Differentiated impacts of urban expansion patterns on ecosystem services and their socio-ecological drivers: Evidence from the Pearl River Delta urban agglomeration in China

Urban expansion can alter ecosystem services (ES), yet the effects of different expansion patterns and their socio-ecological drivers remain insufficiently understood. The study focused on the Pearl River Delta urban agglomeration (PRD) to understand how different geometric expansion types influence regional ES. The Landscape Expansion Index (LEI) was used to identify interior-filling, edge-spreading, and leap-frogging expansion, while the InVEST model assessed changes in habitat quality, carbon sequestration, soil retention, water yield, and food production. A Random Forest model was further employed to identify the relative importance of ten socio-ecological drivers under different expansion patterns. The results showed a clear spatial gradient, with interior-filling concentrated in the urban core, edge-spreading dominant in the middle belt, and leap-frogging more common in peripheral areas. Carbon sequestration, habitat quality, and food production declined over 2000–2020, with net changes of −11.86 × 10 8 gC, −21.67 × 10 4 , and −17.12 × 10 5 t, respectively, while soil retention decreased by 7.73 × 10 6 t. Water yield increased by 7.24 × 10 7 mm despite declines during the early periods. Edge-spreading generated the largest absolute ES losses because of its extensive spatial footprint, whereas interior-filling produced the highest ES loss intensity per unit area. The driving mechanisms also differed among patterns: edge-spreading was more sensitive to topography and precipitation, while interior-filling was more strongly associated with socioeconomic factors. Leap-frogging had smaller regional effects but may increase local risks such as habitat fragmentation, soil erosion, and reduced ecological connectivity. These findings suggest that urban growth should be managed according to expansion patterns, with ecological land around urban fringes protected during edge-spreading, ecological safeguards strengthened during interior development, and green infrastructure improved in areas affected by leap-frogging expansion.