Applying production-possibility frontier based ecosystem services trade-off to identify optimal scenarios of Grain-for-Green Program

The trade-off between grain production service (GP) and water purification service (WP) is widely acknowledged. Grain-for-Green Program (GFGP) is an effective way to alleviate ecosystem services (ESs) trade-offs and to achieve sustainable management of grain supply and water protection. However, how to identify the optimal GFGP scenario is worth further investigation. This study developed an index system for measuring ESs trade-offs, including the first-order derivative, synergy potential, and trade-off intensity based on the production-possibility frontier (PPF). Six GFGP scenarios were constructed and the non-linear trade-off between GP and WP under each scenario was evaluated. The results showed that in 2018 and six GFGP scenarios, the PPFs of the two ESs in the Dongting Lake Basin in Hunan Province showed a combination of convex-concave trade-offs. The synergy potential of GP and WP under the six scenarios increased by 2.52%~12.88%, while the trade-off intensity decreased by 6.54%~47.37% respectively, compared with the baseline of 2018. The Water Purification Priority Scenario of high-intensity was identified to be the optimal scenario with the highest synergy potential and lowest trade-off intensity, indicating that converting cropland with high nitrogen output into forest land under the condition of strict preservation of cropland could minimize the trade-off between GP and WP. This study proposed a PPF approach to identifying the optimal implementation of GFGP with the aim to realize collaborative guarantee of grain supply and water protection.