Effects of climate change on suitable rice cropping areas, cropping systems and crop water requirements in southern China

Rice is one of the main crops grown in southern China. Global climate change has significantly altered the local water availability and temperature regime for rice production. In this study, we explored the influence of climate change on suitable rice cropping areas, rice cropping systems and crop water requirements (CWRs) during the growing season for historical (from 1951 to 2010) and future (from 2011 to 2100) time periods. The results indicated that the land areas suitable for rice cropping systems shifted northward and westward from 1951 to 2100 but with different amplitudes. The land areas suitable for single rice-cropping systems (SRCS) and early double rice-cropping systems (EDRCS) decreased, whereas the land areas suitable for middle double rice-cropping systems (MDRCS) and late double rice-cropping systems (LDRCS) expanded significantly. Among the rice-cropping systems, the planting area suitable for SRCS was the largest during the historical period (1951–1980), whereas the suitable planting area for LDRCS was the largest during the future period (2070–2100). Spatially, the water requirement of rice during the growing season exhibited a decreasing trend from southeast to northwest from 1951 to 2010. Temporally, the regional water requirement of rice during the growing season decreased from 720 mm (1951–1980) to 700 mm (1981–2010) as a result of solar radiation and evapotranspiration. However, the water requirement was predicted to increase from 1027 mm (2011–2040) to 1150 mm (2071–2100). During the past six decades, the planting area suitable for double rice-cropping systems increased by 2.7 × 104 km2 and, consequently, the CWR and irrigation water requirement (IWR) increased by 1.1 × 1010 and 8.8 × 109 m3, respectively. In addition, under A1B scenarios, the CWR and IWR of double rice-cropping systems are expected to increase by 1.6 × 1011 and 1.2 × 1011 m3, respectively, from 2071–2100 compared with the historical period of 1951–1980. The regional CWR and IWR were predicted to increase respectively by 8% and 6% from 2011 to 2040, by 17% and 19% from 2041 to 2070, and by 20% and 24% from 2071 to 2100 compared with 1951–1980. These increases can be attributed to climate warming, which expands the suitable planting area for multiple-cropping systems and extends the growing season for late-maturing rice varieties. Our study aims to provide a scientific guide for planning future cropping systems and optimizing water management in the southern rice cropping region of China.