Greening Cities

| 1st April 2003
With human beings about to become a predominantly urban species, Dan Box asks whether cities can ever be sustainable.

We are fast approaching a unique point in human history. Within five years half the earth’s population will live in cities. By 2006, we will be a predominantly urban species.

In 1800 London was the only city with a population over 1 million. Today, there are 20 cities around the world with more than 10 million residents, 35 with more than 5 million and hundreds with a million or more residents. Every two weeks, the combined population of these cities swells by a million more.

This rate of change is driven by the shift from rural to industrial economies in the developing world. Asia alone accounts for half the world’s urban population. Within 10 years China plans to create 100 new cities – each with a population of more than a million people. And the cities of Latin America are growing at five times the rate of their smaller, scarcer North American counterparts. The scale of this migration marks the greatest social change since agriculture began 15,000 years ago.

Ecological footprints

The growing number of people living in cities is matched by massive increases in the resources they consume and the pollution they create. Cities rely on their ability to import resources and export their waste. This open loop cannot be sustained.

The ecological footprint of a city represents the area of land required to provide the resources it consumes and to assimilate the waste it generates. London’s footprint alone is now the equivalent of the entire productive land in Britain. Over half of that land is required to absorb the 60 million tonnes of carbon dioxide London produces every year. In producing that carbon dioxide, the city consumes 20 million tonnes of oil per year; that’s two super-tankers worth a week. Unable to meet this demand within its own borders, Britain is set to become a net importer of oil and gas within three years.

Isolated progress…

This pattern of consumption is recreated in every city across the world. At present, the ecological footprint of the earth’s population is a fifth bigger than the earth. If levels of consumption worldwide were the same as those in London, this area would increase to three times the size of the earth’s productive land. Wally N’Dow, secretary general of the second UN Conference on Cities, says: ‘Urbanisation is bringing about one of the most significant transformations in history. The problems this creates are staggering.’

Most urban centres in the developing world will face extreme water shortages within 15 years. Already, ‘more than a billion people cannot get clean drinking water,’ says N’Dow. This ‘causes 80 per cent of diseases in the developing world’.

Faced with this prospect, individual cities are working to reform their urban systems. They are aiming to limit the causes of consumption and waste production to ones which are naturally sustainable within their boundaries.


In London, the introduction of congestion charging has proved the efficiency of political action at this level. Where once the growth of traffic appeared endemic, the 20 per cent cut that followed the charge has shown that traffic congestion can be reduced. Only the week before the British government had abandoned its national target to reduce car traffic by 6 per cent over 10 years, because, transport secretary Alistair Darling claimed, nothing could be done. The initial success of London’s congestion charge now suggests otherwise.

In south London the BedZed housing project provides public housing while producing no net increase in carbon dioxide. The scheme’s energy-efficient design reduces the demand for electricity and heat, which is generated from tree waste that would otherwise go to landfill.

In Copenhagen, a similar approach has been extended across the city. Hot water as a waste product of power generation heats nearly 70 per cent of the city’s buildings. Waste water from kitchens and compost from household waste are used to fertilise food-producing gardens. The city also maintains a fleet of bikes for public use. The bikes are financed through advertising on wheel surfaces and bicycle frames.

…But the system can’t be sustained

While successful, each of these projects can only limit the increasing demands continued urbanisation creates. Although the sustainable city may be possible, urban society is international; emphasising the individual city only limits our response.

For no city stands alone. Almost all land, sea and air transport is between cities and carries the resources to sustain them. This trade is controlled by international markets focused on city exchanges, and is essential to the functioning of these cities’ economies. The emphasis on making cities sustainable within their own confines fails to address this.

Cities are the products of an international economic system predicated on growth. Describing New York, the author Lewis Mumford wrote: ‘Its executives conceive it as their duty to funnel more traffic into the city, through new bridges and tunnels, than its streets and parking spaces can handle – while contributing to the lapse of a more adequate system of public transport. This policy has resulted in mounting traffic congestion, economic waste and human deterioration – coupled with a constant rise in land values and speculative profits.’

Plans for a new airport on the outskirts of London will mean an increase in pollution created both in and by the capital. Yet, the UK government argues, not to act would harm business in the city.

In the developing world, local authorities are increasingly unable to provide for those attracted by the same unfettered economic growth. In Cairo and Dar es Salaam, the resulting slums account for to up to 70 per cent of the population. Within these slums, little infrastructure of any kind exists. How can they be sustainably developed?

Ultimately, it is too late to be satisfied with the effects of sustainable development. At best, it only mitigates the incidental effects of constant economic growth: the quantities of resources consumed and waste produced. Our urbanised society already consumes more than our planet can provide, and urbanisation is still gaining pace.

The world population is increasingly isolated in urban centres surrounded by hinterlands drained of the resources these centres demand. So far, the reaction has been to attempt reform of individual cities. This approach is limited by the boundaries of those cities. It is a mistake to treat a city on individual terms. Cities exist within an international economic system, and their faults must be seen as systemic. The problems they create go beyond their borders. The response to these problems currently does not. The danger is that attempts to create sustainable cities addresses the symptoms, but does not treat the cause.



High above sea level on the plateau of Serra do Mar, the city of Curitiba is the capital of the Brazilian state of Parana. Since the 1950s, its population has grown from 150,000 to over 1.6 million. With careful planning, however, the authorities have created a city that is a model of sustainable urban design.  Its expansion has been controlled by a system of coordinated public transportation and land use. Concentric circles of local bus lines connect to five lines radiating from the centre of the city. On the radial routes, buses in their own traffic lanes carry 300 passengers each. They go as fast as underground trains, but at 1/80th of the construction cost.

The buses stop at tube stations where passengers pay their fares, enter through one end of the tube and exit from the other. Faster loading and unloading means less idling and air pollution. While the stations provide a sheltered place for waiting, the system is so efficient that passengers don’t have to wait much anyway.

As a result, while the city has one car for every three people, two thirds of all journeys within it are made by bus. The system carries more than 50 times as many people today than 20 years ago, and has massively reduced traffic pollution.

The chief architect of this development is John Larimer, now the city’s mayor. Larimer says: ‘When a city accepts as a mandate its quality of life, when it respects the environment, when it prepares for future generations, the people share the responsibility for that mandate. This shared cause is the only way to achieve that collective dream.’

In Curitiba city centre all household waste is taken by council trucks for recycling. Those in the slum settlements unreachable by truck take their waste to local centres, where it is exchanged for bus tickets or food from outlying farms. The waste goes to a plant, itself built of recycled materials, that employs handicapped people, recent immigrants and alcoholics. Recovered materials are sold to local industries.

The recycling programme costs no more than a landfill system, but the city is cleaner, there are more jobs, farmers are supported and the poor get food and transportation.

This article first appeared in the Ecologist April 2003

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