Soil erosion is the removal of soil particles from one place to another via the movement of wind or water. It is a natural process that is greatly enhanced by human activities; this acceleration makes it one of the greatest threats to soil function globally as soil is essentially a non-renewable resource (ITPS 2015, Metcalfe and Bui 2017). It is particularly of concern in Australia where soil formation rates are well below the global average (Bui et al. 2010, Metcalfe and Bui 2017). The loss of topsoils and exposure of subsoils results in reduced agricultural productivity and health of native vegetation (WA EPA 2007). Soil movement can also undermine infrastructure, fill drains, and contaminate water supplies and inland waters (WA EPA 2007). Severe erosion leads to a loss of soil functional capability. The loss of organic carbon and other topsoil resources due to wind and water erosion are significant causes of soil condition decline over time (Tozer and Leys 2013, NSW EPA 2015).
Globally, soil water erosion transports 23 to 42 million tonnes of N and 15 to 26 million tonnes of P off agricultural land, often causing eutrophication of waterways receiving nutrient rich sediments (ITPS 2015). Replacing these nutrients costs an estimated $33-60 billion USD for N and $77-$140 billion USD for P (ITPS 2015). In catchments flowing to the Great Barrier Reef, the waters contain 5 times as much sediment, 2 times as much nitrogen, and 3 times as much phosphorus compared to pre-development conditions (Waterhouse et al. 2017). In addition, the 2015 rate of crop yield losses per annum due to soil erosion was 0.3% (more than 10 million hectares per year); if this rate continues, a 10% loss of potential crop yield would occur by 2050 (NCST 2013, ITPS 2015). The cost of soil erosion within Australia is difficult to quantify but undoubtedly substantial, particularly as up to 10 million hectares of land have less than 500 years until the soil’s A horizon (generally the most productive/valuable layer) will be lost (WA EPA 2007, Bui et al. 2010, Metcalfe and Bui 2017, Waterhouse et al. 2017). The cost of dust storms in New South Wales alone is estimated at $9 million AUD per year (Tozer and Leys 2013).
Soil erosion can be prevented by maintaining adequate groundcover, protecting soil from particle detachment and transport. Climatic variation is a major concern for erosion management however, as erosion risk is determined by climate and vegetation interactions; drought, climate change, fire, and severe weather events all contribute to increased erosion risk (Metcalfe and Bui 2017, WA DAF 2017, VIC EPA 2018). Conservation agricultural practices are a key preventative measure for soil erosion, and are increasing in Australia (Metcalfe and Bui 2017); however, adoption rates are low or have decreased in some key Murray-Darling Basin catchments (Metcalfe and Bui 2017). As such, current rates of soil erosion by water across much of Australia continues to exceed soil formation rates even though there is an improving trend in erosion management through improved land management practices (ITPS 2015, Metcalfe and Bui 2017).
Strategies to prevent erosion often present an opportunity to improve soil condition and therefore soil sustainability. Promoting vegetation leads to an increase in soil organic matter, which can improve soil structure and therefore soil nutrient content and water holding capacity. A significant challenge facing erosion prevention however is the scale at which most prevention activities occur; that is, most prevention takes place at the landholder scale. Social and economic pressures on landholders can prevent the activities that might lead to effective erosion prevention.
Bui, E. N., G. Hancock, A. Chappell, and L. J. Gregory. 2010. Evaluation of tolerable erosion rates and time to critical topsoil loss in Australia. CSIRO, Canberra.
ITPS. 2015. Status of the world’s soil resources technical summary. FAO – Intergovernmental Technical Panel on Soils, Italy.
Metcalfe, D. J., and E. N. Bui. 2017. Australia state of the environment 2016: land. Australian Government Department of the Environment and Energy, Canberra.
NCST. 2013. Establishing the Australian Soil Assessment Program (ASAP).
NSW EPA. 2015. New South Wales State of the Environment 2015. New South Wales Environment Protection Authority, Sydney.
Tozer, P., and J. Leys. 2013. Dust storms – What do they really cost? Rangeland Journal 35:131-142.
VIC EPA. 2018. Victorian State of the Environment 2018 scientific assessments. Authorised by the Commissioner for Environmental Sustainability, Melbourne.
WA DAF. 2017. Report card on sustainable natural resource use in the rangelands: status and trend in the pastoral rangelands of Western Australia. Department of Agriculture and Food, Western Australia, Perth.
WA EPA. 2007. State of the Environment Report: Western Australia 2007. Perth.
Waterhouse, J., B. Schaffelke, R. Bartley, R. Eberhard, J. Brodie, M. Star, P. Thorburn, J. Rolfe, M. Ronan, B. Taylor, and F. Kroon. 2017. 2017 scientific consensus statement – land use impacts on gret Barrier Reef water quality and ecosystem condition. Queensland.
Soil Science Australia acknowledges the traditional owners of the land and pays its respects to their Elders, past, present and future.