Reconstruction of cropland cover in topographically complex areas: The case of Sichuan Province, China, from 1671 to 2019

Abstract

Accurately reconstructing cropland cover in topographically complex areas has long been challenging for historical anthropogenic land cover change (ALCC) datasets. Sichuan Province, one of the most topographically complex areas in China, was chosen as a case study. This study integrated historical gazetteers and modern cropland statistics and survey data to examine and correct the prefecture-level cropland area of Sichuan Province. Subsequently, a novel cropland reconstruction model was proposed based on the order of cropland reclamation. Using this model, cropland changes in Sichuan Province from 1671 to 2019 were reconstructed with a spatial resolution of 5′ × 5′. The main findings were as follows: (1) The cropland reconstruction model designed in this study can well reproduce with the cropland cover in Sichuan Province. Compared with the prevailing ALCC datasets, our reconstructions were more consistent with descriptions of cropland changes in Sichuan Province in the literature. (2) The cropland cover in Sichuan Province expanded from northeastern and southern Sichuan to the Chengdu Plain and the hills north of the Yangtze River and then to the mountainous areas in the center and periphery of the basin from 1671 to 1985, after which it shrank in mountainous and urban areas. (3) The changes in cropland cover in Sichuan Province over the past 350 years were shaped by multiple factors such as war, famine, migration, agricultural policies and urbanization. The reconstructions in this study captured the spatial differences in cropland distribution in Sichuan Province, but their accuracy was limited by the cropland estimation method and the satellite-based cropland data used in the reconstruction model.