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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Biodiversity Assessment - Riverina
Riverina
Introduction
The Riverina Bioregion lies in the south west of NSW, extending into central-north Victoria. There are six subregions* in this bioregion; Lachlan (Riv1), Murrumbidgee (RIV2), Murray Fans (RIV3), Victorian Riverina (RIV4), Robinvale Plains (RIV5) and the Murray Scroll Belt (RIV6) subregions. The Riverina covers the alluvial fans of the Lachlan, Murrumbidgee and Murray Rivers west of the Great Dividing Range and extends down the Murray River.
This bioregion is dominated by river channels, floodplains, backplains, swamps, lakes and lunettes that are all of Quaternary age (less than 2 million years old). The region comprises three overlapping alluvial fans centred on the eastern half of the Murray Basin. Features of each fan differ slightly because of differences in discharge of the streams. The Lachlan fan is mainly clay because it is a smaller stream, it does not have competence to carry sand. The other two fans are similar except that the Murray is more confined and has more active anabranch channels where it is forced to flow around the obstacle of the Cadell fault near Echuca. At times of extreme flood flow water from the different streams can cross the fan surfaces and enter channels of another system.
Soils and vegetation reflect past patterns of sedimentation and today's flooding regime. Sandy soils are found in belts following the older stream channels, sometimes with local source bordering dunes adjacent to them. Texture contrast soils, often badly eroded, are found marginal to channels of all ages on former levees and terraces, and the plains are dominated by deposits of heavy, dark coloured clays. Many clay areas have gilgai micro-relief patterns, most crack extensively, and others are more or less permanently wet in swamplands.
Modern river channels support River Red Gum (Eucalyptus camaldulensis) and River Cooba (Acacia stenophylla) communities. Trees on the floodplains are mainly Black Box (Eucalyptus la.giflorens) and on higher, rarely flooded terraces yellow box (Eucalyptus melliodora) is found. Many plains are treeless and carry Oldman Saltbush (Atriplex nummularia), Bladder Saltbush (Atriplex vesicaria) and grasses. A formerly extensive community of myall (Acacia pendula) and old man saltbush on the backplains has almost vanished. Sandy soils on levees, old channels, dunes and lunettes have stands of white cypress pine (Callitris glaucophylla), sometimes with mallee and bluebush (Maireana sp.). Lake beds may be bare or covered by clumped lignum (Muehlenbeckia cunninghamii) with a fringe of black box. Swamps have wide margins of river red gum, black box and depending on water depth, also support common reed (Phragmites australis), cumbungi (Typha sp.), grasses and floating water plants.
As soil and water salinity increase downstream and saline clays become evident on lake floors, salt tolerant species such as samphire (Arthrocnemum sp.) become common.
(* 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
Over 60% of the bioregion has been cleared for agriculture and grazing on native pastures is the dominant landuse in the area. Logging of the extensive River Red Gum forests has been ongoing over the last century. Clearing and fragmentation of habitat and intensive land use are other threats to the landscape. The average landscape health of the bioregion is five. For the Riverina bioregion this means an intermediate ranking where although moderate areas of native vegetation remain, including most of the subregional ecosystems, connectivity in native vegetation is low and relatively little of the native vegetation is conservatively managed.
Summary of conservation priorities
Protection of the extensive riverine corridors in the bioregion should been seen as a priority for the bioregion. In particular the irrigated and intensively used areas of the bioregion need to be reconciled with natural resource management outcomes.
Natural values
Special values of the bioregion include the Mallee remnants, found in places through the bioregion, and providing refuges for mallee-dependent species. Two wetland areas the Booligal Wetlands and the Great Cumbung Swamp both provide a range of habitat areas and act as major drought refuge for waterbirds.
Click here to link to a table of natural values within each subregion
Wetlands
Three types of wetland are found in the Riverina bioregion; delta-like swamplands particularly on the Lachlan, terminal drainage basins and lakes on Willandra Creek and, overflow lakes on the Murray.
There are seventy Wetlands listed in the Directory of Important Wetlands in Australia within this bioregion. Seven in South Australia, fifteen in New South Wales and forty-eight in Victoria. Threatening processes for these wetlands include feral animals and weeds such as carp, foxes, goats, gambusia, Noogoora Burr, and African boxthorn. Water extraction, salinity, grazing pressure and vegetation clearing also present major threats to the wetlands of the bioregion.
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 Riverina bioregion covers the contains the catchments of the Lachlan, Murrumbidgee, Edward, Wakool and Murray Rivers west of the Great Dividing Range and extends down the Murray. The landscapes in the upper parts of these catchments are a series of overlapping alluvial fans, while further downstream a wider floodplain forms with overflow lakes. The condition of the riparian zone is generally fair or declining. Threats that apply across the subregion are river regulation, logging of River red Gum Forests, fragmentation of habitat and grazing. In many places the bioregion the riparian zone contains the least fragmented vegetation and regeneration may be possible through conservative grazing to allow the understorey to recover. The long-term impacts of changed hydrological regimes will be to cause a change in the composition of native vegetation.
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
In NSW there are 20 threatened ecosystems identified and 38 in Victoria
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
The Riverina Bioregion has ninety-two species listed as either endangered or vulnerable. These include ten endangered and twenty vulnerable plant species, three endangered and sixteen vulnerable mammal species, ten endangered and twenty-nine vulnerable bird species, one vulnerable reptile, one endangered frog and two endangered fish species. Broadscale clearing of vegetation, further fragmentation and loss of habitat remain the greatest general threat to these species with grazing pressure, feral animals and changed fire regimes playing a major role in the threats to many of these species.
| State | Commonwealth | |||||
|---|---|---|---|---|---|---|
| Endangered | Vulnerable | Extinct | Endangered | Vulnerable | Extinct | |
| Bird | 10 | 25 | 0 | 3 | 7 | 0 |
| Mammal | 2 | 11 | 0 | 2 | 3 | 2 |
| Plant | 7 | 14 | 0 | 6 | 19 | 0 |
| Amphibian | 1 | 0 | 0 | 0 | 1 | 0 |
| Fish | 0 | 0 | 0 | 2 | 0 | 0 |
| Reptile | 0 | 2 | 0 | 0 | 2 | 0 |
| Total | 20 | 52 | 0 | 13 | 32 | 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 eucalyptus species Eucalyptus oxypoma has been identified as being endemic to the Murray Fans subregion. No information is available at this time on the species condition or trend.
Richness
The Riverina Bioregion has not been identified as having significant species richness of its acacia and eucalypt species.
Birds
The red gum forests snaking across the plains of the Riverina provide essential habitat for many woodland birds, including the Vulnerable Superb Parrot. The plains themselves are key habitat for the Plains-wanderer while the wetlands are thought to be the stronghold of the Australasian Bittern. Between the two Atlas periods, however, there has been massive agricultural development in the bioregion. Birds of the riparian corridors have largely been unaffected, but ground-feeding insectivores and grassland birds have been reported much less frequently, perhaps as a consequence. Freshwater species have been reported as frequently, perhaps because it was wetter, but included very few bitterns. The greater rainfall may also be behind the declines in several taxa that are more commonly associated with the arid zone such as chats, Diamond Dove, Budgerigar and Zebra Finch, but cannot explain the lower reporting rates of other species that once occupied the sparse woodland and mallee away from the rivers.
Status: Distinctive combination of temperate riparian woodland and grassland birds in an environment highly modified by agriculture.
Rare and threatened: Plains Wanderer in grassland, Superb Parrot in forest, and Australasian Bittern in freshwater wetland.
Increasers: Long-billed Corella, Little Corella, Musk Lorikeet, Common Myna.
Indicators: Emu, Australasian Bittern, Australian Bustard, Banded Lapwing, Superb Parrot, Blue Bonnet, Brown Treecreeper, Hooded Robin, Flame Robin, Jacky Winter, Grey-crowned Babbler, Varied Sittella, Crested Shrike-tit, Restless Flycatcher, Diamond Firetail .
Trend: Ground-feeding insectivores and grassland birds reported much less frequently.
Scenario: Continued loss of endemic grassland birds.
Actions: Protect, enhance and link woodland fragments. No grazing in representative areas and the adoption of reduced, conservative grazing rates in key habitat across the bioregion. Maintain an on-going supply of hollows within riparian forests. Protect or rehabilitate catchments of major wetlands retaining values for freshwater birds. See also Action Plan for Australian Birds 2000 Coordinated Conservation Plan: Temperate Woodlands.
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 47 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 .426. (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 .27. (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 .5. (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 10. (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
Reserves are highly fragmented. Threatening processes acting from outside the reserve (edge effects, including pest species, predation, and changes in species composition) have a high impact despite management of the reserve itself. There is little opportunity for consolidation of existing reserves. However the creation of new reserve areas has been given the highest priority as land in the bioregion is threatened by clearing and landuse practises and opportunities should be taken to acquire reserves where possible.
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
Community conservation/landcare networks are reliant on a small group of key people. The further use of incentive mechanisms may be able to be applies for conservation in the bioregion.
Integrated NRM
The Riverina bioregion is a highly productive agricultural area and competing landuse is a constraint to some NRM outcomes. Some large NRM processes have operated in the area without achieving extensive biodiversity outcomes.
Map: IBRA map showing frequency of recovery actions (species).
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 completion of the Ecosystem mapping project (The Interim Listing of NSW Ecosystems) will ultimately identify threatened ecosystems, and assist in identifying recovery actions for the bioregion. For both flora and fauna record current databases have a bias towards roadside and development sites as well as areas here interest groups operate. There are also very few flora records throughout Western NSW. A comprehensive, uniform vegetation layer is also required derived from structural and floristic data needs to be developed for Western NSW (NPWS 1999). Further fauna autecological information and habitat modelling is also required for both flora and fauna. Comprehensive datasets are also needed for land irreplaceability, capability, vulnerability and salinity. As with the rest of NSW there is very little data available to assess the status of riparian vegetation.
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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