Spatiotemporal coupling analysis between human footprint and ecosystem service value in the highly urbanized Pearl River Delta urban Agglomeration, China

Ecosystems provide multiple benefits that humans depend on for survival. However, humans severely affect ecosystems through urban sprawl and pollution, and ecosystem functions are therefore constrained. In order to explore the evolution of the human-ecosystem relationship and changes in ecological conditions in highly urbanized areas, this study takes the Pearl River Delta Urban Agglomeration (PRDUA) as the study area, and the ecosystem service values (ESV) and the human footprint (HF) index during 2000-2020 were evaluated. We also employed the four-quadrant model and coupling index to reveal the synergistic relationship and interaction intensity between ESV and HF. Results showed: (1) From 2000 to 2020, the core area of PRDUA exhibited low ESV and high HF, while the peripheral area presented high ESV and low HF. Temporally, over 46% of the PRDUA took on high and very high levels of HF during 2000-2020. ESV declined by over 9% in all 9 cities in the PRDUA. (2) Most of the PRDUA areas were in Quadrants II and IV, and the proportion of these two quadrants increased by 4.4% and 4.5% during 2000-2020, respectively. This indicates that the urbanization process is still ongoing in the PRDUA. The area in Quadrant IV had the lowest coupling index of 0.678 on average during 2000-2020, indicating that the interaction intensity between HF and ESV was significantly lower than in the other areas. (3) The relationship between HF and the coupling index showed an inverted U-shaped curve. This indicates that during urbanization, as human activity intensity grows, the intensity of human-ecosystem interaction increases and then turns down when it reaches a certain threshold. By revealing the changes in the human-ecosystem relationship in a highly urbanized area, this study provides theoretical guidance for ecological regulation and planning in such areas.