Think of what it takes to feed, for example, the almost 9.5 billion animals raised for food each year in the United States. Or what goes into growing this country’s more than 90 million acres of corn, used mainly for livestock feed and ethanol production. The monumental quantities of fertilizers and pesticides that go into those operations (and all the manure that comes out) are just a few examples of the pollution associated with agriculture. Here’s your guide to making sense of the many and varied impacts of our farming practices.
What Is Agricultural Pollution?
Agricultural pollution is the contamination we release into the environment as a by-product of growing and raising livestock, food crops, animal feed, and biofuel crops.
The History of Industrial Agriculture
For most of our history, humans were hunters and gatherers. We fished in the ocean, hunted on land, and collected wild-growing fruits, seeds, and plants. Modern agriculture was born just 12,000 years ago, when we began to grow wild wheat and barley in the Fertile Crescent of the Middle East and Mediterranean basin, and to tend to the first rice paddies in swamps in China.
Agriculture transformed our way of life, giving us more consistent food supplies, allowing the growth of civilizations, and supporting an exponential boom in human population.
In the thousands of years since, agriculture has undergone tremendous horizontal growth, meaning that humans have set aside more and more land to grow food. In fact, the amount of land used for agriculture increased nearly sixfold in just a few centuries, between 1700 and 1980. In recent decades, we’ve also radically industrialized our methods and developed more resilient (and productive) crop species. It’s this growth in productivity—also called vertical expansion—that’s been credited with skyrocketing yields and reducing the cost of food. But many of the tools enabling this high-input, high-volume commodity agriculture have also contributed massive amounts of agricultural pollution.
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What Are the Causes of Agricultural Pollution?
Agricultural pollution has many different sources. Nitrogen-based fertilizers produce potent greenhouse gases and can overload waterways with dangerous pollutants; chemical pesticides with varying toxicological effects can contaminate our air and water or reside directly on our food. Sometimes we can clearly see (or even smell) the pollution and its source, like manure from a farm. Other times, the pollutant may be more indirect, like methane—another significant contributor to global warming—released through the digestive systems of cows. Agricultural pollution is generally divided into two categories: pollution that comes from raising animals, and pollution from growing crops including animal feed, human food, and biofuel crops.
Animal Agriculture Pollution
For most of history, meat was considered a luxury. But as disposable income has risen in the past century, so too has our demand for and consumption of meat, milk, and eggs. Between 1961 and 2014, meat consumption around the globe nearly doubled, from an average of 50 pounds per person each year to 95 pounds. Americans consume much higher amounts: roughly 133 pounds of red meat and poultry per person annually, according to the U.S. Department of Agriculture (USDA). Here’s why feeding, slaughtering, and transporting billions of animals each year in businesses officially known as concentrated animal feeding operations, or CAFOs, is environmentally costly.
Livestock Water Pollution
Cows, pigs, chickens, and turkeys do what all other animals do: poop. In 2012 livestock and poultry grown in the largest CAFOs in the United States produced 369 million tons of manure, or almost 13 times the waste of the entire U.S. population, according to an analysis of USDA figures done by Food & Water Watch. All of that farm animal waste needs to go somewhere. But CAFOs don’t treat animal waste in the same way we treat human waste, by sending it to a wastewater treatment plant via a municipal sewer system.
Instead, this waste is disposed of by spreading it, untreated, on land. Operators are supposed to apply only the amount that crops can use, but in reality, there is often too much manure—so it is applied beyond the ground’s natural absorption rate, leading to runoff into water sources.
To make matters worse, before it is applied it to land, the manure usually sits on-site in vast manure lagoons that can grow to the size of a football field. The lagoons contain a toxic stew of antibiotics residue, chemicals, and bacteria decomposing the waste, a medley that can take on a sickly hue. They’re often unlined and are prone to overflows, leaks, and spills, often causing the contents to leach into the soil and groundwater.
(Big storms, like Hurricane Florence, which devastated North Carolina’s coast, make wide-scale spills and contamination more likely.) And once this mixture, chock-full of phosphorus and nitrogen, gets into a water body, it causes a cascading reaction called eutrophication, or the destructive overgrowth of algae.
Similar problems arise with poultry waste, which is mostly dry litter, a combination of the birds’ bedding materials (such as shavings), their feces, and loose feathers, which is stored in exposed, giant mounds. Because chicken manure contains a higher percentage of phosphorus than other animal manure, it’s also prone to harming waterways with phosphorus runoff.
Livestock Air Pollution
Livestock and their manure pollute our air, too: Manure management alone accounts for 14 percent of all agricultural greenhouse gas emissions in the U.S. Manure emits ammonia, which combines with other air pollutants, like nitrogen oxides and sulfates, to create tiny (and deadly) solid particles. We humans then inhale these particles, which can cause heart and lung disease and are said to account fort least 3.3 million deaths each year globally. Additionally, hog waste in particular has been called out by people living near CAFOs for its foul smell.
Antibiotic resistance
The widespread use of antibiotics in meat production in animals that are not sick is contributing to the public health crisis of antibiotic resistance. Two-thirds of antibiotics important to human medicine in the U.S. are sold for use in livestock, not people. The regular use of these drugs in the food and water of farm animals to (poorly) help them survive the often crowded, unsanitary, and stressful conditions on CAFOs contributes to the rise and proliferation of antibiotic-resistant bacteria. These bacteria can then spread from CAFOs via air and water, including water used to irrigate crops, and can end up in animal waste used to fertilize crops. Contaminated meat and farmworkers’ clothing and shoes can also spread these antibiotic-resistant bacteria into our communities. Resistant bacteria can even “teach” other bacteria resistance, and this process can take place anywhere bacteria are found, including in our homes and guts. The exposure of workers and farm-adjacent communities is particularly high.
Antibiotic-resistant bacteria are among the gravest health threats we face today. It’s estimated that up to 162,000 people die per year in the United States as a result of antibiotic-resistant infections—that’s more people than are killed in all types of accidents, and more than double the annual deaths from opioid overdoses—making it the third-leading cause of death in the United States, behind heart disease and cancer. And public health officials warn that the crisis will only get worse if we continue misusing and overusing these drugs.
Crop Agriculture Pollution
Industrial agriculture permits us to overproduce grains, fruits, and vegetables year-round. (This includes the feed for our livestock, which takes up one-third of the planet’s arable land.) Unfortunately, this productivity comes with a price.
Nitrogen-Based Fertilizers
Nitrogen-based fertilizer has been a major factor driving the industrialization of agriculture in the past century, allowing high yields even on overtaxed land. But fertilizer has serious downsides for our water supplies and climate.
Nitrogen is a primary building block for plants, and healthy soil uses nitrogen efficiently. But under mono-cropping, soil becomes depleted of nutrients, requiring farmers to try to regenerate the soil through practices like planting cover crops or to move on to more arable land. The invention of synthetic nitrogen in the 20th century (and then, quickly, its skyrocketing use) removed this limiting factor and allowed for a boom in chemical-intensive, industrial farming practices. A big boom, indeed: In 1964 U.S. farmers applied about 4.3 million tons of nitrogen to their crops each year. By 2007, American farmers were dropping 5.7 million tons of nitrogen fertilizer just on corn.
Synthetic forms of nitrogen are different in some key ways from the nitrogen occurring naturally in our atmosphere. Naturally occurring nitrogen, known as N2, is more difficult for plants to use, requiring specific bacteria to help make it bioavailable. But synthetic fertilizer is made up of a nitrogen- and hydrogen-based ammonia (NH3) that can be used by plants directly. Transforming N2 into NH3 through chemical processes is resource intensive, and this form of nitrogen is also more prone to reacting with other things in the environment, not just plants.
In addition, when excess nitrogen makes its way into the atmosphere (as it often does when fertilizer is applied at high volumes), it can become nitrous oxide, a potent greenhouse gas, or nitrogen oxide, which contributes to ground-level smog.
Nutrient Runoff
The climate impacts alone are enough of a reason to wean ourselves off synthetic fertilizers, but these chemicals have another major environmental downside: nutrient runoff. Runoff occurs when nutrient-rich material like fertilizer or manure, chock-full of nitrogen and phosphorous, makes its way into nearby rivers, oceans, and lakes, wreaking havoc on our freshwater and marine ecosystems. Heavy rains can trigger runoff, as can soil erosion. Here’s how it works: An excess of nutrients in a water system causes an overgrowth of algae. As algae then die off, aerobic bacteria decompose them, consuming oxygen in the process and starving other marine life. Algae overgrowth can also block sunlight, disrupting the ecosystem below that relies on the sun for energy.
The results can be dramatic: Nutrient runoff decimated the once-thriving Chesapeake Bay, killing off large numbers of the estuary’s fish and shellfish. Each summer, high levels of manure and fertilizer from the Mississippi River make their way into the Gulf of Mexico, causing a recurring “dead zone” thousands of kilometers wide. And in recent years, persistent algal blooms, like red tides that produce toxins, have devastated coastal communities in Florida, staying long past their typical seasons and killing marine life en masse.
Pollution via runoff (known as agricultural nonpoint source pollution) is the leading source of harm to water quality for surveyed rivers and streams, the third-largest for lakes, and the second-largest for wetlands. But stemming it is in our control. Farmers can reduce nutrient runoff significantly through improved soil health practices like planting cover crops, water quality practices like planting streamside buffer crops, and by following fertilizer best practices.
Chemical Pesticides
Farmers routinely use pesticides—herbicides, insecticides, rodenticides, and fungicides—to keep away any unwanted weeds, insects, rodents, and fungi. But these toxic chemicals have serious side-effects. These chemicals can cause many chronic diseases such as endocrine (hormone) and neurological disorders and cancer. Because of their still-developing bodies, children are especially vulnerable to exposure and face the worst health impacts. Some of the most toxic pesticides, like chlorpyrifos, have been linked to developmental delays, lower IQs, and learning disabilities.
Since becoming widespread in the past century, pesticides are routinely detected in 90 percent of our streams and rivers. And we Americans now have an average of 43 different pesticides in our blood, circulating to all the organs and systems in our bodies where they can cause adverse health effects. Farmworkers are particularly susceptible to exposure, coming into contact with pesticides when spraying fields, inhaling pesticide “drift,” and exposing their families via contamination on their clothing. Rural residents in general may be exposed to contaminated water, air, and food.
Aside from being bad for human health, pesticides are also bad for pollinators. The populations of insects like the iconic monarch butterfly and native bees like the rusty patched bumble bee have plummeted in recent decades, due in part to these ubiquitous toxins. But under pressure from pesticide manufacturers and industry lobbyists, governments are often slow to ban or even limit these products’ use. Instead they choose to pass off the risk to consumers, rural communities, and agricultural workers.
The Carbon Footprint of Meat
If we’re going to stave off the worst effects of climate change, we must tackle the oversize carbon pollution footprint of meat. An NRDC analysis showed that in 2014, beef alone was responsible for 34 percent of all food-related greenhouse gas emissions in the United States.
Enteric Fermentation
It’s a fancy name for a not-so-fancy phenomenon: cow burps and gas. Enteric fermentation is part of the digestive process of ruminant animals like cows, sheep, and goats. Gut microbes decompose and ferment fibrous food, like grass, producing methane , which has about 30 times the planet-warming power of carbon. Those emissions add up: Enteric fermentation is the largest source of greenhouse gas emissions in agricultural production, contributing roughly 164 million metric tons of carbon dioxide-equivalent emissions.
Caloric Inefficiency
The caloric inefficiency of beef drives its high carbon price tag. It takes much more food, water, and land to produce 1,000 calories of beef than it does to produce 1,000 calories of grain. And that livestock feed is grown using pesticides as well as fertilizers, both of which are made with fossil fuels. All these factors add up to make beef 34 times more damaging to our climate than legumes like beans and lentils, by weight. (Additionally, composting cow manure releases more methane and nitrous oxide into the air.)
Land-Use Changes
Shifting land use to raise more livestock delivers a one-two punch to the environment. Not only is animal agriculture resource intensive and polluting, but clearing land that previously held forest and other vegetation means releasing stored carbon into the environment and destroying diverse ecosystems. Cattle ranching, for example, is devastating the Amazon, accounting for nearly 80 percent of the deforestation in every Amazon country. Protecting dense carbon sinks like this rainforest is critical to reducing our carbon emissions and fighting climate change.
Reducing Industrial Agriculture Pollution
By 2050 the global population will hit nearly 10 billion. Can we feed all these people without overtaxing our natural resources or destroying the planet in the process? It’s possible, but we’ll have to make significant shifts in the way we grow, raise, and eat food. Here are some steps we can all take; even small changes can be very meaningful:
- Eat more plant-based foods.
- Minimize consumption of red meat, our most carbon-intensive food.
- When choosing among restaurants, consider their records on antibiotic use in their meat supply (check out NRDC’s restaurant scorecards).
- When you buy animal products, buy products from animals raised without the regular use of medically important antibiotics. Look for any of these labels: USDA Certified Organic, USDA Process Verified No Antibiotics Ever, Global Animal Partnership (GAP), American Grassfed, Certified Humane, and Animal Welfare Approved; all of these indicate third-party certification. Labels saying “No Antibiotics Administered” or “No Antibiotics Added” or “Raised Without Antibiotics” also communicate the producer’s commitment to responsible use but are not verified by an outside group.
- When possible, opt for organic, especially with the fruits and vegetables known to carry the highest amounts of pesticides like strawberries, spinach, and apples.
- Plan meals in advance and serve small portions to prevent food waste, a significant contributor of greenhouse gases. Nearly 40 percent of food in America goes uneaten, a remarkable waste of resources.
- Don’t trash food scraps. Bring leftovers home from restaurants, and freeze what you won’t eat right away. Any vegetable odds and ends can go into a home or community compost.
- Support local farmers practicing more sustainable growing methods by buying from a neighborhood market. Get to know the farmers, ask about their soil and livestock management practices, and let them know you appreciate their efforts.
- Buy “ugly” produce. Food waste happens at every level of the supply chain—including on the farm itself. Edible produce is frequently left unharvested because there’s simply no market for it. (Think tiny apples, misshapen carrots, or too much of any one crop.) Though farm-level food waste is the least destructive kind (as resources have not been expended on packing and shipping), we can still do our part by telling local farmers directly that we’re willing to purchase imperfect produce, which could help shape future harvesting practices.
- Buy in bulk to limit your packaging consumption.
- Start a “plant forward” initiative in your community and build meals around your favorite vegetables instead of meats.
- Grow your own food, without chemicals. You’ll have a better understanding of regenerative farming and will be able to reward yourself with organic, in-season produce.
- Pay attention to farm policy and be vocal in your support of pro-environment practices. While the solutions for reducing nutrient pollution are plentiful, our system of food and farm policies is not set up to give farmers incentives to use the best practices. In fact, farm policy is often a barrier to practices that regenerate the land. You can make a difference by reading up on farm policy in the news and petitioning your government representatives to do the following: support conservation and climate-friendly farming, ban harmful pesticides, reduce the use of medically important antibiotics in meat and poultry production, improve the crop insurance program, invest in research to help farmers transition away from chemical agriculture to more ecological practices like organic and regenerative farming, and enforce stricter rules on the disposal of manure from CAFOs.
