Measurement of Forest Carbon Sink Efficiency and Its Influencing Factors Empirical Evidence from China

The efficiency and productivity improvement are the core requirements of high-quality development, while improving the efficiency of forest carbon sinks is an important means and fundamental way to achieve their high-quality development. Based on the forests and socioeconomic development data of 31 provinces (cities and districts) in China from 2004 to 2018, the biomass method and DEA-Tobit panel regression model were used to analyze the level of forest carbon stock, carbon sink and carbon sink efficiency, and factors influencing forest carbon sink efficiency in China's provinces. The results indicated that: (1) nationwide forest carbon stocks and carbon sinks increased successively while carbon density decreased. The regions with higher carbon stock, carbon sink, and carbon density were concentrated in the northeast and southwest forest areas with abundant forest resources. (2) During the 7th to 9th forest inventory, the efficiency of forest carbon sinks was on a low and decreasing trend. The mean values of comprehensive efficiency in general for the 7th to 9th forest inventory periods were 0.421 and 0.336, respectively. The scale efficiency in the decomposition efficiency was above 0.650 for both inventory periods, and gradually increased, showing that the gap between the actual scale and the optimal production scale of forestry carbon sink was decreasing. The pure technical efficiency level represented the production efficiency of input factors at the optimal scale of forestry carbon sinks. The mean values of the two periods are 0.639 and 0.514, respectively, while the differences within the production frontier surface are 0.361 and 0.486, which indicates that there is input redundancy or output deficiency in the two periods as a whole. (3) The total annual precipitation and the level of socioeconomic development have significant driving effects on the improvement of forest carbon sink efficiency, while the incidence of pests and diseases, abnormal changes in temperature, afforestation area and the development of population urbanization have significant inhibiting effects on the improvement of forest carbon sink efficiency in China.