AUSTRALIA'S planned population explosion will place unprecedented pressure on strained water supplies and radically change the daily lives of average citizens, experts warn.

Both state and federal political leaders plan to almost double the population in the coming decades despite calls from a growing number of academics and activists who question whether the pace can be maintained.

Australian Bureau of Statistics figures released yesterday show the nation's population has passed the 22 million mark, and Prime Minister Kevin Rudd is advocating smashing the 35 million barrier by 2050.

Premier Mike Rann spent much of the recent election campaign boasting South Australia had been transformed from a "rust bucket state" into one that attracts new residents in large numbers.

He has plans to swell the population of greater Adelaide by 560,000 before 2040 as a key measure to underpin long-term economic growth. This has won backing from the Opposition and the state's business lobby.

But Sustainable Population Australia president Sandra Kanck yesterday said the nation had failed to come to grips with the full implications of a reform agenda she said would push natural resources to breaking point.

"It is crazy to be welcoming these sorts of numbers when we have no plan of how to deal with them," she told The Advertiser.

"We are the driest state in the driest continent and that is something that should make our decision-makers pause and reflect.

"We are living with that as the starting point, knowing with climate change it's only going to get worse."

Ms Kanck said the increase in housing needed to accommodate new residents would also spell the death of the backyard for many families and destroy some of the best agricultural land in the state.

"If the Government is intent on growing the population, people have to realise this can only happen with a reduction in our standard of living," she said.

Business leaders are sounding their own warnings and say the looming mass retirement of baby boomers will leave a black hole in the workforce that must be filled.

Business SA chief executive Peter Vaughan said population growth increased vibrancy and innovation and was especially important as SA stood on the cusp of a mining boom.

"This state desperately needs critical mass in order to remain competitive in Australia," he said. "Skilled is a pre-requisite, but also young, of a marriageable age and preferably with children. They are the ones who will stay and not head off to the bright lights of Sydney and Melbourne.

"It also allows us to use our domestic market to offset the vagaries of our export market when the dollar is going against us."

Mr Vaughan said the number of working Australians supporting each welfare recipient had shrunk from 22 to five since 1965.

He said SA faced an especially large shock as it grappled with the oldest population over 60 and the youngest under 30 in the nation.

"If we (do) not get population growth in this state there will be no one to fund and support the growing older population," he said.

UNIVERSITY of Adelaide demographer Professor Graeme Hugo said Australia had not had an educated debate on population growth and called for an inquiry the likes of which has not been seen since 1971.

"We do have to have growth, there's no question about that, but at the same time not compromise our goal to move towards a sustainable environmental situation," he said.

"The two sides are more or less talking past each other. We've got a separate environmental policy and a separate population policy. What we need to do in Australia is to bring those two things together.

"What I'm calling for is the possibility of having growth with sustainability. To do that, we have to look at what trade-offs and compromises are needed."

PROFESSOR Hugo pointed to Japan's declining population as evidence growth need not continue exponentially. He said the ideal population would be stable in overall number and include an even mix of younger workers and older retirees.

He said a population inquiry would deliver scientific data that could be used to determine a sustainable total which would be maintained through a drawdown in overseas migration.

Yesterday's ABS figures reveal a 1.3 per cent growth in SA's population in the 12 months to September. A spokesman for the Urban Development and Planning Minister Paul Holloway said the data showed an increase above that forecast in the short-term targets for the Government's 30-Year Plan.

The spokesman made clear the plan was open to review should demand or circumstances change. "South Australia's population growth will no doubt vary from quarter to quarter but at this early stage we remain on track to reach the targets set out in the plan," he said.

"The 30-Year Plan will be regularly reviewed to ensure the targets and policies are adapted in line with any changes in demographic trends."

The global population began surging after industrialisation and is tipped to peak at about nine billion.

Originally published as Is bigger really better?