Brian Barton
Agriculture is a major contributor to pollution, with farming practices leading to contaminated or degraded environments and ecosystems. The agricultural sector consumes about 69% of the world's freshwater, and unsustainable practices can lead to excessive water consumption and degradation of water quality. The use of pesticides and fertilizers, for example, can poison freshwater, marine ecosystems, air, and soil, and remain in the environment for generations. Animal waste is another major contributor to air, soil, and water pollution, with manure emitting ammonia, which combines with other air pollutants to create deadly solid particles.
| Characteristics | Values |
|---|---|
| Soil erosion | Agriculture contributes to soil erosion through intensive management or inefficient land cover. |
| Sediment deposition | Sedimentation in runoff water affects water quality and transport capacity of water bodies, and interferes with the feeding habits of fishes. |
| Water pollution | Agricultural runoff is the leading cause of water quality impacts to rivers and streams, and the second largest source of impairments to wetlands. |
| Air pollution | Agricultural air pollution is caused by ammonia from heavily fertilized fields and livestock waste, which combines with industrial emissions to form solid particles. |
| Greenhouse gas emissions | Agriculture accounts for about 11% of U.S. emissions, with livestock being the second-largest contributor of greenhouse gas emissions globally. |
| Nutrient pollution | Excess nitrogen and phosphorus from chemical fertilizers and animal manure can cause eutrophication of water bodies, leading to hypoxia and harmful algal blooms. |
| Pesticide use | Pesticides used in agriculture can contaminate water sources and have direct impacts on surrounding ecosystems, such as killing local wildlife. |
| Land use | Agriculture uses half of the world's habitable land, contributing to the loss of natural habitats and a reduction in biodiversity. |
| Water consumption | Agriculture requires large amounts of freshwater, causing environmental pressures in regions with water stress. |
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What You'll Learn
Livestock and manure
Livestock and their manure contribute to air pollution. The EPA reports that manure management accounts for 12% of all agricultural greenhouse gas emissions in the United States, and globally, it accounts for 14.5%. Manure emits ammonia, which combines with other air pollutants, such as nitrogen oxides and sulfates, to create solid particles that are harmful to humans. These particles are said to cause heart and lung diseases and account for millions of deaths each year globally.
The demand for livestock products is expected to increase due to population growth and changes in dietary preferences, especially in developing countries. This will result in an increased need for better manure management practices to prevent an equal rise in emissions and other issues arising from manure collection, storage, treatment, and utilization. Manure is often disposed of in piles, slurries, or lagoons, which can lead to significant methane emissions, environmental degradation, negative health impacts, and the loss of valuable nutrients that could benefit the soil.
Good manure management can reduce the need for manufactured fertilizers. Effective storage techniques, such as covered structures and lagoons, are essential in preventing nutrient leaching, runoff, and greenhouse gas emissions. Proper transportation planning, field application methods, and comprehensive nutrient management plans are also vital to optimizing nutrient uptake, minimizing runoff, and reducing environmental impact.
Livestock manure is a significant source of nutrient pollution, which primarily results from human activities and deteriorates water quality. Nutrients in manure, such as nitrogen and phosphorus, can stimulate algal blooms in lakes and rivers, leading to hypoxic conditions that are harmful to aquatic life. Bacteria and nutrients from livestock manure can also contaminate drinking water supplies and cause beach and shellfish bed closures.
The livestock sector is responsible for a large portion of global greenhouse gas emissions, with methane and nitrous oxide being the most important gases. Methane is produced by enteric fermentation, a process in the digestive system of ruminant animals, and has a much higher global warming potential than carbon dioxide. Nitrous oxide is emitted when organic and inorganic fertilizers are applied to the soil.
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Pesticides and fertilizers
Fertilizers, for example, are a major source of water pollution. In the United States, about 12 million tons of nitrogen and 4 million tons of phosphorus fertilizer are applied to crops annually. When excess nitrogen makes its way into the atmosphere, it can become nitrous oxide, a potent greenhouse gas, or nitrogen oxide, which contributes to ground-level smog. Nitrogen oxide, along with ammonia from livestock manure, can also combine with other air pollutants to create tiny solid particles that are harmful to human health.
Fertilizers are also a leading cause of water quality issues in rivers and streams, the third leading source for lakes, and the second-largest source of impairments to wetlands. Nutrient pollution from fertilizers causes eutrophication in ditches and river courses, stimulating algal blooms that can lead to the development of hypoxic conditions harmful to aquatic life. Excessive sedimentation from erosion, which can be caused by agricultural practices, can overwhelm aquatic ecosystems, smother breeding areas, and degrade coastal and marine ecosystems, including coral reefs.
Pesticides are another major contributor to water pollution. In the United States, about half a million tons of pesticides are applied to crops annually. Pesticide runoff can pose risks to aquatic life, fish-eating wildlife, and drinking water supplies. Pollutants from agricultural pesticides can also enter groundwater and degrade sources of drinking water.
The use of pesticides and fertilizers in agriculture can have significant environmental and human health impacts. Addressing these concerns is crucial for developing a sustainable food system and mitigating climate change.
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Water pollution
Agriculture has a profound effect on the planet, and certain agricultural practices can lead to significant water pollution, affecting both ecosystems and human health. The National Water Quality Assessment shows that agricultural runoff is the leading cause of water quality impacts to rivers and streams, the third leading source for lakes, and the second-largest source of impairments to wetlands.
Agricultural runoff is a nonpoint source category of pollution. Rainfall and snowmelt transport the majority of these pollutants to surface waters, but other factors, such as cattle loafing in stream corridors and stream channel erosion, can also contribute. The overuse of pesticides and fertilizers can lead to excessive algal blooms, which can lead to the development of hypoxic (low oxygen) conditions that are harmful to aquatic life. Algae can also affect the recreational use of local streams, downstream reservoirs, and estuaries.
The use of pesticides and fertilizers is a major contributor to water pollution. Farmers often apply large amounts of chemical fertilizers and pesticides to promote crop growth and protect against pests. When it rains or when fields are irrigated, excess fertilizers and pesticides can wash off the fields into nearby rivers, lakes, or streams. Increased levels of nitrogen and phosphorus from fertilizers and manure can stimulate algal blooms in lakes and rivers.
Soil erosion, nutrient loss, bacteria from livestock manure, and pesticides constitute the primary stressors to water quality. Nutrients in fertilizer and livestock manure, pesticides, and other substances don't always remain stationary on the landscape where they are applied. Runoff, infiltration, and irrigation return flows can move these contaminants into local streams, rivers, and groundwater.
In recent decades, the area equipped for irrigation has more than doubled, from 139 million hectares in 1961 to 320 million in 2012, transferring agricultural pollution to water bodies. The total number of livestock has also risen from 7.3 billion units in 1970 to 24.2 billion in 2011. Livestock production now accounts for 70% of all agricultural land and 30% of the planet's land surface. Fish excreta and uneaten feeds from aquaculture diminish water quality. Increased production has combined with the greater use of antibiotics, fungicides, and anti-fouling agents, which may contribute to polluting downstream ecosystems.
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Soil erosion
The effects of soil erosion include the loss of fertile land, increased pollution and sedimentation in streams and rivers, clogging waterways, and causing declines in fish and other species. As land loses its fertile soil, agricultural producers move on to clear more forests, continuing the cycle of soil loss. Soil erosion can also reduce the soil's ability to absorb water, leading to flooding and the creation of large areas of standing water.
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Greenhouse gases
Agriculture is a significant contributor to anthropogenic global warming, with agricultural activities emitting three primary greenhouse gases: carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4). These gases are released into the atmosphere through various agricultural processes and have different impacts on climate change.
Carbon Dioxide (CO2)
Carbon dioxide is emitted through activities such as the tilling of fields, planting of crops, and shipment of products, burning of fossil fuels for heating and powering equipment, and decomposition of organic matter. CO2 is the dominant greenhouse gas, and its concentration in the atmosphere can be affected by deforestation, with forests acting as a sink for absorbing CO2.
Nitrous Oxide (N2O)
Nitrous oxide is released primarily through the application of agricultural fertilizers to soils and manure management. It has a much higher global warming potential than CO2, with a capacity 273-296 times greater. Reducing nitrous oxide emissions requires conscious use of chemical fertilizers, pesticides, and manure, along with implementing inhibitors to regulate nitrogen processes in soils.
Methane (CH4)
Methane is formed through "enteric fermentation" in the digestive systems of ruminant livestock (cattle, sheep, and goats). It is also produced through the decomposition of animal manure, rice cultivation, and anaerobic decomposition of organic matter in wet soils. Methane is the number one contributor to agricultural greenhouse gases globally, with cattle being a major driver. While methane has a shorter residence time in the atmosphere than CO2, it is much more effective at trapping heat, with a global warming potential 27-30 times greater than CO2 over 100 years.
Mitigation Strategies
To counterbalance the increase in greenhouse gases, carbon sequestration, the capture, and long-term storage of atmospheric CO2 in soil, is a proposed solution. This includes enhancing biomass production, using bio-fertilizers, adopting conservation practices, and improving manure management. Additionally, diet changes towards ruminant-free alternatives, such as milk substitutes and meat analogues, can also help reduce methane emissions.
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Frequently asked questions
Agriculture contributes to air pollution through livestock and their manure. According to the EPA, manure management accounts for 12% of all agricultural greenhouse gas emissions in the United States. Globally, manure management accounts for 14.5% of agricultural greenhouse gas emissions.
Agriculture contributes to water pollution through agricultural runoff, which includes fertilizer and manure. According to the National Water Quality Assessment, agricultural runoff is the leading cause of water quality issues in rivers and streams, the third leading source for lakes, and the second-largest source of impairments to wetlands.
Agriculture contributes to soil pollution through soil erosion and sediment deposition. Intensive management and inefficient land cover lead to soil degradation, resulting in an irreversible decline in fertility on millions of hectares of fertile land each year.
