Reducing human nitrogen use for food production.

Reactive nitrogen (N) is created in order to sustain food production, but only a small fraction of this N ends up being consumed as food, the rest being lost to the environment. We calculated that the total N input (TN) of global food production was 171 Tg N yr(-1) in 2000. The production of animal products accounted for over 50% of the TN, against 17% for global calories production. Under current TN per unit of food production and assuming no change in agricultural practices and waste-to-food ratios, we estimate that an additional TN of 100 Tg N yr(-1) will be needed by 2030 for a baseline scenario that would meet hunger alleviation targets for over 9 billion people. Increased animal production will have the largest impact on increasing TN, which calls for new food production systems with better N-recycling, such as cooperation between crop and livestock producing farms. Increased N-use efficiency, healthier diet and decreased food waste could mitigate this increase and even reduce TN in 2030 by 8% relative to the 2000 level. Achieving a worldwide reduction of TN is a major challenge that requires sustained actions to improve nitrogen management practices and reduce nitrogen losses into the environment.