Towards a green world: the impact of the Belt and Road Initiative on the carbon intensity reduction of countries along the route

The Belt and Road Initiative (BRI) has attracted widespread attention since its implementation, especially the ecological effect. However, the net environmental impact of the BRI on countries along the route has rarely been directly assessed, though nearly 8 years after the BRI was proposed. This study quantitatively estimates the net effect, impact mechanism, and impact heterogeneity of the BRI on the carbon intensity reduction of countries along the route by adopting the difference-in-differences estimator based on propensity score matching, which enables a more convincing causal relationship between the BRI and the countries' ecological improvement. Research indicates that the BRI has significantly promoted the carbon intensity reduction of countries along the route, which is mainly achieved by boosting the growth of green economy (scale effect), the progress of green technology (technique effect), and the upgrading of industrial structure (composition effect). Moreover, the impact reveals obvious heterogeneity, manifested as the BRI has significantly promoted the carbon intensity reduction of countries with high institutional quality, high-income countries, and countries along the Silk Road Economic Belt, while its impacts on countries with low institutional quality, low-income countries, and countries along the 21st Century Maritime Silk Road are not significant. A series of validity tests further demonstrate the robustness of the estimation.