Comparative study on two evaluating methods of ecosystem services at city-scale

The red line of ecological protection is significance in controlling the intensity of human activity and in maintaining ecological security and sustainability. China has already carried out a demarcation work of red line for ecological protection at national scale and is now nearing completion at provincial scale. Also the demarcation of red line for ecological protection at municipal scale is underway. However, in the process of delineating the red line for ecological protection, problems such as difficulty in classification, diversification of indicators, determination of scale and selection of evaluation methods have been encountered. The evaluation of ecosystem services is one important step in delineating red lines. Ecosystem service refers to any benefit that mankind can obtain from the ecosystem and it is the basis of human survival and modern civilization. Human neglect of ecosystem services and their importance has caused serious damage to critical natural ecosystems. Therefore, it is necessary to carry out an evaluation of ecosystem services. To standardize the evaluation of ecosystem services in China, the Technical Guidelines for the delineation of red lines for ecological protection issued by the Ministry of Ecology and Environment recommended the NPP quantitative index method and the model evaluation method to evaluate ecosystem services. As China has wide geographical extent with complex topographic features and natural conditions, it is important to evaluate the suitability of the two methods for application in demarcating red lines for ecological service evaluation. Based on MODIS remote sensing images, the evaluation of ecosystem services in Hebi City was carried out using the NPP quantitative index method and compared with the model evaluation method. The purpose of the paper was to select a more suitable evaluation method for the area and to provide theoretical basis for the demarcation of red line for ecological protection smaller-scale. In this study, we compared the results of the ecosystem service evaluation derived from the two different methods. The results showed that there was a significant difference between the NPP quantitative index method and the model evaluation method at prefectural city scale. In order to judge which method was more accurate, we compared the results of the two evaluation methods in terms of spatial distribution of the forest park. The model evaluation method was more consistent for high evaluation area of ecosystem services (soil and water conservation functions and biodiversity protection function) and the area with better ecological protection (area overlapping ratios of 19% and 85%, respectively) in Hebi City. The evaluation result of the NPP quantitative index method was not consistent with the protection status. The reason why the NPP quantitative index method was inaccurate was that the selected parameters and calculation formulas were not suitable for the study area. Therefore, the model evaluation method was more accurate for evaluating ecosystem services in the study area, compared with the NPP quantitative index method at prefectural city scale. Appropriate method should be selected according to actual local conditions in order to accurately evaluate ecosystem services in future studies. The comparative analysis in this study provided a reference point for evaluating ecosystem services and delineating red lines for ecological protection.