Moreover, all these calculations of how much energy is required to grow meat fall flat when you consider grass-fed beef & pastured chickens (a la Saladin); unlike corn-fed beef, grass-fed beef can be self sustaining & actually rejuvenate the land.

Choosing veganism over corn-fed carnivory is the lesser of two evils, only because veganism requires less monocropping. However, at best it can only slow--never reverse--environmental destruction (without animals, the NPK source is petroleum).

From an environmental standpoint, the disease is "growing crops without animal input," and corn-fed beef is merely a symptom.

Ironically, the only way to turn veganism into a closed system is to avoid the large-scale monocropping of grains and re-introduce animals for a nitrogen source.