Agents of Change Salinity in Australia

Essay by 512High School, 11th gradeA, June 2008

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The increase in salinity is becoming one of the most significant environmental problems in Australia. It is destroying the Australian landscapes and is a serious threat to our native species and functioning ecosystems as well has having a major impact on species diversity. Although salinity occurs, to some extent, naturally in some areas, the problem is being increased by some farming practices.

There are two types of soil salinity, dryland (occurring on areas of land not exposed to irrigation farming) and irrigation salinity. Both describe areas where the soil contains high levels of salt. Usually, plants and soil organisms are killed or their productivity is severely limited on salinity affected lands.

What has caused the problemSalt has been accumulating underground in Australia for thousands of years and up until a few hundred years ago, it wasn’t a problem.

Native Australian vegetation evolved to be salt-tolerant, with deep root systems.

While the ecosystems were in balance, the salt remained underground. But after European farming methods arrived and cleared the lands of native vegetation replacing it with shallow-rooted annual crops and pastures whose roots did not penetrate as far into the ground, the system became unbalanced.

The shallow root system causes excess water to leak from the root zone into the underground water systems each rainfall. The increased amount of water entering the watertables cause the level to rise, mobilizing the underground salt band and bringing the salts to the root zones or the surface, or into lakes, wetlands and rivers etc. (see pic.)Salinity can also occur when the volume of irrigation water exceeds evaporation and transpiration by plants. This increases the water draining underground causing the watertables to rise, which then carries the salts to surface bringing the same consequences as with the land clearing. Evaporation leaves these salts to...