Cover of "Livestock's Long Shadow: Enviro...

Cover via Amazon

We all need clean water. No doubt about it. HOW to get it and keep it running clean and plentiful is becoming a problem almost everywhere. In fact, the United Nations’ Food and Agricultural Organization (FAO) predicts in a report titled Livestock’s Long Shadow, that by 2050, two-thirds of people worldwide will lack clean water to meet even their basic needs.

The good news is that one part of the solution is easy and close at hand! It all starts with your fork.

“Livestock are one of the most significant contributors to today’s most serious environmental problems. Urgent action is required to remedy the situation.”

H. Steinfeld, senior author, Livestock’s Long Shadow, A report from the United Nations

Saving Earth’s Water By Eating A Vegetarian Diet

Did you know that the largest user of fresh water is the livestock industry? Water is directly needed for drinking and cleaning of animals. And that’s a lot of water when we’re talking about over 10 billion animals raised for food in the United States alone every year.

But the biggest way animal agriculture consumes water is indirectly. A large amount of fresh water is used to grow the feed that livestock animals eat.

By comparison, it takes a lot less water to grow the grains, beans, legumes, fruits, and vegetables that make up a typical vegetarian diet. Here’s how the numbers stack up according to researchers whose work is cited in the U.N.’s Livestock’s Long Shadow:

Table 1. Estimated Amount of Water In Liters Used to Produce One Kilogram of Food in the U.S.
(Note: One liter (L) is approximately the same as one quart. One kilogram (kg) is approximately the same as 2.2 lbs.)

Food Item
Hoekstra & Chapagain
Zimmer & Renault
Pimentel, Berger, Filiberto, et al.
Corn 500 700 650
Wheat 850 1,200 900
Soybeans 1,900 2,000
Rice 1,600 1,400 1,600
Cow’s Milk 700 800
Eggs 1,500 2,700
Beef (feedlot) 13,000 13,500 143,000
Beef (rangeland) 12,000* 120,000-200,000
Pork 3,900 4,600 6,000
Poultry 2,400 4,100 3,500


Table 2. Global Averages of the Quantity of Water Required to Produce Certain Food Products (Liter)
Note: One liter (approximately one quart) equals 1,000 milliliters (ml). One pound equals 454 grams (g).

Food Item Water Needed for Production (Liter)
1 cup of coffee (125 ml) 140
1 glass of milk (200 ml) 200
1 slice of bread (30 g) 40
1 slice of bread (30 g)
with cheese (10 g)
1 potato (100 g) 25
1 bag of potato chips (200 g) 185
1 tomato (70 g) 13
1 apple (100 g) 70
1 glass of apple juice (200 ml) 190
1 egg (40 g) 135
1 hamburger (150 g) 2400
Dry pasta (made in Italy; 1 kg)* 1900
Cheese pizza (made in Italy; 725 g)* 1200 (or 248 L per 150 g = ~ ¼ pizza)
Tomato pizza (made in Italy; 600 g)* 300 (or 75 L per 150 = ~¼ pizza)


Animal Waste

Besides using all that clean, fresh water, animal agriculture pollutes a lot more of it. Livestock’s Long Shadow states that tons of animal wastes are discharged into waterways each year. The report says that in most of the developing world, untreated manure enters water used by people for drinking, washing and bathing.

Along with the manure flow lots of other undesirables including pesticides, antibiotics, hormones, and their breakdown products, not to mention the surplus of nitrogen and phosphorus coming from fertilizers placed on the feed crops. All of this livestock-related influx upsets balance in nature. It can lead to fish kills and algal blooms which can deaden lakes.

Poor GrainMeat Conversions

To produce meat for people, animals need to eat. In most cases, a significant portion of their feed is grains. The grain-to-meat conversion process is not perfect: “one pound of grain in” does not equal “one pound of meat out.”

Here’s how various agencies and researchers calculate the grain-to-meat conversion:

Table 3. Quantity of Grains* (kg) Eaten by U.S.** Livestock to Produce One Kilogram of Meat

Livestock type CAST (1999) EPA (2007) USDA (2009) Pimentel (2003)
Beef 2.6 6.5 ~4 13
Pork 3.7 3.0 5.9
Chicken 2.2 1.9 ~1.9 2.3

The EPA values were accessed at in March 2009.

The USDA values for beef and poultry were from personal email communications with employees of the Economic Research Service (ERS) branch of the USDA. (~ means approximately). Pimentel D, Pimentel, M (2003) Sustainability of meat-based and plantbased diets and the environment. American Journal of Clinical Nutrition 78:660S-663S. (Reprinted in their 2008 book titled Food, Energy, and Society, 3rd ed.).  Note that meat may mean “live weight,” not “consumable food.”

During grain-to-meat conversions, there are water losses along the way. First, there’s water loss when the feed crops lose water through evapotranspiration, a natural process that’s part of a plant’s normal growth. Livestock’s Long Shadow estimates that this loss accounts for 15% of all freshwater loss on a global basis.

Inefficient irrigation contributes to water runoff from cropland and to further evaporation loss. In 2008, approximately 50% of the corn crop and 60% of the soybean crop were fed to US livestock according to the United States Department of Agriculture. That’s a lot of indirect water used by livestock, not to mention the topsoil erosion that occurs.

Vegetarians eating a variety of grains and legumes directly as the basis of their diet conserve water by eliminating meat, the middle part of the grain-to-meat conversion process.

How Your Food Choices Impact the AIR and the LAND

Livestock’s Long Shadow states that the #1 contributor of greenhouse gases is not vehicle emissions, but raising livestock which accounts for 18% of all carbon dioxide equivalents. And between the methane, ammonia, and nitrous oxide, the situation is really heating up (literally!) on a global level.

Livestock’s Long Shadow reports that raising livestock is responsible for 70% of forests cleared for grazing and feed crop production in the Amazon Rain Forest. Breathe easier and help keep the earth green by going vegetarian.

One Simple Step

So that’s how easy it is for YOU to make a difference. A simple step to keeping water clean and keeping it plentiful for generations to come. And while you’re at it, you’ll be helping to keep the air clean, the forests green, and biodiversity thriving. The really cool thing about it all is that you can start TODAY with your next trip to the store.