Modeling the Impact of Global Warming on Rice Yield in Japan

Abstract

The effects of global warming can lead to decreased crop yields on a global scale. However, the extent to which crop yields decline due to the warming may vary among different geographical areas depending on the climatic factors and types of cultivation, fertilization, and soil. In this study, a crop yield-nutrient model was developed to estimate nutrient levels and quantify the contributions of climatic factors in crop yield improvements. The model was used to predict rice yields (given total nutrient levels) as well as the decline in yields in response to increased temperatures, using the estimated baseline nutrient level required for plant growth and the estimated effects of temperature among different prefectures in Japan. Results showed that the predicted temperature increase from 2015 to 2030 could cause a decline in rice yield in the range of 53-194 g m^(-2). The largest percentage decline in the rice yield was predicted for Okinawa prefecture; however, Okayama was the prefecture that had suffered the most serious effects of global warming in Japan during the past 50 years (according to the estimated effects of temperature). It showed that the contributions of rainfall and radiation to plant growth varied geographically (although the difference was small among prefectures). The spatial divergence in nutrient intake levels in crops can be demonstrated with a simple mathematical model.