Irrigated by one of the world's mightiest river systems, the Murray-Darling Basin yields almost half of Australia's fresh produce. But the basin is ailing and scientists fear that as climate change grips the driest inhabited continent its main food bowl could become a global warming ground zero.

The signs are ominous. In the Riverland, one of the nation's major horticulture areas, dying vines and parched lemon trees attest to critical water shortages.

Farmers have had their water allocations slashed during the recent crippling drought; 200 sold up and many of those who hung on are struggling.

In Renmark, the region's oldest town, some families have spent their life savings, others are drowning in debt.

Since the 1880s, when Europeans settled in the Riverland, fruit and vegetable producers have depended on the broad Murray River. However, the river is in a sorry state, and this once lush area - at the southern end of the sprawling Murray-Darling Basin - faces a bleak future.

The picture is similar across the million-sq m basin, which consists of vast inland plains crisscrossed by the Murray, Darling and numerous other rivers and tributaries.

The past half-century has witnessed an enormous - and officially sanctioned - over-extraction of water. The river system, which straddles four states and one territory, has been badly mismanaged. Falling commodity prices - and a glut of wine grapes - have exacerbated farmers' woes.

But it was the decade-long drought, the worst for more than a century, that tipped the balance. It also brought the basin's plight to public attention, with its images of skeletal cattle in cracked, brown paddocks and broad waterways reduced to muddy trickles.

And such spectacles, scientists say, will become increasingly common in Australia as the planet heats up.

According to the country's Department of Climate Change, global warming will trigger more frequent and severe droughts, as well as more devastating bushfires, cyclones and floods. The Government's main scientific body, the Commonwealth Scientific and Industrial Research Organisation, says there is growing evidence that lower rainfall in south-eastern Australia is linked to global climate change.

Anne Henderson-Sellers, a research fellow at Sydney's Macquarie University and a former director of the United Nations' World Climate Research Programme, says: "Global warming is going to have an extraordinarily detrimental effect on us, more than on any other developed nation."

The challenges facing Australia include managing scarce water resources at a time of rapid population growth and ensuring food security in a continent with only six per cent arable land.

The Government's climate change advisers have warned that agricultural production there could fall by 92 per cent by 2100. Now the basin has become a political tug-of-war.

Labor and the Liberal Party have promised millions of dollars to restore the river system - and the wetlands at the mouth of the Murray - to health. Climate change, though, has barely rated a mention.

Garry Hera-Singh lives at Meningie, on the banks of Lake Albert, and has fished commercially all his life.

The area where he catches fish has shrunk by two-thirds. The remaining waters are up to five to seven times saltier than the sea.

"The whole ecosystem is on life support. Salinity is gradually engulfing it, like a cancer," he says.

He is cynical about the latest political promises. "They should have done something a long time ago instead of waiting until communities were brought to their knees."

- INDEPENDENT