3.3. Evaluation of cultural services
The Declaration on the Human Environment issued in 1972 emphasized the relationship between development and protection from the perspective of environmental protection. Subsequently, many countries started large-scale ecological restoration and urban ecosystem restoration in order to provide a happy living environment for urban residents through building a healthy ecosystem. Ecosystem health initially meant that the organization of the ecosystem was not damaged or weakened, and had a certain restoration ability (Costanza and Norton, 1992). Then, in the concept of ecosystem health, human health factors were introduced. It was believed that ecosystem health depended on the judgment by the whole social system, so human welfare should be considered. Therefore, more researchers focused on the urban development and residents’ perception of urban blue-green spaces and gradually emphasized cultural services supplied by blue-green spaces, including aesthetics, landscape, and mental health benefits (Table 3).
Xia Jihong (Xia, 2005) believed that an ecological riparian zone was a dynamic open water-land interlaced ecosystem, established a set of comprehensive evaluation index system for riparian ecosystem, and expounded the evaluation method of an ecological riparian zone from four perspectives, including structural stability, landscape suitability, ecological health, and safety. On this basis of the above system, ecological characteristic indices such as strong self-healing ability were introduced to carry out health evaluation of urban lakes and provide a theoretical basis for ecological restoration, planning, and construction of urban lakes (Wu et al. , 2020). According to the development characteristics of urban waterfront space, in order to build a modern economic-ecological-social city, ten principles of waterfront vitality were proposed and mainly involve ecological indices, public indices, full-time indices, accessible indices, hydrophilic indices, permeable indices, economic indices, mixed indices, sign indices, life indices and other indices (Zhang, 2009). A slow-travel-friendly waterfront strip park space evaluation system and scoring criteria were also established based on analytic hierarchy process (AHP), so that the friendliness of waterfront parks could be evaluated from three aspects: slow-travel paths, slow-travel facilities, and slow-travel landscapes (Zhong et al. , 2021).
In the history of the blue-green space evaluation index system, the evaluation indices have been gradually expanded from biological indices to habitat indices and human-related ecological service indices. The above history was basically consistent with the stages of urban development. Urban development has experienced the initial agricultural society, to industrial society and information society. Therefore, the demands for the environment has changed from material supply to habitat provision and cultural services. Therefore, the later blue-green space evaluation index systems retained the previous key indices that had an impact on ecological restoration and contained some relevant indices that were in line with the vitality of modern society, thus emphasizing the influence of the integrated natural ecosystem in blue-green spaces on ecological service function and urban development potential. The later system provided the basis for urban planning. In the future blue-green space evaluation index system, based on the concept of economic-society-ecological integration, the benefits of water bodies and green spaces related to social development and human well-being should be comprehensively considered. Qualitative and quantitative indices make the evaluation results more accurate and can better reflect the quality of a blue-green space (Table 3).