Landscape Health In Australia

A rapid assessment of the relative condition of Australia's bioregions and subregions
Gethin Morgan
Environment Australia, 2000
ISBN 0 642 37119 9

1. Condition attributes

Current extent of native vegetation

Extent of native vegetation provides a broad surrogate for the spatial extent of ecological disruption within a subregion and is based on State vegetation coverages. Currency of these coverages varies between 1986 and 2000; scale varies between 1:250000 and 1:100000. Extensive broadscale clearing since these coverages were prepared is largely limited to Queensland, New South Wales and Tasmania, and the current extent of native vegetation in these States can be assumed to be overestimates.

Extensive clearing is mainly limited to the intensive use zone, with any clearing in the extensive use zone restricted to clearing for infrastructure or for small areas of irrigated crops (Figures 2, 3). Although some broader scale clearing is occurring in parts of the extensive use zone notably in the Darwin Coastal and Daly Basin subregions of the Northern Territory, and the Victoria Bonaparte (1) subregion in Western Australia, the extent of clearing remains less than 10% in all extensive use zone subregions.

Figure 2: Current extent of native vegetation in the intensive use zone

97 intensive use zone subregions (53%) have less than 50% of their native vegetation remaining.
57 intensive use zone subregions (31%) have less than 30% of their native vegetation remaining.
12 intensive use zone subregions (7%) have less than 10% remaining.

The relatively high number of subregions with less than 30% of their native vegetation remaining is of concern. These subregions are distributed around the major cropping and developed pasture regions of Australia, with the most extensively cleared subregions in south-east South Australia, western Victoria and the southern part of the Brigalow Belt South bioregion in Queensland and south-west Western Australia.

40 subregions (22%) have 30 - 50% of their natural vegetation remaining. Clearing is continuing in most of these subregions. A particular concern is that these subregions form the habitat matrix within which the subregions with less than 30% of their native vegetation remaining are distributed.

Figure 3: Current extent of native vegetation by subregion

Degree of connectivity in native vegetation

All the subregions in the extensive use zone have little or no broad acre clearing and connectivity between native vegetation types is high. This attribute therefore only applies to the intensive use zone, where clearing of timbered landscapes and cultivation of grasslands has fragmented the natural patterns of the landscape and led to a reduction in the connectivity of native vegetation. Decreasing connectivity (increasing fragmentation) across a landscape leads to a general decline in biodiversity, particularly of the less mobile vertebrates with more complex habitat or large home area requirements.

Subregions were allocated to one of five connectivity classes, based on a visual analysis of the State vegetation maps. These maps range in currency between 1986 and 2000. Connectivity classes range from those with little connectivity to those that are totally unmodified by major structural change (Figures 4, 5, 6).

88 subregions (48%) fall into the first two classes where connectivity between remaining native vegetation has broken down, except for along major natural features (e.g. mountain ranges). This has occurred mainly in the cropping and intensive grazing areas (e.g. south-west Western Australia, and eastern Australia).
49 subregions (27%) are in the early stages of fragmentation and contain some isolated remnants. These subregions are often adjacent to the most fragmented subregions and in many cases are subject to continuing clearing.
49 subregions have little or no clearing. These subregions either have most of their remaining native vegetation in conservative tenures, are too rugged for further extensive clearing, or, in the case of western and northern Queensland, are the more marginal lands of the intensive use zone.

Figure 4: Diagrammatic representation of connectivity in native vegetation classes in the intensive use zone.

Figure 5: Degree of connectivity in native vegetation in intensive use zone.

Figure 6: Degree of connectivity in native vegetation in the intensive land use zone.

Protection of native vegetation

Conservation reserves

Protection and conservation of representative areas of the natural environment is a fundamental part of sustainable land use in each subregion. In the absence of detailed ecosystem mapping, the percentage of a subregion in protected areas broadly indicates the extent to which a comprehensive, adequate and representative reserve system has been established (Figures 7, 8).

The 1999 Collaborative Australian and Protected Area Database (Environment Australia 2000b) indicates that protected areas are distributed evenly between but not within the intensive and extensive use zones.

71 subregions (20%) of the 354 subregions have no protected areas.
173 subregions (49%) have less than 2% of their area protected.

A target of 15% of each vegetation type was accepted as part of the Regional Forest Agreement process as the target for protection in forested areas (JANIS 1996). A comparable figure may be appropriate for other subregions. Only 18% of the subregions meet this target. Half of these are more than 30% reserved for nature conservation, including the Australian Alps, South West Tasmania and Lake Eyre.

Figure 7: Percentage of subregion in conservation reserves across Australia

Figure 8: Percentage of subregion in conservation reserves

Native vegetation outside conservation reserves

Extensive clearing has often greatly reduced the options for nature conservation in the intensive use zone. The percentage of native vegetation remaining outside protected areas is an indication of opportunities available to increase representation of poorly protected subregions (Figures 9, 10).

158 (87%) of the subregions in the intensive use zone have more than 70% of remaining vegetation outside conservation reserves. Eighty-one of these subregions have less than 2% of their total area protected; 131 have less than 10% protected. Significant reserve consolidation options remain in any highly stressed subregion.

Figure 9: Percentage of native vegetation outside conservation reserves in the intensive use zone.

Figure 10: Percentage of native vegetation outside conservation reserves in the intensive use zone.

Condition of native vegetation

Information available on the condition of vegetation across Australia is limited. Other Audit initiatives are specifying condition indicators for Australia's rangelands. No national or State-wide data sets exist. Some States and the Northern Territory measure soil or pasture condition in more arid areas. The data is of varying currency and methodology. Surrogates have been used to infer relative condition from the likely intensity of past and present land uses.

Impact from total grazing pressuresextensive use zone

'Biophysical naturalness'an attribute of the national data set compiled for the National Wilderness Inventory (Lesslie & Maslen 1995)incorporates tenure, rangeland type, and distance to (semi-) permanent water to provide a relative measure of the intensity and consequent impacts of total grazing pressure on biodiversity (Landsberg et al. 1999). Lesslie and Maslen's five classes were reduced to three, and the extent of the least disturbed class was determined for each subregion. This class included areas where at most only marginal or irregular grazing occurred (Figures 11, 12).

96 subregions (56%) have 50% or more of their area in the 'least impact total grazing pressures' class. These are concentrated around the far north of the continent, the central western deserts and Nullabor. The subregions with the greatest grazing intensity are in the Great Artesian Basin, central west Western Australia and the Barkley Tableland.

Figure 11: Percentage of subregion in the 'least impact from total grazing pressures' class in the extensive use zone.

Figure 12: Percentage of subregion in the 'least impact from total grazing pressures' class in the extensive use zone.

Native vegetation in land tenures associated with less intensive land use practices

Land tenure is another indicator of the likely impact of past and present land uses. Tenures associated with conservative land use practices include conservation reserves, World Heritage areas, vacant crown lands, crown reserves, aboriginal reserves, or armed forces reserves. Lands within such tenures have historically been managed less intensively (or 'conservatively'). Past uses have mainly been restricted to irregular grazing or a single episode of selective logging, and the impacts of these uses are relatively small compared to the more intensively managed grazing lands or native forests.

Land tenure is the most easily collated indicator of intensity of land use in the intensive use zone. Conservative tenures were identified across Australia using the Collaborative Australian Protected Area database (Environment Australia 2000b) and National Land Use mapping (Bureau of Rural Sciences 1999) (Figures 13, 14).

In the intensive use zone only 19 (10%) of the subregions have greater than 50% of their remnant vegetation in land tenures associated with conservative land uses. They include the New South Wales (and Australian Capital Territory) Alps and Wilsons Promontory, where most of the subregion is reserved as national park. Ninety subregions (49%) have less than 10% of their area in conservative tenures. The subregions in the intensive use zone with the least native vegetation in land tenures associated with conservative land uses are in the Great Artesian Basin, sub-coastal Queensland and the western slopes of New South Wales.
In the extensive use zone only 17 (10%) of the subregions have greater than 50% of their remnant vegetation in conservative land uses, including Lake Eyre and the Little Sandy Desert. One hundred and ten subregions (64%) have less than 10% of their area in conservative tenures. The subregions in the extensive use zone with the least native vegetation in conservative tenures are in the Great Artesian Basin and across central northern Australia.

Figure 13: Percentage of native vegetation in land tenures associated with conservative land use practices.

Figure 14: Percentage of native vegetation in land tenures associated with conservative land use practices.

Extent of changed soil condition

With the exception of dryland salinity, little national data was available on soil condition at the time of this assessment.

Extent of dryland salinity risk or hazard

Assessments undertaken by the States and Territories for the Audit (NLWRA 2000) provide the first national coverage of the extent of dryland salinity. In Western Australia, South Australia, Victoria and New South Wales, this mapping shows the incidence of high water tables and associated high dryland salinity risk, while in Queensland, the Northern Territory and Tasmania, the interpretation of dryland salinity hazard is mainly based on geology, soils and landform. The national coverage was derived by using scaling factors accounting for the different methods used by the States and Territories.

Where subregions cross State or Territory boundaries the data is analysed and presented for each jurisdiction. The number of reporting polygons for this attribute is therefore 206.

Percentage of subregion with high dryland salinity risk or hazard in the intensive use zone

The main areas of high salinity risk or hazard are in southern temperate Australia with the worst affected subregions in south west Western Australia, south east South Australia, and central to western Victoria. Subregions with smaller areas of high salinity risk or hazard also occur within the eastern states including the Lower Slopes subregion and Sydney Basin bioregion in New South Wales and coastal and inland cropping subregions of Queensland (Figures 15, 16).

10 subregions (4.9%) have a high dryland salinity risk or hazard over more than 10% of their area. These are mainly in south-west Western Australia, where most subregions fall into these two highest categories.
Dandarragan Plateau north of Perth is the worst affected subregion and has high dryland salinity risk over 41% of its area. It is the only subregion nationally in the >30% affected class.
Four subregions in south-west Western Australia have a high dryland salinity risk or hazard over more than 20% of their area. These are the northern part of the Avon Wheatbelt, the Western Mallee, Perth, and Fitzgerald.

Other subregions with significant areas of high dryland salinity risk or hazard are the seaward margins of the Murray Basin in South Australia, including all of the subregions of the Naracoorte Coastal Plain bioregion (Tintinara is the worst affected by rising groundwater), and the Central Uplands and Dundas Tablelands subregion of the Victorian Midlands bioregion (the Dundas Tablelands being the worst affected).

Figure 15: Percentage of subregion with high dryland salinity risk or hazard in the intensive use zone.

Figure 16: Percentage of subregion with high dryland salinity risk or hazard in the intensive use zone.

Percentage of native vegetation in subregion with high dryland salinity risk or hazard in the intensive use zone

Areas of dryland salinity hazard or risk have also been intersected with native vegetation coverages to determine the amount of native vegetation currently within areas at high risk or hazard from dryland salinity (Figures 17, 18).

Dandarragan Plateau subregion north of Perth has the greatest proportion of native vegetation threatened by dryland salinity, with almost 38% in high risk areas. The Murray River Scroll Belt in Victoria is the next most threatened, with over 20% of native vegetation in high dryland salinity risk areas. Seven other subregions have more than 10% of native vegetation threatened, including five in Western Australiathe two subregions of the Avon Wheatbelt, the Western Mallee, Fitzgerald, Warren, on the far south-west coast, and Bridgewater and Tintinara subregions of the Naracoorte Coastal Plain bioregion near the mouth of the Murray River.

Figure 17: Percentage of native vegetation in subregion with highland salinity risk or hazard in the intensive use zone.

Figure 18: Percentage of native vegetation in subregion with highland salinity risk or hazard in the intensive use zone.

Degree of changed hydrological conditions.

This assessment of changed hydrological conditions applies only to the terrestrial component of the subregion and does not include aquatic environments, although the two are clearly connected. The condition of estuaries and riverine environments is the subject of other Audit assessments.

Changed hydrology may result from:

soil degradation caused by over-grazing or cultivation; or
land surface change due to vegetation clearing, land levelling, filling of preferential flow paths, drainage development, contour banking, or the construction of dams or levees.

Land use practices may have a major influence on hydrology (e.g. frequency and method of cultivation, degree of pasture development).

This attribute was assessed within four classes, using expert knowledge, the national land use map (BRS 1999), and the information collated on condition of native vegetation (Figures 19, 20).

The subregions where hydrology has been significantly changed are those dominated by pasture development or regular cultivation.

66 subregions (19%) in the intensive use zone (36% within this zone) have moderate to major changes in hydrology. In southern Australia these include the subregions now subject to extensive dryland salinity.
41 subregions (12%) have a moderate change in hydrology.

Most of these subregions occur in the intensive use zone where hydrological change is mainly due to:

clearing of native vegetation;
extensive disruption of flow paths by land levelling, farm dams or contour banks; or
extensive changes in infiltration due to soil degradation.

In the extensive use zone, hydrological change is largely due to the cumulative impacts of total grazing pressures on soil surfaces and consequently on infiltration and run-off.

117 subregions (68%) have had little to no impact on their hydrology
52 subregions (30%) have minor to moderate changeprimarily occurring in the more intensively grazed subregions on shallow topsoils or soils that are prone to compaction.

Figure 19: Degree of changed hydrological conditions.

Figure 20: Degree of changed hydrological conditions.

Feral plants and animals

Distribution and density of non-indigenous plant species (weeds) of national importance.

The project mainly assessed the 20 weeds of national significance identified as part of the development of the national weeds strategy (ARMCANZ 1999, Thorpe & Lynch 2000). Other introduced plants that were considered by the States and Territories to pose a particularly significant threat to biodiversity were included.

Assessment of distribution and density was mainly based on expert knowledge for each weed species (density was allocated to one of three classes: occasional, common or abundant). Weed distributions and densities were determined at the subregional scale except in Queensland where most weed data is presented at the bioregional scale. Where trend in density is known, it is also summarised in this section.

Weed species can be grouped according to current and potential distribution in Australia:

Wetland weed species

Wetland species are generally able to colonise a wide range of climatic zones. Alligator weed (Alternanthera philoxeroides), cabomba, (Cabomba caroliniana), and salvinia (Salvinia molesta) are able to spread to suitable habitats across most of Australia.

Alligator weed has been eradicated from Tasmania, and is currently restricted to three subregions in New South Wales, and parts of the southern Brigalow Belt and south-east Queensland. Its trend is not known (Figure 21).
Cabomba is scattered between north Queensland and Victoria and is increasing in density and extent (Figure 22).
Salvinia is scattered along the northern Australian coast from the Sydney Basin to south-west Western Australia but is not increasing in density due to control efforts (Figure 23).

Figure 21: Distribution and density of alligator weed.

Figure 22: Distribution and density of cabomba.

Figure 23: Distribution and density of salvinia.

Other wetland species of concern are largely restricted to northern Australia. Hymenachne (Hymenachne amplexicaulis) and para grass (Brachiaria mutica) are both semi aquatic grasses introduced for grazing purposes and have invaded natural wetlands in Western Australia, Queensland and the Northern Territory (Figures 24, 25). Both appear to be increasing in extent. Pond apple (Annona glabra) is a tree that is taking over timbered wetlands on the central and northern coast of Queensland and also appears to be increasing (Figure 26).

Figure 24: Distribution and density of hymenachne.

Figure 25: Distribution and density of para grass.

Figure 26: Distribution and density of pond apple.

Dryland species

Dryland species can be divided into three groups:

species restricted to the north of Australia (usually including the wet/dry tropical areas and in some cases the northern parts of the semi arid or arid interior);
species that are largely restricted to southern Australia; and
species with the potential to colonise suitable habitat across the entire continent.

Predominantly northern species include the aggressive introduced pasture species buffel grass (mainly Cenchrus ciliaris), gamba grass (Andropogon gayanus) and mission grass (Pennisetum polystachion) (Figures 27, 28, 29). All are increasing rapidly in extent and density, although gamba grass and mission grass are currently restricted to the north of the Northern Territory. Buffel grass is becoming increasingly extensive and increasing in density across the drier and sandier parts of northern and central Australia.

Figure 27: Distribution and density of buffel grass.

Figure 28: Distribution and density of gamba grass.

Figure 29: Distribution and density of mission grass.

Woody northern species include athel pine (Tamarix aphylla), mesquite (Prosopis spp.), mimosa (Mimosa pigra), parkinsonia (Parkinsonia aculeata), prickly acacia (Acacia nilotica ssp. indica), and rubber vine (Cryptostegia grandiflora) (Figures 30, 31, 32, 33, 34). Athel pine is restricted to small areas of the Northern Territory, central western New South Wales and South Australia, where it is increasing, and Western Australia, where it is stable. Mimosa is restricted to the northern part of the Northern Territory where it is increasing in density following a reduction in control activities. The remaining species are scattered across northern Australia and are generally increasing in extent and density.

Figure 30: Distribution and density of athel pine.

Figure 31: Distribution and density of mesquite.

Figure 32: Distribution and density of parkinsonia.

Figure 33: Distribution and density of prickly acacia.

Figure 34: Distribution and density of rubber vine.

Southern weed species of concern are mainly woody, although they also include a number of herbaceous plants. Herbaceous species include bridal creeper (Asparagus asparagoides), Chilean needle grass (Nassella neesiana), serrated tussock (Nassella trichotoma), and wards weed (Carrichtena annua).

Bridal creeper is the most widespread and aggressive, invading remnant bushland throughout south-west Western Australia, and the more developed parts of South Australia, Victoria, New South Wales and Tasmania (Figure 35).
Serrated tussock and Chilean needle grass are restricted to South Australia, Victoria, New South Wales and Tasmania, and are increasing in extent and density (Figures 36, 37).
Wards weed is restricted to the drier parts of southern Western Australia, southern South Australia, and the western parts of New South Wales and Victoria, where it dominates many areas and is spreading rapidly (Figure 38).

Figure 35: Distribution and density of bridal creeper.

Figure 36: Distribution and density of Chilean needle grass

Figure 37: Distribution and density of serrated tussock.

Figure 38: Distribution and density of Wards weed.

Woody southern species of concern include bitou bush/boneseed (Chrysanthemoides monilifera), blackberry (Rubus fruticosus agg.), gorse (Ulex europaeus), willows (Salix spp. except S. babylonica, S. X calodendron and S. X reichardtiji), boxthorn (Lycium ferocissimum), broom (Cytisus spp. and Genista monspessulana), olives (Olea europaea), and radiata pine (Pinus radiata).

Bitou bush/boneseed, blackberry, gorse, boxthorn and the willows are all widespread and increasing in extent and density (Figures 39, 40, 41, 42, 43).

Figure 39: Distribution and density of bitou bush.

Figure 40: Distribution and density of blackberry.

Figure 41: Distribution and density of gorse.

Figure 42: Distribution and density of willows.

Figure 43: Distribution and density of boxthorn.

Broom, olive and radiata pine are most abundant in South Australia, and increasing in extent and density (Figures 44, 45, 46).

Figure 44: Distribution and density of broom.

Figure 45: Distribution and density of olives.

Figure 46: Distribution and density of olives.

Two weeds with the capacity to colonise suitable habitat across much of Australia are lantana (Lantana camara) and parthenium weed (Parthenium hysterophorus).

Lantana occurs in high densities along coastal areas in Queensland and New South Wales, and in lower densities on parts of the Western Australia and Northern Territory coasts (Figure 47). While the trend in Western Australia is unknown, lantana is increasing in extent and density in most other areas.
Parthenium is mainly restricted to central Queensland but is continuing to spread outwards (Figure 48).

Figure 47: Distribution and density of lantana.

Figure 48: Distribution and density of parthenium.

Distribution and density of non-indigenous vertebrate species (feral animals) of national importance.

Feral animals assessed included those for which national threat abatement plans have been producedgoats (Capra hircus), foxes (Vulpes vulpes), cats (Felus catus) and rabbits (Oryctolagus cuniculus) (Environment Australia 1999a, 1999b, 1999c, 1999d). States and Territories also considered pigs (Sus scrofa), swamp buffalo (Bubalus bubalis) and cane toads (Bufo marinus) to pose particularly significant threats to biodiversity and these were also assessed. Information on distribution and density was largely based on expert knowledge, with density being allocated to one of three classesoccasional, common or abundant. Distribution and density were determined at the subregional scale except in Queensland and New South Wales where most data is presented at the bioregional scale. Where trend in density was known, it is also summarised in this section.

Foxes and rabbits have similar extents, occurring across most of southern and central Australia (except Tasmania in the case of foxes) (Figure 49, 50). They occur in higher densities in the south. Populations of both species have declined due to the impacts of calicivirus, and are now thought to be stable or increasing slightly.
Cats occur throughout Australia, with southern populations having decreased due to the reduction in rabbits as a food source following the introduction of the calicivirus. Northern populations are stable (Figure 51).
Goats are widespread in south-eastern Australia, and central-west Western Australia, but absent from northern, central and central-southern Australia (Figure 52). The populations are stable to decreasing except in semi-arid Western Australia where they are increasing.

Figure 49: Distribution and density of foxes.

Figure 50: Distribution and density of rabbits.

Figure 51: Distribution and density of cats.

Figure 52: Distribution and density of goats.

Information on pigs, buffalo and cane toads is at present patchy, with uncertainty on the limits of spread.

Pigs are widespread in northern and eastern Australia, and in south-west Western Australia (Figure 53). Densities are stable to increasing in the south west and north, but the trend is unknown in other parts of the mainland. Pigs are present in Tasmania only on Flinders Island where trapping is holding the population at an equilibrium.
Buffalo are common and increasing in the far north of the Northern Territory, and have spread to the coast of the Gulf of Carpentaria in north-western Queensland (Figure 54).
Cane toads now extend across north-eastern Australia from northern New South Wales almost to Darwin, and are continuing to expand their range (Figure 55). Their south-western distribution is unclear. They are increasing in density around the fringes of their distribution, but populations appear to have stabilised in most other areas.

At-risk ecological communities and threatened species

Ecosystems at risk in the intensive use zone

This attribute was only assessed in the intensive use zone, as the loss of natural landscapes following tree clearing or cultivation is more readily defined than that due to land degradation in the extensive use zone where landscape change is less obvious and usually incremental. 'At risk' ecosystems were defined as those with:

greater than 70% of their original extent cleared or cultivated; and
those that had an original area of less than 10 000 ha and are subject to continuing clearing.

This definition corresponds broadly to the 'endangered and of concern' categories used to define the biodiversity conservation status of regional ecosystems in Queensland. In Queensland 'at-risk' ecosystems also include ecosystems that have been moderately degraded across most of their range (Sattler & Williams 1999).

The proportion of ecosystems at risk in a subregion is an indicator of the heterogeneity of remaining native vegetation. It provides an early warning of landscape decline associated with the selective removal of particular landscape elements (e.g. tree dieback due to sustained defoliation by insects may follow the loss of ecosystems having critical seasonal food resources or other habitat needs of key predators; clearing of ecosystems associated with recharge areas may lead to the loss of associated wetlands to salinity).

Ecosystems have been generally defined at a scale of 1:100000.

Assessment in Western Australia, Victoria, and Queensland, is based on mapping which enabled an accurate assessment of the remaining extent. In Queensland non mapped information on the condition of the remaining vegetation was also used to determine their status (Sattler & Williams 1999).
Assessment in South Australia and Tasmania was based on a combination of ecosystem mapping and expert knowledge.
In New South Wales geomorphological units (Pressey et al. 2000) were used within the subregional framework to provide a surrogate for ecosystems, and their remaining extent was derived from the State remnant vegetation cover.

The percentage of subregional ecosystems at risk in the intensive use zone is illustrated in Figures 56, 57.

12 subregions (7%) have more than 90% of ecosystems at risk. These include the Mount Lofty Ranges in South Australia, the Victorian Midlands and parts of the Southern Brigalow Belt.
27 subregions (15%) have between 70% and 90% of their ecosystems at risk. This includes most of the cropping subregions of southern Australia, parts of the Mulga Lands in Queensland and the Tasmanian Northern Midlands.
56 subregions 32%) have between 50% and 70% of their ecosystems at risk, and clearing is continuing in most of these.
5 subregions (3%) can be considered to have almost all of their ecosystems still covering more than 30% of their original extent, including Wilsons Promontory and the West Coast of Tasmania.

Figure 56: Percentage of subregional ecosystems at risk in the intensive use zone.

Figure 57: Percentage of subregional ecosystems at risk in the intensive use zone.

Threatened species

Threatened species considered in this report are those listed nationally in the Environment Protection and Biodiversity Conservation Act 1999 (Cth). These lists are based on recent sightings provided by the States, and then refined nationally by distribution modelling and expert review. Information is current to 1999. While these lists differ to some extent to those currently under State legislation, the geographic information sets underlying some State lists do not lend themselves readily to analysis using the subregions. State lists also do not necessarily recognise the status of species beyond their jurisdiction.

The absence of a threatened species from a subregion gives no indication of whether it was once present but is now extinct in the subregiona common situation particularly in more arid areas of the continent. The presence of a threatened species in a bioregion gives no indication of the degree of threat it faces, nor does it necessarily imply that the subregion is critical in the national conservation of that species.

Conservation of threatened species requires a detailed understanding of distribution, ecology and threats to survival. Despite these constraints, an assessment of the relative number of threatened species across the landscapes of Australia may provide a focus for more detailed subregional analysis.

Threatened plants

There are strong national differences in the recorded occurrence of threatened plants between the intensive use zone and the extensive use zone (Figures 58, 59, 60):

122 subregions in the intensive use zone (67%) have more than 10 threatened plants species recorded from within them.
10 subregions in the extensive use zone (6%) have more than 10 threatened plants species recorded from within them.
three subregions in the intensive use zone (2%) have no threatened species records.
49 subregions in the extensive use zone (28%) have no threatened species records.

These differences reflect biogeography, habitat and threatening processes. They may also reflect search effort, with much of the more remote areas of Australia known only superficially botanically.

38 subregions (11%) have more than 30 threatened plants recorded within them including most of south-west Western Australia, Victoria, the coast of New South Wales, south-eastern Queensland and the northern part of the Wet Tropics and southern Cape York Peninsula.
Subregions with no records of threatened plant species include the deserts of north and north-western Australia, and associated subtropical pastoral lands. The only subregions in the intensive use zone with no records are Culgoa - Bokhara and Narran - Lightning Ridge in the Darling Riverine Plains, and Warrego River Plains in the Mulga Lands.

Figure 59: Number of threatened plants in the extensive use zone.

Figure 60: Known and predicted occurrences of threatened plants.

Threatened vertebrate animals

This analysis of threatened vertebrates includes freshwater fish, birds, reptiles and mammals (Figures 61, 62, 63). It does not include marine or pelagic animals that spend part of their life cycle on the continent or on nearby islands (discussed under 'threatened marine and pelagic vertebrate animals').

Clear national differences exist in the recorded occurrence of threatened vertebrate species between the intensive use zone and the extensive use zone:

84 subregions in the intensive use zone (46%) have more than 10 threatened animal species recorded from within them.
12 subregions in the extensive use zone (7%) have more than 10 threatened animal species recorded from within them.
No subregions in the intensive use zone have no threatened species records.
Nine subregions in the extensive use zone (5%) have no threatened vertebrate records.

Figure 61: Number of threatened vertebrate animals in the intensive use zone.

These contrasts are less marked than for threatened plants, probably reflecting a greater scientific knowledge of a relatively limited suite of vertebrate animal species.

The greatest number of threatened vertebrates are in the south-east of the continent, with the New South Wales North Coast having the highest number (26 species) and a further seven subregions having 20 or more threatened vertebrate animal species.

In the intensive use zone most of the coastal and sub-coastal subregions of north east Queensland have between 10 and 20 threatened vertebrate animals, as does south-west Western Australia.

no subregions with greater than 20 threatened vertebrate animal species occur in the extensive use zone. The highest numbers (10 - 20 threatened species) are found in south-east Cape York, the Simpson Desert, Tanami Desert, the Great Sandy Desert and the tropical rangelands in the north-west of the continent.

Figure 62: Number of threatened plants in the extensive use zone.

Figure 63: Known and predicted occurrence of threatened vertebrate fauna.

Threatened marine and pelagic vertebrate animals

Threatened marine and pelagic vertebrate animals include those that spend some time of their life cycle on the continent or on nearby islands.

More threatened species are found around the northern coast of Australia between Shark Bay and Fraser Island, in south-west Western Australia, and south-east Victoria. The highest numbers are found along the coastal parts of the Victorian Volcanic Plains and King Island (Figure 64).

Figure 64: Known and predicted occurrence of marine and pelagic threatened vertebrate fauna.

Before you download

Most publications are downloadable as PDF files. Adobe Acrobat Reader is required to view PDF files.

If you are unable to access a publication, please contact us to organise a suitable alternative format.

Key

Links to an another web site
Opens a pop-up window

Australian Natural Resources Atlas

Natural Resource Topics