Biodiversity Assessment - Murray Darling Depression
Murray Darling Depression
Introduction
The Murray Darling Depression bioregion lies in the south western corner of NSW and extends into Victoria and South Australia. There are six subregions* in the bioregion; South Olary Plain (MDD1), Murray Mallee (MDD2), Murray Lakes and Coorong (MDD3), Lowan Mallee (MDD4), Wimmera (MDD5) and the Darling Depression (MDD6).
The Murray Basin is a shallow crustal depression filled with marine and terrestrial sediments to a maximum depth of 600 m over the last 50-60 million years, as shallow seas have moved back and forth across the plains. Sandy surface sediments have been extensively reworked into dunes and sandplains. The Darling River and other streams have cut through the sands and constructed numerous overflow lakes such as the Sayers Lake system, and abandoned Pleistocene channel and basins of the Willandra Lakes complex. Saline groundwaters have formed salt basins in many places where the sandplain or dune topography intersects the water table.
Soils and vegetation differ according to the landform. On the dunefields red, brown and yellow calcareous sands occur with more clayey materials in the swales. Typically the dunes support diverse mallee communities with mixed shrubs and porcupine grass (Triodia pungens). Belah (Casuarina pauper and C. cristata), rosewood (Alectryon oleifolius) and variable spear grass (Stipa variabilis) occupy the swales. On sandplains the soil tends to be heavier with brown gradational or texture contrast profiles and mallee is only found on sandy rises. Typical sandplain species include rosewood, white cypress pine (Callitris glaucophylla), narrow-leaved hopbush (Dodonea viscosa), punty bush (Cassia eremophila), belah, copperburrs (Sclerolaena sp.), black bluebush (Maireana pyramidata) and variable spear grass.
Lakes and depressions all have clay floors, and vegetation relates to the presence or absence of salt and gypsum. Infrequently flooded freshwater lakes carry cane grass (Eragrostis australasica), lignum (Muehlenbeckia cunninghamii), and nitre goosefoot (Chenopodium nitrariaceum) with clumps of black box (Eucalyptus la.giflorens) on the margins. More saline lakes have grey cracking clays and carry chenopods. Salt lakes floors carry little vegetation.
Vegetation on lunettes varies. Clean sands often have white cypress pine, brown clayey sands support mallee with porcupine grass, and mixed sand and clay lunettes carry rosewood, belah, western pittosporum (Pittosporum phylliraeoides), narrow-leaf hopbush and bluebush. The largest rocky hills, Maccullochs Range, has mulga (Acacia aneura) dominated vegetation very similar to much of the Cobar Peneplain. Smaller hills have more of a mixture of local sandplain species and distant rocky slope species.
(* Subregional boundaries in NSW are an interim product in draft format for use exclusively in the Audit terrestrial biodiversity assessment.)
Summary of overall condition and trend
The Murray Darling Depression is generally considered in poor condition and deteriorating further as a result of current landuse practices. Factors operating at the sub-regional level are significant in determining the overall rating for the bioregion. Salinity is an increasing problem for land throughout the region and is largely attributable to over clearing and inappropriate landuse practices by landholders. This includes unsustainable water extraction from rivers and inappropriate irrigation regimes for soils that are prone to salinity.
Summary of conservation priorities
Relative to the other bioregions, reservation of land is a medium to high priority for the Murray Darling Depression. While landuse practices in the area constrain conservation actions, landholder stewardship for conservation is a possibility and a high priority to encourage through the use of Voluntary Conservation Agreements, Wildlife Refuges, Covenants and other planning mechanisms in use by various government agencies.
Natural values
Special values of the bioregion include the Darling and Talyawalka Anabranch Lakes wetland complex that provides a wide range of habitats and a major drought refuge for waterbirds. Mallee remnants are also found throughout the bioregion and provide a refuge for mallee-dependent species.
Click here to link to a table of natural values within each subregion
Wetlands
There are five wetlands of national importance in the NSW portion of the bioregion, and four wetlands that have been identified as being of subregional significance. All the wetlands in the bioregion have important values for wildlife but are only fair in condition and often declining.
Eleven wetlands are listed in the Directory of Important Wetlands of Australia (DIWA) in South Australia. One in the South Olary Plain subregion, seven in Murray Mallee, two in Murray Lakes and Coorong and one in the Wimmera subregion. Threats to these wetlands include the presence of the Eastern Gambusia and Carp (Cyprinus carpio), rabbits, foxes, weed infestation and water extraction for irrigation. Victoria has twenty-nine DIWA wetlands listed, seventeen in Murray Mallee, two in Lowan Mallee and ten in Wimmera.
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
Riparian vegetation is thought to be in a fair condition, with a large amount of intervention to return it to its natural state. The trend is static.
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
Eighteen threatened ecosystems were identified in the NSW portion of the Murray Darling Depression bioregion, including two listed threatened ecological communities; Acacia loderi Shrublands and Buloke Woodlands. This means approximately 20% of all ecosystems identified in the NSW portion of the bioregion are threatened.
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
Generally grazing by stock and feral species has been identified as the greatest threat to species in the bioregion. Predation by feral species and loss of remnant habitat are further key threats in the bioregion.
| State | Commonwealth | |||||
|---|---|---|---|---|---|---|
| Endangered | Vulnerable | Extinct | Endangered | Vulnerable | Extinct | |
| Bird | 8 | 23 | 0 | 3 | 7 | 0 |
| Mammal | 4 | 7 | 0 | 0 | 2 | 2 |
| Plant | 13 | 11 | 0 | 3 | 18 | 0 |
| Amphibian | 2 | 0 | 0 | 0 | 1 | 0 |
| Fish | 0 | 0 | 0 | 1 | 0 | 0 |
| Reptile | 0 | 3 | 0 | 0 | 0 | 0 |
| Total | 27 | 44 | 0 | 7 | 28 | 2 |
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.
Eucalypts and Acacias
Endemism
One species of Eucalypt has been identified as endemic to the Murray Darling Depression, Eucalyptus molyneuxii. No acacia species have been identified at this time.
Richness
The Murray Darling Depression Bioregion has not been identified as having significant species richness of its acacia and eucalypt species.
Birds
The Murray Darling depression contains most of the eastern mallee, as well as the wheat fields where mallee used to grow. Three bird species are found mostly or entirely in this bioregion: the Red-lored Whistler, the Mallee Emu-wren and the Black-eared Miner, the latter two being Vulnerable and Endangered respectively. There are also major populations of the Endangered eastern subspecies of Regent Parrot and Western Whipbird, the Endangered Plains Wanderer and the Vulnerable Malleefowl. The extensive agricultural landscapes provide habitat for substantial populations of Eurasian Skylark, European Goldfinch and Common Starling; altogether over 4% of all observations were of exotic species. Overall, the reporting rate of many mallee taxa has remained level or increased between the two Atlas periods, but there are some species, such as Purple-gaped Honeyeater, which were recorded less frequently. This group of birds warrants more detailed attention.
Status: Highly distinct, predominantly mallee avifauna in several large and many small remnant blocks; moderate exotic bird loading.
Rare and threatened: Malleefowl, Black-eared Miner, Mallee Emu-wren, Western Whipbird, Red-lored Whistler mostly in long unburnt mallee, Regent Parrot moving between mallee and riparian red gums.
Increasers: Musk Lorikeet.
Indicators: Emu, Australian Bustard, Banded Lapwing, White-browed Treecreeper, Brown Treecreeper, Purple-gaped Honeyeater, Tawny-crowned Honeyeater, Jacky Winter, Scarlet Robin, Flame Robin, Hooded Robin, Grey-crowned Babbler, Varied Sittella, Crested Shrike-tit, Red-lored Whistler, Restless Flycatcher, Diamond Firetail .
Trend: Decreased reporting rates for grassland, ground-nesting birds, ground-feeding insectivores, but increases in temperate forest and temperate woodland birds.
Scenario: Gradual decline in isolated fragments and extinctions in major mallee blocks during rare, large-scale fires.
Actions: Maintain close control on fire management. Restore, expand and connect mallee fragments. See also Action Plan for Australian Birds 2000 Coordinated Conservation Plan: Eastern Tasmania.
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 51 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 .392. (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 .4. (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 .31. (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 .62. (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 unknown. (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 11. (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 12. (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
Murray Darling Depression is less than 15% reserved under IUCN categories I to VI. Reservation in this bioregion is a moderate priority compared to other bioregions owing to the lower comparative levels of threatening processes. There are few areas remaining in the Murray darling depression that can be reserved under any formal state or federal reserve scheme. Many areas surrounding existing reserves have been highly altered for agriculture and are unlikely to provide for further significant reservation.
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
Catchment Management Blueprints and Regional Vegetation Management Plans play an important part of identifying threats and recovery options for species, species groups and ecosystems.
Integrated NRM
The subregion is dominated by grazing on native pastures. The adoption of duty of care mechanisms and industry initiatives to achieve sustainable grazing regimes is a priority. This requires the establishment of a systematic rangeland monitoring program, the adoption of safe stocking rates and in some instances structural reform to achieve long term restoration of degraded parts of the landscape. Biodiversity requirements need to be clearly articulated as part of such integrated NRM initiatives. Completion of threat abatement plans for feral cat management and fire management are important. Prevention of dry-land salinity is also a high priority
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 spatial datalayer for wildlife refuges is currently being reviewed and the data used in the National Biodiversity Audit is not yet complete therefore, areas and numbers of wildlife refuges stated are possibly less than what actually exists. The ecological detail available for both threatened flora and fauna species was insufficient to provide specific threatening process and recovery actions on a subregional scale. Ecosystem mapping is currently being completed by NPWS as part of the state biodiversity strategy. This data will ultimately identify threatened ecosystems, and assist in identifying recovery actions for these those ecosystems not yet mapped. As such, no comment on ecosystem reservation priority has been made at a bioregion level.
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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