I think the problem of cities is the twin scourge of urban sprawl and car dependency. Sydney is an expample - commuters travelling in some cases more than 100km to work by car on choked roads. Huge government resources required to build more freeways that choke up quick as more people drive. Horrific associated air, noise and water pollution and greenhouse gases. Fast depletion of oil reserves. Road carnage. Lack of community cohesion as we sit solo for ours in our metal beasts. Lack of physical exercise.

Governments must get real serious now about breaking car dependency. Putting very high taxes on all car parking spaces at retail disticts and places of employment might work. Put the funds to huge investment in public transport including safe cycleways. All capital cities should have a proper metro rail system, not the half-baked system that exists now. Consider making public transport fares cheaper or free and charge the motorists the difference - might get 'em outta their cars.

Create more medium density housing estates in middle ring suburbs that are well serviced by public transport and make the transport work even better. Create better employment opportunities in the outlying suburbs by zoning business parks well served by public transport. It may sound easy, it may sound difficult but something like this needs to be tackled now before our cities and whole planet become unlivelable.

Just some thoughts ... I am sitting in my office in the house we have recently purchased. We live 300 m from a railway station and have a railway line running past just across the road. My children get to school by bus and train and are able to get into the city in 10 to 15 minutes on a train as well if they want. I have been watching relatively empty trains whizz past while since before 8.00am the traffic in the road running parallel has been in complete gridlock.

I am afraid epidemiologists have met their match when they take up the fight for sustainability against the modern city.
Two million years of development for sapiens as a free-range species foraging upon almost equal proportions of vegetable, flesh, and fruit. But less than ten thousand years in developing city-style sedentary living.
One hundred thousand generations to 500. maybe 5,000 to 500 if we confine the comparison completely within Homo sapiens sapiens.
But it is over just the last two generations that major procrustean efforts have been employed to force our species into an inappropriately-sized biological bed. Much as lot-fed cattle are taken away from a natural diet consumed while roaming their grasslands, to stand in crowded yards ruminating on high-protein (even chicken-litter if authorities are not watching) and creating troubling quantities of effluent per animal, all with burgeoning numbers.Epidemiologists know this. But they are whistling in the wind trying to address the fundamentals. It can't be otherwise when people do not want to know, or when habits developed are difficult to change; and especially when the status-quo is "good for the economy as vewed by the convenience-marketers for food, drink, entertainment; by advertising industry, media, political aspirants. Society is besieged by these groups, who exhort us to consume more, to breed more; and believing our breeding rates unsatisfactory, increase immigration. How can cities ever be sustainable when their size ever increases?
People with such biological acumen and sanity as Fenner, Doherty, McMichael keep repeating the message that our species needs to take drastic steps to foster its own wellbeing and acknowledge the limits of the environment to sustain us. I am grateful that they do so. If only the public would take up that message sufficiently strongly to precipitate change from unsustainability.

PK, you're right on the money re: public transport and reducing the use of private vehicles by taxing them out of the city, but before penalising the poor motorist, firstly a reliable and far reaching public transport system needs to be implemented. This requires a complete change of thinking across all Governments, especially at a time when the era of fossil fuels is quickly coming to an end. Geopolitical tentions aside, OPEC seems no longer able to increase production in order to keep pace with world demand for oil. Very soon we'll see a situation whereby fuel for our massive private car fleet is prohibitively expensive and Governments will have no hope of keeping up with installation of public transport as demand for it's existance outstrips potential for implementation. Everyone able to hold a pen or who have access to email should be lobbying their Governments both State and Federal to begin a nationwide implementation program of public transport to all areas including rural areas. Only then can incentives be introduced to wean us off our reliance on private transport. I mention rural areas simply because over a decade ago, fuel was cheap and the tracks which supplied smaller outlying townships were torn up. Public rail transport to areas such as my own were not replaced with other forms of public transport and so we were forced into reliance on private transport to simply get to major centres to find work. Fuel prices are now a major burden on struggling families who live in outlying areas. I'd love to be able to catch a bus or train to work, even though I'd have to cycle 6k's to the nearest bus route, but I don't have that choice and my Government, despite my letters, continue to turn a blind eye to the situation. Makes one wonder just how much influence oil companies have over Government policy.

Our governments need to decentralise more of their services, departments and offices. Then they can fill up the outer suburban commercial centres of Sydney, eg Blacktown, Penrith, Liverpool, Campbelltown with more of their facilities. The only presence of departments in the city should be that limited to service delivery where customers need to personally attend in order to use the service. This reduces travel time and congestion near the Sydney CBD and increases job opportunity for those outside the city.

A while back Australian cities had adequate hospitals, adequate schools etc for the existing population. Health matters were high on the list of priorities. All food shops, cafes had regular inspections by health inspectors and most food was produced in this country according to stringent agricultural and handling laws.
Now there appears to be an absolute deluge of immigration but with inadequate infrastructure , the system is not coping.
The developers are in seventh heaven as they squeeze as much living space onto the least amount of land, hospitals are on constant ambulance bypass.Schools are bulging if not in need of fixing.
But the state government is going to hand out millions for sport stadiums and fields.
And foreign grown food is edging our own home grown out of the supermarkets.
Still from the point of view of the pollies and the developers, all is rosy in Eden.