Unraveling the quantity and sustainability of cross-scale ecosystem service flows: A meta-coupling framework perspective

Ecosystem service flows (ESFs) can reveal the interrelationships and impacts between natural systems and human activities. We can improve the stability and sustainability of ecosystems, more effectively utilize natural resources, protect the environment, and enhance the harmonious coexistence of humans and nature by comprehending ESFs. However, few studies have examined ESFs across scales and evaluated their sustainability; most have concentrated on regional scales. In order to quantify and analyze ESFs within the Jing River Basin (JRB) and between the JRB and the adjacent and distant regions from a water-food-energy perspective, this paper employs a meta-coupling framework. Additionally, it evaluates the sustainability of these flows using a techno-ecological synergy framework. The results show that the ESFs within the JRB was significant in 2020. Water production services were concentrated in the southern part of the JRB, while the distribution of food supply and carbon supply services was relatively even. Huan County emerged as the largest exporting county, providing 1.46×10⁸ kg of food to other counties and exporting 2.97×10⁶ kg of energy. The ESFs in the JRB primarily moved towards the neighboring and distant systems. Water production services flowed into the Guanzhong Plain Urban Agglomeration (GPUA), amounting to 5.8×10⁶ kg. Carbon supply services flowed out at 2.4×10⁵ kg, and food exports were the highest, reaching 5.0×10⁷ kg. The ecosystem service flows from the JRB to both the neighboring and distant systems enhanced food security and ecological resilience. The basin itself demonstrated good sustainability in food supply services, with an index value reaching 48.19. In cross-scale calculations of food production sustainability with the adjacent GPUA, the index value increased from 48.19 to 52.99, indicating a significant improvement. These findings demonstrate that applying the meta-coupling framework provides an effective approach to quantify ESFs and assess their sustainability across scales.