Ecological systems

The following description of the subregion is taken from the former Hunter-Central Rivers Catchment Management Authority (CMA) (DECCW, 2010a), the boundary of which was used when the Hunter subregion was defined in 2012. The former CMA covered an area of approximately 3.7 million hectares on the east coast of NSW, and extended from Newcastle in the east to the Merriwa Plateau and Great Dividing Range in the west, and from Taree in the north to Gosford in the south. The climate is subtropical with the greatest rainfall in coastal areas and the Barrington Tops; rainfall decreases further inland (see Section for more detail). Major waterways are Port Stephens; the Manning, Karuah and Hunter rivers; and the coastal lakes of Wallis Lake, Lake Macquarie, Tuggerah Lake and Brisbane Water.

The Hunter Valley is of great ecological significance because (i) it represents the only major break in the Great Dividing Range and therefore provides a link between coastal and inland NSW and (ii) it contains an area of overlap between tropical and temperate zones known as the MacPherson-Macleay Overlap (Burbidge, 1960) in which the limits of many taxa are found. The CMA contains two World Heritage-listed areas – the Greater Blue Mountains and the Barrington Tops – as well as internationally significant wetlands listed under the Ramsar Convention on Wetlands including Myall Lakes and Hunter Estuary (McCauley, 2006). It contains approximately 116 national parks and nature reserves. The 2010 New South Wales State of the Catchments (DECCW, 2010b) reported 126 species of flora and 152 species of fauna within the Hunter-Central Rivers CMA that are listed under either the Threatened Species Conservation Act 1995 (the TSC Act) or the NSW Fisheries Management Act 1994.

The main bioregions defined by the Interim Biogeographic Regionalisation for Australia (IBRA; Environment Australia, 2000) that are also within the Hunter subregion are the Sydney Basin (mainly Hunter, Kerrabee, Wyong, Yengo and Wollemi IBRA subregions), which accounts for 77% of the subregion, and the Brigalow Belt South (mainly the Liverpool Range IBRA subregion), which accounts for 20% of the subregion (see Section 1.1.3). The remaining 3% is within the NSW North Coast and Nandewar IBRA bioregions. The key IBRA bioregions are described in detail in Table 14 (see also Figure 6 in Section 1.1.1).

Table 14 Key bioregions from the Interim Biogeographic Regionalisation for Australia within the Hunter subregion

IBRAa classification


Characteristic landforms

Typical soils


Sydney Basin bioregion

Hunter subregion

A complex of Permian shales, sandstones, conglomerates, volcanics and coal measures. Bounded on the north by the Hunter Thrust fault and on the south by cliffs of Narrabeen Sandstone.

Pleistocene coastal barrier system in Newcastle bight. Rolling hills, wide valleys, with a meandering river system on a wide floodplain. River terraces are evident, the highest with silicified gravels. Streams can be brackish or saline at low flow. Numerous small swamps in upper catchment, extensive estuarine swamps behind the coastal barrier of beach and dunes.

A variety of harsh texture contrast soils on slopes and deep sandy loam alluvium on the valley floors. Small number of source bordering dunes on southern tributaries of the Hunter. Deep sands with Podosol profiles in dunes on the barrier, saline, organic muds in the estuary. Soil salinity is common on some bedrocks in the upper catchment.

Patches of rainforest brush in the lower valley. Forest and open woodland of white box, forest red gum, narrow-leaved ironbark, grey box, grey gum spotted gum, rough-barked apple and extensive of stands of swamp oak in upper reaches and foothills. River oak and river red gum along the streams. Coastal dune vegetation of blackbutt, smooth-barked apple, coast banksias and swamp mahogany. Mangroves, salt marsh and freshwater reed swamps in the estuary.

Kerrabee subregion

Triassic Narrabeen Group quartz and lithic sandstones and shales. Singleton coal measures exposed in valley floors. Numerous volcanic necks of Jurassic age and small areas of ridge top Cenozoic basalt flows. Quaternary sandy alluvium in main valleys.

Sandstone plateau with cliffed edges into wide valleys with sandy alluvial fill. Volcanic necks form circular depressions or low domes depending on relative erodibility of adjacent rock types.

Shallow sandy profiles, bare rock outcrop on plateau. Sandy texture contrast soils on slopes, harsh texture contrast soils on coal measures, deep sands and loams in alluvium. Basalts have red brown structured loams and clay loams, often buried by slope debris where the volcanic necks form depressions.

Yellow bloodwood, broad-leaved ironbark, rough-barked apple, grey gum with scribbly gum and shrubs and patches of dry heath on plateau. Rough-barked apple, forest red gum, grey box, white box, yellow box, fuzzy box, with Queensland blue grass and three-awned spear grass in valleys. River oak on the main streams. Volcanic necks and domes always support distinctive local vegetation, usually a box with grassy understorey.

Wollemi subregion

Hawkesbury Sandstone and equivalent quartz sandstones of Narrabeen Group, subhorizontal bedding, strong vertical joint patterns. A few volcanic necks.

Highest part of the Blue Mountains. Sandstone plateau with benched rock outcrops. Creek directions controlled by jointing deep gorge of the Capertee and Wolgan Rivers.

Thin sands or deep yellow earths on plateau, thin texture contrast soils on shale benches. Organic sands in swamps and joint crevices, bouldery slope debris below cliffs, sandy alluvium in pockets along the streams. Red brown structured loams on basalts.

Red bloodwood, yellow bloodwood, rough-barked apple, smooth-barked apple, hard-leaved scribbly gum, and grey gum with diverse shrubs and heaths on plateau. Smooth-barked apple, Sydney peppermint, blue-leaved stringybark, and turpentine and gully rainforests in gullies and canyon heads. Ribbon gum and Blaxland’s stringybark on basalt. River oak along main streams.

Yengo subregion

Triassic Hawkesbury Sandstone, valleys incised to Narrabeen sandstone, a few volcanic necks and basalt caps, Quaternary sandy alluvium and high level sands on Mellong Range and Maroota. Quaternary muddy sands in Hawkesbury upper estuary.

Benched sandstone plateau with steep slopes into narrow valleys with low cliff lines on Narrabeen sandstone. Structurally controlled subrectangular drainage pattern. Northern end of Lapstone monocline controls Mellong Range. Hawkesbury River gorge cuts across the subregion, tributary streams dammed by levees form freshwater swamps adjacent to the river.

Shallow quartz sands on plateau, some areas of deep yellow earth and patches of Podosol development on sandstone benches and in all Cenozoic and Quaternary high level sands. Texture contrast soils on shales, deep clean sands in alluvium. Red brown structured loams and clay loams on basalt.

Red bloodwood, yellow bloodwood, rough-barked apple, smooth-barked apple, hard-leaved scribbly gum, and grey gum with diverse shrubs and heaths on plateau. Smooth-barked apple, Sydney peppermint, blue-leaved stringybark, and turpentine with rainforest species in gullies. Hard-leaved scribbly gum, rough-barked apple and Parramatta red gum with sedge swamps on Mellong Range sand. River mangrove and grey mangrove along margins of upper Hawkesbury estuary, freshwater reed swamps with sedges and paperbarks.

Wyong subregion

Triassic Narrabeen sandstones, Quaternary estuarine fills, and coastal barrier complexes.

Coastal fall of the Sydney Basin, rolling hills and sandstone plateau outliers. Beach, dune and lagoons of coastal barriers interspersed with coastal cliffs and rock platforms.

Texture contrast soils on lithic sandstones and shales. Loamy sands alluvium along creeks clean quartz sands on beaches and frontal dunes, Podosols in older hind dunes. Organic sands and muds in lagoons and swamps.

Smooth-barked apple, red bloodwood, brown stringybark, Sydney peppermint, spotted gum, bastard mahogany, northern grey ironbark and grey gum on hills and slopes. Prickly-leaved tea-tree and other shrubs with swamp mahogany, swamp oak, sedges and common reed on swampy creek flats. Open heath with banksia, tea-tree, coastal wattle, black she-oak and smooth-barked apple on barrier dunes. Limited areas of grey mangrove.

Brigalow Belt South bioregion

Liverpool Range subregion

Multiple Cenozoic basalt flows with intervening sediments and ash fall material, overlying Jurassic quartz sandstones and shale.

Undulating plateau top with steep margins grading to long footslopes.

Stony red brown loams on ridges, shallow stony clay soils on steep slopes grading to deep black earths on lower slopes.

Plateau: open forest of silvertop stringybark, manna gum and mountain gum. Snow gum in cold air drainage hollows.Tallow wood, blackbutt and blue gum on eastern slopes, small areas of vine forest. Slopes:White box with rough-barked apple, belah in the creeks on northern aspects. Yellow box and Blakely’s red gum on southern aspect.

aInterim Biogeographic Regionalisation of Australia (IBRA; Environment Australia, 2000)

Data: The Bioregions of New South Wales: their biodiversity, conservation and history (NSW National Parks and Wildlife Service, 2003)

Last updated:
18 January 2019
Thumbnail of the Hunter subregion

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