The influence of farm landscape shape on the impact and management of dryland salinity

This paper examines how a farmʹs landscape shape and its distribution of soils affects the impacts of dryland salinity. Three farm landscape shapes, subject to gradual salinisation, are described. The way in which the farm landscape influences the spread of dryland salinity is explored. Where soils are homogeneous, a linear plane landscape and a spherical basin landscape provide no additional incentive for salinity abatement or containment. In such landscapes the incentive to manage the onset of salinity chiefly comes from the size of the profit difference between land use on salinised versus unsalinised land, the cost and technical feasibility of reducing recharge and the farmerʹs time preference for money. By contrast, where the landscape is like a cylindrical segment, and where soils are homogeneous, then the landscape shape does provide an additional incentive for salinity abatement or containment. Using farm modeling for a study region in Western Australia the paper discusses the farm management and environmental ramifications of findings about the role of landscape shape and soil distribution in affecting the onset and spread of dryland salinity. Non-linearities in profit impacts due to landscape shape, soil gradients and a time preference for money suggest there is often an incentive to act sooner rather than later in slowing the spread of dryland salinity.