By Phil Mercer BBC correspondent in Sydney

Water supplies are in crisis in parts of Australia

The report by the Australian Climate Group says an increase in the average temperature of just one or two degrees Celsius could devastate farmland.

It says the solution is to cut greenhouse gases by 60% by 2050.

Australia, which has one the world's highest gas emissions on a per capita basis, has not ratified the Kyoto Protocol on climate change.

'Unacceptable' plans

The ACG - an alliance of conservationists, scientists and economists - sees this vast continent becoming a land increasingly at the mercy of natural disasters such as floods, droughts and cyclones.

Its report claims that an increase in the average temperature by just few degrees could trigger serious economic losses.

There are fears that other drought-prone regions in the Southern Hemisphere - including parts of Africa - could suffer similar problems if emissions remain unchecked.

The study has insisted that water shortages in Australia are clearly linked to global warming. But Australia's plans to confront these challenges are described as "unacceptable".

'Meaningless' without US

The government has insisted it has a responsible, long-term strategy.

But Prime Minister John Howard believes that ratifying the Kyoto Protocol on climate change would cost jobs and damage industry.

Mr Howard said the global agreement would be meaningless without the support of the United States, which has also rejected it.

Australia has said it is meeting its international obligations on emissions while still achieving strong economic growth.