Mapping ecosystem service supply and demand dynamics under rapid urban expansion: A case study in the Yangtze River Delta of China

Much remains to be learned about the contributions of urban expansion to the supply–demand budgets of ecosystem services (ES), a relationship that is crucial for achieving more sustainable urbanization. To fill this knowledge gap, we mapped supply and demand dynamics of two important ES (i.e., carbon sequestration and nature-based recreation) at 1-km resolution in the rapidly urbanizing Yangtze River Delta (YRD) of China. Carbon sequestration supply (CSS) and demand (CSD) were estimated under alternative carbon reduction policies, and supply (NRS) of and demand (NRD) for nature-based recreation were estimated by considering multiple levels of spatial accessibility. A moderate increase in CSS between 2000 and 2015 was contrasted with a sharp increase in CSD, indicating the existence of a widening gap between demand and supply in the YRD. Urban expansion was responsible for nine-tenths of the total increase in CSD and two-thirds of the growth in deficit area. As of 2015, CSS offset less than 5% of CSD in the eight core cities of the YRD. The areas of deficient CSS in these eight cities expanded by 8% under the long-term carbon neutrality goal, but they shrank by 34% due to significant decreases in carbon emissions per unit of GDP under the mid-term carbon reduction goal. NRS in the YRD decreased slightly coincident with moderate increases in NRD during the same period as a result of urban expansion and population growth. More than half of the increased deficit area was attributable to urban expansion across the region. NRD in the eight core cities equaled four-fifths of NRS in 2000, but it surpassed NRS by one-fifth in 2015. The disparities between NRS and NRD in these eight cities were reduced with increasing levels of accessibility to ecological land. Bridging the gaps between supply of and demand for these two ES will require control of unsustainable urban expansion, construction of urban-to-rural greenways, and improved economic efficiency of industrial carbon emissions in the YRD. The analytical framework and methods for mapping ES used here are applicable to other rapidly urbanizing regions of the world.