Informing urban sustainability through cross-scale urban metabolism: Insights from Shanghai and the Yangtze River Delta

Abstract

Urban development is inherently connected to resource flows across city boundaries, which are associated with environmental impacts. To understand these dynamics, urban metabolism (UM) research conceptualizes cities as living systems and examines their complex interactions with surrounding environments.UM draws on diverse perspectives and methodologies, exploring not only material and energy flows but also broader systemic relationships within and beyond urban boundaries. However, much of the existing research focuses on intra-city metabolic processes, creating a critical gap in understanding how external metabolic activities influence internal urban systems. This study addresses this gap by proposing an innovative cross-scale urban metabolism model to investigate the interactions between internal and external metabolic systems, using Shanghai and the Yangtze River Delta (YRD) as a case study. By combining material flow analysis and ecological network analysis, the study uncovers the intricate structure of resource exchange and their effects on urban sustainability. The YRD region processes 3517 million tons of material flow distributed across 274 pathways, with Shanghai accounting for 7.3 % of the total metabolic flow. External metabolic activities substantially enhance the symbiosis, coordination, and stability of Shanghai's metabolic system. This study underscores the necessity of cross-scale urban metabolism research for understanding the broader urban-environment interactions critical to sustainability. By elucidating the role of external systems in optimizing urban metabolic processes, it offers valuable insights for guiding urban planning, resource management, and environmental policymaking, contributing to the sustainable development of cities like Shanghai.