Clean Air Day: nitrogen pollution from agriculture has been overlooked for far too long

This post is by Jenny Hawley, policy manager at Plantlife International.

Across the UK today, thousands of people will be raising awareness about the need to reduce air pollution. Most will be rightly and primarily motivated by the damage caused to our health, particularly children’s health. Yet tackling air quality can also help us to tackle the nature and climate crisis, and lead to a more sustainable food and farming system. 

Air pollution and greenhouse gas emissions are natural policy partners, with many of the same sources: fuel combustion for transport, industry and energy, and farm livestock and fertilisers. Action, such as the phase out of petrol and diesel engines, is a huge step forward in improving public health and mitigating climate change in one fell swoop. It makes sense to take an integrated approach. Well designed policy can also help to reverse biodiversity loss and environmental pollution on land and in our rivers and seas.

Nitrogen from agriculture should be a priority
A continuous thread running through these interrelated policy issues is the nitrogen cycle. Often overshadowed by its more famous carbon cousin, the global nitrogen cycle is vital to life on Earth. As an inert gas, it makes up nearly 80 per cent of our atmosphere and, in its reactive forms, it’s essential to plants and animals, and therefore for food production. But nitrogen is easy to overlook. In agro-environment policy, we talk about fertilisers, nutrient management plans, ecosystem enrichment and eutrophication, yet they are often not seen as part of the picture on air quality and climate change.

‘Laughing gas’ is a greenhouse gas (nitrous oxide) with 300 times the global warming potential of CO2, mostly emitted from farm manures and synthetic fertilisers, so not so funny after all. Ammonia (NH3) from agriculture and NOx from fuel combustion both contribute to the formation of secondary particulate matter (PM), which is a priority for government in improving air quality and public health.

These same pollutants are driving the loss of many wildflowers, lichen and fungi, which cannot cope in such fertile conditions. As these species quietly disappear, their ecosystems become degraded, along with the services they provide, mossy peatbogs and wildflower meadows are overrun with nitrogen-loving plants such as grasses and nettles, eventually becoming a different, less biodiverse ecosystem altogether. Reactive nitrogen can travel long distances in the atmosphere, causing damage at the tops of our mountains and across national borders. At least 40 per cent of the nitrogen present in UK farm fertilisers is lost to the environment, much of this to our rivers as nitrates, which we then spend billions of pounds cleaning up.  

Plantlife’s campaign to protect wild plants and fungi from excess nitrogen in the air has helped to raise awareness and encourage government action on air quality for nature as well as people. A new survey shows that 80 per cent of people believe it’s important to reduce air pollution because of the impact on nature as well as people’s health.

An integrated approach to cutting nitrogen pollution, in all its forms, is a huge and urgently needed opportunity to achieve lasting improvements to air, soil and water quality, greenhouse gas emissions, biodiversity, ecosystems and public health.

Regulation has been ineffective so far
Extraordinary levels of inefficiency and pollution from agriculture have continued for too long; regulation has been largely ineffective, absent or unenforced. Ammonia and nitrous oxide emissions remain largely unregulated in all four nations, except for the most intensive pig and poultry units. We import vast quantities of embedded nitrogen in our food, animal feed and fertilisers, much of it from countries where nitrogen pollution is also a significant problem. In fact, due to progress in cutting carbon emissions (and NOx emissions as a by-product) most of the excess nitrogen lost to our air, water and soils, both in the UK and globally, now comes from food and farming. The estimated cost of this pollution is $200 billion each year.

In Scotland, the government has shown impressive leadership by requiring the production of a national nitrogen balance sheet, quantifying all nitrogen flows and identifying priorities for action across society. Plantlife is calling on the UK government and devolved administrations to follow suit and create a UK-wide nitrogen budget to sit alongside national carbon budgets, and recognise the need for more concerted action against this significant and pernicious air pollutant. This really would be a progressive, world leading approach to cleaning up our air, improving nature and defending against climate change.

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