Nevermind all the ways our "water drinking habit" bites us back.
We are omnivores. We need vegetables AND meat to be healthy. I think what you meant to say is it's another way our overpopulation is biting us back. If we didn't have so many people we could still have normal herd sizes.
(Granted, it's likely the prevalence of said food that led to overpopulation... oh nevermind.)
Animal consumption has scaled considerably faster than population, so I don't think it's solely that. The traditional Mediterranean diet, for example, uses much less meat than is now commonly consumed in the Mediterranean countries.
My guess is some mixture of affluence (can afford to import meat from faraway factory farms), the factory-ization itself (meat is a cheap-ish commodity), and decline in cooking skills and time available to use them (most good vegetable-heavy dishes take more time and skill to cook than a hamburger does).
Enough people are living as vegetarians to counter your claim of meat being necessary. Even so, meat consumption per person seems to go up everywhere, so even if you assume people need meat, a century ago they needed a lot less meat per person somehow.
In today's world, vegetarians have access to various non-animal sources of protein that our bodies cannot produce on its own. This has not always been the case. Regardless, the point is our bodies need certain things to be healthy, and those things are historically mainly found in meats and vegetables.
And I won't argue that we eat more meat than our bodies need. But then again, we eat more EVERYTHING than our bodies need. Most of that is likely due to our survival instinct that makes high calorie food taste appealing- protein, fats, and sugars.
They would lose, you can get vitamin C just fine from either a plant only diet or a meat only diet. Organ meat is a good source of vitamin C, especially liver.
What? Lot's of diseases are a result of animal farming - see "Guns, Germs and Steel" for an account of how the germs we bred in Europe helped deplete the New World of people who weren't exposed to animal farming yet. And modern factory farming will add it's share (antibiotics resistances and so on).
We are omnivores. We need vegetables AND meat to be healthy. I think what you meant to say is it's another way our overpopulation is biting us back. If we didn't have so many people we could still have normal herd sizes.
(Granted, it's likely the prevalence of said food that led to overpopulation... oh nevermind.)