Sorry but being vegan doesn't solve all the world's problems.
There are large amounts of land that cannot be used to grow crops.
Some cultures are defined by their livestock, you would end the way of life for many people.
You have to eat more vegetables to get the same nutrients as you get from animal protein.
You would still need to control pests to protect crops, so what are you going to do with the rabbits you shoot?
How are you going to manage things like deer?
What are you going to feed to babies who cannot be breast fed?
Reducing meat consumption, particularly in the west would probably benefit the world, but not stopping it all together.