Dynamic Assessment and Change Analysis of Ecosystem Service Value Based on Physical Assessment Method in Cili County, China

The effective implementation of ecological protection policies requires the adequate assessment of temporal and spatial changes in the environment. To understand how ecosystem services can be used to track environmental changes, we carried out a study which focused on assessing the changes in the ecosystem services over time and space in Cili County, which is an important forestry region. The method we used was to evaluate the value of the regional ecological services based on the method for evaluating the value equivalent factor per unit area; then, by introducing multi-source data, the InVEST model was optimized to accurately assess the function of the regional ecosystem services, such as carbon storage, soil conservation, and water production. In addition, the values of the ecosystem services and the function assessment results were compared. Finally, based on the results of the optimized InVEST model, the value of the ecosystem services in the study area was regulated and re-evaluated. After re-evaluation, the total value of the ecosystem services in Cili county between 2000 and 2020 still showed an upward trend, increasing from CNY 26.136 billion to CNY 35.444 billion, with a total increase of CNY 9.308 billion. Compared to before the re-evaluation, the total value of the ecosystem services only increased from CNY 32.243 billion to CNY 32.473 billion, with a total increase of CNY 0.23 billion; the change in the value of the ecosystem services was more obvious, with a stronger spatial heterogeneity. The areas with high ecosystem service value in Cili County are mainly concentrated in the eastern parts, as well as the northwestern and southern parts, while the areas with low value are mainly concentrated in the central part of Cili County. The value of the central, southern, and northwestern parts of Cili County increased significantly. Such changes are closely related to China's implementation of ecological protection policies in this region since 2000, such as returning farmland to forest and natural forest protection. The evaluation results of the ecosystem services and the method for evaluating the value equivalent factor in this study are more consistent with the changes in the ecosystem services in the study area. The dynamic assessment method of ecosystem service value proposed in this study is helpful in achieving accurate assessments of the regional ecosystem services and thus provides a useful reference for the formulation of more reasonable regional ecological protection policies.