Nature conservation

Biodiversity Reform

Sydney Basin - biodiversity

Plant communities

The Sydney Basin Bioregion is one of the most species diverse in Australia. This is a result of the variety of rock types, topography and climates in the bioregion.

The frontal dunes along the coastal area of the bioregion supports coast tea-tree (Leptospermum laevigatum), coast wattle (Acacia longifolia) and coast banksias (Banksia aemula, B. serrata, B. integrifolia), often with grass tree (Xanthorroea sp.) and lomandra (Lomandra longifolia).

Dunes generally support vegetation communities dominated by old man banksia (Banksia serrata), smooth-barked apple (Angophora costata), red bloodwood (Corymbia gummifera) and blackbutt (Eucalyptus pilularis) with a diverse shrub layer. The oldest dunes, which lie on the inland side of the coastal barrier or are found as parabolic dunes high in the landscape, such as on headlands, support a mature coastal forest community.

Estuaries are characterised by a swamp oak (Casuarina glauca), common reed (Phragmites australis), saltmarsh (Juncus kraussii, Sporobulus virginicus, and Sarcocornia quinqueflora) and mangrove (Aegiceras corniculatum and Avicennia marina) sequence. The boundaries of these communities are dynamic due to present day geomorphic processes.

Rainforest communities are characterised by coachwood (Ceratopetalum apetalum), native tamarind (Diploglottus australis), white cherry (Schizomeria ovata), cheese tree (Glochidion ferdinandi), lilly pilly (Acmena smithii), blackwood (Acacia melanoxylon) and Port Jackson fig (Ficus rubiginosa), with soft tree fern (Dicksonia antarctica) and rough tree fern (Cyathea australis) common in the understorey.

The adjacent tall forests are dominated by Sydney peppermint (Eucalyptus piperita), narrow-leaved peppermint (Eucalyptus radiata), messmate (Eucalyptus obliqua), brown barrel (Eucalyptus fastigata), yellow stringybark (Eucalyptus muellerana), coastal white box (Eucalyptus quadrangulata), blackbutt, turpentine (Syncarpia glomulifera), Deane's gum (Eucalyptus deanei), bangalow palm (Archontophoenix cunninghamiana), cabbage tree palm (Livistonia australis), forest oak (Allocasuarina torulosa) and the creekline species, water gum (Tristania laurina).

Species composition and the structural form of the vegetation communities occupying extensive sandstone plateaus vary with altitude and rainfall. Common trees include red bloodwood, yellow bloodwood (Corymbia eximia), rough-barked apple (Angophora floribunda), smooth-barked apple, hard-leaved scribbly gum (Eucalyptus sclerophylla), grey gum (Eucalyptus punctata), black ash (Eucalyptus sieberi), Sydney peppermint, blue-leaved stringybark (Eucalyptus agglomerata), turpentine, brown stringybark (Eucalyptus capitellata) and northern grey ironbark (Eucalyptus siderophloia).

Drier, lowland environments, such as the upper Hunter, Cerrabee and Cumberland Plain support forests and woodlands dominated by forest red gum (Eucalyptus tereticornis), grey gum, spotted gum (Eucalyptus maculata), scribbly gum (Eucalyptus haemastoma), grey box (Eucalyptus moluccana), white box, yellow box (Eucalyptus melliodora), fuzzy box (Eucalyptus conica), narrow-leaved ironbark (Eucalyptus crebra), broad-leaved ironbark (Eucalyptus fibrosa), rough-barked apple, yellow bloodwood and extensive stands of swamp oak.

Riparian vegetation is dominated by river oak (Casuarina cunninghamiana) through most of the basin, with river red gum (Eucalyptus camaldulensis) occurring in the Hunter and water gum occupying the wetter, more protected environments.

Swamp vegetation ranges from monocultures of common reed to complex prickly-leaved tea-tree (Melaleuca stypheloides) and paperbark (Melaleuca quinquenervia) associations, with swamp mahogany (Eucalyptus robusta), swamp oak, sedges, tall spike rush (Elaeocharis sphacelata) and juncus (Juncus sp.) Hanging swamps can be found on sandstone and dunes, with the dominant species being gahnia (Gahnia aspera) and banksia (Banksia robur). A raised sphagnum bog (Sphagnum sp.) is located at Wingecarribee, an uncommon vegetation community in the Sydney Basin.

Coastal forest characterised by Sydney blue gum (Eucalyptus saligna), blackbutt, turpentine, grey ironbark (Eucalyptus paniculata), spotted gum, black ash and bangalay (Eucalyptus botryoides) occupies shale-derived soils capping sandstone and along parts of the coastal ramp. These often have an open understorey, with macrozamia (Macrozamia communis) and cabbage tree palm.

Significant flora

Wollemi National Park, the largest reserve in the bioregion, protects many threatened species as well as species whose distribution is restricted entirely to the bioregion. Such flora species include Apatophyllum constablei, Acacia asparagoides, Eucalyptus bensonii and Rupicola decumbens, all of which are locally endemic (NSW NPWS 2002).

The recently discovered Wollemi Pine (Wollemia nobilis) occurs only in a very restricted part of the bioregion. It is a relict of the Gondwanan era (60-200 million years ago) found in a remote canyon in Wollemi National Park (NSW NPWS 2002). It is now listed as endangered in the TSC Act.

Important vegetation communities include yellow box - ironbark woodlands in the northern escarpments of the bioregion. These woodlands are thought to provide important habitat for species such as the regent honeyeater (Xanthomyza phrygia), but are not well represented in conservation reserves in the bioregion (NSW NPWS 2002). Mellong Swamp in the Wollemi National Park is another unique plant community, which provides important habitat for both reptiles and invertebrates in the bioregion (NSW NPWS 2002).

In total there are 92 vulnerable and 60 endangered plant species in the bioregion (Australian Terrestrial Biodiversity Assessment 2002).

Significant fauna

Threatened species recorded in the bioregion include the brush-tailed rock wallaby (Petrogale penicillata), koala (Phascolarctos cinereus), yellow-bellied glider (Petaurus australis), brush-tailed phascogale (Phascogale tapoatafa), tiger quoll (Dasyurus maculatus), broadheaded snake (Hoplocephalus bungaroides), glossy black cockatoo (Calyptorhyncus lathami), turquoise parrot (Neophema pulchella) and powerful owl (Ninox strenua) (NSW NPWS 2002).

The Sydney Basin Bioregion is home to 2 endangered and 4 vulnerable frog species, 54 vulnerable and 14 endangered bird species, 25 vulnerable, 3 endangered and one extinct mammal species, and 11 vulnerable and 2 endangered reptile species.

Although the Sydney Basin Bioregion has the highest human population of any NSW bioregion, significant areas of native vegetation remain unchanged since European occupation. Despite this, significant rates of decline of grassland, woodland and forest bird species, as well as ground-nesting birds and ground-feeding insectivorous birds, have occurred in this bioregion.

Sightings of rainforest birds, which increased significantly across Australia, did not follow this trend in the Sydney Basin despite the presence of areas of relatively intact rainforest (Australian Terrestrial Biodiversity Assessment 2002). Sightings of the rockwarbler (Origma solitaria), a species largely restricted to the bioregion, have been reported less frequently than in the past. Loss of forest and woodland birds around Sydney, resulting from continuing urbanisation, is a threat now and into the future (Australian Terrestrial Biodiversity Assessment 2002).

Despite declines in some native species, others such as the white-headed pigeon (Columba leucomela), spotted turtle-dove (Streptopelia chinensis), long-billed corella (Cacatua tenuirostris), little corella (Cacatua sanguinea), rainbow lorikeet (Trichoglossus haematodus) and noisy miner (Manorina melanocephala) as well as the introduced red-whiskered bulbul (Pycnonotus jocosus) and common myna (Acridotheres tristis) seem to have increased in numbers in the bioregion (Australian Terrestrial Biodiversity Assessment 2002). This is probably a result of their ability to adapt well to environments modified by humans.

Two threatened species listed in the NSW TSC Act, the ground parrot (Pezoporus wallicus) and the eastern bristlebird (Dasyornis brachypterus), have both been recorded southwest of Wollongong and near Jervis Bay in the bioregion's south, while the largest population of the endangered regent honeyeater (Xanthomyza phrygia) has been recorded in the north of the bioregion around the Capertee Valley. Forest and woodland birds of the bioregion are thought to be somewhat protected in Hawkesbury sandstone communities contained in conservation reserves (Australian Terrestrial Biodiversity Assessment 2002).

General threats to species in the bioregion include broad-scale vegetation clearing and loss of remnants as well as grazing by stock. Urbanisation is also a major threat to many species in the built-up areas in the bioregion.

Significant wetlands

Nine wetlands in the Sydney Basin Bioregion are regarded as being bioregionally significant (Australian Terrestrial Biodiversity Assessment 2002).

Swan Lake provides important breeding habitat for prawns and fish and is a key feeding and roosting area for waterfowl. The lake also supports an extensive area of seagrass (Halophila ovalis and H. decipiens) (Australian Terrestrial Biodiversity Assessment 2002).

Lake Conjola provides nesting habitat for a number of threatened shorebirds. These include the endangered little tern (Sterna albifrons) and hooded plover (Thinornis rubricollis) as well as the vulnerable pied oystercatcher (Haematopus longirostris). The lake also supports a significant area of seagrass (Zosteraceae and Halophila) (Australian Terrestrial Biodiversity Assessment 2002).

Lake Liddell supported over 2,000 waterbirds in 1985 and over 3,000 waterbirds in 1995 (Australian Terrestrial Biodiversity Assessment 2002). The most abundant species in 1985 were Eurasian coot and black swan (Cygnus atratus). In 1995, the most abundant species were Eurasian coot (Fulica atra), little black cormorant (Phalacrocorax sulcirostris), great cormorant (Phalacrocorax carbo) and little pied cormorant (Phalacrocorax melanoleucos). The vulnerable freckled duck (Stictonetta naevosa) (NSW NPWS 2001) and the endangered green and golden bell frog (Litoria aurea) have both been recorded at the lake.

North Avoca Swamp has also been described as bioregionally significant as it provides key habitat for the endangered green and golden bell frog (Australian Terrestrial Biodiversity Assessment 2002).

Narrabeen Lagoon and Deep Creek support the vulnerable black bittern (Ixobrychus flavicollis), Australasian bittern (Botaurus poiciloptilus), osprey (Pandion haliaetus) and glossy black cockatoo (Calyptorhynchus lathami) (Australian Terrestrial Biodiversity Assessment 2002).

Bakers Lagoon supports a range of important species including the vulnerable freckled duck, Australasian bittern (Botaurus poiciloptilus), black-tailed godwit (Limosa limosa) and black bittern (Ixobrychus flavicollis). There have also been sightings of a star finch (Neochmia ruficauda) at the Lagoon, a species that is classified as extinct under the TSC Act, as well as the endangered black-necked stork (Ephippiorhynchus asiaticus).

The wetlands of the Cecil Hoskins Nature Reserve are considered to be bioregionally significant. They are described as being in fair condition, although feral animals, exotic weeds, changed hydrology, and pollution due to runoff from agricultural lands threaten their status.

Brundee Swamp provides key habitat for the vulnerable Australasian bittern.

Disturbances and threats to the wetlands in the Sydney Basin Bioregion are many and varied depending on their location and include impacts from urban, agricultural and industrial development.

Decreased water quality in the wetlands results from runoff from urban areas, industrial areas, agricultural lands and rubbish tips, as well as increased stormwater and pollution from sewage treatment works. Potential spills from shipping and industries can also pose a serious risk to wetland health.

The bioregion is densely populated and pressures from recreational activities, including horse riding, jetskis and boats, fishing, erosion caused by the wash from speedboats, erosion from walking and access tracks, can threaten the biodiversity of the wetlands.

Other threats include feral animals and exotic weeds, changed fire regimes, sedimentation, salinity, weir construction and mining activities.

Documents to download


Next page: Sydney Basin - regional history
Previous page: Sydney Basin - landform
Up to contents page: Sydney Basin Bioregion
Page last updated: 18 April 2016