Broken Hill Complex - biodiversity
Mulga (Acacia aneura) communities coupled with chenopod shrubland composed of saltbush and bluebush communities (Benson 1999) characterise the vegetation of the bioregion (Morgan and Terrey 1992).
Belah (Casuarina cristata), rosewood (Alectryon oleifolius), white cypress pine (Callitris glaucophylla) and mallee communities also occur throughout the bioregion (Benson 1999). Most plants are very sensitive to available soil moisture and runoff patterns largely control vegetation distribution.
Range crests have sparse vegetation including mulga, dead finish (Acacia tetragonophylla) and scattered bluebush (Maireana sp.). Vegetation is more abundant and diverse on the deeper loamy soils of the footslopes and valleys, where there is more moisture.
Dominant species include belah, rosewood (Heterodendrum oleifolium), occasional beefwood (Grevillea striata) and leopardwood (Flindersia maculata). Bluebush, bladder saltbush (Atriplex vesicaria), prickly wattle (Acacia victoriae), turpentine (Eremophila sturtii), narrow-leaf hopbush (Dodonaea attenuata), copperburrs (Sclerolaena sp.), variable speargrass (Stipa variabilis) and forbs form a discontinuous understorey.
Limestone or dolomite outcrops have shallow, highly calcareous, brown loamy soils with generally sparse vegetation and some rare plant species such as curly mallee (Eucalyptus gillii).
The tops of mesas and tablelands are usually treeless except for occasional mulga, gidgee, dead finish and Eremophila sp., with bladder saltbush, pearl bluebush, copperburrs and annual grasses on the slopes.
Swamps and fresh lakes have a fringing of black box (Eucalyptus largiflorens) woodland with cane grass (Eragrostis australasica) and copperburrs on the lake bed. Lunettes have brown clayey sand which carry mulga, turpentine (Eremophila sturtii) and often pearl bluebush (Maireana sedifolia).
Larger stream channels support river red gum (Eucalyptus camaldulensis), some coolabah (Eucalyptus microtheca) and river cooba (Acacia stenophylla), with oldman saltbush (Atriplex nummularia) and thorny saltbush (Rhagodia spinescens) on the banks.
Sandplains and dunes have a varied cover of low trees and shrubs including mulga, nelia (Acacia loderi), needlewood (Hakea leucoptera), rosewood, clumps of belah, occasional leopardwood, dense patches of punty bush (Cassia eremophila), western boobialla (Myoporum montanum), emu bush (Eremophila longifolia), turpentine, narrow-leaf hopbush, prickly wattle, variable spear grass and copperburr.
The only occurrence of the mallee species Eucalyptus gillii in NSW is in the bioregion in the Barrier Range near Broken Hill (Benson 1999).
Several species are at risk in the bioregion. Listed as vulnerable in the TSC Act, Acacia carnei is threatened by rabbits grazing on seedlings (Auld 1993, cited in Morton et al. 1995). Bowen and Pressey (1993, cited in Morton et al. 1995) also reported Lepidium monoplocoides and Eleocharis obicis and Rhaphidospora bonneyana, which are both listed as Vulnerable under the TSC Act.
Several plants in the bioregion are considered to be rare, including Gahnia lanigera, Paspalidium clementii, Ixiochlamys nana, Pluchea baccharoides, Vittadinia arida, Atriplex lobativalvis, A. morrisii, Euphorbia sarcostemmoides and Goodenia berardiana (Bowen and Pressey 1993, cited in Morton et al. 1995).
A total of 195 species of birds, 58 species of reptiles, 5 species of amphibians and 37 species of mammals have been recorded in the Broken Hill Complex Bioregion (National Land and Water Resources Audit).
In this bioregion, the endangered yellow-footed rock-wallaby (Petrogale xanthopus) has a limited distribution centred on the Bynguano and Coturaundee Ranges between Mootwingee and White Cliffs, north of Broken Hill (Lim et al. 1987, Lim and Giles 1989, cited in Morton et al. 1995).
Since European settlement, the species has undergone dramatic decline, with several populations becoming extinct in the early 1900s. In NSW, the species consists of only one population of about 100 individuals living in two colonies in Mootwingee National Park and Coturaundee Nature Reserve.
The endangered Bolam's mouse (Pseudomys bolami) is a native rodent known from the mallee shrublands of the Broken Hill Complex and Murray Darling Depression bioregions. This species is nocturnal, spending its days sheltering in burrows while at night it is active, feeding on seeds, fruits, blossoms, grasses, herbs and insects.
Populations of letter-winged kites (Elanus scriptus), black-breasted buzzards (Hamirostra melanosternon), Australian bustards (Ardeotis kori), bush thick-knees (or bush stone-curlew) (Burhinus grallarius) and Bourke's parrots (Neophema bourkii) have been recorded in the bioregion and are considered to be at risk (Smith and Smith 1994; cited in Morton et al, 1995).
Populations of bush stone-curlew are also known from other bioregions in NSW but have not been recorded in the Broken Hill Complex Bioregion since the 1980s (NSW NPWS 1999a). As with other areas of western NSW, birds of the chenopod shrublands in the bioregion seem to be at risk of decline (Reid and Fleming 1992, cited in Morton et al. 1995).
The birds of the Broken Hill Complex Bioregion are fairly typical of those found elsewhere in the semi-arid zone of NSW. The diversity of birds in the bioregion is comparatively low but there are species with limited ranges, such as the chirruping wedgebill (Psopohdes cristatus), that occur here.
Both ground-nesting birds and ground-feeding insectivores have undergone a serious decline in their numbers in this bioregion. This can be partly attributed to grazing of extensive areas of habitat. Continued loss of ground-feeding insectivores is likely to continue unless the problem can be addressed by reduction of grazing pressure in suitable areas and protection of adequate habitat.
The agamid, or dragon lizard (Ctenophorus decresii), is reasonably restricted nationally, and in NSW is confined to several isolated sites in the Barrier Range. The skink (Ctenotus uber) is represented in NSW by a distinct specimen known only from five sites (Sadlier and Pressey 1994; cited in Morton et al. 1995).
Part of the Menindee Lakes system falls in the bioregion. This wetland is of national significance and is located along the Darling River in the Barrier Range Outwash Fans and Plains subregion. The Menindee Lakes system is managed for water storage for supply to South Australia.
Poor timing of inflow and outflow can result in habitat loss during breeding times and demand for irrigation water can exceed supply, leading to rapid depletion of residual pools during drought. Grazing occurs in the vicinity of the wetland, but is becoming more conservatively managed.
Weed species and feral animals, including rabbits, pigs, goats, foxes and cats, all present a threat to the biodiversity of the wetland.
Two other wetlands in the bioregion are identified as having subregional significance. Bancannia Lake, an intermittent freshwater lake located in the Barrier Range Outwash Fans and Plains subregion, is described as being in good condition.
It is an important aggregation site for fauna, supporting many waterbird species including the vulnerable freckled duck (Stictonetta naevosa), with sightings of the blue-billed duck (Oxyura australis). Grazing, feral animals and weed invasion all pose threats to this wetland.
Stephens Creek Reservoir in the Barrier Range subregion is a water-storage area. Sightings of rare fauna at the reservoir include the vulnerable blue-billed duck and the little pied bat (Chalinolobus picatus). The freckled duck and redthroat (Pyrrholaemus brunneus) have also been sighted. Cats are considered to be the greatest threat to the biodiversity of the wetland.
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Page last updated: 27 February 2011