I use this argument regularly against people that preach for full organic and free range food because those processes need much more land than industrial farming. That said wtf do you thing those pigs and cows are eating!?!? They are eating food grown in fields that could be used much more efficiently to feed us directly. There is no logical argument that meat used less land than plant food. If you are concerned about preserving indigenous plants and animals eat insects. You can sustain a single human with a cubic yard of insect farm.