How do the problems of urbanization in developing countries differ from those caused by urbanization in the developed world?

'Global warning: cities harm people'. This was the stark message given by the second UN conference on human settlements in 1996. No-one can deny that cities the world over have suffered many problems as a result of urbanization. But how do the type and scale of problems differ between those in the developed and the developing world?

The initial problems in less developed cities (LDCs) are often due to rapid demographic changes. Initial migrants from rural areas, or bridgeheaders, are predominantly young and male. The infrastructure of the city cannot cope with the influx of people and this brings inevitable social problems.

Most less developed cities suffer chronic housing shortages. This causes a proliferation of slums and squatter settlements characteristic of so many LDCs, for example Rio, Cairo and Nairobi. Central slums are usually in old, substandard buildings, which have been sub-divided into tiny, cramped flats. Most bridgeheaders initially move here in search of work, but access to services is poor. There is high incidence of crime, suicide, drugs and alcohol. These central areas are often nicknamed 'slums of despair'.

Later, with more money and joined by his family, the early migrant may move to peripheral squatter settlements. Conditions here are fractionally better, but the huge informal settlements, like the favelas around Rio, are a headache for the city authorities. It may take many years for the settlements to be provided with adequate water and electricity, education and healthcare. The self-built houses are often sub-standard with no regard for building regulations.

Most LDCs were originally under the control of colonial powers. In some cities, this leads to noticeable divisions between former ruling classes and native populations. This 'duality' is evident in cities like Harare, where white and black areas have yet to mix to any great extent. Access to services varies dramatically between districts.

More developed cities (MDCs) in the developed world have social problems too, though they are generally more confined to inner city areas. In-migration is far less rapid, although still noticeable. Housing shortages are also less severe, the main result being to drive up prices. Inner city areas are characterised by an increased incidence of single parents, elderly people and children in care. Death rates and infant mortality are higher and life expectancy lower, while access to services is poorer than in outer suburbs. However, the scale of the problems is by no means as bad as in LDCs. The 'poor' healthcare in an inner city borough like Brixton would no doubt be considered excellent in an LDC.

Nonetheless, the same 'themes' are recurrent between LDCs and MDCs. Tension can result where concentrations of ethnic minorities are particularly high, an issue brought to the fore in London by the death of black teenager Stephen Lawrence. Crime and drugs are also perennial problems in the inner cities of the developed world.

The economic problems of LDCs are well-documented. Widespread under- and unemployment is a, if not the, major problem in many LDCs. What work there is, is usually in the informal sector, unregulated and poorly paid. The scale of informal employment can be staggering. In Addis Adaba, for example, some 85% of the workforce are employed in the informal sector. The informal sector does not enable people to benefit from social security, making this support channel useless for the majority.

Many developed cities have suffered a backlash from unsustainable economic growth. Recent years have seen a decline in traditional heavy industries as a result of falling demand and competition. For example, employment in manufacturing fell from 19% in the early 80's to just 9% by 1991 in London. The recession at that time was not helped by the modern economic ideas of downsizing (decreasing staff numbers) and outsourcing (using external contractors as required). The days of full employment are probably now gone, although the situation has recovered significantly from the early 1990's.

The other major problem facing MDCs is decentralization. In recent years, companies have chosen to site away from the expensive city centres, in cheaper, more flexible out-of-town locations. This has been particularly the case with new hi-tech industries, characterised by the M4 'golden corridor', and service activities, hence out-of-town shopping centres like Bluewater off the M25.

Environmental problems are very much a hazard in LDCs. When one thinks of pollution, it is often air pollution that springs to mind, and not without good reason. Thick black smog is common in many LDCs as a result of too many cars. This is particularly an issue in Bangkok. The narrow roads simply cannot cope with the estimated 3 million vehicles a year which travel the streets. The average speed of travel is just 11kph. The exhaust fumes from the many cars, taxis and buses blend into a toxic cocktail of gases.

Respiratory problems are a way of life in most LDCs, especially cardiovascular illness and lung cancer. The World Health Organisation estimates that 98% of Mexico City's population suffer from cell deformation and inflammation of the nasal passages.

Water supplies can by contaminated by leaching of dangerous chemicals into the soil. In fact, water supply itself is a severe problem in many LDCs. In Mexico City, for example, the over-exploitation of local aquifers has caused them to be almost exhausted. Water must be pumped from further afield at a much greater cost. The system of water delivery is also flawed. A quarter or more of water is lost as a result of leaking pipes and illegal 'tapping'.

Illegal dumping of waste is not only an eyesore but a health hazard. Mexico City produces 40% of the country's hazardous waste, some 2.48 million tonnes per year, and yet there are no legal landfill sites.

Congestion and pollution are also problems in MDCs, though they are without doubt less acute. Road networks are much better than in LDCs, but driving in inner city London, Paris or Rome for example, is by no means a pleasant experience. Good, though ageing, public transport makes the situation better than would otherwise be expected, but new money is desperately needed if improvements are to be made. It will take a lot to persuade people to abandon their cars.

Air quality varies from city to city. While legislation like the Clean Air Act has stopped the worst smogs over London and other British cities, other MDCs like Sydney and Los Angeles still suffer from smog. Water pollution, though a problem, is helped by modern technology allowing waste water to be cleaned and by legislation preventing outflow of chemicals into rivers. The Thames has seen a dramatic recovery, but other water features like Lake Erie in North America are still suffering as a result of industrialization.

In some ways, the problems of LDCs and MDCs are very different. While governments in the developing world must try to increase the supply of services to satisfy the increasing population, those in the developed world must try to cope with economic slowdown due to decentralization and changing working patterns.

Yet it could be argued that the types of problems in MDCs and LDCs are not all that different. Yes, the developing world's problems are more acute - but what is happening in the developing world is really no different to what has happened in the developed world over the last 150 years. It is just that it is occurring at a larger scale and at a more frightening pace.

Matthew Mayer