Sustainability in an urbanizing planet

Sustainability science is use-inspired fundamental research that links knowledge to action such that meeting the needs of society can be balanced with sustaining the life support systems of the planet (1, 2). Nowhere is this action-oriented research needed more than in urban areas that are now home to more than half of the world’s population, generating about 80% of the world’s economy (3) as well as over 70% of global energy use and global energy-related emissions (4). Depending on the literature and perspectives taken, urbanization and cities will be either key components to the transition to sustainability or major threats to sustainability. The dichotomy in views is partly a result of the wide range in urban conditions and uneven urbanization processes around the world. Urban areas can be sites of innovation and production of knowledge and wealth, and provide widespread access to employment, education, sanitation, and modern energy, but they can also have high levels of pollution, social exclusion, environmental degradation, and cause unintended consequences outside of the urban boundaries; all of these outcomes could occur simultaneously through the same urbanization process. A number of urban transitions are underway, several of which involve: the change from a predominantly rural and lower-density population to an urban and higher-density living; the shift in economies from agrarian to manufacturing and services, finance, and technology; the increasing resource intensity of energy, materials, and water required to produce a unit of good or service; the lasting imprint and spatial configuration of built environments and their requisite infrastructures; the subtle impact on a broad spectrum of biotic interactions and the significant threats to biodiversity; the increasing complexity and reach of urban institutions and governance to enforce the rule of law and maintain civil society; and the transition from individually demarcated cities and towns to the … [↵][1]1To whom correspondence should be addressed. Email: karen.seto{at}yale.edu. [1]: #xref-corresp-1-1