Quantifying security and resilience of Chinese coastal urban ecosystems.

The emerging threat to the coastal urban ecosystems from increased intensity and frequency of weather events is a compelling reason for improving our understanding of the integrity of the existing ecosystem. Resilience of an ecosystem is a critical property that aids recovery and adaptation when subject to intense stress. Quantifying the resilience of an ecological system requires a detailed understanding of the vulnerabilities and interactions within a complex web of interconnected social, technological and economic networks. Through an ecological network analysis of ascendency and redundancy of the flux of energy and material flows, the causal relationships are established through structural equations modeling (SEM) techniques. A model based-on the five factors of driving force (D), pressure (P), state (S), impact (I), and response (R) (DPSIR), recognizes the different roles these factors play in the coastal urban ecological security system of China. Energy and material flows transmission equations of the ecological security network are developed to evaluate the resilience of the ecological security network. The results show that the ecological security network of Chinese coastal cities has a relatively high network occupation rate (A/C = 0.6898), indicating a relatively mature state of the ecological security network of coastal cities with sufficient metabolic capacity and steady status. The low vacancy rate (R/C = 0.3102) shows that the coastal ecological security network lacks flexibility of surplus space. The energy and material flows conversion and dissipation ability in the network are strong: the five factors of DPSIR are highly interdependent, and the ecological security network framework is both steady and mature. However, the resilience of the coastal urban ecosystem against external impacts is weak. It is critical for coastal cities to broaden their planning protocols to introduce more flexible space to increase resilience and guarantee a robust pathway for sustainable development. This study contributes to a rational method for testing the internal causal relationships among DPSIR linkages toward quantifying our understanding of the resilience of a security ecosystem.