Researchers from Yale University and the World Resources Institute analyzed 478 cities with populations of more than 1 million people and found that the predominant urban growth pattern in cities around the world is horizontal, outward expansion into suburbs rather than vertical expansion in the shape of high-rises and skyscrapers. Some 46% of the cities analyzed are experiencing moderate outward growth, and 11% – particularly in Africa and India, but also parts of China – are even experiencing high outward growth.
Outward urban growth patterns are generally considered inefficient and unsustainable because they require high amounts of energy and maintenance, as well as intensive land use.
"While these trends are probably not sustainable in the long term, it's not too late to shape the future of what these cities look like," said Richa Mahtta, lead author of the study. "However, we must act soon before all the urban infrastructure is built and energy consumption becomes locked in. Once cities are fully established, both their spatial patterns and associated human behaviour are difficult to change."
Notable exceptions to this global trend are found in East and Southeast Asia, where there has been a steep rise in the construction of high-rise buildings due to geographic boundaries and high land prices (Hong Kong and Singapore) or declining populations (Japan and South Korea). In many urban areas of China, population growth and government policies are driving growth that is both vertical and horizontal.
