05/31/2008 05:12 am ET | Updated Nov 17, 2011

Go Green by Eating More of Your Greens

A recent visit to the American Museum of Natural History in New York got me thinking: going vegetarian is probably the boldest step any of us can take to lead a greener life.

My mind kept returning to an amazing statistic from the new exhibit "Water: H2O = Life": 600 gallons of water are needed to produce a single hamburger. 600 gallons -- that's enough water to hydrate a person for over 3 years (at the recommended rate of 8 glasses per day). And that's just the beef patty--no bun or fixings included.

Full disclosure: I am not a vegetarian. I try to limit eating meat, but chicken, pork, and beef are all on my menu. Still, those water statistics got me thinking about the nexus of meat production and some of our most pressing ills, like food and water shortages, polluted oceans, land degradation, loss of habitats, and the big one, climate change. Believe it or not, producing our delicious meat has a part in all of these problems.

The way we produce meat today is very inefficient. Most animals raised for food in the United States are fed grain -- a lot of it. Each calorie of U.S.-produced beef requires about 7 calories of grains. For pork the caloric ratio is 1 to 4; for chicken it is 1 to 2.

It's a similar story with protein. Each pound of "high-quality animal protein" requires about 6 pounds of plant protein (American Journal of Clinical Nutrition, 2003).

Here's the kicker -- U.S. livestock consume 7 times more grain than all Americans combined.

Needless to say, our meat-eating requires (literally) tons more grains than would, say, just eating the grain. This has enormous societal and environmental impacts. Let's look at just four.

The Food Crisis

Grabbing headlines lately are the skyrocketing prices for staples like corn and soybeans. High costs are squeezing people at the bottom of the income ladder, and malnutrition and starvation are on the rise in the developing world.

Clearly, eating meat did not precipitate this crisis. Nevertheless, because so much grain already goes to feeding livestock, when demands for grain increase for other purposes (say, for biofuels), the stage is set for today's problems. Somewhat ironically, the more we choose to eat grains over meat, the less demand there will be for grains and the more food there will be to feed people.

Water Shortages

Water is the life-blood of farming. In California and the American Southwest, irrigation is the circulatory system that waters the crops.

Irrigation uses about 40% of all freshwater withdrawals -- 137 billion gallons per day out of a total of 345 billion, according to government statistics. Irrigation is the largest single consumer of fresh water and can literally run rivers dry. Take the third longest river in the U.S. In theory, the Rio Grande drains into the Gulf of Mexico. But these days, it rarely reaches its mouth because over-extraction in part from irrigation dries it up before it gets there.

We'd use a lot less water if we ate less meat.

Water Pollution

Nitrogen is an essential building-block of life. Photosynthesis helps produce carbohydrates (molecules of carbon, hydrogen, and oxygen), but to make protein (an amino acid) you need nitrogen. Farmers use lots of nitrogen fertilizer to increase grain yields.

By some estimates, U.S. croplands use almost 19 million tons of nitrogen (Howarth, Ambio 2002). Of that, only about 1.3 million tons feed people directly in the form of grains. Almost 6 million tons go to animals, and of that 6, a little less than 1 million ton is eaten by humans in the form of animal protein. The other 5 million tons fed to animals is pissed away -- or, ah, excreted through another path.

Suffice it to say, meat-eating significantly adds nitrogen to our environment - creating huge consequences. A lot of that nitrogen leaks into our rivers and our streams, degrading water quality and killing fish. It also drains into our oceans where it causes huge dead zones. Each year, pollution from the Mississippi River snuffs the life out of a slice of the Gulf of Mexico the size of New Jersey.

Climate Change

Farming takes energy. Sowing seeds, irrigating crops, producing and applying fertilizers, harvesting the crops and transporting them to market mean burning fossil fuels, which in turn means spewing copious emissions of carbon dioxide (C02), the major global warming pollutant.

What's more, cow "burps" add emissions of methane, a global warming pollutant about 20 times more powerful than CO2. And on top of that, applying nitrogen fertilizers leads to the production of nitrous oxide, a global warming pollutant about 120 times more potent than CO2.

The United Nations estimates that the livestock industry accounts for 18% of all global warming pollution -- more emissions than those coming from cars!

And so...

We have another "inconvenient truth." One of the most effective ways to slash global warming pollution and lead a more sustainable life is to skip that burger.

Now, I confessed earlier to my carnivorous habits, and am fully aware of how difficult giving up meat would be. I like my fries with a burger. But we can all cut back on meat.

I'll close with another stunning statistic. If every American gave up meat one day each week, it would be like taking 8 million cars off the road. Such a move would help fight a myriad of problems, such as climate change, water pollution and scarcity, and rising food prices. So who's game for meatless Mondays?

Huffington Post guest blogger Bill Chameides blogs regularly at