I am both surprised and happy to see a discussion about the dietary habits that people have.
I am not a vegetarian, but I eat very little (if any) meat a day. At the risk of sounding callous, I really don't care too much about what happens to animals. If people didn't meat, other animals would.
People do not [b]need[/b] meat anymore. Meat (particularly red meat) is extremely high in fat, which is why it was great for our ancestors. Food was scarce and fat holds the highest amount of calories per gram. With modern agricultural technology, we grow and consume so much food and take in so many calories that our bodies don't know how to handle it. That is why 1 out of 4 american adults are obese. Meat is a good source of protein. Other good sources of protein are: soy, protein shakes, protein pills, etc. If you go into any GNC, they will point out a huge area of the store dedicated to low fat/no fat protein.
As for food shortages, check this out. For every animal on the food chain, only 10% of it's matter moves up the food chain. What do I mean by this? If you want to eat a 100 pound cow, that cow would have to eat (in order to get up to that size), 1000 pounds of plants. That means, if everyone only ate plants, there would be 10 times more food in the world. (If anyone already said this or if I fucked up my facts I apologize, I am trying to recall facts from 10th grade biology.)
So, even if you don't give two shits about animals, EVERYONE needs to eat healthier. People don't realize how many calories they eat in a day. The sooner they do, the less risk they have of serious health risks later on.