No abstract

City and regional planners have recently started exploring a circular approach to urban development. Meanwhile, industrial ecologists have been designing and refining methodologies to quantify and locate material flows and stocks within systems. This Perspective explores to which extent material stock studies can contribute to urban circularity, focusing on the built environment. We conducted a critical literature review of material stock studies that claim they contribute to circular cities. We classified each article according to a matrix we developed leveraging existing circular built environment frameworks of urban planning, architecture, and civil engineering and included the terminology of material stock studies. We found that, out of 271 studies, only 132 provided information that could be relevant to the implementation of circular cities, albeit to vastly different degrees of effectiveness. Of these 132, only 26 reported their results in a spatially explicit manner, which is fundamental to the effective actuation of circular city strategies. We argue that future research should strive to provide spatial data, avoid being siloed, and increase engagement with other sociopolitical fields to address the different needs of the relevant stakeholders for urban circularity.

No abstract

Ecological efficiency (eco-efficiency) is the effectiveness of ecological resources in meeting human needs and is a good representation of the quality of a region's development. The traditional concept of improving eco-efficiency refers to maximizing economic benefits by minimizing resource costs and environmental loads. This article argues that the goal of eco-efficiency evaluation is not only to maximize economic benefits but also to achieve high-quality and coordinated development in many aspects so that more people can enjoy the fruits of development. Therefore, in the evaluation system of eco-efficiency, the input indexes take into account the consumption of human, energy resources, and the environmental load caused by them in a region. The output indexes take into account the four dimensions of "economy, innovation, social harmony, and openness." This study first establishes the nonexpected output superefficiency slacks-based measure model under the assumption of variable returns to scale to measure eco-efficiency in 11 cities of Zhejiang Province, China. Second, the spatial and temporal trends of eco-efficiency are studied with the help of the Malmquist index model. Moreover, regression analysis was conducted using the panel Tobit method to discuss the influencing factors of eco-efficiency. Several key results were obtained in this study: (1) The overall eco-efficiency in Zhejiang Province is rising steadily, but there are serious regional imbalances. (2) The improvement of eco-efficiency mainly relied on the scale efficiency from 2008 to 2013, but on pure technical efficiency from 2013 to 2018. (3) The share of tertiary industry, the number of scientific researchers, and the foreign trade dependence positively affect the improvement of eco-efficiency, but highway transportation mileage has a negative impact on the improvement of eco-efficiency.