In the last of our series on research in Southern Hemisphere countries, Julia Hinde looks at how salinity is causing a national water supply crisis in Australia. Overleaf we return to South Africa
Australia, the world's driest habitable continent, is facing an environmental disaster - because it has too much water.
More than 2.5 million hectares of the Australian continent are already affected by dryland salinity - with the associated loss of agricultural productivity, the destruction of infrastructure, the salinisation of water supplies and the potential devastation of eco-
At least 80 towns, including the city of Wagga Wagga in New South Wales, are literally being eaten away or dissolved from below by salt; even the western suburbs of Sydney are beginning to show signs of salinisation, with waterways turning saline and roads beginning to erode. Some suggest Adelaide in South Australia has just 15 years of easily obtainable fresh water reserves remaining as the Murray River, which serves the city, becomes increasingly saline.
In 50 years, say scientists, 15 million hectares of Australia could be affected by salinity. Since 1924, when E. W. Wood, a railway department employee from Western Australia, noted that streams dug beside the railways to provide fresh water for the trains' boilers were salinising, Australian scientists have been pondering the problem.
They know why the land is salinising, and by using sophisticated modelling techniques and satellite images to measure the distribution of salt, the height of the water table below the surface and the type of vegetation in an area, they can predict the potential future extent of problems, where they are likely to occur, and estimate their costs.
But now, research being undertaken by state governments, the Commonwealth Scientific and Industrial Research Organisation and universities - to the tune of approximately Aus$40 million (Pounds 16 million) a year - is trying to find solutions - from genetic engineering to water engineering, from new agricultural practices to tax incentives.
"We are our own worst enemies," explains Richard Price, programme manager of the National Dryland Salinity Programme, which was set up in 1993 to co-ordinate research and development in the field of salinity.
"We are a country that is the world's driest inhabited continent, yet our biggest degradation problem is our inappropriate use of what water we have."
Australia's salinity problem, he explains, is the result of changed land use. Native plants were well adapted to use available rainfall, but years of clearing and planting with European crops has upset the delicate water balance.
European agricultural practices and plants, which have been introduced throughout the continent, use less water than native species, allowing more of the water to run below plant roots to the water table, which then rises.
An ancient island continent, Australia has accumulated tiny amounts of salt that have been deposited in rainfall and by wind on the surface over millions of years. Low rainfall levels in some areas, and the transient nature of rivers, means not all the salt has been historically flushed away to sea, rather accumulating in the soil in some areas.
An abundance of water in the soil, since the introduction of new farming methods, has mobilised the salt deposits, leading to today's salinity problems.
"For years the government actively encouraged land clearing and made it compulsory in some cases," says Dr Price. "But for many years, it must have known the results coming out of science and from early observations made by the likes of E. W. Wood. Only in the past ten years, however, have governments really begun to change their philosophies."
Current research, co-ordinated by the programme, has a number of strands. Scientists across Australia are working with farmers on paddock and catchment-scale trials to seek better farming systems that use more of the water, yet are economically viable for farmers.
Considering many of the effects of the land clearing and agricultural practices are not seen on the farms themselves, but sometimes several and even hundreds of kilometres downstream where the salt emerges, it is essential to find economically viable alternatives that advantage the farmer too. In some areas, grazing has been replaced by agroforestry, in other areas fields are being broken up with alleys of trees.
"There's no one solution that can be implemented across a landscape," explains Dr Price, who adds that such research at the landscape scale is very expensive and therefore computer modelling is often used to predict the effects of changed farming methods.
Hydrologists and engineers are also working on engineering solutions, and combining them with agriculture changes. The technology exists to extract salt water from the ground, but then scientists and farmers are faced with what to do with the extracted water.
"Key wetlands of international significance - such as Lake Toolibin in Western Australia - are salinising at a rate that means you must either intervene now with engineering solutions or you can do nothing," explains Tom Hatton, programme leader at CSIRO Land and Water in Perth.
"This is a site of enormous biodiversity with lots of endemics. They are looking at engineering solutions, ground-water pumping and disposing of the water in lakes where it can evaporate."
Dr Hatton believes salinisation is happening over such a large area that inevitably considerable quantities of land will be lost to the salt. "I think we will have to be selective," he says.
Hence scientists are also looking for viable ways of working salinised land, including the introduction of salt-resistant crops or even saline aquaculture. Plant breeding and genetic engineering techniques are being used to breed better salt tolerance, while salt-resistant crops are being sought worldwide.
More recently, researchers have turned their attention to understanding what kind of social and political operating environments are needed to promote the agricultural changes that are necessary.
"Researchers are looking at how you would need to change the institutions to effect change in the landscape," explains Dr Hatton. This could include tax incentives to induce certain practices. It brings economists, social scientists and policy experts to what was initially a scientific problem.
After years of ignoring the salinity problem, or believing it to be just a problem for agriculture, Australia, says Dr Price, is beginning to wake up to its salinity crisis.
"It's not agriculture that's driving the salinity debate any more," he says. "Now towns and roads are at risk; houses across Australia are crumbling from salt. In the next ten to 15 years it will start chewing up the heritage buildings and houses of western Sydney, then Australia will truly wake up to the scale of its problem."