Biodiversity Assessment - Great Sandy Desert
Great Sandy Desert
Introduction
The Great Sandy Desert comprises the McLarty (GSD1) and Mackay (GSD2) subregions, and is mainly a tree steppe in the north grading to shrub steppe in south. The is dominated by Quaternary red longitudinal sand dune fields overlying Jurassic and Cretaceous sandstones of the Canning and Armadeus Basins. Vegetation comprises open hummock grassland of Triodia pungens and Plectrachne schinzii with scattered trees of Owenia reticulata and Bloodwoods, and shrubs of Acacia spp, Grevillea wickhamii and G. refracta. Casuarina decaisneana (Desert Oak) occurs in the far east of the region. Gently undulating lateritised uplands support shrub steppe such as Acacia pachycarpa over Triodia pungens hummock grass. Calcrete and evaporite surfaces are associated with occluded palaeo-drainage systems that traverse the desert and these include extensive salt lake chains with samphire low shrublands, and Melaleuca glomerata - M. lasiandra shrublands. Monsoonal influences are apparent in GSD1, which includes gravely surfaces of Anketell Ridge and dunefields with red-brown sands of finer texture than further south supporting Owenia reticulata savannas that have a greater proportion of bunch grasses. Arid tropical climate with summer rain.
Summary of overall condition and trend
Both subregions in the Great Sandy Desert are continental landscape stress class 5 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed), which is not high compared to other bioregions. However, historical information on the region's biota is scant, and the affects of fire and exotic herbivores (camels and rabbits) and predators (foxes and cats) on productivity and biomass of mammal and vegetation structure are overt. Condition therefor is unknown, but the trend is considered to be declining. Herbivores (feral and stock) have visibly degraded wetlands.
Summary of priority management/consevation priorities
Land acquisition and management issuses are overshadowed by Native Title legislation and partnership arrangements with Aborigional communities. Quite a large off-park conservation effort is needed to preserve biodiversity, but examples of vegetation associations that are subject to threatening processes also need to be reserved. Reducing the effects of inappropriate fire regimes is a priority. The primary constraint on effective land management is the absence of data on the composition and status of most of the region's biota.
Natural values
Dominant landuses in the subregion are: unallocated Crown land, nature conservation, Aboriginal lands, mining lands and urbans areas. The region also contains a number of rare features such as Mandora Marsh, Dragon Tree Soak, Salt Creek (inland mangroves), Rudall River, as well as various soaks and rockholes that are significant local sources of water and serve as seasonal refugia. Endemic troglobitic faunas are almost certainly associated with calcrete systems along palaeo-drainage lines. The bioregion's arid ecosystems are rich in reptiles, particularly in species of Ctenotus and Lerista.
Click here to link to a table of natural values within each subregion
Wetlands
There are 3 wetlands of national importance: Dragon Tree Soak, Mandora Salt Marsh and Lake Dora-Rudall River. Their condition is currently fair to good, though all wetlands areas are declining. Threatening processes are: damage and grazing pressure by feral animals (camels), changed fire regimes and exotic weeds (particularly buffel grass). Minor spring wetlands of Percival and other lake systems, soaks that were previously used by Aboriginal people (no longer maintained), salt lakes, and underground aquifers are scattered throughout the region. They are regionally important. In most cases they are the only sources of fresh water for large distances and are therefor vital as refuges as well as for the wetland ecosystems they support. Most surface wetlands are are threatened by camels, in fair condition but declining or declining rapidly. Very little is known of the stygofauna of calcrete aquifers.
Nationally important wetlands
Map: IBRA map showing DIWA locations, towns, subregions, major roads and reserves and most common threatening processes.
Click here to link to a table of Australia's Important Wetlands (Directory of Important Wetlands of Australia): their type, condition, trend and threatening processes within each subregion.
Regionally important wetlands
Click here to link to a table of provisional identification of wetlands of regional significance: their type and special values within each subregion. The reliability of the overall subregional assessment is indicated.
Click here to link to a table of provisional identification of wetlands of regional significance: their condition, trend and threatening processes within each subregion.
Riparian Zones
The Rundall River is the primary riparian area within the bioregion. It is currently in fair to good condition, but declining. Threatening processes are changed fire regimes, weeds (particularly buffel grass), grazing by feral animals (camels) and changed hydrology.
Map: Riparian threatening processes.
Click here to link to a table of riparian zones: their average condition, trend and threatening processes for each subregion. The reliability of this overall assessment is indicated.
Ecosystems at risk
There are no Threatened Ecological Communities listed for the bioregion, however 10 ecosystems are considered to be at risk. All except for one of these ecosystems are relatively small isolated mound springs, wetlands, mangroves, riparian habitats, and salt lakes which are vital to biota in a very dry environment. Other ecosystems facing particular threat are those that are sensitive to changed fire regimes. The trend of all ecosystems is either not known or in decline. Key threatening processes include grazing pressure from stock and feral animals (camels, donkeys, goats), and changed fire regimes.
Map: IBRA map showing frequency of threatening processes for ecosystems.
Click here to link to a table of provisional list of threatened ecosystems in Australia: their broad vegetation type (National Vegetation Information System - Major Vegetation Subgroup), recommended status, current legislative protection as a threatened ecosystem, trend and bioregional distribution. These ecosystems are arranged in the bioregion of their principal occurrence. The reliability of the recommended status is indicated.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their threatening processes.
Click here to link to a table of provisional list of threatened ecosystems in each subregion: their recommended recovery actions
Species at risk
While no plant species have been declared as Critically Endangered, Endangered or Vulnerable under WA State legislation, one mammal (Notoryctes caurinus) and one reptile (Egernia kintorei) are listed as Endangered, and one mammal (Macrotis lagotis) is declared Vulnerable. Many of the desert's original mammals and a bird (Night Parrot) are extinct. In all cases, the trend for species at risk is unknown and the threatening processes include predation by cats and foxes and changed fire regimes.
Map: IBRA map showing frequency of threatening processes for species.
Click here to link to a table of species at risk in each subregion: their status, trend and subregional distribution. The reliability of the assessment of trend is indicated and whether recovery plans have been prepared.
Click here to link to a table of species at risk in each subregion: their threatening processes.
Click here to link to a table of species at risk in each subregion: their status recommended recovery actions.
Birds
This vast bioregion has an avifauna that closely resembles that of other slightly less vast, semi-arid bioregions nearby. More Princess Parrots are likely to live in this bioregion than most others in which it occurs, but otherwise it is undistinguished for limited range, threatened or introduced species. Guild trends it shares with nearby bioregions are increases in ground feeding insectivores, ground nesting birds and freshwater birds, all counter to the national trend, but possibly related to the much higher rainfall.
Status: A typical semi-arid avifauna that fluctuates, primarily, with rainfall.
Rare and threatened: No major populations.
Increasers: None indicative of landscape health.
Indicators: Emu, Australian Bustard, Hooded Robin, Jacky Winter.
Trend: Higher reporting rates of ground feeding insectivores, ground nesting and freshwater birds, probably because wetter in second Atlas period.
Scenario: Possible decline of species affected by changes in fire regime, although most impact may already have occurred.
Actions: Ensure representative areas have an appropriate fire regime to maintain diversity.
Click hereto download a summary report including the physical characteristics of the bioregion, a species list, and summary statistics [Excel file]. The file may open on your screen. To save it to your system 'Save as' under the File menu.
Mammals
Number of species and status
There are 64 mammal species within this bioregion. (The maximum number of species recorded in a bioregion is 86 and the minimum is 25).
Click here to link to a table of number of species in each status class for this bioregion.
Click here to link to a list of mammal species and their status for this bioregion.
Critical weight range
The critical weight range (35 - 5500 g) of mammals is the size range of Australian mammals that have been most affected by environmental changes following European settlement. In this bioregion, the proportion of mammal fauna within the critical weight range is .516. (The maximum proportion of fauna within the critical weight range recorded in a bioregion is 0.632 and the minimum is 0.222).
Faunal Attrition Index
Faunal attrition is a measure of contraction or loss of species richness with a region. A high index value means many species have declined or are extinct in the bioregion. The index can be used to compare the status of mammal fauna to regional attributes such as changes since European settlement and average annual rainfall. The Faunal Attrition Index for mammals in this bioregion is .38. (The maximum faunal attrition index value recorded in a bioregion is 0.66 and the minimum is 0).
Click here to link to a table of Faunal Attrition Index for groups of mammals shows the contributions of each group to overall patterns of faunal decline.
Faunal Contraction Index
A range contraction index is a measure of the extent to which the range inhabited by a particular species has contracted. A high index value means that many of the species comprising the region's original mammal fauna have contracted from a high proportion of the regions they originally occurred in. The faunal contraction index for the mammal fauna in this bioregion is .37. (The maximum faunal contraction index value recorded in a bioregion is 0.51 and the minimum is 0.07).
Faunal Endemism Index
Endemic species are those restricted to certain regions. Regions containing endemic species are considered to have high biodiversity conservation values because opportunities to conserve those species do not exist elsewhere. A high index value means that the species comprising the original mammal fauna typically occurred in few bioregions. The faunal endemism index value for the mammal fauna in this bioregion is .68. (The maximum faunal endemism index value recorded in a bioregion is 0.79 and the minimum is 0.52).
New Endemism Index
Extant (still surviving) species that have undergone major range contractions can be considered 'new endemics'. Bioregions that contain new endemic species are often important refugia for threatened species. The new endemism index for the mammal fauna in this bioregion is .66. (The maximum new endemism index value recorded in a bioregion is 0.93 and the minimum is 0.5).
Table: Translocated Species
There is no data available for this table within the bioregion.
Exotic Mammals
The number of introduced exotic mammal species that occur within this bioregion is 8. (The maximum number of introduced exotic mammal species in a bioregion is 16 and the minimum is 5).
Click here to link to a list of introduced exotic mammal species for this bioregion.
Extinct mammal species
The number of extinct mammal species that previously occurred within this bioregion is 21. (The maximum number of extinct mammal species in a bioregion is 29 and the minimum is 0).
Click here to link to a list of extinct mammal species for this bioregion.
Management responses
Reserve consolidation
There are 20 vegetation types which are not currently reserved within the bioregion and which have a high priority for acquisition. They include, bunch-grass savanna, sedgelands, samphire, Coolbah, Melaleuca spp, shrublands or hummock grasslands including Triodia pungens, T. basedowii, T. intermedia, T. wiseana, T. bitextura, Owenia reticulata, E.brevifolia, E. setosa, E. dicromophloia, Acacia aneura, A. pyrifolia, A. delibrata, A. pachycarpa, Acacia coriacea, Grevillea refracta, Hakea spp, Allocasuarina decaisneana, and Plectrachne schinzii. They include communities on red sand, laterite, alluvial foot-slopes and plains, saltflats, clay plains and claypans, The primary constraint to aquiring these vegetation units into CALM reserves is competing land uses. M many areas are now subject to native title claims.
Major reserves in the region include the northern part of the Rudall River National Park and reserves in the Northern Territory. The Great Sandy Desert bioregion has a ranking priority of 2 for reserve consolidation; both subregions have inadequate and biassed reserve systems. Reserve management within the Western Australian part of the bioregion is ranked as 'poor' as there are no management plans, no onsite staff (even in parks with high tourist visitation and containing Aboriginal communities), no feral animal control programmes, no prescribed burning, stock have uncontrolled access within parks, and the extent of other threatening processes (for example weeds) is yet to be determined.
Click here to link to a table of comprehensiveness, adequacy and representativeness (CAR) of the National Reserve System in terms of ecosystems and area sampled and a ranking of reserve management. The bioregional priority for consolidating the National Reserve System is based on this CAR analysis and threat.
Table: Bioregional and subregional priorities and ecosystem priorities to consolidate the National Reserve System and associated ecosystem constraints.
There is no data available for this table within the bioregion.
Off-park conservation for species and ecosystem recovery
Priority species are critical weight range mammals (especially in the McLarty subregion), granivorous birds, and priority ecosystems include wetlands damaged by feral herbivores and vegetations adversely affected by fire. Little is known of the distribution, status and impact of weed species. Species recovery actions include detailed fire research and a move towards biodiversity-driven fire management strategies, survey of a wide range of species and communities, weed control, and the removal of feral stock from the conservation estate. A number of recovery plans are relevant to species found in the region, including 'The Action Plans' for Australian rodents and for Australian marsupials and monotremes. Links need to be established between Government agencies, Traditional owners and the broader community in order to effectively manage and research the bioregion. The majority of the bioregion requires a large off-park effort, although limited off park measures in areas such as Mandora Marsh would result in significant conservation gains.
Integrated NRM
There are only a few Natural Resource Management actions currently taking place within the WA section of the bioregion: La Grange groundwater management committee established and this may prove to be an important capacity building resource; and some threat abatement planning occurs in the form of pest management. Opportunities for NRM to address biodiversity issues include research on the mechanism and impacts of threatening processes, threat abatement via pest control, improved implementation of existing legislation, improved communication between all stakeholders, acknowledgement of differing land management objectives, development of catchment and regional plans involving all stakeholders, and capability building through Aboriginal communities. Limited financial resources, the low number of people available to implement strategies, recognition that Native Title which will require cooperative work with desert Aboriginal communities, and the need to increase awareness of conservation values throughout the community are major constraints. NRM rank = 2.
Map: IBRA map showing frequency of recovery actions (species).
Map: IBRA map showing frequency of recovery actions (ecosystems).
Map: IBRA map showing existing projects part of NRM.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: existing measures and effectiveness.
Click here to link to a table of contribution of integrated Natural Resource Management to the protection of biodiversity in each subregion: feasible opportunities and comments.
Further Information & Gaps
Data gaps and research priorities
The major research priority is vegetation and ecosystem mapping, including fauna and habitat data, effects of feral animals (particularly camels) on wetland areas, fire ecology, and population trends even for relatively common species (eg, native rodents, dasyurids, spinifex reptile communities, termites, ants, and weeds such as buffel grass).
References
Environment Australia 2000. Revision of the Interim Biogeographic Regionalisation of Australia (IBRA) and the Development of Version 5.1. - Summary Report. Department of Environment and Heritage, Canberra.
A complete list of references is available by clicking here.
Further information
View the Landscape Health in Australia report.
View the Terrestrial Biodiversity Assessment 2002 report.
Download the Terrestrial Biodiversity Assessment 2002 Database - Biodiversity Audit Data Entry System (BADES), and specifications
Click here to link to a table of some major data gaps in each subregion in terms of protecting biodiversity.
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