In recent years, China's economic development has been significantly improved, but at the same time, a large number of pollution emissions have also been produced, greatly destroying the ecological environment. Environmental conflicts caused by environmental pollution are constantly emerging in China, and gradually become one of the negative factors that affect social stability. Then, when economic development brings environmental pollution, does it also bring environmental conflicts as the byproduct? However, the empirical research on the relationship between economic development and environmental conflicts is still very scarce. On the one hand, economic development promotes the individuals' income level, but also improves the individuals' environmental preference and rights awareness, providing the conditions for environmental conflicts. On the other hand, as one of the main byproducts of economic development, environmental pollution mainly accounts for environmental conflicts. Economic development can indirectly bring out environmental conflicts by producing environmental pollution, but high-level economic development may also make the ecological environment gradually improved, thereby inhibiting environmental conflicts. Therefore, when examining the impact mechanism of economic development on environmental conflicts, it is necessary to distinguish the direct and indirect effects of economic development on environmental conflicts.

Through a two-stage regression model, this paper estimates the impact mechanism of economic development on environmental conflicts for the first time based on panel data of 30 provinces from 1998 to 2013. In the two-stage regression model, the first stage regression model is used to estimate the net effect of economic development on environmental pollution. By using the fitting value of environmental pollution in the first-stage regression, we estimate the direct impacts of economic development and environmental pollution on environmental conflicts in the second-stage regression after controlling legal environment, income inequality, urbanization and other factors affecting environmental conflicts. Then, we combine the estimation coefficients of the first-stage regression with the estimation coefficients of the second-stage regression to calculate the indirect effect of economic development on environmental conflicts. In addition, individuals' environmental preference may have a diminishing marginal effect, so we further investigate the impacts of economic development at different levels on environmental conflicts by constructing a panel threshold regression model.

The results suggest that economic development has promoted the residents' environmental preference and rights awareness, and also destroys the ecological environment, being the main causes of environmental conflicts. In this sense, environmental conflicts are the byproduct of economic development. But this does not mean that the environment conflicts will continue to grow as economic development improves. The indirect effects show further economic development can optimize the economic structure, improve production technology and then the environmental quality and thus have an inhibitory effect on environmental conflicts. Moreover, the results of testing the threshold model confirm that when the economic development level has reached a certain level, individuals' environmental preference suffers from diminishing marginal effect. Therefore, environmental conflicts gradually decrease as the economy develops as a whole. The research of this paper is of great significance to the clarification of the relationship between economic development and environmental conflicts, effective prevention and control of environmental conflicts and the maintenance of social stability and sustainable development.