Spatial variation and influencing factors of the effectiveness of afforestation in China's Loess Plateau.

Payment for ecosystem services (PES) has become a widely accepted strategy for combining environmental conservation or restoration with socioeconomic development. Understanding the spatial heterogeneity of the effects of PES programs and their influencing factors is necessary for the design and implementation of effective programs. However, few researchers have both distinguished the effects of PES and analyzed their spatial variation simultaneously. Here, we analyzed the spatial differences in the effectiveness of afforestation under China's Grain-to-Green Program (GTGP), a well-known PES program, in the Loess Plateau. The approach is based on remote sensing data and county-level statistical data, which reflects the basic implementation unit of the GTGP. We identified several local and non-local influencing factors: the aridity index, rural non-farm employment, and rural migration improved afforestation effectiveness, whereas the total afforestation degree (the cumulative area of afforestation divided by the total area), vegetation conditions before afforestation, grain production, and investment in fixed assets decreased its effectiveness. Based on our results, we propose several suggestions for improvement: preferring afforestation in humid counties with low vegetation cover, identifying an optimal degree of afforestation, and promoting the transformation of rural livelihoods. Our study provides a general approach to analyze the effectiveness of PES and its spatial variation, thereby providing insights into future PES programs both within China and around the world.