Reconciling regional nitrogen boundaries with global food security

While nitrogen inputs are crucial to agricultural production, excess nitrogen contributes to serious ecosystem damage and water pollution. Here, we investigate this trade-off using an integrated modelling framework. We quantify how different nitrogen mitigation options contribute to reconciling food security and compliance with regional nitrogen surplus boundaries. We find that even when respecting regional nitrogen surplus boundaries, hunger could be substantially alleviated with 590 million fewer people at risk of hunger from 2010 to 2050, if all nitrogen mitigation options were mobilized simultaneously. Our scenario experiments indicate that when introducing regional N targets, supply-side measures such as the nitrogen use efficiency improvement are more important than demand-side efforts for food security. International trade plays a key role in sustaining global food security under nitrogen boundary constraints if only a limited set of mitigation options is deployed. Policies that respect regional nitrogen surplus boundaries would yield a substantial reduction in non-CO2 GHG emissions of 2.3 GtCO(2)e yr(-1) in 2050, which indicates a necessity for policy coordination. Increasing nitrogen use efficiency is the most effective strategy to reduce undernourishment while respecting the nitrogen boundaries in regions such as China and India. This supply-side effort plays a more important role in alleviating food insecurity than demand-side efforts such as diet shifts and reduced waste when introducing regional nitrogen targets.