Objective With multiple ecological values, urban ecological space integrates various ecological regulating functions such as carbon sequestration and sink enhancement, water conservation, climate regulation, and soil and water conservation, among which carbon sequestration and sink enhancement has become a hotspot of global research in the context of the United Nations’ response to climate change. How to enhance the capacity of carbon sequestration and sink enhancement in diversified urban ecological spaces, and give full play to the synergistic effect of multiple regulating services, has become an issue that must be addressed in realizing the national carbon neutrality strategy and sustainable development. Evaluating ecological services in urban ecological space can help visualize the spatial distribution and evolution pattern of ecosystem services, intuitively understand the current ecological service capacity, quantify ecological value, and identify clusters of ecosystem services, which can reveal the numerical combination pattern and trend of individual services, and make it easy to examine the environmental resources and development trend of different regions, so as to maximize ecological benefits. Therefore, it is of great significance to optimize the layout of urban ecological space and contribute to the construction of ecological civilization by taking carbon sink enhancement as a starting point, comprehensively considering various types of ecosystem services, and proposing planning strategies for urban ecological space.
Methods Taking Wuhan City as an example, this research screens out five major modules related to the natural background of urban ecological space, namely carbon storage, habitat quality, water conservation, water purification and soil conservation, and evaluates individual ecosystem services using the five modules in the InVEST model. After that, the research adopts the SOM model for a cluster analysis, and finally identifies the number of ecosystem service clusters by considering the two dimensions of “minimization of intra-cluster and inter-cluster differences” and typicality of ecological spatial features. Based on this, the research imports the data obtained into the ArcGIS platform to carry out spatial mapping, and converts the values of ecosystem services into a graphic language, which helps understand the differences in the capacity of the analysis of the five categories of ecosystem services and their spatial distribution, and bring in a carbon sink perspective. The research finally revisits the ecosystem service clusters with a focus on the combined relationship between carbon and other ecosystem services. The above methodology can help visualize the spatial distribution of ecosystem services and the combination patterns of ecosystem service clusters, thus providing guidance for planning strategies and a basis for spatial decision-making.
Results According to their spatial distribution patterns and combination patterns, six types of ecosystem service clusters are identified, namely the ecological balance cluster, ecological conservation cluster, recreational water cluster, soil and water conservation cluster, habitat cluster and ecological fragility cluster. Among them, the ecological balance cluster and the ecological conservation cluster are distributed in the forested mountainous areas in northern and northeastern Wuhan, with high carbon storage, good habitat quality and synergistic development of ecosystem services, which belong to the carbon sink conservation area; the recreational water cluster and the soil and water conservation cluster are distributed in the main urban area as well as the suburban water bodies and cultivated lands, with strong water conservation and purification capacity and a certain carbon sink potential, which belong to the carbon sink potential area; the habitat cluster and the ecological fragility cluster are mostly distributed in the peri-urban areas with frequent human activities and around water bodies, which are featured by weak ecosystem services and belong to the carbon sink scarcity area.
Conclusion Reviewing the ecosystem service clusters from the perspective of the degree of carbon sink development can provide a new idea and method for the classification of different types of urban ecological spaces and carbon sink enhancement strategies. The method proposed in this research is highly operational and has significant results, which can effectively identify the distribution pattern of carbon sinks in urban ecological space, thus helping formulate differentiated carbon sink enhancement strategies, maximize the benefits of ecosystem services, and drive the synergistic development of ecosystem services, which is of great significance in optimizing the urban ecological spatial layout, and more importantly, can help realize the green and low-carbon development, provide a scientific basis for the construction of urban ecological civilization, and promote the achievement of the carbon peaking and carbon neutrality goals. This method can be widely used in similar researches on urban ecological spatial planning related to the enhancement of carbon sinks, and can also help other cities to realize the coordinated and sustainable development of the ecological environment and the economy and society.
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