Biodiversity: Condition

Independent report to the Australian Government Minister for the Environment and Heritage
Beeton RJS (Bob), Buckley Kristal I, Jones Gary J, Morgan Denise, Reichelt Russell E, Trewin Dennis
(2006 Australian State of the Environment Committee), 2006

5.1 Condition

As reported in SoE2001, biodiversity continues to be in serious decline in many parts of Australia (Williams et al 2001). This legacy effect represents the consequence of past actions and it will be some time before responses to recent actions can be seen. Recognising change is difficult because of the imperfect knowledge of the condition and trend of biodiversity at a range of scales. Also unknown are the implications of change for sustaining Australia’s natural systems and heritage.

It is only for some iconic groups that estimates of condition can be made. For example, analysis of the 1977–81 and 1998–2001 Bird Atlas surveys showed that 29 species (out of 497 species) had significantly decreased reporting rates over the 20-year period. Grassland, woodland and ground-nesting guilds were particularly affected (Garnett et al 2002). In the oceans, key habitats and groups of species, including kelp, seagrass and a range of fish and seabirds are showings changes in distribution . In addition, there is little doubt that a number of fish species have also declined. Expert opinion in 2001 was that a large proportion (39 per cent of Australia’s 85 bioregions have more than 30 per cent of their ecosystems described as threatened (NLWRA 2002b).

A new approach to assessing the condition of ecological communities has been proposed by the Threatened Species Scientific Committee (DEH 2006e). This approach recognises the impact of degradation through the use of condition classes that describe areas of an ecological community that have a similar conservation value.  The definition of an ecological community listed under the EPBC Act will now include information on the condition classes. This new approach is for areas of land that contain degraded examples of listed ecological communities may still be rehabilitated. This approach adds to the credibility of the listings and will assist regional bodies in developing appropriate management responses (DEH 2006e).

Many of Australia’s threatened species are in the Murray–Darling Basin, south-west Western Australia, populated coastal regions, and in the Tasmanian Midlands. Some areas contain more than 150 threatened species. More than half of the ecosystems in the developed coastal areas and the Murray–Darling Basin are under severe pressure and significant declines are likely (NLWRA 2002b, Olsen et al 2006, Tyler 2006.

Across Australia the condition of nationally important wetlands varies: those in northern Australia are generally in good condition; those in southern Australia need significant management actions for their recovery. Of 901 (as at 2006) nationally important wetlands  in Australia, 64 are protected under the Ramsar Convention. An assessment in 2001 found that a total of 231 nationally important wetlands were under pressure from changes to water regimes (Table 8).

Table 8: Number of nationally important wetlands and number with threatened water regimes (as at 2001)
State or territory Total number of sites Number of Commonwealth owned or managed sites Number of wetlands with threatened water regimes*
Australian Capital Territory 13 0 4
New South Wales 178 6 38
Northern Territory 33 4 7
Queensland 181 8 42
South Australia 69 1 19
Tasmania 89 0 13
Victoria 159 4 57
Western Australia 120 8 51
External Territories 9 9 -
Total 851 40 231

Note: * Source is Davis et al (2001)

Source: DEH (2001)

Changes to Australia’s wetlands and floodplains have caused a decline in the number of waterbirds  dependent on floodplains in areas that have been permanently flooded (for example, the Macquarie Marshes and Lowbidgee wetlands). Waterbird numbers across eastern Australia have declined since 1983, with the most significant decline occurring between 1984–86, and with further declines after 1991 (Kingsford and Porter 2005). Overall, annual average bird numbers have fallen from 1.1 million in 1983 to 0.2 million in 2004. Waterbird breeding grounds depend on regular flooding for their replenishment; a decrease in the frequency of flooding inevitably decreases the frequency of breeding and hence the numbers of birds. Should flooding be prevented altogether, there can be little or no breeding (Frith 1967).

Some important aquatic indicator species have also declined, including many species of aquatic macro-invertebrates , freshwater fish , and frogs . In Australia, four species of frog are extinct, 15 are endangered and another 12 are listed as vulnerable; in total about 14 per cent of frog species are threatened and there are an increasing number of sites in Australia in which frogs are no longer found. While some of this decline may be attributed to the Chytrid fungus, nobody knows whether, if, or to what extent, human activities have exacerbated the problem.