Foreword

Nitrogen is one of the most important elements for life on earth. It is a key ingredient in DNA and RNA, photosynthesis and amino acids – the building blocks of proteins. Nitrogen is essential for the growth of plants and crops on which humans and livestock depend. Approximately half of the world’s population rely on nitrogen fertilisers for their food consumption, making nitrogen fundamental to global food security.

Humankind has doubled the inputs of chemically-reactive forms of nitrogen to the environment since the early 20th Century. The use of nitrogen-containing fertiliser and cultivation of nitrogen-fixing crops has expanded rapidly in order to feed the planet’s growing population. Nitrogen also has many industrial uses, and the combustion of fossil fuels releases nitrogen to the atmosphere.

While too little nitrogen input constrains agricultural and industrial productivity, the excessive use of nitrogen has far-reaching and complex – but often overlooked – effects. It poses a risk to human health and the environment, and threatens to undermine efforts to achieve biodiversity, climate and other Sustainable Development Goals. Once introduced into the environment, nitrogen easily changes chemical form and moves between air, soil, water and ecosystems, causing a cascade of damages. We do not yet fully understand the resilience of ecosystems to excess nitrogen, or the effects of nitrogen loading on different ecosystem services. This underscores the need for stricter monitoring and management.

This report, Human Acceleration of the Nitrogen Cycle: Managing Risks and Uncertainty – produced by the OECD in collaboration with the UNECE Task Force on Reactive Nitrogen (TFRN) – proposes a policy framework to address the environmental and public health challenges of nitrogen. It advocates a three-pronged approach to manage the known risks related to nitrogen and the uncertainties associated with excess nitrogen in the environment. This entails: (i) analysing nitrogen pathways to better manage environmental risks; (ii) addressing nitrous oxide emissions in climate change mitigation policies; and (iii) monitoring and managing residual nitrogen by measuring the effect of the above measures on the national nitrogen budget. The report provides guidance on how to implement this three-pronged approach, while addressing the need for coherence across sectoral and environmental policies.

I am proud that the OECD is working closely with the scientific community to help inform policymakers, governments, business and civil society of the importance of managing human impacts on the nitrogen cycle and promoting better nitrogen policies for better lives.

Angel Gurria

Secretary General

OECD