Advancing urban sustainability theory and action: Challenges and opportunities

a b s t r a c t Urban ecology and its theories are increasingly poised to contribute to urban sustainability, through both basic understanding and action. We present a conceptual framework that expands the Indus- trial → Sanitary → Sustainable City transition to include non-sanitary cities, "new cities", and various permutations of transition options for cities encountering exogenous and endogenous "triggers of change". When investigating and modeling these urban transitions, we should consider: (1) the triggers that have induced change; (2) situations where crisis triggers change; (3) why cities transition toward more sustainable states on their own, in the absence of crisis; (4) what we can learn from new city transitions, and non-sanitary city transitions; and (5) how resource interactions affect urban transition s. Several existing theoretical frameworks, including sustainability, resilience, adaptation, and vulnera- bility, may be helpful when considering urban transitions. We suggest that all of these theories interact through inertia in urban systems, and that this multi-faceted inertia—e.g. institutional inertia, infras- tructural inertia, and social inertia—imparts degrees of rigidity that make urban systems less flexible and nimble when facing transitional triggers and change. Given this, solutions to urban sustainability challenges may be categorized as those: (1) that "tweak" the current systems and work with or even take advantage of the inertia in those systems, versus; (2) that are more "transformative", that confront systemic inertia, and that may require new systems. We propose that a model for addressing urban sustainability in the context of relevant theory, and for bridging research and practice, should focus on intercity comparisons. And one mechanism to facilitate this approach is a newly formed interdisci- plinary Research Coordination Network (RCN) that focuses on urban sustainability by integrating urban research while incubating solutions-oriented products and collaborative partnerships with practitioners. The Network includes more than two dozen cities in five continents that are in various degrees of tran- sition. In the true vein of sustainability science, our Network activities are incubating societally-relevant