Trends in the food nitrogen and phosphorus footprints for Asia's giants: China, India, and Japan

Substantial losses of nitrogen (N) and phosphorus (P) to the environment occur during food production. These emissions of reactive N (Nr) and P have adverse effects on the environment. The life cycle emissions of Nr and P due to resource consumption can be quantified using N and P footprints. In this study, a common framework developed for the purpose of making comparisons was used to examine the food N and P footprints of China, India, and Japan from 1961 to 2013. The footprints increased significantly in China after 1976 (5.4–19.3 kg-N capita⁻¹ yr⁻¹ and 1.20–4.77 kg-P capita⁻¹ yr⁻¹ in 1976–2013) with the higher consumption of meat and vegetables. In India, an increase in milk and vegetable consumption resulted in a gradual increase in the footprints since 1976 (8.5–11.4 kg-N capita⁻¹ yr⁻¹, 0.99–1.6 kg-P capita⁻¹ yr⁻¹ in 1976–2013). In Japan, the footprints increased until 1993 (12.2–28.3 kg-N capita⁻¹ yr⁻¹, 2.59–8.43 kg-P capita⁻¹ yr⁻¹ in 1961–1993) before declining (21.8 kg-N capita⁻¹ yr⁻¹, 6.05 kg-P capita⁻¹ yr⁻¹ in 2013), with a constant increase in meat consumption, a decrease in cereals, and improvements in nutrient use efficiency. The N footprint tends to be more sensitive to the consumption of meat, milk, oil crops, fish, and seafood, and the P footprint tends to be more sensitive to vegetables. By analysing the Asian giants, the key food items to target to reduce the footprints are identified. If the per-capita average footprints in high and middle income countries were the same as that in Japan in 1993, the global food N and P footprints would increase by factors of 1.18–1.89 by 2030. The use of these results with other advances in agriculture practices has the potential to improve nutrient use efficiency and to promote more efficiently-produced food.