A plant-based diet not only emits less CO2 but also uses less water, among many other environmental and health benefits.  According to a 2014 study in the UK, a vegan diet had less than half the emissions of a diet where people consumed more than 100 grams of meat a day. While this sounds like a lot of meat, the average American eats almost 250 grams of meat a day, according to a 2015 study. The EU consumes over 175 grams per person, and almost all of the world, with the exception of Africa and southwest Asia, almost every nation exceeds 100 grams of meat consumption, per day per person. Thus, for many people, a vegan diet likely reduces CO2 emissions more than the study concluded. Additionally, a vegan diet requires far less water. A pound of beef takes over 180 times the water of a pound of wheat. Also, to produce a liter of milk, 1000 liters of water are expended. With 70% of the global water supply used in food production, and droughts expected to be more common with global warming, veganism is a great choice to help prevent global warming and adapt to the problems i t will cause.

Sources:
1. https://www.vox.com/2014/7/2/5865109/st … nt-in-half
2. https://link.springer.com/article/10.10 … 169-1#Sec8
3. https://www.theguardian.com/news/databl … bal-trends
4. http://shrinkthatfootprint.com/food-car … print-diet
5. http://www.businessinsider.com/where-do … eat-2015-9
6. https://www.forbes.com/sites/niallmccar … 7f86da4f95
7. https://www.theguardian.com/lifeandstyl … nvironment

Yes, becoming a vegan may help the environment, it is also important to note that being a vegan can also have its negative effects. For example, many vegans, or people in general, eat imported fruits such as mangos from India or avocados from Mexico. These imported foods have a larger negative impact on the environment than beef from a local farm or eggs from a neighbors backyard. Instead of becoming a vegan, I would tell somebody to change their diet by eating locally grown foods. This cuts out the energy needed to move food from place to place and ensures that you are getting fresh, healthy food. One other disadvantage of the vegan diet is the lack of protein in food. To supplement this, many people eat or drink soy products such as tofu or soy milk. The production of soy, is in short, killing our rainforests. Soybean plantations are taking over rainforests, adding even more to the problem of deforestation. These large farms are also pushing out smaller communities and farmers. Again, I am not saying that being a vegan is worse or as bad as eating meat, I just want to  show that veganism is not as perfect as many people see it as.

https://www.independent.co.uk/life-styl … 77541.html
http://wwf.panda.org/what_we_do/footpri … y/impacts/

Caitlin- you make a lot of good points.  And I agree with you that like everyone, vegans need to consider where their food comes from too. 

But since you mentioned soy and deforestation did you know that, according to the Union of Concerned Scientists, "70-75% of the world’s soy ends up as feed for chickens, pigs, cows, and farmed fish"?

https://www.ucsusa.org/global-warming/s … t14lBiZPeQ

Veganism, as you say, is not perfect by itself.  But I think there is little doubt that, on average, a vegan diet has less of an impact than an average meat-eating diet.

My concern is that someone reading your comment might think: "ok well both eating meat and being vegan are bad - I guess I will just keep eating the same amount of meat then"

Max, Caitlin, and Jason, you all make very good, well-informed points about being a vegan, versus being a carnivore. Personally, I am an omnivore, and I think that doing so has the right effect on my body. However, Caitlin, what would you say about people who cannot get locally sourced vegetables or even meat. As surprising as it may sound Texas is ranked 52 after Puerto Rico and D.C. as the worst state for locally sourced food and vegetables, according to strolling of the heifers (https://www.strollingoftheheifers.com/locavore/). I agree with Jason and ask when you say that people "will continue to eat the same amount of meat" what do you mean by that. As well, what is the solution?  For Max, why does a vegan diet mean less CO2 emissions? You cannot simply claim that it does so, without an explanation. As well, think of all the people and old, diesel-powered equipment used to harvest these vegetables. As well, if you are killing and producing your own meat, it wo uld be much more efficient than going to a farmers market, spending money, and driving all the way home. In short, I think that eating a mixed diet, maybe weighing on meat, is more productive.

For one, it's not just vegans who eat imported fruits and vegetables. Most people do. It is not specific to vegans. However, buying local and organic food is another step, on top of veganism, that people can do to help the environment.

The Independent article cited by Caitlin says, "eating lamb chops that come from a farm a few miles down the road is much better for the environment than eating an avocado that has traveled from the other side of the world" (5).
As previously stated, vegans are not the only people who eat imported food. There is nothing to suggest that vegans eat more imported food, so many meat eaters might eat the lamb chop (local or not) and that avocado from the "other side of the world." 

According to the World Shipping Council, the CO2 emissions for shipping a metric ton of goods a kilometer is 10 grams, while the Emergency Community of Airport Entrepreneurs Hamburg says it takes between 10-40 grams of CO2. According to sea-distances.org, it is about 21,000km from a port in Kenya to San Francisco. Thus, even if we use 40 grams per ton per kilome ter, it is (km*grams of CO2 per metric ton) or (21000*40) = 840000 grams of CO2 to ship a metric ton of goods from Kenya to San Francisco. 840000 grams is 840 kilograms of CO2 to ship one ton. Because there are 1000 kilograms in a metric ton, the CO2 footprint to ship goods from Kenya to San Francisco is 0.84 kg of CO2/ kilogram of goods. The following emissions from various foods are based on data from Business Insider. While a kilogram of rice, lentils, and nuts (protein equivalents to meat) emit under 3kg of CO2, a kilogram of lamb produces 39.2 kilograms of CO2. Even leaner meats like chicken and canned tuna emit 6.9 and 6.1 kilograms of CO2, per kilogram, respectively. Thus, 0.84 kilograms of CO2 expended to ship plant-based foods across the world is incomparable to the additional CO2 expended to produce meat. Assuming plant-based protein emissions at 3 kilos per kg (high), and lamb emissions at 35 kilos per kg (eliminating all post-production and transportation emissions to generously account for the stated "few miles down the road"), emissions for transport would need to be about 1520g for a metric ton of goods to be transported a kilogram. This is about three times higher than airfare emissions estimated from my sources for naval emissions. Thus, it is incomparable to suggest that local lamb is less bad for the environment than imported plant-based food. Overall, my point is that vegans are not the only ones who consume imported goods (fruits and vegetables aren't even the only food items imported), and that, based on my data, comparing the emissions from shipping to producing meat is not valid. However, it is still significant and everyone should try to eat local when possible.

Grayson asked why meat produces more CO2.  Meat contributes more CO2 to the atmosphere because animals eat many plants and drink lots of water to grow. Also, some animals, like cows, also emit methane through flatulence, and all animals exhale CO2. Animal products suffer from similar inefficiencies.

I appreciate the discussion. Also, if someone finds contrary evidence for emissions, I would love to hear it!

Sources:
http://www.businessinsider.com/the-top- … int-2015-9
http://www.worldshipping.org/industry-i … -emissions
https://www.fluglaerm.de/hamburg/klima.htm

Also, the Independent article Caitlin used also stated that increased demand for avocados and quinoa because of the rise of veganism has caused supply shortages which make those products out of reach for locals who often consume that food. While this is unfortunate, this is related to the principles of capitalism, not veganism, and should likely be temporary, because now that there is a larger market more supply should be created around the world.

Although I am not a vegan, I still want to agree with your opinion. I want to point out that the meat only supplies a tiny bit of energy but requires a huge amount of energy to get a little piece of meat. For example, getting a pound of meat on the pig might need 10 pounds of food to feed it. A lot of energy is wasted through the process. Besides, handling the meat and saving it in the refrigerator would spend much electricity.