Today, urban areas generate more than 90% of the global economy, are home to more than 50% of the world population, consume more than 65% of the world's energy; and emit 70% of global greenhouse gas emissions.1 The science and policy communities increasingly recognize that cities, urban areas, and the underlying urbanization process are at the center of global climate change and sustainability challenges. Policymakers need facts, empirical evidence, and theories on how to plan and manage cities and urbanization during the contemporary era of rapid change and environmental uncertainty.
Scholars spanning from the humanities to social and physical sciences have engaged in the study of cities over the past century and have generated numerous discoveries about urban places and processes that drive their creation and development. While some research has concluded that cities are sources of environmental degradation, there is also evidence that cities and the lifestyles they engender can be potential solutions to current and future environmental and sustainability challenges. As a sign of confidence in our understanding of cities, the recent Rio + 20 conference recognized the need for a holistic approach to urban development and human settlements and called for an integrated approach to planning and building sustainable cities and urban settlements to create livable places as a way to solve our local, regional, and even global environmental problems. The idea is simple and enticing: Acting locally within cities can solve our global environmental problems.