Biological values of Seven Mile Beach ecosystems.

The Seven Mile Beach National Park, together with adjoining native vegetation on private lands, forms a vulnerable, disconnected island of vegetation. Clearing, fragmentation of vegetation and loss of habitat has been a contentious issue more than 30 years.

Drainage canals have historically degraded Foys Swamp, Blue Angle Creek has been modified into a canal, acid sulphate contamination has polluted Crooked River and at least 80 hectares of biologically important forests (mostly Endangered Ecological Communities) have been cleared.

Bush fire compounds these impacts on the viability of native fauna (including endangered and vulnerable species). The koala appears to have become locally extinct since it was surveyed in 1980 and the Greater Glider has recently been listed as an Endangered Population.

The continuing viability of a biologically important suite of six Endangered Ecological Communities is under threat; some of these have been severely reduced and/or degraded due to sand quarrying. The most vulnerable remnant EECs are located on private lands identified as a sand resource in the Illawarra Regional Strategy, These include:

  1. Wetlands

Behind Seven Mile Beach are three interrelated wetland complexes. The freshwater wetlands form the largest ecosystem system of its type in NSW. The scale and biological complexity of the original vegetation assemblages associated with these wetlands was enormous.

Coomonderry Swamp drains to the Shoalhaven River at the southern end of the beach and covers an area of approximately 670 hectares. It represents nearly 40% of coastal freshwater wetlands in the State, and 90% of this wetland type on the south coast. It is partly protected within the National Park but is threatened by development within its immediate catchment.

West of the northern end of the beach, Foys Swamp is located Crooked River Road and the railway line. It covers an area of 120 hectares and drains along Blue Angle Creek to Crooked River. This unprotected freshwater swamp, although cleared and modified by drainage canals, retains its soil profile and hydrological functions. Importantly its intact soil profile prevents the further oxidation of acid sulphate soils. Fragments of Swamp Sclerophyll Forest exist at its margins. The Crooked River Estuary Management Plan states “Identify Foys Swamp as a significant freshwater wetland worthy of conservation”.

At the north western end of the beach are smaller freshwater and saline wetlands associated with Blue Angle Creek and Crooked River. The vegetation makeup associated with these wetlands is particularly complex and characterised by Littoral Rainforests in association with swamp forests, dune forests and wetland vegetation. 

  1. Vegetation

A beach, dune wetlands sequence, defines ecosystems associated with Seven Mile Beach. The scale of the wetlands and the association of freshwater and saline wetlands make it a habitat for scientifically important vegetation communities that support a number endangered and vulnerable species.

The vegetation sequence south of Berry Beach Road is different in make up to that associated with the Crooked River wetlands to the north, which is dominated by Littoral Rainforest.

The Endangered Ecological Communities found at Seven Mile Beach, listed under the NSW

Threatened Species Conservation Act, include:

  1. Swamp Oak Floodplain Forest of the New South Wales North Coast, Sydney Basin and South East Corner Bioregions
  2. Swamp Sclerophyll Forest on Coastal Floodplains of the New South Wales North Coast, Sydney Basin and South East Corner Bioregions
  3. Freshwater Wetlands on Coastal Floodplains of the New South Wales North Coast, Sydney Basin and South East Corner Bioregions
  4. Littoral Rainforest in the New South Wales North Coast, Sydney Basin and South East Corner Bioregions
  5. Bangalay Sand Forest of the Sydney Basin and South East Corner bioregions
  6. Coastal Saltmarsh in the New South Wales North Coast, Sydney Basin and South East Corner Bioregions

Also Blackbutt dune forests occupy the SMB hind dunes – these forests are undergoing significant clearing for sand mining – This vegetation community is the primary habitat of the greater glider and a number of greater glider colonies survive on the fringes of these fragmented dune forests and in the adjoining national park. The habitat area needed for this species to remain viable may already be too small to sustain this population and, as there is no avenue to replenished diminishing populations from adjoining lands, they are under threat of local extinction.  The Seven Mile Beach Greater glider population has been recently declared an Endangered Population.

These vegetation communities are not all well represented within the Seven Mile Beach National Park, significant Endangered Ecological Communities remain unprotected on private lands and these have suffered from clearing for farming, urban encroachment, golf course extension and sand quarrying.

Howard H Jones

Secretary Gerroa Environmental Protection Society