Scientists have long understood that human actions are the primary cause of global warming. But one of the largest single organized human activity – growing livestock for food – contributes as much as any coal burning plant or petroleum consuming vehicle to global climate change.

According to a new article from E Magazine, livestock raising may account for as much as 18 percent of all greenhouse gas emissions. How does it work? According to the article, 'The Meat of the Matter,' the US meat industry alone produces about '60 million tons of waste annually – five tons for every US citizen and 130 times the volume of human waste.'

Cows, sheep, pigs, etc. have to eat, and their grazing involves more than one-fourth of all the land surface of the Earth. Even more troublesome is the fact that one-third of arable land is used to grow crops that are then fed to livestock.

Over doing it on livestock, has crowded out other animal species. Eight percent of the world's water supply is used by excessive livestock populations, adding to land erosion problems. Harmful chemicals such as pesticides and antibiotics are added to the environment and the food supply through livestock.

Meat production accounts for massive deforestation. Grazing has led to widescale soil erosion and land degradation. Fossil fuels are also used to operate equipment to care for the animals. On top of that, livestock – it really is no myth, writes E – creates more than one-third of methane which is more potent than carbon dioxide.

In the past, opponents of environmental policies that would combat global climate change have insisted that we can't do much about the problem, pointing the finger at cows (and their farts) as methane producers. But are cows to blame?

No, says the E Magazine article. The promotion of meat-based diets are a specific profit-driven human industry, especially in the US. Globally, humans eat more than 90 pounds of meat annually, while by comparison, people in the US consume about 200, according to 2005 estimates by the USDA.

To aid this environmentally dangerous but profitable trend, meat producers have created the message that meat is healthy, which 'is routinely reinforced through advertising and by the cultural signals we’re sent at school, work and church.' Vegetarianism is usually depicted as a 'fringe choice.' Recall, the beef industry's ferocious response to an Oprah episode some years back when she challenged the healthiness of beef.

From pesticides to diseases (like E. Coli and 'mad cow disease') and greenhouse gas emissions, meat production is a public health and global environmental problem. The E Magazine article quotes the Center for Science in the Public Interest's Michael Jacobson as saying, “From an environmental point of view, the less beef people eat the better.'

Do we need to cut out all meat? Some will say yes, but for those who aren't ready to make that 'fringe choice,' eating less meat makes sense from all sides. When eating meat, use the hand test. If the piece of chicken you're about to plop down in the frying pan is bigger than your whole hand it is too much for one adult. If the piece of steak or pork is bigger than your palm, divvy it up with your companion.

Save the planet. Stay healthy.