Two aquatic ecosystems were listed as threatened ecological communities under the EPBC Act since 2011: Coastal Upland Swamps in the Sydney Basin bioregion (listed 2014) were listed as endangered, and Seasonal Herbaceous Wetlands (Freshwater) of the Temperate Lowland Plains (listed 2012) were listed as critically endangered. Clearing, altered hydrological processes and invasive species are indicated as ongoing threats to both ecosystems, as well as changed fire regimes and climate change.
Groundwater-dependent ecosystems are geographically small, yet they are an important part of Australian biodiversity. Groundwater-dependent ecosystems are frequently connected to surface waters. In perennial rivers, such as the Daly and Roper rivers of the Northern Territory, permanent base flows are maintained by groundwater inputs during the dry season. Base flows allow fishes to persist through the dry season, and are important areas of production for aquatic invertebrate animals (Pollino & Couch 2014). Few jurisdictions report on the condition of groundwater-dependent ecosystems (however, see New South Wales and Western Australia in Jurisdictional reporting on freshwater species and ecosystems). The New South Wales Government has been actively engaged in identifying groundwater-dependent ecosystems across the state; however, the condition and trend of these ecosystems are largely unknown.
The Murray–Darling Basin is a highly modified, regulated river system that covers 14 per cent of the Australian continent and generates approximately 45 per cent of Australia’s irrigated agriculture. It is generally accepted that most flow-dependent ecosystems of the Basin are in poor ecological condition, particularly in the southern Basin, where river regulation and water diversions have resulted in the greatest alterations to flow regimes (Davies et al. 2010, 2012). In response to mounting ecological concerns, the Australian Government initiated major water reforms, culminating in the Water Act 2007 and the Murray–Darling Basin Plan 2012 to address overallocation of irrigation water and restore flows to rivers. The Inland water report graded the state of ecological processes and key species populations in the Murray–Darling as very poor with a deteriorating trend, noting widespread loss of ecosystem function and species population decline.
The South Australian NRM report cards assessed the ecological condition of the Murray River in South Australia as poor, but noted that populations of some communities of aquatic plants, birds and aquatic animals improved between 2010 and 2013 in the Coorong, Lower Lakes and Murray Mouth. Since the millennium drought (which lasted from 2000 to 2010, although in some areas it began as early as 1997 and ended as late as 2012), the condition of river red gums on the floodplains has improved, but the 2013 (partial) Sustainable Rivers Audit found that fish populations in the Murray River channel declined from poor to very poor, and other aquatic animals remained in a moderate condition.
Rivers and riparian habitats
The ecological condition of waterways across Australia is variable; most states and territories (Australian Capital Territory, New South Wales, South Australia, Tasmania, Victoria and Western Australia) report poor to moderate condition of rivers and/or freshwater aquatic ecosystems (see Jurisdictional reporting on freshwater species and ecosystems). Twenty-three per cent of major rivers and tributaries in Victoria were in good or excellent condition.
In northern Australia, aquatic ecosystems (including estuaries, floodplain and riverine) are generally considered to be in overall good ecological condition, notwithstanding areas of localised poor condition (e.g. high riverine disturbance index values for the Fitzroy, Ord, Leichhardt and upper Mitchell rivers). In the arid zone, aquatic systems are considered to be in poorer condition overall because of the impacts of cattle and large feral mammals, as well as losses of some endemic fish and invertebrate fauna in some small spring systems because of introduced fish species. Connectivity of river systems in the arid zone is rated high for most rivers, because the number of impoundments and large dams is low compared with elsewhere in Australia (27 versus 467 dams of more than 0.2 GL).
Data from the Great Barrier Reef Marine Monitoring Program show that overall forest loss in riparian areas continued between 2009 and 2013 (31,000 hectares, or 0.4 per cent) in Great Barrier Reef catchments, with an increased rate of loss compared with previous periods.
Australia has 65 wetlands listed under the Ramsar Convention, with a surface area of more than 8 million hectares. These wetlands are recognised as a matter of environmental significance under the EPBC Act. Australia’s latest report to the Ramsar Convention (DoE 2015b) noted that there is currently no comprehensive national inventory of Ramsar wetlands in place, and it is not possible to definitively state whether the condition of wetlands overall in Australia has improved, deteriorated or stayed the same.
Wetland condition is generally reported by the jurisdictions to be overall poor to moderate (see Jurisdictional reporting on freshwater species and ecosystems); Victoria reports 56 per cent of high-value wetlands in good or excellent condition. Wetland extent is reported as declining in the Swan Coastal Plain and in Queensland. The greatest ongoing losses in Queensland occur in the Murray–Darling and north-east coast areas. Data from the Great Barrier Reef Marine Monitoring Program show that overall loss of wetlands in adjacent catchments continued between 2009 and 2013 (330 hectares, less than 0.1 per cent), although the rate of loss was lower than in previous periods. Wetland extent is reported as stable in New South Wales.
Waterbird communities have been found to be a useful indicator for identifying long-term trends in, and effects of water management on, biodiversity at a range of scales from the entire Murray–Darling Basin, to the Murray River catchment or individual wetlands (Kingsford et al. 2013). The Eastern Australian Waterbird Survey provides baseline information with which to assess changes in, and impacts on, eastern Australian wetlands and rivers. The survey includes estuaries, coastal lakes, rivers, swamps, floodplains and saline lakes, as well as dams, reservoirs and impoundments.
The survey results show that the wetland area across eastern Australia declined in 2015 to below the long-term average (1983–2015; Figure BIO24) (Porter et al. 2014). The 2015 aerial surveys showed that the Macquarie Marshes and Lowbidgee wetlands were partially filled by environmental flows, but these were relatively small areas compared with large flooding years. Most rivers in the Murray–Darling Basin had reduced flows, with mostly dry wetland habitat on their floodplains, including the large lakes of the Menindee Lakes (Porter et al. 2015). Lake Eyre and Cooper Creek wetlands were mostly dry except for a small group of rain-filled wetlands east of Lake Eyre. Other important wetlands were dry, including the Diamantina and Georgina rivers, and lakes Yamma Yamma, Torquinie and Mumbleberry in Queensland. Figure BIO24 illustrates a broad analysis of variation in wetland area during the past 30 years, with a strong correlation with the number of waterbirds in the system (see Terrestrial ecosystems and communities). The Murray–Darling Basin Plan (which came into effect in 2012) has established a coordinated Basin-wide environmental watering strategy across the Basin, agreed to by the Australian Government, and the South Australian, Victorian, New South Wales, Queensland and Australian Capital Territory governments.