Australian Terrestrial Biodiversity Assessment 2002
Paul Sattler and Colin Creighton
National Land and Water Resources Audit, 2002
ISBN 0 642 3713
Case Study
Dieri (Simpson-Strezelecki Dunefields 3) Lowest stress class
Sandhill canegrass, Zygochloa paradoxa, on a dune crest in the Simpson Desert.
Photo: P. Canty
The Dieri subregion is dominated by a large expanse of red sand dunes of the southern Simpson and Tirari Deserts, two large ephemeral salt lakes (Lake Eyre North and Lake Eyre South), local concentrations of pans with cracking clay soils in the southern Simpson Desert, and the lower reaches of two of Australia's major inland river systems - Warburton and Cooper Creeks.
Lake Eyre is the terminus for one of the world's largest endoreic drainage basins that occupies approximately 16% of Australia and 35% of South Australia. It is the largest lake in Australia and the fifth largest terminal lake in the world. Although the Dieri subregion is in the driest part of the continent, with an annual rainfall of 100 to 150mm, the lake receives water from the Northern Territory and Queensland where heavy and regular monsoon rains fall.
Condition and trend
The Dieri subregion contains four ecosystems that have been identified as being at risk at the State level. The ecosystems are associated with major arid drainage lines and are:
- Chenopodium auricomum shrubland on cracking clay depressions subject to periodic waterlogging;
- Eucalyptus coolabah ssp. arida woodland on levees and channel banks of regularly inundated floodplains;
- Acacia salicina, Eucalyptus coolabah ssp. arida, +/- Lysiphyllum gilvum woodland of drainage lines and floodplains; and
- Atriplex nummularia ssp. nummularia open shrubland with occasional emergent Eucalyptus camaldulensis var. obtusa or E. coolabah ssp. arida on low sandy rises of floodplains.
Of the six nationally threatened species either occurring, or likely to occur, in the Dieri subregion, three—Dasycercus hillieri (Ampurta), Pseudomys australis (Plains Rat) and Frankenia plicata (sea-heath)—have been recorded within reserves. Insufficient information exists to provide an accurate assessment of the trend and condition of any of these species in this subregion.
Threatening processes
The three nationally threatened mammals of the dune country (Dasycercus hillieri, Pseudomys australis and Notomys fuscus) face common threatening processes such as:
- habitat destruction by introduced herbivores such as camels, horses, donkeys and cattle;
- competition for resources with mainly rabbits and house mice; and
- predation by foxes and cats.
The main threats facing the three State-listed birds of the dune country (Neophema chrysostoma (Bluewinged Parrot), Phaps histrionica (Flock Bronzewing) and Ardeotis australis (Australian Bustard) are predation by foxes and cats and the loss of vegetation associated with rabbit and stock grazing. With large areas of habitat excluded from stock, and rabbit numbers at their lowest in years, the current conditions in the Dieri provide these species with a good opportunity to consolidate existing populations.
The main threatening processes for ecosystems at risk are:
- cattle and feral animal grazing (which has the potential to limit regeneration and establishment of seedlings of both overstorey and the main shrub layer);
- rabbit grazing (by suppressing regeneration of perennials); and
- tourism (camping and vehicle use can contribute to vegetation loss through off-road driving, trampling, firewood collection, soil compaction and accelerated erosion).
Special case
The Banded Stilt (Cladorhynchus leucocephalus) is an endemic Australian wader that inhabits saline wetlands in coastal regions of southern Australia, but will opportunistically fly long distances inland to breed on large ephemeral salt lakes such as Lake Eyre. Such breeding events occur irregularly and only five times in the past 70 years and follow heavy rains that flood these inland lakes.
During the most recent flood event in Lake Eyre in early 2000, water persisted for several months enabling four breeding episodes of Banded Stilts. However, Silver Gulls (Larus novaehollandiae) were responsible for heavy predation on eggs and young, and by early April, no nests remained. In response, the National Parks and Wildlife Service conducted an extensive Gull control program in July. This was spectacularly successful and by late August the total Banded Stilt population on Lake Eyre North was estimated at 100,000 birds. This action has led to the development of a breeding management action plan for Banded Stilt populations in South Australia.
Methods
The approach taken to develop biodiversity strategies in the Dieri subregion involved consideration of the following:
- A comprehensive, adequate and representative reserve assessment. This process identified four ecosystems as being priorities for inclusion in future reserves. It requires:
- the inclusion within the reserve system of the full range of environmental associations described for the subregion;
- inclusion within the reserve system of at least 10% of the whole subregion and of each environmental association it contains; and
- the areas included from each environmental association reasonably reflect the biodiversity of the ecosystems present.
- Identification of candidate areas of these priority ecosystems for possible addition to the existing formal reserve system.
- Identification of species and/or ecosystems suitable for multi-species recovery programs. Two clear groupings were defined - 'species associated with longitudinal dunes and swales' and 'species and ecosystems associated with major arid drainage lines'.
- Development of recovery actions for the most threatened of the above two groups.
- Identification of existing and possible integrated natural resource management actions that maximise conservation of the most threatened species and ecosystems.
Management Responses
Some of the key management responses include:
- maintenance of Bushcare Grants Scheme as an incentive to pastoralists, in particular, a devolved grants scheme for on-ground works to be administered by the South Australian Rangelands Soil Board Executive Committee;
- continued provision of practical information and knowledge to pastoralists;
- ecologically sustainable use of major drainage channels and floodplains;
- provision of a policy framework to underpin pastoral lease development, particularly with respect to the establishment of new water points;
- efficient discharge and distribution of artesian water; and
- monitoring and control of feral animal and pest plant populations.
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