Impact Of Diet Changes On Nitrogen Flows In The Food Chain And Optimization Strategies In China

The change of dietary structure is an important driving factor of China’s food production,and it will also affect the nitrogen nutrient flows and its resource and environmental costs of the food chain in China.In this study,from the perspective of changes in dietary structure,we established an index system for the comprehensive evaluation of nitrogen in the food chain in China.Using the NUFER(Nutrient flows in Food chains,Environment and Resources use)model and the N-Calculator model,this study analyzed the historical changes in the nitrogen footprint of the food chain in China.Through the establishment of the food trade matrix among different provinces in China,the spatial variation characteristics of the nitrogen footprint of the food chain in China are quantified.Finally,the future food chain nitrogen management optimization strategies based on dietary structure changes are proposed through scenario analysis.The main results of this study are as follows:1.Between 1978 and 2012,the per capita food consumption of our country’s residents showed a downward trend,which was mainly due to the continuous decrease in per capita cereals and vegetable consumption.The per capita energy intake of residents in China showed a declining trend,per capita protein intake remained basically stable,and per capita fat intake rose rapidly.The proportion of animal-derived food in China’s residents’ nutrient intake has been rising.From 1960s to 2000s,total N input to China’s food chain increased from 5.5 MT N/yr to 44.9 MT N/yr.Nitrogen use efficiency in the process of plant-derived food production continues to decline,and nitrogen use efficiency in animal-derived food production continues to increase.The nitrogen losses during the food chain production in China increased from 3.0 MT N/yr to 27.2 MT N/yr.2.Between 1960s and 2000s,the per capita food nitrogen footprint increased from 4.7 kg N/capita/yr to 21.3 kg N/capita/yr,an increase of 3.5 times,and the proportion of animal-derived food to total food nitrogen footprint in China increase from 37%to 54%.The per capita food nitrogen footprint of China is lower than that of the United Kingdom,the United States,Japan,and Australia,closer to the Netherlands and higher than Germany,Austria,and Tanzania.China’s food virtual nitrogen factor(referring to the amount of nitrogen released to the environment from food production to consumption per unit unit of food nitrogen consumed)is generally higher than other countries.Excessive chemical fertilizer input and poor animal manure management are the main reasons leading to lower nitrogen use efficiency in crop and animal production to consumption.3.In 2015,total inter-provincial food trade in China was 527 MT/yr,accounting for 28%of China’s total food production.The main export areas of China’s food are Northeast China,North China,Central China,and Northwest China.The main input areas are South China,Southwest China,and East China.The food virtual nitrogen factor in China’s food-exporting provincesis generally lower than that of food-importing provinces.The food nitrogen footprints of different provinces in China are quite different.The per capita food nitrogen footprint in Chongqing is the highest,which is 27.7 kg N/capita/yr,the per capita food nitrogen footprint in Tibet is the lowest,which is 12.3 kg N/capita/yr.4.Based on the per capita food consumption recommendation in the Chinese Residents’ Dietary Guidelines(Version 2016),compared with the BAU scenario(keeping the existing development trends unchanged),the future China’s food chain nitrogen input,nitrogen losses and food nitrogen footprint will increase substantially,increasing by more than 20%and 50%respectively in 2030 and 2050.Optimizing China’s future food production to improve nitrogen use efficiency and nitrogen recycle efficiency in different stages of China’s food chain can effectively reduce the nitrogen input,nitrogen losses,and food nitrogen footprint in China’s food chain,with reductions of more than 20%,38%and 40%,respectively.In addition,an appropriate increase in the proportion of food imports is also an effective way to mitigate food production pressure and reduce the environmental impact of nitrogen.