A system dynamics simulation of marine economic development — evidence from Zhejiang province in China

As coastal economies transition from scale expansion to high-quality development, marine growth depends on coordinated industrial upgrading, innovation, port capacity, openness, and ecological protection. Existing research often treats these factors separately, overlooking delayed feedback, nonlinear constraints, and resilience to external shocks. This study models the marine economy as a complex adaptive system to examine how subsystem interactions shape long-term development. Using Zhejiang data for 2017–2030, we construct a system dynamics model integrating marine industry, technological innovation, port capacity, economic openness and cooperation, and ecological protection through causal-loop diagrams, stock-flow modeling, validation, and scenario simulation. Results identify a short-term masking effect in the innovation loop: weaker innovation does not immediately halt gross ocean product (GOP) growth because of inertia, but reduces the value added of emerging marine industries by approximately 16.7% relative to the 2030 baseline. Port capacity transmits effects between industrial expansion and ecological governance; a 60% decline in cargo throughput slows emerging-industry growth and constrains environmental investment. Marine ecological protection exhibits constraint-dependent nonlinear effects: it promotes GOP growth under weak constraints but slows it under strong constraints, while inducing a rise-then-fall pattern in the value added of emerging marine industries and a transition toward low-carbon logistics. Scenario simulations show that strong internal innovation support also improves resilience to severe external shocks, increasing projected 2030 GOP by about RMB 35 billion relative to the dual-negative-shock scenario. By revealing cross-subsystem feedback and shock-transmission mechanisms, this study advances marine economic analysis beyond static, single-factor approaches and informs coordinated policy design.