National recovery plan for the Downy Wattle (Acacia pubescens)

NSW National Parks and Wildlife Service
Environment Australia, February 2003
ISBN 0 7313 6504 6

5. Distribution

5.1 Current and Historical Distribution

Acacia pubescens is restricted to the Sydney region. Its distribution is concentrated around the Bankstown-Fairfield-Rookwood area and the Pitt Town area, with outliers occurring at Barden Ridge, Oakdale and Mountain Lagoon. The current and historic distribution is illustrated in Figure 1.

Figure 1. Distribution of A. pubescens

Figure 1. Distribution of A. pubescens

Figure 1. Distribution of A. pubescens

A complete picture of the original distribution is not apparent. An article from 1914 states that the 'centre of activity' for the species is around the Georges River area, from Canterbury through Belmore and Bankstown to Liverpool, occurring with Melaleuca spp. (Anon. 1914). Although the distribution includes a large area, the extant sites are mostly small and fragmented, surrounded by development. It is assumed that the species was once more common across its range, given it occurs in an area which has largely been developed.

The list of 151 extant sites are tabled in Appendix 1. A number of sites were not included in this list due to inadequate location details, or because it is assumed they have been planted, or they have been lost due to clearing. These sites are listed in Appendix 2.

There are 116 populations of the species listed in Appendix 1, occurring at 151 sites, in 14 LGA's. The number of sites and populations in each LGA are listed in Table 1 below.

Table 1. Locations of A. pubescens by LGA
LGA No. of extant sites No. of extant populations
Auburn 11 11
Bankstown 40 36
Baulkham Hills 3 2
Blacktown 4 4
Canterbury 2 2
Fairfield 14 13
Hawkesbury 33 16
Holroyd 6 6
Liverpool 14 9
Parramatta 5 5
Rockdale 1 1
Strathfield 6 4
Sutherland 2 2
Wollondilly 10 5

Note that in this recovery plan, plants within 300 m of each other have been defined as the one population, as dispersal is considered likely to occur over this distance in Acacia spp. (D. Keith, NPWS, pers. comm.). Populations may consist of a number of sites, as sites are defined largely by tenure boundaries.

Acacia pubescens is a clonal species, so an individual (or genet) may occur as a number of clumps (or ramets). Appendix 1 contains data on the number of ramets recorded at each site, which indicates that a large percentage of sites have only a small number of plants. The data on the number of ramets in each population is summarised below. Note that the number of individuals in each population will be less than or equal to than these figures indicate.

Table 2. Number of ramets in each population
number of ramets in population 20-100 101-1000 >1000 unknown
no of populations 59 28 18 6 5
%age of total no of popns 51% 24% 16% 5% 4%

The large percentage of populations with fewer than 20 plants (51%) is worth noting.

As the number of A. pubescens individuals at a site is difficult to determine, another useful measure of the status and relative distribution of a species is the area occupied by each population. The following information is derived from the data in Appendix 1:

Table 3. Area occupied by each population
area occupied by population 2 300m2 - 1 ha >1 ha unknown
no of populations 77 18 10 11
%age of total no of popns 66% 16% 9% 9%

Again, the large percentage of sites that cover a very small area, is worth noting. Eighty-two per cent (82%) of populations are smaller than one hectare.

5.2 Tenure

Only five of the 151 known sites occur within conservation reserves (within Scheyville National Park and Windsor Downs Nature Reserve). (Note that some of the specimens at the Royal Botanic Gardens from the Mountain Lagoon area state that the location is within Wollemi National Park. However, the NPWS could only locate the species at one site in the Mountain Lagoon area, on land owned by the Department of Land and Water Conservation, ie. not within Wollemi National Park). Four other sites are on lands zoned for environmental protection (at Mountain Lagoon, Pleasure Point, Campbell Hill Pioneer Park and Duck River Reserve) and two sites owned by the Sydney Catchment Authority are being managed for nature conservation. The tenure of the remaining sites varies. The major land managers are listed in Table 4 below, from the data in Appendix 1.

Table 4. Tenure of A. pubescens sites
Land Manager Number of sites Percentage of sites
Councils 55 36%
Private 52 34%
Rail Infrastructure Corp. 13 9%
NPWS 5 3%
Other public authorities 26 17%

The data in table 4 demonstrates that a large percentage (66%) of the sites occur on lands in public ownership.

5.3 In situ and ex situ plantings

Some organisations have planted A. pubescens on land under their control. Before the introduction of the TSC Act , Bankstown Council planted A. pubescens in at least five reserves (at Mirambeena Reserve, Salt Pan Creek Reserve, Deepwater Park, Roberts Park and at The Crest of Bankstown). It is also believed that the RTA planted some plants along the M5 Motorway, which were taken from plants lost during its construction. Individuals of A. pubescens in these locations appear to be surviving well and flowering.

There are also ex situ plantings of the species in Mount Annan Botanic Garden, the Australian National Botanic Gardens and the Burrendong Arboretum. The species is sold in some commercial and Council nurseries, and is in cultivation as an ornamental in Europe and the USA (Leigh et al. 1984). None of these plantings has been included in the list of extant sites in Appendix 1.