With the way climate change is going, the human population will be closer to 0 in the year 2050 than 20 billion.
The average american eats ~200lbs of meat a year. that's alot, it's a person and a half.
But the discussion should not be about how much meat a person should eat, the answer is -0-.
Meat, is highly toxic to the human body. Our digestive tract is too long, as it is designed for eating plants. REAL carnivores have very short guts, so the meat goes in and out quickly.
In humans, meat Putrifies in our gut. Japan used to be primarily plant based, but after ww2 when American culture hit the island, their Colon and Bowel cancer exploded.
Cholesterol gives us heart attacks. Meat is also our primary exposure pathway for Dioxins, Pcb, mercury, tmao, AGEs, Neu5gc, Heme Iron, Heterocyclic amines. Meat also concentrates pesticides because we're feeding many times the food a human would eat to the cow, our exposure increases by 2x-6x. Fish is the worst, the ocean is the public sewer and a chemical dumping ground, all of our industrial output ends up in it, The sea life bio-accumulates these toxins up the food chain from plankton up to larger fish.
We are also megadosing ourselves in animal estrogen by drinking cow's milk and eating beef. Milk gives men moobies.
So if eating meat is ONLY bad for humans, and it's the primary cause of climate change as it opposes Carbon sinking <forests> , we shouldn't eat it at all.