The developing world is rapidly urbanizing, as a previous World Development Report  noted. Low and middle-income nations are home to three quarters of the world’s urban population. Urban areas are likely to absorb almost all of the world’s population increase over the next two decades. The most populous urban areas tend to concentrate in coastal zones--China and India alone have more than a quarter of the world’s urban population and the world’s largest population living in low-lying coastal zones. Even Africa, generally considered a rural continent, has two-fifths of its population in urban areas, and a large concentration of coastal cities.
Climate change represents and new and major threat to urban areas. A one meter sea level rise--considered a near-certain, conservative estimate according to recent research--would put close to 60 million people and over 1% of urban areas at risk today (Dasgupta and others (2007) ). Coastal storm surges will be significantly amplified even by modest sea level rise and would affect a much larger number of people, as well as coastal economic activity. But it’s not just coastal cities. Interior urban areas are also at risk. The massive global retreat of glaciers will reduce fresh water supply to major urban centers, such as those downstream from the Andes and Himalayan mountain systems.
Urbanization is part of the industrialization process, which itself contributes to climate change. However, this does not mean that urbanization needs to be slowed--in fact, dense urban areas have shorter travel distances, consume less land for housing and are more energy efficient. They can also provide services and economic opportunities efficiently. Many of the options to mitigate emissions are in cities, including through better energy efficiency in construction and transport. And adaptive responses to reduce human vulnerability will also take place at the city level, through better urban planning and stronger community-based action.
This raises many questions, both for existing cities that are likely to house many more people in the future as well future cities that will be built to accommodate tomorrow’s urban dwellers. So, what is the 'right' urban form under a warmer and riskier climate? How can urban areas take leadership in mitigating and adapting to climate change? Will we see a retreat from the coast or ‘floating cities’ as climate change impacts become more apparent?