many veggies protest the treatment of farm animals not the fact they die. They may be there for our food but imo they should have a happy life in the interim. They get pumped with growth hormones, taken from their mothers and raised in tiny pens. That isn't fair. Im not a veggie but i try to make sure I eat free range eggs and meat from RSPCA approved farms. You can never guarrantee your meat is truly happy tho

You may not have realised this, but cows, pigs and chickens are herbivores. They eat plants. In order to get 1kg of meat, you have to have fed that animal far more than that per unit mass. So by not eating animals, you're actually consuming less "oxygen", as less plants need to be grown. Something like 90% of the world's edible food crops are fed to livestock in order to produce meat. Consider it like this: Plants obtain energy from the sun. Herbivores obtain energy from plants. First-level carnivores eat herbivores. Second-level carnivores eat the first-order carnivores. Roughly 90% of energy is lost between each stage, as it's used by the organism to grow, reproduce, etc. So the higher-up you are on these levels (they're called trophic levels), the less energy-efficient your diet is. The most energy-efficient source of energy is the sun, but humans can't photosynthesize so the most achievable level of efficiency is to eat plants. With the carbon dioxide point, yes, the livestock industry produces more greenhouse gases than all forms of transport in the world combined. If we stopped mass-breeding animals for us to eat, and ate the plants instead, we'd be both reducing greenhouse gas emissions and increasing the capacity for oxygen production.