08-16-2017, 10:53 PM
Wind erosion
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Wind erosion is a common cause of land degradation in the arid and semi arid grazing lands of inland Queensland. It is one of the processes leading to desertification. Significant wind erosion occurs when strong winds blow over light-textured soils that have been heavily grazed during periods of drought.
Wind erosion is also a natural process. The large parallel sand dunes in south-west Queensland, including the Simpson Desert National Park, are the result of wind erosion and deposition over thousands of years. These dunes are constantly moving and roads and tracks can be covered by drifting sands in only a few hours.
Contributing factors
Overgrazing by livestock is a prime cause of wind erosion. Grazing pressure can also occur from kangaroos and wallabies, as well as feral animals such as rabbits, goats and camels.
Periods of drought associated with a negative Southern Oscillation Index (SOI) provide the highest levels of wind erosion activity. The hotter and drier conditions predicted under climate change scenarios would exacerbate the problem.
The breakdown of the biological soil crust, which is a characteristic of many arid zone soils, makes soils susceptible to wind erosion. This living crust incorporates algae, lichens, mosses and liverworts and protects the soil from all forms of soil erosion. Crust cover can take many years to recover once damaged.
Areas affected by wind erosion
The lighter textured soils (sands and loams) in the low rainfall lands of Queensland s south-west are the most susceptible to wind erosion. Average annual rainfall in this area is between 150 and 500 millimetres (mm).
Wind erosion is generally not a serious issue in the two per cent of Queensland that is used for cropping. This area is located in higher rainfall areas and most of the soils are well-structured clays. The relatively large aggregates formed by clays are too coarse to become airborne. However cultivated sandy and red loamy soils are susceptible to wind erosion when they have no cover and are in a dry, finely worked condition.
Sources of air borne materials
Soils are made up of particles of sand, silt and clay. Individual soil particles generally need to be less than one mm in order to be moved by wind. Individual clay particles have an average diameter of only 0.001 mm but they usually clump together in aggregates that are too heavy to be moved by wind. Non-aggregated particles of sand, silt, clay and organic matter are most susceptible to removal by wind erosion.
Control measures
The most effective method of controlling erosion by both wind and water is to maintain adequate levels of cover on the soil surface. To achieve this on grazing lands, stock numbers need to be managed to match the current and expected seasonal conditions. Graziers have to make regular decisions about how many animals they should run on a piece of land taking into account the added impact of native herbivores and feral animals.