How much of the Earth's surface is covered by towns and cities?
According to the UN, in 1830, just three per cent of the world's population lived in urban areas. By 1900, the proportion had more than quadrupled to 14 per cent and, by 2000, close to half of the world had moved out of the countryside. The UN reckons that, by 2030, some 60 per cent of people will have taken up urban life.
However, as the population density of towns and cities is far higher than that of villages and farms, the area of land under urban use is a lot smaller than you might imagine. For several years, researchers believed that towns and cities covered between one and two per cent of the Earth's surface. However, a new Columbia University study suggests the figure could be closer to three per cent.
The Columbia researchers' system, called Grump, used various techniques, including census data and night-time satellite pictures--lights give a good approximation of urban spread--to find places with a population of more than 5,000 people and with an area of more than one square kilometre.
The result for the year 2000 was a total of 24,000 urban areas of all sizes; Tokyo was the largest, sprawling over more than 30,000 square kilometres. Many urban areas are formed when growing towns merge, and the project identified more than 75,000 distinct settlements.
The project revealed that coastal areas tend to be richer in towns and cities than elsewhere, particularly in Asia and Africa. Grump also found that seven per cent of the world's population now lives in the largest megacities. Previous estimates had put the figure at four per cent.
N Bracken, Paisley
|Printer friendly Cite/link Email Feedback|
|Article Type:||Brief Article|
|Date:||Jun 1, 2005|
|Previous Article:||Why is the Baltic Sea island of Bornholm part of Denmark when it's located so close to Sweden?|
|Next Article:||Where is the coldest place on the equator?|