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In this section you will find detailed information, including national overviews and state and regional level assessments, from the 2000-2002 National Land and Water Resources Audit theme assessments.
Australian Terrestrial Biodiversity Assessment 2002
Paul Sattler and Colin Creighton
National Land and Water Resources Audit, 2002
ISBN 0 642 3713
Case Study
Isaac-Comet Downs (Brigalow Belt North 11) second highest stress class
Bottle tree, Brachychiton rupestre
Photo: P. Sattler
The Isaac-Comet Downs subregion incorporates the Isaac, Comet, Upper MacKenzie Rivers as well as portions of the Fitzroy and Nogoa Rivers. Land uses include grazing native pastures, grazing improved pastures and some cultivation.
Predominant vegetation includes brigalow (Acacia harpophylla), Dawson gum (Eucalyptus cambageana) and residual vegetation including narrow-leaved ironbark (E. crebra), bendee (A. catenulata) or lancewood (A. shirleyi). Alluvium is dominated by brigalow or coolibah (E. coolabah).
The subregion contains important habitat for a diverse range of fauna (particularly birds) and habitat for rare and threatened species including star finches, platypus, turtles, the red goshawk and golden tailed geckos. Several properties have important stands of remnant brigalow, poplar box, ooline and bonewood, and possibly Bridled Nail-tail Wallaby populations. Important wetlands support high fish diversity, Freckled Duck populations and over 100 other waterbird species.
Condition and trend
Condition of riparian vegetation within the subregion is fair with a rapidly declining trend.
Of the 82 ecosystems, 29 are listed as endangered in Queensland and a further 19 considered as vulnerable but not protected on freehold land. The majority of threatened ecosystems are eucalypt woodlands with grassy understoreys and brigalow forest and woodlands. Most of the threatened ecosystems in the region are still declining although clearing of endangered ecosystems has been halted by recent legislative changes in Queensland.
There are 25 threatened species in the subregion. This includes five vulnerable and one extinct bird, one vulnerable insect, two endangered mammals, four vulnerable reptiles and nine vulnerable and three endangered plants. Threatened species are generally declining. For a large number of species, particularly plants, there is little information about their condition or trend.
Threatening processes
Broadscale vegetation clearing has resulted in less than 26% natural vegetation remaining and is a continuing, major threat to species. Grazing pressure, changed fire regimes and feral animals, in particular pigs, cats and foxes are additional threats to biodiversity. Extensive clearing has contributed to habitat fragmentation with many remnants below a size capable of retaining regional fauna diversity, has encouraged weeds, and changed hydrology. Those ecosystems occurring on alluvial soils and hills with shallow soils have the greatest number of threats.
Management responses
Isaac-Comet Downs' ecological health has been severely degraded and a coordinated strategy is imperative if some level of biodiversity conservation is to be achieved. The subregion, and indeed the whole bioregion, has the highest priority for reserve consolidation to secure the key remaining large areas of high conservation value. Lack of funding to quickly acquire and manage these remaining key areas is of serious concern.
Major constraints exist to achieve off park conservation outcomes. The degree and rate of land clearing and fragmentation means that existing remnant vegetation within the subregion must be protected and managed for biodiversity conservation.
Restoration targets of 30% are now proposed in some catchment plans in parts of southern Australia to restore landscape function and biodiversity (refer chapter 9). The cessation of clearing in the Isaac- Comet subregion, where less than 30% vegetation remains, is therefore a priority to avoid costly restoration in the future. Appropriate mechanisms to end clearing and to reward property owners who retain vegetation above what might be a reasonable duty of care should be considered as part of structural adjustment.
Incentives are needed to drive private land conservation. This includes encouraging the protection of regrowth to enhance key remnants, the management of habitat of threatened species and recovery of endangered ecosystems. Further protection of habitat with fencing to manage grazing pressure, and control of feral animals and weeds are other important management actions required.
A high number of species have no recovery plans or recovery actions identified and resources are needed for ecological research.
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