Agricultural Pollution: Understanding Its Root Causes

Agriculture has a profound effect on the planet. Modern agricultural methods are responsible for a significant amount of pollution, which comes in a variety of types and has a multitude of causes. The main causes of agricultural pollution are air pollution, soil pollution, and water pollution. Air pollution is caused by the rampant use of pesticides and fertilizers, as well as livestock operations, which emit ammonia, nitrogen oxides, and methane. Soil pollution is caused by the overuse of pesticides and fertilizers, which reduce soil quality and fertility. Water pollution is caused by agricultural runoff, which includes excess nutrients, chemicals, and sediments that contaminate rivers, lakes, and oceans.

Livestock and manure

Livestock and their manure are major contributors to agricultural pollution, particularly air pollution. According to the EPA, manure management alone 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 like nitrogen oxides and sulfates to form tiny, yet deadly, solid particles. These particles are inhaled by humans and are known to cause heart and lung diseases, contributing to millions of deaths worldwide annually.

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 a rise in emissions and other issues related to manure collection, storage, treatment, and utilization if proper manure management practices are not implemented. Poor manure management practices are already prevalent on many farms worldwide, as farmers lack awareness of the value of livestock manure as a fertilizer and fuel. Improper disposal methods, such as piling, slurrying, or lagoon storage, can lead to significant methane emissions, environmental degradation, negative health impacts, and the loss of valuable nutrients that could benefit soil health.

Furthermore, the feeding, slaughtering, and transportation of billions of animals annually in concentrated animal feeding operations (CAFOs) have environmental consequences. The large quantities of manure produced by these operations contribute to water pollution when they infiltrate surface and groundwater systems through runoff or seepage. Hog waste, in particular, has been criticized for its offensive odour by people residing near CAFOs. Additionally, the widespread use of antibiotics in meat production, even in healthy animals, is exacerbating the public health crisis of antibiotic resistance.

The impact of livestock and manure on water pollution is significant. Animal agriculture manure is a primary source of nitrogen and phosphorus in surface and groundwater. Manure runoff from croplands, pastures, and CAFOs can contaminate water bodies, affecting their quality and the health of aquatic ecosystems. This contamination can lead to eutrophication, encouraging the growth of certain species, such as algae, while hindering the survival of others.

To address these issues, organizations like the Climate and Clean Air Coalition are working to improve manure management practices. They advocate for integrated practices that encompass all aspects of manure management, from excretion to collection, storage, and utilization. By raising awareness, providing resources, and facilitating knowledge exchange, they aim to reduce short-lived climate pollutant emissions and mitigate the environmental and health impacts associated with poor manure management.

Pesticides and fertilisers

Soil pollution caused by pesticides and fertilisers can have detrimental effects on soil quality, gradually reducing its fertility over time. This, in turn, negatively impacts the biodiversity of the soil, decreasing the number of life forms that can thrive in it and making it less suitable for future cultivation.

Water pollution is another significant consequence of excessive pesticide and fertiliser use. Agricultural runoff sweeps excess chemicals, including pesticides and fertilisers, into nearby rivers, streams, lakes, and coastal areas. This leads to an abundance of certain substances, such as ammonia, nitrates, and phosphates, which can cause eutrophication. Eutrophication is a process where algal blooms block sunlight and consume more oxygen than other organisms, making it challenging for them to survive. Additionally, pesticides that reach water bodies can contaminate drinking water supplies and pose risks to aquatic life and fish-eating wildlife.

Air pollution is also a concern with pesticide and fertiliser use. These substances can become airborne, especially in strong winds, before they reach their intended targets or evaporate over time. Once in the air, they contribute to air pollution, affecting the quality of the air in the vicinity of agricultural areas and potentially infiltrating distant environments.

Furthermore, pesticides like neonics are harmful to pollinators and have contributed to the decline in populations of iconic species such as the monarch butterfly and native bees. The toxic chemicals in pesticides can also cause chronic diseases in humans, including endocrine (hormone) and neurological disorders.

Soil pollution

There are several causes of soil pollution, many of which are linked to agricultural practices. One of the primary causes is the excessive use of pesticides and fertilizers. The use of pesticides and herbicides in agriculture has increased considerably over the past few decades, with around 300 million kilograms of pesticides used annually in the US as of 2010. While these chemicals help control pests and enhance crop production, they can also contaminate the soil. When pesticides are applied to crops, they can become airborne and affect the surrounding environment, including the soil. Additionally, during heavy rain or storms, pesticides and fertilizers can be washed away and seep into nearby bodies of water, contaminating them and causing water pollution. This runoff can also lead to soil erosion, further exacerbating the problem.

Another cause of soil pollution is the use of livestock manure as fertilizer. Manure contains high levels of phosphorus and nitrogen, which can lead to nutrient runoff and water pollution if not properly managed. Manure also emits ammonia, which combines with other air pollutants to form harmful solid particles that can be inhaled by humans and cause health issues. Furthermore, the use of antibiotics in livestock farming contributes to the development of antimicrobial-resistant bacteria, which poses a significant threat to public health.

The effects of soil pollution are far-reaching. It reduces soil biodiversity, weakens soil structure, and makes the soil more susceptible to erosion. Additionally, soil pollution can lead to the acidification of the soil, affecting the bioavailability of contaminants and causing metal toxicities in plants. Nitrates from excessive fertilizer use can leach into groundwater, and nitrous oxide, a major greenhouse gas, is released from overly fertilized soils, contributing to climate change.

Water pollution

Agricultural runoff is the leading cause of water quality impacts to rivers and streams, the third-largest for lakes, and the second-largest for wetlands. The National Water Quality Assessment in the US found that about a half million tons of pesticides, 12 million tons of nitrogen, and 4 million tons of phosphorus fertilizer are applied annually to crops in the country. Soil erosion, nutrient loss, bacteria from livestock manure, and pesticides are the primary stressors to water quality. These contaminants can be moved into local streams, rivers, and groundwater through runoff, infiltration, and irrigation return flows. Rainfall and snowmelt are the primary transporters of these pollutants to surface waters, but other factors, such as cattle loafing in stream corridors, can also contribute.

Nutrient management practices can help minimize runoff. For example, using drip irrigation instead of furrow irrigation allows better control of the amounts of pesticides and nutrients added to irrigation water. Storing livestock manure in lagoons, covered stockpiles, or protected upland areas can also minimize runoff risks. Even subsurface cropland drainage systems can be managed to reduce the export of pollutants to streams.

Excess chemicals from industrialized agriculture can be swept into rivers, lakes, streams, and coastal waters, leading to an abundance of certain substances such as ammonia, nitrates, and phosphate. This encourages the rapid proliferation of certain species, such as algae, which can block out sunlight and consume oxygen, making it harder for other flora and fauna beneath the water surface to survive. This process, known as eutrophication, can also affect recreational uses of local streams, downstream reservoirs, and estuaries.

Agricultural operations can also contaminate groundwater, degrading sources of drinking water. Pesticides that are transported to streams can pose risks to aquatic life, fish-eating wildlife, and drinking water supplies. Bacteria and nutrients from livestock and poultry manure can cause beach and shellfish bed closures and affect drinking water supplies.

Air pollution

Agriculture accounts for about 11% of US emissions, according to the EPA, and of that, 36% comes from raising, feeding, and managing livestock. The air pollution caused by agriculture through land use changes and animal agriculture practices has a significant impact on climate change.

One of the main causes of air pollution in agriculture is the use of pesticides and fertilisers. The rampant use of pesticides and fertilisers can be devastating for soil quality, and they can also create air pollution. In strong winds, they can become airborne before they even reach their intended target, or they can evaporate into the air over time. Pesticides like neonics are not only bad for human health but also for pollinators, and their toxic chemicals can cause chronic diseases such as endocrine (hormone) and neurological disorders.

Another significant contributor to agricultural air pollution is livestock and their manure. According to the EPA, manure management alone accounts for 12% of all agricultural greenhouse gas emissions in the United States and 14.5% globally, according to 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 to human health.

Furthermore, the use of machinery, vehicles, and electrical equipment in modern farming practices produces various greenhouse gases, airborne chemicals, and other pollutants that negatively impact air quality.

To address these issues, farmers can adopt nutrient management techniques, such as applying nutrients (fertiliser and manure) in the right amounts, at the right time of year, and with the correct methods and placement. Implementing conservation tillage by reducing the frequency and intensity of tilling can also help improve soil health and reduce nutrient losses to the air.

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