Urban ecosystem ecology has emerged as a crucial proving ground in the development of transdisciplinary approaches to both the study of coupled human natural systems and the effective management of human-dominated systems. A comprehensive socio-ecological theory of urban ecosystems still eludes the field, though application of a variety of integrating concepts such as ecosystem metabolism and ecosystem services has led to important progress. To address this need, the Urban Long-Term Research Area (ULTRA) program has generated a new network of research sites funded by the National Science Foundation and the US Forest Service. Teams of scientists and practitioners are conducting interdisciplinary research on the dynamic interactions between people and natural ecosystems in sub/urban settings in ways that advance both fundamental and applied knowledge. The current exploratory phase of the network includes 20 projects across the United States. This symposium and its companion (Stewardship in Urban Systems 2: Socio-ecology, Governance, and Equity in the ULTRA network) collectively bring together a multidisciplinary group of researchers from all 20 projects to share their approaches and findings. Speakers in this symposium will explore the ecological flows and interactions of materials and organisms in urban landscapes, and the resulting effects on ecosystem services. The session features 11 oral presentations (12 min + 3 min questions) that focus on the flows of material and organisms through sub/urban areas, particularly as people affect them. Speakers examine a range of topics, including tradeoffs between city-building and ecosystem services, and the biological and social aspects of water movement and use. The symposium juxtaposes presentations addressing vastly different ecoregions from Boston to Los Angeles to cities in Hawai’i and from mega-metropolises like New York City to small cities like Fresno, California. Two discussion / break periods provide opportunities to develop comparative approaches to urban ecosystem ecology.