sustainability Article Urban Sustainability and Resilience: From Theory to Practice Patricia Romero-Lankao 1, *, Daniel M. Gnatz 2 , Olga Wilhelmi 1 and Mary Hayden 1 1 National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307-3000, USA; olgaw@ucar.edu (O.W.); mhayden@ucar.edu (M.H.) 2 MnS Institute for Sustainable Urban Transformations, P.O. Box 21292, Boulder, CO 80308, USA; gnatz@isut.org * Correspondence: prlankao@ucar.edu; Tel.: +1-303-497-8104 Academic Editor: Tan Yigitcanlar Received: 22 August 2016; Accepted: 16 November 2016; Published: 25 November 2016 Abstract: Urbanization and urban areas are profoundly altering the relationship between society and the environment, and affecting cities’ sustainability and resilience in complex ways at alarming rates. Over the last decades, sustainability and resilience have become key concepts aimed at understanding existing urban dynamics and responding to the challenges of creating livable urban futures. Sustainability and resilience have also moved and are now core analytic and normative concepts for many scholars, transnational networks and urban communities of practice. Yet, even with this elevated scholarly attention, strategies for bridging between research and practice remain elusive, and efforts to understand and affect change towards more sustainable and resilient urban centers have often fallen short. This paper seeks to synthesize, from this issue’s papers and other strands of literature, the knowledge, theory and practice of urban sustainability and resilience. Specifically, we focus on what capacities urban actors draw on to create sustainability and resilience and how different definitions of these concepts intersect, complement, or contradict each other. We then examine the implications of those intersections and differences in the efforts by urban actors to enhance the capacity to change unsustainable trajectories and transform themselves, their communities, and their cities toward sustainable and resilient relationships with the environment. Keywords: urban; sustainability; resilience; capacity; transformation 1. Introduction Urbanization and urban areas belong to a set of worldwide, multiscale phenomena that are profoundly altering the relationship between society and the environment, and affecting both urban and earth system sustainability and resilience in complex ways and at alarming rates. In recent decades, sustainability, resilience and transformation have become key concepts aimed at understanding and responding to an array of looming challenges posed by urbanization and environmental change. Yet, even though definitions and approaches to these concepts are ever-changing and highly contested, they revolve around common themes and ask large and compelling questions, such as these: How, with our growing world population, can we thrive (or even survive) on a warming planet with its degrading ecosystems? What kind of urban (or rural) lives do we want, and what kind of world could provide for those lives into the future? Furthermore, of critical importance to moving sustainability and resilience into practice, what capacities do we need to foster that will enable us to survive, or to transform our ways of living and thrive, both on and with our increasingly warm planet? [1,2] As compelling metaphors that convey the interactions and dependencies between urban areas and the ecosystems on which they depend, the evolving concepts of urban sustainability and resilience are associated with an expansion of research around sustainability and resilience science [3,4], and with Sustainability 2016, 8, 1224; doi:10.3390/su8121224 www.mdpi.com/journal/sustainability