Integrating ecological and socio-economic systems by carbon metabolism in a typical wetland city of China

Coastal wetlands serve as huge blue carbon sinks, whereas intense anthropogenic activities greatly changed the carbon sequestration, and then influenced carbon metabolism in coastal regions. Therefore, it’s essential to explore carbon metabolism from the perspective by integrating coastal ecosystems and socio-economic systems, thus identifying the key nodes for adapting to climate change. We used ecological network analysis (ENA) by the interaction and feedbacks of costal ecosystems and socio-economic system to trace the carbon flows for a typical wetland city in the Yellow River Delta, China, during 1995–2015. We found that the total carbon inputs showed an overall growing trend, which increased to 1.4 times its value. Although decreased by 15% in the coastal ecosystem, carbon inputs increased to 1.8 times in the socio-economic system. Carbon sequestration of coastal wetlands decreased by 43%, while carbon emission increased to 3.0 times its initial value in the coastal region. Heavy industry, crude oil, and atmosphere accounted for approximately 29%, 17%, and 9%, respectively, which most strongly influenced the network as the key nodes. Although the small direct flows of the macrophytes, they totally accounted for about 14%, whose effects could not be ignored for the coupled network. Network mutualism index for carbon metabolism was around 1.3. The ecological relationship distributions were basically the same in the study period, following the sequence of exploitation/control, mutualism and competition relationship. Based on the network control analysis, socio-economic sectors had the great control on atmosphere, and were mainly dependent on wetland resources suppliers. This study identified the key nodes and pathways in the coastal region metabolism system, and thus provided the targeted suggestions for policymakers to manage these nodes for wetland conservation and the sustainable development of coastal regions.