Biodiversity: Habitat protection
Authors
Bruce Wilson, Peter Young and Rosemary Niehus, Environmental Protection Agency
Reviewer
Jeremy Thompson, Environmental Protection Agency
Key findings
- The major pressures on Queensland's biodiversity induced by human settlement and land use continue to be the loss, degradation and fragmentation of native habitat.
- While most of Queensland has relatively continuous native vegetation cover (82% remnant native vegetation in 2003), more fertile landscapes in wetter parts of the state have been reduced to less than 30% of native vegetation cover.
- Clearing has been expanding into semi-arid areas in recent years.
- The rate of clearing has risen during the past decade, although there was a decline in clearing associated with the introduction of the Vegetation Management Act 1999 .
- The cessation of broadscale clearing of remnant vegetation at the end of 2006 will lead to a further reduction in the rate of loss of native vegetation.
- Habitat condition and the extent of other pressures on biodiversity, such as altered fire regimes and grazing pressure in remnant ecosystems, are not as readily reported on as loss of habitat.
- The condition of regional ecosystems in bioregions subject to little or no clearing has declined.
- The recent development of biodiversity assessment and planning tools to prioritise actions, and the implementation of on-ground revegetation and rehabilitation works, are dealing with some of the declines in vegetation condition.
- About 4.6% of Queensland is contained within formal conservation reserves.
- Given its modest extent, the reserve network performs well for comprehensiveness if measured by representation of regional ecosystems, but poorly for adequacy if based on a widely used target of 15% of the state.
- Many off-reserve conservation initiatives have gathered momentum since 2001.
Indicators and summary of status
Indicator |
Status of indicator |
Native vegetation extent |
|
Native vegetation condition |
|
Terrestrial protected areas |
|
Fire regimes |
|
Area revegetated |
|
]
]Importance
Native vegetation extent
Loss of native vegetation is closely associated with impacts on biodiversity through the depletion and modification of habitat and the decline in conservation status of species and ecosystems. Vegetation loss is taken here to include both the removal by clearing of woody species in natural ecosystems and the loss and modification of non-woody natural ecosystems, such as grassland and shrubland.
Quantifying the extent to which all individual taxa have declined and may continue to decline due to clearing and modification of habitat is possible for taxa that are identified as being a priority for conservation. For other taxa, vegetation or regional ecosystems provide a surrogate for describing the pressure from clearing and modification because these data are available for most of the state. There is limited information available for individual species, particularly those that are common. Therefore, reporting on the extent by regional ecosystems and vegetation has been used to define the extent to which clearing and habitat modification are affecting biodiversity.
The shorter-term impacts of clearing on plants and animals at any site range from the total loss of species experienced in the conversion of native vegetation to cultivation, improved pasture or urban use to the reduction in species richness and diversity experienced when woody vegetation is converted to native pasture. The cumulative and longer-term impacts of clearing also need to be taken into account. Clearing across the landscape isolates populations, reduces the size of populations, favours certain species over others and increases the opportunities for invasive taxa to displace native species. For long-lived taxa such as birds, there is a time lag between loss of habitat and consequent loss of species, a process that has been referred to as 'extinction debt'.
Loss of vegetation is not uniform but varies across regions and ecosystem types. Therefore, the proportion of each subregion covered by remnant vegetation and the proportion of each ecosystem remaining compared to its pre-clearing extent that are reported here are key inputs to determining priorities for planning and management actions and are useful indicators of the impacts of vegetation extent on biodiversity.
Endangered and of concern regional ecosystems contain particular combinations of plant and animal species associated with distinctive geology, landform, soils and climate features, and these combinations are at risk of disappearing from the landscape if clearing continues. Some taxa, especially plants with restricted distributions, are at risk of extinction if clearing continues. These ecosystems are also often on lands highly suited to agricultural production.
Area revegetated
Increases in native vegetation extent occur through revegetation. Habitat restoration for nature conservation has occurred primarily through revegetation programs undertaken by community groups, but also occurs through natural regeneration and regrowth of previously cleared areas on agricultural lands. While revegetation offsets the decrease in extent of vegetation through clearing, the replacement vegetation, whether natural regeneration or planted trees, is often unlike the communities that were previously cleared.
Native vegetation condition
Reporting on the extent of vegetation gives no indication of its condition. While some ecosystems have extensive areas remaining, they may have been extensively modified by pressures such as grazing, fire and changes in climate, which cause significant modification to structure, composition and habitat value. Condition information is required to understand the ability of remaining native vegetation to provide habitat for native plants and animals at local site and landscape scales. Reporting on the condition of vegetation is imperative to our understanding of the biodiversity in those areas. The condition of vegetation contributes to identification of priority issues and areas relevant to natural resource managers, including responses to specific interventions and overall trends.
In this report the biodiversity status of regional ecosystems (EPA 2005) is used to provide an indicator of condition. This status is based on an assessment of the condition of remnant vegetation in addition to the pre-clearing and remnant extent of a regional ecosystem.
Fire regimes
Fire has played an important role in shaping much of Australia's landscapes and the composition of the fauna and flora within them. Manipulating fire to create or protect desirable landscape features and habitats has become a matter of primary importance at all levels of land management. Therefore, fire regime is an important indicator of vegetation condition and associated biodiversity.
Terrestrial protected areas
The reserve system is considered the cornerstone of an integrated strategy to conserve nature, including biological diversity. The reserve system aalso makes significant contributions to preservation of cultural heritage, local, regional and national economies and the wellbeing of society.
Formal reserves established under the Nature Conservation Act 1992 and managed by the Queensland Parks and Wildlife Service (QPWS) have traditionally accounted for much of the land in Queensland that is dedicated to nature conservation. Complementary measures, including land acquisition by local government and private nature conservation organisations, and cooperative programs involving landholders, are of increasing importance. The latter includes nature refuges under the Nature Conservation Act 1992 and declarations under the Vegetation Management Act 2004.
Regional ecosystems are used as the primary planning surrogate to assess the adequacy, comprehensiveness and representativeness of the terrestrial conservation estate. Comprehensiveness is measured by the percentage of the total number of regional ecosystems present in the reserve system. Adequacy is measured by the proportion of each regional ecosystem that has more than 15% of its total area reserved.
Pressure and condition
Native vegetation extent
Table 7.1 shows that the rate of clearing of woody vegetation in Queensland, as measured by the Statewide Landcover and Trees Study (SLATS), has varied over the past decade. This rate increased during the 1990s in the lead-up to the introduction in September 2000 of the Vegetation Management Act 1999 , after which there was a substantial decline followed by a slow increase. There was a significant decline in the following year.
Table 7.2 shows the extent of clearing of remnant vegetation and the total area of remnant vegetation across the state's bioregions over the period 1997-2003. These figures show a similar trend to the clearing of woody vegetation, although the figures are different because remnant vegetation includes non-woody vegetation such as grasslands, open-shrublands and some open-woodlands that are not included in the figures in Table 7.1.
Clearing of vegetation has been much more widespread across the east and south of the state, where three bioregions- Brigalow Belt, Southeast Queensland and New England Tableland-have lost over 50% of their native vegetation. Some areas within the Wet Tropics, Mulga Lands and Central Queensland Coast bioregions have also been extensively cleared.
The bioregions with the greatest rates of clearing over the period 1997-2003 are the Desert Uplands, Brigalow Belt, Mulga Lands and New England Tableland. However, Central Queensland Coast (which had lost a substantial proportion of vegetation before 1997) and Southeast Queensland also continued to lose vegetation as a result of clearing. The lowest rates of clearing have occurred in bioregions in the state's west, north-west and far north, the exception being the Mitchell Grass Downs, where gidgee-dominated ecosystems are being selectively cleared.
Comparison between the periods 1997-99 (discussed in the last report) and 1999-2003, the most recent interval for which data are available, indicates that clearing rates for both woody and remnant vegetation decreased in the period 2000-01. This coincided with the September 2000 introduction of the Vegetation Management Act 1999 . Since that time there has been an increase in clearing although the 2001-03 rates were generally lower than the pre-2000 rates.
Subregions defined within each bioregion provide a finer scale of resolution for analysing landscape distribution and the environmental impacts of past and present land uses. Figure 7.1 shows the subregions in central and southern Queensland where remnant vegetation has fallen below 30%, a figure that is widely used as a minimum threshold for habitat retention. In contrast to these areas, western, north-western and far northern parts of the state have experienced negligible levels of clearing.
Table 7.1 Loss of woody vegetation in Queensland 1991- 2004
Interval |
Clearing per year |
|
Hectares |
Percentage of Queensland |
|
1991-95 |
289 000 |
0.17 |
1995-97 |
340 000 |
0.20 |
1997-99 |
425 000 |
0.26 |
1999-2000 |
757 000 |
0.46 |
2000-01 |
380 000 |
0.23 |
2001-02 |
498 000 |
0.29 |
2002-03 |
554 000 |
0.33 |
2003-04 |
482 000 |
0.28 |
Source: DNRM 2006, Table 3
Figure 7.1 2003 remnant vegetation in subregions in Queensland
Source: Accad et al. 2006, Figure 7
Table 7.2 Clearing of remnant vegetation in Queensland's terrestrial bioregions
Bioregion |
Bioregion area (ha) |
Percentage of bioregion remnant 2003 |
Area cleared |
Area cleared |
Area cleared |
Area cleared |
Northwest Highlands |
7 232 970 |
99.4 |
3 380 |
920 |
0 |
510 |
Gulf Plains |
21 911 140 |
99.3 |
3 690 |
3 710 |
3 390 |
3 200 |
Cape York Peninsula |
12 152 050 |
99.0 |
1 050 |
2 270 |
1 260 |
540 |
Mitchell Grass Downs |
24 224 420 |
94.3 |
25 450 |
57 130 |
11 870 |
12 860 |
Channel Country |
23 344 850 |
99.7 |
550 |
1 550 |
2 |
3 920 |
Mulga Lands |
18 584 100 |
78.0 |
75 710 |
179 710 |
64 730 |
200 490 |
Wet Tropics |
1 998 980 |
76.6 |
NA |
740 |
370 |
260 |
Central Queensland Coast |
1 462 970 |
69.9 |
1 970 |
2 970 |
1 080 |
760 |
Einasleigh Uplands |
11 718 580 |
97.8 |
2 950 |
5 060 |
2 880 |
1 380 |
Desert Uplands |
6 885 340 |
83.7 |
49 180 |
76 450 |
63 230 |
47 530 |
Brigalow Belt |
36 500 440 |
42.3 |
239 360 |
290 160 |
96 950 |
86 420 |
Southeast Queensland |
6 203 910 |
44.1 |
6 250 |
9 700 |
3 200 |
3 550 |
New England Tableland |
774 760 |
32.9 |
1 990 |
1 810 |
206 |
490 |
Queensland |
172 994 530 |
80.8 |
411 520 |
632 180 |
249 080 |
361 900 |
NA = not available
Source: Accad et al. 2006, Table 8. Area column totals may have discrepancies due to rounding to nearest 10 ha during calculations.
Table 7.3 presents data showing the loss from clearing for broad vegetation types. Until 2003, the broad vegetation types with the greatest loss in terms of their pre-clearing area were rainforests and vine thickets; subtropical woodlands such as poplar box, narrow-leaved and silver-leaved ironbark, mountain coolibah and cypress pine woodlands; and brigalow and gidgee. Historically, brigalow has experienced greater rates of clearing than gidgee, a species of semi-arid areas. However, the rate of clearing of gidgee has been increasing as clearing gradually moves into drier environments. During the period 2001-03 mulga woodlands and eucalypt woodlands continued to experience the highest rate of clearing in the state.
Table 7.3 Pre-clearing, clearing 2001-03 and remnant in 2003 across broad vegetation types
Broad vegetation type |
Pre -clearing area (ha) |
Area cleared 2001-03 (ha) |
Remnant 2003 area (ha) |
Remnant 2003 area (% of |
Rainforests, scrubs |
3 567 250 |
1 570 |
2 078 130 |
58 |
Wet eucalypt open forests |
477 600 |
540 |
340 930 |
71 |
Eucalypt woodlands to open forests |
31 507 830 |
34 630 |
26 222 460 |
83 |
Eucalypt open forests to woodlands on floodplains |
10 810 550 |
19 340 |
7 906 410 |
73 |
Eucalypt dry woodlands on depositional plains |
22 573 730 |
222 450 |
14 352 960 |
64 |
Eucalypt low open woodlands, usually with spinifex understorey |
9 384 670 |
4 840 |
9 288 010 |
99 |
Callitris woodland |
1 170 770 |
9 340 |
804 280 |
69 |
Melaleuca low open woodland on depositional plains |
9 228 090 |
8 350 |
8 458 170 |
92 |
Acacia aneura dominated open forests, woodlands and shrublands |
12 965 970 |
294 950 |
10 849 110 |
84 |
Other Acacia dominated open forests, woodlands and shrublands |
26 622 540 |
111 720 |
16 153 130 |
61 |
Other non-eucalypt coastal communities or heaths |
1 494 170 |
620 |
1 417 800 |
95 |
Tussock grasslands, forblands |
33 691 140 |
11 000 |
32 291 220 |
96 |
Hummock grasslands |
4 436 400 |
4 970 |
4 417 070 |
100 |
Wetlands (swamps, lakes) |
3 764 900 |
2 660 |
3 563 630 |
95 |
Mangroves and saltmarshes |
1 298 920 |
60 |
1 266 410 |
97 |
Total |
172 994 530 |
727 030 |
139 409 700 |
81 |
Source: Accad et al. 2006, and Queensland Herbarium, unpublished data. Area column totals may have discrepancies due to rounding to nearest 10 ha during calculations.
Table 7.4 shows the extent of clearing in relation to the Vegetation Management Act status of regional ecosystems in bioregions where regional ecosystem mapping has been completed or is in progress ( Accad et al. 2006).
In bioregions where regional ecosystem mapping has been completed, 2% of the clearing in the period 2001-03 occurred in endangered regional ecosystems and 13% in those with an of-concern status. This is a further reduction in the level of clearing in these ecosystems from the previous two reporting periods when 34-54% of the total clearing occurred within these ecosystems.
Table 7.4 Clearing (ha/year) in 2001-03 across regional ecosystems with a Vegetation Management Act status of endangered, of concern and not of concern
Bioregion |
Endangered |
Of concern |
Not of concern |
Total |
Northwest Highlands |
0 |
0 |
510 |
510 |
Gulf Plains |
0 |
4 |
3 200 |
3 200 |
Cape York Peninsula |
0 |
100 |
440 |
540 |
Mitchell Grass Downs |
0 |
1 860 |
11 000 |
12 860 |
Channel Country |
0 |
0 |
3 920 |
3 920 |
Mulga Lands |
1 120 |
17 500 |
181 870 |
200 490 |
Wet Tropics |
30 |
60 |
170 |
260 |
Central Queensland Coast |
50 |
340 |
370 |
760 |
Einasleigh Uplands |
0 |
30 |
1 350 |
1 380 |
Desert Uplands |
500 |
970 |
46 060 |
47 530 |
Brigalow Belt |
5 070 |
24 120 |
57 230 |
86 420 |
Southeast Queensland |
390 |
760 |
2 380 |
3 550 |
New England Tableland |
40 |
330 |
120 |
490 |
Total |
7 200 |
46 070 |
305 700 |
361 890 |
Source: Accad et al. 2006, and Queensland Herbarium, unpublished data. Area totals may have discrepancies due to rounding to nearest 10 ha during calculations.
Area revegetated
Table 7.5 shows the area of new woody regrowth recorded over the period 1997-99 by bioregion. These figures were derived from remote sensing. For some bioregions, such as the Brigalow Belt and Southeast Queensland, there are substantial areas of regrowth, although even in these regions the total area of regrowth is very small compared to the amount of clearing (cf. Table 7.1).
The remote sensing used to map areas of regrowth cannot establish the purpose, extent, structural complexity, or dominant species of revegetated areas (Kuhnell et al. 1998). The remote sensing techniques do not discriminate well between areas of vigorous regrowth and green pasture (DNR 2000). Recently developed techniques will enable reporting on areas of regrowth and compare these areas with revegetation and restoration projects. SLATS intends to update these figures with reports on longer-term trends in regrowth and woodland thickening and thinning, while the EPA will monitor progress of vegetation from non-remnant to remnant status.
Native vegetation condition
Table 7.6 shows the proportion, in 2003, of each bioregion that is remnant vegetation and the proportion of regional ecosystems with a biodiversity status of endangered, of concern and not of concern. While 82% of the state had then been mapped by the Queensland Herbarium as remnant native vegetation, there was a large variation in the condition of remaining vegetation, which is reflected in the variation in biodiversity status across the bioregions.
Depletion of regional ecosystems due to clearing and modification is the primary contributor to the high proportion of endangered and of-concern regional ecosystems in the New England Tableland, Southeast Queensland and Brigalow Belt, and in parts of the Wet Tropics, Mulga Lands and Central Queensland Coast. In other bioregions, the decline in condition of regional ecosystems has been the primary cause of their of-concern status. Their condition has declined because of weeds, modification to floristic and structural composition due to trampling and grazing by domestic and feral animals, scalding and topsoil loss due to total grazing pressure, and changes in hydrology arising from bunding, dams and groundwater extraction.
Table 7.5 Rate of new woody regrowth change (km²/year), detected using satellite imagery for the period 1997-99 by biogeographic region
Biogeo-graphic region |
Brigalow Belt |
Channel Country |
Central Mackay Coast |
Cape York Peninsula |
Desert Uplands |
Einasleigh Uplands |
Gulf Plains |
Area (km²) of new |
46.43 |
0.00 |
1.55 |
0.29 |
0.56 |
1.87 |
0.04 |
Biogeographic region |
Mitchell Grass Downs |
Mulga Lands |
Northern New England Tableland |
North West Highlands |
Southeast Queensland |
Wet Tropics |
|
Area (km²) of new |
1.76 |
4.33 |
0.06 |
0.00 |
38.53 |
1.08 |
Source: DNR 2000, Table 9, page 24
Table 7.6 Proportion in 2003 of each bioregion that is remnant vegetation, and proportion of regional ecosystems with a biodiversity status of endangered, of concern and not of concern
Bioregion |
Percent- |
||||||
Percent- |
Percent- |
Percent- |
Percent- |
Percent- |
Percent- |
||
Northwest Highlands |
99.4 |
7.0 |
NA |
46.5 |
NA |
46.5 |
NA |
Gulf Plains |
99.3 |
3.6 |
NA |
38.1 |
NA |
58.3 |
NA |
Cape York Peninsula |
99.0 |
2.7 |
NA |
42.8 |
NA |
54.5 |
NA |
Mitchell Grass Downs |
94.3 |
1.9 |
NA |
18.5 |
NA |
79.6 |
NA |
Channel Country |
99.7 |
3.6 |
NA |
5.4 |
NA |
91.1 |
NA |
Mulga Lands |
78.0 |
9.2 |
1 |
35.4 |
26 |
55.4 |
73 |
Wet Tropics |
76.6 |
42.7 |
15 |
47.0 |
20 |
10.3 |
65 |
Central Queensland |
69.9 |
29.3 |
7 |
50.7 |
19 |
20.0 |
74 |
Einasleigh Uplands |
97.8 |
0.7 |
0.1 |
40.8 |
9 |
58.5 |
91 |
Desert Uplands |
83.7 |
20.8 |
1 |
39.0 |
15 |
40.3 |
83 |
Brigalow Belt |
42.3 |
23.3 |
4 |
35.5 |
25 |
41.3 |
71 |
Southeast Queensland |
44.1 |
17.2 |
7 |
51.7 |
21 |
31.1 |
73 |
New England Tableland |
32.9 |
60.0 |
13 |
24.0 |
73 |
16.0 |
14 |
NA = not available
Source: Accad et al. 2006, and Queensland Herbarium, unpublished data
Fire regimes
The total area burnt across Queensland per year is shown in Table 7.7. Burning falls into two classes, wildfire and planned use of fire. The latter includes:
- grazing production purposes, principally for promotion of green herbage (and also, to an extent, for the control of woody regrowth that competes with pasture);
- hazard- or fuel-reduction burning, especially around urban areas;
- ecological burning to maintain fire-dependent plant and animal communities.
Much of Queensland receives a higher proportion of rainfall in the warmer part of the year and burning occurs mainly in the late winter-spring period when understorey vegetation, especially grass, is dry. However, there are limited data to explain the extent to which fire is an issue for biodiversity because of adverse impacts associated with frequency (too frequent or too infrequent) and intensity.
Terrestrial protected areas
Terrestrial protected areas cover 4.6% of Queensland and a wide range of different landscapes and regional ecosystems. Much of the country that is incorporated into protected areas has been selected because the native vegetation and associated biodiversity remain in good condition. Management planning aims to identify the inputs that will be required to maintain and enhance vegetation condition, including use of fire, control of pests and limiting impacts of visitors. QPWS collates data on planned use of fire, especially ecological burning (Table 7.8) as well as wildfire occurrences across the protected area estate. Ecological burning has been constrained in the past few years by very dry weather conditions across much of the state at the optimal time of burning. A larger total area has been burnt in preceding years.
Table 7.7 Total area burnt across Queensland per year 2003-05
Year |
Total area burnt in Qld (ha) |
2003 |
7 570 000 |
2004 |
10 570 000 |
2005 |
3 670 000 |
Source: Western Australia Department of Land Information-Satellite Remote Sensing Services. The data are derived from NOAA AVHRR 1-km resolution satellite imagery and areas of less than 4 km² that are burnt by fire are not mapped.
Table 7.8 Total area of ecological burning on EPA estate 2004-06
Year* |
Total area of ecological burning undertaken |
2004 |
284 000 |
2005 |
220 400 |
2006** |
376 300 |
*Year: statistics are collated for the period 1 March to 28 February of the following year.
**Figure for 2006 is for period 1 March to 31 October only.
Source: QPWS, October 2006
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Last reviewed 12 May 2011
Last updated 13 February 2008