Australian Native Vegetation Assessment 2001
Maria Cofinas, Colin Creighton
National Land and Water Resources Audit, 2001
ISBN 0 642 37128 8
Pre-European vegetation in Australia
Wetlands at Fogg Dam, NT
Photo: Maria Cofinas
Key findings
Australia's vegetation has been in a state of dynamic change throughout geological history, responding to major shifts in environmental conditions associated with continental drift, periods of intense geological activity such as volcanism and climate change during the Quaternary. The dominance of certain morphological features of Australian plants such as sclerophylly, and the success of genera that have developed such water-saving features, underlines the adaption of the Australian flora to increasing aridity.
Structural vegetation types vary across the Australian continent, reflecting climatic and edaphic patterns, with rainfall a key factor limiting distribution (e.g. of certain closed forests or rainforest communities).
Australian vegetation has many unique features:
- many species are endemic to Australia; and
- two large tree and shrub groups-the eucalypts and acacias-dominate. These groups also contain a large number of species, an indication of their diversity and adaptation across the broad range of climatic and edaphic conditions.
The high numbers of vegetation types at the association and sub-association levels (Levels V and VI in the National Vegetation Information System information hierarchy) indicate a high level of diversity in Australia's vegetation. According to our current knowledge, there are more than 3000 vegetation types described across Australia and these have been summarised into 23 major vegetation groups for reporting (Figure 5, Table 2).
- Forests and woodlands covered approximately 50% of the continent across tropical northern Australia, down the higher rainfall eastern side of Australia, Tasmania, to southern South Australia and southern Western Australia. Eucalypt woodlands make up the largest proportion, approximately 13% of Australia.
- Shrubs and heaths covered approximately 11% of the continent. Key distributions of acacia shrublands were in south-western Queensland, central South Australia, southern Northern Territory and on the west coast of Western Australia up the central coast to Broome. The main distribution of heaths was in Western Australia in the Geraldton Hills region.
- Grasslands, chenopods and samphire shrubs covered approximately 40% of the continent across much of the mainland interior and western Tasmania. The hummock grasslands covered 23% of Australia, west of Queensland and New South Wales.
- There was little bare soil apart from the areas that were sparsely vegetated in the semi-arid and arid regions.
- Surface waters, including salt lakes, occupied less than 2% of the continent.
Figure 5. Pre-European major vegetation groups.
| Major Vegetation Group | Area |
|---|---|
| Rainforest and vine thickets | 43,493 |
| Eucalypt tall open forests | 44,817 |
| Eucalypt open forests | 340,968 |
| Eucalypt low open forests | 15,066 |
| Eucalypt woodlands | 1,012,047 |
| Acacia forests and woodlands | 657,582 |
| Callitris forests and woodlands | 30,963 |
| Casuarina forests and woodlands | 73,356 |
| Melaleuca forests and woodlands | 93,501 |
| Other forests and woodlands | 125,328 |
| Eucalypt open woodlands | 513,943 |
| Tropical eucalypt woodlands/grasslands | 256,434 |
| Acacia open woodlands | 117,993 |
| Mallee woodlands and shrublands | 383,399 |
| Low closed forests and closed shrublands | 15,864 |
| Acacia shrublands | 670,737 |
| Other shrublands | 115,824 |
| Heath | 47,158 |
| Tussock grasslands | 589,212 |
| Hummock grasslands | 1,756,962 |
| Other grasslands, herblands, sedgelands and rushlands | 100,504 |
| Chenopod shrubs, samphire shrubs and forblands | 563,389 |
| Mangroves, tidal mudflats, samphires and bare areas, claypan, sand, rock, salt lakes, lagoons, lakes | 112,063 |
Methods
Pre-European vegetation of Australia has been reconstructed using a variety of interpolation and modeling techniques from mapping and information on the present types and extent, historical records and early aerial photographs. It is assumed that Australia had experienced no significant clearing other than changes due to fire regimes prior to European settlement.
The underlying data used to describe the pre-European vegetation is in many cases the same as that representing the present vegetation. Some States and Territories have assumed that vegetation types mapped as pre-European vegetation also approximate the present vegetation.
This presents varying problems in interpreting changes in vegetation. There are very few areas in Australia that have not undergone some modification in species or structure following European settlement (e.g. changes in fire regime). Australian scientists are still developing systems and techniques to assess the condition and changes to condition of native vegetation.
In all states, adding the present vegetation data from the National Vegetation Information System to the available pre-European mapping provided the source for the pre-European major vegetation groups. In South Australia, New South Wales and Tasmania the pre-European vegetation is presented as an interim product to be used at broad State and national scales. In Tasmania the pre-European data set was derived from modelling techniques and is yet to be finalised.
The major vegetation groups that are mapped, represent the dominant vegetation occurring in a particular area.
Applications
The inferred pre-European vegetation mapping can provide:
- a broad baseline to document change in the extent and type of native vegetation;
- information to assist in understanding the landscape for management and conservation of biodiversity;
- an understanding of native vegetation cover which, coupled with details on Australia's soils, topography and climate variability assists construction of a modelled; assessment of natural soil erosion. This then allows us to understand changes in soil erosion patterns that have accompanied land use and are now impacting on the condition of our rivers, estuaries and near shore zones (NLWRA in prep.);
- species and vegetation community information to assist in regional revegetation activities; and
- information to assist in understanding changes in water balance, the key driver of dryland salinity (NLWRA 2001a) and changes in catchment surface water hydrology (NLWRA 2001b).
Limitations
The variety of methods used to map pre-European vegetation, the scale of some of the data and the difficulty of mapping in fragmented landscapes has resulted in an Australia-wide map which presents a combination of very broad and detailed mapping.
Queensland, Western Australia, Victoria and the Northern Territory National Vegetation Information System data have the greatest reliability. The New South Wales, South Australia and Tasmanian data are interim products and provide a broad scale view of Australia's pre-European vegetation.
The Guidelines section of this report 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 pre-European vegetation including the extent, scale and date of collection.
Figures 6 and 7 provide information on the location and extent of data sets, their scale and level of classification used to develop the major vegetation groups.
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