Most of the vegan food we grow is fed to animals, so we can eat them. Feeding and housing animals for food consumption purposes requires 83% of our total farmland, but produces only 18% of our calorific intake.

If the world went vegan, we'd only use 25% of the farm land we currently do, meaning we don't need to use that "difficult to farm" land.

Unfortunately there is literally no valid argument against veganism. If there were, I wouldn't be vegan.