Impact evaluation of coastal protection forest program on carbon sequestration change in East China

Forest carbon sequestration is an important nature-based solution for mitigating climate change. Despite significant investments allocated to the construction of coastal protection forests to mitigate climate change and environmental degradation, the effects of these conservation efforts have rarely been examined. This study evaluates the causal effects of China's Coastal Protection Forest Program (CPFP) on carbon sequestration changes in East China, focusing on program impact itself, time lag, and spatial heterogeneity. Using long-term forest inventory data (1999-2018) from 300 permanent plots, integrating biophysical and socioeconomic variables, we applied quasi-experimental matching methods to isolate program impacts. Our results showed that: (1) over the past 20 years, carbon sequestration per hectare of the coastal county forests in East China has surged by 2.3 times, with a total increase of 30.60 Mg C/ha at the plot scale; (2) different matching methods indicated that the CPFP had a significant and positive effect on carbon sequestration improvement, ranging from 16.84 to 18.98 Mg C/ha at the plot scale. In addition, significant positive time lag effects were observed across different time periods; and (3) the effect of CPFP on carbon sequestration change in the 0-10 km buffer zone was significantly lower than that in the 10-55 km buffer zone. Our study contributed to the sophisticated impact evaluation of coastal forest conservation policies, enhancing the understanding and management of conservation practices both in China and globally.