City living affects our behaviours, health and lifespan in more ways than we usually realise. A prominent example is how, over recent decades, increased road-building and car dependence - and, hence, reduced daily exertion - have contributed to the alarming rise in obesity. So, too, has modern food-processing, in conjunction with retail food outlets, intensive advertising and the pervasive canteen Coke-chips-and-chocolate culture. These conditions of daily living predispose to daily caloric intake exceeding daily output.
Around the world, cities are rapidly becoming the dominant "human habitat". Some time this decade Homo sapiens will become an urban species, as the proportion of all humans living in large towns or cities passes the 50 per cent mark.
We therefore have a great stake in understanding how the planning and functioning of cities affects patterns of well-being, health and disease. Indeed, those outcomes, being expressions of actual human experience, should be the real focal point of "sustainability". After all, we don't want productive economies, cohesive communities or conserved natural environments in their own free-standing right; we want them because they make our lives better, more meaningful and healthier.
That is the frame within which we should now be thinking about Australia's cities, present and future. Indeed, the sustainability discussion holds promise of transforming the way that we think about urban environments and our way of living in cities. They are not merely economic engines, trading centres, consumer havens or tourist must-sees. They are habitat; they have their own ecology.
Urban planning and the goal of "sustainable cities" has recently become a more prominent topic in Australia. In September 2005, the House of Representatives Standing Committee tabled its Sustainable Cities report. There is heightened awareness that our cities are struggling with water shortages, traffic congestion, waste disposal, escalating energy demands and the dilemma of increasing emissions of greenhouse gases.
Policy discussions, in recent years, have paid little attention to how these problems actually affect risks to the well-being and health of city populations. Hopefully, though, this growing recognition of systemic difficulties with the growth and metabolism of cities will also illuminate the cities-and-health relationship. It will encourage a more integrated "ecological" view of the inter-linked influences on health. It will necessitate a longer time-frame for thinking about building and maintaining health-supportive cities.
Before the scientific age in western society, health promotion and disease prevention were not explicit objectives in the development of cities. Plato's utopian proposal for an "ideal" (or at least a "just") city was framed in terms of politics, ethics and social relations. Over many ensuing centuries, little was understood about the environmental factors that influenced health and disease. Food shortages, famines and epidemic outbreaks were mostly viewed as the work of the gods, often as divine retribution.
Sustained public concern about urban environments in the cities of Europe and its distant offshoots first arose in response to crowding, squalor and environmental pollution in early-industrial cities. Epidemic infections (cholera, consumption [TB], measles, smallpox and others) created fears among rich and poor. Malnutrition and recurrent infections weakened workers and exacerbated poverty.
The need for domestic hygiene and public sanitation was recognised by governments. The ensuing sanitary reforms in the latter 19th century, along with improved civic infrastructure, yielded health gains. During that era, the motives for seeking health gains were mixed: self-protection, enhanced economic productivity and environmental amenity all loomed large.
The historical scourges of infectious disease epidemics and severe air pollution have been largely controlled.
However, today we face various newer urban health problems. These include obesity and its serious consequences, mental health disorders, alienation and anti-social behaviours, and - on an even large scale - the various health risks from climate change.
The annual Fenner Conference, at the Australian Academy of Science last week, explored the relationships between urbanism, environment and health. It was attended by about 200 people from government, the private sector, the urban planning profession, university researchers and community groups.
Recent research evidence, presented at the conference by Dr Larry Frank from Vancouver, showed how making a city easier to get around on foot encourages people to be more physically active. "There are many flow-on benefits to both health and to the environment," he says. "These include less local air pollution, reduced obesity, lower stress levels and fewer greenhouse gas emissions."
The future planning and development of Australia's cities, as places where people live and work, and where health-affecting behaviours and experiences arise, must place the human dimension at the focal point of sustainability planning. The measure of "sustainable cities" is not to be found in economic indices, edifice density or traffic flows. It resides in whether people are happier, fulfilled, healthier and longer living.