Comment by etrabroline

That land is called marginal land, or pasture. You can't grow crops there economically r do anything else really. Removing the grazing animals from the land changes nothing and does not improve the environment at all. That land would be worthless if not for grazing animals.

I'm not sure there is enough arible land to support the human population without grazing animals. I suspect anything is possible with enough technology and money, but matthewmorgan is correct in being concerned.