The BBC's correspondent in Australia, Michael Peschardt, says widespread deforestation has caused the water table to rise, lifting thousands of tons of salt into the top soil.
Nothing can grow in the resulting desert.
Since white settlement of Australia started in the 18th century an estimated 15 billion trees have been cut down to make way for farms or urban development. The trees held the rising water levels in check, their roots sucking up millions of gallons of water which then evaporated in the hot sun. Trees must be planted' Land may never recover The council says only a massive tree replanting programme can reverse the process because agricultural crops do not suck up enough water. But farmers are still felling trees. Every year hundreds of acres lose their protection against the saline menace lurking beneath the surface.