With half the world’s population now residing in urban areas, the United Nations has deemed the 21st century the “Century of the City.” Urban growth patterns during the next 90 years, however, are unlikely to mimic those of the past.
Geography has long been a pivotal factor in determining which cities boom or bust, and port cities frequently benefited from trade along well-traveled coasts and riverways. Recently, however, ground transportation has allowed economic development to take place in more remote regions. Transportation infrastructure, more than free-trade zones or administrative changes, is now considered the most important urban growth factor, according to UN-HABITAT’s State of the World’s Cities report.
Cities in almost all ecosystems are growing at an average rate of 2.2 percent per year. Cities in Africa’s mountainous and forested areas, for example, grew at rates 0.3–0.4 percent faster than cities along coastal zones. A U.N. analysis of 245 of the fastest growing cities in the developing world suggests that the leading driver of this growth has been the diversification, expansion, or improvement of regional or national transportation systems, including roads, airports, urban and inter-urban railway lines, and ports.
Clearly, transportation policies are crucial for driving a country’s sustainable development. As the world’s urban population expands from 3.3 billion people today to almost 5 billion in 2030 and 6.4 billion by 2050, transportation infrastructure will need to expand, not only to carry around so many more people, but also to provide sustainable economies in these urban areas.
As climate change increasingly overheats and floods our urban areas, while also threatening the food and water resources that many cities import from afar, we need cities to become models of low-carbon development.
“Green transportation” doesn’t just offer great possibilities for lowering a city’s carbon footprint—it can also help grow the economies of urban areas. As Worldwatch researcher Michael Renner recently pointed out, studies show that every $1 billion invested in intercity rail and urban transit in U.S. and European cities can support twice the number of jobs gained from investing the same resources in highway infrastructure. In a world of rising oil prices, public transportation will also be a much less expensive option for traveling through the city, especially for poorer residents.
Planners should realize that those cities that are best suited to handle the environmental and social challenges of the 21st century will not focus on building more world-class highways. Instead, they should focus on public transportation as a sustainable way to continue urban growth.