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Native vegetation in Australia

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.

• The hummock grasslands dominate Australia's native vegetation. These occur extensively in Western Australia, the Northern Territory and South Australia, accounting for 23% of the native vegetation.
• Other major vegetation groups covering greater than 500,000 km² each and together covering 39% of Australia are:
  • eucalypt woodlands;
  • acacia forests and woodlands;
  • acacia shrublands;
  • tussock grasslands; and
  • chenopod/samphire shrubs and forblands.
• A number of major vegetation groups that are quite restricted in area, covering less than 70,000 km² each and together covering approximately 2.6% of Australia, include:
  • rainforest and vine thickets;
  • eucalypt tall open forests;
  • eucalypt low open forests;
  • callitris and casuarina forests and woodlands;
  • low closed forests and closed shrublands; and
  • heath.

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

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:

• landscape function;
• remaining habitats;
• opportunities for catchment rehabilitation, whether the issue is catchment hydrology or dryland salinity control;
• priorities for protection and rehabilitation, ensuring remaining native vegetation is representative of Australia's pre-European communities; and
• the contribution of native vegetation to land use planning and sustainable use of Australia's natural resources.

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.

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:

• broadacre clearing for cultivation and grazing on improved pastures;
• forest modification through logging practices, harvesting or disturbing selected species;
• rangeland modification through grazing practices, fire regime changes and introduction of weeds and feral animals, resulting in some species loss and change;
• exotic introductions (e.g. pine forests, weeds, including willow, and feral animals); and
• major alteration/loss of native vegetation and filling of wetlands in urban areas and transport corridors.

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:

• south-west Western Australia;
• southern South Australia;
• western and central Victoria;
• the midlands and northern Tasmania;
• large areas of central and the eastern lowlands of New South Wales;
• northern and eastern Australian Capital Territory;
• central and south-east Queensland; and
• small isolated patches in the Northern Territory.

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).

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:

• road and power infrastructure;
• urban expansion; and
• loss of condition, such as might occur with overgrazing and broad scale clearing for agricultural land.

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

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.

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:

• soil erosion;
• weed infestations;
• dryland salinity; and
• regional fauna extinctions.

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.

Attributes in the assessment included:

• vegetation extent and clearing;
• land use;
• fragmentation of native vegetation;
• hydrological change;
• weeds;
• feral animals; and
• threatened ecosystems and species.

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.

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:

• rainforest and vine thickets;
• eucalypt tall open forests;
• eucalypt open forests;
• eucalypt woodlands;
• eucalypt open woodlands; and
• mallee woodlands and shrublands.

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:

• the representativeness or otherwise of Australia's nature conservation estate and for related interpretations (e.g. setting priorities for retention of native vegetation types);
• opportunities for catchment rehabilitation, whether the issue is catchment hydrology or dryland salinity control;
• the types of vegetation suitable for rehabilitation, restoration and/or revegetation activities in an area; and
• priorities for protection of biodiversity in landscapes under stress.

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:

• impacts of European land use is minimal;
• there is good physical and floristic information (e.g. in Victoria) which can be used for detailed interpolation; and
• the scale of the pre-European mapping and method is similar to that of the current extent mapping (e.g. in Queensland, Victoria, Northern Territory and Western Australia).

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.

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