Location and General Description
The southern Riverina portion of this ecoregion is an ancient riverine plain, with alluvial fans of unconsolidated sediments, and evidence of former stream channels. Low hills and plains of Palaeozoic rocks extend to the north, transitional to the alluvial fans and plains of the Darling Riverine Plain (Thackway and Cresswell 1995). Average annual rainfall varies from 500 mm to 300 mm, with higher rain falling in the west closer to the Great Dividing Range. The climate can largely be considered subhumid, transitioning to temperate semi-arid at the eastern edges (Read 1994).
Vegetation here was once almost entirely eucalypt woodland, forming a transition between the higher rainfall coastal margin and the arid central interior. However, native vegetation has been removed almost entirely and replaced by cereal cropping. To the north, near the New South Wales–Queensland boundary, original vegetation was grassy open woodland, with coolibah trees (Eucalpytus microtheca) over a cover of Mitchell grass (Astrebla lappacea). Mitchell grass and red river gums (Eucalyptus camaldulensis) extend further west along the Darling River. To the south, woodlands with low trees and tall shrubs extend through this ecoregion. These ‘layered woodlands’ have a herbaceous ground layer and a floristically diverse lower stratum. Genera represented in the lower stratum include Acacia, Callitris, and Casuarina. Dominant woodland trees include narrow-leaved ironbark (Eucalyptus crebra), poplar box (E. populnea), and silver-leaved ironbark (E. melanophloia) (AUSLIG 1990).
Positioned between arid and temperate regions, the Southeast Australian Temperate Savannas represent the western limit for a number of flora and fauna. A wide variety of threatened species are also found here, including the superb parrot (Polytelis swainsonii VU) and Mackay’s burrowing skink (Anomalopus mackayi VU), (Hilton-Taylor 2000). Other species under threat include the red goshawk (Erythrotriorchis radiatus VU), malleefowl (Leipoa ocellata VU), plains-wanderer (Pedionomus torquatus EN), and the swift parrot (Lathamus discolor EN) which winters here each summer, returning to Tasmania to breed. Although there are no endemic mammals, threatened mammals native to this ecoregion include the kultarr (Antechinomys laniger DD), the spotted-tailed quoll (Dasyurus maculatus VU), bridled nailtail wallaby (Onychogalea fraenata EN), and brush-tailed rock-wallaby (Petrogale penicillata VU). The eastern subspecies of western barred bandicoot (Perameles bougainville fasciata) is presumed extinct. This species remains only on offshore islands in Western Australia (Strahan 1999).
This southeastern wheatbelt region is an economically important area, supporting both wheat and sheep. Most of the native vegetation has been cleared, negatively impacting biodiversity and causing a decline in the native fauna. The 235 km2 Warrumbungle National Park is one the few protected areas in this ecoregion, but does not conserve typical savanna vegetation. This protected area contains the westernmost steep, rocky areas of the Great Dividing Range. A number of smaller nature reserves and national parks are found throughout the ecoregion. Conservation programs that focus on private lands are key because of the small, fragmented nature of remaining vegetation. Private landholders in New South Wales have shown themselves amenable to conserving remaining vegetation fragments (Hodgkins et al. 2000).
Types and Severity of Threat
Overgrazing and agricultural mismanagement are serious threats in this region. Native habitat is increasingly fragmented, as extensive clearing continues today (Siversen and Clarke 2000). Fragmented ‘edge habitats’ encourage the spread of aggressive or predatory species such as noisy miners (Manorina melanophrys) and Australian ravens (Corvus coronoides). Land degradation has led to increasing salinity and erosion. The Murray and Murrumbidgee Rivers are used in massive irrigation schemes which has led to reduced native fish stocks and increased salinity.
Justification of Ecoregion Delineation
The Southeast Australia Temperate Savannas ecoregion is a transition zone between southeastern forest and the arid inland. It includes three full IBRAs: ‘Darling Riverine Plains’, ‘Cobar Peneplain’, ‘Riverina’, and the southern New South Wales portion of ‘Brigalow Belt South’ (Thackway and Cresswell 1995).
Australian Surveying and Land Information Group (AUSLIG). 1990. Atlas of Australian Resources: Vegetation. Australian Government Publishing Service, Canberra, Australia.
Hilton-Taylor, C. 2000. 1998. The IUCN 2000 Red List of Threatened Species. IUCN, Gland, Switzerland and Cambridge, United Kingdom.
Hodgkins, D., D. Goldney, G. Watson, and G. Tyson. 2000. The attitudes of landholders to a range of environmental issues, including the values of remnant bushland in the central western region of New South Wales. Pages 336 – 350 in R. J. Hobbs and C. J. Yates, editors. Temperate Eucalypt Woodlands in Australia: biology, conservation, management, and restoration. Surrey Beatty & Sons, Chipping Norton, New South Wales, Australia.
Read, I. G. 1994. The bush: a guide to the vegetated landscapes of Australia. University of New South Wales Press, Sydney, Australia.
Sivertsen, D. and P. J. Clarke. 2000. Temperate woodlands in New South Wales: a brief overview of distribution, composition, and conservation. Pages 6 – 16 in R. J. Hobbs and C. J. Yates, editors. Temperate Eucalypt Woodlands in Australia: biology, conservation, management, and restoration. Surrey Beatty & Sons, Chipping Norton, New South Wales, Australia.
Strahan, R. 1998. The mammals of Australia. Australian Museum/Reed New Holland. Syndey, Australia.
Thackway, R. and I. D. Cresswell. editors. 1995. An Interim Biogeographic Regionalisation for Australia: a framework for establishing the national system of reserves, Version 4.0. Australian Nature Conservation Agency, Canberra.
Prepared by: Miranda Mockrin
Reviewed by: Roger Kitching