um, so lets say that letting loose a whole bunch of animals onto the planet wasn't a problem. the pesticides, fertilizers, and poisons that agricultural farmers set/spray would be detrimental to water supplies, and would pollute groundwater, so really, being vegan would be just as bad as being a meateater if the whole world were to participate.
…I’m sorry what? Why exactly are we letting loose a whole bunch of animals and increasing our pesticide use? Those are some pretty massive assumptions right off the bat. First of all, if the world went vegan it’d happen over time, we wouldn’t suddenly have 60 billion farmed animals roaming the streets. As demand goes down, so does the number of animals being bred to fulfill that demand, which is basic economics. The ones who do remain can comfortable live out their lives in sanctuaries, as the lucky few already do.
As for pesticides, I think you must be assuming that if we all went vegan we’d need more vegetables to feed the population, but you’re very wrong about that. If we look at cows, for example, it takes 16 pounds of grain to make one pound of beef. That’s 94% more land, and 94% more pesticides than just eating that grain directly. All told, livestock consume 70% of all the grain we produce, 98% of all soy, and a fifth of all water consumed globally. Farmed animals take in far more calories in crop feed than they will ever give out in meat, meaning that they are literally detracting from the global food supply. If the world went vegan, we would add an addition 70% to the world’s global food supply.
All of this is also assuming that we would still be using pesticides and animal fertilizers, but by your own hypothetical the whole world is vegan, so why exactly would we be using products which harm animals? Plant ferifilisers are very effective and veganic farming already exists. It is not the case that crops can’t be grown without harming animals or people. I think if you’re really honest with yourself, the reason you aren’t vegan isn’t because “all the animals would be released and we’d use loads of pesticides if everyone went vegan", it’s because you like eating animals. I’d honestly prefer you just admit that instead of inventing these nonsensical straw man hypotheticals which waste everyone’s time.