In New South Wales, about 6% of the state is wetland and the majority of wetlands are found west of the Great Dividing Range.
Wetlands are characterised by being wet long enough for plants and animals to adapt to, and become dependent on, wet conditions for at least part of their life cycle. Wetlands can be permanent, intermittent (e.g. seasonally) or ephemeral (e.g. just after flooding) with fresh, brackish or salty water. They include lakes, lagoons, mangroves and salt marsh, rivers, floodplains, swamps, bogs, billabongs, marshes, coral reefs and seagrass beds.
In NSW wetlands cover approximately 4.3 million ha or 6% of the state and are predominately found west of the Great Dividing Range in the form of floodplain wetlands. Only 4% of wetlands are along the coast – these are 59% estuarine wetlands such as mangroves and salt marshes, 35% coastal lakes and lagoons, 5% floodplain wetlands and 1% freshwater lakes.
Wetlands play a vital role in our natural environment. They reduce the impact of flooding by capturing and holding excess water, by filtering pollutants flowing through them and providing habitats for a large variety of animals and plants. They also form nurseries for fish and other aquatic life and are critical for Australia’s commercial and recreational fishing industries. Wetlands also recharge groundwater systems, can act as a sink for greenhouse gases, and many have substantial significance to Aboriginal culture.
With changing water levels from day to day or week to week, wetlands have an ever changing variety of animals and plants. After floods or rain, inland wetlands come to life. Plants, insects, micro-organisms, water birds, frogs, fish and mammals suddenly sprout, hatch or arrive in their thousands. These plants and animals are adapted to – and depend on – the unpredictable periods of flood and drought for their survival. Wetting and drying drives many important wetland processes. For example, many water birds and other animals can only breed after rain or during floods, when there are enough food resources to support breeding and feeding the young.
Threats to Wetlands
Wetlands are among the most threatened ecosystems in the world. In the past, many wetlands were drained or filled in to create farmland or urban areas. In NSW, regional wetland losses range from 40% to 80% since European settlement.
Although no longer openly destroyed, wetlands are currently affected by alteration of natural flow patterns caused either by droughts or by water extraction and regulation of rivers by building dams and weirs. Urban development, land clearing, grazing and use of pesticides can also impact adversely on water quality and the natural water cycles of wetlands.
Another threat to wetlands, and other ecosystems, is climate change. In inland NSW, climate change is expected to modify rainfall, evaporation and flooding patterns, increase droughts and bushfires, change the temperature of water bodies and, along the coast, cause sea levels to rise. This threat will cause the coastline to retreat and saltwater to flood freshwater lakes and lagoons.
Effective conservation of wetlands requires complementary management of both land and water by government and surrounding landowners. Water availability is the primary pressure on inland wetlands, while urban development is a significant pressure on coastal wetlands.
Many wetlands are conserved within existing National Parks and reserves and may have some protection under international treaties, such as the Ramsar Convention. Planning laws can help protect wetlands from development.
In most rivers, a share of the water has been allocated for the environment, including important wetlands. Where more water is needed, such as in the Murray Darling Basin, water is being recovered for the environment, particularly for major or icon wetland systems such as the Barmah-Millewa Forest on the Murray River and the Macquarie Marshes on the Macquarie River.
The Gwydir Wetlands are situated predominantly on private land and are located in the Darling Riverine Plains of the Murray-Darling Basin. Four areas of wetlands in the Gwydir are listed under
the Ramsar Convention.
Much of the Gwydir wetland complex has been modified due to river regulation, however they still play a significant part in the biological and ecological functioning of the Murray-Darling Basin as a whole. The Gwydir wetlands provide a special habitat for the breeding and feeding of large numbers of colonial waterbirds. Major wetlands in the Basin are rarely inundated simultaneously and are not always suitable for bird breeding at the same time, therefore the Gwydir wetlands provide an important ‘link’ in the network of wetlands used by both regional and national colonies of waterbirds.
The wetlands support an appreciable assemblage of rare and vulnerable species, including magpie geese, egrets, ibis (including glossy) and black-necked storks. The wetlands also contain mammals such as the eastern water rat, swamp wallaby and an estimated 14 species of frogs.
The wetland is noted as having one of the largest stands of water couch (an aquatic grass) in NSW and also contains other significant plants such as spike rush, tussock rush and cumbungi.
Department of Environment, Climate Change and Water