Aquatic species and ecosystems


The state of, and trends in, aquatic species and ecosystems are dealt with in detail in Chapter 4: Inland water. Here we draw briefly on that chapter and summarise what state and territory SoE reports say about aquatic species and ecosystems.

The attention given to aquatic systems in SoE reports by the states and territories ranges from no specific mention to some detail (Table 8.17). The national assessment of terrestrial biodiversity reported that only 17% of Australia has comprehensive mapping of wetlands.15 In the well-studied Murray–Darling Basin—an example of a system whose lands and rivers have been largely developed for agricultural and other industries and for human settlements—there is evidence of major declines (Table 8.17). Native fish species in the Murray–Darling Basin were found in only 43% of valley zones where they were expected to occur. By contrast, in the less-developed Lake Eyre Basin, rivers have been assessed as being in generally good condition and ecologically functional.86

Ecological processes in inland waters have been altered to some degree across most parts of Australia. For much of northern and remote Australia, these changes do not affect ecosystem function significantly and, with a few exceptions, there is little evidence that populations of aquatic species are declining. By contrast, in most southern regions, inland water ecological processes have changed substantially and ecosystem function is significantly affected, with significant declines in many native species populations. The Eastern Australian The Eastern Australian Waterbird Surveys covering 1983–2009 found a consistent decline in waterbird numbers after 1999 below the long-term mean. This decline was associated with the millennium drought (lasting from 2000 to 2010 in southern Australia, but starting as early as 1997 in some areas), but also with long-term effects of river regulation, which has reduced water flow. There was also a significant decline in the number of breeding waterbirds and the number of breeding species estimated over time.

Table 8.17 Summary of assessments of aquatic ecosystemsa in state and territory state of the environment reports and the most recent national terrestrial biodiversity assessmenta
Jurisdiction State (and trend if reported)
ACT Tableland wetlands are under considerable threat even though they are largely included in reserves
NSW Historically, clearing and grazing have had major detrimental impacts on many wetlands
There is little mention of current state or trends in the report
NT Wetlands are a feature of both wet and arid parts of the territory, but there are limited published data on their extent or condition on a territory-wide basis
Qld The loss of wetlands continued to occur at approximately 7000 hectares per year (0.34% of 1997 total) from 1997 to 2003; palustrine and riverine wetland systems have experienced the greatest percentage annual reduction in extent. Relatively, estuarine and lacustrine systems have been least affected
There were insufficient data to report on the condition of wetlands
Between 1997 and 2003 there was an overall loss of approximately 370 hectares per year of wetlands in the coastal zone
SA Aquatic systems are included in the broader biodiversity assessment and not discussed separately
Tas There are an estimated 20 597 wetlands with a total area of 206 790 hectares
Overall, 59% of the state’s wetlands and 74% of their total area are still in natural or near natural condition; however, 35% (15% by area) have been severely altered and 6% (11% by area) have been significantly altered
Vic Many aquatic species are now considered threatened, including 21 freshwater and estuarine fish species, 11 frog species and 29 species of waterbirds
Macroinvertebrate communities were found to be in good condition across almost half the reach length assessed as part of the 2004 Index of Stream Condition; the total index of abundance for waterbirds in eastern Australia has shown a declining trend over past decades, with 2007 having the second-lowest abundance on record
Survival and diversity of the native aquatic fauna of inland waters is declining
WA Aquatic and marine biodiversity is generally less well known and described than terrestrial taxa, and the lack of knowledge remains a significant shortcoming
National Only 17% of Australia has comprehensive mapping of wetlands, and case studies indicate a widespread decline in their extent
There has been a loss of 90% of floodplain wetlands in the Murray–Darling Basin (MDB). The Sustainable Rivers Audit of the MDB found 13 river valleys to be in very poor health, 7 in poor health, 2 in moderate health and 1 in good health
The Lake Eyre Basin (LEB) Rivers Assessment found the rivers and catchments of the LEB to be in generally good condition, with critical aquatic ecosystem processes remaining intact

ACT = Australian Capital Territory; NSW = New South Wales; NT = Northern Territory; Qld = Queensland; SA = South Australia; Tas = Tasmania; Vic = Victoria; WA = Western Australia

a See also Chapter 4: Inland water

b See notes below Table 8.5 for caveats and sources

Cork S (2011). Biodiversity: Aquatic species and ecosystems. In: Australia state of the environment 2011, Australian Government Department of the Environment and Energy, Canberra,, DOI 10.4226/94/58b65ac828812