Table 1.

Research gaps on PES programs in the context of telecoupling framework

Components of the telecoupling framework (2)	Definitions of the telecoupling components with regard to PES	Specific telecoupling components studied or not studied by Zheng et al. (1)
Sending systems	Systems that provide ecosystem services	Upstream of Miyun Reservoir watershed in Hebei Province
Receiving systems	Systems that receive ecosystem services	City of Beijing
Spillover systems	Systems that affect or are affected by interactions between sending and receiving systems	Other areas affected by the PLDL (e.g., surrounding areas in Hebei and other areas that send water to Beijing)
Flows	Movement of ecosystem services and associated materials, energy, information, such as cash payments	Movement of water and cash between Heibei and Beijing; movement of materials/energy/information between Beijing (or Hebei) and spillover systems
Agents	Service providers in sending systems; beneficiaries in receiving systems; involved organizations or people in sending, receiving, and spillover systems	Participant households in Hebei; local governments in Hebei and Beijing; agents in spillover systems
Causes	Environmental (e.g., availability of ecosystem services in sending systems); Socioeconomic (e.g., demand for ecosystem services in receiving systems); Political (e.g., agreements between sending and receiving systems); technological (e.g., channels to transfer ecosystem services)	Decline in water quantity and quality in Beijing and Hebei; population growth and household proliferation in Beijing; rapid economic growth; increasing water demand in Beijing; conflicts and shared political interests between Hebei and Beijing; feasible technologies of transferring water; systems that affect hydrological dynamics in Beijing and Hebei
Effects	Socioeconomic and environmental effects in sending, receiving, and spillover systems; feedbacks	Increase in water yield and decrease in nutrient pollution in Miyun Reservoir Watershed; opportunity costs of conserving water to service providers; transaction costs; economic costs to Beijing residents; changes in livelihood of service providers; changes in livelihood of beneficiaries; environmental effects (e.g., on groundwater level, land cover) in Beijing; feedbacks such as changes in payments according to changes in water quantity and quality; socioeconomic and environmental effects on spillover systems

Underlined items refer to issues that are not studied by Zheng et al. (1).