There are endless reasons to become vegan. The most urgent, to humans, is the fact that meat production produces more global warming gases than all the cars, trucks, trains, ships, planes, on earth- combined (this according to UN and industry statistics).
Another obvious fact is that it's horrifically cruel to the animals. And animals do feel pain, have a sense of self, emotions, etc, just like humans. So causing them unnecessary pain is a true ethical concern.
It is also unhealthy for humans to consume meat and dairy products, and meat and dairy production waste irreplaceable natural resources and feed fewer people than if we simply raised vegan food. Plus, by going vegan, we'd be able to feed the 30,000 impoverished people who die daily due to starvation related disease. Meat production uses more resources and land and yields far less food than farming a vegan diet.
This is NOT opinion, it's all sound scientific fact based on peer reviewed scientific research.
Farming and consuming meat is NOT a sustainable practice, therefor it cannot continue. So, if you care about anything at all, do the right thing and go vegan. Now.
Your body will thank you, the animals will thank you, the planet will thank you, the 30,000 people who starve to death daily due to wealthy western nations growing meat rather than a vegan diet will thank you.
A senior UN official and co-author of a UN report detailing this problem, Henning Steinfeld, said "Livestock are one of the most significant contributors to today's most serious environmental problems". Livestock production occupies 70% of all land used for agriculture, or 30% of the land surface of the planet. It is one of the largest sources of greenhouse gases, responsible for 18% of the world's greenhouse gas emissions as measured in CO2 equivalents. By comparison, all transportation emits 13.5% of the CO2. It produces 65% of human-related nitrous oxide (which has 296 times the global warming potential of CO2,) and 37% of all human-induced methane (which is 23 times as warming as CO2. It also generates 64% of the ammonia, which contributes to acid rain and acidification of ecosystems. Livestock expansion is cited as a key factor driving deforestation, in the Amazon basin 70% of previously forested area is now occupied by pastures and the remainder used for feedcrops. Through deforestation and land degradation, livestock is also driving reductions in biodiversity.