Salinisation is the build-up of salt within the soil. It is one of the greatest environmental threats facing Australia today. Salinisation could devastate up to 12 million hectares of land during the coming century and already costs us at least $500 million a year in Victoria alone.
Salinisation occurs when salt gets moved around and concentrated in the soil. Because salt dissolves, it is moved around with water. As water evaporates, it leaves the salt behind in the surface layers of the soil. If this process continues long enough, the concentration of salt becomes too high for most plants and they die.
Salt is already present in our soil because much of Australia was once covered by the sea. However, the vast majority of the salinisation in Australia is due to humans altering the way water moves through the environment. This is done through irrigation, causing irrigation salinisation, and through altering vegetation, which results in dryland salinisation. Artificial fertilisers can also add salt to soils.
Irrigation salinisation is caused by excess water from irrigation which raises the water table, bringing salt to the surface. Irrigation salinisation can be reduced by using less water on crops and by growing crops which require less irrigation.
Dryland salinisation occurs because much of Australia has been cleared for agriculture and the introduced crops use less water than the native vegetation they have replaced. This results in more water seeping down through the soil to join the existing groundwater, which causes the watertable and the salt to rise. Replanting cleared areas with trees and deep rooted grasses is often used to lower rising watertables. However, replanting must take place over large areas to have a significant impact on ground waters.
Salinisation of land is one of the major environmental crises facing Australia. If we cannot control the spread of salinisation and reclaim lands already salted, the costs, both economic and environmental, will remain a substantial burden on future generations.
Greg Gowing
Terrestrial Ecology
Australian Museum
Copyright © Australian Museum, 2003
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