To learn more about the environmental impact of meat consumption, I recommend this Our World in Data article: https://ourworldindata.org/environmental-impacts-of-food
I would highlight this chart: https://ourworldindata.org/grapher/ghg-per-protein-poore?country=Pig+Meat~Beef+%28beef+herd%29~Eggs~Lamb+%26+Mutton~Grains~Milk~Other+Pulses~Poultry+Meat~Tofu+%28soybeans%29~Peas~Nuts~Groundnuts~Fish+%28farmed%29~Cheese~Beef+%28dairy+herd%29~Prawns+%28farmed%29~Tofu
For example, getting 100 g of protein from beef emits ~ 50 kg of CO2. Getting 100 g of protein from tofu only emits ~ 2 kg of CO2.
This is simply not true. Globally, 77% of the land area that's used for agriculture is used either by livestock or to grow food to feed to livestock (such as corn and soy). Only 23% is used for crops for direct human consumption (1): This makes sense intuitively: If I feed a cow 1 kcal of energy, it will create way less than 1kcal of energy to be consumed. In fact, beef has an energy efficiency of 1.9%. This means, for every 100 kcal the cow eats, you only get out 1.9 kcal (2). Otherwise, cows would defy the laws of physics. Do you really think that the 74 billion chicken, 620 million sheep and 330 million cattle that we slaughter each year for meat just are fed human-food leftovers? (3)
1: https://ourworldindata.org/global-land-for-agriculture 2: https://ourworldindata.org/meat-production#energy-conversion-efficiency 3: https://ourworldindata.org/meat-production#livestock-counts