关键词: 社会资本, 红树林碳汇项目, 参照依赖, 演化博弈, 绿色PPP搭配高收益项目

Abstract: In 2021, China’s first mangrove carbon sink project (the Zhanjiang Mangrove Afforestation Project) was born, providing assistance for the achievement of the dual carbon goals. Mangrove carbon sink has the feature of high carbon fixation and sink increasing capacity and efficiency, which have long been considered as an effective way to achieve the goal of “carbon peak and carbon neutrality”. Increasing the development and promotion of mangrove carbon sink projects is a “three-win” approach to mitigating climate change, repairing mangrove ecosystems, and achieving carbon sequestration value. However, due to the large initial investment and long return period of the project, the funding demand and uncertainty for project development are also high. There are few existing project participants, and the market activity is not high. It is urgent to introduce diversified market participants to provide a breakthrough force for project development. However, existing research rarely discusses the specific paths and incentive strategies for social capital to participate in mangrove carbon sink projects, and the forms and implementation mechanisms of social capital participation need to be explored. And the existing research is limited to the single tool of government subsidies. In fact, in projects involving social capital, the incentive strategy of combining green PPP with high-yield projects (referred to as green PPP strategies) can also help promote project development.
In addition, the high investment threshold and development risks of carbon sink projects make social capital more dependent on the future returns of the project when making investment decisions. Specifically, when decision-makers make a certain choice, they will use a certain reference point as a benchmark, perceive the changes in the profit and loss of the selection results relative to that reference point, and thus decide whether to make a choice. Therefore, this study combines evolutionary game theory with reference dependency effect to analyze the behavioral strategies of social capital, government, and emission reduction enterprises under different government incentive strategies, providing reference for the design of incentive policies for driving the development of mangrove carbon sink projects in the future. Firstly, a tripartite evolutionary game model is established for the government, social capital, and emission reduction enterprises. Secondly, the interaction behavior of different stakeholders is described by establishing a replication dynamic equation. Finally, numerical simulation experiments are conducted to analyze the stability conditions and third-party strategy selection of the system under different parameters.
The research results indicate that: (1)Relying solely on subsidy strategies cannot have an effective incentive effect on social capital participation. (2)By relying solely on green PPP strategies, effective investment incentives can only be generated when the degree of risk aversion for returns is low and the degree of risk preference for losses is high. (3)The dual incentive strategy of subsidies and green PPP can alleviate the short-sighted behavior of social capital. (4)As the level of project performance reference points decreases and the level of social reputation reference points increases, the effectiveness of green PPP strategies on social capital investment incentives becomes apparent. (5)A low carbon tax will disrupt the evolutionary stability of cooperative investment between the government and social capital. Finally, targeted policy recommendations are put forward to promote the participation of social capital in mangrove carbon sink projects.

Key words: social capital, mangrove carbon sink project, reference dependency, evolutionary game, green PPP with high-yield project