About 2 million hectares of agricultural land in southern Western Australia is already affected by salinity, and a further 4 million hectares is threatened.
The fundamental cause of salinity is the replacement of perennial, deep rooted native vegetation with the annual crops and pastures used in agriculture. Salinity is usually noticed first when plants grow poorly, and yields of farm plants (crops and pastures) are reduced by more than 25 to 30%. In severe cases, bare or 'weedy' patches develop with salt obvious on the surface. These patches are known as 'salt scalds'.
Trees can prevent saline ground water rising to the surface, where its effect on agricultural production and nature conservation is disastrous.