Except for the deforestation needed to increase pasture area and for growing more feed. Destroying habitats and pushing indigenous people further from their homes. Meat on a large scale doesn't work because it is energetically less efficient. Farmed animals produce waste products like methane which are large contributors to global warming. Even if the land used by livestock was completely unusable for other purposes, they would still be polluting the environment through eutrophication and destroying locally endangered species.