Spatiotemporal variation of essential ecosystem services and their trade-off/synergy along with rapid urbanization in the Lower Pearl River Basin, China

The Lower Pearl River Basin (LPRB) of China has witnessed the rapidest urbanization in the world, along with which there has been significant spatiotemporal heterogeneity of essential ecosystem services and their trade-off/synergy within this rapid urbanization region. This study firstly explored the spatiotemporal heterogeneity of three essential ecosystem services (i.e., the carbon sequestration service, habitat quality and water yield) in the LPRB with the Integrated Valuation of Ecosystem Services and Trade-offs model based on time-series data during 1990-2015. This study then categorized the study area into different urbanization areas according to the urbanization level, and thereafter separately revealed the trade-off/synergy between these ecosystem services with correlation analysis on the sub-watershed scale. Results suggested the carbon sequestration service and habitat quality in the whole study area showed a slightly decreasing trend, while the water yield in the whole study area showed significant inter-annual fluctuation. Besides, there were obvious differences in the trade-off/synergy between three essential ecosystem services in different urbanization areas, indicating urbanization had important impacts on these ecosystem services and their trade-off/synergy. Specifically, there was always a significant synergy between the carbon sequestration service and habitat quality, which tended to decline and then keep stable as urbanization proceeds. While there was a trade-off between the carbon sequestration service and water yield, which tended to be firstly stronger and significant but then weaker and insignificant as urbanization proceeds. By contrast, there tended to be a decreasing but still significant trade-off between the habitat quality and water yield as urbanization proceeds. Moreover, there was an unusual trade-off/synergy between the water yield and the other two ecosystem services in 1990 and 2015, which was primarily due to the significant spatial variation of some relatively unstable factors (e.g., precipitation). It is necessary to take proper measures (e.g., sponge city construction, water transfer projects) to cope with the effects of these relatively unstable factors on the essential ecosystem services as urbanization proceeds. The results of this study can provide valuable supporting information for land use management to guarantee sustainable provision of essential ecosystem services in these rapid urbanization areas.