The survival of society has always depended on safeguarding the equilibrium between the variables of population, resources and environment. The neglect of this principle had disastrous and fatal consequences for civilisations of the past. We, too, are subject to the controlling laws of survival, but unlike them we are the first to be a global civilisation and therefore the first ever to have faced a simultaneous and worldwide expansion of population, depletion of natural resources and erosion of the environment.
Above us as I write, 400 or so satellites, equipped with weather instruments, study coastal, ocean and polar processes, constantly beaming back scans of vegetation and atmosphere, plotting the effects of pollution and erosion. Their data plays a crucial role, providing insights into changing geological patterns, global warming and the depletion of the ozone layer. They are witnessing the creation of an environmental catastrophe of a magnitude never before faced by humankind. The exact long-term results of current levels of consumption are not yet clear, but given the scientific uncertainty concerning their precise effects, my contention is that we must apply the "precautionary principle" and ensure that action be taken to safeguard the survival of our species on this planet.
It is a shocking revelation, especially to an architect, that it is our cities that are driving this environmental crisis. In 1900 only one- tenth of the world's population lived in cities. Today, for the first time in history, half the population lives in cities - and in 30 years' time it may rise to as much as three-quarters. The urban population is increasing at a rate of a quarter of a million people per day - the equivalent of a new London every month. The worldwide growth of urban populations, and grossly inefficient patterns of living, are accelerating the rate of increase of pollution and erosion.
It is ironic that mankind's habitat - our cities - is the major destroyer of the ecosystem and the greatest threat to humankind's survival on the planet. In the United States, pollution from cities has already reduced crop production by almost 10 per cent. In Japan, waste dumped by Tokyo city amounts to an estimated 20 million tons every year, waste that has already saturated the entire Tokyo bay. Mexico City is literally drinking its two rivers dry, while London's massive traffic congestion causes greater air pollution today than did the burning of coal in the pre-1956 Clean Air Act period. Cities generate the majority of greenhouse gases, and respected establishment figures such as Sir John Houghton, chair of the United Nations advisory panel on Climate Change, now warn of the disastrous likely effects of current levels of greenhouse-gas production.
While the need for cities and the inevitability of their growth will not diminish, city living per se need not lead to civilisation's self-destruction. I passionately believe that the arts of architecture and city planning could be evolved to provide crucial tools for safeguarding our future, creating cities that provide sustainable and civilising environments. This piece will attempt to demonstrate that future cities could provide the springboard for restoring humanity's harmony with its environment.
My cause for optimism is derived from three factors: the spread of ecological awareness, of communications technology and automated production. All are contributing conditions for the development of an environmentally aware and socially responsible post-industrial urban culture. Through- out the world, scientists, philosophers, economists, politicians, planners, artists and citizens are increasingly demanding that the global perspective be integrated into strategies for the future. A United Nations report, "Our Common Future", proposed the concept of "sustainable development" as the backbone of global economic policy: we should aim to meet our present needs without compromising future generations, and we should actively direct our development in favour of the world's majority - the poor.
The core of this concept of sustainability is the redefining of wealth to include natural capital: clean air, fresh water, an effective ozone layer, a clean sea, fertile land and the abundant diversity of species. The means proposed to ensure the protection of this natural capital are regulations and, most importantly, an appropriate pricing of the market's use of natural capital, an asset that had been previously considered limitless and therefore cost-free. The ultimate aim of sustainable economic development is to leave to future generations a stock of natural capital that equals or ideally exceeds our own inheritance.
Nowhere is the implementation of "sustainability" more potent and more beneficial than in the city. In fact, the benefits to be derived from this approach are potentially so great that environmental sustainability should become the guiding principle of modern urban design.
If cities are undermining the ecological balance of the planet, it is our patterns of social and economic behaviour that are the root cause of their development in ways that produce environmental imbalance. In both developed and developing worlds, the "carrying" capacity of cities is being stretched to the limit. Cities are increasing in size and at such a rate that conventional patterns of accommodating urban growth have become obsolete. In the developed world the migration of people and activities from city centres to the dream world of suburbia has led to massive suburban development, widespread road-building, increased car use, congestion and pollution best exemplified in the cities of the western USA like Phoenix and Las Vegas. Meanwhile, in the fast-growing economies of the developing world, new cities are being built at a phenomenal rate and density with little thought for future environmental or social impact. Worldwide, there is a mass migration of the rural poor to these new consumerist cities. Every-where the situation of the poor is largely overlooked. In the developed world they fall out of the consumer society and are abandoned and isolated in the inner-city ghettos, while in the developing cities the poor are relegated to the squalor of the swelling shanty towns. "Unofficial" or illegal residents regularly outnumber the official ones.
Cities are producing disastrous social instability that is further driving environmental decline. Despite global increases in wealth that far outpace increases in population, the world's poor are growing in number and in poverty. Many of these poor are living in the most squalid environments, exposed to extremes of environmental poverty and perpetuating the cycle of erosion and pollution. Cities are destined to house a larger and larger proportion of the world's poor. It should come as no surprise that societies and cities that lack basic equity suffer intense social deprivation and create greater environmental damage - environmental and social issues are interlocked.
Poverty, unemployment, ill-health, poor education, conflict - in short, social injustice in all its forms - undermine a city's capacity to be environmentally sustainable. Cities that have experienced civil war, such as Beirut; that suffer from severe poverty, such as Bombay; that have alienated large sections of their population from mainstream life, such as Los Angeles; or that pursue profit as their only motive, such as Sao Paulo, damage the environment to the detriment of all. There can be no urban harmony or real environmental improvements without basic human rights and peace.
Cities throughout the rich, developed world contain communities that are experiencing intense social deprivation, but it is in the rapidly expanding cities of the developing world that the crisis of the poor is expanding all the faster. If unchecked, the ecological and social problems of these cities will soon dominate the human scene. The idea that the rich few can continue to turn their backs on the pollution and poverty of these cities and operate in comfortable isolation from these seats of desolation is short-sighted in the extreme. Lack of basic equity is the constant force undermining attempts to harmonise society and humanise its cities.
Beyond providing opportunities for employment and wealth, cities provide the physical framework for an urban community. In recent decades and throughout the world, the public realm of cities, the people's spaces between buildings, has been neglected or eroded. This process has increased the polarisation of society and created further poverty and alienation. New concepts of urban planning that integrate social responsibilities are needed. Cities have grown and changed into such complex and unmanageable structures that it is hard to remember that they exist first and foremost to satisfy the human and social needs of communities. In fact they generally fail to be seen in this way. If you ask people what they think of cities they are more likely to talk about buildings and cars than streets and squares. If you ask them about city life, they are more likely to talk about alienation, isolation, fear of crime or congestion and pollution than about community, participation, animation, beauty or pleasure.
They will probably say that the concepts "city" and "quality of life" are incompatible. In the developed world this conflict is driving citizens into the seclusion of private guarded territories, segregating rich from poor and stripping citizenship of its very meaning.
The city has been viewed as an arena for consumerism. Political and commercial expediency has shifted the emphasis of urban development from meeting the broad social needs of the community to meeting the circumscribed needs of individuals. The pursuit of this narrow objective has sapped the city of its vitality. The complexity of "community" has been untangled and public life has been dissected into individual components. Paradoxically, in this global age of rising democracy, cities are increasingly polarising society into segregated communities.
The result of this trend is the decline of the vitality of our urban spaces. The political theorist Michael Walzer has classified urban space into two distinct groups: "single-minded" and "open-minded" spaces. "Single- minded" describes a concept of urban space that fulfils a single function and is generally the consequence of decisions by old-guard planners or developers. "Open-minded" is conceived as multi- functional and has evolved or been designed for a variety of uses in which everyone can participate. The residential suburb, the housing estate, the business district, the industrial zone, the car park, underpass, ring-road, shopping mall, even the car itself, provide "single-minded" spaces. But the busy square, the lively street, the market, the park, the pavement cafe are "open-minded". When we are in the first type of spaces we are generally in a hurry, but in the "open-minded" places we are readier to meet people's gaze and to participate.
Both categories have a role to play in the city. Single-minded spaces cater to our very modern craving for private consumption and autonomy. They are very efficient, in those terms. In contrast, open-minded places give us something in common: they bring diverse sections of society together and breed a sense of tolerance, awareness, identity and mutual respect.
My point, however, is that in the process of designing cities to meet the inexorable patterns of private demand, we have seen the former category eclipsing the latter. Open-mindedness has given way to single- mindedness and in its wake we are witnessing the destruction of the very idea of the inclusive city.
The emphasis is now on selfishness and separation rather than contact and community. In the new kinds of urban development, the activities that traditionally overlapped are organised for the purpose of maximising profit for developers or retailers. Businesses are isolated and grouped into business parks; shops are grouped in shopping centres with theatre-set "streets" built into them; homes are grouped into residential suburbs and housing estates. Inevitably, the streets and squares of this counterfeit public domain lack the diversity, vitality and humanity of everyday city life. Worse still, the existing streets of the city are drained of commercial life and become little more than a no-man's land for scurrying pedestrians or sealed private cars. People today do value convenience but they also long for genuine public life, and the crowds that pack city centres on weekends testify to this.
The disappearance of "open-minded" public space is not simply a cause for regret: it can generate dire social consequences launching a spiral of decline. As the vibrancy of public spaces diminishes we lose the habit of participating in street life. The natural policing of streets that comes from the presence of people needs to be replaced by "security" and the city itself becomes less hospitable and more alienating. Soon our public spaces are perceived as downright dangerous, and fear enters the scene.
In response, activities become ever more territorial. The street market becomes less attractive than the secured shopping mall, the university district becomes the closed campus; and as this process spreads through the city the open-minded public domain retreats. People with wealth bar themselves in or move out of the city. In these closed, privatised spaces, the poor are forbidden to enter, guards stand at the gate. Those without money are equivalent to those without a passport, a class to be banished. Citizenship - the notion of shared responsibility for one's environment - disappears, and city life becomes a two-tier structure, with the rich in protected enclaves and the poor trapped in inner-city ghettos or, as in the developing world, squalid shanty towns. We created cities to celebrate what we have in common. Now they are designed to keep us apart.
The sprawling cities of the USA, with their inner-city ghettos, heavily policed middle-class dormitories, shopping centres and business parks, show this divisive tendency most clearly. The Californian writer Mike Davis describes how Los Angeles, the scene of repeated riots in recent decades, has grown more and more segregated, even militarised.
Starting at the outskirts there is the Toxic Rim, a circle of giant garbage landfill, radioactive-waste dumps and polluting industries. Moving inwards you pass so-called gated or privately patrolled residential suburbs and a zone of self-policing lower-middle-class homes, until you reach a free- fire downtown area of ghettos and gangs. Here, the Ramparts Division of the Los Angeles police regularly investigates more murders than any other local police department in the country. Finally, beyond this no-go area lies the business district itself. In parts of this area, TV cameras and security devices screen almost every passing pedestrian.
At the touch of a button, access is blocked, bullet-proof screens are activated, bomb-proof shutters roll down. The appearance of the "wrong sort of person" triggers a quiet panic. Video cameras turn on their mounts. Security guards adjust their belts. A new type of citadel has emerged which relies not only on physical boundaries, high fences, barbed wire and imposing gates but increasingly on invisible electronic hardware.
In LA the car has become the mobile fortress. Tinted windows disguise the identity of passengers, bullet-proof glass protects from armed attack, doors can in an instant be centrally locked from within, creating ever greater alienation of the individual from the city.
The situation in Houston is almost as disturbing. An entire network of underground streets - more than six miles long - has been excavated beneath the city's downtown business district. This glitzy maze, called with unintended irony the "connection system", is entirely private. You cannot gain admittance to it from the street, but only through the marble lobbies of the banks and oil companies that dominate Houston. The result is the creation of yet another kind of urban ghetto. The car-choked streets are left to the poor and unemployed, while wealthy workers shop and do business in air- conditioned comfort.
Although British or European cities have not yet gone this far, many display similar tendencies writ small. We too have seen a retreat to the suburbs and growing inner-city poverty, an increasing reliance on private security and private transport, the proliferation of single-minded spaces. Any attempt to redress the situation must depend on mobilising the participation of individuals and their sense of belonging to the city. It is the individual's commitment to their city which is so absolutely central to achieving sustainability. Civic beauty is the result of the social and cultural commitment of the communities of an urban society. It is a dynamic force that colours all aspects of city life down to the design of its buildings.
I passionately believe in the importance of citizenship and the liveliness and humanity it stimulates. It manifests itself in planned large-scale civic gestures but also in the small scale and the spontaneous. Together they create the rich diversity of city life. Cities remain the great demographic magnets of our time because they facilitate work and are the seedbeds of our cultural development. Cities are centres of communication, learning and complex commercial enterprises; they house huge concentrations of families; they focus and condense physical, intellectual and creative energy. They are places of hugely diversified activities and functions: exhibitions and demonstrations, bars and cathedrals, shops and opera houses. I love their combination of ages, races, cultures and activities, the mix of community and anonymity, familiarity and surprise, even their sense of dangerous excitement. I enjoy their grand spaces as well as the animation that simple pavement cafes bring to the street, the informal liveliness of the public square, the mixture of workplaces, shops and homes that make living neighbourhoods.
Strolling through Europe's great public spaces - the covered Galleria in Milan, the Ramblas in Barcelona, the parks of London or the everyday public spaces of markets and local neighbourhoods - I feel part of the community of the city. The Italians even have a word which describes the way men, women and children interact with the public space of their city as they stroll on their streets and squares in the evening: they call it la passeggiata.
When the Parisian authorities agreed to let us give half the site they had set aside for the Pompidou Centre to a public piazza they were encouraging exactly this type of citizenship. The idea of integrating a bustling public square into the Pompidou Centre project had come from our experience of historic public spaces, such as Jamaa El Afna in Marrakech, Piazza San Marco in Venice and the Campo at the heart of Siena, scene of the Palio horse race. To my great delight the relationship between building and public space, between the Centre and the Place Beaubourg, has created a place teeming with public life and has regenerated the areas around it.
Active citizenship and vibrant urban life are essential components of a good city and of civic identity. To restore these where they are lacking, citizens must be involved in the evolution of their cities. They must feel that public space is in their communal ownership and responsibility. From the modest back street to the grand civic square these spaces belong to the citizen and make up the totality of the public domain, a public institution in its own right which like any other can enhance or frustrate our urban existence. The public domain is the theatre of an urban culture. It is where citizenship is enacted, it is the glue that can bind an urban society together.
Cities can only reflect the values, commitment and resolve of the societies which they contain. The success of a city therefore depends on its inhabitants, their government and the priority both give to maintaining a humane urban environment. The Athenians of ancient Greece recognised the importance of their city and the role it played in encouraging the moral and intellectual democracy of their times. The agora, the temples, the stadium, the theatre and the public spaces between them were both the magnificent artistic expression of Hellenic culture and the catalyst for its rich humanist development. The commitment to the interdependence of built form and ideals was captured in the oath pledged by new citizens: "We will leave this city not less but greater, better and more beautiful than it was left to us." Quality of urban environment defines quality of life for citizens. The relation between city and civic harmony is well established.
Vitruvius, Leonardo da Vinci, Thomas Jefferson, Ebenezer Howard, Le Corbusier, Frank Lloyd Wright, Buckminster Fuller and others proposed ideal cities that they imagined would create ideal societies - cities that would encourage better citizenship and enable society to overcome its traumas. While such single-minded visions of cities are no longer relevant to the diversity and complexity of modern society, these architectural attempts at Utopia should remind us that, in a democratic age, contemporary architecture and planning might be expected to express our common philosophical and social values. But, in fact, most recent transformations of cities reflect society's commitment to the pursuit of personal wealth. Wealth has become an end in itself rather than a means of achieving broader social goals.
The construction of our habitat continues to be dominated by market forces and short-term financial imperatives. Not surprisingly, this has produced spectacularly chaotic results. It astounds me that the built environment in so many places remains an incidental political issue. Cities are the cradle of civilisation, the condensers and engines of our cultural development. Putting the culture of cities back on the political agenda is critical, for while they might be places where life is at its most precarious, cities can also fundamentally inspire. This is the dichotomy of the city: its potential to brutalise and its potential to civilise.
A new form of citizenship must be evolved that responds to the needs of a modern city. Greater emphasis on citizen participation and better leadership are vital. Involving communities in decision-making requires that the built environment becomes a standard part of education, and a major component of our National Curriculum. Teaching children about their everyday urban environment equips them to participate in the process of respecting and improving the city. Cities themselves can be a great tool, a live laboratory for education. Environ-mental sustainability should be at the core of subjects taught - a theme linking physics, biology, art and history. We must make funds available to interest and inform the public. We must teach good citizenship to young and old, and listen to citizens. Much of our future "quality of life" depends on getting this right.
Should people be demoralised by the apparently insurmountable task of gaining democratic control of their cities, there are encouraging examples from around the world. In many places, the city, in its many aspects from ecology to architecture, is an established issue of public debate and electioneering, a sharp contrast to its neglect in Britain.
The late President Francois Mitterand stated that "culture", and in particular architecture, was the fourth most important voting issue in France (I dread to think how high British politicians would rank culture). In Britain we are perhaps aware only of major initiatives such as the Grand Projects of Paris, but these are just the tip of the iceberg. In France there is a competition for each and every government building, be it a public-housing project, a school, a post office, a local square, a park or an entire new town. All local competitions of any significance are decided by a jury comprised of the mayor, a representative of the users, members of the local community, technical experts and architects. There are small competitions designed to encourage young talent as well as major international competitions (often involving the President himself) designed to ensure that France is home to the best of international architecture.
Contrast this with the situation in Britain, where taxpayers spend pounds 4 billion annually on their public buildings and yet central government has had no architectural policy. In 1992 we held 10 public design competitions to France's 2,000. Britons complain about their architecture, yet they have a generation of talented young architects who almost without exception have received no public commissions in this country. It is maddening to watch real talent being squandered today and a mediocre architectural heritage left for tomorrow.
Curitiba, a rapidly expanding city in Brazil, has succeeded, thanks to far-sighted leadership and public participation, in tackling its problems of growth and consolidation. As I will describe later, they have pursued myriad policies aimed at increasing environmental and social awareness, covering everything from education to commerce, transport to planning. As a result, citizens feel that they own their city and are responsible for its future.
Rotterdam provides an example of concerted government-sponsored but community- oriented development. A strategic plan for the entire city defines the principle directions in which the community wish to see their city grow. The conversion of their docklands is the subject of continuous study, debate and collaboration. The majority of land in and around the city is publicly owned and can be given to the community when and where the need arises, rather than when someone can afford to buy a site. The city aims to grow like a cell structure, splitting and replicating into mixed neighbourhoods of three to five thousand people with workplaces, schools, shops and housing. At least a third of each new community consists of overflow from neighbouring communities, which ensures the social coherence of the whole. In this way, Rotterdam avoids dividing itself into segregated zones and isolated communities.
In Spain, the end of Franco's rule was followed by the election of city mayors, and in Barcelona strong mayoral leadership backed by popular support totally transformed the city. The Mayor, Pascal Maragal, and his Minister of Culture, the architect Oriel Bohigas, used the hosting of the 1992 Olympics as a catalyst for visionary reform that went much further than the provision of Olympic facilities. It included the establishment of a strategic masterplan for the entire city, the refurbishment of streets and, significantly, the creation of 150 new public squares. They called upon some of the world's leading architects to implement the most ambitious of all the city's redevelopment plans: the conversion of its defunct industrial dock area that had separated the city from the sea, a waterside area typical of coastal industrial cities throughout the world. The result is that the city has been reconnected to the sea along a huge stretch of coast. Beyond specific projects, Maragal has created an atmosphere in which the private sector is willing to conform to popular public leadership, because developers can both see the overall benefit of the long-term improvement of the city and recognise the importance of public interest. By these democratic processes Barcelona has been transformed into a world-class city, a place where people long to visit, work and live.
The cities of San Francisco, Seattle and Portland have integrated public participation in urban planning into their electoral system. In local elections, you don't just choose a candidate, you have the opportunity to make decisions about your own surroundings: How much office space should be allowed? Which regeneration plan is best? What transportation strategy to adopt? The inhabitants of these cities therefore feel they have involvement and control over their city's destiny.
The above approaches illustrate how urban societies are evolving strategies tailored to their specific culture and needs. In each of these cities there is a fundamental assumption that citizens have a say in the shaping of their cities. They emphatically prove that public participation and genuine government commitment can transform the physical and social fabric of our cities.
I have touched upon some of the problems facing contemporary cities and have illustrated how citizens' commitment can contribute to improving the situation. In parallel we must pursue ever more decisively the development of technologies and innovations that protect our ecology and humanise our cities.
Humankind's capacity to transmit accumulated knowledge from generation to generation, to anticipate and to solve problems, has been its greatest asset. I find it amazing and tremendously inspiring that only a hundred typical lifespans separate our present age, which can build a city in space, from the age which saw the first cities built along the Euphrates and the Tigris.
Technology and our ability to predict have transformed our world, and often in the face of appalling odds. In 1798 the economist Malthus warned that, according to his calculations, the rate of increase in the world population was exceeding the capacity of the Earth to feed future generations. He was proved wrong because he had reckoned without the remarkable potential of technology. In the hundred years following his ominous prediction, the population of Britain quadrupled, but technological advances brought a 14-fold increase in agricultural production. Nowadays technology develops ever faster and offers even greater opportunities. There were only two lifespans between the invention of the bicycle and that of space travel; and less than half a lifespan between the invention of the first electronic computer and the development of the information superhighway.
In his compelling analysis of modernity in the 19th and 20th centuries, Marshall Berman reminds us of the challenge to traditional social, economic and religious values that accompanies this technological evolution. He quotes from Marx's vivid description of the modern condition: "All fixed, fast-frozen relations, with their train of ancient and venerable prejudices and opinions, are swept away, all new-formed ones become antiquated before they can ossify. All that is solid melts into air, all that is holy is profaned, and men at last are forced to face the real conditions of their lives and their relations with their fellow men."
Embracing change always carries uncertainty and risk. The power to transform and change both ourselves and the world defines our modern condition. The thirst for what we can achieve is balanced by the awareness of our ability to destroy. To be modern, therefore, is to live this life of paradox - this is the Faustian bargain that Berman so brilliantly exposes.
In this maelstrom, the laws of the market have taken hold. But the "invisible hand" of the market is a force of neither nature nor man. Society, in the form of its governments and other institutions, has the responsibility to focus the dynamic of modern life, to direct the application of new technology, to confront old values with new. The city is the embodiment of society; its form must be continuously viewed against our social objectives. The problems of today's cities are not the result of rampant technological development, but of its rampant misapplication.
The speed of technological change and, above all, the speed and breadth of its dissemination provides modern society with its greatest potential power. The United Nations Development Agency estimates that in the next 30 years as many people will be seeking a formal education qualification as have done so in total since the beginning of civilisation. Robotics place our generation in a position to reap the benefit of more wealth per capita with less labour. For the first time since the industrial revolution, work is taking up less of our lives. Robotics, education, medicine, global communications - all manifestations of our technological development - provide the conditions for the development of a new form of creative citizenship that generates wealth for society without breaching the limits of our environment's sustainability.
The challenge we face is to move from a system that exploits technological development for pure profit to one that has sustainable objectives. Making cities sustainable demands fundamental changes in human behaviour, in the practice of government, commerce, architecture and city planning. The developer who builds for purely commercial returns, with no commitment to the city's environment nor to the quality of life of its citizens, is misusing technology. So too is the planner who drives a motorway through the middle of a city without regard for the broader environmental or social issues.
I am wild about technology but not about technology run wild. Technology must be focused by the citizen for the benefit of the citizen; it should seek to secure universal human rights and provide shelter, water, food, health, education, hope and freedom for all. It is my belief that the sustainable city could provide the framework for the fulfilment of these basic human rights. That ideal underpins my approach to sustainability: mobilising creative thinking and technology to secure humanity's future on this small planet of finite resources. It is an innovation that would have an impact on the city of the 21st century as radical as that of the industrial revolution on the city of the 19th century.
'Cities For a Small Planet' (Faber & Faber, pounds 9.99), based on Richard Rogers' 1995 Reith Lectures and edited by Philip Gumuchjian, is out next week. To order a copy at the reduced price of pounds 8.99 (inc p&p), phone the Faber credit-card hotline on 01279 417134, quoting this offer. National Architecture Week, consisting of more than 150 events around the country, runs to Thursday. For further information call 0171 490 5969.