Salinity in Australia
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Salinity is a major environmental issue in Australia. Salinity describes the salt content of water or soil. When the salt content rises to an extreme, it degrades the water quality and land efficiency. This is the problem that is being faced in Australia; salt levels are becoming so extreme that is affecting plant and animal survival, thus damaging infrastructure.
Dryland salinity is caused when the rising water-table surfaces natural salts in the soil. The salt remains in the soil and becomes increasingly concentrated as the water evaporates or is used by plants (Australian Government, 2001). One of the main causes for rising water-tables is the removal of the native Australian vegetation. They have deeper roots and use more water than the crop plants that are replacing them. The crop plants have short roots and cannot absorb as much water as the native plants, therefore causing the water-table to rise and bring salt to the surface. Dryland salinity is having detrimental effects on Australia. There is a continuing loss of productive farmland; degradation of soil and water resources; extinction of native plant and animal species and social and economic decline of rural communities. There are many approaches to confronting Australias salinity problem, but there is not a universal solution that would be practical everywhere.
Salt is a natural feature of the Australian landscape. Until European settlement, the salt remained deep in the soil below the root zone of the native vegetation. The clearing of the natural vegetation results in the slow release of these salts to the soil surface or to the river system, which causes a dramatic increase in the salt concentration of the river flow (Anonymous, 1979). Deep rooted native vegetation tended to use most of the rainfall that it received. However the shallower rooted crop plants that are replacing the native vegetation does not use all the rainfall that it receives, causing the excess rainfall to seep deep down through the soil profile (Government of S. Australia, 2005). The excess water is recharging the underlying ground water systems at a much faster rate than what was occurring under natural conditions and consequently the ground water levels are rising.
Salinity is having a devastating effect on the Australian ecosystem. It is directly contributing towards species extinction; making it a critical issue for biodiversity. The agricultural region of Western Australia has lost more species of plants and animals than any other comparable region in the world. Without massive intervention it is projected that up to 50% of remnant vegetation on private land and most of the nature reserves in the wheatbelt which contain wetlands will be lost to salinity. Consequently species loss will continue. Increased salinity could cause the extinction of approximately 450 species of native flora and 250 species of invertebrate water fauna in the western Australian wheatbelt (Australian Government, 2001). The area of salt affected land in Western Australia is increasing at a rate of one football field per hour. In South Australia, low-lying remnant vegetation and wetlands are at risk from rising groundwater. Several areas of high conservation value native vegetation are threatened; they include tea-tree shrublands and native grasslands in the Coorong and Upper South East districts. On Kangaroo Island sedgeland and tea-tree shrublands are also at risk. (Government of S. Australia, 2005)
“The National Land and Water Resources Audit (2001) estimates that the area of land in Australia with a “high potential to develop Dryland salinity” is currently 5.7 million ha and will reach 17 million by the year 2050.” (Pannell, Ewing & Ridley, 2004) Western Australia has undoubtedly the greatest affected area, with 80 percent of the current national total and 50 percent of the 2050 forecast area. Over 30 percent of the land in Western Australia is at risk of being affected by salinity in the year 2050 15 percent of the land is also at risk nationally (Van Bueren & Price, 2004). Scientists are predicting that the water in the Murray Darling River system will exceed the WHO desirable limit for drinking between 2050 and 2100 (Pannell, Ewing & Ridley, 2004).
Dryland salinity can and will cause damage to established infrastructure such as roads, railway lines, and buildings. Operating in damp, saline conditions, railways, vehicles and plant machinery can be damaged prematurely by rusting and corrosion (Government of S. Australia, 2005). It is estimated that by the year 2020 1,260 kilometres of roads in South Australia will be damaged by salinity. In South Australia more than $6 million is spent annually on building repairs and maintenance to fix things caused by salinity. (Government of S. Australia, 2005)
In an effort to maintain and control the spread of salinity, the Commonwealth, State and Territory governments have adopted a National Action Plan for Salinity and Water Quality. 1.4 billion dollars over seven years has been promised to support and help offset the costs of communities and land managers in highly affected catchments (Australian Government, 2001). As a part of the NAP an airborne geophysical survey was conducted in 2002. This survey will provide information on the extent of salt-affected soil up to 100 metres below the surface in key regions in South Australia (Government of S. Australia, 2005). The information gathered from the survey will help to decide what areas of the state should be targeted for corrective action. The National Dryland Salinity Program (NDSP) is a collaborative research, developments and extension program investigating causes of, and solutions to, the national problem of dryland salinity