Limiting factor analysis and regulation for urban ecosystems—A case study of Ningbo, China

Considering the importance of supporting system for the urban ecosystem development, the urban ecological carrying capacity (UECC) representing the supporting functions of biophysical environment for urban development is introduced into the analysis of urban ecosystem degradation. It is proposed in this paper that the urban ecosystem degradation can be attributed to the imbalance between supply and demand of UECC, i.e. the conflict between the infinite demand of urban development and finite supply of biophysical supporting system, which can be mainly described by the dominant limiting factors of UECC. Through the shortage indices of various factors that denoted by the ratio of the gap between the demand and supply to the demand, the limiting factors of UECC can be identified and graded with different levels. The urban ecosystem degradation can thus be regulated by adjusting the relationship of supply and demand in terms of limiting factors from both the layers of technical practice and goal-based government management. As for Ningbo City, the shortage of water resources quantity, the pressure of SO2 emission, insufficiency of sewage treatment and green area are the prominent limiting factors and corresponding regulation scheme is thereafter suggested to adjust the relationship between supply and demand of UECC.