Agricultural pollution is one of the world's most costly and pervasive environmental problems. As the global population continues to grow and become wealthier, there will be more pressure on farms to produce and thus more pollutants being released into the air and water. Agricultural emissions are projected to increase 15% to a total of 7 billion tonnes per year by 2030.
Farmers spread synthetic fertilizer or manure, both rich in nitrogen and phosphate, to restore nutrients to the soil to help crops grow. However, plants cannot absorb all the nutrients at once, and so excess nutrients are washed away. Fertilizer runoff pollutes the air and water, which can be dangerous to animal and human health. The EPA estimates that nutrient pollution is “one of America’s most widespread, costly and challenging environmental problems.” Drinking or swimming in contaminated water can cause illness and even death, especially for infants, while nitrous oxides emitted from fertilizer use are strong greenhouse gases and can cause smog and acid rain.
In spite of the huge costs of nutrient pollution, farmers continue to spread excess fertilizer to ensure high crop yields. Fertilizer is an insurance policy for farmers. By spreading too little, they may not achieve maximum yield, whereas spreading too much will not hurt crops. Nutrient pollution is an externality, meaning that farmers don’t directly absorb the costs of pollution. Communities downriver suffer the most. Many people with varying interests and several jurisdictions or states are implicated, making it difficult for everyone to agree on a single solution to nutrient pollution.
RUNOFF
Fertilizer runoff from farm fields causes widespread pollution
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Agriculture contributes 13% of all greenhouse gases globally, making it the second largest source of emissions behind the energy sector. Changes in population and wealth are projected to increase global agricultural emissions by 15% above 2010 levels by 2030, bringing them to a total of 7 billion tonnes per year. Nitrous oxides are one the the primary greenhouse gases emitted by agricultural activities. Fertilizer use is the leading cause of nitrous oxide emissions, an extremely potent greenhouse gas. Although carbon pollution is more widespread, nitrous oxide is 300 times more powerful a greenhouse gas than carbon dioxide. In the US, fertilizer application and other cropping practices comprise about 79% of nitrous oxide emissions.
CLIMATE
Agriculture contributes 9% of all greenhouse gas emissions
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When nitrogen and phosphorus leaves the field as runoff, they pollute groundwater and other water sources that humans and ecosystems rely on. A U.S. geological survey discovered that 64% of wells in agricultural and urban areas were too high in nitrates. Drinking or swimming in contaminated water can cause rashes, stomach or liver illness, respiratory problems, miscarriage, and neurological effects. The most vulnerable are most likely to suffer. Infants who drink contaminated water high in nitrates may fall ill and even die, suffering from a condition known as blue baby syndrome in which they are short of breath and have blue-tinted skin.
Contaminated water is eventually swept through the watershed and deposited at an endpoint such as the Gulf of Mexico or Chesapeake Bay. Algae in aquatic habitats feed off these nutrients. Except in this case, huge blooms of algae form that block out sunlight, clog fish gills, and may become toxic to aquatic animals or humans who come into contact with the water. When disinfectants used to treat drinking water react with toxic algae, dangerous chemicals called dioxins are created that have been linked to reproductive complications, developmental health risks, and cancer. These huge algae blooms can tie up all the dissolved oxygen in the water, creating a condition called hypoxia in which there is not enough oxygen in the water to support life. Animals must leave or suffocate, creating “deadzones” that can stretch for thousands of miles.
WATER POLLUTION
Over 60% of wells are too high in harmful nitrates
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Spreading fertilizer causes airborne nutrient pollution. Acid rain from air pollution harms lakes, streams, estuaries, forests, and grasslands. In addition, nitrogen oxides aid ground-level ozone formation. Ozone in the stratosphere protects life from deadly ultraviolet rays, but is harmful when present at the ground level. Breathing in ozone can cause a host of lung-related ailments, including worsened asthma and reduced lung function. Ironically, ground-level ozone also damages crops and other vegetation, costing farmers about $500 million a year.
AIR POLLUTION
Nitrous oxides in the air causes acid rain, smog, and ozone pollution
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