Spatial matching and value transfer assessment of ecosystem services supply and demand in urban agglomerations: A case study of the Guangdong-Hong Kong-Macao Greater Bay area in China

Due to the high intensity of urban construction and human intervention, the imbalance between ecosystem service supply and demand (ESSD) in urban agglomerations is deteriorating. The quantitative study of ecosystem service flow (ESF), as a critical process connecting ESSD, can assist decision-makers in accurately identifying the potential for ecological cooperation among cities, solving the conflict between ESSD in urban agglomerations, promoting regional ecological integration, and achieving sustainable and healthy development. Currently, quantitative research on ESF is focused chiefly on flow direction identification. However, the relationship between ESSD and ESF, flow scope, path, and rate measurement, are still in the exploratory stage. Using the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) as an example, this paper evaluated the four ESSDs based on the InVEST model: habitat quality (HQ), carbon storage (CS), water yield (WY), and soil retention (SR), and quantified the comprehensive economic value of the four ESSDs using the alternative cost method with the city/ county as the basic units. Finally, utilizing the breakpoint model and the field intensity model, we built an ESF value transfer model and estimated the value of ESFs transmitted from ESSD surplus cities/counties to the deficit in the GBA. The findings revealed an imbalance between ESSD in the GBA, with most of them being in severe ESSD deficit or surplus, and ESFs had played a key role in improving this. The primary transfer out locations (TOL) of ESFs were Huizhou, Zhaoqing, and Jiangmen. In contrast, the primary transfer in locations (TIL) of ESFs were Guangzhou, Shenzhen, Foshan, and other highly urbanized areas. The total value of ESFs in the GBA was as high as 4.218 billion yuan. As an attempt toward quantifying the ESF, this work provides a framework for the future establishment of scientific ecological compensation norms for urban agglomerations to encourage benign and equitable ecological exchanges between cities/counties.