Robertson Rainforest in the Sydney Basin Bioregion - Determination to make a minor amendment to Part 3 of Schedule 1 of the Threatened Species Conservation Act

The Scientific Committee, established by the Threatened Species Conservation Act, has made a Determination to make a minor amendment to Part 3 of Schedule 1 (Endangered ecological communities) of the Act by inserting the Robertson Rainforest in the Sydney Basin Bioregion (as described in the determination of the Scientific Committee under Division 5 Part 2) and as a consequence to omit reference to the Robertson Rainforest in the Sydney Basin Bioregion (as described in the final determination to list the ecological community) which was published on pages 3702 to 3706 in the NSW Government Gazette No. 97 dated 15 June 2001. Minor amendments to the Schedules are provided for by Division 5 of Part 2 of the Act.

The Scientific Committee is of the opinion that the amendment is necessary or desirable to correct minor errors or omissions in the Determination in relation to the Thackway and Cresswell (1995) reference.

NSW Scientific Committee - final determination

The Scientific Committee has found that:

1. Robertson Rainforest in the Sydney Basin Bioregion is the name given to the ecological community characterised by the species assemblage listed in 2 below. The community occurs on high nutrient soils in high rainfall areas of the Southern Highlands. All sites are within the Sydney Basin Bioregion. Bioregions are defined in Thackway and Cresswell (1995).

2. Robertson Rainforest is characterised by the following assemblage:

3 The total species list of the 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 vertebrates and invertebrates, many of which are poorly known. Invertebrate species may be restricted to soils or canopy trees and shrubs. In any particular site not all of the assemblage listed above may be present. At any one time, seeds of some species may only be present in the soil seed bank with no above-ground individuals present. 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 Robertson Rainforest is a warm temperate/cool temperate rainforest type characterised by Quintinia sieberi, Polyosma cunninghamia and  Doryphora sassafras (Mills & Jakeman 1995).  Eucryphia moorei was probably common along streams. Tree and shrub species typically associated with this rainforest type are  Acmena smithii, Acacia melanoxylon,  Quintinia sieberi, Hymenanthera dentata, Coprosma quadrifida, Tasmannia insipida and occasionally  Ceratopetalum apetalum. Cool temperate components include  Olearia argophylla, Hedycarya angustifolia, Eucryphia moorei, Dicksonia antarctica and  Parsonsia brownii. Ground cover is a dense fern cover including  Lastreopsis microsora and  Microsorum pustulatum subsp.  pustulatum.

5 Robertson Rainforest is found on high fertility soils derived generally from Tertiary basalts (mainly the Robertson Basalt and Kangaroo Valley Basanite), at high altitudes (500-750 m) and under high rainfalls (1000-1600 mm per annum) (Mills & Jakeman 1995).

6 Robertson Rainforest is or has been known to occur in the Wingecarribee and Shoalhaven Local Government Area, but may occur elsewhere in the Sydney Basin Bioregion (sensu Thackway and Cresswell 1995). It has been reported from the Robertson plateau and Cambewarra Range (Mills & Jakeman 1995).

7 Disturbed Robertson Rainforest remnants are considered to form part of the community including areas where the vegetation would respond to assisted natural regeneration, such as where the natural soil and associated seedbank is still at least partially intact.

8 Robertson Rainforest has been extensively cleared for agriculture and rural development. About 400-600 ha or about 20% of its original extent is estimated to survive though mostly as fragmented remnants (Mills 1988). Remnants are often dominated by Acmena smithii,  Doryphora sassafras and  Acacia melanoxylon.

9 A remnant of Robertson Rainforest is conserved in Robertson Nature Reserve at Robertson.

10 Much of the remaining area of Robertson Rainforest is highly fragmented with much of it occurring on private land. Threatening processes include invasion of exotic weed species including Ligustrum sinense, Hedera helix, Lonicera japonica, Ilex aquifolium and clearing, grazing, trampling and further fragmentation.

11 In view of the originally restricted distribution of this community, its inadequate representation within conservation reserves, and threats from fragmentation and weed invasion, the Scientific Committee is of the opinion that Robertson Rainforest 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.

Dr Richard Major
Chairperson
Scientific Committee

Proposed Gazettal date: 14/10/11
Exhibition period: 14/10/11 - 9/12/11 

Note this ecological community was originally listed in 2001 as indicated in the determination

References

Mills, K. (1988) The clearing of Illawarra rainforest: problems in reconstructing pre-european vegetation patterns. Australian Geographer 19(2): 230-240.

Mills, K. & Jakeman, J. (1995) Rainforests of the Illawarra District. (Coachwood Publishing:Jamberoo)

Thackway R, Cresswell ID (1995) An interim biogeographic regionalisation for Australia: a framework for setting priorities in the National Reserves System Cooperative Program. (Version 4.0. Australian Nature Conservation Agency: Canberra.)