Land Resources

For the purposes of this Snapshot, ‘Land resources’ as a theme is defined as: All land, soils and landscapes of the South West NRM region that have been modified since European settlement through various forms of land use and development.

It includes all land resources that are used to produce goods of value to humans, including remnant vegetation and agro-forestry on public and private land. The theme area does not include native forests of the region as these are public assets that may or may not have been modified through logging. For more information, view SWCC’s NRM strategy

Consumers are increasingly sourcing locally produced and high-quality food items and Western Australian agriculture is capitalising on this by marketing its products based on a ‘clean, green’ image. As well as its economic contribution, the rural landscape is an important part of the regional identity and the ‘sense of place’.

Despite its tangible value to the economy and society, the landscape and its soils have been fundamentally changed over the past two hundred years through clearing and modification for agriculture. These impacts have contributed significantly to the poor condition of many of the southwest region’s land assets and the issues that threaten them.

Banner photo: Crops Katanning, South Western Australia. Photo: Christian Fletcher

Soil Acidity

Soil acidification is a natural process that is accelerated by agriculture. It is primarily caused through the leaching of nitrates from nitrogen fertiliser and removal of cations. Soil acidity is estimated to cost broadacre agriculture $498 million per year in WA1 or about nine per cent of the average annual crop. It is one of the few soil constraints (particularly subsurface constraints) that can be treated with appropriate management.

Water repellence

Soil water repellence is the resistance of soils to wetting, sometimes to the extent that they remain dry even after significant rainfall events or irrigation. Water repellence is a significant land management issue in the southwest of WA, affecting more than three million hectares of sandy soils in the high and medium rainfall zones. The consequences of water repellence are poor crop and pasture establishment, increased risk of wind and water erosion, and poor water and nutrient use.

Poor Soil Nutrient Management

Nutrients are required for productive agriculture and too little of any nutrient can lead to poor biological growth, reduced agricultural production and a poor economic outcome. Equally, too much of a nutrient can be an economic disadvantage if it is still being applied when enough is already available, and can lead to losses that result in off-site impacts. The direct cost of excess phosphorus application in the agricultural areas of the southwest of WA is estimated to be about $400 million per year.

Soil Salinity

Dryland salinity refers to all soils in non-irrigated areas that have become saline since being cleared for agriculture. There are three basic requirements for dryland salinity to develop: a store of salt, a supply of water and a mechanism to bring both of these into contact with the ground surface. Clearing for agriculture over the last one hundred years and the replacement of perennial, deep-rooted native vegetation with the shallower rooted annual crops and pastures has increased groundwater recharge. More than 1 million hectares of land are affected in the South West. In areas cleared and developed for agriculture after 1960, most water-tables continue to rise, despite a decline in annual rainfall. The cost of lost agricultural production is estimated at $344 million per year.

Plant and animal pests and diseases (biosecurity)

WA agricultural products are renowned as safe, high-quality products and our biosecurity systems ensure this reputation and status is maintained. This biosecurity status confers a significant competitive advantage in overseas markets. Introduced organisms have the capacity to disrupt export and domestic trade of agricultural, forestry, aquaculture and fish products, as well as affect local demand or supply for these products. Such disruptions could have serious effects on the short- or longer-term viability of our food and fibre producers and access to overseas markets as well as our way of life. Effective management of biosecurity risks helps to protect our biodiversity and our distinctive ecosystems and natural environment. Pre-border and border activities include risk assessment, quality assurance, establishing conditions of entry, pre-clearance checks, inspection and compliance activities. Post-border activities include surveillance, monitoring, risk assessment, emergency preparedness and response planning.2

Changing Climate

Climate is the primary factor that influences the performance of the land. Intense summer thunderstorms that occur when the land is bare may lead to catastrophic water erosion.

Climate is not a static factor; it is continually changing, and has always done so, but we need to understand the current climatic conditions and how they are trending to predict current and future condition of the natural resources.

Analysis of climate data over recent decades has demonstrated six key messages relevant to the sustainable and profitable management of our agricultural land:

  • Mean temperatures are rising.
  • Annual rainfall is declining.
  • Autumn and winter rainfall is declining.
  • Spring and summer rainfall is increasing.
  • Projections indicate that these trends will continue.
  • In the short term, year-to-year climate variability may be more important than the longer-term trends.

Additional reading

  • Department of Agriculture and Food (2013). Report card on sustainable natural resource use in agriculture: Status and trends in the agricultural areas of the south west of Western Australia. Department of Agriculture and Food, Western Australia. 188 pages.
  • Department of Agriculture and Food (2016). DAFWA Annual Report 2016. Department of Agriculture and Food, Western Australia. 160 pages.

Case Studies

References

  1. Herbert, A (2009). Opportunity costs of land degradation hazards in South-West Agriculture Region. Resource management technical report 349, Department of Agriculture and Food, Western Australia.
  2.  ‘Western Australian Biosecurity Strategy 2016-2025’, Western Australia Agricultural Authority 2016.