· The structure of urban systems includes human and nonhuman organisms; abiotic components such as soil, water, land, climate, buildings, roads, and technological infrastructure; social institutions; politics and governance; and economic drivers—all of which interact to produce the observable functions of urban systems. · Humans interact dynamically within social-ecological-technical/built system (SETS) components. · Delineating boundaries and defining response units are crucial for empirical research, as is understanding the influences, material, and energy that cross boundaries. · Urban ecosystem function emerges from the interactions, relationships, and feedbacks of system components. · Urban systems are spatially heterogeneous and temporally dynamic. · Linking urban system patterns with processes at multiple scales is a primary focus. · Conceptual frameworks must work across multiple spatial and temporal scales. · Conceptual frameworks must incorporate key, well-described drivers of urban system dynamics, including social, ecological, political, economic, and technical processes. · The relationship among urban form, heterogeneous spatial structure, and system functions must be known to theorize and measure ecosystem services. · Conceptual frameworks must be designed to enable comparative studies across cities. |