Biodiversity publications archive

Refugia for biological diversity in arid and semi-arid Australia

Biodiversity Series, Paper No. 4
S.R. Morton, J. Short and R.D. Barker, with an Appendix by G.F. Griffin and G. Pearce
Biodiversity Unit
Department of the Environment, Sport and Territories, 1995

6. Foci of biological diversity in the Northern Territory (continued)

6.4. Mitchell Grass Downs

Area

319,594 km².

Primary land-use

Extensive cattle grazing.

National Parks and Nature Reserves

Connell's Lagoon Stock Reserve (Northern Territory). The Queensland Department of Environment and Heritage is actively seeking to add to its estate in this Region.

Management problems

Land degradation due to over-grazing (Neldner 1991; Wilcox and Cunningham 1994). Over-grazing may particularly affect minor habitats within the Mitchell grass plains, such as bluebush (Chenopodium) swamps (Finlayson et al. in McComb and Lake 1988). Heavy grazing pressure may also be affecting vegetation of Lake Woods and Lake Sylvester, Northern Territory. In addition, invasive plants – particularly Acacia nilotica – are causing substantial problems (Cummings et al. 1993).

Power boats on Longreach Waterhole on Lake Woods (near the town of Elliott, NT) disturb birdlife and cause erosion of banks (Fleming et al. 1983).

ANZECC-listed species

Mammals: Bilbies Macrotis lagotis (V) are present at Lake Woods (Fleming et al. 1983) in the western part of the species' range, and also in Mitchell grass downs at Davenport Downs and Coorabulka Stations in the isolated Queensland population (Southgate 1990).

Birds: The only recent specimen of the night parrot Geopsittacus occidentalis (E) was found on a roadside just north of Boulia (Boles et al. 1994).

Plants: In Queensland, Neldner (1991) recorded Xerothamnella parvifolia, Ptilotus machonochiei, Sclerolaena walkeri, Eremophila tetraptera and Acacia crombiei, and Thomas and McDonald (1989) reported Acacia deuteroneura (all V).

Species that are regionally endemic

The gecko Gehyra minuta, the skink Ctenotus schevilli and the goanna Varanus spenceri (Cogger 1992).

Undescribed species of plants of the genera Callistemon and Mukia appear endemic to the Region (Neldner 1991).

Relict populations

The Queensland population of bilbies is relictual, and requires careful management. Night parrots may have retreated to this Region.

A fish, the red-finned blue-eye Scaturiginichthys vermeilipinnis, is known only from four springs in the Edgbaston spring complex near Aramac, Queensland. It has recently disappeared from two of the springs, apparently because of habitat deterioration due to stock, because of competition from introduced fish Gambusia holbrooki, and perhaps also because of over-collection (Wager and Jackson 1993). Several species of snails are confined to artesian springs in Queensland (Ponder and Clark 1990).

Other significant populations

Significant populations of the yellow chat Ephthianura crocea occur across the Region, particularly in drainage systems in the Northern Territory (Strong and Fleming 1987) and presumably also in Queensland (Blakers et al. 1984). The Australian bustard Ardeotis kori occurs in reasonable numbers (Johnson et al. 1982). The flock bronzewing Phaps histrionica is focussed on the grasslands of this Region.

At Connell's Lagoon Stock Reserve, of 189 plant species recorded, 11 were rare or poorly known (Johnson et al. 1982): Abutilon sp. aff. cunninghamii, Acacia sutherlandii, Chionachne hubbardiana, Echinochloa turnerana, Fimbristylis aff. subaristata, Goodenia sp., Ipomoea sp., Morgania sp., and Portulaca oligosperma.

In Queensland, Thomas and McDonald (1989) and Neldner (1991) reported populations of the rare plants Calotis suffruticosa, Nesaea robertsii, Ptilotus pseudohelipteroides, P. brachyanthus, Euphorbia sarcostemmoides, Daviesia arthropoda, and Acacia spania.

Wetland sites

"The Lake Woods/Longreach Waterhole system is probably the most important inland waterfowl breeding and stop-over locality in the N.T." (Fleming et al. 1983, p. 7). The watercourse contains several large waterholes, some of which are permanent or near-permanent. Lake Woods is the largest inland freshwater lake in the Northern Territory and when flooded provides extensive breeding habitat for certain species of waterfowl, notably magpie geese Anseranas semipalmata. Tens of thousands of birds have been recorded, and nearly 50 species. Significant species known from the Lake include freckled duck Stictonetta naevosa and painted snipe Rostratula benghalensis (Fleming 1993).

The Lake Sylvester system is a seasonal freshwater system fed by tropical streams. It formerly supported the largest area of wetland bluebush Chenopodium auricomum in the Northern Territory, and provides habitat for many waterbirds, sometimes breeding aggregations (Fleming 1993). Numbers of individuals and of species similar to those seen on Lake Woods occur here. It is part of the core habitat of the yellow chat (Strong and Fleming 1987), and also provides water for occasionally phenomenal numbers of flock bronzewings (Fleming 1993).

Refugia

The following are listed as refugia: Lake Woods (see section 12.2), Lake Sylvester (12.3), and Edgbaston Spring (13.1).