Abstract: Urban inland rivers are vital components of the urban water environment, playing a crucial role in shaping the aesthetic, ecological, and social structure of cities. These rivers significantly enhance the environmental quality of urban areas, influencing green development, urban landscapes, and the health and well-being of residents. The ideal state of urban inland rivers characterized by “smooth waterway, clear water, green bank, and scenic beauty” represents the aspirations of city dwellers. In 2021, the proportion of black and odorous water bodies in Chinese cities was reduced by over 98% through the joint governance efforts of government, market forces, and societal organizations. This achievement demonstrates the effectiveness of multi-stakeholder governance, yet illegal wastewater discharges from industrial enterprises continue to undermine these efforts. The re-emergence of “black and odorous” water in some urban inland rivers indicates that pollution control remains an ongoing challenge. Therefore, regulating enterprises to ensure legal wastewater discharge and addressing the long-term management of urban inland rivers have become a central focus of current policy efforts. In practical terms, the role of government-purchased services in advancing ecological civilization has become increasingly important. Government procurement of services is seen as a key mechanism for guiding multiple stakeholders in controlling pollution, and it is expected to become a crucial measure for the long-term governance of urban inland river ecosystems.
This paper aims to address the potential “government failure” and “market failure” that may arise in multi-stakeholder governance by exploring how local governments incentivize environmental protection social organizations (ENGO) through service procurement. ENGO, in turn, collaborates with the public to engage in informal environmental regulation to supervise enterprises and ensure legal wastewater discharge. To investigate this mechanism, a four-party evolutionary game model is constructed, incorporating local governments, polluting enterprises, ENGO, and the public. The equilibrium of each player in the game is analyzed, resulting in the identification of eleven stable evolutionary points. These points are further classified and analyzed for their stability. Additionally, numerical simulations are conducted to study how changes in key parameters—such as government incentives, ENGO influence, and public participation—affect the stable strategies of the different players involved.
The findings indicate that: (1)Strengthening local government efforts in purchasing services significantly promotes the active engagement of ENGO in service provision, thereby facilitating the system’s convergence toward an ideal stable state. Polluting enterprises exhibit greater sensitivity to subsidies provided by local governments compared to fines. However, the combination of subsidy and fine policies proves more effective in expediting the system’s transition toward the desired equilibrium. Furthermore, raising the environmental protection tax rate serves to incentivize enterprises to engage in lawful pollutant discharge practices. (2)Enhancing the influence and environmental enforcement capacity of ENGO can regulate the legal discharge of pollutants by enterprises to varying degrees, thereby encouraging them to assume greater environmental responsibility. (3)Increasing public reporting efforts has a relatively limited impact on system evolution, although local government incentives have led to a short-term increase in public willingness to report violations. (4)Sensitivity analysis reveals that changes in local government service purchase efforts are more likely to prompt alterations in the decision-making behavior of polluting enterprises, while modifications in ENGO influence and environmental enforcement efforts more significantly affect the decisions of both enterprises and the public. (5)The initial willingness of different stakeholders to participate affects the evolution of the system in varying ways. However, a high level of participation willingness among stakeholders plays a positive role in accelerating the system’s convergence toward the ideal stable state. Specifically, when ENGO with high participation willingness supervises the pollutant discharge behavior of enterprises through informal environmental regulation methods, these enterprises no longer attempt to engage in illegal pollutant discharge practices. This indicates that the participation willingness of ENGO is a decisive factor in shaping the pollution control intentions of enterprises, highlighting the urgent need for governments to enhance the participation willingness of ENGO.
In light of these findings, this paper develops a mechanism for the long-term governance of urban river ecosystems under the synergistic effect of formal and informal environmental regulation. The proposed mechanism comprises three primary components: the service purchase mechanism, the incentive and constraint mechanism, and the reputation influence mechanism. Additionally, this paper outlines effective safeguard measures tailored to each component. From the perspectives of both local governments and ENGO, policy recommendations for enhancing urban river ecosystem governance are also presented.

Key words: urban river, ecological environment governance, government purchase of services, ENGO, quadrilateral evolutionary game

摘要： 政府购买服务是促进多方主体共同治理污染的有效途径,对于实现城市内河生态环境的长效治理具有重要意义。本研究旨在解决多元共治过程中可能出现的“政府失灵”和“市场失灵”问题,探讨地方政府如何通过购买服务激励环保社会组织(ENGO),并联合公众实施非正式环境规制,以监督企业合法排污。为此,我们构建了一个包含地方政府、排污企业、ENGO和公众在内的四方演化博弈模型,分析了各主体的策略演化,并运用数值仿真模拟了参数变化对各主体稳定策略的影响。研究发现:(1)地方政府增加服务购买力度能有效激励ENGO积极参与服务;排污企业对地方政府的补贴政策比罚款更为敏感;提高环境保护税标准有助于促进企业合法排污;(2)增强ENGO的影响力和环保力度可以在不同程度上规制企业合法排污,促使企业承担环境责任;(3)提高公众举报力度对系统演化的影响不大,但地方政府的奖励措施能在短期内提升公众的举报意愿。基于这些发现,本文提出了针对城市内河生态环境治理的政策建议。

关键词: 城市内河, 生态环境治理, 政府购买服务, ENGO, 四方演化博弈