Prediction of the environmental effects of excess nitrogen caused by increasing food demand with rapid economic growth in eastern Asian countries, 1961–2020

Using a nitrogen balance model based on statistical data, nitrogen loads due to food production and consumption and energy production were estimated for each 0.5° × 0.5° grid cell in the 13 countries of eastern Asia from 1961 to 2002. Groundwater quality was estimated with a simple first-order reaction model. Total nitrogen load, including natural nitrogen fixation, increased by a factor of 3.8 between 1961 and 2002 (with an increase by a factor of 15.6 due to crop production, 14.1 due to livestock waste, 2.4 due to human waste, and 4.5 due to energy production). The present estimate of average nitrogen load is 3.9 t km−2 yr−1. Our model indicated high nitrogen concentrations in groundwater in eastern and northeastern China and some areas of Republic of Korea and Japan. In many countries, per capita food consumption and the common logarithm of per capita NOx emission show significant linear relationships with the common logarithm of per capita GDP. Based on these relationships, we predicted food demands, fertilizer demand, NOx emission, and the resulting nitrogen loads for the next 18 years. Our model predicts that in 2020, the total nitrogen load will be 1.3–1.6 times the present load across the entire region according to several scenarios on economic growth and population increase, with various patterns of change in the different countries.