Rangelands - Overview
Ord-Victoria Plains
Summary
- Includes land within Western Australia and the Northern Territory and covers much of the upper catchments of the Ord and Victoria River systems.
- The population is low, with people living on pastoral stations and small Aboriginal settlements with a few hundred people or less.
- The region has a semi-arid monsoonal climate.
- The bioregion forms an interzone for some bird and mammal species of the arid and tropical regions.
- Tourism is an important industry in the region focussing on the distinctive features of Purnululu (Bungle Bungle) National Park in WA and Gregory National Park in the NT.
- Mining is the largest contributor to the economy, particularly the Argyle diamond mine.
ATSIC Boundaries
Catchment Basins
Statistical Local Areas
Introduction
The Ord-Victoria Plains bioregion covers an area of 125,400 sq km in the Northern Territory and Western Australia. 56% of the bioregion is in the Northern Territory. The bioregion includes much of the upper catchments of both the Ord and Victoria River systems.
The population is low. Settlements in the NT include the Aboriginal communities of Kalkarinji (with the largest population of 259), Daguragu and Yarralin. Halls Creek and Warmum in WA lie just outside the bioregion. Lake Argyle is on the boundary between the Ord-Victoria Plains bioregion and the Victoria Bonaparte bioregion.
The region includes Purnululu (Bungle Bungle) National Park in WA and part of the Gregory National Park in NT. The Argyle diamond mine is within the region.
Natural Environment
Climate
The region is semi-arid with a dry, warm monsoonal climate. The rainy season lasts for four or five months over summer, and there is little rain for the remainder of the year. Rainfall in the bioregion ranges from 375mm to 625mm. Victoria River Downs Station in the north east of the bioregion has a mean annual rainfall of 620mm.
Temperatures at Victoria River Downs range from 25? C -38.6? C in summer and10.6? C - 28.9? C in winter.
Climate averages are available for Victoria River Downs:
http://www.bom.gov.au/climate/map/climate_avgs/a14f.shtml
Temperature and rainfall graphs are available for Victoria River Downs:
www.bom.gov.au/climate/forms/map_forms/new_imagemaps/nt_name.html
Current seasonal conditions and their historical context can be provided by satellite imagery. The Normalised Difference Vegetation Index (NDVI) is a measure of the vegetation 'greenness'. The NDVI for the Ord-Victoria Plains bioregion for this year and previous years can be found at: www.ea.gov.au/land/monitoring/ttrace/ovp.html
The bioregion contains three defined geomorphic units. The west of the bioregion incorporates the Halls Creek Ridges and abuts the Kimberley Plateau. The Ord River Basin sub-region contains the middle reaches of the Ord River where there are extensive plains and dissected volcanics forming mesas and buttes. The upper Victoria River catchment is mostly an undulating plain, which rises gradually to the Sturt Plateau in the south. There are also scattered mesas and buttes and a series of benches in the east.
Most of the bioregion falls within the Victoria River Basin with the Cambrian (490-545 million years ago) Antrim Plateau Volcanics a dominant rock formation. Middle Cambrian limestone and shale and Devonian (354-410 million years ago) sandstones are also present (Kerle, 1996).
For more detailed geological information and map refer to the Australian Geological Survey Organisation website: www.agso.gov.au/map/ and the Northern Territory Geological Survey website:
www.dme.nt.gov.au/ntgs/ntgs/geo_overview/geo_over.html
Shallow, immature skeletal soils occur on the steep tablelands and hills, ranges and rocky outcrops. Deep black soils occur on the gentle slopes. Leached and deeply weathered red/yellow earths and lateritic podsolics occur on the interior plateau (Kerle, 1996).
For more soils information refer to the Digital Atlas of Australian Soils at:
www.brs.gov.au/data/datasets/atlas/index.html
Connors et. al., (1996) have identified 999 plant species in the Northern Territory section of the bioregion including 39 species that are rare and threatened.
There are three broad vegetation groups, those occurring in rocky country, the woodlands and grasslands of the undulating plains; and communities of the watercourses (Kerle, 1996).
The rocky country consists of mostly low open-woodlands with dominant species being snappy gum (E. brevifolia) in the south and mixed taller woodland of variable-barked bloodwood (Corymbria dichromophloia), stringybark (E. tetrodonta) and Darwin woolly butt (E. miniata) in the north. The understorey is generally hummock grassland of spinifex or golden beard grass. The shrub layer is absent or very sparse.
Bauhinia (Lysiphyllum cunninghamii) low open woodland with a grassland understorey occurs on rocky limestone outcrops south of Timber Creek.
On the undulating plains a range of grassland communities occur including mitchell grass (Astreleba sp.) grassland. Beard grass (Chrysopogon fallax) / blue grass (Dichanthium fecundum) is the predominant grassland on clay soils further north.
Woodland communities occur extensively on the plains in the north of the bioregion with a grassland understorey with golden beard grass and white grass (Sehima nervosum). Communities include low Eucalypt woodland dominated by bloodwood (Corymbria terminalis) and southern box (E. chlorophylla) occurs on the Victoria Plateau.
Along the watercourses, bluebush (Chenopodium auricomum) low open-shrubland occurs along Sturt Creek in the southwest, and coolibah (E. microtheca) low open woodland grows on some drainage lines in the south and east (Kerle, 1996).
364 vertebrate species have been recorded in the NT part of the bioregion with 15 rare and threatened species. These include the pig nosed turtle (Carettochelys insculpta), the greater bilby (Macrotis lagotis), central pebble mound mouse (Pseudomys johnsoni) (Connors, et. al., 1996).
This bioregion along with the Sturt Plateau and the Gulf Falls bioregions form an interzone for some species of the arid and tropical fauna of northern Australia. This is reflected in the mammals of the region, with a high diversity of macropods. These range from the red kangaroo, which is adapted to arid areas, to the northern nail-tail wallaby (Onychogalea urguifera) and spectacled hare wallaby (Lagorchestes conspicillatus) of the sub-tropical grasslands to the more tropical agile wallaby (Macropus agilis).
Birds also reflect the overlap between tropical and arid species. Those more commonly found in the arid zone include the ground cuckoo-shrike (Coracina maxima), while more typical tropical species include the blue-winged kookaburra (Dacelo leachii), rufous-throated honeyeater (Conopophila rufogalaris) and crimson finch (Neochimia phaeton).
Freshwater crocodiles and two turtle species are found in the rivers (Kerle, 1996).
Small and medium sized mammals, which appear to have become regionally extinct or much less common since European contact, include golden bandicoot (Isoodon auratus), northern brown bandicoot (Isoodon macrorus), northern quoll (Dasyurus hallucatus), brush-tailed possum (Trichosurus vulpecula) and brush-tailed phascogale (Phascogale tapoatafa). Two riparian birds, the white-browed robin (Poecilodryas superciliosa) and purple crowned fairy-wren (Malurus coronatus) have declined along extensive stretches of major rivers (Woinarski, et. al., in prep.).
Land Tenure & Use
Lands include pastoral lease, Aboriginal land and conservation reserves.
83% of the NT part of the bioregion (57,328 sq km) is pastoral lease or freehold, 8.2% (5,659 sq km) is Aboriginal freehold and 5.2% (3,598 sq km) is reserved for conservation.
National Parks include Purnululu in WA and parts of Gregory National Park in NT
The major land use in the region is cattle grazing, generally with high economic viability (Connors et. al., 1996), with areas of Aboriginal land, nature reserves and vacant crown land. The nature reserves are generally on rocky country with low pastoral suitability, and are not particularly representative. Mining is also an important industry.
Tourism is an important industry focussing on natural features such as Purnululu (Bungle Bungle) National Park (WA) and Gregory National Park (NT).
Lake Argyle on the Ord River is on the boundary between this bioregion and Victoria Bonaparte to the north.
For more details refer to the Tropical Savanna website which covers larger regions on either side of the border. For the Kimberley region on the WA side of the border:
www.savanna.ntu.edu.au/information/savannaexplorer.html
and the VRD-Sturt region within the NT:
www.savanna.ntu.edu.au/information/savannaexplorer.html
Condition Of The Landscape
Land degradation
Connors, et. al., 1996 provides a summary of information on land degradation from a number of sources including fire, herbivores, weeds and tourism.
The long history of pastoral use has left a legacy of land degradation in many of the region's most productive areas (www.savanna.ntu.edu.au/information/savannaexplorer.html).
There has been scalding and erosion (both sheet and gully) and a widespread replacement of preferred grasses by less palatable species and exotic weeds. In some areas a decline in desirable species such as golden beard grass has occurred, and an increase in undesirable annual grasses (Aristida sp.).
In some areas overgrazing and changes in fire regimes have combined to increase the density of native shrubs and lowered the lands productive capacity. This combination has also left large areas vulnerable to invasion by weeds including exotic woody species such as parkinsonia (Parkinsonia aculeata) and castor oil plant (Ricinus communis).
High frequency of intense fires is degrading Lancewood vegetation in the bioregion.
Land condition has probably gradually improved over the last few decades as stocking rates have been set a sustainable level (Woinarski, et. al., in prep.).
The feral cat is distributed throughout the region. Other pests include feral pigeons, horses, donkeys, water buffalo and pigs. The fox is a seasonal problem in small isolated pockets. (Morton et. al., 1995)
Weeds include parkinsonia (Parkinsonia arcuata), which forms impenetrable thorny thickets, devil's claw (Martynia annua), rubberbush (Calotropis procera), and a wide variety of burrs and prickles are widespread and completely dominate some areas, particularly along riverbanks and watercourses. Localised weed problems exist including spread of buffel grass (Cenchrus ciliaris), bellyache bush (Jatropha gossypifolia), noogoora burr (Xanthium strumarium) and prickly acacia (Acacia nilotica) (Woinarski, et. al., in prep.).
For more details see the Tropical Savanna website: www.savanna.ntu.edu.au/information/savannaexplorer.html
Social & Economic Aspects
People
This bioregion generally lies to the south of the Great Northern and Victoria Highways and is very sparsely populated. The population is limited to a number of pastoral stations such as Victoria River Downs and small Aboriginal communities such as Kalkarindji with 259 people.
Aboriginal lands in the NT include Daguragu, Yarralin, Wambardi and part of Wanimiyan. Aboriginal lands in WA include Elvire, Bohemia Downs and part of Doon Doon (Hema Maps, 1997). The bioregion is within the ATSIC regions of Katherine and Kununurra and is managed by the Garrak Jarru and Wunan regional councils respectively (McLennan, 1997). For more information on the Aboriginal people of this region refer to Horton, (1994) and the relevant websites in the reference list.
Tourism is a major industry in the area focusing on natural features including the distinctive features of Purnululu (Bungle Bungle) National Park.
Mining is the largest contributor to the economy, particularly the Argyle diamond mine. This mine makes up most of the $631 million that is generated each year from mining across the Kimberley.
Resources, References & Contacts
Publications
Connors G., Oliver B., & Woinarski, J. 1996, Bioregions in the Northern Territory: Conservation Values, Reservations Status and Information Gaps. Final report to ANCA National Reserves System Cooperative Program (Project N607), Parks and Wildlife Commission of the Northern Territory, Palmerston, Northern Territory. (www.nt.gov.au/paw/fauna/bau/intro.htm.)
Hema Maps 1997, Australia Touring Atlas, Fergies Colour Printers, Brisbane, Queensland.
Horton, D. R. 1994, The Encyclopaedia of Aboriginal Australia, Aboriginal Studies Press for the Australian Institute of Aboriginal and Torres Strait Islander Studies, Canberra, ACT.
Kerle, J.A. 1996, Bioregions of the Northern Territory. Draft report Conservation Commission of Northern Territory, Palmerston, Northern Territory.
McLennan. W. 1997, 1994 National Aboriginal and Torres Strait Islander Survey: Social Atlas, Australian Bureau of Statistics, Canberra, ACT.
Morton, S.R., Short, J., & Barker, R.D. with an Appendix by Griffin, G.F., & Pearce, G. 1995, Refugia for Biological Diversity in Arid and Semi-arid Australia, Department of the Environment, Sport and Territories, Canberra, ACT.
Thackway, R. & Cresswell I.D. 1995, An Interim Biogeographical Regionalisation for Australia: a Framework for Setting Priorities in the National Reserves System Cooperative Program, Australian Nature Conservation Agency, Canberra.
Woinarski J., Fensham, R., Whitehead, P. & Fisher, A., with map production by Verhagen, C. in prep., Biodiversity in the Australian Rangelands: a Review of Changes in Status and Threatening Processes. Draft report prepared as a resource document for Project 3: Developing an Adaptive Framework for Monitoring Biodiversity in Australia's Rangelands, of the National Land and Water Resources Audit, Theme 4 (Rangelands monitoring) by the Tropical Savannas Cooperative Research Centre, Darwin, Northern Territory.
Aboriginal languages of Australia
Aboriginal Studies WWW Virtual Library
http://www.ciolek.com/WWWVL-Aboriginal.html
Australian Torres Strait Islanders Commission (ATSIC)
www.atsic.org.au/about_atsic/board_regional_councillors/regional_information.htm
Australian Geological Survey Organisation, Geology of Australia
www.agso.gov.au/map/
Bureau of Meteorology, Climate averages
http://www.bom.gov.au/climate/map/climate_avgs/a14ga.shtml
http://www.bom.gov.au/climate/map/climate_avgs/a14f.shtml
Bureau of Meteorology, Temperature and Rainfall graphs
www.bom.gov.au/climate/forms/map_forms/new_imagemaps/nt_name.html
Bureau of Rural Sciences, Digital Atlas of Australian Soils
www.brs.gov.au/data/datasets/atlas/index.html
Charles Sturt University: Guide to Australia - NT
http://www.csu.edu.au/australia/nt.html
Connors G., Oliver B., & Woinarski, J. 1996, Bioregions in the Northern Territory: Conservation Values, Reservations Status and Information Gaps. Final report to ANCA National Reserves System Cooperative Program (Project N607), Parks and Wildlife Commission of the Northern Territory, Palmerston, Northern Territory. (www.nt.gov.au/paw/fauna/bau/intro.htm.)
Department of Primary Industries and Fisheries, Rangelands of the Northern Territory
www.nt.gov.au/dpif/rangelands/rl_index.shtml
Environment Australia, Normalized Difference Vegetation Index information including bioregional information
www.ea.gov.au/land/monitoring
Kimberley Development Commission
www.kimberley.wa.gov.au/economy.htm
Northern Lands Council
www.nlc.org.au
Northern Territory Department of Lands, Planning and Environment
www.lpe.nt.gov.au
Northern Territory Geological Survey
www.dme.nt.gov.au/ntgs/ntgs/geo_overview/geo_over.html
Northern Territory Government Tourism www.nt.gov.au/ntg_internet/profile/regions_alice_springs.shtml
and
nttc.com.au/
Tropical Savanna Co-operative Research Centre
www.savanna.ntu.edu.au/information/savannaexplorer.html
Link to the Map Maker to make a map using this information.
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