• Change text size
• Skip to content

Australian Natural Resources Atlas

Natural Resource Topics

• About us
• Contact us

Search:

• ANRA home
  • ARO
  • Map maker
  • Natural resource topics
  • Data Library

• Natural resource topics
  • Agriculture
  • Coasts
  • Dryland Salinity
  • Irrigation
  • Land
  • Natural resource economics
  • People
  • Rangelands
  • Soils
  • Vegetation and biodiversity
  • Water
  • Publications

• Vegetation and biodiversity
  • Overview
  • Assessment
    • New South Wales
    • Victoria
    • Queensland
    • South Australia
    • Western Australia
    • Tasmania
    • Northern Territory
    • Australian Capital Territory
  • Landscape health
  • NVIS framework
  • Extent
    • New South Wales
    • Victoria
    • Queensland
    • South Australia
    • Western Australia
    • Tasmania
    • Northern Territory
    • Australian Capital Territory
  • Clearing
    • New South Wales
    • Victoria
    • Queensland
    • South Australia
    • Western Australia
    • Tasmania
    • Northern Territory
    • Australian Capital Territory
  • Management

The material below is an extract from the Australian Native Vegetation Assessment 2001 report. For ease of cross reference, figure, table and section references pertain to the chapter structure of this report. The Further Information section provides links to the Australian Native Vegetation Assessment 2001 report.

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:

• rainforest and vine thickets (0.18% of the total area);
• eucalypt open forests (0.01% of the total area);
• acacia forests and woodlands (9.21% of the total area);
• acacia open woodlands (none remaining); and
• tussock grasslands (0.47% of the total area).

All groups have restricted distributions in the subregion.

 

Figure 16. 1996/97 land use in the Isaac-Comet Downs subregion.	Figure 17. Pre-European vegetation 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
A negative value indicates an increase in extent of vegetation type