While we often think of plastic pollution when we think of threats to our ocean, there are actually many other pollutants that impact our ocean’s health, including nitrogen pollution. Being mindful of the different sources of marine pollution enables us to navigate benefits and trade-offs when making policy decisions about pollution control, especially as substances like nitrogen, phosphorus, pathogens and pesticides often come from common sources.
Although nitrogen is a vital part of life, in its reactive form (Nr), it can be transported into freshwater, estuaries, and coastal waters. This can be transferred through different pathways, including soil, surface runoff, groundwater, sewage, and nitrogen fixation. In this way, the cycles of water and nitrogen are closely linked, with nitrogen pollution eventually making its way into the marine environment. Even nitrogen pollution in the air finds its way back into the water cycle as pollutants are trapped in rainwater and brought back down to land and waterways. Human activities, notably the overuse of fertilizer in agriculture, can also cause an excess of reactive nitrogen to end up in waterways in the form of runoff or through groundwater aquifers. Nitrogen pollution is considered by marine experts as ocean plastics pollution’s forgotten neighbour.
As outlined in the UNEP article: Four reasons why the world needs to limit nitrogen pollution (unep.org), the pathway of reactive nitrogen from land to sea can have detrimental consequences for the ocean.
“Once nitrogen reaches aquatic ecosystems, it can cause a rapid increase of toxic algae, known as algal blooms, which deplete oxygen in water and can create coastal dead zones affecting underwater life.”
The negative effects of algal blooms are a threat to local fishing and tourism, making nitrogen pollution a concern for health, food security, the environment, and the economy, as well as one of the biggest global drivers of human-made biodiversity loss.
The GEF/UNEP ‘Towards INMS’ (INMS) project is tackling the issue head on by bringing together scientists and policymakers to address the nitrogen challenge in an integrated way, which avoids issues such as ‘pollution swapping’, where a mitigation for one pollutant leads to the increase in another pollutant.
INMS supported the preparation of the first ever UNECE Guidance Document on Integrated Sustainable Nitrogen Management under the lead of the UNECE Task Force on Reactive Nitrogen. The document outlines best practices for policymakers, extension agencies and farmers on how to manage nitrogen in such a way that it mitigates both water and air pollution. Furthermore, INMS co-led a team of 40 international experts in the preparation of the ‘Our Phosphorus Future’ report, a comprehensive global analysis of the challenges and possible solutions to the phosphorus crisis. Similar to nitrogen, excessive quantities of phosphorus represent a significant source of aquatic pollution.
Moreover, INMS has provided a cross-cutting contribution to multiple policy programmes and intergovernmental conventions relevant for the nitrogen challenge. These include among others the Global Partnership on Nutrient Management (GPNM) and the Global Programme of Action for the Protection of the Marine Environment from Land-based Activities (GPA). INMS has been very active in identifying Nitrogen Champions and lending scientific support to ambitious regional and global nitrogen policies such as the Colombo Declaration and the two UNEA Resolutions on Sustainable Nitrogen Management (4/14;5/2).
INMS is currently working to complete and publish a series of Guidance Documents and the first International Nitrogen Assessment (INA) (set for publication by Cambridge University Press in 2024), which will provide a state-of-the-art scientific underpinning for future action on nitrogen. The INA will have a dedicated chapter on water which will quantify the current status of reactive nitrogen concentrations in waterways, while also identifying the sources of reactive nitrogen enrichment. The chapter uses models to make projections of future nitrogen pollution under different scenarios. The INMS Guidance Documents series will be published later this year and covers a wide array of topics ranging from ‘National Nitrogen Budgets’ and ‘Nitrogen Impact Assessment Methods’ to ‘Opportunities for nitrogen mitigation’.
On an international policy scale, there was the notable adoption of the landmark global agreement to safeguard biodiversity in December 2022: the Kunming-Montreal Global Biodiversity Framework. With its ‘Target 7’, this agreement includes the most ambitious global nitrogen target so far: a reduction of excess nutrients [incl.nitrogen] lost to the environment by at least half, including through more efficient nutrient cycling [incl.nitrogen] and use by 2030.
The culmination of these efforts promotes a better understanding of global and regional nitrogen flows, sources, sinks and solutions, as well as actions to reduce barriers to the improved management of nutrients.
------------------------
About the GEF/UNEP INMS Project
For more information on the GEF/UNEP INMS Project, please contact the Project Coordination Unit (inms@ceh.ac.uk), visit the project website, to find all existing INMS publications, and the project page on iwlearn.net.
To be updated about the publication dates of the Guidance Documents and the INA, feel free to sign up for the INMS newsletter and follow the INMS on Twitter.
© 2026 IW:LEARN
.jpeg?auto=webp)
.jpeg?auto=webp)
.jpeg?auto=webp)
.jpeg?auto=webp)
.jpeg?auto=webp)
.jpeg?auto=webp)
.jpeg?auto=webp)
/1x.jpeg?auto=webp)
/1x.jpeg?auto=webp)
/1x.jpeg?auto=webp)
/1x.jpeg?auto=webp)
/1x.jpeg?auto=webp)
/1x.jpeg?auto=webp)