An analysis of the water-energy-food-land requirements and CO2 emissions for food security of rice in Japan

The aim of this study is to assess the impact of rice-based food security on water, energy, land, and CO2 emissions from a holistic point of view using the Nexus approach, which analyzes tradeoffs between water, energy, and food management. In Japan, both rice consumption and the area harvested for rice have decreased. Maintaining a high self-sufficiency ratio (SSR) in rice production is an important aspect of food security in Japan, impacting the management of key resources, such as water, energy, and land. This study has, therefore, assessed the impact of various SSRs on rice production, focusing on consumption and land-use trends. First, the rice production SSR is predicted to drop to 87% by 2025 within the logarithmic trend of rice consumption and the polynomial trend line of the harvested area of rice. This reflects the fact that rice production is expected to decline more steeply than consumption between 2016 and 2025. Second, this study sets the SSRs for rice in 2025 between 80% and 100%, reflecting a range of low-to-high food security levels. In comparison with the 2016 baseline, about 0.70 ×106 additional tons of rice will be produced. Achieving a rice production SSR of 100% will require 10,195 ×106 m3 more of water and 23.31 ×106 GJ more of energy. Furthermore, an additional 283,000 tons of CO2 will be emitted in 2025, as more energy is used. By contrast, an 80% rice production SSR scenario would save 1482 ×106 m3 of water and 3.39 ×106 GJ of energy, as well as making a 398,000-ton reduction in CO2 emissions in 2015. A lower SSR would have a positive impact on resource management but a negative impact on food security. It would also reduce the income and economic status of farmers. It is, therefore, important to consider the tradeoffs between food security and resource savings in order to achieve sustainable water, energy, food, and land management in Japan. © 2018 by the authors.