Written by Doug Benson, Royal Botanic Gardens, Sydney.
About the Remnant
In November 1992 I visited a very interesting remnant of native vegetation on the banks of the Cooks River at the end of Third Avenue, Campsie. The site occupies about 0.5 hectares between the Cooks River and its junction with a small stormwater canal (both being concrete lined channels). Geologically the site is on the end of a ridge of Wianamatta Shale, the soil being heavy clay and having a number of bare patches. On the lower slopes of the ridge fill has been deposited to build up the banks of the Cooks River and the canal.
The vegetation has patches of scrub, grassland and some trees. Most of the vegetation is of native plants, native to the site, many of which are growing very vigorously. In particular, in some of the more open areas there is a rich flora of ground cover species in particular grasses and prostrate small shrubs, such as Astroloma humifusum, Calotis cuneifolia, Goodenia hederacea. There was a patch of the orchid Microtis unifolia and some very impressive clumps of Xanthorrhoea media. Populations of Calotis cuneifolia, Hibbertia serpyllifolia and Oxylobium ilicifolia are probably the only natural occurrences surviving in western Sydney. Patches of shrubs include Kunzea ambigua, Leptospermum trinervium and shrubby trees of Syncarpia glomulifera. One of the reasons for the vigorous native plant growth is that the natural soils have been essentially unmodified and have not received nutrients in runoff from other areas. In comparison, the areas with filled soil have a significant number of weeds.
Importance of the Remnant
The vegetation is a small remnant of the original Wianamatta Shale based vegetation of the inner west and southwestern part of Sydney, part of the Turpentine-Ironbark Forest described by Benson and Howell (Taken for Granted: The bushland of Sydney and its suburbs, Kangaroo Press, Sydney, 1990). It is virtually the only remnant of such vegetation for many kilometres, the only other remnants being at Silverwater and Concord. It is also virtually the only remnant of native vegetation on the banks of the Cooks River. The only other native vegetation in the Cooks River valley is along Wolli Creek, associated with outcropping sandstone in Girrahween Park and having a different species composition from this remnant on shale at Campsie.
The remnant of vegetation at Third Avenue Campsie is a very significant remnant of native vegetation and should be protected carefully. The site itself is open and does not receive runoff, so is protected from weed invasion that is characteristic of other bushland sites in Sydney.
The area should be maintained as natural bushland for its scientific and for its natural heritage significance. It maintains a remnant of the original natural landscape of this part of Sydney. Its plants contain the local genotypes of the species that grew on shale soils in this region; preserving this genetic variation is an important component of regional plant conservation.
The area is small and needs careful protection. The vegetation is in good condition with many species flowering and fruiting. There is little weed growth within the main area of bushland, weeds being confined to the filled sites along the immediate banks of the river. Because of its size and the small numbers of some of the plant species it contains, the area could be prone to over-trampling and removal of species. At present access to the site is difficult, involving crossing the stormwater canal, and this has probably protected it from further damage. It is therefore recommended that access not be improved, but that the whole of the site be regarded as a significant conservation reserve. Some localised weeding, e.g., removal of some lantana, could be carried out, but this would have to be done carefully to avoid damage to native species. An organisation like the National Trust which has specific expertise in bush regeneration, should be called on for comment. Nor should the openness of the site, with many patches of bare soil be regarded as an invitation for tree-planting; rather the open areas are colonised by native species which are likely to be destroyed by shading and overgrowth of tree canopies. In the long term, after seed has been collected from the site and seedlings raised, some tree planting could be undertaken along the banks of the Cooks River, but care should be taken to ensure that any plantings are done from seed collected from the actual site to maintain the genetic integrity of the bushland.
Because of the smallness of the area and the fragility of many of the small ground cover species, it is recommended that educational use of the site involve interpretive displays elsewhere, perhaps in association with plantings or interpretive signage in nearby parkland. Campsie bushland would provide a very useful resource in designing display drawings reconstructing the Cooks River environment in past times, for example. Such uses would be more compatible than risking overtrampling of vegetation, e.g. by large school groups or uncontrolled weekend visitors.
Additional comment, March 1999
We have recently recognised that the original native vegetation of the upper Cooks River valley area was distinctive enough in its own right to be regarded as a separate plant community – the Cooks River Clay Plain Scrub Forest. This community appears to have occurred on clay loams on Wianamatta Shale along the broad shallow valleys of the upper Cooks River and Wolli Creek. Because so little of this community remains it has been listed as an Endangered Ecological Community under the NSW Threatened Species Conservation Act. The Third Ave Campsie Bushland is part of this community, rather than the Turpentine-Ironbark Forest which would have occurred on deeper shale on the higher rises such as along Canterbury Road.