The Challenge
Global nitrogen losses to the environment are at an all time high
Reactive nitrogen is a harmful substance both when dissolved in water and as a gas. When there is an imbalance of nitrogen in the environment, it contributes to climate change, pollutes biodiverse habitats, waterways, soil and air.
Overview
Since the 1950s, humans have more than doubled the amount of reactive nitrogen in the world, largely through agricultural practices and management. After the second World War, farmers were encouraged by the government to use synthetic nitrogen fertiliser to increase yields and meet food demand. But only in recent decades has the environmental impact of excess fertiliser use been realised. More recently, increasing demand for cheaper meat has driven the intensification of livestock systems, driving input use and subsequent losses of nitrogen, leading to polluted air and water systems.
Fertiliser use also helped higher income countries to sustain a huge increase in human populations, alongside other drivers this led to developments in industrial processes and fuel combustion. As technologies progressed, vehicles grew in popularity and aviation transport meant human travel became global.
When airborne nitrogen from agricultural sources mixes with other airborne particles, including nitrogen pollution from traffic, dangerous particulate matter pollution is produced. With technological improvements and the move towards greener vehicle fleets, roadside pollution levels have been decreasing since the 1990s, meaning the percentage of particulate matter pollution contributed by agriculture is increasing.
Now it is recognised that the global costs of the current level of excess nitrogen outweighs the benefits of synthetic nitrogen-based agricultural systems. Conventional agriculture must now move in the direction of low-input systems which are more resilient and produce food with less pollution.
Nitrogen contributes up to 43,000 premature deaths per year in the UK through air pollution and accounts for 4% of UK global warming potential. Excess nitrogen drives biodiversity decline across the country, with over 99% of nitrogen-sensitive habitats above recommended nitrogen levels in England and many species unable to tolerate these conditions. As a significant driver of water pollution, it contributes to deteriorating water quality and fish populations with only 14% of rivers in England in good ecological health.
The causes and impact of excess nitrogen is wide ranging
Through this Alliance, we are using our collective advocacy and expertise to be more than the sum of our parts, utilising our wide-ranging knowledge of specific impact areas to develop systemic nitrogen solutions.
Current government action is disjointed and unambitious, with the UK’s statutory targets and the Environment Improvement Plan lagging behind international commitments. Government and industry prioritise reducing carbon emissions to meet the national target to reach Net Zero by 2050, yet nitrous oxide has a global warming potential 273 times greater than that of carbon dioxide.
Different forms of nitrogen cause damage in different impact areas
Nitrogen Oxides
Biodiversity
Health
Nitrate
Biodiversity
Health
Food
Ammonium
Biodiversity
Health
Food
Ammonia
Biodiversity
Health
Food
Nitrous Oxide
Climate
Health
Nitrogen impacts and sources
Biodiversity
What is the impact of nitrogen pollution on biodiversity?
Terrestrial
Biodiversity is damaged by reactive nitrogen which can travel great distances through the air, far from its source. It is then deposited in the environment, through wet or dry deposition, overloading the sensitive balance of nutrients within species-rich environments. Excessive nitrogen drives populations of ‘generalists’ which outcompete ‘specialists’ meaning that biodiversity and species abundance declines over time as generalist species take over. The nitrogen critical load (a measure of nitrogen pollution in sensitive habitats) is exceeded in 95% of the area of woodlands in the UK (managed and unmanaged), even in Atlantic rainforests on the west coast of Wales, far from large nitrogen sources such as transport and intensive agriculture. Atmospheric nitrogen deposition is also increasing carbon loss from peat bogs and about 15% of woodland soil in England and Wales is nitrogen saturated, which can increase nitrate leaching from soils and associated aluminium toxicity to the plant roots. Nitrogen deposition increases the prevalence of acid rain by increasing the nitrogen oxides in the atmosphere which react with sulphur dioxide - 36% of UK land area is sensitive to acidification, and 38% is sensitive to nutrient nitrogen through eutrophication - the excessive richness of nitrogen.
Click here to read more about the impact of nitrogen on wild plants and fungi
https://www.plantlife.org.uk/our-work/clean-air-wild-plants-fungi/
Freshwater
Nitrogen causes harm in soil and surface water as organic nitrogen compounds, nitrate and ammonium. As the predominant drivers of deteriorating water quality in English rivers, these pollutants cause eutrophication in water systems by driving algal blooms. When these blooms grow to the point of blocking out light, populations of other plant species and fish plummet contributing to ecological dead zones. As all rivers lead to the sea, nitrogen pollution of rivers and waterways in turn impacts the coastal and marine ecosystems.
In the UK, only 16% of water bodies meet the criteria for ‘good’ ecological status, and 50% and 40% of water bodies achieve good status in Scotland and Wales, respectively. Since 2019, 55% of England has been designated as a Nitrate Vulnerable Zone due primarily to elevated nitrate concentrations in groundwater and rivers. This means farmers must implement certain land management practices in order to reduce the impact on surrounding waterways.
Health
What is the impact of nitrogen pollution on health?
Nitrogen damages human health in a number of ways; through air pollution, deteriorating water quality and as the primary driver of stratospheric ozone depletion. Nitrogen drives air pollution in the form of nitrogen oxides (NOₓ), emitted mainly from traffic, industry and domestic heating, and as ammonia (NH₃), mainly emitted from agriculture. These pollutants are damaging in their own right, but when combined with other molecules in the air (mainly sulphur) they form particulate matter pollution (PM2.5). As part of the ‘cocktail’ that can lead to the formation of photochemical smogs, nitrogen oxides also induce the formation of tropospheric (low-level) ozone, which causes asthma and chronic respiratory problems. While ammonia doesn’t last long in the atmosphere on its own, PM2.5 can travel great distances, meaning agricultural sources are a key driver of air pollution in urban areas, contributing to a quarter of PM2.5 in London, and almost 40% in Leicester. High levels of ammonia causes swelling of the airways and lung damage, with cases of stomach and heart damage, while air pollution from PM2.5 causes asthma, chronic lung and heart diseases, and contributes to 40,000 premature deaths in the UK annually.
Click here to read more about air pollution:
https://www.cieh.org/news/press-releases/2023/concerns-over-air-quality-as-new-defra-statistics-show-significant-rise-in-emission-of-pm25/
Climate
What is the impact of nitrogen pollution on climate?
Nitrous oxide (N2O) contributes roughly 6% of UK total greenhouse gases, with a global warming potential which is 273x that of carbon dioxide, yet action on GHGs has been targeted on carbon dioxide. There is an ongoing risk that emissions of N2O will remain a low priority in future unless action is taken to highlight the opportunity for sustainable nitrogen management to offer win-win situations between climate, wider environmental protection and economy.
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Greenhouse gases increase the global temperature by trapping heat from the sun. A rapidly warming planet means natural processes like rainfall patterns, climates and ocean currents are disrupted. Global warming also increases climatic events such as flooding, droughts, tornadoes, wildfires and hurricanes. Species struggle to adapt to changing climates as access to water and food becomes more difficult.
Food
What is the impact of nitrogen pollution on food?
The way we currently live and eat is outstripping the planet’s capacity to provide for us. In order to ensure we can meet our needs and those of the natural world now and into the future, we need to change the demands we make of our planet, make best use of our land and align what we consume with what we can sustainably produce.
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The food system is the largest source of nitrogen pollution across the environment and the economy. In Europe, 80% of the continent’s nitrogen emissions are a result of the food system. Such great nitrogen losses occur because soils in all regions of England are oversaturated with nitrogen. Some receive more than double their absorption potential and excess runs off into waterways or is lost as air pollution or nitrous oxide. In England, the regions with high concentrations of industrialised indoor-reared livestock have the biggest nitrogen surplus because more than 40% of total nitrogen pollution comes from livestock manure.
Eutrophication Potential is a measure of the potential to cause over-fertilisation of water and soil. Nitrogen and phosphorus are the main chemicals responsible for eutrophication and some foods have a much higher eutrophication potential than others. Dairy, beef, farmed seafood, pork, bacon and coffee all come with a high eutrophication impact, while fruits and vegetables, nuts, legumes, cereals and peas have a much lower impact.
Intensive poultry units import soya feed from Brazil and Argentina to sustain the tens of thousands of chickens housed in each shed. This soya is typically grown in the drier Cerrado region of the Amazon basin - a biome even more reduced and degraded than the rainforest. High levels of deforestation have been driven by meat demand in the UK and other more economically developed countries.
Sources of Nitrogen Pollution
Synthetic nitrogen fertiliser
Since the 1950s, humans have more than doubled the amount of reactive nitrogen in the world, largely through agricultural practices and management. A growing population led to an increasing demand for food that drove the agricultural system to maximise yields at all costs. While the financial costs of synthetic fertiliser use have increased dramatically in recent years, the environmental impacts of synthetic fertiliser use are not yet accounted for.
The use of synthetic nitrogen holds a number of issues. The manufacture of ammonium nitrate from nitrogen and hydrogen is an energy intensive process requiring fossil fuels, meaning there are inherent greenhouse gas emissions associated with production processes. Several factors associated with the application of nitrogen fertiliser to fields impact nitrous oxide production, particularly soil N concentration, soil moisture, soil temperature, fertiliser application amounts, and land use management. In total, the production and use of synthetic fertiliser is responsible for 5% of global greenhouse gas emissions.
Nitrogen deposition and the resulting increased acidity from synthetic nitrogen fertiliser harms biodiversity both on-farm and in surrounding habitats. Excess nitrogen fertiliser also runs off agricultural soils and causes eutrophication of surrounding waterways, harming marine fish and plant populations.
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The Solutions
An integrated approach can deliver multiple benefits more effectively for people, nature and our climate
