Ecosystem service trade-offs and synergies under influence of climate and land cover change in an afforested semiarid basin, China

Due to increasing global changes, understanding the corresponding change in provisioning ecosystem services is becoming increasingly important. Climate and land use change have been identified as two major environmental change variables and will affect ecosystem services extensively. Nevertheless, the impact of these two factors on ecosystem services, especially their relative importance and combined effects, is still unclear. The objective of this study is to offer a comprehensive method to investigate water-related ecosystem services and how they are influenced by land use and climate change in the Luanhe River Basin (LRB), China. This will serve as a case study to reveal widely general principles in semiarid areas. The water-related ecosystem services between 1995 and 2015 were first quantified spatially by the InVEST model for four scenarios. Then, the effects of land use and climate change on the water-related ecosystem services were assessed by two indices, the relative importance index (RII) and combined effect index (CEI). The results show that the water-related ecosystem services in the LRB have been dramatically reduced. Specifically, the water yield, nitrogen and phosphorus purification decreased by 22.08%, 2.72% and 4.98%, respectively, from 1995 to 2015. Notably, climate change has a higher impact than land use change on water yield and soil export, while land use change has a greater impact than climate change on nutrient purification. In addition, changes in water yield and soil export were different between the three sub-watersheds in the LRB, which is likely due to the difference in land use types. Our results are potentially useful for land management practices in the context of environmental change to enhance ecosystems services and achieve sustainable goals in semiarid regions.