Perth to absorb 2 million more

Perth will sprawl further than New York City, be clogged with cars and people will live in each other's pockets as the city groans under the weight of an extra two million residents over the next 40 years.

An analysis of how Perth is growing and will grow as more people call the city home also warns that more desalination plants, thousands of kilometres of roads and hundreds of schools will have to be built to cope with the surge in residents.

POLL: Can Perth cope? Have your say

The Australian Bureau of Statistics is forecasting Perth's population to hit 3.8 million from its current 1.7 million by 2050.

For the first time the bureau has looked at what that will mean to Perth residents - and the picture is dominated by sprawling suburbs and long journeys to work.

Already the city covers 5423sq km but statistician Phil Smythe found that if the population reached 3.8 million, and even if housing density increased, Perth would sprawl over 12,000sq km.

New York City, home to 17.8 million people, covers 8700sq km.

Perth would stretch from the coastal hamlet of Lancelin in the north to the Lakes turn-off in the Perth Hills and south to a point midway between Mandurah and Bunbury.

The population density of Perth would increase to 710 people for every square kilometre, up from 319.

Mr Smythe said the number of vehicles would swell from 900,000 to almost two million.

Thousands of kilometres of roads would have to be built to cope with the extra traffic, and the use of public transport would have to increase dramatically.

Mr Smythe said fewer than 10 per cent of Perth residents used public transport now but that would have to increase to avoid serious congestion.

More desalination plants would be necessary to cope with the increased demand for water, and power generation would have to more than double to supply the energy demands.

There would be challenges for the city's education system, with the number of schools likely to more than double to 2300 with 600,000 students.

"This may mean stiff competition for school names," he said. "Already there are 73 schools named after saints, including 12 after St Joseph and nine after St Mary."

Professor of sustainability at Curtin University, Peter Newman, said the attitudes of Perth residents would change, as they were already in the US, with more people moving back towards the city centre rather than out to the suburban fringes.

He said there were huge costs associated with suburban growth, from transport to health, and it meant more people were now looking to higher density or inner-city life.

"You'll see places like Mandurah, Kwinana, Rockingham, Karrinyup and Morley fill up, especially as younger people start giving up their cars," he said.

Treasurer Wayne Swan said yesterday that people who demanded a cap on Australia's population were too narrowly focused in their complaints.

"It is all too easy to speak of the costs of an increased population, and forget the benefits," he said. "This is a mistake too often made."