Responses of urban ecosystem health to precipitation extreme: A case study in Beijing and Tianjin

Our research explores the relationship between precipitation extreme and urban ecosystem health by using emergy analysis based on urban ecosystem health assessment and Difference-in-Difference approach. In the case study area of Beijing and Tianjin, their urban ecosystem are getting healthier with the average growth rate of the key index, urban ecosystem health, are 0.23 and 0.12 respectively, simultaneously the overall index of Beijing is a little higher than that of Tianjin. Meanwhile, urban ecosystem seemingly has nothing to do with precipitation extreme, and the health of its urban sub-ecosystem performs significantly to the precipitation extreme except the sub-ecosystems, resilience, public services and human health. Vigor, one of the urban sub-ecosystems, its ecosystem health negatively associated with precipitation extreme. And urban sub-ecosystem health of vigor will reduce 14.42 if a precipitation extreme happens. The precipitation extreme has a positive effect on organization and emergies. And urban sub-ecosystem health of organization and emergies will increase 44.11, 12.02 respectively if a precipitation extreme happens. In addition, it is apparently nonsignificant to the sub-ecosystems, resilience, public services and human health. Moreover, the extreme precipitation consumes more emergies for the city, it seems beneficial for emergy flow for that precipitation extreme negatively affects emergy/dollar ratio, environmental loading rate and positively affects total emergy. But the extreme precipitation also negatively influences emergy yield ratio. Thus, urban ecosystem health associates with precipitation extreme in a complex way, both positively and negatively. Government measures for recovering urban ecosystem health should emphasize the sub-ecosystem vigor of the city, like constructing more public facilities. And policy makers may pay more attention on environmental loading rate, like advocating improving energy use efficiency.