The European Nitrogen Assessment

The European Nitrogen Assessment (ENA) is the first comprehensive synthesis of the effects of reactive nitrogen on European ecosystems, climate, and human health. It was coordinated by the Centre for Ecology & Hydrology (CEH) and published in 2011 by Cambridge University Press.

Key Findings

• Europe loses between €70 billion and €320 billion per year through the effects of reactive nitrogen on human health, ecosystem services, and climate.
• Agriculture is responsible for approximately 80% of reactive nitrogen emissions in Europe, primarily through ammonia (NH₃) and nitrous oxide (N₂O).
• Ammonia deposition exceeds critical loads across large areas of Europe, causing biodiversity loss in sensitive ecosystems.
• The nitrogen use efficiency of European agriculture averages approximately 18%, meaning most applied nitrogen is lost to the environment.

Scope

The assessment covers 200 European scientists and synthesises data from more than 3,000 scientific papers across five key threats: water quality, air quality, greenhouse gases, ecosystems, and human health.

Policy Relevance

The ENA directly informed the revision of the EU National Emission Ceilings Directive (2016/2284/EU) and the UNECE Gothenburg Protocol amendments (2012), both of which include specific ammonia emission reduction targets.