One of the world’s greatest challenges in the 21st century is to ensure we can grow enough food for everyone while safeguarding the long term viability of the planet. The global food system currently leaves 870 million people hungry and accounts for approximately 20% of greenhouse gas emissions, so we must learn to grow more, with less. As Rotarians, we need to keep environmental concerns in mind when running projects. Why? Sustainability can also be thought of as intergenerational equality – we do not want to take from future generations in order to sustain current ones.

You no doubt have heard of carbon dioxide and its role in climate change, but another pollutant is coming on the scene that we should start talking about. Nitrogen. It contributes to climate change, but also adversely affects biodiversity, ozone depletion, food security, hunger, water pollution and air quality.

Nitrogen is responsible for growing our food (it's a key ingredient in fertilizer), but too much can wreak havoc on human health and the environment. According to the US Environmental Protection Agency, nitrogen pollution is one of America’s most widespread, costly and challenging environmental problems! It's a big problem in many other areas of the world too, including Europe, China and India.

Some quick facts about Nitrogen:

  • Approximately 45% of the crops grown worldwide use chemical nitrogen fertilizer
  • Nitrogen has helped humanity grow enough food to feed the 7 billion people on earth (though there are still food distribution and poverty problems)
  • Excess nitrogen in the environment costs the European Union (EU) between €70 billion (US$100 billion) and €320 billion per year, mainly due to human health costs associated with respiratory diseases
  • About 80% of European fresh waters exceed a threshold for high risk to biodiversity due to high levels of nitrates
  • Nitrogen emissions have reduced forest biodiversity by more than 10% over two-thirds of Europe
  • Nitrous oxide is now the leading cause of ozone depletion, since it is not regulated like CFCs


It’s a balancing act, and we’ve tipped the scales

Nitrogen will be a key factor in achieving a balance of sustainability and food supply. It is the main component in fertilizer, and is key to soil fertility. It is created naturally in the soil by some plants and trees, but early in the 20th century we discovered how to create it chemically using natural gas and inert, atmospheric nitrogen (which makes up approximately 80% of our atmosphere and is harmless). This enabled food to keep pace with population growth, which grew exponentially from 1950.

Like CO2, nitrogen is naturally occurring and is an important part of making our world function. Without CO2, our planet would be too cold to sustain life, but too much heats up the earth and causes climate change. Similarly, nitrogen is essential for plant growth, but when too much of it gets released into the environment it causes serious health and environmental problems.

As the need for more food increases, the demand for nitrogen will increase, thus is will increasingly become an issue in the 21st century.


Where does nitrogen come from?

Sources of nitrogen include fertilizers (applied to agricultural fields, golf courses, and suburban lawns), nitrogen-fixing crops, animal manure, fossil fuel burning, erosion of soil that contains nitrogen, industrial and sewage treatment plant discharges, and natural sources (soil bacteria, algae, lightning, etc.).

Driven by a massive increase in the use of fertilizer, the burning of fossil fuels, and land clearing and deforestation, the amount of nitrogen available in the environment has skyrocketed since the 1960s, dwarfing the 25 % increase in atmospheric CO2 during the same time period[1]. Human activities now contribute more to the global supply of fixed nitrogen each year than natural processes do.

Fixed (also known as "reactive") nitrogen can take many forms and impacts the air and water differently. For example, nitrous oxide (NOx) is a potent greenhouse gas, destroys the ozone layer and causes respiratory diseases. Nitrates in water pollutes drinking water and causes algae blooms (eutrophication). Because these forms of nitrogen have a lifespan of about 120 years before finally reverting back to inert nitrogen (N2), they can break apart and re-form many times, affecting many people and earth systems along the way. For more information on the various forms of nitrogen, see a comprehensive list of nitrogen terms, provided by the Woods Hole Research Center. For the sake of simplicity, in this post all the reactive forms of nitrogen are referred to simply as "nitrogen".


How does nitrogen affect the ecosystem?

Nitrogen helped create the hole in the ozone layer, and is the leading cause of ozone depletion in the 21st century[2]. It is a major component of acid rain, which weakens the ecosystem and impacts biodiversity. It is estimated that nitrogen has reduced forest biodiversity by 10% across over two-thirds of Europe[3]. For example, forests in some parts of Northern Europe receive 10 times the natural levels of nitrogen from the air[4].

When it ends up in rivers, lakes, or seas, it can create algal blooms that kill fish, choke coral and break down the food chain. Globally, eutrophication (algae blooms) of coastal systems has risen from fewer than 75 systems in 1960 to more than 800 systems today. Of these, more than 500 have experienced hypoxia, or dead zones[5]. In the United States, two thirds of coastal systems are moderately to severely impaired due to nutrient loading, and 1/3 of streams and 2/5 of lakes are impaired by high nitrogen concentrations: coastal rivers in the northeastern United States and northern Europe receive as much as 20 times the natural amount of nitrogen[6].

Nitrous oxide is also a powerful greenhouse gas. While there is less of it in the atmosphere than carbon, its warming effect is 300 times that of CO2, and accounts for approximately 9% of global greenhouse gas emissions[7].


How does nitrogen affect human health?

The impacts of nitrogen pollution on human health are detrimental and costly. In industrialized nations, the effects of nitrogen pollution are mainly though cardiovascular and respiratory illnesses due to nitrogen smog. In Europe, it is estimated that the effects of these airborne particles take 6-9 months off the life expectancy of at least half of its population[8], and an estimated 811,000 people annually die prematurely from elevated levels of particulate matter[9].

Nitrates in water have been shown to have a wide range of health impacts. Ingesting high levels of nitrates has been associated with cancer, adverse reproductive outcomes and issues with spleen, kidney, and thyroid functions[10]. While most industrialized countries remove nitrates from drinking water, those that depend on well water are at risk. In the San Joaquin Valley in California, for example, over 40% of the wells tested contained illegal levels of nitrates. The poor are often the most affected: Low income residents must spend an average of 4.6% of household income on bottled water to avoid contaminated well water, more than three times the affordability threshold for drinking water recommended by the US EPA[12].

In the developing world, Malaria, cholera, schistosomiasis and the West Nile Virus have also been found to spread more quickly when nitrogen is abundant. Nitrogen and phosphorous runoff fuels greater plant growth in water bodies, creating a bigger habitat for disease-spreading animals such as mosquitoes and snails[13].


How does nitrogen pollution affect the economy?

Nitrogen has positive and negative effects on the economy. Positive effects are primarily from in the increase in crop yields from fertilizer. In the EU for example, manufactured fertilizer produces a direct benefit to European farmers, in terms of crops grown, of €20 billion to €80 billion per year, when the long-term benefits are included. On top of that, biological fixation and recycled sources of nitrogen — including plant residues, animal manures and atmospheric deposition — add 17 million tonnes, giving a total direct benefit of €25 billion to €130 billion, even before value is added during the food-supply chain[14].

But half of the nitrogen in fertilizers and manures is lost to the surrounding environment, leaching into the air and water systems. In economic terms, this amounts to a loss of potential benefits to farmers of €13 billion to €65 billion per year[15].

Beyond the economic benefits and costs of fertilizers directly, there are significant costs to from health care and impacted industries. In the United States, the EPA considers nitrogen pollution to be one of their most costly and challenging environmental problems. In the EU, the total cost of nitrogen pollution is estimated at €70 billion to €320 billion per year, which is equivalent to 1–4% of the average disposable per capita income of European citizens[16]. Estimates on costs from China suggest that air particulates from road transport for Beijing residents alone account for $300 million dollars annually, an equivalent of 0.58% of their GDP[17]. Cleaning freshwater drinking supplies is also costly. A 2002 estimate suggests the damage costs of freshwater eutrophication in England and Wales to be £75.0-114.3 million annually[18].

The economic costs extend beyond public health to other major industries, primarily fishing and tourism. Eutrophication of freshwater and coastal water bodies severely degrade fish stocks and destroy supporting ecosystem services. Algal toxins can also be transmitted up the food chain to other marine species including (farmed) fish, birds and marine animals. Nutrients cause an increase in plankton, and some plankton species have sharp spines that can damage gill tissue, making fish more susceptible to disease. The frequency of mortalities due to algal blooms around salmon farms is increasing. When these mortalities occur, salmon farmers suffer significant financial losses. In the US, an average 6,688 square-mile dead zone in the Gulf of Mexico has battered the region’s $2.8 billion fisheries industry[19].

Eutrophication, or algae blooms, can affect the tourism and housing industries. Toxic algae sludge from nutrient pollution is both ugly and pungent, reducing the property values and disincentivizing water-based tourism and ecotourism activities.


How Does Nitrogen Compare to Other Environmental Issues?

In 2009, a guy named Johan Rockstrom tried to compare various threats to the environment on a global scale. While there are inherent challenges in this approach (for example, some problems are far more localized than others), it gives a relative degree of “how much we should care” about the problem. As shown above, we are at least 3.5 times beyond the global “safe boundary” for nitrogen use.


What can Rotarians do?

There are two things that Rotarians can do. The first one is to think about the impact of nitrogen in your projects, particularly those that have to do with community development. Are there solutions that are good for people and good for the environment?
The most important thing that every individual can do is eat less meat. I’m not vegetarian, but I have cut my meat consumption in half as a result of knowing about the damaging effects of nitrogen. Because so much of our agriculture goes into animal production, eating less meat reduces our “nitrogen footprint” considerably.
Did you know:

  • Livestock consume around 85% of the 14 million tonnes of nitrogen in crops (EU figures), only 15% of crops is used to feed humans directly
  • If Europeans obtained all their protein from plants, only 30% of the crops grown currently would be needed, reducing nitrogen fertilizer inputs and the associated pollution by 70%
  • If Americans ate the recommended amount of meat by the National Institute of Health, they could reduce their nitrogen footprint by 45% and be healthier as a result!

Ways to Reduce Meat Consumption:

  • Meatless Mondays! Go meatless one day a week
  • Be a "Demi-tarian" and cut your meat consumption in half
  • Eat less nitrogen intensive meat. Chicken requires about 1/4 the nitrogen of beef
  • Supplement meat protein with vegetable protein such as hummus and quinoa
  • Reduce food waste - approximately 30% of all food goes to waste worldwide. Eat your leftovers, and ask for a to-go box at restaurants if you have extra




1.   Alan R. Townsend and Robert W. Howarth. Fixing the Global Nitrogen Problem. Scientific American. 2010.  
2.   A R Ravishankara, John S Daniel, Robert W Portmann. Nitrous oxide (N2O): the dominant ozone-depleting substance emitted in the 21st century. Science. 2009.
3.   Mark Sutton et al. Too Much of a Good Thing. Nature. 2011.
4.   WRI. Nutrient overload: Unbalancing the global nitrogen cycle. World Resources Institute. 1989.
5.   Mindy Selman. How Food Production Impacts Water Quality. World Resources Institute. 2012.
6.   Eric Davidson et al. Excess Nitrogen in the U.S. Environment: Trends, Risks and Solutions. Issues in Ecology. 2012.
       Fred Pearce. Planet Earth is Drowning in Nitrogen. New Scientist. 1997.
7.   Peter Smithson, et al. Fundamentals of the Physical Environment. Routledge. 2008.
8.   Mark Sutton et al. Too Much of a Good Thing. Nature. 2011.
9.   Armistead Russell and Bert Brunekreef. A Focus on Particulate Matter and Health. Environmental Science and Technology. 2009.
10. Alan R. Townsend and Robert W. Howarth. Fixing the Global Nitrogen Problem. Scientific American. 2010.
11. Catherine Zelman. New questions and insights into nitrate/nitrite and human health effects: a retrospective cohort study of private well users' immunological and wellness status. Environmental Health. 2011.
12. Eli Moore and Eyal Matalon. The Human Costs of Nitrate-contaminated Drinking Water in the San Joaquin Valley. Pacific Institute. 2011.
13. Alan R. Townsend and Robert W. Howarth. Fixing the Global Nitrogen Problem. Scientific American. 2010.
14. Mark Sutton et al. Too Much of a Good Thing. Nature. 2011.
15. Mark Sutton et al. Too Much of a Good Thing. Nature. 2011.
16. Mark Sutton et al. Too Much of a Good Thing. Nature. 2011.
17. X. R. Guo et al. Estimation of economic costs of particulate air pollution from road transport in China. Atmospheric Environment. 2010.
18. J. R. Pretty et al. A preliminary assessment of the environmental costs of the eutrophication of fresh waters in England and Wales. University of Essex. 2002.
19. EPA. Moving forward on Gulf Hypoxia Annual Report. US Environmental Protection Agency. 2011.

Website Sponsors