Allocation equity of regulating ecosystem services from blue-green infrastructures: A case study of street blocks in Wuhan central city

Rapid urban expansion has aggravated the degradation of ecosystem services (ES). The ES provided by blue-green infrastructure (BGI) is a critical factor influencing the urban environmental quality, and its allocation is closely associated with the life quality and equal rights of urban residents. Here, considering the major environmental problems in the urbanization process of Wuhan, nine components of ES related to four different types of BGI were selected for study. First, we quantified and mapped the provision of ES by various types of BGI based on a quantitative table obtained by reviewing the current literature on ES. Then, we illustrated the relationship between BGI and regulating ES (illustrated the characteristic of the ES provided by BGI) from the perspective of contribution rate and efficiency, and analyzed the allocation equity of regulating ES with some sociological methods. Based on the Gini index, our results showed that the allocation of regulating ES based on population is highly inequitable (0.70), while that based on space is relatively equitable (0.15) in Wuhan at the whole city scale. The Gini index was calculated for the nine ES components, including SO2 absorption, dust retention, runoff mitigation, precipitation infiltration, cooling, humidifying, noise absorption, carbon fixation and oxygen release. The results reveal that there are slight differences among different ES components. Although the mean value of PAL (population-average allocation level; 3.08) is higher than that of SAL (spatial-average allocation level; 0.72) in Wuhan, PAL has a much higher standard deviation than SAL, indicating the existence of significant gaps in PAL of ES among different blocks. Based on the integration of PAL and SAL, the blocks with relatively sufficient SAL and PAL of regulating ES were found to be mainly located in the northeast of the city, while those with very insufficient SAL and PAL of regulating ES are highly urbanized areas. Besides, the block with very insufficient SAL of regulating ES is located in urban industrial areas close to the suburbs, while those with insufficient PAL of regulating ES are scattered in the area close to the suburbs, respectively. Then, we proposed three priority levels and a judgment model for appropriate interventions based on allocation inequity in urban blocks. Our findings provide important implications for urban planning by associating ES with resident welfare.