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
vegetation for seeding. The combination of these practices have led to a rise in the underground water table, pushing salts stored in the soil closer to the surface. (A) It is in this way that agricultural practices in the wheat belt have unwittingly contributed to the salinization of the area. The result of this is that the wheatbelt accounts for 70% of Australian inland salinity (A, B) Groundwater tables in the wheat belt are estimated to be rising between 0/5-1.0m per year. The secondary salinization effect on these wheat belt areas has resulted in a significant number of wetlands and rivers becoming more saline. (E) It is estimated that over one million hectares of previously viable farmland in the wheat belt is now affected by salinity. (D)
Salinisation is highly detrimental to the wetland ecosystem, greatly affecting freshwater macro-invertebrate species. Small changes to the salt levels can have a significant impact on macro-invertebrate richness. (A) The salinity levels tolerated by eggs and larval stages of many macro-invertebrates can be much lower than that of their adult forms. (C)

Lit review
The threat to wheatbelt biodiversity due to salinity is being heavily researched across multiple disciplines, primarily to sustain agriculture but will hopefully lead to innovative technical solutions to also protect biodiversity.
(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)
Salinisation poses one of the biggest threats to river and wetland ecosystems, causing irreversible damage.
(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.

This
study
New approaches to assess and understand what is going in with salinity and macro-invertebrates is needed to improve management and repair strategies.(A) One third of freshwater macro-invertebrates are at risk of extinction from the wheatbelt area over the next 100 years. Present level of biodiversity can only be maintained if a significant number of clean water bodies remain.(B) A number of biological and engineering options can be used to decrease salinity. (D) Studies of change over time are not very common, especially in regards to secondary salinization.(E) This purpose of this study was to measure macro-invertebrates richness over a longer period of time, in relativity to rainfall and salinity.