Some findings of the survey
Some of the findings of the survey are summarised below:
The full survey findings were compiled as a three-volume set of reports. These reports were published under the title Urban bushland biodiversity survey and are available at many libraries. The reports are:
Overview and Recommendations Report - describes the social, biophysical and planning context
Flora Technical Report - describes the findings relating to native plants and communities and includes appendices with summary reports for each local government area
Fauna Technical Report - describes the findings relating to native mammals, birds, aquatic macroinvertebrates, reptiles and frogs.
The fieldwork and subsequent conclusions drawn from the data revealed that the plant communities of the Cumberland Plain are extremely diverse. An area of approximately 245,120 hectares was studied during the survey and a total of 46 different plant communities were identified. Of the plant communities, over 70 per cent are endemic to the region and are limited to a few sites.
The diversity in habitats and plant communities has in turn resulted in a great number of different species being present in the region. Over 1300 species of native plants were recorded in the study area, including 54 species which are considered to be threatened at national or state level. In addition, about 950 species are classified as regionally vulnerable. In other words, these species are not protected in conservation reserves in the western Sydney region.
The presence of such a large number of threatened native plant species suggests that the original levels of plant diversity before European settlement had been extremely high. That so many different species have actually survived to the present day is in itself remarkable, given the long history of European settlement resulted in extensive land clearing throughout the region. Many of the vegetation communities are a fraction of their original size and some major communities have been reduced to less than 10 per cent of their original range.
Some of the best-represented families in the 1995-96 Western Sydney Urban Bushland Survey included the orchids, eucalypts, acacias, and peas and grasses. One species endemic to western Sydney, Hypsela sessiliflora, was not recorded at any site during the survey and it is now believed to be extinct. The large number of plant species that are endemic to the Cumberland Plain indicate that the area developed in relative isolation due to the surrounding plateaus.
Several plant species never before recorded in Sydney were discovered during the survey, such as Callistemon shiressii, a shrub with cream flowers. Persoonia nutans, which is listed as endangered under the Threatened Species Conservation Act, was recorded at 10 different sites.
It is important to conserve what remains of the plant species of western Sydney. Although some species may not be classified as threatened in NSW as a whole, their loss from the western Sydney region affects the biodiversity of the area. The loss of a plant species may in turn lead to instability within the ecosystem or reduce the habitat or survival of particular animal species.
Vegetation communities found in western Sydney
The plant communities of the Cumberland Plain are dominated by eucalypts. The 1995-96 Western Sydney Urban Bushland Survey found:
- Tall open forests occur in areas where there is higher rainfall and more fertile soils, while the dominant vegetation, the woodlands, are in drier areas.
- Scrub and heath occur in more infertile and exposed areas at Annangrove, Maroota and Kellyville.
- Freshwater wetlands and estuarine habitats occur along the floodplains of the Hawkesbury-Nepean rivers and on the Georges and Parramatta rivers.
- Pockets of rainforest co-exist with schlerophyll forest at Kurrajong, Cobbity and Cattai.
The range of community types reflects the variation in geology, soils and drainage of particular sites. Transitional areas where there are changes in soil or geological landscapes, for example where Wianamatta shale meets Sydney sandstone, are particularly rich in the variety of plant species.
Plant community profile: the Cumberland Plain woodlands
These woodlands occur on the Cumberland Plain, stretching south to Campbelltown and Camden, north to Glossodia and Ebenezer, east to Parramatta and west to the Nepean-Hawkesbury rivers. This is the driest part of Sydney with average annual rainfall of less than 800 millimetres.
These woodlands of grey box and grey box-ironbark communities are dominated by the grey box (Eucalyptus moluccana) and forest red gum (E. tereticornis). There is spotted gum (Corymbia maculata) forest limited to small pockets at Hoxton Park, Prospect Reservoir, Fairfield and Appin-Werombi district.
Approximately 93 per cent of the original area covered by Cumberland Plain woodland in western Sydney has been cleared. With only seven per cent of the original Cumberland Plain woodlands remaining, it is vital that we conserve what remains of this vegetation type in remnant communities.
Mammals found in Western Sydney
During the 1995-96 Western Sydney Urban Bushland Survey, 17 native and 10 introduced species of mammals were recorded. It is known, however, that at least 62 native and 18 introduced species of mammals have been recorded in western Sydney since European settlement.
The survey revealed that relatively few native mammal species survive in the western Sydney region. The decline in mammal species is probably due to extensive degrading of the environment over many years. Other regions such as inland NSW which have been similarly degraded also show high rates of loss among mammal species. Prior to clearing and the presence of introduced mammals that compete with native animals for food and shelter, the western Sydney region would have supported approximately 60 species of native mammals.
In some small areas of remnant vegetation, only introduced mammals such as rabbits, foxes and feral cats were detected. Small to medium ground-dwelling native mammals, such as the brown antechinus and the New Holland mouse, were only detected in large, relatively undisturbed, rugged areas of bush. This information indicates that smaller ground-dwelling mammals have been effectively driven out of smaller more accessible habitats either by clearing of habitat areas or by introduced species competing for habitat and food or by introduced predators. Larger ground-dwelling mammals, such as the eastern grey kangaroo and swamp wallaby, were recorded respectively in 10 and nine of the local government areas.
Field workers on the survey had more success locating tree-dwelling mammals, such as possums and gliders, with a greater number of species being located at a greater number of sites. However, large-scale clearing of their habitat, and hence their habitat trees, have lessened the survival chances of many tree-dwelling species in semi-urban areas.
Birds found in Western Sydney
Since European settlement in western Sydney, at least 336 species of birds have been recorded in the region. Of these, 60 species have only been seen on a few occasions and may be assumed to have accidentally entered the area; the remainder are permanent inhabitants or regular visitors.
The most frequently encountered birds in the 1995-96 Western Sydney Urban Bushland Survey were the spotted pardalote, grey butcherbird, Australian raven, golden whistler, grey fantail, Australian magpie, grey shrike-thrush, noisy miner, silvereye, magpie-lark, superb fairy-wren and the eastern rosella. These birds were detected in 75 per cent or more of the survey areas.
At least 38 species of native birds have either disappeared from western Sydney or their numbers have been greatly reduced since European settlement in the region. Most of these birds were typically inhabitants of the Cumberland Plain woodlands, such as at Nurragingy Reserve in Blacktown. The decline of these species may be accounted for by the large-scale clearing of their woodland habitat.
Four endangered and 24 vulnerable species have been known to inhabit western Sydney in the last 50 years. However of these, four (little tern, black-necked stork, comb-crested jacana and magpie goose) are now extinct in the area and another seven (including the brolga, osprey and blue-billed duck) are occasional visitors.
Sixteen of the threatened species are waterbirds. Five threatened species — bush stone-curlew, glossy black cockatoo, powerful owl, sooty owl and masked owl — were detected by the survey. The decline of these species may be attributed to their habitat being fragmented, a decline in their food sources and being preyed on by introduced species.
Frogs found in Western Sydney
Amphibians are a major part of the biodiversity of western Sydney. Because some species have managed to survive even in populated or highly developed areas, many people encounter frogs in their neighbourhoods.
The 1995-96 Western Sydney Urban Bushland Survey found 31 native species of frogs. Of these, five were listed as threatened or vulnerable in the Threatened Species Conservation Act 1995 — green and golden bell frog, red-crowned toadlet, giant burrowing frog, green-thighed frog and stuttering frog.
The presence of threatened frog species in western Sydney highlights the importance of the region for conservation at a statewide level. Although much of the biodiversity of western Sydney remains in isolated pockets of remnant vegetation, what remains sustains a number of threatened species that are crucial to the biodiversity of NSW.
Reptiles found in Western Sydney
The reptile population of western Sydney has undergone extensive change since European settlement. According to the 1995-96 Western Sydney Urban Bushland Survey, many species have declined in numbers while others exist in greater numbers and are frequently encountered. What remains of western Sydney's reptile population hints at the previously rich biodiversity before land clearing and the impact of human activity. A number of the species that remain have adapted to the artificial habitats that have evolved in much of western Sydney.
Large species, such as goannas and some snakes, which require large home ranges of up to several hectares, cannot survive in small isolated patches of bushland. These larger species of reptile also tend to have naturally lower numbers of individuals and are therefore even more prone to have declining numbers where there is not suitable habitat.
At least 53 species of native reptiles are known in western Sydney from the survey. The red-bellied black snake and the eastern brown snake were the most frequently encountered snakes during the survey. Two of the species, the broad-headed snake and the heath monitor, are listed as threatened species in the Threatened Species Conservation Act 1995.
Aquatic macroinvertebrates found in western Sydney
Aquatic macroinvertebrates include insects (beetles, moths, dragonflies), aquatic earthworms, freshwater mussels, snails and limpets, and prawns and crayfish. The 1995-96 Western Sydney Urban Bushland Survey used a combination of all available sources of data to compile a list of 446 species in the western Sydney region. These numbers indicate that the region is rich in macroinvertebrate biodiversity.
Aquatic macroinvertebrates rely on local streams and river systems for their survival. Of the streams on the Cumberland Plain and surrounding region, very few remain in their orginal natural condition. The few that are in their natural condition are vital for conservation. The Hawkesbury-Nepean River, which is a major river system in western Sydney, is important for the conservation of aquatic macroinvertebrates as it supports some unique dragonflies and many mussel species.
Habitat profile: Blaxland Creek
Blaxland Creek, on Department of Defence land near Penrith, is probably the last near-pristine freshwater stream in the Cumberland Plain. Conservation efforts will be vital in ensuring that freshwater streams with their specialised aquatic species are protected. Blaxland Creek, because it has been relatively untouched by development, can be used not only as a touchstone for understanding the biodiversity of other freshwater streams on the Cumberland Plain but as a way of reintroducing native species to other streams.
The threats to the biodiversity of western Sydney are the same threats that face native plants and animals across NSW and Australia:
Unless these threats are addressed and reduced, western Sydney will see a greater loss of biodiversity and its native plant and animal species will disappear.
Of particular concern in western Sydney is clearing of habitat areas for houses and industry, which in turn place pressure on the remaining areas of bushland.
More information
Tables of results
References
Page last updated: 20 March 2014
