Biodiversity Assessment - Naracoorte Coastal Plain
Naracoorte Coastal Plain
Introduction
A broad coastal plain of Tertiary and Quaternary sediments with a regular series of calcareous sand ridges separated by inter-dune swales, closed limestone depressions and young volcanoes at Mount Gambier. Vegetation was dominated by heathy woodlands and mallee shrublands with wet heaths in the inter-dune swales. The bioregion has been extensively cleared for agriculture.
Summary of overall condition and trend
The overall condition of the bioregion is fair and the trend declining, with recovery only possible with significant management intervention over an extended period. Most of the bioregion is used for grazing on cultivated pastures, resulting in the clearance and/or degradation of native vegetation on private land. An extensive drainage system has been constructed to enable previously inundated land to be grazed hence reducing the area of wetlands and wetland dependent vegetation in the bioregion. Dryland salinity is a major concern in the north of the bioregion, resulting in the dieback of native vegetation and pasture, and increasingly saline wetlands.
Habitat fragmentation and degradation are key threatening processes for native plant and animal taxa in the bioregion. Although the broad acre clearing of native vegetation is now regulated by the Native Vegetation Act 1991, some clearance is still allowed under exemptions in the Act (ie for fencelines and fire tracks). Biodiversity declines associated with past clearance are probably still continuing. Feral animals including rabbits, foxes, cats, goats and deer present threats to native plant and animal species through grazing, competition and predation, whilst exotic weed species such as bridal creeper, African boxthorn, radiata pine and Salvation Jane crowd out native plant species.
The bioregion consists of four subregions (Bridgewater - NCP1, Glenelg Plain - NCP2, Lucindale - NCP3 and Tintinara - NCP4) with continental landcape stress classes ranging from 1 to 4 as assessed by the Landscape Health report (1 is most stressed, 6 is least stressed).
Summary of Conservation Priorities
Regulation of grazing densities, promotion of fencing schemes and enforcement of the Native Vegetation Act 1991 are conservation priorities aimed at preventing further fragmentation and degradation of habitat. Additionally the continued control of feral animals and plants is important at both the ecosystem and species level.
The promotion of the Heritage Agreement system to local landowners is also a priority. This NHT funded program provides incentives for landowners to fence and manage native vegetation on their properties.
The Upper South East Dryland Salinity and Flood Management Scheme is intended to reduce the incidence of dryland salinity in the north of the bioregion. A congruent aim of this scheme is to reinstate the natural hydrology and flow regimes of wetlands and revegetate drainage lines. This should be a priority where possible.
Natural values
Due to its variety of habitats, the Naracoorte Coastal Plain supports a highly diverse biota. A number of species are on the western margins of their distribution from the wetter southeast of Australia, the southern extreme for drier mallee vegetation or are unique to the bioregion. Although much of the bioregion has been cleared and wetlands drained to facilitate agriculture, the bioregion retains important examples of freshwater wetlands and associated vegetation communities that provide habitat for nationally and state threatened marsupials, reptiles and birds, including migratory birds listed in JAMBA and CAMBA agreements. The bioregion is also an important over-wintering area for the nationally endangered Neophema chrysogaster (Orange-bellied Parrot), of which less than 200 are known to exist, and contains the only known populations of the nationally vulnerable plant species, Ixodia achillaeoides ssp. arenicola (sand ixodia). Other species of note include Miniopterus schreibersii undescribed sub species (Large Bentwing-Bat) and the endemics Nannoperca obscura (Ewens Pygmy Perch), Caladenia richardsiorum (Little Dip spider-orchid) (also nationally endangered), Eucalyptus splendens ssp. arcana (Carpenters Rocks manna gum) and Prasophyllum litorale (coast leek-orchid).
Click here to link to a table of natural values within each subregion
Wetlands
The Naracoorte Coastal Plain bioregion contains 17 wetlands listed in the Directory of Important Wetlands in Australia.
The coastal salt lakes to the south of the Coorong (Butchers and Salt Lakes, South East Coastal Salt Lakes) contain some of the last remaining significant stands of coastal scrub between the Coorong Lagoon and the township of Robe, as well as some of the few known habitats of the nationally endangered N. chrysogaster (Orange-bellied Parrot).
The inland fresh water wetlands (Bool and Hacks Lagoon, Deadmans Swamp, Honans Scrub, Lake Frome and Mullins Swamp, Marshes Swamp, Naen Naen Swamp and Gum Lagoon) are some of the most important wetland areas remaining in the Naracoorte Coastal Plain, as they are remnant wetlands in an area that has been extensively drained and developed for agricultural use. These wetlands provide important habitat for summer concentrations of the southern Australian population of the Grus rubicunda (Brolga), and are a breeding site for several species of wader and waterbirds.
The spring fed limestone wetlands of Ewens Ponds and Piccaninnie Ponds are unique karst features and are world renowned for cave diving. Piccaninnie Ponds is the only remnant of coastal peat fen reserved in South Australia, and one of the few of its type reserved in Australia. Both these wetlands support several species of threatened plants and animals.
The brackish estuary of the Glenelg River contains the only remaining relatively undisturbed saltmarsh community in western Victoria and is one of the few sites where Sterna albifrons (Little Tern) breed in Victoria.
Almost all wetlands in the Naracoorte Coastal Plan bioregion are in fair or degraded condition. Threats to the wetlands of the bioregion include drainage and development for agriculture, Grazing of riparian vegetation by sheep, cattle and rabbits, uncontrolled visitor access, introduced fish species including Perca fluviatilis (Redfin), Salmo trutta (Brown Trout) and Gambusia holbrooki (Eastern Gambusia).
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
Due to the unique geology of much of the Naracoorte Coastal Plain, few permanent rivers or streams exist. Relict sand dune ridges running parallel to the coast stretch far inland, and prevent the formation of rivers and streams. The only major river in the bioregion is the Glenelg River, which is threatened by grazing by rabbits, cattle and sheep, run off from agriculture and clearance for agriculture.
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
This bioregion contains 15 ecosystems at risk. The most severely degraded ecosystems are herblands, sedgelands and rushlands, tussock grasslands, heath and banksia woodlands and shrublands, mallee eucalyptus low open woodlands, eucalyptus woodlands with grassy understoreys and eucalyptus forests with heathy understoreys. Herblands, sedgelands and rushlands, tussock grasslands and banksia woodlands and shrublands are generally associated with wetland areas, which have been extensively drained to facilitate agriculture and are also subject to increasing salinity and grazing by sheep, cattle and rabbits. Other ecosystems, particularly eucalyptus woodlands with heathy or grassy understoreys, have been extensively cleared and grazed.
All ecosystems are declining, except for Banksia marginata Grassy Low Woodland on sandy loam plains in higher rainfall areas, which is rapidly declining.
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 main threats to plants in the bioregion are the drainage of wetlands, grazing by cattle, sheep, rabbits and goats, the invasion of exotic weeds including Myrsiphyllum asparagoides (bridal creeper), Lycium ferocissimum (African boxthorn) and Pinus radiata (radiata pine) and dryland salinity.
Birds in the bioregion are mainly threatened by habitat fragmentation and degradation and predation by foxes and cats, as are mammals and reptiles. The main threats to fish and amphibians are drainage of wetlands, increasing salinity of water bodies, agricultural chemicals and run off and introduced fish species. There is little information available in regards to the trend and condition of threatened species in this bioregion.
There is a total of 121 threatened species in the Naracoorte Coastal Plain bioregion.
| Taxa Group | Commonwealth listing | State/Territory listing | |||
|---|---|---|---|---|---|
| Endangered | Vulnerable | Endangered | Vulnerable | Total | |
| Plants | 7 | 9 | 11 | 41 | 68 |
| Birds | 3 | 7 | 1 | 26 | 37 |
| Mammals | 1 | 1 | 3 | 2 | 7 |
| Reptiles | 0 | 1 | 2 | 0 | 3 |
| Amphibians | 0 | 1 | 0 | 0 | 1 |
| Fish | 0 | 5 | 0 | 0 | 5 |
| Total | 11 | 24 | 17 | 69 | 121 |
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
The Eucalyptus splendens ssp. arcana (Carpenter Rocks manna gum) is endemic to the Bridgewater subregion. It is presently well conserved in Carpenter Rocks Conservation Park. There are no endemic eucalypts in any of the other subregions, nor are there endemic acacias in any subregions of the Naracoorte Coastal Plain bioregion.
None of the subregions of this bioregion have any been identified as being particularly rich for either of these genera.
Birds
The coastal plains of southeast South Australia have been largely cleared for over a century. Even so, the pockets of vegetation that remain are important for several bird taxa. The fringes of the Coorong provide habitat for a distinct subspecies of Rufous Bristlebird, a limited range species. The Coorong saltmarshes are also important over-wintering habitat for Critically Endangered Orange-bellied Parrot, while further inland, low mallee and heath support small populations of the eastern subspecies of Western Whipbird. The broader landscape, however, has a substantial load of introduced species, which made up 6.5% of all observations. The reporting rate of woodland species and many ground-feeding insectivores declined.
Status: Much altered but still diverse avifauna, though with little endemicity; high exotic bird loading.
Rare and threatened: Red-tailed Black-Cockatoo in stringybark and red gum woodlands, Orange-bellied Parrot on saltmarsh in winter, Rufous Bristlebird in Coorong heaths, Western Whipbird in mallee and heath.
Increasers: Little Corella, Rainbow Lorikeet.
Indicators: Emu, Australasian Bittern, Banded Lapwing, Gang-gang Cockatoo, Rufous Bristlebird, Tawny-crowned Honeyeater, Scarlet Robin, Flame Robin, Jacky Winter, Spotted Quail-thrush, Varied Sittella, Crested Shrike-tit, Restless Flycatcher, Diamond Firetail .
Trend: Declines in reporting rates of woodland birds and ground-feeding insectivores.
Scenario: Continued declines in fragmented habitats; increase in some exotic and more adaptable native species.
Actions: Maximise or increase the size of and integrity of woodland fragments. Provide connectivity between seasonally variable resources. Protect or rehabilitate catchments of major wetlands, retaining values for freshwater birds. Implement a fire regime that favours the retention of long unburnt patches of mallee.
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 68 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 .574. (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 .57. (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 .33. (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 .71. (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 .58. (The maximum new endemism index value recorded in a bioregion is 0.93 and the minimum is 0.5).
Click here to link to a list translocated species that has/have been successfully translocated into this bioregion.
Exotic Mammals
The number of introduced exotic mammal species that occur within this bioregion is 10. (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 23. (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 several major reserves within the bioregion:
- Canunda National Park is a linear coastal strip comprising coastal cliffs and beaches backed by stable and unstable dunes in the north, and a mainly unstable coastal dune system in the south. The dunes where vegetated have a diverse range of coastal associations. The park contains a number of soaks and peat swamps.
- Coorong National Park conserves ocean beaches backed by a dune succession on a peninsula formed by the Coorong Lagoon, and fringed by ephemeral salt lakes with samphire and tea tree associations that grade into mallee communities on a limestone landscape.
- Messent Conservation Park is mostly composed of dunes with limestone outcrops supporting a number of mallee communities and infrequent ephemeral swamps. The southern portion of the park contains low lying flats with sedgelands subject to partial flooding during the wet season.
- Gum Lagoon Conservation Park conserves extensive areas of low lying wet heath land in the eastern portion with rising dune country surrounding a chain of lagoons in the western and northern sections of the park.
- Mount Rescue Conservation Park conserves a consolidated aeolian landscape with mallee and heath communities.
Eucalyptus and Sheoak communities with grassy understoreys are insufficiently conserved in the reserve system of the Naracoorte Coastal Plain bioregion, as are Leptospermum lanigerum (silky tea-tree) and Gahnia spp. (cutting grass) ecosystems. These ecosystems are a priority for reserve consolidation, but are constrained by the lack of uncleared or ungrazed examples and the small size of remnants.
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.
Click here to link to a table of bioregional and subregional priorities and ecosystem priorities to consolidate the National Reserve System and associated ecosystem constraints.
Off-park conservation for species and ecosystem recovery
This priority species group for recovery is the threatened species of silky tea-tree closed tall shrublands. It consists of Calamanthus pyrrhopygius (Chestnut-rumped Heathwren), Pachycephala olivacea (Olive Whistler), Egernia coventryi (Swamp Skink) and Antechinus minimus maritimus (Swamp Antechinus).
The major recovery actions for this ecosystem are :-
- encourage the undertaking of Heritage Agreements on land containing the ecosystem;
- block or fill in unnecessary drainage;
- increase awareness of the threats to this ecosystem amongst local landowners;
- establish linking corridors between remnant areas of suitable habitat;
- re-establish areas of habitat where appropriate;
- coordinate district level fox and feral cat control to reduce the level of predation;
- re-establish wetland water quality through appropriate water manipulation; and
- manage salinity in localised areas of suitable habitat.
The main constraints to the implementation of recovery actions include :-
- lack of awareness of significance of ecosystem amongst landowners and the general public;
- the fragmented nature of remaining habitat;
- lack of coordination of feral animal control; and
- inadequate resourcing.
Integrated NRM
Key issues for natural resource management in the Naracoorte Coastal Plain bioregion are :-
- drainage of wetlands and grazing of fringing native vegetation;
- the increasing incidence of dryland salinity;
- feral animal control; and
- continued clearance of habitat on private land.
Current biodiversity initiatives and their outcomes include :-
- Biodiversity Plan for the South East of South Australia. An integrated natural resource management plan covering the Naracoorte Coastal Plain Bioregion with outcomes including increased awareness of biodiversity issues amongst landowners and the general public. An easily accessible reference to be used as the basis for more detailed biodiversity management plans.
- Heritage Agreement and Native Vegetation Council Grant Scheme. A scheme aimed at providing incentives for and assistance to landowners wishing to fence off and manage native vegetation on their properties. Outcomes are long term protection of remnant vegetation on private property, increased awareness of biodiversity issues, additional flora and fauna survey data and public ownership of conservation initiatives.
- Bushcare Management Adviser based in Mount Gambier provides advice and assistance regarding the management of remnant native vegetation, its restoration and re-establishment, and assists in the implementation of community based Bushcare projects, including the provision of workshops.
Where similar circumstances exist, ie privately owned native vegetation adjoining state owned native vegetation, plans of this type enable coordinated, uniform management of important habitat and should be encouraged. Landowners benefit from assistance with weed and feral animal control, whilst biodiversity management can be implemented over large areas. Opportunities also exist for the creation of wildlife corridors between areas native vegetation that are not connected.
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
- Detailed information on the ecological requirements, threats, trend and condition of many of the threatened species, particularly the plants.
- Further wetland inventory is required.
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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