Dryland salinity is a significant cost to agriculture and infrastructure, and a major risk to water resources and biodiversity. It is estimated that between 1 and 2 million hectares of land within the agricultural regions is salt affected and that the opportunity cost of lost agricultural production alone is $519 million a year. Salinity also damages infrastructure, adding further costs, impacts water resources and reduces biodiversity. Without some level of intervention, dryland salinity will continue to be a significant cost and major risk to the State.

Agencies expect the extent of salinity affected land in the South West to more than double over the next 50 to 100 years to around 5.4 million hectares. Of this, 4.5 million hectares is agricultural land.

There are approximately 18 million hectares of agricultural land in the South West. If the upper estimate of 4.5 million hectares became salinity affected that would equate to 25% of agricultural land and could potentially cost around $1 billion a year in lost production (2016 estimated opportunity cost x2).

DWER estimates that almost every stream and river in the South West is affected by salinity. When salt levels exceed Australian Drinking Water Guidelines of 500mg per litre it can be harmful to health. As salt concentrations increase the potential uses for the water diminish.

High concentrations of salt are harmful to most plants and animals. In 2010, the then Department of Environment and Conservation estimated that 850 endemic flora and fauna species were at threat of extinction as a result of dryland salinity. The threat to the State’s biodiversity is not limited to individual species. DBCA advise that all the remaining remnants of many valley-floor communities (wetlands, shrublands and woodlands), along with their soils could disappear because of salinisation.

Under the Natural Diversity Recovery Catchment Program, DBCA manages 2 key catchments so they are protected for the long term. Expenditure for activities related to overall dryland salinity management are not separated and reported.

Salt also damages infrastructure owned by State, local government and the private sector which can increase maintenance costs and reduce the life of an asset. Infrastructure includes roads (main, regional and local) and railways, local government assets, private houses and buildings.

The cost and impact on infrastructure assets is not accurately known, but local governments estimate salinity can halve the life of roads. In 2006, the Salinity Investment Framework Phase II[1] report stated that about 252 kilometres of highways and main roads, and 3,850 kilometres of local roads were affected by salinity. The annual costs of repairs were approximately $175 million a year. It was estimated that 210 kilometres of rail line and potentially another 1,050 kilometres could be affected by salinity with an annual repair cost of $2 million and $7 million respectively.

Local governments that we spoke to said salinity did impact their roads and assets such as parks, reserves and buildings but were not able to separately identify the financial impacts. Where the local governments operated town site bores to lower water tables, they were able to provide ballpark calculations of operational costs for the pumps. All other expenditure is included within operational costs.

There is no practical way of calculating the cost of salinity on private assets such as houses and buildings. Anecdotally we were told of extensive repairs needed to some houses in Narrogin, Wagin and Katanning.

[1] Salinity Investment Framework, Phase II, Natural Resource Management, December 2006

The scale and costs of intervention could be very large, and government needs to decide what is feasible and economically viable

The South West agricultural area is poorly drained, is particularly flat in the eastern parts and has wide valley floors. For large scale improvements, DPIRD estimates that over 80% of the Wheatbelt would need to be replanted with deep rooted trees and shrubs to stabilise and lower water tables. Water tables would take decades to fall and the current extent of broad scale agriculture would no longer be possible.

Agencies advise that recovery from dryland salinity is only feasible in discrete catchments and they have focused efforts on individual assets that warrant protection. On a landscape scale, more achievable and feasible management goals are to contain the area impacted or adapt to the saline conditions. Options include revegetation, drainage systems, planting salt tolerant plant species or adoption of alternative land uses. The choice for government is to decide how much intervention is feasible and economically sound.