wales. Department of Agriculture, NSW. Fisheries Bulletin 2, Sydney

Williams RJ, Watford FA (1996) An inventory of impediments to tidal flow in NSW estuaruine fish habitats Wetlands (Australia) 15, 44-54.

Yerman MN, Ross PM (2004) Landscape issues for the macrofauna in temperate urban mangrove forests. In "Urban Wildlife more than meets the eye". (Ed. D Lunney and S Burgin) pp. 205-210. (Royal Zoological Society of NSW, Mosman, NSW).


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Page last updated: 27 February 2011