Assessment and Enhancement of Ecosystem Service Supply Efficiency Based on Production Possibility Frontier: A Case Study of the Loess Plateau in Northern Shaanxi

Enhancing the supply efficiency of ecosystem services plays a central role in improving both natural ecosystems and human well-being. Taking the Loess Plateau of Northern Shaanxi as an example, this study utilizes InVEST to assess the ecosystem services of water yield and habitat quality. The optimal solutions for the combination of these two services are calculated on the basis of the Pareto principle. The production possibility frontier curves for the two services are fitted, and the services’ supply efficiency is measured. Furthermore, this study employs ordinary least squares and geographically weighted regression to analyze the dominant factors affecting supply efficiency. The results comprise the following findings: (1) There are eighteen solutions representing the optimal combinations between the two services. (2) The supply efficiency of the two services increases from northwest to southeast in spatial distribution. (3) The dominant factors vary among different zones of supply efficiency. Population, hydrology, and gross domestic product (GDP) are the dominant factors in the general-efficiency, sub-low-efficiency, and low-efficiency supply zones, respectively. Hydrology, NDVI, and GDP are the dominant factors in the sub-high-efficiency supply zone, while GDP, terrain, and population are the dominant factors in the high-efficiency supply zone. In conclusion, this paper proposes recommendations for reducing trade-offs and enhancing supply efficiency between ecosystem services. These include dynamic supervising for the high-efficiency supply zone, moderate greening in the sub-high-efficiency supply zone, stabilizing the population in the general-efficiency supply zone, and reducing development intensity in low- and sub-low-efficiency zones. The study reveals the potential and approaches for improving the supply of ecosystem services and offers guidance for formulating ecological protection plans.