A team of researchers from Texas A&M, Yale, Arizona State and Stanford universities analysed 326 studies that used remote sensing to map urban land conversion between 1970 and 2000. They found that during that period, urban areas increased by 58,000 square kilometres, with India, China and Africa experiencing the highest rates of urban land expansion, and North America the largest total change.

The researchers then developed a model that enabled them to predict that global urban land cover would increase by between 430,000 and 12.5 million square kilometres, with 1.5 million the most likely figure.

The study revealed a range of different reasons for the trend. ‘Annual growth in GDP per capita drives approximately half of the observed urban land expansion in China but only moderately affects urban expansion in India and Africa, where urban land expansion is driven more by urban population growth,’ explained the authors.

Other factors, including land-use policies, agricultural subsidies and transportation costs have also contributed. ‘Urban growth is driven, at least in part, by the economic incentives of local officials to increase their revenue by obtaining rural land and transferring land use rights to developers,’ said the report.

November 2011