Those 30% you're talking about is not the only land your cattle herds need ... there is also corn/seeds/alfaalfa etc. produced somewhere.
Beef needs 120x more land than plant-based foods for the same amount of calories.
Western countries are a model for developing countries. If we base our diets on meat/dairy, they will want the same. We're developed, we have to set a positive/meaningful example.
We would need several Earths to feed the world same diet as westerners eat. It's simply short-sided and selfish to insist upon current practices to the detriment of everybody else (& Earth & wild animals & biodiversity etc.).
