Agriculture's Pollution Problem: How Bad Is It?

Agriculture is a major source of pollution, contributing significantly to global greenhouse gas emissions. The production of food, including both plant-based and animal-based sources, is responsible for around 25-30% of global emissions, with this figure rising to one-third when non-food agricultural products such as cotton, wool, and leather are included. Animal-based food production is particularly harmful, with meat diets producing 59% more greenhouse gases than vegetarian ones. Beef is the largest contributor, generating 25% of total food emissions, while rice is the most polluting plant-based food, responsible for 12% of emissions from the food sector. Agriculture also causes pollution through fertilizer runoff, which has decimated ecosystems in areas such as the Chesapeake Bay and the Gulf of Mexico.

Livestock and manure

Livestock farming has become one of the biggest drivers of climate change and environmental destruction. The sector's contribution to deforestation, habitat loss, and pollution exacerbates climate change. The demand for livestock products is expected to increase due to population growth and changes in dietary preferences. As the demand for meat has increased, so has the number of animals raised for food each year. This has resulted in a significant increase in manure, which has become a major challenge for farmers to manage.

Livestock produce around 450 million tons of manure annually. Common management methods include storing manure in large piles, landfills, or lagoons, or using it as untreated fertilizer on cropland. These methods result in the release of methane and nitrous oxide, which are powerful greenhouse gases. Manure also contains antibiotics and hormones, which can contaminate water sources. When manure is applied to fields, it can run off into nearby waterways, polluting drinking water and causing harmful algal blooms that release toxins harmful to humans and animals.

Poor manure management practices are common on farms due to a lack of awareness about the value of livestock manure as a fertilizer and fuel. Manure is often disposed of in ways that lead to significant emissions of methane and other short-lived climate pollutants. However, proper manure management can prevent these emissions and provide added benefits for farmers through cost savings and additional income.

The Environmental Protection Agency (EPA) estimates that manure management alone accounts for 12% of all agricultural greenhouse gas emissions in the United States. Globally, it accounts for 14.5%. To address this issue, the Climate and Clean Air Coalition is working to improve manure management practices by providing information, expertise, and resources to farmers. They promote integrated practices that encompass all activities associated with the management of dung and urine, from excretion to utilization.

By implementing better manure management practices, such as proper storage and treatment, farmers can reduce emissions and improve environmental and health outcomes. Additionally, adopting agroecology practices, such as crop rotation and increasing crop and animal diversity, can help reduce the agricultural sector's impact on the environment.

Fertilizer use

Fertilizers are essential for crop growth, but their overuse and improper management can have detrimental effects on the environment and human health. Nitrogen and phosphorus are the two primary fertilizers that farmers apply to their fields. While these fertilizers have significantly increased agricultural productivity, allowing for greater food production and the preservation of ecosystems, they can also act as pollutants when overapplied. Research indicates that nearly two-thirds of the nitrogen used on crops becomes a pollutant, and more than half of the applied phosphorus has the same effect.

Excess nitrogen and phosphorus from fertilizers can be washed from farm fields into nearby waterways during rain and snowmelt or leach into the groundwater over time. This nutrient runoff leads to eutrophication, a process where the overload of nutrients causes uncontrolled algae growth, depleting the water of oxygen and resulting in hypoxic or "dead zones" where aquatic life cannot survive. These dead zones can be found in lakes, rivers, wetlands, estuaries, and coastal areas, negatively impacting aquatic ecosystems and water quality.

The use of synthetic fertilizers in agriculture also contributes to air pollution. The manufacturing process releases soot, dust particles, and polluting gases such as sulphur oxide (SOx), ammonia (NH3), and nitrogenous compounds like nitric oxide (NO) and nitrogen dioxide (NO2). These emissions have severe consequences for both the environment and human health. Nitrogen oxides, for example, have a 300 times more potent greenhouse effect than carbon dioxide, contributing to climate change. Additionally, the inhalation of these gases can lead to respiratory diseases, circulatory system disorders, and organ damage in humans.

The impact of fertilizer use on the environment and human health is evident in regions with intensive agriculture, such as Punjab, India. In these areas, the declining health of farmers and their families has been linked to increased fertilizer and pesticide use. As the soil's fertility decreases, higher amounts of synthetic fertilizers are required, leading to greater air pollution and adverse health effects.

To mitigate the negative consequences of fertilizer use, farmers can adopt improved nutrient management practices. This includes applying the right amount of nutrients at the appropriate time of year, using suitable methods and placement. Implementing conservation drainage practices, such as subsurface tile drainage, is also crucial to managing water movement and reducing nutrient loads while maintaining adequate drainage for crop production. Additionally, ensuring year-round ground cover by planting cover crops or perennial species can prevent soil erosion and reduce nutrient loss from fields.

Deforestation

Forests are biologically diverse and ecologically important, covering almost a third of the Earth's surface and providing a home to hundreds of thousands of species. Unfortunately, forests are under threat, and deforestation rates are increasing. Agriculture is the primary cause of deforestation, with other significant contributors being poorly planned infrastructure, logging, and livestock grazing.

The leading cause of deforestation is the conversion of forest land to agricultural use. This can be for crop-growing or livestock grazing, with the majority of deforested land being used for animal agriculture. Between 2010 and 2018, about 49% of deforested land was used for crops, while 38% was used for livestock. However, if we consider that many crops are grown to feed livestock, the share of deforested land used for animal agriculture rises to 77%.

The beef industry is the single biggest driver of deforestation, with cattle farming accounting for 80% of all deforested land in the Amazon and 41% of all tropical deforestation worldwide. In addition, agricultural products such as soy and palm oil are used in an ever-increasing number of products, from animal feed to biofuels. The demand for these products has created incentives to convert forests to farmland and ranch land.

Halting deforestation requires addressing the underlying and indirect roles of agriculture. While sector-specific initiatives to combat deforestation are invaluable, strengthening forest and land-use governance in producer countries is essential. Protecting and restoring forests, as well as revamping the global food system through dietary changes, are key solutions to the escalating biodiversity and climate crises.

Meat vs plant-based diets

Agriculture has a profound impact on the planet, and food systems account for around 25-30% of global greenhouse gas emissions. When non-food agricultural products are included, this figure rises to one-third.

The environmental impact of meat-based diets compared to plant-based diets is a significant aspect of the broader issue of agricultural pollution. Meat diets produce 59% more greenhouse gases than vegetarian ones, and beef is 34 times more damaging to the climate than legumes, according to the National Institutes of Health. This is due to the greater amount of food, water, and land needed to produce meat, especially beef, compared to fruits, vegetables, and legumes. Additionally, the use of pesticides and fertilizers, which are made with fossil fuels, in livestock feed contributes to pollution.

The environmental impact of meat-based meals is, on average, 14 times higher than that of vegetarian meals, and 42 times higher than vegan meals. Replacing animal-based ingredients with plant-based alternatives in recipes is a simple way to significantly reduce the environmental impact of meals. This is because animal agriculture is resource-intensive and polluting, and clearing land that previously held forests and other vegetation releases stored carbon and destroys diverse ecosystems.

Livestock and their manure also contribute to air pollution, with manure management accounting for 12% of all agricultural greenhouse gas emissions in the United States, and 14.5% globally. Pollution via runoff, or agricultural nonpoint source pollution, is a leading source of harm to water quality for rivers, streams, lakes, wetlands, and oceans. For example, high levels of manure and fertilizer from the Mississippi River cause a recurring "dead zone" in the Gulf of Mexico each summer, and similar problems arise with poultry waste.

In terms of health, the concept of plant-based diets has gained popularity due to its purported benefits for both human health and the environment. Vegetarians and vegans typically have lower body mass indexes, serum low-density lipoprotein (LDL) cholesterol, and blood pressure than regular meat-eaters. They also have a lower risk of certain diseases, such as ischaemic heart disease, diabetes, and diverticular disease. However, they may also face a higher risk of fractures and a lack of certain micronutrients, such as vitamin B12, vitamin D, calcium, and iodine.

Fossil fuels

The specific breakdown of fossil fuel emissions by sector varies from source to source. The transportation sector is the largest source of direct greenhouse gas emissions and the second-largest source when indirect emissions from electricity end-use are included. The commercial and residential sector emissions increase substantially when indirect emissions from electricity end-use are included, as buildings use 75% of the electricity generated in the US. The industrial sector, including emissions from burning fossil fuels on-site at facilities for energy, accounts for 24% of global greenhouse gas emissions.

Fossil fuel emissions come primarily from burning coal, natural gas, and petroleum for energy use. The amount of CO2 produced depends on the carbon content of the fuel and the amount of heat produced depends on the carbon and hydrogen content. Natural gas, which is mostly methane, has a high hydrogen content, so burning it produces less CO2 for the same amount of energy produced compared to other fossil fuels.

The economic growth, weather patterns, energy prices, and government policies all influence the amount of energy consumed and the sources or types of energy used. The continued rise in emissions from the burning of fossil fuels is impeding progress to limit global warming.

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