Up to the mountains and down to the wetlands: Thirty years' migration of cropland in China since 1990.

Cropland changes are crucial aspects of land-use/land-cover changes (LUCC), which profoundly influence agricultural sustainability and terrestrial ecosystem health. In the context of dynamic shifts within the natural environment, coupled with the evolution of agricultural practices and the transformation of agrarian systems and policies, the trajectory of farmland alteration has exhibited significant divergence across various nations and regions. This article delves into the intriguing phenomenon of China's cropland migrating up to mountains and down to wetlands and analyses its spatiotemporal pattern evolution from 1990 to 2020. Then the study identified the driving forces behind this migration from diverse perspectives encompassing natural factors, socioeconomic factors, cropland conditions, and landscape patterns. A fixed-effect panel analysis is employed to quantify the impacts of this phenomenon on food security and ecological environment quality. The findings reveal that over the past three decades, croplands moving to mountains and wetlands have been conspicuous across the country, with a considerable area of 187,862.9 square kilometres, representing a substantial 37.15% of the newly developed arable land. In the temporal pattern, it's exhibiting a clear three-stage characteristic of "prosperity-decline-recovery". Geographically, the northeast (NER) and northwest (NWR) agricultural regions have witnessed the largest cumulative areas of cropland moving to mountains and wetlands. These cropland changes are influenced not only by natural factors and the endowment of cropland but also by economic and financial factors. Furthermore, whether cropland moves up to the mountains or down to the wetlands exerts a significantly negative effect on ecological security and food security. This study aims to provide policy implications for regional cropland protection and agricultural sustainable development.