In the year 2003, the Stockholm Urban Assessment (SUA) was selected as a sub-global assessment within the global Millennium Ecosystem Assessment (MA, Ecosystems and human well-being: synthesis. Island Press, Washington, DC, 2005). This chapter revisits SUA and fills in important knowledge gaps in the assessment as well as provides insights on urban resilience building. The chapter applies a critical perspective on the present urban development trajectory of the Stockholm metropolitan area. It emphasizes the need to understand ways in which informally managed green spaces contribute to ecological functions in urban settings. The chapter provides a background of the Stockholm region and the current challenges it faces, followed by a synthesis of the major insights conveyed in SUA related to informal ecosystem management. The chapter concludes by proposing policy recommendations of general implications for urban resilience building.