5. Conclusions and Outlook
Due to rapid urban development, the environmental hotspot has changed from initial supply services to the later regulation function, and then to the current cultural service function. Urban development has gradually shifted from the initial orientation to economic construction to people-oriented development. The blue-green space system, in which water bodies and green spaces are intertwined and continuously integrated, can promote the sustainable development of urban natural systems, the construction of livable cities, and the improvement in urban vitality. In the review, the development process of the blue-green space evaluation index system is summarized because of previous studies. The relationships between water bodies, green spaces, and blue-green spaces and the complex structures and functions of blue-green spaces are analyzed as a composite ecosystem in order to provide the basis for subsequent blue-green space planning.
In existing studies on blue-green spaces, blue spaces and green spaces are separately evaluated and a combined evaluation index system for blue-green spaces is not available. The suggestions are provided as follows:
1) The indices of water bodies and green spaces should be comprehensively considered, in order to evaluate the blue-green space. The blue-green space is a complex system composed of water and green spaces. The mutual influence between water and green spaces form ecological service functions, unlike that in a single water body or a green space. Therefore, in the evaluation of a blue-green space, it is necessary to select indices considering water and green spaces for comprehensive evaluation.
2) People-oriented urban construction is significant. Urban blue-green spaces have environmental landscape functions and ecological service benefits and provide residents with space for recreational activities, thereby increasing residents’ physical activities, promoting social interaction and integration, and bringing positive effects to the public’s physical and mental health. In other words, the construction quality of blue-green spaces is closely related to the happiness and quality of life of urban residents. Therefore, the selection of indices should reflect the ecological service function or social function for human beings.
3) Multi-scale and periodic evaluation are recommended. According to the size of the range, blue-green spaces can be classified into large blue-green spaces and micro blue-green spaces. According to different scales of evaluation objects, a multi-scale evaluation index system with the hierarchy of “city-district-community-people” can be constructed to cover the macroscopic whole area and an individual. In addition, the constructed evaluation index system should be based on the overall planning of urban and rural areas and the “people-oriented” planning idea. It is necessary to improve the supervision mechanism and establish a periodic evaluation system. Long-term monitoring and evaluation can provide the basis for improving urban planning quality and subsequent construction.