since rearing livestock will not be a sustainable option.
That is a moral opinion.
Sustainable at what standard and for whom?
If you want to end unnecessary suffering... end overpopulation, so that species can continue to exist. In contrast to that task, vegetarianism is a paltry substitute and a surrogate activity that takes the place of real action.
outside of a major change in the foundations of our civilization such as a drastic reduction of our population, eating meat will further perpetuate the ecological crisis. check our history, note the pattern, study how much rice you can grow on a field compared to the kilograms of meat you can farm. results can be scientifically proven yet often times the individual will choose the most emotionally appealing of evidence- think of passive smoking. also, in my city veganism in young people is almost always tied to advocation of a plethora of ethical commitments, most of which i assume would also be advocated here such as animal rights, organic(animal) farming, endangered species protection, enviroment protection, human health.
the first fallacy is that you(appear to) claim depopulation is possible.
if this were true and more so it were imminent, at first i would agree that more effort should be put into the depopulation task as opposed to vegetariansim, as i agree that the 'unnecessary suffering' (i will assume can refer to human suffering, non-human or animal suffering or both) that will end with depopulation will end much more suffering than the suffering inflicted upon an individual eating animals.
which brings us to the second fallacy, which is that vegetarianism is an activity which can take the place of 'real action', which is in this case ending overpopulation.
vegetarianism cant be a surrogate activity because it isnt an activity. its simply a diet.
therefore one could practice veganism(a lifestyle excluding animals or animal products for food or clothing or any other purpose) whilst at the same time advocating depopulation.
our future and future itself is inherently uncertain. depopulation can be contrasted with a plethora of modern utopianist ideologies: communism, anarchism, stormfront fascism, 'anus ideology', neo-luddism, green anarchy, liberalism, we could have a nuclear apocalypse or alien invasion.
what is certain is that in this present time, eating a Big-Mac or organic beef is supporting deforestation and the destruction of our enviroment. its playing your part as one of six billion that have brought earth to its current state. this isnt an ethical concern, this has nothing to do with a moral crusade. stripped bare this is one thing- it is science, it is truth.