A global analysis of agricultural productivity and water resource consumption changes over cropland expansion regions

Cropland expansion often occurs on grasslands and partial forests. However, there is little quantified understanding of how cropland expansion affected the agricultural productivity and water resource consumption globally. In this study, we used spatially explicit satellite-based data, including land use maps, net primary productivity and evapotranspiration from 2001 to 2018, and the space-for-time substitution technique to investigate the relationships between cropland expansion and agricultural productivity and water resource consumption. Results showed that global cropland area presented a significant net increasing trend with 1.9 × 104 km2/a (p < 0.01) since 2000. Net increased cropland area over the Northern Hemisphere and the Southern Hemisphere occupied 27.1% and 72.9% of global total net increase, respectively. Large-area cropland expansion mainly focused on Eastern Asia, Southern Asia, Eastern Europe, Southern America, and Northern America. Particularly, cropland expansion in the Southern America deserved the greatest attention. At the global scale, new expanded croplands caused average NPP decrease and average ET decrease compared to original ecosystems, but performances were evident differences in subregions. Cropland expansion in the Southern America evidently decreased NPP and ET compared to other places. In contrast, new expanded croplands in most subregions of Asia and Northern America performed higher the agriculture productivity, while the increases were done at the expense of more water resource consumption. Although cropland expansion only slightly decreased NPP compared to original ecosystems globally, new expanded croplands often occurred in water-limited or temperature-limited areas according to precipitation and temperature gradations. This study suggests that cropland expansion should more consider sustainable land use and development, and reduce the risks of cropland expansion on natural ecosystems as much as possible.