Wheatbelt Salinization

Overview
Australia has a large number of shallow salt wetlands which occur naturally in arid and semi-arid regions of inland Australia. Many of these occur naturally due to the high evaporation rates and atmospheric accession of salt. There are, however, a rapidly increasing amount of saline wetlands occurring due to secondary salinization. This salinisation is resulting in the loss of freshwater macro-invertebrate species. (A)
Specific descript of issue
Land management practices for the purpose of agriculture in the aptly named “wheatbelt” of Western Australia have led to the secondary salinization of many rivers, streams and wetlands. Secondary salinization can be caused by both extensive crop irrigation and by clearing of deep rooted native
(B) Channel drains were implemented in some areas to try to reduce agricultural salinity but the ecological effects for the discharge sites were not considered, resulting in great change in the macro-invertebrate species richness and composition at these sites. (D) Studies show that further salinization of the wheatbelt will reduce the richness of some species, some to the point of extinction.
(E) Macro-invertebrates are sensitive indicators of increased salinity in an environment and can provide early warning signs of changing aquatic habits. (F) They are widely researched as indicators of the health of particular waterways. (H)
On a human scale, higher salinity levels can also increase population numbers of the mosquito responsible for Ross River Virus. This species thrive in an environment with less macro-invertebrate predators who cannot tolerate the higher salt percentage. Maintaining species diversity can reduce disease risk. (G)

Gap in the knowledge
The impact of secondary salinization in agricultural terms is well documented, however the true, long-term impacts on wetland ecosystems is poorly documented. (A) . (E) found that 46% of the 752 freshwater macro-invertebrates occur at least once in the 144 saline wetlands (>3g/L-) around the wheatbelt of WA. In contrast to these figures, saline lakes in Victoria and South Australia were reported to have a very small percentage of freshwater species in parallel conditions. (E) Further research is required to discover how the WA macro-invertebrates have adapted to thrive more efficiently in saline conditions.

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