This Issue Paper outlines the importance of ecosystems to cities. The social and economic systems that visibly constitute cities are built upon the ecosystems that they supplant, and are perpetually reliant on the flow of ecosystem services both within and beyond the city. The content of this Issue Paper has relevance to various others, in which can be found elements that are discussed here in more, or less, detail. Specifically the topics covered in Issue Paper 6 on Urban Governance; Issue Paper 8 on Urban and Spatial Planning; Issue Paper 10 on Urban-rural Linkages; Issue Paper 11 on Public Space; Issue Paper 15 on Urban Resilience; and Issue Paper 17 on Cities &Climate Change & Disaster Risk Management; have relevance to the current Issue Paper on Urban Ecosystems and Resource Management