For the environment, this means new environmental technologies, experiments with new environmental policy tools, and dynamic social movements dedicated to addressing the region's environment challenges. More than half of the world's population will soon live in urban areas. In the developing world, the urban population is projected to increase by 3 billion over the next 50 years. The growth of cities poses critical environmental problems that reach far beyond municipal boundaries or national borders. Often sited in geographic areas subject to natural hazards, cities also pose major hazard-linked social, economic, and environmental challenges.
Urbanization exacerbates the frequency and severity of hazards such as flooding.
The concentration of people and capital investment increase the scale of potential loss associated with episodic events such as major earthquakes, wildfires, and debris flows, or gradual events such as sea level rise. Such urbanization-driven environmental dilemmas require the development of alternative approaches to production, consumption, and circulation of people and goods if cities are to become sustainable in the future. Broad systemic changes that touch the heart of social, economic, and political life, along with tailored programs designed to address locale-specific problems, will be required to stem the tide of environmental damage associated with explosive urban growth in ways that respect concern for social and economic efficiency.