2.2 Geology and Geomorphology

2.3 The Vegetation Communities of the Upper Parramatta River Catchment

2.4 Conservation Status Of Plant Communities

2.5 Threatened Species And Populations (Flora)

2.7 Threatened Fauna Species And Populations

2.10 Threatening Processes Affecting Remnant Bushland

Part 2: Ecology of the Catchment

1. Introduction

Part 2 of the Green Corridors Management Strategy provides an overview of the ecology of the Upper Parramatta River Catchment. It includes a brief description of the plant communities, threatened species and their conservation status and the threatening processes that occur in the corridors.

The Upper Parramatta River Catchment is an extensively urbanised part of Sydney with on-going growth in medium-density housing and a section of rapidly developing conventional housing in the far north. There are also substantial areas of industrial and commercial land use and an area of extractive industry at Prospect. There are numerous areas of open space but many of these are used for intensive recreation and were either cleared earlier on for grazing or farming or have been cleared more recently for the construction of sporting facilities, particularly play fields.

There are no large or perpetually reserved conservation areas such as National Parks or Nature Reserves in the Catchment. The vast majority of the area’s remnant vegetation is within open space reserves managed by Local Government with some important areas of bushland in private and state ownership e.g. the Boral woodlands at Prospect and Cumberland State Forest in West Pennant Hills respectively. This means that Local Government has a weighty responsibility for managing the bulk of the remnant vegetation of the region. This responsibility is especially onerous because much of the remnant bushland supports vegetation communities which are now endangered due to extensive clearing.

Most of these remnants pose substantial management challenges because of a long history of degradation, on-going pressures of settlement and the fact that many of these areas were not designed to function as viable conservation reserves. Reserves have often survived only because they were the "left-overs" of the property development process. Only more recently have areas in the Catchment been deliberately set aside or managed as open space with some consideration of conservation issues. However existing patterns of land use and land valuation have meant that reserves are still largely restricted to areas which are not of prime development potential or which are remnants from past agricultural activities.

Only with substantial commitment of professional and volunteer resources can land managers hope to reverse the trend of bushland loss and degradation. An important aspect of this process is understanding the ecological attributes of remnant bushland and the factors that have shaped and continue to affect its condition. Such an understanding forms the basis for formulating, resourcing and implementing the management plans and policies which are essential to ensuring that bushland remnants are not allowed to be terminally compromised by consent, neglect or mismanagement. A major management issue for many of these often small, linear and isolated remnants is the need to ensure their viability through maximising their size and re-establishing ecological connections with habitat corridors.

Whilst the area contains relatively little remnant bushland compared to some of the less settled parts of Sydney, these remnants are often especially important because they represent some of the last examples of particular vegetation types, habitats and corridors for threatened plants and animals, and important cultural resources. Even remnants along road verges and railways can be of considerable significance in extensively cleared areas such as the Upper Parramatta River Catchment. Whilst rarely large and often degraded to some extent, the remnants of this area include ecological communities and species which are not adequately conserved in the large ring of sandstone-based National Parks that surround Sydney.

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2. Geology and Geomorphology
1. Geology

The Upper Parramatta River Catchment encompasses two major geological provenances; the Cumberland Plain and the Hornsby Plateau.

The Cumberland Plain is a basin-like feature which occurs to the west of the Hawkesbury River from Penrith, north to Glossodia, south to Wilton and east to Parramatta. It is largely composed of Wianamatta Group Shales (mainly the Bringelly Shale member) with rare outcroppings of associated sandstone. Soils derived from the shales are deep clays of moderate to low fertility. The Blacktown Soil Landscape is the most common soil type.

The Hornsby Plateau is an uplifted area north of the Harbour, east of Cattai Creek, Castle Hill and Parramatta. It is dominated by the dissected terrain which cuts through Hawkesbury Sandstone but retains areas of Wianamatta Shale (Ashfield member) as caps along some ridge-tops e.g. West Pennant Hills. Some ridges retain highly weathered remnants of shale in the form of laterite as well as elements of the transitional unit known as the Mittagong Formation or the Shale/Sandstone Transition Zone (see Douglas, unpub. 1995). The north-eastern third of the catchment occurs on the south-western edge of the Hornsby Plateau. The soils are diverse and range from the typical Hawkesbury Soil Landscape to the transitional Lucas Heights Soil Landscape which is derived from Hawkesbury and Wianamatta Shales.

The boundary between the Plateau and Plain is poorly defined in the catchment. An analysis of soil landscapes, topography and vegetation types indicates that the boundary between the Cumberland Plain and Hornsby Plateau is such that the Plateau occurs north of the Parramatta River, east of Windsor Road then east of Old Northern Road to Castle Hill (Map X). The transition zone is between Old Northern / Windsor Roads in the east and Old Windsor Road in the west.

2. Geomorphology

As the Catchment is composed of two quite different geological provenances, it is to be expected that its geomorphology will also be quite contrasting. This certainly the case, with the Darling Mills Creek system being typical of the deeply dissected sandstone terrain of the Hornsby Plateau. This catchment is dominated by v-shaped valleys and sandstone scarps and benches, with relatively small deposits of alluvium at stream confluences. In contrast, the western streams such as Greystanes Creek, drain from and through the flat to gently undulating shale-based terrain of the Cumberland Plain. There is a marked absence of the rocky slopes and benches which typify the more eastern parts of the catchment within the Hornsby Plateau. More extensive deposits of Quaternary alluvium are found along the Cumberland Plain streams, mainly as the South Creek soil landscape (Bannerman & Hazelton 1989). Backswamps and cut-off meanders are occasionally present.

Intermediate between the characteristics of the Darling Mills and Greystanes Creeks is the eastern Toongabbie Creek system where shale terrain dominates but sandstone outcrops occur in gullies and along many streambeds.

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1. The Vegetation Communities of the Upper Parramatta River Catchment

This section provides a brief description of the vegetation communities occurring in the catchment. The distribution of the vegetation communities was mapped at a scale of 1:10,000 from an aerial photograph taken in November 1997. The maps ‘Vegetation Communities and Management Zones’ are attached in Part 6 of this Strategy. More detailed information about plant species is attached in the Appendix. It contains extracts from the UBBS (NPWS 1997) describing in more detail each of the vegetation communities and associated species and sites of significance in the catchment.

The most recent literature regarding the native vegetation communities of the catchment is the Urban Bushland Biodiversity Survey (UBBS) of Western Sydney (NPWS, 1997). The Urban Bushland Biodiversity Survey dealt with Local Government Areas rather than water catchments or catchment management areas. Table 1 lists the vegetation communities identified within the catchment by the UBBS. These have been placed into a sub-catchment context for this report. More detailed descriptions of the communities are given in the exerts from the UBBS in the Appendix.

 

1. Blue Gum High Forest

Blue Gum High Forest is found only in the upper Darling Mills Creek Catchment. Most of this occurs from the catchment boundary at Castle Hill Road, down-slope and south to just below Aiken Road in West Pennant Hills. A small area also remains in a drainage line near the intersection of Crane and Darcey Roads in Castle Hill and some other patches in Carlingford such as the rear of North Rocks Park. It is essentially restricted to the higher altitude and relatively high rainfall shale-capped ridges and which form the northern catchment boundaries or which run off it e.g. eastern North Rock Road.

There are a number of remnants of this community in the West Pennant Hills area, the largest being Cumberland State Forest and the adjoining IBM land. All of the bushland and remnant vegetation in this area is or was once Blue Gum High Forest.

Most remnants are now restricted to gullies and have moderate to severe weed infestation and erosion problems. On-going urbanisation, especially near Castle Hill Road, is leading to further losses of this community and degradation of remnants through sedimentation, fragmentation and weed invasion. Most of the landscaping in this area is not of native origin and represents a substantial invasive threat to remnants as well as favouring non-native or aggressive native fauna. Blue Gum High Forest is listed as an endangered ecological community under Schedule 1 of the Threatened Species and Conservation Act 1995.

 

2. Blue Gum River-flat Forest

Blue Gum River-flat Forest appears to have once extended down to the Parramatta River and to have occurred along the river banks and nearby floodplain downstream of James Ruse Drive. This endangered community is now only seen along lower Toongabbie Creek downstream of Old Windsor Road and near its confluence with the Quarry Branch Creek in Northmead.

This community merges with Sydney Sandstone Gully Forest where the development of shale-influenced alluvium is restricted or reduced e.g. in narrow, more sandstone-based gullies or near sandstone outcrops along streams. A small patch occurs at the lower reaches of Darling Mills Creek west of Lake Parramatta in Northmead. It merges with Red Gum - Cabbage Gum River-flat Forest where drainage is impeded by a high influence of clay soils, where exposure to drying winds is increased and where water supply along the stream is less reliable e.g. small tributaries and more westerly parts of Toongabbie Creek. The Sydney Blue Gum (Eucalyptus saligna) population in the lower Toongabbie Creek catchment is important as it is the southern limit of this tree; all populations to the south are hybrids with E. botryoides (Bangalay). As there is usually genetic variation in a species across the extent of its range, conservation of species at the limits of their distribution is important for maintaining genetic diversity.

 

3. Cumberland Plain Woodland

This is a suite of communities occurring on the Cumberland Plain in the south western part of the catchment. Within this report, three types of Cumberland Plain Woodland are dealt with; Grey Box Woodland, Grey Box - Ironbark Woodland and River-flat Forest. Grey Box - Ironbark Woodlands tend to occur along the fringes of the Cumberland Plain e.g. Luddenham Soil Landscape. Grey Box Woodland is generally restricted to the central Plain growing on the Blacktown Soil Landscape derived primarily from the Bringelly Shale member of the Wianamatta Group. Most of the creek corridors in the Blacktown LGA are on the Cumberland Plain but have been extensively cleared of their original vegetation. Today, only remnant trees survive as well as a few sites of Swamp Oak forest at Duncan Park and Greystanes Creek. The most intact remnants of Cumberland Plain occur on private land at Norman Street, the Boral Quarry, and at the Research Poultry Station in Seven Hills. Cumberland Plain Woodland is listed as an endangered ecological community under Schedule 12 of the Threatened Species and Conservation Act 1995.

 

4. Grey Box Woodland

Grey Box Woodland is found largely west of Toongabbie however its similarity to Grey Box-Ironbark Woodland and the highly altered state of the few remnants means that considerable overlap and intermingling of these communities occurred in the central part of the Catchment. It is likely that a number of the Grey Box remnants in the area were Grey Box - Ironbark communities but that the ironbarks have been either removed or severely depleted through their use in rural fencing and more recently for log round "stepping stones" and garden edges.

 

5. Grey Box - Ironbark Woodland

Grey Box - Ironbark Woodland occurs from Crestwood Reserve in the far north of the Catchment through to parts of eastern Blacktown LGA and the far western parts of Parramatta LGA. Most remnants are in the form of mown parkland rather than bushland, with many having been subject to various alterations such as landscape plantings of non-indigenous species.

Both communities merge with River-flat Forests along watercourses. This is often indicated by an increase in the dominance of Forest Red Gum (Eucalyptus tereticornis) and the appearance of Cabbage Gum (E. amplifolia) and Melaleuca species.

 

6. River-flat Forest

River-flat Forest includes two sub-units Red Gum - Cabbage Gum River-flat Forest and Swamp Oak Forest which occurs a thin band along the banks of creeks. Red Gum - Cabbage Gum River-flat Forest is essentially the form of Cumberland Plain Woodland which occurs along creeks and floodplains on alluvium soil. It used to be relatively widespread on floodplains but because of the highly fertile soils and arable nature of these landscapes, it is now restricted to tiny riparian strips. What remains is severely degraded from past grazing practices and subsequent weed invasion. Small patches of River-flat Forest which are too small to map are present along most creek corridors mostly as mature remnant trees typical of the Cumberland Plain vegetation. The only substantial remnant mapped is a discontinuous riparian and floodplain fringe along Greystanes Creek and Swamp Oak Forest at Duncan Park. Other small and less distinct remnants are present around Wentworthville and Westmead along tributaries of Toongabbie Creek. Along Toongabbie Creek the community merges with Blue Gum River-flat Forest. The distinguishing feature of the latter is the dominance of Sydney Blue Gum (Eucalyptus saligna).

 

7. Sydney Sandstone Complex

This suite contains numerous sub-units varying with and depending on the resolution used in mapping and the methods used in describing this very diverse and variable vegetation type. This report has adopted sub-units used in the UBBS and combined these with communities defined by some other studies (e.g. Mount King Ecological Surveys 1994) rather than using the simple division into Ridgetop Woodland and Gully Forest units.

The Sydney Sandstone Complex is the dominant remnant vegetation type of the Darling Mills and Hunts Creek Corridors. It forms the bulk of the largest remnant in the Upper Parramatta River Catchment, namely the Excelsior/Bidjigal Reserve and Darling Mills State Forest area.

Angophora bakeri, Eucalyptus sclerophylla Woodland;

This assemblage was recorded on exposed upper slopes at and near the Bundilla Scout Camp, at the confluence of Toongabbie Creek and The Quarry Branch Creek. It is closely related to the vegetation which occurs below the shale/sandstone transition along parts of Cattai Creek outside the study area from Castle Hill to Cattai e.g. Fred Caterson Reserve. It is also closely allied with some of the Western Shale/Sandstone Transition Woodland vegetation.

Angophora costata, Syncarpia glomulifera, Allocasuarina torulosa Open-forest / Woodland;

This assemblage is present on the ridgetops, but more often on the upper slopes in the Darling Mills and Hunts Creek Catchments, but is prevalent around Lake Parramatta. It appears to occur mainly on the Gymea soil landscape and is often associated with the ecotone between the shale-based Turpentine-Ironbark Forest and the sandstone flora. As most ridge-tops have been cleared and settled, this community is often found on the upper slopes at the edge of bushland adjoining housing. It can extend a considerable distance down the less sheltered slopes.

Corymbia gumnifera, Angophora bakeri, Eucalyptus piperita, E. haemastoma Woodland;

This assemblage is relatively restricted in its distribution as it is associated with the flatter ridgetops and upper slopes, many of which have been cleared for housing or playing fields. An excellent example can be seen upslope of the fire trail which runs west and north from the end of Range Road through Darling Mills State Forest, in the far south of West Pennant Hills. It appears to be largely restricted to the northern ridges of the Darling Mills Creek Catchment.

Allocasuarina littoralis, Kunzea ambigua, Banksia ericifolia Scrub / Heath;

The Scrub / Heath unit occurs mainly on the site known as Bald Hill near the end of Highs Road in West Pennant Hills, overlooking Darling Mills Creek. This is its only large occurrence in the Upper Parramatta River Catchment. It represents potential habitat for the threatened species Darwinia biflora, Tetratheca glandulosa and possibly the Red-Crowned Toadlet. Patches of this vegetation type also occur sporadically in areas of shallow and/or poorly drained soil on laterised ridgetops amongst various other ridgetop woodland units. A scrub dominated by Kunzea ambigua (Tickbush) tends to develop in areas of past disturbance and/or an absence of hot fires in the last 15 years or more, e.g. the fire/powerline trail around Virginia Place in Darling Mills State Forest.

Eucalyptus pilularis, E. saligna, Syncarpia glomulifera, Angophora costata Gully Forest;

This unit is abundant on lower slopes and in gullies but can extend a long way up the slopes on the more sheltered aspects where it sometimes merges into Turpentine-Ironbark Forest along a short shale/sandstone interface. For example, E. pilularis extends from the gully all the way to the upper slope where it adjoins housing in the lower West Pennant Hills area. It is prevalent in the Darling Mills and Hunts Creek Catchments and could be argued to occur as a narrow strip along some of the upper Toongabbie Creek system in Baulkham Hills where Turpentine-Ironbark Forest merges with sandstone flora.

Closed Forest / Scrub.

Closed Forest / Scrub is generally restricted to the riparian zones of the larger streams and is often sheltered by the Gully Forest canopy. It can extend up some minor tributaries as a very narrow band on the more sheltered and/or fertile slopes. It occurs in strips and linear patches along Darling Mills and Hunts Creeks and is also occasionally seen along parts of eastern Toongabbie Creek. It is generally a feature of sandstone-based terrain but occurs along some parts of the Cumberland Plain streams, mainly along the banks where sandstone outcrops have been uncovered by erosion, e.g. Briens Road bridge at Westmead. It has often been heavily disturbed by the installation of sewerage, urban flooding and weed invasion.

 

8. Turpentine-Ironbark Forest

There is very little of this community remaining in the catchment and of what remains, most are not representative of the full development of this community. Most of the remnants, which comply with the definition of this ecological community, are more representative of the transition between "true" Turpentine-Ironbark Forest and the adjoining sandstone-based vegetation. For example, "true" Turpentine-Ironbark Forest supports very few if any Angophora costata (Smooth-barked Apple) yet many of the remnants of this community in the Darling Mills Catchment have a relatively high proportion of this species; a situation which indicates the ecotone between the shale and sandstone vegetation (Benson & Howell, 1990). Turpentine - Ironbark Forest has a preliminary determination as an endangered ecological community under Schedule 1 of the Threatened Species and Conservation Act 1995

This community is now restricted to very few sites, all of which are small and isolated. It once occurred on the eastern Cumberland Plain and drier shale-capped ridge of the Hornsby Plateau but within the catchment there are no true Cumberland Plain-based remnants and less than a hand-full of ridge-top sites. It was once found extensively around Castle Hill and Baulkham Hills on the drier Ashfield Shales which were too dry to support Blue Gum High Forest but not dry or westerly enough to support Cumberland Plain Woodland. Most remnants in this area are thin strips which merge with Cumberland Plain Woodland on the remnant edges and towards Windsor Road; or with Shale/Sandstone transition communities in the slopes of the gullies. Within the Catchment, it is now found in the Darling Mills, and the upper, eastern Toongabbie Creek systems and in the vicinity of Lake Parramatta. A more substantial example can be found in Coxs Park just outside the catchment boundary in Carlingford.

 

9. Shale/Sandstone Transition Forest

Shale / Sandstone Transition Complex is a suite of communities that occurs at the interface of shale based Cumberland Plain and sandstone landscapes of the Hornsby Plateau. As ecotone units, both tend to intergrade with each other and with surrounding shale and sandstone-based vegetation such as Turpentine-Ironbark Forest and Sydney Sandstone Complex respectively. They can be difficult to delineate in the field and within the catchment. Most occurrences are in very narrow bands, some of which can not be mapped due to limitations of scale and the extensive intergradation of adjoining communities. Shale / Sandstone Transition Forest is listed as an endangered ecological community under Schedule 1 of the Threatened Species and Conservation Act 1995.

Shale / Sandstone Transition Forest appears in the eastern Toongabbie Creek, lower Hunts Creek and outer edges of Lake Parramatta where Turpentine-Ironbark Forest intergrades with Sydney Sandstone Complex. Stringybark species are often prevalent e.g. Eucalyptus eugenioides and/or E. globoidea along with the Red Mahogany (E. resinifera) and rarely the White Mahogany (E. acmenoides). Further quantitative research is needed to define this community and to distinguish it from other vegetation types.

A woodland form of Shale/ Sandstone Transition Forest is readily distinguished from most of the surrounding vegetation by the dominance of Mountain Scribbly Gum (Eucalyptus sclerophylla). It occurs along upper Toongabbie Creek at Sophia Doyle Reserve, along Seven Hills Road and for a few hundred metres downstream. Other occurrences were noted by NPWS (1997) along slopes above Toongabbie Creek near its confluence with The Quarry Branch Creek, however the vegetation in this area appeared to be more allied with the Transition Forest rather than the Woodland form.

 

10. Riparian Complex

This suite encompasses all of the instream aquatic vegetation and fringing vegetation such as sedges, reeds and rushes. It includes many species typical of wetland environments. It is readily observed around some of the edges of Lake Parramatta where reedlands of Eleocharis sphacelata have developed. It is present to varying extents throughout the Upper Parramatta River Catchment. Many of the sandstone-based streams of the catchment have very little instream and fringing vegetation, possibly because of extensive disturbance and scouring by altered flood regimes. Despite similar impacts, shale and alluvium-based streams tend to retain more of this vegetation type. This may be due to the larger areas of suitable substrate in the banks and beds of shale and alluvium-based streams which offer better quality habitat, more ponding and possibly a less ephemeral stream flow.

The streams of the Cumberland Plain occasionally still support substantial areas of Riparian Complex vegetation, some of which has potential to develop into wetlands. A large number of plant species and forms can be present in the Riparian Complex.

11. Estuarine Complex

Within the study area, this refers to the linear strips and patches of mangroves along the Parramatta River. This community has suffered enormous impacts through "land reclamation", particularly for industrial land and playing fields. Other areas have been lost through landfill with various wastes. There is a relatively little area of mangroves in the study area of the Upper River.

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2. Conservation Status Of Plant Communities

The catchment contains a diverse range of endangered ecological vegetation communities and flora and fauna species. In essence, all of the vegetation types of the catchment, which occur on Wianamatta Shale or Quaternary alluvium are endangered. This includes the Cumberland Plain Woodlands and Blue Gum High Forest, which are listed as endangered communities under Schedule 1 of the Threatened Species and Conservation Act 1995. Turpentine Ironbark Forest and Shale/Sandstone Transition Forests have preliminary determinations as endangered ecological communities under Schedule 1 of the Threatened Species and Conservation Act 1995 and final determinations are most likely to be made soon. The distribution of conservation status of the vegetation communities is shown on map ‘Conservation Status’ in Part 6.

A key feature of the catchment is a substantial ecotone associated with the transition from the Hornsby Plateau to the Cumberland Plain. This ecotone is created through changes in geology, altitude and rainfall from the lower and drier, shale based eastern Sydney landscapes to the elevated Sandstone plateau of the western Sydney landscapes. This transitional landscape zone (ecotone) is indicated by the occurrence of transitional vegetation communities such as the Western Shale/Sandstone Transition Forest. They occur where the two landscape types meet at the Hornsby warp in West Pennant Hills and along Toongabbie Creek and its upper tributaries. The transition zone is inherently limited in extent and fairly linear in shape. Consequently the associated vegetation communities are of restricted range and prone to fragmentation and naturally rare. The impact of white settlement post-1788 has affected such communities so severely that they are now considered to be endangered (NPWS 1997).

The catchment’s endangered communities are limited to the Sydney region. Most remnants are severely fragmented and degraded caused by a history of logging, clearing and agriculture and residential housing development of the more fertile shale and alluvial landscapes. The relative ease of farming and construction on and access to ridge-tops of the Hornsby Plateau and the flat to gently undulating terrain of the Cumberland Plain has meant that these areas have been preferred development areas compared with the inaccessible sandstone country. They continue to be subjected to the most severe impacts of Sydney’s growth. The most current threats to remnant vegetation and habitat are freeway construction, road widening, flood mitigation work, increased densities in residential development, construction of sporting facilities, and inappropriate maintenance such as mowing and spraying of herbicides.

The widely recognised Sydney Sandstone communities are now the dominant remnant vegetation type in the Catchment. Sandstone landscapes are unsuitable for farming due to their poor, sandy, stony soil and rugged landform. These limit residential housing development, which would be affected by steep sandstone slopes, bushfire and flooding hazards. Because of their natural limitations to development, relatively large areas of sandstone terrain have been conserved in Darling Mills State and Cumberland State Forests and Excelsior Park. Another factor in their protection might be that they have long been perceived as more scenic than the flatter and/or drier areas of the ridges and Cumberland Plain.

Consequently, the retention and reservation of sandstone vegetation communities is more extensive within the catchment and as is the case in the Sydney metropolitan region. With the exception of some components of the Sydney Sandstone Complex, all of the other communities in the catchment are extant and inadequately reserved. The extent of existing remnants is far from even approaching the levels required for comprehensive, adequate and representative reservation (see NPWS, 1997). Part of the problem, as mentioned above, is the fact that some of these communities were naturally limited in extent and distribution and thus very prone to rapid depletion and degradation.

Most bushland remnants are now occurring along drainage lines because such areas have been affected by flooding and allocated as open space for drainage easements and playing fields. This has meant that remnant vegetation and habitat corridors are particularly vulnerable to the many forms of alteration and degradation associated with drainage lines such as altered flood regimes, flood mitigation work, sewage lines, stormwater pollution and related weed invasion. However, the linear configuration and branching nature of the Toongabbie and Darling Mills Creek system means that green corridors can be easily established. Most areas along creek corridors are zoned for open space or drainage easements and therefore protected from residential development. Reservation, restoration, revegetation and linking of currently fragmented indigenous vegetation communities and habitats along creek corridors in the catchment is a great opportunity to protect and enhance biodiversity.

On the Cumberland Plain, the creek corridors are the most narrow, cleared and fragmented. Although set aside in council owned and/or managed open space reserves, most remnant vegetation remains under various levels and types of threat. Inappropriate management techniques such as clearing, mowing and spraying of herbicides and increased urban runoff are the most direct barriers to natural regeneration. Lower Toongabbie Creek still contains significant remnant vegetation but most of it is degraded and under pressure due to the narrowness of the reserve and adjacent development. Clearing continues for flood mitigation, favouring weed invasion and erosion. Bush regeneration activity has been limited due to lack of funding and resources. This corridor is the most threatened. It is in need of regeneration and restoration as it contains the rarest of the endangered communities. Conservation and restoration of the Blue Gum River-flat Forest and Shale/Sandstone Transition Complex of Toongabbie and it’s upper tributaries should be a priority in the catchment.

The bushland in the Darling Mills Corridor is much more intact and under less pressure. The main management requirements here are continuing bush regeneration to control weed invasion, stormwater control and the prevention of inappropriate recreational activities such as bmx-bikes, or pedestrian /cycle paths.

Threats are documented in more detail later in this report. Please refer to the section Threats to Remnant Bushland. Even within perpetual reserves such as National Parks and Nature Reserves, threatening processes continue to operate to varying degrees. Within urban bushland, these are almost always of a greater magnitude and there is a consequent need to correspond with intensive management to counteract or otherwise reduce these threats.

 

1. Regional Significance

The UBBS provides comprehensive lists of plant species, which are of conservation significance within Western Sydney. Reference to the full UBBS report should be made to gain a full understanding of the distribution and significance of these within the catchment. Additional information provided by the UBBS includes species lists for various sites throughout the area, some including notations as to the significance of the plants recorded. Some of the information provided on a Local Government Area basis includes records of particularly important species and populations in the catchment.

For example, the population of Eucalyptus saligna (Sydney Blue Gum) in the lower Toongabbie Creek catchment is important as it is the southern limit of this tree; all populations to the south are hybrids with E. botryoides (Bangalay). Conservation of species at the limits of their distribution is important for maintaining genetic diversity as there is usually genetic variation in a taxon across the extent of its range. Such variation is important in the evolutionary process as it can provide the means by which flora and fauna can adapt to changing conditions. This is especially important in the context of highly modified environments such as the catchment and because of large-scale environmental change due to the enhanced greenhouse effect and depletion of the ozone layer. Some of these populations have considerable potential for being listed as endangered under the TSC Act.

 

2. Significant Vegetation Remnants

The major remnants of significance are Excelsior/Bidjigal Reserve, the Prospect Cumberland Plain Woodlands, Norman Street, Lake Parramatta Reserve and environs, Cumberland State Forest and the IBM forest, The Quarry Branch Creek remnants, middle Toongabbie Creek remnants e.g. Centenary Centre, and upper Toongabbie Creek remnants e.g. Sophia Doyle and William Joyce Reserves. A number of smaller and very isolated remnants are also present with some of these supporting endangered communities. All of these remnants are mapped at a scale (1:16,000) on the Map Vegetation Communities and Management Zone" attached in Part 6 of this report. A brief overview of significant vegetation communities occurring within the catchment is given in Table 2.2.

All larger significant vegetation remnants have been documented by NPWS (1997). Relevant sections from the UBBS report have been reproduced in the Appendix with some minor modifications having been made to the NPWS text.

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3. Threatened Species And Populations (Flora)

NPWS (1997) note the presence or records of several flora species of State and National Significance within the catchment. They are listed in Table 2.3 by Local Government Area; additional comments are made by the Steve Douglas based on more current research and personal communications with NPWS staff. These plants are threatened or rare at state and/or national levels. No endangered populations are known from the catchment, however populations of Persoonia hirsuta and Hibbertia incana are listed for Baulkham Hills Shire.

 

Table 2.2: Significant Vegetation Remnants

Site	LGA	Vegetation Community
Lower Toongabbie Creek	Parramatta LGA	Shale/Sandstone Transition Forest, Cumberland Plain Woodland
Central Gardens	Holroyd LGA	Cumberland Plain Woodland
Crestwood Reserve	Baulkham Hills LGA	Shale/Sandstone Transition Forest, Cumberland Plain Woodland
Cumberland State Forest	Baulkham Hills LGA	Blue Gum High Forest
Darling Mills State Forest	Baulkham Hills LGA	Sydney Sandstone Gully Forest Sydney Sandstone Ridgetop Woodland
Duncan Park	Blacktown LGA	River-flat Forest
Excelsior Reserve	Baulkham Hills LGA	Turpentine Ironbark Forest, Blue Gum High Forest Blue Gum River-flat Forest, Sydney Sandstone Gully Forest, Sydney Sandstone Ridgetop Woodland, Sydney Sandstone Heath, Shale/Sandstone Transition Forest,
Greystanes Creek Reserve	Blacktown LGA	River-flat Forest
International Park	Blacktown LGA	River-flat Forest
Lake Parramatta Reserve	Parramatta LGA	Sydney Sandstone Gully Forest Sydney Sandstone Ridgetop Woodland Shale/Sandstone Transition Forest
Parramatta Park	Parramatta LGA	Cumberland Plain Woodland River-flat Forest
Sophia Doyle Reserve	Baulkham Hills LGA	Shale/Sandstone Transition Forest Sydney Sandstone Gully Forest
Third Settlement Reserve	Parramatta LGA	Blue Gum River-flat Forest Shale/Sandstone Transition Forest
Boral Quarries	Holroyd LGA	Cumberland Plain Woodland
CSRIO site	Holroyd LGA	Cumberland Plain Woodland
Buckleys Road	Parramatta LGA	Cumberland Plain Woodland
Bundilla Scout Camp	Parramatta LGA	Blue Gum River-flat Forest
Grand United Centenary Centre	Parramatta LGA	Blue Gum River-flat Forest Shale/Sandstone Transition Forest
Grantham Poultry Station	Blacktown LGA	Cumberland Plain Woodland
Norman Street	Blacktown LGA	Cumberland Plain Woodland
Sydney Water Site	Parramatta LGA	Cumberland Plain Woodland

 

Table 2.3: Flora of State and National Level Significance

Species	Code	LGAs	Subcatchments	Comments	Local Occurrences
Acacia bynoeana	3VC-, nominated for upgrading to endangered	Baulkham Hills	Darling Mills (upper)	One record from 1947. Possibly now extinct due to housing	Near the end of Cottonwood Place in the far east of Castle Hill overlooking Darling Mills Creek
Acacia pubescens	2VCa Sch2	Holroyd	Toongabbie Creek (west)	Recovery Plan being formulated	Lower Canal
Epacris purpurascens var. purpurascens	2KC-, nominated as vulnerable	Baulkham Hills, Parramatta	Darling Mills, Hunts Creek, Toongabbie Creek (middle) Lake Parramatta	Considered worthy of listing under Schedule 2 and coding as 2VCa	Excelsior / Bidjigal and Eric Mobbs Reserve, Lake Parramatta Reserve, Moxham Reserve, West P’ Hills
Eucalyptus punctata ssp. wianamattica	_	Baulkham Hills, Parramatta	Toongabbie Creek (lower)	Considered worthy of listing under the TSC Act. Locally endemic	Quarry Branch Creek e.g. Sophia Doyle & William Joyce Reserves, North Wentworthville, Toongabbie
Hibbertia nitida	2RC-	Parramatta	Hunts Creek	Not recorded recently	Lake Parramatta Reserve
Pimelea curviflora var. curviflora	_	Parramatta	Toongabbie Creek (middle)	Nominated for addition to Schedule 1. Preliminary Determination for addition to Sched.2	Moxham Reserve
Pimelea spicata	3ECi Sch1	Blacktown?, Holroyd	Girraween Creek	Recovery Plan available	A number of records from Prospect, Greystanes and the Lower Canal
Tetratheca glandulosa	2VC- Sch2	Baulkham Hills	Darling Mills (upper)	Recommend for coding as 2VCa	Darling Mills State Forest (likely to be on Bald Hill as well)

ROTAP Code:

Code	Definition
2	species with geographic range of less than 100 km
3	species with geographic range exceeding 100 km
E	Endangered - species at serious risk of disappearing from within 1 or 2 decades
V	Vulnerable - at risk of disappearing from the wild
R	Rare - species which is rare in Australia (and hence usually in the world) but which currently does not have any identifiable habitat
Ca	1,000 or more plants are known to occur within a conservation reserve
Ci	Species is inadequately conserved

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1. Native Fauna and Habitats of the Upper Parramatta River Catchment

This study focuses on documenting fauna habitats based on the mapping of vegetation communities. The scope of this study did not include the undertaking of fauna surveys due to limited resources. However, as the UBBS points out "vegetation alone does not adequately summarise the requirements of many fauna, which vary widely because of differences in biology and ecology. The presence of tree hollows and components of ground cover such as rocks, logs or tussock grasses are just some of the elements that are important in defining an organism’s habitat" (NPWS 1997).

It is important to note that whilst the UBBS is the most recent source of information on fauna in the catchment, the fauna component of the Survey was by no means as extensive as the flora component. Indeed there are some classes of fauna such as frogs and bats, which were not surveyed at all due to limitations of funding and inappropriate season for these type of surveys. As a consequence, greater emphasis was placed on assessing fauna habitats and existing data to determine which species may still occur in the area.

The UBBS identifies eight types of fauna habitat. These habitat types are associated with the local vegetation communities and land uses found in the catchment as shown below. (Habitat types have been arranged in descending order of their estimated extend in the Catchment.)

1. Urban (U) - residential, commercial, industrial and most associated special use zonings;
1. Dry Sclerophyll Forest (DSF) - Sydney Sandstone Ridgetop Woodland Complex (Forest subunits), Western Shale/Sandstone Transition Forest, Turpentine-Ironbark Forest;
2. Woodland (Wo) - Grey Box and Grey Box-Ironbark Woodlands, Sydney Sandstone Ridgetop Woodland Complex (Woodland subunits), Western Shale/Sandstone Transition Woodland;
3. Farmland (F) - parkland, golf courses, farms, vacant former farms, paddocks;
4. Wet Sclerophyll Forest (WSF) - Blue Gum High Forest, Blue Gum River-flat Forest,
   Blue Gum / Blackbutt Subunit of Sydney Sandstone Gully Forest Complex, Red Gum - Cabbage Gum River-flat Forest;
5. Scrubland & Heath (H) - Sydney Sandstone Ridgetop Woodland (Scrub/Heath subunit);
6. Rock Outcrops (RO) - mainly present in sandstone terrain on mid-slopes and ridges.
7. Rainforest (Rf) - Sydney Sandstone Gully Forest Complex (Closed Forest/Scrub subunit);
8. Wetlands - (Wt) Riparian Complex

There is substantial overlap between some habitat types because of the variation within and merging between some communities, particularly sandstone-based woodlands and forests.

The UBBS describes the types of fauna found in each of these habitats. Specialist texts should also be referred to for an understanding of the habitat requirements of various species. The UBBS does provide detailed and localised information on the occurrence of threatened species and their habitat requirements. As this report focuses on identifying general fauna habitats and the known and potential occurrences of threatened species, extensive reference has been made to the UBBS species profiles. These are addressed further on.

The threatening processes to remnant bushland and habitat in the catchment are described in detail in section 2.11 of this report. For further reference, the UBBS contains a good review of threats to biodiversity in the Western Sydney Region (see pp. 31-36 in Native Fauna of Western Sydney. NPWS, 1997). The UBBS also contains a section, which deals with specific and detailed descriptions of the threats to various types of fauna some of which are mentioned in later sections below. In general all the threats to the survival of native fauna are related to five general processes which threaten species to varying degrees across the catchment and indeed the whole of Australia. These are:

• habitat loss, fragmentation and degradation;
• introduced species;
• altered fire regimes;
• pollution (various types); and
• climate change

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   Threatened Fauna Species And Populations

The tables below provide a list of threatened fauna species likely to occur in the catchment. It is derived from the UBBS list of threatened species including those which are not listed under the TSC Act but have the potential to be listed for various reasons. Species which have not been recorded in the catchment, but for which suitable habitat is known or likely to exist have been included. Note that this report does not include invertebrate fauna. Habitat types in which the species have been recorded are specific to those found in the catchment. References are NPWS (1997), Strahan (1995), Ehmann (1997), Land & Environment Planning (1994), Lindsey (undated), Tyler (undated). The distribution of known rare species is shown on the map Rare Species Records in Part 6 of this document.

 

1. Bird Habitat

The UBBS also listed forty-seven species of bird as regionally significant. These are not dealt with separately here as there are clear patterns which underlie the vulnerability of these birds, making the issue more readily dealt with in terms of habitat management. Not surprisingly, it is the birds which are characteristic of the Cumberland Plain that are now regionally vulnerable. This is largely due to loss and on on-going degradation of habitat (e.g. from clearing and grazing) along with predation by exotic species. In addition, some of the species, which occur in the sandstone terrain are also threatened by the same factors, particularly the loss of vegetation types such as Blue Gum High Forest which are naturally restricted to the heavily settled ridge-tops.

One particularly notable record of regional significance is that of the Barking Owl from Castle Hill in 1983. The reliability of this record is unknown however, the species has been recorded by the author 6 km to the north. Barking Owl is considered to be worthy of listing under the TSC Act and is probably of greater conservation significance in the Sydney Region than the Powerful Owl (P. Burcher pers. comm. 1997).

Again, the UBBS describes the various threats to bird diversity and many of these are clearly linked to more general threats to biodiversity. The threatening processes specifically affecting birds were broadly grouped by NPWS (1997) as:

• habitat loss and fragmentation;
• habitat degradation;
• pesticide use;
• direct exploitation (e.g. capture for sale); and
• predation.

The UBBS notes that because of the fragmented and degraded nature of much of Western Sydney and the ecology of many birds, it is "important to plan and manage faunal habitats on a regional scale and not focus on reserving many small, isolated remnants. It is necessary to maintain or re-establish links between remnants" (NPWS, 1997). This is a central goal of this Green Corridor Management Strategy and the preceding Green Web-Sydney project (Seidlich & Douglas 1997).

1. Mammal Habitat

"The mammalian fauna of Western Sydney, particularly on the Cumberland Plain is noticeably depauperate" (Antcliff, 1988 cited in NPWS, 1997). The only threatened mammals likely to be present in the catchment are three microchiropteran bat species. NPWS (1997) discussed the pre-European mammal fauna of the area as well as some of the threatened species, which survived until relatively recently.

Even though the list of threatened species occurring in the catchment is quite short (refer to Table 2.4), indicating unsuitable or difficult conditions and habitat for those species, it is important to note that many, more common native mammals survive in the urban catchment. They are generally larger and versatile arboreal species such as the Brushtail Possum, Ringtail Possum and Sugar Glider Gliders (Petaurus breviceps). Species such as Sugar Gliders, although considered more common, form regionally significant populations as evidenced by the paucity of records for various mammals in Western Sydney, particularly in the urban and agricultural areas and the Cumberland Plain. Non-threatened animals such as Sugar Gliders, Brown Antechinus, Bush Rats and Eastern Pygmy Possum have been recently shown to have a very important role in the pollination and thus reproduction of certain native plants (Goldingay & Carthew 1997).

The focus needs to be on creating larger connected vegetated areas to create regional habitat. In essence, this means retaining suitable areas and preventing or more often reversing the many factors of degradation. The idea is to create or restore areas suitable for native fauna on the assumption that they are present or may recolonise.

A focus on restoration of habitat on-the ground, is preferable to putting vast and often unproductive efforts into species-specific surveys to determine if they are indeed present. Concentrating on surveys is particularly unproductive when dealing with species which are trap-shy, otherwise hard to detect and/or in very low numbers eg. bats. Appropriate habitat enhancement and maintenance strategies include controlled and strategic weed removal, installation of nest boxes, minimising trails, switching to lopping rather than clearing in electricity line corridors, pest animal control, reducing edge/area ratios and establishing habitat corridors to reduce fragmentation.

2. Significant Fauna Habitats

In general, the occurrence of significant fauna habitats coincides with significant vegetation remnants. However, within these remnants, there are a number of attributes which are particularly important for certain types of fauna and some remnants which are significant because of their size or vegetation type may not have all of these habitat attributes or will have them in varying proportions.

Important habitat attributes include:

• tree hollows (used by animals such as bats, birds, gliders, possums and pythons),
• loose rock and rock ledges (important for reptiles and some frogs),
• caves and some artificial hollows (used by bats),
• riparian vegetation (important for frogs and many other animals),
• instream v egetation eg. the reedlands around parts of Lake Parramatta (very important for frogs and waterbirds), dense understorey vegetation (even when this is weedy as it still provides shelter for small birds and particularly the Ringtail Possum),
• leaf litter (for reptiles and some amphibians),
• certain plant species such as Eucalyptus saligna and E. fibrosa (which are important for some threatened bird species),
• grasslands (as a rare habitat with often specific fauna),
• the small heath and sedge areas which occur in sandstone terrain often associated with groundwater seepage eg. from shale lenses in sandstone (for some reptiles and amphibians),
• he open woodlands of the Cumberland Plain (simply because they are so rare and support a fairly specific bird fauna),
• and shrubs with abundant berries such as Acmena smithii and Glochidion ferdinandi (which can be important for fruit pigeons).

Many of these habitat attributes are also important for the invertebrate species which are consumed by vertebrate fauna and which have vital roles in processes such as pollination, nutrient recycling and seed dispersal. For example, leaf litter often harbours not only skinks but insects on which they prey and provides cover for the ants which are important in the dispersal and burial of Acacia seeds. Thus it is very important not to oversimplify habitat and its attributes. Certainly, it is often valuable to examine a remnant in terms of how many tree hollows it has and to install and manage artificial hollows to improve this aspect. However, it must be remembered that assessing the significance of a site for vertebrates, particularly the so-called charismatic megafauna such as Powerful Owls or the "cute & furies" like gliders, is only part of ecological whole. The distribution of habitat is shown on the map habitat in Part 6 of this document.

1. Maintenance And Restoration Of Threatened Fauna Habitats

Priority should go to maintaining and recreating the habitat of species, which are threatened and known to occur in the area either as residents, migrants or vagrants. This can be followed up by working to maintain and recreate suitable habitat for species, which may be present or may recolonise the area from known populations nearby. The third priority should be given to projects which protect regionally and locally significant populations of otherwise common species. None of these approaches is mutually exclusive. Indeed they are all interwoven at an ecological level because many activities will likely have flow-on benefits for the whole ecosystem. Although at this point there may arise a very difficult issue, whereby measures to promote the survival of one component of the ecosystem may have deleterious effects on other components. More specifically, it raises the question of whether management for a threatened species (flora or fauna) should take precedence over that for a threatened ecological community. Circumstances such as these may well arise in the catchment and indicate the need to involve specialist expertise in the management of bushland and its various components.

An example of a conflict between managing bushland for flora-oriented values such as maintenance of the botanical community and managing for fauna (threatened or otherwise) can be drawn from the all too prevalent problem of (over-) clearing of weeds.

The rapid removal of understorey, even if it is predominantly weed species such as Lantana and Privet, can have devastating impacts on local native fauna populations through loss of habitat and exposure to predators, competitors and other threats such as vehicles (eg. McAllan & Ondinea, 1995). The often linear and isolated nature of much of the area’s bushland means that remnant native fauna is particularly threatened by overclearing of weeds and by subsequent fires that burn most of the remnant patch, leaving little or no shelter.

There are unfortunately numerous examples of bushland management projects where this has been the case but most occurred during the early days of municipally-based bush regeneration in Sydney before the professionalisation of the bush regeneration industry. Despite a growing understanding of this issue, the practise of excessively rapid and extensive weeding followed by "broad area" burning continues, with recent examples seen at Sophia Doyle Reserve in Baulkham Hills along upper Toongabbie Creek. This particular example also highlighted the problems of using unskilled or underskilled labour, in this case day-release prisoners under community supervision. These issues are discussed further in the Draft Vegetation Management Strategy.

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2. Threatening Processes Affecting Remnant Bushland

The UBBS list of general threatening processes is again a good outline of the pressures affecting the Catchment’s bushland as well as its flora and fauna populations and species:

• habitat loss, fragmentation and degradation;
• introduced species;
• altered fire regimes;
• pollution (various types); and
• climate change.

The Upper Parramatta River Catchment is somewhat different to the whole of Western Sydney in that very little remnant vegetation remains in private ownership. For this reason, it isn’t the usual pressures of urban and industrial development which represent the major threat to the Catchment’s remaining bushland. Such pressures have in large part already eliminated or degraded areas available for these activities. As most of the Catchment’s bushland is in public open space covered by SEPP 19, the major threat is not direct clearing for housing or industrial estates as it is on much of the Cumberland Plain and in the North-West Sector. Whilst in more recently urbanised and rapidly growing areas such as Kellyville and Rouse Hill, bushland in public open space is at considerable risk from the construction of intensive recreation facilities, most of the Catchment’s reserves have already had such features constructed in them. The main threats to the Catchment’s open space bushland are those related to the management of weeds and pest fauna, mowing, drainage, access and use, fire, revegetation and rubbish dumping, existing internal and external fragmentation and climate change.

1. Mowing

During field work for this report, many of the smaller areas of open space were found to be subject to extensive mowing. This was particularly prevalent in the endangered shale-based vegetation communities where in contrast to the steep and rocky sandstone environments, the gentle terrain allows mowing to occur. In such situations, often all that remains to be seen are mature trees, landscape plantings (which are often non-indigenous) and a few native understorey plants at the base of tree trunks or in hard to mow areas. Mowing of sites with largely undisturbed soil and a potential seed bank suppresses natural resilience and regeneration. Unless mowing of such parklands is stopped or greatly reduced in extent, the potential for these areas to return to bushland will be greatly diminished and eventually eliminated. Even in areas where there is little chance of the understorey regenerating but where the canopy remains, mowing will mean that most of the remaining vegetation will die through old age and ecological stresses and will not be replaced due to a lack of seedling recruitment, thus leading to total loss of this remnant vegetation.

Some councils have implemented "no mow" zones in suitable sites to allow natural regeneration of native understorey, also reducing park management costs and greenhouse gas emissions. This can be a very effective way of converting mown parkland with minimal ecological and aesthetic values into valuable flora and fauna habitat (for further information see James T. 1994).

 

2. Fragmentation and Edge Effects

As has been mentioned in earlier sections, most remnants in the catchment and indeed much of Sydney, are based in gullies with some being little more than riparian strips in drainage reserves and floodways. This has often resulted in remnants which are very linear and thus prone to so-called "edge effects" ie. the longer the boundary edge in relation to the area, the higher the level of ecological stress and the lower the viability of the remnant. This phenomenon of high edge to area ratio is worsened throughout Sydney by the fact that many of these corridors are isolated from one another as a result of clearing, settlement, and establishment of transport corridors along the ridges which once provided cross-catchment links. Many remnants are also internally fragmented by utility corridors and trails including powerlines, sewerage, roads and recreational and fire trails. Many such trails provide enhanced opportunities for weed invasion and pest animal access and hunting. Plans for construction of cycleways and formal walking tracks through bushland (as opposed to in parkland or adjoining bushland) represents a potentially significant threat to the Catchment’s urban bushland unless this is subject to strong ecologically based controls.

 

3. Altered Drainage Regimes

Clearing of bushland for farming and later settlement lead to a vastly different pattern of stream flows. This is magnified by the large increases in the area of impermeable surfaces from roads, roofs etc. which lead to more rapid and intense flood events worsening stream bank erosion. It has also polluted the waters with excess sediment and other sources of nutrients. Other interferences in the natural drainage regime such as old farm dams, weirs, fords and retention basins have also altered stream flows by causing temporary or permanent inundation. More recent constructions have aimed to reduce erosion and flooding downstream.

There are a number of ecological consequences arising from alterations to drainage regimes. Erosion and direct loss of riparian and instream vegetation and habitats is a major issue, as is their indirect loss through weed invasion and siltation. A more recent threat to the catchment’s bushland arises from public pressure to control post-settlement flooding and erosion problems. This has seen significant areas of remnant bushland destroyed or further degraded through the use of engineering techniques such as channelisation and in-stream engineering structures such as retarding basins and artificial wetlands. Some of these works such as channelisation are now being "de-constructed" in recognition of their limited engineering success and severe ecological consequences. As a result of such initiatives, streams are being recreated to be capable of carrying urban water flows whilst also re-establishing semi-natural vegetation and fauna habitats.

4. Weed Invasion

Weed invasion is often worst along the riparian zones and floodways where the disturbance caused by flooding, erosion and siltation together with moist conditions and nutrient enrichment has favoured the establishment of numerous exotic trees, shrubs, herbs and grasses. Privet, Lantana and Blackberry are common examples along with a growing range of "garden escapes" such as Impatiens, Fishbone Fern, Wandering Jew and Watsonia, many of which are still sold by nurseries and used by landscape contractors/designers and builders, home gardeners and some less informed councils. Most councils in Sydney have assembled large lists of noxious and environmental weeds which are either banned from sale or use or must be appropriately controlled. Noxious Weeds Act authorities also publish such lists, however enforcement by these agencies and councils (often the same body) is generally very poor due to a lack of resources and political commitment.

Weed invasion is also often moderate to severe along the boundary between bushland and private property, and bushland edges generally. This is caused by a range of factors such as nutrient enrichment from garden fertilisers, detergents, dog droppings, old septic tank trenches, increased soil moisture from urban runoff, landfill, sedimentation and the dumping of rubbish such as prunings and lawn clippings.

In remnants which are large enough to include areas which are neither edges or just the riparian zone, remnant vegetation is often free of weeds or at least not severely affected. This is because, particularly in the very infertile sandstone environments, poor nutrient levels have been a barrier to the establishment of many weed species. Such "core" areas need to be protected from creeping weed invasion moving in from the edges and the riparian zone.

Similar to modern attempts to control urban flooding and erosion, good intentions endeavouring to manage weed invasion can actually worsen the situation as is the case through excessively rapid removal of exotic weeds, which still provide substantial fauna habitat. This is particularly problematic in some of the more narrow linear riparian remnants where much of the understorey is composed of weed species which need to be removed. Are these eradicated too quickly, there can be almost no habitat left for species such as Ringtail Possums and many of the small bird species which have often only survived in the shelter provided by dense stands of Privet and/or Lantana. Over weeding can cause local extinctions, particularly in remnants which are isolated or which become isolated by removal of the weedy understorey.

In addition, over weeding can lead to more severe secondary weed invasion unless there is adequate follow-up weeding and regeneration or replanting as appropriate. Examples of over weeding were seen in the upper eastern Toongabbie Creek remnants such as Sophia Doyle and Torry Burn Reserves where unskilled prison labour was used and fire was employed on a larger scale than was appropriate for the size of these areas. Whilst such schemes can quickly and very cheaply remove large infestations of woody weeds such as Privet and Lantana, they do not adequately address ecological concerns such as the retention of native fauna and the protection of native vegetation including threatened species.

 

5. Introduced Species (fauna)

Almost all urban bushland will harbour pest fauna. Common pest include Black Rat, Norwegian Rat, House Mouse, Rabbit, Hare (mainly Cumberland Plain), European Red Fox, Cat, Dog, and Goat (in larger areas) along with a large range of introduced birds such as Indian Mynah and native birds which have moved into the area or which have become over-abundant as a result of habitat alterations by people eg. Galah, Sulphur Crested Cockatoo and Crested Pigeon.

During field work for this report disturbance to soil and vegetation by rabbits was evident at a number of locations and introduced bird species tended to predominate. During field survey for the UBBS, most remnants were found to harbour a range of common introduced fauna and no native ground mammals were found in remnants on the Cumberland Plain.

Introduced fauna can pose a range of threats to urban bushland communities. Impacts include predation of native species (for example by domestic and feral cats and the European Red Fox), displacement of native fauna (eg. Indian Mynahs competing for nest hollows), competition for food and/or shelter (eg. rabbits competing with macropods such as the Swamp Wallaby and foxes occupying Wombat burrows), and by more complex alterations of the ecology through flow-on and feedback effects (eg. stock grazing removes the understorey which would normally harbour a predatory wasp laying eggs inside Christmas Beetle larvae and which is thus critical for preventing these larvae from overgrazing Eucalypt foliage, one form of "die back" and tree loss.

Pest fauna can be managed by direct controls such as trapping, shooting, poisoning etc. but in many urban bushland areas the main tool is habitat management. Exotic species are favoured by the altered landscape caused by human settlement and related activities. By making remnants larger, more connected and more natural (eg. by controlling weeds and optimising the use of fire etc.) managers will be favouring native species and thus helping to re-balance these altered ecosystems. Some pest fauna is almost impossible or at least often impractical to eliminate and habitat management to disfavour pests and encourage natives is likely to be a more realistic approach. The strengthening, reconstruction maintenance of remnants and habitat corridors will provide native fauna with more support in their competition with introduced species.

 

6. Altered Fire Regimes

The management of bushfire hazard in urban areas shares some similarities with efforts to address urban flooding and erosion. Both are often trying to deal with issues which are now of concern in areas which were developed for housing some time ago when these matters were rarely, if ever considered or addressed properly. As a consequence, both issues tend to come into conflict with objectives to protect the local environment whilst also providing necessary protection to property and human lives.

In many urban bushland areas, it is now very difficult or impossible to establish fire regimes which are optimal for the maintenance of conservation values. Limitations are imposed by the size of the remnant, the proximity of housing, fuel levels and vegetation changes from past fire regimes as well as controls on when burning can occur in relation to urban air quality considerations.

In most instances, urban bushland areas have to be managed by finding a compromise which allows fire authorities to meet their obligation to protect life and property whilst also protecting ecological values. Fire regime management and other hazard reduction techniques (such as mulching) can cause alterations to flora and fauna composition and the overall biodiversity. The causes of such alterations include the use of low intensity hazard reduction fires in cooler seasons, extremely high intensity wildfires, fires which are too frequent or too infrequent, and fires which burn out whole remnants or very large patches. Altered fire regimes can act as a very serious threat to biodiversity conservation and the following situation are the most common problems with fire management in urban bushland:

• low intensity fire in the cooler seasons leading to an alteration of community floristics and structure as many native species require hotter fires to release and germinate their seeds. Cool season fires expose any seedlings to the relatively dry winters and potential frost damage;

• too frequent fires due to over zealous burning and/or inefficient hazard reduction burning, eg. too many cool fires rather than fewer hotter and thus more effective fires. This can promote the conversion of forest to woodland and eventually to grassland as a high fire frequency does not provide enough time for many plants to set seed and can rapidly exhaust the food stores of those that re-sprout from lignotubers and rhizomes etc. Areas dominated by Bracken (Pteridium esculentum) and/or Bladey Grass (Imperata cylindrica) may have come about by too frequent burning;

• too frequent fire due to arson. This can have the same end result as above though the process will vary initially depending on when the fires are lit;

• too infrequent fires due to concerns about the risk that any fire may pose to housing and/or lack of suitable weather conditions for burning. This tends to lower biodiversity by allowing a few shrub species to become excessively dominant eg. Kunzea ambigua in Scrub and Heath and/or by suppressed germination of fire-dependent plants and can lead to a "mesic shift" in vegetation ie. a tendency for sclerophyll fire-dependent species to be replaced by mesophyll "rainforest" plants which are disfavoured by fire eg. Pittosporum undulatum.

Fire is also used as a tool in bush regeneration as it can assist in controlling weeds in some circumstances whilst also stimulating regeneration of many native sclerophyll plants. Problems can arise when such burning removes an excessive area of vegetation and fauna habitat, which in many small remnants is very easy to do. Most regeneration projects use pile burns or patch burns rather than so called "broad acre" burning. This allows for far more strategic employment of fire and tends to prevent local extinctions which can result from larger fire in small, isolated or otherwise vulnerable urban remnants. A good rule is that no remnant should be burnt at once and sufficient time should be provided between fires to allow restoration of habitat on the previously burnt patch before the next patch is burnt.

1. Climate Change

Human-induced climate change through the impacts of the greenhouse effect places additional pressure on remnant bushland and its biota. Changing climates will affect the structure and florisitics of vegetation, the availability of food resources, fire regimes, migration periods and a range of other parameters. To survive, species, populations and communities will have to move or otherwise adapt to these changes. The rate of human-induced climate change means that normal adaptive processes will be unlikely to provide much benefit for affected biota and so movement is their main defence. In such highly altered environments as the Upper Parramatta River Catchment, the ability of biota to shift with climate change is severely limited. The main limitation is the lack of connection between remnants of the catchment and between the catchment and remnants in the adjoining Georges River, Cattai Creek, South Creek and lower Parramatta River catchments. Without these connections, some biota will not be able to move into suitable habitat and will thus eventually become locally or regionally extinct as its habitat will have changed faster than its ability to adapt.

This situation is obviously extremely relevant to the Green Corridors Management Project and its objectives and is also addressed in the UBBS, Green Web-Sydney project and the Draft NSW Biodiversity Strategy amongst others. The rate of human-induced climate change means that even if most of the other threatening processes were addressed as fully as possible the need for biota to relocate in response to climate-based habitat changes will remain critical to the survival of some species, populations and communities.

Antcliff. P.J. 1988. Unpub. The status of native birds and mammals in the remnant vegetation of north west Sydney. University of Technology, Sydney.

Bannerman S.M. and Hazelton P.A. 1989. Soil landscapes of the Penrith 1:100 000 Sheet. Soil Conservation Service, Sydney.

Centre for Environmental and Urban Studies. 1983. Excelsior Reserve: a resources study. CEUS, Macquarie University, North Ryde (now Graduate School of the Environment).

Douglas S.M. 1995. Significant native vegetation of the Greater Cattai Region. Unpublished manuscript. E.S.P. Ecological Surveys & Planning, Hornsby.

Douglas S.M. and Seidlich B.A. 1997. Green Web-Sydney. Western Sydney Regional Organisation of Councils (Blacktown) and Australian Nature Conservation Agency, Canberra.

Ehmann H. (ed.) 1997. Threatened frogs of New South Wales: habitats, status and conservation. Frog & Tadpole Study Group NSW Inc, Sydney South.

Goldingay R. and Carthew S. 1997. "The forgotten pollinators". Nature Australia 25(11) pp.50-57.

James T.A. "Observation on the effects of mowing on native species in remnant bushland, western Sydney." Cunninghamia 3(3) pp. 515-519.

Land & Environment Planning. 1994. Fauna corridors and vegetation links in Hornsby Shire. Report to Hornsby Shire Council, Hornsby.

Lindsey T. undated. Encyclopedia of Australian birds. Webster Multimedia, Frenchs Forest.

McAllan I. and Ondinea D. 1995. Wildlife habitat corridors study for Lane Cove Council. Report to Lane Cove Council. Designing for Wildlife, Cremorne.

National Parks & Wildlife Service (NSW). 1997. Urban Bushland Biodiversity Survey (Western Sydney). The Service, Hurstville.

Strahan R. 1995. A photographic guide to mammals of Australia. New Holland Publishers (Ltd), Sydney.

Tyler M. undated.Michael Tyler’s Frogs of Australia. Webster Multimedia, Frenchs Forest.

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