Cities have long held the promise of 'streets paved with gold'. Today, nearly half of us live in urban areas; by 2030, two thirds of us will. The world's cities are currently home to more than 3 billion people and are growing by 1 million people a week - 100 new residents every minute.

Although cities occupy just 2 per cent of the earth's land surface, their inhabitants use 75 per cent of the world's resources. But cities are economic powerhouses, too, generating more than half the world's wealth and, in some developing countries, up to 80 per cent of their economic activity. On average, urban dwellers earn higher wages and live healthier, easier lives than their rural counterparts.

The benefits are not universal - as many as 1 billion people live in slums and squatter settlements with limited access to clean water, sanitation, adequate housing, transport, schooling or health care. For them, city life is marked not only by opportunities but also by poverty, overcrowding, disease, violence and uncertainty, with survival depending on their astonishing personal resilience and resourcefulness.

The growth of modern cities has far surpassed the mass migrations of the past. People will still flock to them as long as urban living conditions outstrip those in the countryside. For the first time in history, humans are becoming predominantly urban. Might our mindsets and lifestyles decreasingly comprehend the values and vital services provided by natural world? A challenge for us all, as - from towns to mega-metropolises - the urban revolution is here to stay.



Cities under pressure from rising populations can expand upwards, outwards or underground - and many do all three. After all, new city dwellers - and the homes, workplaces, transport and public places they require - need to go somewhere. As skyscrapers, subway systems and high-rise buildings alone cannot absorb this rapid growth, city planners have looked increasingly to urban peripheries to accept population and commercial overflow (often termed 'sprawl').

Urban expansion has often led to higher city revenues through additional tax sources and business activities, and provided families with space to live and work, but it also can increase congestion and pollution, destroy greenery and wildlife and encourage wasteful use of land and natural resources.

Solutions for the future will be likely to come from 'smart growth' initiatives - constructing well-connected street networks, accessible public transport, mixed-use buildings, civic squares and public green spaces - that blend social, economic and environmental concerns to improve the quality of urban living.


photos: Earth Sciences and Image Analysis Laboratory at Johnson Space Center


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