Australian Natural Resources Atlas

Natural Resource Topics

Australian Native Vegetation Assessment 2001

Maria Cofinas, Colin Creighton
National Land and Water Resources Audit, 2001
ISBN 0 642 37128 8

Native vegetation in Australia

Mountain ash regrowth (Eucalyptus regnans) forest

Mountain ash regrowth (Eucalyptus regnans) forest

Photo: Michael Ryan

Major vegetation groups and their representation in the Australian landscape

Key findings

Australia's native vegetation types respond to the climatic variation across the continent. The lush tropical rainforests of Queensland's wet tropics are a stark contrast to the hummock grasslands and saltpans of the arid interior. Both are comparatively unique. Both contain a high degree of endemism. Within these climatic extremes lies a broad range of native vegetation types with varying structural (height and density) features from tall forests, to varying closed and open shrublands through to grasslands and forblands, all with their own species assemblages.

The physical landscape-landform, lithology and soils-can either offset or exacerbate climatic influences by providing microenvironments. Landforms such as mountain plateau or gullies may act as climatic refuges allowing more temperate or moisture seeking plants to survive in regions where the climate is otherwise unfavourable. These variations in the physical environment may effect both the structural and floristic composition of plant communities.

Against this palette of variation and diversity, Australia is dominated by a few key plant genera ranging across the broad range of structural vegetation types (Figure 8, Tables 3, 4). Eucalypt communities are widespread and probably the best known genus. Acacias, or wattles cover large areas of the continent, particularly in the low rainfall interior. Hummock grasslands cover a very large proportion of the arid interior.

Figure 8. Major vegetation groups.
Table 3: Area (km²) of major vegetation groups.
Major vegetation group Area
Cleared/modified native vegetation 982,051
Rainforest and vine thickets 30,231
Eucalypt tall open forests 30,129
Eucalypt open forests 240,484
Eucalypt low open forests 12,922
Eucalypt woodlands 693,449
Acacia forests and woodlands 560,649
Callitris forests and woodlands 27,724
Casuarina forests and woodlands 60,848
Melaleuca forests and woodlands 90,513
Other forests and woodlands 119,384
Eucalypt open woodlands 384,310
Tropical eucalypt woodlands/grasslands 254,228
Acacia open woodlands 114,755
Mallee woodlands and shrublands 250,420
Low closed forests and closed shrublands 8,749
Acacia shrublands 654,279
Other shrublands 98,947
Heath 25,861
Tussock grasslands 528,998
Hummock grasslands 1,756,104
Other grasslands, herblands, sedgelands and rushlands 98,523
Chenopod shrubs, samphire shrubs and forblands 552,394
Mangroves, tidal mudflats, samphires and bare areas, claypan, sand, rock, salt lakes, lagoons, lakes - 106,999
Figure 9: Present Major vegetation groups data set classification detail.
Figure 10: Present Major vegetation groups data set scale.

Methods

The decision framework that underpinned compilation of the range of mapped present vegetation data sets into the National Vegetation Information System hierarchy is provided in Appendix 9.

Major vegetation groups that were mapped represent the dominant vegetation occurring in a particular area.

Applications

Appendix 1 presents the area and type of major vegetetation group in each IBRA bioregion. Information collated into a consistent framework can be used to report on Australia's native vegetation using any defined region selected by users.

Information about the extent and type of remaining native vegetation can be integrated with other key data sets to understand:

Limitations

Native regrowth and native plantings have not been specifically mapped or compiled into the National Vegetation Information System. Much of the mapping compiled in the National Vegetation Information System does not include small native vegetation remnants such as road reserves, travelling stock routes and undeveloped lands within farming landscapes.

The National Vegetation Information System data sets have the greatest reliability in mapping the type and extent of the native vegetation. Additional data used to compile an Australia-wide map of major vegetation groups should be considered an interim product and provides broad scale information on native vegetation.

The aggregation into major vegetation groups for summary analysis purposes simplifies the health of data provided for collation under the National Vegetation Information System, with the species and type detail behind all mapping programs provided in lower categories of the hierarchy.

The Guidelines section provides guidelines on the use of the information and Appendix 8 presents information on the sources of data that have been collated into the National Vegetation Information System to represent Australia's native vegetation including the extent, scale and date of collection. Figures 9 and 10 provide information on the location and extent of data sets, their scale and level of classification used to develop the major vegetation groups.

The State and Territory summaries of present vegetation also provide guidelines on the use of the information.

Table 4. Area (km²) of major vegetation groups in each State and Territory.
Major vegetation group Australian Capital Territory New South Wales Northern Territory Queensland South Australia Tasmania Victoria Western Australia
Cleared-modified native vegetation 738 234,527 6,055 304,043 99,473 10,695 142,633 183,887
Rainforest and vine thickets - 2,218 977 19,558 - 7,055 407 16
Eucalypt tall open forests 4 4,405 - 429 - 6,193 16,755 2,343
Eucalypt open forests 937 90,979 58,471 35,150 396 19,212 15,018 20,321
Eucalypt low open forests 49 10,883 70 111 17 106 180 1,506
Eucalypt woodlands 223 68,306 123,078 367,293 16,459 4,609 25,051 88,430
Acacia forests and woodlands - 21,184 29,866 91,534 15,414 28 400 402,223
Callitris forests and woodlands 5 22,132 - 4,134 1,023 1 429 -
Casuarina forests and woodlands 3 40,698 - 1,545 15,261 156 46 3,139
Melaleuca forests and woodlands - 14 19,244 70,014 7 - 45 1,189
Other forests and woodlands - 141 29,497 49,266 34,958 359 2,186 2,977
Eucalypt open woodlands 270 31,245 175,775 134,421 7,652 1,108 1,185 32,654
Tropical eucalypt woodlands/ grasslands - - 107,254 20,653 - - - 126,321
Acacia open woodlands - 138 48,703 36,734 25,414 - - 3,766
Mallee woodlands and shrublands - 33,889 35,450 14 118,531 - 10,843 51,693
Low closed forests and closed shrublands - 3,725 - 445 3 2,168 818 1,590
Acacia shrublands - 77,017 86,035 100,660 151,769 13 14 238,771
Other shrublands 8 5,117 5,294 16,419 25,658 755 3,450 42,246
Heath 9 1,154 - 470 2,680 1,925 1,801 17,822
Tussock grasslands 91 19,318 83,613 282,547 81,187 1,090 614 60,538
Hummock grasslands - 4 490,232 91,809 175,363 - - 998,696
Other grasslands, herblands, sedgelands and rushlands 2 65,761 7,633 4,771 772 10,670 1,059 7,855
Chenopod shrubs, samphire shrubs and forblands - 62,322 33,753 81,944 182,644 28 2,038 189,665
Mangroves, tidal mudflats, samphires and bare areas, claypans, sand, rock, salt lakes, lagoons, lakes 18 5,411 5,410 15,143 28,769 1,880 2,257 48,111
Note: - Indicates that this major vegetation group does not exist in a particular jurisdiction or that the scale and type of mapping compiled has not captured this major vegetation group.
Photo

Photo: Murray-Darling Basin Commission

Change in the extent of native vegetation

Key findings

Thousands of years of traditional Aboriginal land use practices modified Australia's vegetation mainly through the impact of fire. Never has Australia's vegetation experienced such rapid change as since European settlement when large scale clearing and modification has occurred in a relatively short amount of time.

Agricultural, pastoral and urban development has significantly and rapidly changed Australian vegetation and landscapes in the 200 years since European settlement. Impacts have varied with land uses and include:

Broad-scale clearing has accelerated the effects of a number of processes, threatening the long-term viability of our native vegetation (e.g. native vegetation clearing and its replacement with shallow-rooted crops and pastures has contributed to rising water tables, the mobilisation of salt and other hydrological changes). Vegetation clearing has, therefore, led to landscape salinisation, increased sediment, nutrient and salt loads in rivers and streams, loss of habitat and a decline in biodiversity (Williams 2000). Further information on the risk of dryland salinity in Australia can be found in Australia's Dryland Salinity Assessment 2000 (NLWRA 2001a).

Regions most affected by intensive land use development (Table 5 and Figure 11) occur in:

In many of these regions native woody vegetation only survives as isolated trees in paddocks or linear strips (e.g. in windbreaks or along road reserves and stock routes). Native grasslands now grade into exotic sown pastures and/or weed fields. Often the remnants that do occur are on land that is unproductive for agricultural land uses or held by a landholder with a strong commitment to nature conservation.

Management of remnants, while important, is costly. For example, where surrounding land use is 'hostile' (e.g. urban uses as a source of exotic animals, wildfires and weeds) and the habitat patches are small, it will be necessary to actively manage remnants to avoid degradation (Williams 2000).

Figure 11: Extent of native vegetation in Australia

These summary maps and tables provide information on Australia's native vegetation collated within the National Vegetation Information System at July 2001 and with additional mapped informaton where not available from the National Vegetation Information System. The National Vegetation Information System will be updated continuously as vegetation mapping data becomes available from States and Territories.

Table 5: Native vegetation remaining in the intensively (defined as the intensive land use zone [Graetz et al. 1995]) used areas of Australia.
State/Territory Area native vegetation remaining (km²) Percent Remaining
Australian Capital Territory 1,620 69
New South Wales 470,604 67
Northern Territory 186,629 98
Queensland 772,452 72
South Australia 174,966 64
Tasmania 42,520 80
Victoria 84,541 37
Western Australia 234,423 56
Australia (intensive zone) 1,967,755 68

Large areas of intact native vegetation in intensively used regions are either used for forestry and nature conservation or are still within government tenure and unallocated. Few large patches are on private land.

Major threats to remnant vegetation include continued land use development, particularly:

Figures 12 and 13 summarise the percentage of native vegetation remaining by river basin and IBRA subregion. These maps provide useful summaries at a regional level for assessing clearing patterns in Australia, the implications at a river basin scale and the imperatives for remnant management within IBRA subregions. Those river basins and subregions with less than 30% remaining native vegetation are listed in Tables 6 and 7. Twenty-five river basins and 42 IBRA subregions have less than 30% remaining native vegetation.

Appendix 1 presents the area of major vegetation groups and percentage of native vegetation remaining in each IBRA bioregion.

Table 6: River basins with less than 30% remaining native vegetation.
River Basin Area of Native Vegetation (ha) Percent vegetation remaining
Hopkins River 55,928 5.5
Myponga River 1,256 8.2
Avoca River 122,212 8.6
Wakefield River 16,664 8.7
Gawler River 43,668 9.6
Broughton River 167,276 10.3
Onkaparinga River 11,408 12.5
Fleurieu Peninsula 14,928 15.3
Campaspe River 64,492 15.9
Loddon River 252,488 16.1
Torrens River 18,592 16.7
Wimmera - Avon Rivers 528,756 17.4
Maribyrnong River 25,348 17.4
Moorabool River 39,236 17.7
Barwon River 69,616 18.3
Broken River 130,528 18.4
Lake Corangamite 75,736 18.6
Murray-Riverina 287,788 19.1
Bunyip River 79,696 19.7
Portland Coast 77,772 19.8
Millicent Coast 852,044 24.8
Logan-Albert River 111,976 27.1
Blackwood River 611,988 27.1
Moonie River 410,728 28.6
Sydney Coast - Georges River 50,700 29.3
Figure 12: Percentage remaining native vegetation in river basins.

Figure 13: Percentage remaining native vegetation in subregions.

Figure 13: Percentage remaining native vegetation in subregions.
Table 7: Subregions with less than 30% remaining native vegetation.
Sub Region Area of Native Vegetation (ha) Percent vegetation remaining
Victorian Riverina (VR) 91,604 5.1
Mount Gambier 4,832 5.7
Tara Downs 28,388 6.3
Victorian Volcanic Plain (VP) 158,452 7.6
Wimmera (WI) 130,636 7.7
Taroom Downs 52,880 8.2
Avon Wheatbelt P2 254,948 8.5
St Vincent 99,016 9.1
Fleurieu 38,140 10.3
Callide Creek Downs 33,000 11.1
Glenn Innes-Guyra Basalts 32,236 11.6
Dawson River Downs 116,404 11.8
Broughton 123,148 11.9
Dundas Tablelands (DT) 64,420 13.1
Warrnambool Plain (WP) 31,084 13.3
Inverell Basalts 35,068 15.2
Eastern Darling Downs 253,884 15.5
Lucindale 116,064 15.7
Mount Lofty Ranges 47,132 15.7
Moonie R. - Commoron Creek Floodout 137,516 17.1
Southern Yorke 74,916 17.2
Avon Wheatbelt P1 1,129,720 17.3
Deepwater Downs 17,332 17.7
Dulacca Downs 30,612 18.9
Gippsland Plain (GIP) 240,192 20.0
Murray Mallee (MM) 1,125,176 20.4
Armidale Plateau 59,516 20.4
Tintinara 145,140 20.5
Murray Fans 424,348 20.5
Yarrowyck-Kentucky Downs 13,536 20.8
Bridgewater 102,368 22.4
Goldfields (GO) 378,428 22.5
Moreton Basin 180,244 23.0
South Burnett 143,624 25.5
Bundarra Downs 39,464 26.0
Isaac - Comet Downs 702,260 26.0
Moonie - Barwon Interfluve, Collarenebri Interfluve 188,988 26.2
Liverpool Plains 251,124 26.7
Strzelecki Ranges (STZ) 94,668 27.5
Dandarragan Plateau 107,512 28.0
West Balonne Plains 600,240 29.1
Upper Belyando Floodout 128,848 29.4

Methods

The analysis of native vegetation extent is based on the compiled information, as detailed in previous sections.

Limitations

As noted in the previous section, the age of the data sets, their accuracy and the attributes mapped vary.

Woody cover is over-represented in central and western New South Wales and Tasmania due to the age of the data sets available for compilation into the National Vegetation Information System and development of the major vegetation groups. Some regions within these States have experienced much higher levels of clearing than reported. More accurate information for New South Wales and Tasmania is available from those States.

Native and derived grasslands are often not well mapped particularly in mapping coverages from South Australia, New South Wales and the Australian Capital Territory.

Soil erosion, Thrushton NP, Qld

Soil erosion, Thrushton NP, Qld

Photo: Murray Fagg

Landscape Health

An assessment of landscape health (NLWRA 2001c) has used existing information to assess regional differences in landscape health from a natural ecosystems perspective to help guide national initiatives for biodiversity conservation. The information from this study is presented by IBRA subregions.

Broad indications of environmental decline across Australia include:

The accumulating impact of European patterns of land use profoundly affects many Australian landscapes, ecosystems and their biological diversity. An understanding of relativities in landscape health is needed to help guide the urgent and effective responses required to prevent further long-term damage to landscape health, and where necessary, repair the damage already done.

The continent was divided into two discrete zones for analysis and reporting of some attributes: the intensive use zone (extensive clearing has occurred or is occurring) and the extensive use zone (land use predominantly relies on the use of native vegetation). The concept is similar to extensive and intensive land use zones used by Graetz et al. 1995, but unlike these-defined by 1:250,000 scale map sheets-they are defined by grouping subregions. Subregions in the intensive use zone have generally been cleared of more than 10% of the original native vegetation.

Regeneration from clearing, Mount Sheridan Rd, Lake Grace, WA

Regeneration from clearing, Mount Sheridan Rd, Lake Grace, WA

Photo: Murray Fagg

Attributes in the assessment included:

The synthesis and reporting of these attributes was undertaken for both land use zones.

Subregions in the intensive use zone have a history of land use intensification, including clearing, pasture development, cropping and plantation establishment. Assessment of general landscape health in the intensive land use zone must separate the cleared and developed areas from the undeveloped areas. The biodiversity component of landscape health in the intensive use zone relates largely to the extent, distribution and condition of the remaining native vegetation, and these are also reflected in the health of the subregion as a whole.

In the extensive use zone native vegetation is essentially continuous at the scale of this study. Biodiversity and landscape health is inextricably entwined across each subregion.

The particular condition and trend attributes used to provide a synthesis of landscape health were compiled to provide a measure of 'landscape stress' (Figure 14) across Australia by subregion.

Continental landscape stress

The intensive use zone contains the most degraded landscapes-37 subregions in the two highest landscape stress ratings have less than 30% of the original native vegetation extent. Native vegetation occurs mainly as small and isolated fragments, only a small proportion of which are managed conservatively. More than two-thirds of the ecosystems representative of these subregions have less than 30% of original extent remaining and are now at risk of collapse or total loss. No subregions in the extensive use zone could be considered to be in such poor health.

Subregions in the intensive use zone in the third highest landscape stress class usually have 30-50% of original native vegetation extent remaining and although relatively fragmented, it has been cleared in such a way that moderate areas of most of the original ecosystems remain. The overall health of ecosystems in these subregions approximates that of the most heavily used subregions of the extensive use zone (those in the two highest extensive use zone stress classes) where, although there has been little or no clearing, more than 70% of their area typically has a history of relatively high total grazing pressures.

Decreasing grazing pressures in subregions in the remaining extensive use zone stress classes roughly correspond to decreasing land use pressures in the remaining intensive use zone stress classes.

Figure 14: Continental landscape stress.

Figure 14: Continental landscape stress.
Remnant trees and ploughed paddock on basalt, Tas

Remnant trees and ploughed paddock on basalt, Tas

Photo: Michael Ryan

Proportion of remaining native vegetation types in Australia

Key findings

Table 8 and Figure 15 detail the status of the 23 major vegetation groups since European settlement.

At the continental scale, the real differences in patterns of clearing between major vegetation groups are not clear. This is partly because the largest proportion of Australia, the rangelands, remains relatively free of broad-scale clearing.

The key emerging picture at the Australia-wide scale is that the most affected vegetation groups, where approximately 50% of the pre-European extent now remains, are the low closed forests and closed shrublands and the heaths. These two major vegetation groups were already very restricted in their pre-European extent so that further clearing has a major impact on aerial extent.

Major vegetation groups where 60-80% of pre-European extent remains are:

Of these, rainforest and vine thickets and eucalypt tall open forests were very restricted in their pre-European extent.

Table 8: Area of pre-European and present vegetation in Australia (km²).
Major vegetation group Present Pre–European Percent Remaining
Rainforest and vine thickets 30,231 43,493 70
Eucalypt tall open forests 30,129 44,817 67
Eucalypt open forests 240,484 340,968 71
Eucalypt low open forests 12,922 15,066 86
Eucalypt woodlands 693,449 1,012,047 69
Acacia forests and woodlands 560,649 657,582 85
Callitris forests and woodlands 27,724 30,963 90
Casuarina forests and woodlands 60,848 73,356 83
Melaleuca forests and woodlands 90,513 93,501 97
Other forests and woodlands 119,384 125,328 95
Eucalypt open woodlands 384,310 513,943 75
Tropical eucalypt woodland/grasslands 254,228 256,434 99
Acacia open woodlands 114,755 117,993 97
Mallee woodlands and shrublands 250,420 383,399 65
Low closed forests and closed shrublands 8,749 15,864 55
Acacia shrublands 654,279 670,737 98
Other shrublands 98,947 115,824 85
Heath 25,861 47,158 55
Tussock grasslands 528,998 589,212 90
Hummock grasslands 1,756,104 1,756,962 100
Other grasslands, herblands, sedgelands and rushlands 98,523 100,504 98
Chenopod shrubs, samphire shrubs and forblands 552,394 563,389 98
Mangroves, tidal mudflats, samphires and bare areas, claypans, sand, rock, salt lakes, lagoons, lakes 106,999 112,063 96
Note: This table provides a broad analysis of Australia's pre-European and present major vegetation groups based on available data. The methods, limitations and Guidelines section of the report provide a reference to the data used in this analysis.

Methods

This analysis is based on a comparison of the present extent of major vegetation groups and pre-European mapping.

Applications

Analysis at the Australia-wide, State and Territory and regional scales provides information on which to base broad assessments of change in extent and type of vegetation. This is a key input to assessing:

Limitations

Pre-European vegetation and present native vegetation for many States and Territories do not match in mapping method or scale. Development of pre-European vegetation maps in cleared areas of Australia is usually dependent upon coarse or generalised data on landforms and soils sometimes at 1:250,000 or even 1:1,000,000 scale. Reconstructing the natural complexity of vegetation patterns from such broad interpretations is difficult. Earlier vegetation mapping for areas now cleared may similarly be coarse in scale and/or generalised, with little data from systematic field sampling to support the derivation of mapping units and the allocation of individual patches of native vegetation to mapping units.

Pre-European data is more reliable where:

Data variability is greatest in New South Wales, the Australian Capital Territory and South Australia, where the pre-European data does not meet the requirements of the National Vegetation Information System. In Tasmania the pre-European data is not finalised. In these States it is assumed that the present vegetation mapped is an approximate representation of the pre-European vegetation. The Australia wide pre-European major vegetation groups data set is an interim product.

Figure 15: Area km² of pre-European and present major vegetation groups in Australia.

Figure 15: Area km2 of pre-European and present major vegetation groups in Australia.

Case Study: Vegetation Change And Information To Support Regional Vegetation Management

Role

This case study demonstrates the use of the National Vegetation Information System information on major vegetation groups and information hierarchy at Level IV to determine the changes in vegetation type and extent at a subregional level. Detail is also provided on the present land use and land tenure in the region as part of the information set necessary to underpin regional planning and management decisions.

Data sets

The Isaac - Comet Downs subregion has been selected as the subregion to demonstrate this application as it has a complete vegetation data set for both pre-European and present type and extent at 1:100,000 scale. The vegetation data sets are complemented by a complete coverage of land use in the subregion at 1:100,000 scale (Calvert et al. 2000). This congruence in scales of available data facilitates analysis.

Geology and vegetation

Isaac - Comet Downs is an extensive but diverse subregion in tropical western Queensland. It is an undulating subregion dominated by Tertiary and other Cainozoic deposits, with mid-Catena deposits being slightly more prominent. Tableland and dissected remnants of the upper Tertiary surface are widespread, supporting narrow-leaved Eucalyptus crebra woodlands on the earths of undulating plateaus, and bendee (Acacia catenulata) or lancewood (A. shirleyi) on the rocky hills and mesas. The lower parts of the Tertiary surface are dominated by brigalow (A. harpophylla) and Dawson gum (E. cambageana) communities on undulating clay or tenure contrast soils. These communities dominate the subregion. Alluvium is also prominent and the predominantly fine-textured soils of the alluvium carry brigalow or coolibah (E. coolabah) woodlands. Fine-grained Permian sediments are exposed due to long term weathering, giving rise to grasslands, open woodlands and areas of brigalow (Young et al. 1999).

Land use

The dominant land use in the subregion is livestock grazing with smaller areas of dryland agriculture and a large area of irrigated agriculture near Emerald (Figure 16). Two nature conservation areas are present in the subregion, Dipperu and Taunton National Parks (0.7% of the region). One large crown reserve, that is used for grazing and forestry, accounts for 2.8% of the region. The majority of the remnant vegetation is on freehold tenure. Overall the subregion, other than the Crown estate, is a mix in about equal proportions of freehold and leasehold tenure.

Native vegetation and change

Figures 17 and 18 show the pre-European and present vegetation types and extent of the vegetation mapped by major vegetation group. Table 9 presents the area of pre-European and present major vegetation groups.

The total area of the subregion is 27,011 km² with 28% remaining vegetation of the pre-European extent. This diverse subregion had the fourth highest level of clearing between 1997 and 1999 (Sattler 2001).

The remaining native vegetation and areas cleared are presented in Table 10. The most impacted major vegetation groups, with less than 30% of the pre-European vegetation extent remaining, are:

All groups have restricted distributions in the subregion.

Figure 16: 1996/97 land use in the Isaac-Comet Downs subregion.

Figure 16: 1996/97 land use in the Isaac-Comet Downs subregion.

Figure 17: Pre-European vegetation Isaac-Comet Downs subregion.

Figure 17: Pre-European vegetation Isaac-Comet Downs subregion.

Figure 18: Major vegetation groups Isaac-Comet Downs subregion.

Figure 18: Major vegetation groups Isaac-Comet Downs subregion.

Fine scale detail on vegetation change

Because of the richness of the National Vegetation Information System database in this region, this analysis can be repeated at all levels of the hierarchy, providing the finer definition of vegetation types required for the development of management plans. This analysis is presented at Level IV (vegetation subformation) describing the floristic and structural characteristics for the upper- and mid-strata, and structure of the lower vegetation stratum.

Table 11 shows that 17 of the 51 (or 34%) of the subformations have less than 30% remaining native vegetation. These are primarily eucalypt and acacia woodlands with grassy understorey and eucalypt/acacia mixed open forests and low closed forests with shrubs and grassy understorey. Remnant management, connectivity between remnants and minimisation of any further clearing are key management responses for these vegetation types. As to how this is implemented in the subregion, which land areas, what interaction with tenure types is a task for the regional groups, armed with the knowledge that this assessment provides.

At the other end of the perspective, eleven (22%) of the subformations have more than 70% remaining vegetation. These are primarily eucalypt woodlands with acacia shrubs and grassy understorey, being the areas of lower site quality for agricultural and grazing development. Again, armed with this information, regional groups can develop vegetation management strategies.

Table 9: Pre-European and present major vegetation groups in the Isaac - Comet Downs subregion.
Major vegetation groups Pre-European extent Present extent
Area (ha) Percent of total area Area (ha) Percent of total area
Cleared (primarily agricultural, grazing, urban and infrastructure) - - 1 955 790 72.41
Rainforest and vine thickets 34 386 1.27 4 860 0.18
Eucalypt open forests 1 731 0.06 397 0.01
Eucalypt woodlands 715 377 26.48 340 154 12.59
Acacia forests and woodlands 1 470 403 54.44 248 738 9.21
Callitris forests and woodlands 506 0.02 245 0.01
Casuarina forests and woodlands 23 429 0.87 8 651 0.32
Eucalypt open woodlands 380 877 14.10 125 895 4.66
Acacia open woodlands 1 704 0.06 0 0
Other shrublands 2 863 0.11 1 427 0.05
Tussock grasslands 68 541 2.54 12 629 0.47
Other grasslands, herblands, sedgelands and rushlands 1 162 0.04 774 0.03
Bare areas, claypans, sand, rock, salt lakes, lagoons, freshwater lakes (increase in area includes the water storages, supplying water for the high value irrigation development) 100 ~ 0.00 1 518 0.06
Table 10: Changes to major vegetation groups in the Isaac - Comet Downs subregion since from pre-European settlement.
Major vegetation groups Area cleared (ha) Percent of pre-European extent remaining
Rainforest and vine thickets 29 525 14.13
Eucalypt open forests 1 334 22.95
Eucalypt woodlands 375 223 47.54
Acacia forests and woodlands 1 221 665 16.91
Callitris forests and woodlands 260 48.51
Casuarina forests and woodlands 14 779 36.92
Eucalypt open woodlands 254 982 33.05
Acacia open woodlands 1 704 0
Other shrublands 1 436 49.83
Tussock grasslands 55 911 18.42
Other grasslands, herblands, sedgelands and rushlands 388 66.64
Table 11: Vegetation sub-formation in the Isaac - Comet Downs subregion.
Vegetation sub-formation (Level IV) Pre-European area (ha) Present area (ha) Vegetation cleared (ha) Percent of pre-European extent remaining
Acacia low open woodlands/dichanthium tussock grassland 1 704 0 1 704 0
Eucalypt woodlands/coniferous woodlands/mixed unable to determine structural formation 468 0 468 0
Eucalypt woodlands/acacia tall sparse shrubland/grassy tussock grassland 16 1 916 -1 900 100
Coniferous woodlands/coniferous isolated shrubs/grassy tussock grassland 214 10 205 5
Acacia open forests/mixed open shrubland 467 518 45 973 421 545 10
Mixed low closed forests/mixed low woodlands 184 19 165 10
Acacia open forests/mixed tall open shrubland/grassy sparse tussock grassland 833 373 96 682 736 691 12
Mixed low closed forests/mixed tall open shrubland/grassy isolated tussock grasses 34 202 4 841 29 360 14
Eucalypt woodlands/mixed tall open shrubland/grassy open tussock grassland 10 559 1 561 8 998 15
Eucalypt woodlands/mixed tall open tussock grassland 16 611 2 457 14 154 15
Acacia open forests/mixed tall shrubland/grassy sparse tussock grassland 12 940 1 921 11 019 15
Acacia low isolated trees/astrebla and iseilema open tussock grassland 68 541 12 629 55 911 18
Eucalypt open forests/mixed tall open shrubland 1 616 353 1 263 22
Mixed woodlands 5 413 1 387 4 026 26
Eucalypt open woodlands/mixed sparse shrubland/spinifex sparse tussock grassland 147 066 38 275 108 791 26
Eucalypt woodlands/mixed tall isolated shrubs/grassy tussock grassland 14 757 3 876 10 881 26
Eucalypt woodlands/mixed open tussock grassland 7 422 2 067 5 355 28
Eucalypt open woodlands/mixed tall sparse shrublands 19 071 5 674 13 396 30
Eucalypt woodlands/mixed isolated shrubs/grassy open tussock grasslands 39 553 12 696 26 856 32
Eucalypt woodlands/mixed tall sparse shrublands 44 271 14 792 29 479 33
Eucalypt open woodlands/mixed tall sparse shrublands/grassy open tussock grasslands 78 362 28 517 49 845 36
Casuarina open woodlands 23 429 8 651 14 779 37
Eucalypt open woodlands/mixed low isolated shrubs/grassy open tussock grasslands 131 874 50 068 81 805 38
Eucalypt woodlands/mixed low tussock grasslands 123 629 47 204 76 425 38
Eucalypt mallee woodlands/spinifex woodlands 115 45 71 39
Eucalypt woodlands/mixed tall isolated shrubs/grassy open tussock grasslands 2 694 1 064 1 629 40
Melaleuca tall open shrublands 373 166 207 44
Eucalypt woodlands/grassy tussock grasslands 205 217 93 522 111 696 46
Eucalypt woodlands/acacia tall open shrublands/grassy open tussock grasslands 17 254 8 354 8 900 48
Eucalypt woodlands/acacia tall open shrublands 97 006 47 896 49 110 49
Eucalypt woodlands/melaleuca woodlands/mixed sparse rushlands 7 224 3 641 3 583 50
Mixed open shrublands 2 490 1 261 1 229 51
Eucalypt open woodlands 395 229 166 58
Acacia open forests/mixed low woodlands 36 245 21 627 14 618 60
Cyperaceae low open sedgelands 1 162 774 388 67
Eucalypt woodlands/dichanthium tussock grasslands 56 38 19 67
Acacia low woodlands/mixed sparse shrublands/grassy sparse tussock grasslands 30 893 20 943 9 950 68
Acacia woodlands/acacia tall sparse shrublands/grassy sparse tussock grasslands 88 919 61 235 27 684 69
Acacia open forests/mixed tall open shrublands 514 357 157 69
Eucalypt woodlands 69 568 51 290 18 278 74
Eucalypt open woodlands/acacia open shrublands/grassy open tussock grasslands 4 110 3 132 978 76
Mixed woodlands/mixed tall open shrublands 901 708 193 79
Coniferous open forests/acacia sparse shrublands/grassy open tussock grasslands 291 235 56 81
Eucalypt woodlands/chenopod sparse shrublands/grassy open tussock grasslands 46 492 40 006 6 487 86
Eucalypt woodlands/grassy open tussock grasslands 1 635 1 423 212 87
Eucalypt woodlands/mixed shrublands/grassy sparse tussock grasslands 732 654 78 89
Eucalypt woodlands/mixed open cycadland 61 55 6 91
Eucalypt woodlands/acacia low sparse shrublands/grassy tussock grasslands 2 123 1 938 185 91
Eucalypt woodlands/acacia sparse shrublands/grassy open tussock grasslands 1 550 1 447 104 93
Eucalypt woodlands/acacia open shrublands/grassy open tussock grasslands 163 163 0 100
Note: A negative value indicates an increase in extent of vegetation type

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