That is not sauce, looking for wiki end of article academic type sauce.
problem with the internet is, you read something and don't save it.
I have looked a little, the problem is there is so many little points.
the same dataset will be written about in conflicting ways on a pro or a con website.
but let us assume for half a second, we do this research ourselves.
how much land would you use to grow all your food if you are a vegetarian. just you 1 person only vegetables.
now make you an omnivore, is the space used the same or more?
now lets make it a town of 20 people.
Vegetarian town uses up this much space for grain, corn, legumes, potatoes, carrots, tomatoes, chickens (for the egs only) goats and cows for sheep.
Omnivore town uses the same amount of space, but uses it better because the animals can be eaten as well. so in theory you could feed 25 people instead of just 20
simple logic states that as the amount of people increase the amount of space needed to produce food of purely vegetarian persuasion will increase, but the amount of space required for an omnivore diet will taper out.
when we get into carbon emissions vs calories things get more complicated.
my argument is purely based on square meter per kilojoule and there meat wins. by far. and veal is 100% the best thing to eat.