Darling Riverine Plains - biodiversity
Modern river channels in the bioregion support river red gum (Eucalyptus camaldulensis) and river cooba (Acacia stenophylla) communities, with some areas of river paperbark (Melaleuca trichostachya), especially along the tributaries of the Barwon. These species grow on the channel margin in the annual flood zone. Coolabah (Eucalyptus microtheca) can be found on the northern rivers.
Trees on the more distant flood plains differ with locality. Yellow box (Eucalyptus melliodora) communities are found in the upper Macquarie, poplar box (Eucalyptus populnea) communities occur on the Bogan, coolabah communities are found on the Culgoa and most of the more northern streams support black box (Eucalyptus largiflorens) vegetation.
Only the hardiest trees can survive the heavy clays of the backplains. These species include myall (Acacia pendula), poplar box and belah (Casuarina cristata) on the Bogan and Macquarie, and coolabah and black box on northern streams. Many plains are treeless, supporting only shrubs and grasses such as oldman saltbush (Atriplex nummularia), bladder saltbush (Atriplex vesicaria) and Mitchell grass (Astrebla sp.).
Landscapes closer to the hills support western plains woodlands, which consist of grey box (Eucalyptus microcarpa), Blakely's red gum (Eucalyptus blakelyi), silver-leaf ironbark (Eucalyptus melanophloia), poplar box, wilga (Geijera parviflora), rosewood (Heterodendrum oleifolium), belah, kurrajong (Brachychiton populneum), white cypress pine (Callitris glaucophulla), yarran (Acacia homalophylla), some brigalow (Acacia harpophylla) and several other species of Acacia.
Sandy soils on levees of old channels and dunes often have stands of white cypress pine. Lake beds may be bare or covered by clumped lignum (Muehlenbeckia cunninghamii) with a fringe of black box. Lunettes support stands of belah, some mallee, white pine, prickly wattle (Acacia victoriae), black bluebush (Maireana pyramidata), and sandhill canegrass (Zygochloa paradoxa).
On the lower reaches of the Darling through the anabranch, river red gums line the banks with old man saltbush and lignum. Billabongs and floodplains are characterised by black box, canegrass (Eragrostis australasica) and lignum, and adjacent dunes support prickly wattle, belah, narrow-leaf hopbush (Dodonea attenuata) and various bluebush species.
Swamp vegetation varies with duration and depth of flooding. Marshes supplied with more permanent water support associations of common reed (Phragmites australis), cumbungi (Typha sp.), water couch (Pseudoraphis spinescens) and aquatic species such as water milfoil (Myriophyllum propinquum) and duckweed (Lemna minor).
Less frequently flooded swamps support lignum and grasslands, especially water couch, and nardoo (Marsilea hirsuta) is also common.
Nineteen species listed in the TSC Act 1995 are known to occur within the Darling Riverine Plains Bioregion. Nine of these species are endangered and 10 are considered vulnerable (NSW NPWS 2001).
The Culgoa River floodplain supports a number of endangered species including the narrow-leaf bumble (Capparis loranthifolia var. loranthifolia) and climbing caustic (Euphorbia sarcostemmoides) (Kearle et al. 2002).
Regionally rare species occurring on the floodplain include bull wiregrass (Aristida longicollis), wirewood (Acacia coriacea), bowl daisy (Pluchea dentex), hairy spurge (Phyllanthus carpentarie) and sandplain riceflower (Pimelea penicillaris) (Environment Australia 2001).
Four species known to occur within the Darling Riverine Plains Bioregion are now listed in the TSC Act as extinct in NSW. All of these are known from only one or two records and all are recorded in the Atlas of NSW Wildlife (NSW NPWS 2001).
Other species of conservation significance that have been recorded in the bioregion include the rare plants Echinochloa lacunaria, Leptorhyncos waitzia, Ipomoea diamantinensis, Ptychosperma anomalum, Swainsona adenophylla, S. laxa, and Solanum karsensis (Bowen and Pressey 1993, cited in Morton et al. 1995).
The Darling Riverine Plains Bioregion includes the following endangered ecological communities listed in the TSC Act:
- Acacia loderi shrublands;
- artesian Springs ecological community;
- Carbeen (Corymbia tessellaris) open forest community in the Darling Riverine Plains and Brigalow Belt South bioregions; and
- native vegetation on the cracking clay soils of the Liverpool Plains.
Two endangered ecological communities in the Darling Riverine Plains Bioregion are listed under the Commonwealth EPBC Act 1999. These are:
- Brigalow (Acacia harpophylla dominant or co-dominant); and
- the community of native species dependent on the natural discharge of groundwater from the Great Artesian Basin (Kearle et al. 2002).
The bioregion is home to 25 amphibian species, 104 reptile species, 319 bird species and 58 mammal species. Of these, 63 species are listed in the TSC Act: 9 as extinct, 12 as endangered and 47 as vulnerable.
Records of amphibians in the Darling Riverine Plains include 7 species that are either endemic or largely restricted to the bioregion (Kearle et al. 2002). These are Crinia parinsignifera, C. sloanei, Limnodynastes fletcheri (long-thumbed frog), Limnodynastes interioris (giant banjo frog), Neobatrachus sudelli, Notaden bennettii (crucifix toad) and Cyclorana verrucosa.
No frog species known or predicted to occur in the Darling Riverine Plains Bioregion is listed as threatened in NSW. Although there are also no threatened populations of amphibians in the bioregion listed under the TSC Act, there have been no detailed studies of their status in the bioregion and areas such as the Gingham wetlands are considered to be worthy of such assessment (Kearle et al. 2002).
Six reptile species within the bioregion are listed in the schedules of the TSC Act, 1995. The fierce snake is listed as extinct in NSW, while 4 species are listed as vulnerable and one species, Anomalopus mackayi, is listed as endangered.
A number of reptile species recorded in the bioregion are either endemic or largely restricted to the bioregion (Kearle et al. 2002). These include Emydura macquarii, Delma plebia (leaden delma), Ctenotus allotropis, Ctenotus brachyonyx, Egernia modesta, Hemiaspis damelii (grey snake), Pseudechis guttatus, Simoselaps australis (coral snake), Anomalopus leuckartii (two-clawed worm-skink) and Anomalopus mackayi (listed under the TSC Act as endangered).
The range of the worm-skink Anomalopus mackayi is largely restricted to the Darling Riverine Plains (Cogger 1992). Its range has decreased because suitable habitat has been cleared for cropping or degraded by grazing (Cogger et al. 1993; Sadlier and Pressey 1994, cited in Morton et al. 1995).
Several species of snake are also affected by clearing of habitat (Morton et al. 1995). These include elapid snakes (Echiopsis curta), which are confined to mallee areas of the bioregion, the Notechis scutatus and the python Morelia spilota variegata, both of which are found in the riverine environs along the Murray-Darling system.
Waterbirds are a significant component of the bird fauna of the Darling Riverine Plains and have been more extensively studied than other bird species (Kearle et al. 2002). Thirty-five bird species in the bioregion have been listed in the TSC Act, 8 as endangered and 27 as vulnerable (NSW NPWS 2001).
Subtropical woodlands which occur in parts of the Darling Riverine Plains (as well as in portions of the Brigalow Belt South, Nandewar and New England Tableland bioregions) are recognised as key habitat areas for the conservation of threatened or near-threatened bird species (Garnett and Crowley 2000, cited in Kearle et al. 2002). Many waterbirds are known to breed in the bioregion, including the freckled duck (Stictonetta naevosa) (Blakers et al. 1984, cited in Morton et al. 1995).
A large proportion of the distribution of several bird species falls in the Darling Riverine Plains Bioregion. Such species include the spotted bowerbird (Chlamydera maculata), striped honeyeater (Plectorhyncha lanceolata) and plum-headed finch (Neochemia modesta) (Kearle et al. 2002).
In NSW, the red-tailed black cockatoo (Calyptorhyncus banksii graptogyne) occurs largely in association with Eucalyptus camaldulensis woodland, where it uses large hollows for nesting (Smith et al. 1994, cited in Kearle et al. 2002). Most NSW records of red-tailed black cockatoos are from this bioregion, generally in the vicinity of the Barwon-Darling River (Kearle et al. 2002).
Twenty-two threatened mammal species described for the bioregion are listed in the TSC Act. Ten species, including the numbat (Myrmecobius fasciatus), bilby (Macrotis lagotis) and burrowing bettong (Bettongia lesueur), are listed as extinct in NSW.
Nine species are listed as vulnerable and 3 species, the kultarr (Antechinomys laniger), southern hairy-nosed wombat (Lasiorhinus latifrons), which was recently rediscovered in this and the Murray Darling Depression Bioregion, (Ayers et al. 1996) and the silky mouse (Pseudomys apodemoides), are listed as endangered. (All three have TS profiles and the silky mouse is known from only one record.)
Populations of swamp wallaby (Wallabia bicolor), common brushtail possum (Trichosurus vulpecula), koala (Phascolarctus cinereus) and glider (Petaurus spp.), have been recorded in several surveys in the bioregion and are considered to be regionally significant (Smith et al. 1998, cited in Kearle et al. 2002), although they are not listed under the TSC Act.
Populations of the greater long-eared bat (Nyctophilus timoriensis) and the yellow-bellied sheathtail bat (Saccolaimus flaviventris) are considered to be sparse and at risk because their tree-roosting behaviour leaves them exposed to loss of habitat and predation by cats (Dickman et al. 1993, cited in Morton et al. 1995).
The two-spined blackfish (Gadopsis bispinosus), Murray jollytail (Galaxias rostrattus), Australian rainbowfish (Melanotaenia fluviatilis), Macquarie perch (Macquaria australasica), Murray cod (Maccullochella peeli) and silver perch (Bidyanus bidyanus) are endemic to the Murray-Darling system (Lloyd et al. 1991, cited in Morton et al. 1995).
A number of feral, introduced mammals have been recorded in the bioregion, including foxes, cats and pigs.
The bioregion supports river red gum (Eucalyptus camaldulensis) corridors along the Darling River and nearby floodplains, which are important for the diversity of birds in the bioregion, including many species that are more common to the wetter bioregions in the south or east. Species such as the vulnerable superb parrot (Polytelis swainsonii) use these river red gum habitats or nearby woodlands, while the adjacent reedy swamps are home to the vulnerable Australasian bittern (Botaurus poiciloptilus).
The pied currawong (Strepera graculina), little raven (Corvus mellori) and Torresian crow (Corvus orru) have increased in number in the bioregion, as have numbers of freshwater, woodland and forest species and some ground-feeding granivores. Species are likely to be lost unless efforts are made to protect, enhance and link forest fragments. Hollows within riparian forests in the bioregion must also be retained.
The distribution of the smooth knob-tailed gecko (Nephrurus levis) reaches its far eastern limit in the Broken Hill Complex Bioregion (Cogger 1992).
There are several bioregionally significant wetlands in the bioregion. The Namoi River Floodplain provides important habitat for the endangered bush stone curlew (Burhinus grallarius), even though its condition has been described as poor and still declining. Several vulnerable species, such as the koala (Phascolarctos cinereus), painted honeyeater (Grantiella picta) and brolga (Grus rubicundus) have been sighted on the floodplain.
Nettlegoe Lake occurs mainly in the Darling Riverine Plains Bioregion, with a small part extending into the Murray Darling Depression. It is described as being in fair condition.
In 1993, Kingsford et al. (1997) recorded more than 10,000 waterbirds here including grey teal (Anas gracilis), pink-eared duck (Malacorhynchus membranaceus) and Eurasian coot (Fulica atra). The vulnerable freckled duck (Stictonetta naevosa) was recorded on the lake in 1983, 1990, 1993 and 1999.
Poopelloe Lake is another significant wetland within the bioregion, although it has been described as degraded and its condition is declining. Kingsford et al. (1997) used modelling to predict that the lake could support 20,000 waterbirds. The vulnerable Major Mitchell's cockatoo (Cacatua leadbeateri) has been recorded at the lake. Modelling has also been used for Wongalara Lake, also significant in the bioregion, to predict that it could provide habitat for 12,000 waterbirds.
The Darling River floodplain is another significant wetland, which supported almost 139,000 waterbirds in 1984. The species with the highest abundance were grey teal (Anas gracilis), hardhead (Aythya australis), black-tailed native hen (Gallinula ventralis) and Australian pelican (Pelecanus conspicillatus). In the same year the floodplain provided nesting habitat for almost 200 yellow-billed spoonbill (Platalea flavipes). In 1998, Pacific black duck (Anas superciliosa) also used the area for nesting.
This section of the Darling River is important for many threatened species. The vulnerable Major Mitchell's cockatoo, red-tailed black cockatoo (Calyptorhynchus banksii) and Australasian bittern (Botaurus poiciloptilus) have all been recorded here (NSW NPWS 2001).
Wetlands in the Darling Riverine Plains Bioregion are affected by changed hydrology, often where water regulation and abstraction results in increased flows for the lakes and decreased flows for the floodplains. Construction of levee banks, lakebed cropping and weir construction upstream is also a problem for some of the wetlands.
Other impacts include feral animals, exotic weeds, salinity and grazing pressure. Despite these impacts, the wetlands still provide important habitat for waterbirds in the bioregion, and indeed across the state.
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Page last updated: 27 February 2011