Effects of Future Climate and Cropland Use Changes on Rice Potential Yields in Hainan Island, China

Rapid climate and cropland use changes in recent decades have posed major challenges to food security in China. Hainan Island is the only tropical island in China and is blessed with natural conditions for crop production. This study first simulates the climate scenarios of Hainan Island for 2030, 2040 and 2050 under the four Socio-economic Pathways (SSPs) based on the climate models in ScenarioMIP of Coupled Model Intercomparison Project Phase 6 (CMIP6), and then simulates the land use scenarios of Hainan Island for 2030, 2040 and 2050 based on the Cellular Automata (CA)-Markov model. Finally, based on the Global Agro-Ecological Zones (GAEZ) model, the rice potential yield in Hainan Island for 2030, 2040 and 2050 are simulated, and the effects of future climate and cropland use changes on rice potential yields are investigated. The results show that: 1) from 2020 to 2050, mean maximum temperature first decreases and then increases, while mean minimum temperature increase sharply followed by a leveling off under the four SSPs. Precipitation decreases and then increases under other three SSPs except SSP2-4.5. Net solar radiation increases continuously under SSP1-2.6, 2-4.5, and 5-8.5, and has the lowest simulated values under SSP3-7.0. Mean wind speed increases continuously under SSP1-2.6, fluctuates more under SSP2-4.5 and SSP5-8.5, and increases slowly and then decreases sharply under SSP3-7.0. Relative humidity basically decreases continuously under the four SSPs. 2) Areas of paddy field are 302.49 thousand, 302.41 thousand and 302.71 thousand ha for 2030, 2040 and 2050, respectively, all less than that in 2020. Paddy field is mainly converted into built-up land and woodland. As for the conversion of other land types to paddy field, woodland is the main source. 3) Under the effects of future climate and cropland use changes, the mean potential productions in Hainan Island under the four SSPs increase 1.17 million, 1.13 million and 1.11 million t, respectively, and the mean potential yields increase 3873.21, 3766.71 and 3672.38 kg/ha, respectively for the three periods. The largest increases in mean rice potential production and mean potential yield are 1.21 million t and 4008.00 kg/ha, 1.16 million t and 3846.65 kg/ha, as well as 1.13 million t and 3732.75 kg/ha, respectively under SSP 3-7.0, indicating that SSP3-7.0 is the most suitable scenario for rice growth. This study could provide scientific basis for crop planting planning and agricultural policy adjustment.