Published online 20 October 2010 | Nature 467, 900-901 (2010) | doi:10.1038/467900a

News Feature

Cities: The century of the city

The explosion in urban population looks set to continue through the twenty-first century, presenting challenges and opportunities for scientists.

WHERE THE PEOPLE ARE

In less than a human lifespan, the face of Earth has been transformed. In 1950, only 29% of people lived in cities. Today that figure is 50.5% and is expected to reach 70% by 2050.

1 The United States is one of the few developed countries where cities have continued to grow. Its urban population of 261 million is set to hit 308 million in 2025.

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2 Europe 's urban population is not expected to change much in the coming decades, rising from 920 million in 2010 to 1.1 billion in 2030.

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3 Latin America is highly urbanized — 80% of its population lives in cities — up from 41% in 1950. Its urban population of 500 million in 2010 is expected to grow to 650 million by 2025.

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4 Only 40% of Africa 's population currently lives in cities, but its urban population is growing quickly. Many of the world's fastest growing big cities are in Africa.

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5 Asia 's urban population is growing faster than in any other region, continuing the trend from the twentieth century. The urban population, 234 million in 1950, reached 1 billion in 1990, and is expected to reach 3.4 billion by 2025.

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6 Megacities — which have populations of more than 10 million — are home to 1 in 10 people.

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WHERE THE PROBLEMS ARE

Cities are gluttons when it comes to resources. In 2006, about 50% of the world's population was urban, but they consumed two-thirds of the total energy used and emitted more than 70% of the energy-related carbon dioxide emissions.

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WHERE THE SCIENCE IS

The solutions to many global problems are in cities. According to one geographic analysis in 2004, the greatest concentrations of scientific publications are in the major cities that hold most of the scientific resources.

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Graphics by Nik Spencer; data compiled by Declan Butler. For the full cities special see nature.com/cities

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