We Need to Talk about Animal Ag

Meat is a contentious subject in the United States. Questions like whether or not it’s a) healthy for humans to eat meat, b) ethical to kill animals for meat, or c) ethical to confine animals to raise them for meat, etc., can be discussed by well-informed people in good faith, but often (usually?) they’re not. For the time being, the discussion revolves around contradictory beliefs that cannot be reconciled.

I won’t be wading into any of that today.

My subject here is the environmental impact of animal agriculture. This impact is factual and quantifiable regardless of what one believes about what one should or shouldn’t do or eat. I will be addressing four categories of impact: land use, water use, pollution and climate.

Land use

Habitat loss is the single greatest driver of extinctions and declining biological diversity in the world today. Agriculture is the biggest cause of habitat loss, with animal ag making up 80% of agricultural land use.

Fully one quarter of the planet’s land area—an area the size of North and South America put together—is currently used for animal ag. About 88% of that is grazing land and the rest is feed production. Only 16% of agricultural land is devoted to crops for human food.

In the United States, 35% of the Lower 48 is pasture and range for grazing (much of it on public land) and another 6% is for feed. 40% of corn and 60% of soybeans are grown for animal feed. You may have seen this very helpful chart of land use in the US. (Note this is a chart illustrating quantities not a map outlining locations.)

All of this agricultural land represents degraded or destroyed wildlife habitat. Whatever animals and plants lived there before were either extirpated or greatly reduced in numbers. Some of this land is regularly sprayed with pesticides that spread into non-farm lands through air and water, harming more wildlife.

The loss in biological diversity since the beginning of Agricultural Revolution has been astonishing. Here’s one way of picturing it:

Since 1970 especially, wildlife have taken a huge hit. Around 50% of mammal, bird, fish and reptile populations have been in decline since then [source]. Insect numbers have been plummeting populations and their ranges shrinking [source]. One third of amphibian species worldwide are threatened [source]. Habitat loss is the biggest cause of these downturns, with pesticides use playing a big role for insects in particular. The majority of this is due to animal ag. Deforestation for grazing and feed production is major factor. For example, between 1991 and 2021, 780,000 square km (303,000 square miles) of the Amazon was clear-cut, with about 80% of that linked to expanding pasture for cattle [source].

Currently 94% of all mammalian biomass excluding humans is cattle, and 71% of all avian biomass is poultry [source]. This is the result of converting ecosystems for wildlife into production zones for domesticated animals. Still, “meat, dairy, and farmed fish provide just 17% of the world’s calories and 38% of its protein” [source]. So the output of 4/5 of all agricultural land is less than 1/5 of all calories.

Water use

Globally, 30% of freshwater is used for animal agriculture, predominantly for irrigating feed crops. In the United States, it’s 23% with great regional variation. For example, in terms of water directly consumed from the Colorado River basin of the arid West, that figure is double: 46%. Only a trickle of the Colorado River actually flows all the way to the sea, and a once moist delta is now salt flats.

All the dams and diversions in the Colorado River basin—along with cattle ranching—have significantly altered ecosystems throughout the region. Cottonwood and Willow, which depend on regular spring floods to distribute and germinate their seeds, have been in decline along most of the system’s tributaries.

Throughout the United States, wetlands disappear or shrink as water tables fall from irrigation diversion. Lower water levels in rivers endanger fish.

In the Midwest, the Ogallala Aquifer has dropped hundreds of feet from decades of pumping. This aquifer is not naturally recharged by precipitation, but is a relic from the last glaciation period. Once it’s gone, it’s gone, at least until the glaciers flow south again. Corn and soy, much of it for animal feed, are the major crops watered from the Ogallala Aquifer.

Fresh water, it should go without saying, is a finite resource. What we take to irrigate feed crops is taken from somewhere—and someone—else. The more-than-human world is, so far, suffering more than humans from our profligate use, but current levels of consumption are unsustainable by any measure.

Pollution

Agricultural run-off happens when precipitation or irrigation carry substances from a field into nearby rivers and streams. The primary problem substances are fertilizers, pesticides and animal pharmaceuticals. The amounts build up as a waterway flows downstream, eventually to the ocean.

Ocean “dead zones” are caused by excessive nutrient levels in the water, primarily nitrogen and phosphorus run-off from fertilizers and manure. In a process called “eutrophication,” these nutrients cause exponential growth of algae and cyanobacteria, leading to algal blooms. When these organisms die, their decomposition consumes the oxygen dissolved in the water, leading to “hypoxic” (oxygen depleted) conditions that can’t support most marine life. Surviving creatures who are mobile are forced to flee their home habitats. Immobile organisms like shellfish are trapped. Coral can be bleached.

Run-off also impacts areas closer to the source. Nearby wetlands and waterways are also subject to eutrophication. The waterborne species who die are food to other species, terrestrial and aerial. In nature, you can never just affect one thing. You can tap just one thread on a spider web but the whole thing vibrates.

Run-off includes sediment and erosion, both of which can be exacerbated by mechanized farming techniques and overgrazing. Top soil loss is its own crisis but the extra sedimentation in local rivers and streams is harmful to aquatic life.

Infiltration / percolation is different from run-off. This is when precipitation or irrigation soaks down into the local water table, carrying substances with it. Fertilizers, pesticides and animal pharmaceuticals can enter ground water this way. Salinization of the water is an additional effect in some regions. For example, in the Colorado River basin, as water from sprinklers or flood-irrigation percolates down through soils in pastures and fields, it picks up minerals that are added to tributaries via the water table. Salinity levels are so high in the Colorado by the time it reaches California that the water must be filtered to make it usable.

Pesticides—a blanket term for herbicides, insecticides, fungicides, etc.—are lethal by design, and they are no less harmful outside the farm fence than inside. Run-off carries them into surrounding areas where they affect wildlife, especially aquatic species like fish, amphibians and invertebrates. They also percolate into ground water and contaminate well water. Some can remain persistent in the soil for many years. Two major animal feed crops, corn and soy, have been genetically modified for resistance to glyphosate, the active ingredient in Monsanto’s Round-up line of herbicides. Use of Round-up has increased since the widespread adoption of these GMO varieties.

A few toxins can be stored in the tissues of an organism (“bioaccumulation”), and then be passed up in the food chain from prey to predator in increasing concentrations (“biomagnification”). A famous example is how DDT biomagnification led to eggshell thinning in predator bird species in the mid-20th Century. DDT has since been banned but other toxins capable of bioaccumulating remain, though less harmful.

Animal/veterinary pharmaceuticals are a bigger deal than I thought. As a topic it’s also a bit onerous to research because most of the information is in scientific journals [for example here, here, here], so I’m really just trying to give a brief summary here. I could have spent a week going down this rabbit hole, but it’s only of passing interest for me. Anyway:

The broad classes in use are antibiotics, antiparasitics, vaccines, growth hormones, anti-inflamatories, and beta-agonists. Beta-agonists are used to produce lean muscle growth instead of fat; the others are self-explanatory I’m assuming. Veterinary medicine has long been a thing, of course, but the need for the high quantity of vaccines and the various anti-s these days has been driven by the expansion of CAFOs (concentrated animal feeding operations). Think the huge sheds packed with pigs or poultry, or the confined feedlots for beef cattle. CAFO conditions are unhealthy for animals, hence the need for more medicating. The crowded conditions are ideal for the rapid spread of disease, hence the vaccines. The animals literally must be drugged to be kept alive.

Many pharmaceuticals are not fully metabolized by the animals, so they’re found in their manure and urine. When this waste is spread on fields, the drugs or their break-down products are then subject to run-off to wetlands and rivers, and to infiltration into the groundwater. Some also persist in the soil for months.

• Antibiotic use on domesticated animals is leading to increasing antibiotic resistance among bacteria and microbes, which is affecting humans. The World Health Organization considered antibiotic resistance to be “one of the ten global public health threats facing humanity” so this is a big deal [source]. Some strains of Salmonella, E. coli and Staph are examples.
• Some antiparasitics pass through the body intact and kill manure-eating invertebrates like dung beetles and other insects. Ironically, the lack of dung beetles leads to imbalances in soil health that encourages more parasites [source].
• Hormones act as endocrine disrupters for various aquatic species including fish and amphibians.

Manure lagoons are another vector for environmental contamination, and a particularly disgusting one at that. They are compacted earth or clay-lined ponds used to store the enormous amounts of manure and urine produced by CAFOs.

Manure lagoons emit methane and ammonia, the latter of which is why their odor is so strong. If you’re driving through farm country, it can be over-powering when you pass one. This is not merely gross; it can be deadly. If they overflow or are breached, the resulting run-off pollutes surrounding land and enters waterways. Spills are so common they’ve been called “accidents waiting to happen.” If they leak, they can can taint groundwater.

In Iowa, manure spills and nitrate poisoning of the water are an on-going crisis. Hundreds of thousands of fish can die in one event. The city of Des Moines has “one of the world’s largest nitrate removal facilities.” Over exposure to nitrates causes blue baby syndrome, among other things. Ratepayers pay the extra cost associated with running these facilities more often [source for above]. This isn’t the only cost to citizens of that state, the only one where cancer rates are rising, in correlation with rising nitrate levels.

Climate

It’s a well known and often cited statistic that 14-15% of global greenhouse gasses are produced by cows, from the methane that results from their digestive processes.

How grass-fed beef operations compare with CAFOs in terms of greenhouse gases is currently being debated. Some claim that on a per pound basis, grass-fed cows emit more methane due to longer lifespans, more animals needed to produce the same amount of beef, and diets that are more difficult to digest. On the other hand, advocates of regenerative grazing claim that carbon sequestration from grazing activity itself makes up for this difference. (Fwiw, this study says in most cases it doesn’t.) The jury is still out on this question.

But emissions are only one leg of climate change, the other being land use alteration because of how it modifies water cycles and temperatures. So the clearing of ecosystems for grazing and for feed crops must also play a significant role, but I could not find a statistic relating directly to that.

Wrap up

In terms of environmental impact, animal ag in the US is figuratively and literally a shit show, with that shit running off into the rivers and making dead zones in the oceans, while what ground water that isn’t being depleted is being toxified with agricultural chemicals and pharmaceuticals, and forests are being razed for pasture and feed crops.

Given all this, it’s undeniable that current rates of meat consumption (let alone what’s projected for the future) are environmentally unsustainable. The folks advocating for a meat-heavy diet for whatever reason (and no, our paleolithic ancestors weren’t predominantly carnivorous) need to grapple with this; either accept that a smaller amount is fine, or that global human population growth needs to be reversed, or both. Yeah, people like hamburgers and fried chicken, and bacon tastes good, but we can’t go on like this. The more-than-human world can’t take it.