Quantitative models for assessing the human-ocean system's sustainable development in coastal cities: The perspective of metabolic-recycling in the Bohai Sea Ring Area, China

• We devise quantitative models to assess the HOSSD in some coastal cities in China.
• Metabolic-recycling capability is the key element in the models.
• The results help us construct the spatial-temporal distribution pattern of HOSSD.
• We use the mean and standard deviation to classify the cities into four grades.
• Our method can guide policymakers toward enhancing sustainability in coastal zones.

Given that nearly half the human population lives in coastal areas, we urgently need new analytical models on how to maintain the ocean's capacity to sustain our progress. This paper introduces quantitative models for assessing the human-ocean system's sustainable development (HOSSD). The quantitative assessment models, consisting of the developmental degree (DD), harmonious degree (HD), and metabolic-recycling degree (MD), are constructed. The models are applied to measure the conditions of HOSSD in 17 coastal cities in the Bohai Sea Ring Area (BSRA) from 2000 to 2011. The kernel density estimation method is employed to analyze the dynamic evolution of HOSSD. The analysis of temporal variation reveals that the sustainable development levels of the cities were beginning to exhibit a polarized tendency by 2005 and that the gaps in sustainable development increased as a whole over the period 2000 to 2011. The spatial patterns for 17 cities are divided into 4 grades: strong, medium, weak, and very weak. The cities with weak or very weak sustainable development levels are mainly located in northwestern BSRA. The main influencing factors of HOSSD differ considerably between the 17 cities and 3 groups. Our approach allows the visualization of how these dimensions of HOSSD differ from city to city, providing important insights into short-term and long-term policies that may help enhance sustainability at a particular location.