Loss of nitrogen to the environment causes a plethora of pollution problems.  In addition to contributing to air pollution and climate change, it has a massive impact on ecosystems.

One of the big challenges for nitrogen is summed up by the slogan ‘Everywhere and Invisible’. Nitrogen losses are hard to see, whether we are talking about ‘diffuse pollution’ from agriculture, wastewater or nitrogen oxides emissions from burning fossil fuels.

When it comes to restoring ecosystems, this means that it is all too easy to forget about nitrogen. Yet we do so at our peril!

Take for example, some of our most vulnerable ecosystems, natural peatlands. Many such systems are naturally ‘oligotrophic’, which means that they are adapted to very few nutrients. With too much nitrogen pollution from the atmosphere, or too many nutrients from water run-off (including both nitrogen and phosphorus), then these precious ecosystems will suffer. Biodiversity is lost as nitrogen-loving species outcompete the natural flora, while reducing their ability to store carbon in the ground.

My thinking about these questions has benefited greatly by working with the Northern Ireland Environment Agency to manage the threat of ammonia pollution. Ammonia is a form of nitrogen that is lost to the atmosphere from livestock manures and nitrogen fertilizers. With high ammonia emissions from this agricultural landscape, the native peatlands – critical for Ireland’s biodiversity – are under serious threat, with key plant species being lost and carbon storage threatened. The problem is that such peatlands are under many threats, and nitrogen is just one of them.

This means that there is a whole parallel universe of scientists and land managers discussing ecosystem restoration for Ireland’s peatlands. How to reduce large-scale peat harvesting? How to manage water levels to encourage recovery of peatland growth? Such approaches are all a key part of nature-based solutions that we urgently need.

Dead or alive? With high levels of nitrogen pollution, restoration of Northern Ireland’s peatlands is being compromised. Here, Mark Sutton holds some healthy sphagnum moss (green-yellow-red colour) and some dead sphagnum (dark brown), which has been killed by ammonia, a form of nitrogen air pollution (Photo © Mark Sutton and Netty van Dijk, UKCEH).

But if we forget the nitrogen in this, we risk not meeting our goals. Invisibly, the ammonia is lost from livestock farms and farmers’ fields. It blows through the air and then lands on the peat bogs. It means that, even if peat-cutting is avoided, and even if water management is ideal, then these peat­lands will be under threat. If we are truly to protect these wonderful wildlife havens, then we will have to reduce ammonia nitrogen emissions and find inventive ways to plan our landscapes better.

The good news is that ammonia is also a valuable commodity because it represents a loss of fertilizer value. In effect, every kg of emission to the air represents around one US$1 worth of fertilizer value lost from the farm. It means we need better awareness of why sustainable nitrogen management is in everyone’s interest. The farmer needs to keep nitrogen on the farm for the best harvest. At the same time, this helps to leave the peatlands in a clean condition, allowing nature to flourish.

While there are many measures available for reducing nitrogen losses from agriculture (see new UN guidance), this connection with ecosystem restoration is too often forgotten. The bottom line is that we need good habitat management AND good nutrient management, if we are going to achieve success.

It is a story that needs to be told round the world.  The “Nitrogen Crisis” in the Netherlands is at heart an issue were excess nitrogen emissions are preventing ecosystem recovery. In the Baltic Sea, Gulf of Mexico, and Manila Bay, excess nitrogen in run-off is creating algal blooms, increasing the risk of dead-zones. Whether on land or sea, in Africa or Asia, ecosystem restoration and sustainable nitrogen management need to go hand in hand.

This is why we are not only working on the decade of ecosystem restoration. In a new nitrogen special issue of One Earth [launch Jan 21, 2021], with INMS colleagues, we have called for the years up to 2030 also to be recognized as the ‘Nitrogen Decade’. Building on the UNEA Nitrogen Resolution (UNEP/EA.4/Res.14) and the Colombo Declaration, if we want to reach the Sustainable Development Goals, we will have to manage these issues together.

Mark Sutton

Director, GEF/UNEP project “Towards the International Nitrogen Management System” (INMS).

UK Centre for Ecology & Hydrology, Edinburgh.

Key issues for Nitrogen & Ecosystem Restoration

• Simply to recognize that sustainable nitrogen management and ecosystem restoration must go hand in hand.
• Nitrogen emissions as a barrier to ecosystem restoration include both nitrogen oxides (NOx) and ammonia (NH3), from fossil fuel burning and agricultural activities.
• Effects of NH3 on vulnerable ecosystems may be even worse than from NOx, because of the ‘Alkaline Air’ effect of ammonia – damaging sensitive biodiversity like lichens and mosses.
• The air pollution effects of nitrogen on ecosystems have been hardly studied in many parts of the world, pointing to an under-recognized problem. These issues are now being explored for the first time under the GCRF South Asian Nitrogen Hub, as a contribution to INMS.
• Restoring aquatic systems is critically dependent on reducing levels of both nitrogen and phosphorus pollution. Massive changes in farming practices and wastewater management will be needed if ecosystems are to get a chance to recover.
• UNEPs work on sustainable nitrogen management is embracing the goal of the Colombo Declaration to halve nitrogen waste from all sources as part of national action plans by 2030 – offering a global saving worth $100 billion per year.
• The International Nitrogen Management System (INMS) is a global science-support system for international nitrogen policy development established as a joint activity of UNEP and the International Nitrogen Initiative. It is supported with funding through the Global Environment Facility (GEF) and around 80 project partners through the “Towards INMS” project (2016-2022). INMS provides a cross-cutting contribution to multiple programmes and intergovernmental conventions relevant for the nitrogen challenge.
• Through INMS and the Global Partnership on Nutrient Management (GPNM), UNEP is cooperating with the UN Convention on Biological Diversity, following up the Aichi Targets and the upcoming 2030 targets of the post 2020 biodiversity framework (for adoption by CBD COP15 in Kunming), working to extend the Colombo Declaration goal to all forms of nutrient pollution.