Agricultural Pollution: America's Growing Threat

Agriculture is a vital sector in the United States, contributing significantly to the country's economy and food supply. However, agricultural activities can also have detrimental effects on the environment, and this is known as agricultural pollution. This type of pollution includes water pollution from agricultural runoff, air pollution from livestock and certain farming practices, and soil erosion. In the US, agricultural nonpoint source (NPS) pollution is the leading cause of water quality issues in rivers and streams and the second-largest source of impairments to wetlands. The improper management of animal waste, overgrazing, and improper fertiliser application are some of the agricultural activities that cause NPS pollution.

Water quality

Agricultural pollution is a pressing issue in the United States, with around 40% of the nation's land dedicated to agricultural use. This extensive farmland has a significant impact on water quality, affecting both local and multi-state watersheds. The leading sources of water quality impairment in the US are municipal point sources, urban stormwater sewers, and agricultural activities.

Agricultural Contaminants

Agricultural contaminants that affect water quality include nutrients, pesticides, and animal waste. Nutrients such as nitrogen and phosphorus are essential for plant growth, but when used excessively in synthetic fertilizers, they can contaminate surface and groundwater. This leads to algal blooms, eutrophication, and nitrate contamination, impacting drinking water quality and aquatic ecosystems. Pesticides, including herbicides, insecticides, and fungicides, are also widespread in surface and groundwater across the US. They pose risks to aquatic life, fish-eating wildlife, and drinking water supplies.

Impacts on Waterways

The high levels of nutrients and algae resulting from agricultural pollution degrade water quality and threaten the health and biodiversity of waterways. This can lead to the loss of aquatic life and their habitats, shellfish contamination, and seasonal dead zones. Contaminated water also impacts recreational activities such as swimming and boating, as well as fishing and shellfishing.

Health Risks

Excessive nutrient runoff and chemical pollution in waterways can impact drinking water supplies and pose severe health risks. Elevated nitrate levels in drinking water are dangerous, causing low oxygen levels in infants ("blue-baby syndrome") and low birth weight. Pathogens in animal waste can also contaminate water supplies, leading to diseases. Copper toxicity, for example, can cause gastrointestinal and liver disorders.

CAFOs and Water Pollution

Concentrated animal feeding operations (CAFOs), or factory farms, generate large amounts of animal waste, which is often stored in pits or open ponds called lagoons. These waste-containment areas can leak or rupture during storms, leading to surface and groundwater contamination. Animal waste can contain pharmaceutical residues, heavy metals, and harmful bacteria. Spraying manure on farm fields can result in environmental damage and the contamination of water supplies.

Mitigation Strategies

To address these issues, farmers can adopt soil and water conservation practices, such as contour strip cropping, to reduce the runoff of sediments, nutrients, bacteria, pesticides, and other pollutants. The National Water Quality Initiative (NWQI) aims to reduce agricultural runoff through the implementation of conservation practices. Additionally, buffer strips around fields and streams, drip irrigation, and precise fertilizer application can help minimize water pollution.

Air pollution

Agricultural activities contribute significantly to air pollution in America. The air pollutants from agricultural practices have severe health and environmental implications.

Livestock and Manure

Livestock and their manure are significant sources of air pollution in the United States. According to the EPA, manure management alone accounts for 12% of all agricultural greenhouse gas emissions in the country. Globally, it accounts for 14.5% of agricultural emissions, as per the United Nations' Food and Agriculture Organization. Manure emits ammonia, which combines with other air pollutants like nitrogen oxides and sulfates to create tiny solid particles that are harmful when inhaled. These particles have been linked to heart and lung diseases and are estimated to cause about 3.3 million deaths annually worldwide.

Nitrogen-based Fertilizers

Nitrogen-based fertilizers have played a pivotal role in the industrialization of agriculture, enabling high crop yields even on overtaxed land. However, they have adverse effects on water supplies and the climate. When excess nitrogen enters the atmosphere, it can become nitrous oxide, a potent greenhouse gas, or nitrogen oxide, contributing to ground-level smog. Nitrogen oxides are among the most widely emitted pollutants globally and can directly damage crop cells. They also contribute to the formation of ozone, an airborne toxin that reduces crop yields, and particulate matter aerosols that scatter sunlight away from crops.

Pesticides

Pesticides, including herbicides, insecticides, rodenticides, and fungicides, are commonly used in agriculture to control unwanted weeds, insects, rodents, and fungi. However, these toxic chemicals have serious side effects, including endocrine (hormone) and neurological disorders and cancer. Children are especially vulnerable to the health impacts of pesticide exposure due to their developing bodies. Chlorpyrifos, for example, has been linked to developmental delays, lower IQs, and learning disabilities. Pesticides also harm beneficial insects, such as bees and butterflies, and contaminate water bodies, posing risks to aquatic life and drinking water supplies.

Antibiotics

The widespread use of antibiotics in meat production, even in animals that are not sick, contributes to the public health crisis of antibiotic resistance. The regular use of these drugs in crowded and unsanitary conditions contributes to the rise of antibiotic-resistant bacteria, which can spread through air, water, and contaminated meat and farmworkers' clothing.

Climate Change

Climate change, influenced by agricultural greenhouse gas emissions, poses additional threats to air quality. Warmer temperatures and changing precipitation patterns can affect the blooming of plants and the emergence of pollinators like bees and butterflies, disrupting pollination. Climate change can also increase the frequency and intensity of wildfires, which release smoke that travels long distances and affects people's health, especially those with medical conditions or who spend significant time outdoors.

Climate change

Crop Yields

Crops such as corn, wheat, and rice are particularly vulnerable to the effects of climate change. A NASA study projects that by 2030, corn yields could decline by 24% due to increases in temperature, shifts in rainfall patterns, and elevated carbon dioxide concentrations. In contrast, wheat yields may increase by about 17%, as temperature rises expand its growing range.

The impact of temperature on crop yields depends on the optimal temperature for each crop's growth and reproduction. While warming may benefit certain crops or allow for the cultivation of different crop varieties, exceeding a crop's optimum temperature will inevitably lead to declining yields.

Additionally, higher carbon dioxide levels can stimulate plant growth, but they also reduce the nutritional value of most food crops. This poses a potential threat to human health, as elevated carbon dioxide levels have been associated with reduced protein and nitrogen content in plants.

Extreme Weather

The increasing frequency and intensity of extreme weather events, such as floods and droughts, pose significant challenges for farmers and threaten food security. Unpredictable changes in rainfall patterns can bring about drought, heatwaves, and flooding, severely impacting agricultural practices. For example, the Southwest region of the United States has been experiencing one of the most severe long-term droughts in the past 1,200 years, triggering reductions in crop yields.

Pests and Diseases

Livestock

Livestock are also at risk due to climate change, both directly from heat stress and indirectly from reduced food supply quality. Heatwaves can cause heat-related losses for agricultural producers, and heat stress can increase livestock's vulnerability to diseases, reduce fertility, and lower milk production. Droughts can further threaten livestock by reducing the availability of quality forage and feed supplies.

Fisheries

Soil

Unpredictable rainfall patterns can lead to heavy rains, causing soil erosion, nutrient loss, and the destruction of productive growing areas. This loss of topsoil can have devastating effects on agricultural productivity and sustainability.

Economic Impact

The agricultural and food sectors contribute significantly to the U.S. economy, with crops, livestock, and seafood generating over $300 billion annually. Climate change poses a threat to this economic contribution, as it affects the availability and accessibility of food and fiber, as well as energy prices and agricultural incomes.

Addressing Climate Change

To mitigate the impacts of climate change on agriculture, it is crucial to reduce greenhouse gas emissions and help farmers adapt to changing conditions. This includes implementing sustainable farming practices, improving soil health, and promoting climate-smart farming methods. By addressing these challenges, we can ensure food security and support the resilience of the agricultural sector in the face of a changing climate.

Soil erosion

The Midwest, a region home to some of America's most productive agricultural land, has been hit hard by erosion. In the last 150 years, it has lost nearly 58 billion tons of soil due to unsustainable agricultural practices. This has not only damaged the land but also reduced crop yields and impacted ecosystems.

The consequences of soil erosion are far-reaching. It reduces the quality and quantity of arable land, threatening food systems and livelihoods. It also affects water quality, as eroded soil, along with agrochemicals and pollutants, end up in rivers, streams, and lakes, contributing to harmful algal blooms and polluted waterways.

To combat soil erosion, farmers can adopt several strategies, including:

• Planting cover crops: Cover crops keep roots in the ground year-round, helping to stabilize the soil and maximize its water-holding capacity.
• Diversifying crop rotations: This helps build soil fertility and disrupt pest cycles.
• Adopting no-till or minimal tillage practices: Reducing mechanical disturbance to the soil minimizes erosion and improves water retention.
• Implementing rotational grazing: Moving livestock between pasture paddocks gives the land time to regrow and minimizes soil compaction and erosion.

Pesticides

The US Environmental Protection Agency (EPA) has been criticised for its failure to ban harmful pesticides, instead relying on voluntary cancellations by pesticide registrants. As a result, the US lags behind other major agricultural nations in banning harmful pesticides. For example, of the pesticides used in US agriculture in 2016, 322 million pounds were banned in the EU, 26 million pounds were banned in Brazil, and 40 million pounds were banned in China.

Frequently asked questions