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How does animal agriculture pollute water?

Photo: Jo-Anne McArthur / We Animals Media

We depend on clean water every day of our lives, to drink, cook, and wash. Yet despite our dependence on a steady supply of clean water for both our health and our convenience, we allow it to be compromised via pollution. One of the largest drivers of water pollution is agriculture, and specifically animal agriculture, due to the overwhelming amount of waste created as a byproduct of the production of animal-derived food. This contamination has serious consequences for the health of humans, the environment, and wild animals.

What is agricultural pollution?

Agricultural pollution constitutes the contamination of water, air, and other resources caused by the processes we use to produce food. Animal agriculture ranks within the top three industries causing the most severe environmental problems facing us today at every scale one considers, from local effects to global ramifications, and that includes water degradation.1 Growing crops to be fed to animals is a major contributor to water pollution due to the sheer size of the industry, the many different chemicals employed, and the enormous amount of fresh water it uses. Factory farms, in which animals are packed together on small areas of land by the thousands or tens of thousands, play a large role in polluting water, as the waste from these animals makes it into waterways, groundwater, and open ocean.

Agriculture also is a major contributor to anthropogenic greenhouse gas emissions (GHGs). Food production as a whole accounts for about a quarter of all human-caused GHGs. Of this total, livestock and fisheries (including production of feed and land use) account for 53 percent of agricultural GHGs.

How does animal agriculture pollute water?

Industrial animal agriculture

The primary way that industrial animal farms contribute to water pollution is through waste storage. Factory farms house thousands or tens of thousands of animals in a relatively small area. All of these animals produce waste. The waste is high in nutrients, including nitrates, which have now become the most common contaminant in the world’s groundwater aquifers. In recent years, veterinary medicines have also made their way into our drinking water due to their heavy use within animal agriculture.2

Industrial crop production

Of the calories from crops produced around the world only 55 percent go directly to humans for consumption. About 36 percent of calories from crops are fed to animals raised for meat. Crop production has a massive impact on the water supply due to the heavy use of pesticides and fertilizers that is standard practice within the modern food production industry. These chemicals make their way into waterways when soil is washed off fields.

How does animal agriculture affect water?

Billions of animals are raised for food around the world. With so many individuals being born, living, and then being killed in a constant cycle that is kept as short as possible to maximize profits, it comes as no surprise that the impact of animal agriculture on water is considerable. Factory farms’ contributions to water pollution stem from the animals and their waste, the operations of the farms, and the production of food for the animals. The pollution caused by these facilities has far-reaching impacts, contributing to disease outbreaks, driving algal blooms, and negatively impacting economies that depend on clean water.

Algal blooms, dead zones, and acidification

Animal agriculture has a major impact on surface water by encouraging the formation of algal blooms and dead zones. Animal agriculture produces large amounts of waste, which is rich in phosphorus and nitrogen. When these nutrients make their way into the water, they increase the likelihood and severity of algal blooms. When the algae of such a bloom eventually die, their decomposition takes with it the oxygen in the water, which results in a mass die-off of the plant and animal species in the impacted area. In addition to the loss of life associated with algal blooms, they can be devastating for local economies and individuals that depend on the water for their incomes.

Heavy metal contamination

Agriculture contributes to the presence of heavy metals in water. Though there are many industrial sources of such contamination, fertilizer, pesticides, manure, and irrigation play significant roles. Heavy metal exposure has been linked to a number of health conditions including weakened bones, liver and lung damage, and cancer.

Nitrates and other contaminants in drinking water

Animal agriculture has been repeatedly recognized as one of the main sources of nitrates in water supplies. The presence of nitrates, even in small amounts, can cause serious medical conditions such as birth defects, thyroid disease, and colorectal cancer.3 Agriculture also contaminates drinking water with other chemicals from fertilizers and pesticides, notably phosphorus.

Pathogen contamination and disease outbreaks

A variety of zoonotic diseases can be spread from animals being raised for food to humans and other animal populations via water. One of the major ways that such diseases are introduced to water is through the fecal matter of an infected animal. Diseases that can be transmitted this way include E. coli and Cryptosporidium.4

How does water pollution affect animals?

Wild animals are seriously impacted by water pollution. Whether they spend their lives in the air, in the water, or on land, wild animals endure some of the worst impacts of polluted water systems.


Many birds depend on waterways for their food supply. When the water becomes polluted, the native grasses and populations of animals on which birds prey can die off, leading to birds not having enough food to survive. Cyanobacteria that occur as part of algal blooms have also been linked to die-offs of birds around the world.5

Marine life

Marine species suffer from water pollution regardless of its cause, but one particularly significant contributor to pollution is aquaculture, or fish farming. Alongside pesticides, fish feces, and antibiotics, one of the most threatening contaminants from aquaculture are the farmed fish themselves. Repeatedly, farmed fish have escaped from enclosures in which they are normally kept, despite every precaution taken, and wreaked havoc on native populations.

Land animals

Cyanobacteria poisoning can affect land animals as well as birds.6 The build-up of any toxic elements in waterways can ultimately impact on animals whose food webs include marine organisms, and the collapse of aquatic ecosystems can have unpredictable effects for land-dwelling animals.

What are the effects of water pollution on agriculture?

Agriculture may be one of the industries most responsible for water pollution, but water pollution in turn also has significant impacts on the agriculture industry. Using polluted water for food production can contaminate the crops and animals raised for food with bacteria or toxins and ultimately pass problems on to farm workers and consumers.

How to prevent water pollution from agriculture

There are a number of tactics that help reduce water pollution from agriculture. These include creating management plans for soil, animal waste, and animals themselves that take water systems into account. While following such suggestions may reduce some of the water pollution from agriculture, much greater change is needed in order to restore water sources and maintain them for the future.

Moving away from large-scale animal agriculture would free up the 41 percent of global agricultural water currently used to grow the food consumed by farmed animals.7 At the individual level, we can support this transition by reducing, and even eliminating, our consumption of not just meat but all animal products, including dairy and eggs.

Water usage in agriculture: Statistics

  • Agriculture accounts for about 70 percent of all water use around the world.
  • Producing just one kilogram of beef requires more than 2,700 liters of water, while one kilogram of shrimp requires more than 3,500 liters of water.
  • As of 2015, farms in the United States produced an estimated 500 million tons of manure a year. Manure often seeps out of its storage facilities and makes its way into waterways.
  • In 2007, the animal manure in Iowa produced an estimated 398 million kilograms of nitrogen and 144 million kilograms of phosphorus.
  • Most of the water used by animal agriculture for drinking and servicing returns to the environment in the form of manure, slurry, and wastewater.


Water pollution is a serious problem not only because it compromises the integrity of the environment, but also because it causes health problems, and potentially death, for a wide range of animals, while also allowing the spread of zoonotic disease. In order to prevent the further degradation of water systems, we must change the way that we eat, by focusing more on eating, and producing, plant-based foods instead of continuing to farm animals en masse on factory farms.



Javier Mateo-Sagasta, Sara Marjani Zadeh, and Hugh Turral, “Water Pollution from Agriculture: A Global Review, Executive Summary” (FAO, 2017),


Mateo-Sagasta, Zadeh, and Turral, “Water Pollution from Agriculture,”


Mary H. Ward et al., “Drinking Water Nitrate and Human Health: An Updated Review,” International Journal of Environmental Research and Public Health 15, no. 7 (July, 2018),


Meg Jenkins, Sabrina Ahmed, and Amber N. Barnes, “A Systematic Review of Waterborne and Water-Related Disease in Animal Populations of Florida from 1999–2019,” PLoS One 16, no. 7 (July, 2021),


Alexandra K. Ash and Stuart Patterson, “Reporting of Freshwater Cyanobacterial Poisoning in Terrestrial Wildlife: A Systematic Map,” Animals 12, no. 18 (2022),


Ash and Patterson, “Reporting of Freshwater Cyanobacterial Poisoning in Terrestrial Wildlife,”


Jens Heinke et al., “Water Use in Global Livestock Production—Opportunities and Constraints for Increasing Water Productivity,” Water Resources Research 56, no. 12 (November, 2020),