Cooks River/Castlereagh ironbark forest in the Sydney Basin Bioregion - endangered ecological community listing

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Final Determination to list Cooks River/Castlereagh Ironbark Forest in the Sydney Basin Bioregion, as an ENDANGERED ECOLOGICAL COMMUNITY on Part 3 of Schedule 1 of the Act, and to omit reference to the Cooks River Clay Plain Scrub Forest as an Endangered Ecological Community. Listing of Endangered Ecological Communities is provided for by Part 2 of the Act.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Cooks River/Castlereagh Ironbark Forest in the Sydney Basin Bioregion is the name given to the ecological community characterised by the species assemblage listed in paragraph 2. All sites are within the Sydney Basin Bioregion.

2. Cooks River/Castlereagh Ironbark Forest is characterised by the following assemblage:

3. The total species list of flora and fauna of the community is considerably larger than that given in 2 (above), with many species present in only one or two sites or in very small quantity. The community includes invertebrates, many of which are poorly known, as well as vertebrates. In any particular site not all of the assemblage listed above may be present. At any one time, some species may only be present as seeds in the soil seed bank with no above-ground individuals present. Invertebrate species may be restricted to sediments or canopy trees and shrubs for example. The species composition of the site will be influenced by the size of the site and by its recent disturbance history. The number of species and the above-ground composition of species will change with time since fire, and may also change in response to changes in fire frequency.

4. Cooks River/Castlereagh Ironbark Forest is predominantly of open-forest to low woodland structure usually with trees of Eucalyptus fibrosa and  Melaleuca decora, sometimes with  Eucalyptus longifolia. A relatively dense shrub stratum is typical, commonly with  Melaleuca nodosa and  Lissanthe strigosa, and to a lesser extent  Melaleuca decora. A variety of shrub species may occur, including  Acacia pubescens,  Dillwynia tenuifolia,  Daviesia ulicifolia,  Pultenaea villosa and  Grevillea juniperina. Commonly occurring species in the ground stratum include  Entolasia stricta,  Lepidosperma laterale,  Opercularia diphylla,  Dianella revoluta,  Themeda australis,  Microlaena stipoides and  Pratia purpurascens.

5. Cooks River/Castlereagh Ironbark Forest usually occurs on clay soils on Tertiary alluvium, or on shale soils on Wianamatta Shale including the Birrong Soil Landscape and associated shale lowlands.

6. Cooks River/Castlereagh Ironbark Forest is described in NSW NPWS (2000a&b) which lists diagnostic plant species for the community. These species provide a guide to identification of the community, but care should be taken in the application and interpretation of diagnostic plant species because of sampling limitations; the reduction in species diversity in degraded sites; and the fact that some species may only be present at a site at some times as a soil seedbank or as dormant bud/tubers.

7. Cooks River/Castlereagh Ironbark Forest is or has been known to occur in the Auburn, Bankstown, Blacktown, Canterbury, Campbelltown, Fairfield, Hawkesbury, Holroyd, Liverpool, Parramatta, Penrith and Strathfield local government areas, but may occur elsewhere in the Sydney Basin Bioregion.

8. It occurred extensively in the Castlereagh area, Holsworthy-Voyager Point area, Kemps Creek area and the upper Cooks River valley, Duck River and associated shale lowlands in the Canterbury-Auburn-Strathfield- Bankstown-Parramatta-Holroyd area.

9. Cooks River/Castlereagh Ironbark Forest may grade into Castlereagh Swamp Woodland in poorly-drained depressions or into Castlereagh Scribbly Gum Woodland where the soil is sandier. Where the Tertiary alluvium is shallow, the community may grade into Shale Gravel Transition Forest.

10. Disturbed Cooks River/Castlereagh Ironbark Forest remnants are considered to form part of the community including remnants where the vegetation would respond to assisted natural regeneration such as where the natural soil and associated seedbank is still at least partially intact.

11. Cooks River/Castlereagh Ironbark Forest has been extensively cleared for urban and rural developments. About 7% of the original distribution is estimated to remain (NSW NPWS 2000a). There has been very extensive clearing and major fragmentation and isolation of remnants in the Canterbury-Auburn-Strathfield-Bankstown-Parramatta-Holroyd area. Much of the remaining area of Cooks River/Castlereagh Ironbark Forest elsewhere has been disturbed by clearing, tracks, weed invasion and soil disturbance. Continuing threats to the community include invasion by exotic species, illegal dumping, water pollution, unauthorised access, fragmentation and clearing for urban, rural-residential, recreational and industrial development.

12. Cooks River/Castlereagh Ironbark Forest has been reported from Agnes Banks Nature Reserve, Castlereagh Nature Reserve and Windsor Downs Nature Reserve. The area of the community in these reserves is about 1.7% of the original distribution.

13. The eastern occurrences of this community, in the Canterbury-Auburn-Strathfield- Bankstown-Parramatta-Holroyd area, are currently listed as the Cooks River Clay Plain Scrub Forest Endangered Ecological Community. The present determination recognises that similar areas in Western Sydney, previously not recognised as part of the community, should be included as part of the listed Endangered Ecological Community.

14. In view of the originally restricted distribution of this community, its inadequate representation within conservation reserves, the extensive disturbance and fragmentation and weed invasion that has occurred and the ongoing development and use threats, the Scientific Committee is of the opinion that Cooks River/Castlereagh Ironbark Forest in the Sydney Basin Bioregion is likely to become extinct in nature in New South Wales unless the circumstances and factors threatening its survival or evolutionary development cease to operate and that the community is eligible for listing as an endangered ecological community.

Proposed Gazettal date: 10/05/02
Exhibition period: 10/05/02 - 14/06/02

References

NSW NPWS (2000a). Native vegetation maps of the Cumberland Plain, western Sydney - Interpretation guidelines. NSW National Parks & Wildlife Service, January 2000.

NSW NPWS (2000b). The native vegetation of the Cumberland Plain, Western Sydney - Technical report. NSW National Parks & Wildlife Service, April 2000