How do heterogeneous environmental regulations affect the sustainable development of marine green economy? Empirical evidence from China's coastal areas

Under the dual constraints of environment and resources, it is imperative for China to achieve sustainable development of its marine economy through establishing effective mechanisms and intensifying environmental regulations to promote green transformation of the marine economy. By incorporating both marine economic development factors and environmental pollution factors into the marine green economy development evaluation system, this study measures the marine green economic efficiency (MGEE) in China. On this basis, the dynamic panel smoothed transition regression model is used to analyze the nonlinear effect and transition mechanisms between environmental regulation and marine green economic efficiency, and the heterogeneous effects of market-based and command-and-control environmental regulation tools are examined by distinguishing the forms of environmental regulation as well as regional development differences. The findings are as follows: ①under the setting of different transition variables, both market-based environmental regulation (MER) and command-and-control environmental regulation (CER) exhibit a non-linear relationship with MGEE during the transition between the high regime and the low regime. ②Both CER and MER contribute positively to the advancement of MGEE after exceeding certain thresholds through changes in the marine industry structure (MIS) and marine technology innovation (MTI). The driving impact of CER is noticeably stronger than that of MER after the threshold of MIS is exceeded, whereas the driving effect of MER is stronger after the threshold of MTI is exceeded. ③When foreign direct investment (FDI) is considered as the transition variable, CER consistently inhibits the growth of MGEE, however, MER's impact progressively changes from negative to positive with FDI surpassing the threshold.