As you might know, most of arable land (as well drinkable water) nowadays is used for producing nutriments for the livestock. This results in cutting rain forests, degradation of soils and biodiversity, huge waste of drinking water, etc.

Imagine, a time traveler comes from the future and tells us that if we don't reduce out consumption of meat, the world will come to its end in 200 years. Now, guess what most of us will do.