Projected unseasonable and shorter actual growth period for paddy rice and more pollutant loads into water bodies in a changing climate

Climate change has altered ecohydroclimatological variables and the phenology of crops and thus has threatened the ecosystem and food security. This study aims to quantify the impacts of climate change on the length and timing of growing seasons, crop yields, and nitrogen transport from paddy fields. A calibrated APEX-Paddy model was used to simulate the paddy rice fields in Gimje district of South Korea. A combination of sixteen general circulation models (GCMs) with two greenhouse gas emission scenarios (Shared Socioeconomic Pathways, SSPs) were used in order to evaluate the uncertainty of the impacts. The results indicated that shortened and unsea-sonable growing seasons are expected based on simulated leaf area index and biomass, accounting for a reduction in rice yields of about 10-13% and 10-27% under SSP2-4.5 and SSP5-8.5, respectively. This shorter growing season, in addition to projected higher precipitation and less efficient application of nitrogen, causes an increase of 7.2-19.8% and 12.0-35.3% in nitrogen loss under SSP2-4.5 and SSP5-8.5, respectively. The findings demonstrated that the projected shortened and unseasonable crop growing season caused by climate change is a threat to global food security and the ecosystem due to the excessive pollutants loads into the environment.