These are separate arguments that are often simultaneously held to be true by the same individuals, failing to realise they if either one were true they would be mutually exclusive. These arguments imply that it is acceptable to eat animals because it is the lesser of two evils; that if we did not eat them animals would overpopulate the planet or go completely extinct as they could not survive on their own.
Firstly, the argument that animals would overpopulate the planet if we stopped eating them is utterly ridiculous and flies in the fact of common sense. Even the most optimistic vegans do not expect the world to go vegan overnight, what we would hope to see is a gradual process where the demand for animal products is lowered, and thus so is the supply. If the Coca-Cola company slowly lost half of its sales over time, it would not continue to make and attempt to distribute the same number of bottles, as this would make no financial sense. Similarly, if the global demand for animal products is reduced over time, then there will be less supply, so less animals will be born and slaughtered. Farmers will not simply keep breeding the same number of animals with no one to purchase the products made out of their bodies. To suggest otherwise is completely illogical.
This leads us on to the second argument at play; as less of these animals are being bred into existence, less would exist, and eventually, it is argued, none would exist at all. Therefore, we are somehow acting in the best interests of animals to breed, exploit and consume them. Firstly, this assumes that no one could possibly be willing to take care of a farmed animal without making a profit out of them, ignoring the existence of the many non-profit sanctuaries and private rescuers already in existence the world over. This argument also assumes that extinction is not a preferable option than continuing to be force bred, imprisoned, exploited and slaughtered. Given the horrific and short life your average farmed animal can expect to be born into, if asked, I do not expect that they would agree.
Furthermore, we must remember that we are not talking about the happy, healthy animals seen in idyllic cartoon advertisements and on the front of packages. We are talking about animals so genetically modified and selectively bred that they are designed to produce as much meat, milk or eggs as possible with no regards for their health. We are talking about chickens bred to grow so fat, so quickly, that they often cannot even walk, cows bred to produce seven times more milk than they did a century ago, turkeys so genetically diminished that they can’t even naturally breed. These animals are a far cry from their natural ancestors, it is simply ridiculous to claim that since we made them this way, we have to keep doing it for their own good. If indeed these animals would go extinct if we stopped farming them, that could rightly be considered a mercy.
Arguments like this one are little more than attempts to use reason to justify what is an ultimately irrational decision. No one eats animals because they are worried they will overpopulate or go extinct if they don’t; we eat them because they taste good. This argument is particularly insidious, since not only does it seek to justify the mass exploitation and slaughter of billions of animals, but in the same breath, it tries to convince us that doing so is actually in their best interests. Only those willing to delude themselves in order to continue benefiting from the misery of animals would believe such a proposal.