Wind erosion in south-west Western Australia

Page last updated: Friday, 22 November 2019 - 3:18pm

Please note: This content may be out of date and is currently under review.

Wind erosion is a natural process that has shaped the ancient Australian landscape. However, wind erosion is increased by several agricultural practices. Wind erosion damage can be cumulative, and have short-term and long-term costs, for the individual farms and for the larger community.

The Department of Primary Industries and Regional Development provides this information to help decrease the incidence of wind erosion in Western Australia.

Why south-west agriculture is particularly susceptible to wind erosion

The south-west of Western Australia (WA) has a Mediterranean climate (hot dry summers and cool wet winters) which largely favours annual broadacre cropping, ancient sandy surfaced soils, and erosive winds during the driest times of the year. Each of these factors contribute to WA's susceptibility to wind erosion.

Climate variability plays an important role in predisposing whole landscapes to wind erosion. In dry seasons, there can be significant areas of poor pasture and crop production, which provide less than adequate ground cover over the dry summer.

Climate change in south-west Western Australia is expressed as lower rainfall, higher temperatures, and later starts to the growing season. These factors increase the risk of wind erosion. See Climate trends in WA and Climate projections for WA for more detail.

Status and trend of wind erosion in the agricultural areas of Western Australia (WA)

  • Wind erosion is a seasonal hazard in the south-west of WA.
  • The indicator used for wind erosion hazard is erodibility – the potential for soil loss in erosive winds.
  • More than half of the agricultural land had unacceptable hazard ratings (were below target values) at least one year in four during the period 2009–12.
  • The Central Northern Wheatbelt Ag Soil Zone had the greatest hazard, with the zone being below target values in each of the four years 2009–12.
  • Wind erosion hazard at the state level has reduced over time because of changed cropping and stubble management practices.

Management implications

  • Current land use practices still result in some degree of wind erosion, with an estimated cost of $50–71 million per year.
  • Increasing the use of stable ground cover (including living and dead vegetation and gravels) to prevent loss of soil, fine particles, nutrients and soil organic carbon is a practical and profitable option.
  • Climate variability and a drying climate will increase the risk of wind erosion in the current agricultural system.

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Conditions needed for wind erosion to occur

For wind erosion to occur, three conditions need to be met:

  • an erodible soil surface – disturbed or detached soil with few obstructions
  • an exposed soil surface – wind must be able to reach the soil surface
  • erosive winds – wind speeds of greater than 28 kilometres per hour are needed to move soil particles and lift dust for significant distances.

In the agricultural areas and farming practices of south-west Western Australia, all three conditions are met at some times in some places each year.

WA soils and the impact of wind erosion

Western Australian soils generally have low inherent soil fertility and high susceptibility to wind erosion. We have estimated that  6.4 million hectares (ha) of agricultural land in WA is at risk of wind erosion – 0.02 million ha at extreme risk, 0.9 million ha at very high risk and 5.5 million ha at high risk (Figure 1).

Map of south-west Western Australia showing areas of high, very high or extreme susceptibility to wind erosion
Figure 1 Areas of high, very high or extreme susceptibility to wind erosion in the south west of Western Australia

Many WA soils have a sandy surface with limited finer fractions. Wind erosion removes the finer fractions from the soil, which includes the clay, organic matter and soil nutrients. The loss of these particles reduces the water and nutrient holding capacity of the soil and hence soil fertility.

For every 3% of the nitrogen that is removed from the soil, there is a 2% loss in yield of the following crop. If the top 10mm of soil are subjected to winnowing by the wind, crop yields may be reduced by 25%.

Additional fertiliser applications will increase the soil fertility, but the soil may not return to its original productivity, because of the loss of smaller particles which retain most of the nutrients. Other on-site impacts include the deposition of sand on fence lines and in waterways and dams. This requires time and resources to remove.

Managing wind erosion in Western Australia

There are technologies and management systems that can reduce or prevent the risk of wind erosion, and to stabilise and rehabilitate eroded areas. See Managing wind erosion in southern Western Australia for more details.

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Resource condition target for wind erosion

Note that these targets and the likelihood ratings do not indicate actual wind erosion – they estimate the likelihood of erosion if erosive winds occur.

We have six ratings of erosion likelihood of a site, and group these as either 'acceptable' or 'unacceptable' (Table1).

Table 1 Likelihood ratings of wind erosion
Rating Physical characteristics Likelihood class
Safe No wind erosion likely and ground surface unlikely to be affected. Acceptable
Negligible Wind erosion unlikely although some minor dust is possible. Ground surface likely to remain intact. Acceptable
Low Dust and minor soil movement is likely although ground surface will probably remain unchanged. Acceptable
Moderate Dust and some sand movement and the start of ground surface particle sorting likely. Unacceptable
High Widespread dust and soil movement and rippling of ground surface likely. Unacceptable
Very high Widespread dust and sand movement and deep deflation (hollowing out) of soil surface likely. Unacceptable

For the long-term sustainability of the soil resource, we consider that less than 5% of the landscape should be in the unacceptable likelihood class each year, with the aspirational aim of less than 3% of the landscape being in an unacceptable likelihood class (Table 2).

Table 2 Hazard and target criteria for the south-west agricultural soils
Target Hazard Criteria
Above target Very low <1% of the landscape in an unacceptable likelihood class
Above target Low 1–3% of the landscape in an unacceptable likelihood class
Above target Moderate 3–5% of the landscape in an unacceptable likelihood class
Below target High 5–10% of the landscape in an unacceptable likelihood class
Below target Very high >10% of the landscape in an unacceptable likelihood class

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Department of Agriculture and Food 2013, Report card on sustainable natural resource use in agriculture: Wind erosion, Department of Agriculture and Food, Western Australia

Department of Agriculture and Food, Western Australia 2014, Investing in sustainable resource use – reference metrics: a companion to the Report card on sustainable natural resource use in agriculture, Department of Agriculture and Food, Western Australia, Perth.

van Gool, D, Vernon, l & Runge, W, 2008, Land resources in the South-West Agricultural Region: a shire-based summary of land degradation and land capability, Resource Management Technical Report 330, Department of Agriculture and Food, Western Australia.

Contact information

Justin Laycock
+61 (0)8 9892 8407
Paul Findlater
+61 (0)8 9956 8535