Cropland compensation in mountainous areas in China aggravates non-grain production: evidence from Fujian Province

The large-scale non-grain production (NGP) on cropland poses a potential threat to national food security, which has attracted the attention of the Chinese government. As a hotspot of NGP, mountainous cropland has undergone dramatic changes in its distribution pattern, influenced by China's cropland requisition-compensation balance system. Consequently, the NGP on compensated cropland (CCL) has become an unstable factor in grain production in mountainous areas. This paper analyzes the distribution pattern of CCL in Fujian Province, a typical mountainous area in China, identifies and compares the NGP characteristics between original cropland (OCL) and CCL, and explores its driving mechanism based on the physico-geographical environment, the socio-locational environment, and the resource endowment attributes, using the boosted regression trees (BRT) model. Results show that from 2009 to 2019, CCL tended to shift towards higher elevation and steeper terrain in the vertical zone and towards inland agricultural districts and counties in the western and northern horizontal zones. The NGP rate of CCL reached 16%, about twice that of OCL, and the proportion of instable cropland was also higher. Travel distance to adjacent cropland and slope were the main driving factors for NGP of CCL, followed by patch area, agricultural population density, and suitability of machine tillage. These factors exhibited differentiated marginal effects in their different threshold intervals and did not follow a simple one-way action mechanism. Furthermore, the analysis of pairwise interaction effects between variables identified the four most powerful combinations, which were slope-elevation, travel distance to adjacent cropland-elevation, slope-travel distance to adjacent residential area, and travel distance to adjacent cropland–aspect; within their specific value ranges, NGP is highly likely. Finally, we optimized the current evaluation system for reserved cropland resources based on these value ranges and selected Jianyang County, Dehua County, Zhao'an County, across the Fujian Province, as the area to adjust the reclamation strategy of future reserved cropland resources.