Vegedus wrote:How are they necessary for your survival?
It's very simple, really.
If a species such as us relied solely on plant proteins and fibers, our brain never would have evolved to the point we're at now. All carnivores have larger brains than solely herbivorous creatures, because they need to outsmart them and come up with complex social structures that deal with things that herbivores simply don't have to deal with, such as small amount of game to name a single example. Animals that Migrate usually don't do so through thought, it's usually just instinct so that when they completely graze out one area, they go in a migratory circle to greener pastures. (A good exception would be Elephants who use active memory and their unusually large brains to remember EXACTLY where oases and good food stores are.)
Carnivores usually capitalize on this, but when it comes to getting in each others' way, they usually can't keep up with migratory animals for more than 1 month out of the year so they have to use actual thought and memory to gauge patterns of what little food remains. A great example would be Africa and all of the animals in the great plains. So, with the advanced thought and ability to detect patterns, carnivores are not only able to outsmart Herbivores, they are also able to solve complex puzzles and think their way out of complicated situations.
Dogs, Cats, even some carnivorous birds like ravens and hawks, zoo and circus animals like dolphins, bears and orcas can all be trained and domesticated. There's a reason you can't train rabbits, they simply didn't evolve the need to be smart.
The truth of vegetarianism is you can't simply survive off of simple plants, you need specific vegetables (and/or fruit) to replace a lot of the nutrients you're missing to support your omnivorous brain. We evolved around a balanced diet, limiting yourself to simply vegetables or simply meat is dangerous and always has repercussions that CAN be avoided with specific variations of your food, but can be easily and naturally avoided by just eating a slice of pepperoni pizza.
I'm probably missing other smart herbivores and things like that, but my main point is that our brain requires nutrients more commonly found in meat than in plants simply because we evolved that way.
Now that the history of our brains is out of the way, all other things you mentioned are 100% correct. It's much less effective to farm/ranch meat than it is to do so for grains and vegetables and if we don't change our ways we will suffer from food losses in the near future. However, as long as half of America is obese, I'm not really in a hurry to call out a Famine yet.