Perhaps it's too much of a blanket statement to say that you cannot be an environmentalist and also eat beef. Certainly there's a theoretical threshold where someone can convert enough light bulbs, trade in their gas guzzler for an electric, and recycle enough cans and bottles that they could eat a burger without a heavy conscience. But, as a new study by the National Academy of Sciences points out, that threshold may be a whole lot higher than we thought.

Just how bad is the production of beef? Let's go through the findings.

The greatest impact beef production has on the planet is in its creation of greenhouse gases. This comes in two forms: (1) The CO2 byproducts associated with creating, harvest, and shipping the cow feed to the huge factory farm lots that dot the middle and west parts of the country; and (2) the methane that comes out of the cows themselves. If you've ever taken the drive up the I-5 to San Francisco, there's a good chance your nose got a small taste of that output near Harris Ranch.

Add those two numbers together, and you get a whopping amount of CO2 heading up into the atmosphere. In all, one pound of beef produces roughly 60 pounds of CO2. Only the production of lamb has a bigger number (86 pounds of CO2 per one pound of lamb), but the relatively small production numbers of lamb put it on a different tier than the factory farmed cow. To give it a true sense of comparison, cows need to be put up against other large-scale meats such as chicken and pork. How does it compare to them?

- A pound of beef produces more than twice the CO2 that a pound of pork does.

- A pound of beef produces four times the CO2 that a pound of chicken does.

And, just for good measure:

- A pound of beef produces 150 times the CO2 that a pound of tofu does.

In all, it adds up to beef producing roughly five times the CO2 emissions that other forms of meat create. Compare it with other "staple foods" like potatoes, rice, and beans, and beef produces 11 times more CO2 on average. In fact, the impact is so dramatic that a professor examining the data from the study suggests that people would do more for the environment if they kept their cars and simply ate less red meat.

But that's not where the study stopped, because there are more aspects to consider than simply how beef raises the levels of CO2. See, in order to raise a whole bunch of cows, you need two items: A whole lot of land, and a whole lot of water.

In previous studies, land and water use weren't considered when taking into account the cost of producing meat, seeing as those studies were performed in a time when water use wasn't on our minds. (Unlike now, when we're in year three of a record drought that's making us question whether or not the trailer for the new "Mad Max" movie is actually for a documentary from the future.)

To analyze water and land impact, the study's authors looked at how it compared to the production of other livestock. Their findings? Beef uses 28 times more land than the average livestock production, and uses 11 times more water. Eleven times more water. Put simply, if the state had access to that amount of extra water, we wouldn't be in the precarious position we're currently in now.

Which is all to say, feel free to get your leaky faucets fixed and cut down on the time you spend in the shower. But more importantly, when you're picking up things for that summer barbecue, leave the burgers out of your cart if you want to help conserve water.

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