Effect of Climate Change on Rice Cultivation in South Korea – Runoff, Nitrogen Discharge, and Productivity Forecast Under Cmip6 Climate Scenarios Using the Apex-Paddy Model

Rice is a global staple crop, hence a forecast of production and implications on the environment in the face of climate change is needed. In this study, climate projections from 16 General Circulation Models (GCMs) in Coupled Model Intercomparison Project phase 6 (CMIP6) were statistically downscaled and implemented as inputs to the APEX-Paddy model for simulation. Runoff, nitrogen (N) discharge, and rice yield were forecasted for the Near-future (2011–2040), Mid-future (2041–2070), and Far-future (2071–2100) under two Shared Socioeconomic Pathways (SSPs) (SSP2-4.5 and SSP5-8.5) at rice paddy plains in Gimje district of South Korea. Generally, the SSPs in CMIP6 projected worse climatic conditions than earlier similar projections from the Representative Concentration Pathways (RCPs). Compared to historical (1981-2010) period, the results projected that daily temperatures, especially night (minimum) temperatures, would increase by 1.5–3.8 o C and 1.6–6.4 o C across all the future periods under SSP2-4.5 and SSP5-8.5 scenarios, respectively. Future increase in precipitation and decrease in N use effeciency would cause N discharge of 7.2–19.8 and 12.0–35.3% under SSP2-4.5 and SSP5-8.5, respectively. Transpiration would reduce by 7–14% and 8–19% for SSP2-4.5 and SSP5-8.5 scenarios, respectively, by the close of the 21 st Century. As a result of the elevated temperature rice growth and development period would shorten, accounting for a reduction in rice yield of about 10–13% and 10–27% under SSP2-4.5 and SSP5-8.5, respectively. Adjusting the period of cultivation and breeding improvement for tolerance to elevated temperature would be vital for sustainable rice production and food security.