Schools For a Sustainable Future

Story

Not so green, less than clean
Salinity
by Claire Miller
Environmental Reporter

Salinity is Australia's most serious environmental threat. Once thought to be a distant rural problem, rising salt is now eroding roads and buildings in major towns and creeping into the western suburbs of Sydney.

Salinity is caused when the amount of water absorbed by vegetation is disrupted by clearing and irrigation. Removing deep-rooted native vegetation increases the volume of water soaking into the soil. This causes the water table to rise, bringing salt which concentrates on the surface as the water evaporates. Irrigation exacerbates the process.

Australian geology is naturally high in salt because much of the continent was once an inland sea. It also has low but highly variable rainfall. Native vegetation adapted to absorb all available surface moisture, thereby keeping water tables low. But now it is largely cleared, 10 times the former amount of water is soaking in, raising water tables and salt-poisoning the land and rivers.

The scale of the threat is huge. The Commonwealth Scientific and Industrial Research Organisation (CSIRO) says 2.5 million hectares of Australia is now salt affected, and that area is likely to increase six-fold over the next 50 years. Salt levels in the Murray River, Adelaide's water supply, are expected to exceed safe drinking levels by 2020. As well as arable farmland, salinity is wiping out remnants of native vegetation, accelerating the slide to extinction.

The creeping crisis is eating away at Australia's economic advantage as a cheap food exporter, and stretching public finances for roads and other infrastructure. Salt affects up to 30 per cent of regional roads, with major highway reconstruction costing up to $1 million per kilometre. Lost agricultural productivity is $130 million a year and rising; the overall economic impact of land and water degradation is valued at $2 billion a year.

Stemming the salinity tide means putting an end to landclearing and revegetating up to 80 per cent of catchment areas. This would have substantial economic and social ramifications in target regions but would also benefit property owners, towns and cities hundreds of kilometres downstream where the rising water tables break the surface.

The CSIRO's Dr Graham Harris has estimated that the cost of fixing Australia's land and water degradation has probably outstripped the $37 billion annual value of agricultural production. It means agriculture is uneconomic as well as unsustainable once the environmental costs are factored in. But abandoning agriculture is not an option since not only do we have to eat, but Australia is one of the few food exporting nations in an increasingly hungry world.

An economic analysis commissioned by the Australian Conservation Foundation and the National Farmers Federation this year estimated it would cost $65 billion over 10 years to fix the problems, put agriculture on a sustainable footing and save species from extinction. The ACF and the NFF proposed the cost be shared between government and the corporate sector.

The Commonwealth Government responded last month with a $700 million plan over the next 10 years, provided the states agree to put in a matching amount.

Green     Biodiversity Loss    Landclearing Logging    Water
Global Warming    Further Reading - Websites    

The Age Publication
1st November 2000