Riverina - biodiversity
Modern river channels support river red gum (Eucalyptus camaldulensis) and river cooba (Acacia stenophylla) communities. Here on the sandy soils, the river red gum understorey is generally composed of herbaceous perennial, annual and post-flooding ephemeral species that alter with topography and flooding characteristics (Eardley 1999).
Nearby on the higher, more saline heavy grey and brown clays towards the outer perimeter of the floodplains, black box (Eucalyptus largiflorens) woodlands dominate with an understorey of salt-tolerant grasses, saltbushes and daisies (Eardley 1999).
On the highest, rarely flooded terraces, yellow box (Eucalyptus melliodora) communities occur along with cypress pine and grey box (Eucalyptus microcarpa) (Eardley 1999).
Further from the rivers, many plains are treeless and carry saltbush shrubland, composed of old man saltbush (Atriplex nummularia), bladder saltbush (Atriplex vesicaria), cotton bush (Maireana aphylla) and native grasslands (Danthonia spp and Stipa spp) (Eardley 1999). A formerly extensive community of myall (Acacia pendula) shrubland and old man saltbush on the backplains has almost vanished (Mitchell in prep).
Sandy soils on levees, old channels, dunes and lunettes have stands of white cypress pine (Callitris glaucophylla), sometimes with mallee and bluebush (Maireana sp.). Lake beds may be bare or covered by clumped lignum (Muehlenbeckia cunninghamii) with a fringe of black box.
Next to rivers and creeks, shrublands of lignum (Muehlenbeckia florulenta) and nitre goosefoot (Chenopodium nitrariaceum) dominate the flats and low-lying swamps (Eardley 1999). Swamps have wide margins of river red gum, black box and, depending on water depth, also support the common reed (Phragmites australis), cumbungi (Typha sp.), grasses and floating water plants.
As soil and water salinity increase downstream and saline clays become evident on lake floors, salt-tolerant species such as samphire (Arthrocnemum sp.) become common.
Although less characteristic of the Riverina, belah (Casuarina cristata) - rosewood (Alectryon oleifolius) and mallee (Eucalyptus socialis, E. dumosa) communities are common on the bioregional boundary. Mallee occurs on the calcareous, sandy soils that tend to be a feature of adjacent bioregions (Semple 1990, Porteners 1993, cited in Eardley 1999).
The Riverina Bioregion includes the Acacia loderi shrublands endangered ecological community listed under the TSC Act 1995.
The Riverina grassland communities that occur on red-brown and grey clays are nationally significant because the lowland grasslands of southeastern Australia are significantly threatened and also poorly conserved (Eardley 1999).
These communities support a number of threatened plant species such as the endemic red Swainson pea (Swainsona plagiotropis) as well as Swainsona murrayana, Sclerolaena napiformis, Brachycome chrysoglossa and Lepidium monoplocoides (Eardley 1999).
Twenty-eight threatened species from the Riverina Bioregion are listed in the schedules of the TSC Act (NSW NPWS 2001). Twelve of these are listed as endangered, 15 are listed as vulnerable and one species, Tetratheca pilosa ssp. pilosa, is considered extinct in the bioregion.
A member of the chenopod family, Maireana cheelii or chariot wheels, is listed as threatened in the NSW TSC Act as well as the Commonwealth EPBC Act. This species is restricted to the riverine plain of NSW, generally in the vicinity of Deniliquin and Hay, and therefore can be considered endemic to the Riverina Bioregion. The main areas of shrublands in NSW occur on the riverine plain (Cunningham et al. 1981).
Significant fauna known to occur in the riverine forests of the Riverina Bioregion include the superb parrot (Polytelis swainsonii), sugar glider (Petaurus breviceps), feathertail glider (Acrobates pygmaeus), squirrel glider (Petaurus norfolcensis), brush-tailed phascogale (Phascogale tapoatafa), koala (Phascolarctos cinereus), carpet python (Morelia spilota), freckled duck (Stictonetta naevosa) and peregrine falcon (Falco peregrinus) (Eardley 1999).
Black box woodlands provide significant habitat to a diversity of bird species including the bush thickknee (Burhinus magnirostris) and the superb parrot, which will only nest where box woodland occurs within 10 km of selected nest trees (usually river red gum) (Eardley 1999).
Species including the plains-wanderer (Pedionomus torquatus), bush thicknee, striped legless-lizard (Delmar Impar) and fat-tailed dunnart (Sminthopsis crassicaudata) are found in the shrublands and grasslands of the Riverina Bioregion (Eardley 1999).
The northern hairy-nosed wombat (Lasiorhinus krefftii) was once found throughout southwestern NSW, particularly in the Riverina Bioregion. However, competition with cattle, sheep and rabbits has led to the rapid decline of the species (Strahan 1983) and the wombat is now presumed extinct, listed in Schedule 1 part 4 of the TSC Act.
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 plains-wanderer (Pedionomus torquatus) is listed as endangered in the TSC Act and vulnerable in the EPBC Act, and although it is also found in the Murray Darling Depression Bioregion, the core of the range of this ground bird falls in the Riverina Bioregion. The species is largely confined to patches of sparse grassland and areas with low, open vegetation, often where the light topsoil is affected by wind erosion (NSW NPWS 1999). Conservation of this species is dependent on effective habitat management so as to avoid intensive cultivation, burning or overgrazing (Morton et al. 1995).
The endangered trout cod (Maccullochella macquariensis) is endemic to the section of the Murray-Darling system that lies in the Riverina Bioregion. The distribution of the Macquarie perch (Macquaria australasica) has declined to such an extent that its range is now restricted to the Murrumbidgee and Lachlan Rivers in the Riverina Bioregion (Morton et al. 1995) where previously it was widespread across the Murray-Darling River system.
This decline is a common trend among the 29 species of fish found within the Murray-Darling system (Morton et al. 1995), including the two-spined blackfish (Gadopsis bispinosus), Murray jollytail (Galaxias rostratus), Australian rainbowfish (Melanotaenia fluviatilis), Murray cod (Maccullochella peeli) and silver perch (Bidyanus bidyanus).
The effect of clearing and grazing, coupled with competition from introduced herbivores such as sheep and rabbits and the impact of carnivores such as foxes and cats, has resulted in a general decrease in the number and species of flora and fauna in the bioregion.
Small mammals such as the now rare bridled nail-tail wallaby (Onychogalea fraenata) and the extinct eastern hare-wallaby (Lagorchestes leporides) are obvious victims of both habitat modification and competition (Eardley 1999).
Important wetlands, which can support more than 20,000 waterbirds, occur in the Murrumbidgee-Lachlan confluence, Barmah-Millewa Forest, and Edward and Murrumbidgee River floodplains (Kingsford et al. 1996, cited in Eardley 1999). Many of these waterbirds are migratory and several, such as the Australasian bittern (Botaurus poiciloptilus), freckled duck and painted snipe (Rostratula benghalensis), are listed as vulnerable under the TSC Act (Eardley 1999).
Eight wetlands have been identified as having bioregional significance in the Riverina (Australian Terrestrial Biodiversity Assessment 2002).
Lake Urana provides habitat for the endangered winged peppercress (Lepidium monoplocoides) which is mainly found on the shores of the lake. Both the vulnerable freckled duck (Stictonetta naevosa) and the vulnerable brolga (Grus rubicundus) have been recorded here (NSW NPWS 2001a). Modelling has suggested that the Lake could support 11,000 waterbirds (Kingsford et al. 1997).
Loorica Lake supported almost 17,000 waterbirds in 1987, including the grey teal (Anas gracilis), hardhead (Aythya australis) and whiskered tern (Sterna hybrida) (Australian Terrestrial Biodiversity Assessment 2002). In 1983, Loorica Lake provided nesting habitat for the black swan (Cygnus atratus) (Australian Terrestrial Biodiversity Assessment 2002).
The vulnerable freckled duck, blue-billed duck (Oxyura australis) and black-tailed godwit (Limosa limosa) have also been recorded (NSW NPWS 2001). The black-tailed godwit, found at the Lake, is listed on the China-Australia Migratory Bird Agreement (CAMBA) and the Japan-Australia Migratory Bird Agreement (JAMBA) (NSW NPWS 2001).
An unnamed swamp southeast of Lake Tala supported more than 20,000 waterbirds in 1983, including the grey teal (Anas gracilis), pink-eared duck (Malacorhynchus membranaceus) and Eurasian coot (Fulica atra). In 1986 and 1987, 7,000 waterbirds were present in the swamp. In 1983 and 1988, the black swan (Cygnus atratus) used the swamp as a nesting site. The freckled duck has also been recorded here.
Gol Gol Lake is significant to this bioregion and also extends into part of the Murray Darling Depression Bioregion. The lake provides habitat for the endangered southern bell frog (Litoria raniformis) as well as many vulnerable species including the painted snipe (Rostratula benghalensis), freckled duck and square-tailed kite (Lophoictinia isura) (NSW NPWS 2001).
Another significant wetland in the bioregion is the Edward River Floodplain, with wetland modelling predicting that it could support 54,000 waterbirds (Kingsford et al. 1997). The vulnerable brolga (Grus rubicundus) and Major Mitchells cockatoo (Cacatua leadbeateri) have been recorded at the wetland as has the painted honeyeater (Grantiella picta) (NSW NPWS 2001a).
The Tuppal Creek Floodplain supports a range of threatened species including the vulnerable koala (Phascolarctos cinereus), superb parrot (Polytelis swainsonii) and Australian bustard (Ardeotis australis) (NSW NPWS 2001a). The endangered bush stone-curlew (Burhinus grallarius) and the vulnerable square-tailed kite (Lophoictinia isura) have also been recorded here. Modelling has predicted that this floodplain could support 19,000 waterbirds (Kingsford et al. 1997).
Morrisons Lake is reserved within the Morrisons Lake Nature Reserve. The Lake provides habitat for a range of threatened species including the vulnerable Major Mitchells cockatoo, square-tailed kite, blue-billed duck (Oxyura australis), grey falcon (Falco hypoleucos), freckled duck (Stictonetta naevosa), Australasian bittern (Botaurus poiciloptilus) and painted snipe (Rostratula benghalensis).
Barrenbox Swamp has also been described as significant to the Riverina Bioregion. The swamp provides habitat for the vulnerable freckled duck, blue-billed duck, Australasian bittern (Botaurus poiciloptilus), painted snipe (Rostratula benghalensis) and magpie goose (Anserenas semipalmata) (NSW NPWS 2001). The painted snipe is protected under CAMBA. The endangered bush stone-curlew (Burhinus grallarius) (NSW NPWS 2001a) and the southern bell frog (Litoria raniformis) have also been recorded here.
The Booligal wetlands have also been recognised as a refuge for biodiversity in the bioregion (Morton et al. 1995).
The NSW Central Murray State Forests, together with the listed Ramsar wetlands in Victoria (Barmah and Gunbower forests), form the largest complex of tree-dominated floodplain wetlands in southern Australia. The site contains wetland types that are rare within the Riverina bioregion, particularly types floodplain lakes and floodplain meadows and reed swamps and regularly supports more than 20,000 waterbirds (eg. Mattingley 1908, Barrett 1931, Chesterfield et al. 1984, Maher 1993, Leslie and Ward in press).
The site plays a substantial role in the functioning of the Murray River, particularly in terms of hydrology flood mitigation, water quality sediment deposition and river health and has recently been nominated for Ramsar listing.
It provides a habitat network for at least 8 globally threatened fauna listed by the World Conservation Union in 2000. The Australasian bittern (Botaurus poiciloptilus), superb parrot (Polytelis swainsonii), silver perch (Bidyanus bidyanus) and flat-headed galaxias (Galaxias rostrata) are listed as "vulnerable", and the regent honeyeater (Xanthomyza phrygia), swift parrot (Lathamus discolor), Murray hardyhead (Craterocephalus fluviatilis) and trout cod (Maccullochella macquariensis) are listed as "endangered" on the IUCN Red List (2000).
The Central Murray State Forests are ecologically linked through an unbroken riparian corridor along the Murray and Edward Rivers. They are in high ecological condition and provide arboreal and wetland habitat in landscapes extensively cleared of trees and developed for agriculture. As such, the site contributes significantly to the conservation of globally and nationally threatened species.
The site is immediately adjacent to other wetlands included in the Ramsar List of Wetlands of International Importance in the neighbouring state of Victoria, and thus, further enhances the viability of threatened flora and fauna species that occur at these Ramsar sites.
The area provides a habitat network for 13 species listed in migratory bird agreements between Australia, and Japan (JAMBA) and China (CAMBA). These species are painted snipe (Rostralula benghalensis), great egret (Ardea alba), cattle egret (Ardea ibis), sharp-tailed sandpiper (Calidris acuminata), greenshank (Tringa nebularia), marsh sandpiper (Tringa stagnatilis), Latham's snipe (Gallinago hardwickii), white-throated needletail (Hirundapus caudacutus), forked-tailed swift (Apus pacificus), glossy ibis (Plegadis falcinellus), Caspian tern (Hydropogne caspia), red-necked stint (Calidris ruficollis) and white-bellied sea-eagle (Haliaeetus leucogaster).
The wetlands of the Riverina Bioregion have been described as being in fair to degraded condition. Changed hydrology is a key threat to all of these wetlands, but there are also impacts from feral animals, exotic weeds, water extraction, regulation and diversion, altered nutrient levels, salinity, grazing pressure, reduced flows and use for water storage.
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Page last updated: 27 February 2011