What dominates the variation of ecosystem services across different urban expansion patterns?-Evidence from the Yangtze River Delta region, China

Urban expansion is considered to be a major driver of ecosystem services (ESs) loss, and variation of ESs in rapidly urbanizing areas are of great concern. Clarifying the relationship between urban expansion and ecosystem services (ESs) and understanding the impact of socio-ecological drivers on ESs are crucial for sustainable urban development and ecological conservation. However, the differential impacts of urban expansion on the variation of ecosystem services across different urban expansion patterns and the dominant drivers of these variation, have not been fully explored, hampering the formulation of sustainable urban development plans. To address these knowledge gaps, we assessed the differential impact of three urban expansion patterns (edge-spreading, interior-filling and leap-frogging) on five representative ESs-carbon sequestration, food production, habitat quality, soil retention and water yield-in the Yangtze River Delta region (YRDR) of China. We applied random forest model to quantify the impact of ten social-ecological drivers on the variation of ESs across three urban expansion patterns. Our findings revealed that edge-spreading is the main pattern of urban expansion and it leads to higher losses of the three key ESs, which is therefore more significant than that caused by interior-filling and leap-frogging. Although the loss of ESs due to urban expansion was primarily driven by changes in natural drivers, social drivers had a variable and sometimes powerful influence on ESs. The differences in the impact of dominant socio-ecological drivers on the variation of ESs across different expansion patterns are mainly reflected in the relative importance. Moreover, the overall explanatory power of socio-ecological drivers on the variation of ESs under leap-frogging expansion was low. We suggest that different ESs protection strategies should be developed and implemented for different urban expansion patterns to achieve a balance between urban development and ecosystem protection. This study can provide an opportunity to formulate refined urban development plans for the sustainable development of human-environment systems in rapidly urbanizing regions.