Go green, move to a city

They may be widely regarded as the perfect symbol of carbon-intensive, unsustainable consumption, but the world's mega-cities in fact provide their residents with lower carbon footprints than their rural counterparts.

That is the conclusion of a new study from the International Institute for Environment and Development to be published next month, which found that per capita emissions in many of the world's largest cities are often just a fraction of the national average.

The report analysed official emissions data from major cities in Europe, Asia and North and South America and found that while they remain major sources of pollution, high population densities, widespread use of public transport and efficient use of resources mean that per capita emissions are generally lower than the national average.

According to the report, London emitted 44.3 million tonnes of CO2 in 2006, or eight per cent of the UK's total emissions, but its population of seven million people meant that per capita emissions were just 55 per cent of the UK's average in 2004.

Similarly, the high population density and prevalence of small apartments meant that the average New York resident had emissions of about 7.1 tonnes, or less than a third of the US average of 23.92 tonnes.

The only exceptions to the rule were Beijing and Shanghai, where the report found the high levels of export-oriented factories meant that per capita emissions were higher than China's average.

"Many cities have surprisingly low per capita emissions but what is clear is that most emissions come from the world's wealthier nations," said report author David Dodman. "The real climate-change culprits are not the cities themselves but the high-consumption lifestyles of people living across these wealthy countries."

He added that policy makers should regard well-designed cities as one of most effective environments for delivering low levels of carbon emissions, warning that poorly planned cities would struggle to reduce their carbon footprint.

"Tokyo has considerably lower emissions per person than either Beijing or Shanghai and this shows clearly that prosperity does not lead inevitably to greater emissions," he said. "Well-designed and well-governed cities can combine high living standards with much lower greenhouse gas emissions."