In some areas of the world, nitrogen fertilizers and biological nitrogen fixation have made it possible to increase crop harvest and livestock production, while in other areas there is insufficient nitrogen to fertilize crops. In excess or deficit, the inefficient use of nitrogen is causing marine, freshwater, and air pollution, as well as altering the climate balance and reducing the ozone and biodiversity. This impacts human health, well-being and livelihoods.

Scientific efforts have begun to bring these issues together. However, there is still a high degree of fragmentation between research on the different benefits and threats of reactive nitrogen and between the respective policy frameworks, especially at the global scale.

The authors argue that a more joined-up approach to managing the global nitrogen cycle is needed to develop the ‘gravity of common cause’ between nitrogen issues and to avoid policy trade-offs. They describe how a coherent system for science evidence provision is being developed to support policy development through the ‘International Nitrogen Management System’ (INMS).

There is now a matching challenge to bring together the multiple policy agreements relevant for nitrogen, and the authors outline the concept for a policy coordination mechanism. This could make a major contribution to multiple Sustainable Development Goals by stimulating the next generation of international nitrogen strategies: maximizing the benefits of efficient nitrogen use, while minimizing its many environmental threats.