Assessing inter-city ecological and economic relations: An emergy-based conceptual model

Inter-city relation, though of great importance in the context of an increasingly globalized society, has rarely been addressed quantitatively compared to the structure and function within the city due to the difficulties when acquiring and disposing the relational data between cities. In this study, we presented a conceptual model for quantifying the inter-city relation in ecological and economic contexts based on emergy analysis, which is recognized as a promising approach to evaluating various city flows on a common basis. Emergy diagram of an urban system was constructed explicitly, and the related relational data indices were selected from the ecological and economic aspects, respectively, to form two indicator systems for emergy analysis, incorporating the transfer of labor, material and currency, etc. After that, the inter-city interaction intensity and sustainability were formulated to identify the sustainable conditions between the two cities, and hopefully, it could reveal potential complementarity or competition between the cities over time. With the introduction of emergy analysis, this study may provide a new way to quantify city interaction.