Optimal options of ecological restoration patterns in semi-arid regions: Lessons learned from two-decade ecological restoration projects in Bashang Plateau of China

In responding to global ecosystem conservation and sustainable social development, numerous ecological restoration projects have been performed in ecologically vulnerable areas around the world, especially in semi-arid areas. Affected by local hydrothermal conditions, whether ecological restoration projects can achieve goals of balanced water-carbon enhancement as well as sustainable development in semi-arid areas is controversial. It is uncertain that to what extent the land use change caused by ecological restoration projects will affect the water-carbon imbalance. This research takes the Bashang Plateau Protection Zone (BPZ), a typical semi-arid area in Hebei Province of China, as a porotype to discover the spatial water-carbon changes and their contributing factors under ecological projects during 2000 to 2020 through root mean square deviation and random forest analysis. Results show: (1) In the past two decades, carbon sequestration in BPZ continued to improve while water conservation decreased significantly. The water-carbon imbalance regions in BPZ increased nearly 6.80 folds, from 338.60 km2 to 2642.38 km2. (2) Precipitation and temperature exerted the most significant impact on the formation of water-carbon imbalance regions, whereas the contribution of land use change could reach 40%, demonstrating that human activities were also strongly responsible for water-carbon imbalance. (3) Ecological restoration pattern of limiting afforestation and agricultural land expansion with priority restoration of grassland is beneficial to achieving water-carbon balance and sustainable goals of ecological restoration in semi-arid regions.