Tradeoffs between agricultural production and ecosystem services: A case study in Zhangye, Northwest China

Humans have increasingly intervened in the nature to advance socioeconomic development at the expense of ecosystem services. Tradeoffs between ecosystem services and socioeconomic development are inevitable and should be considered in sustainable ecosystem management. This is no exception in Zhangye where intensive agricultural activities have significantly affected its ecological conditions. Thus, this study evaluated the tradeoffs between agricultural production and key ecosystem services along with their spatial distributions at the watershed level in Zhangye based on multisource observation data. The key ecosystem services, including net primary productivity (NPP), water yield, and soil conservation, were evaluated for the years 2000, 2010, and 2015 using remote sensing data and the InVEST model. The Morishima elasticity of substitution (MES) between these ecosystem services and agricultural production were then estimated by applying a quadratic directional output distance function, and mapped to determine the tradeoffs. The results showed that the average NPP and annual water yield respectively increased by 22% and 24%, while annual soil conservation decreased by 22% during 2000-2015. The average MES values for agricultural production with NPP, water yield, and soil conservation were 0.14, -0.69, and -0.56, respectively. This indicated the existence of a synergetic relationship between agricultural production and NPP as well as tradeoff relationships between agricultural production and water yield/soil conservation. Differences in the spatial patterns of the relationships between agricultural production and these ecosystem services were observed. Significant tradeoff relationships were observed for agricultural production with water yield and soil conservation in the upper reach of Zhangye. It indicated that increasing agricultural production would be at the cost of decreased water yield and soil conservation, especially in the upper reach area. The quantification and spatial pattern determinations of tradeoffs between ecosystem services and agricultural production is useful for the development of regional ecological conservation policy and sustainable ecosystem management.