Assessing the overall sustainability of urban ecological-economic systems will contribute to producing valuable policies for sustainable urban development. Emergy analysis, which links the natural system to the social-economic system, has proved to be an efficient method to assess the sustainability of systems.
In this study, taking Simao District (Yunnan, China) as an example, an emergy-based framework was built to analyze the district’s sustainability. The study analyzed the resource utilization, environmental and economic efficiency of Simao through comprehensive consideration of its economic, social, and natural subsystem.
The emergy flow of Simao was concluded into six components: local renewable resource emergy, local nonrenewable extraction, imported nonrenewable resources, imported renewable resources, exported emergy and waste emergy. Emergy-based indicators such as empower density (ED), emergy yield ratio (EYR), emergy investment ratio (EIR), emergy sustainable index (ESI) and so on were calculated based on emergy flows.
Moreover, the value of ecosystem services, as a part of natural capital, shouldn’t have been ignored while calculating urban output. Therefore, we creatively regarded ecosystem services as a part of the output emergy, so that the invisible environmental output can be calculated.
Results/Conclusions
The results showed that the total emergy used (U), the emergy used per person (Ucap) and the ED of Simao were relatively at a low level compared to the selected developed cities, while the Ucap and the ED were both higher than the national average in China. The EYR of Simao was relatively low, while the EIR was higher than the province level, indicating that the development of Simao mainly depended on the outside investment. The ESI of Simao was lower than many highly developed cities, suggesting an unsustainable development in the long term.
Furthermore, the ecological services of Simao were also evaluated based on emergy, which indicated that Simao had provided huge ecological services and improved the ecological capacity of Yunnan Province. Policy insights for improving the overall sustainability of Simao are proposed, including adjusting industrial structure, facilitating green agriculture, and increasing renewable energy use.