The divorce of crops and livestock has made us more dependent on synthetic fertilizer, but that's not a complete fertilizer to provide all the needs. 60% of the ice free land is not suitable for crops. It's not what we call arable land and probably won't be suitable for crops in the near future. These soils are too rocky, too shallow, too steep, whatever it might be to support agriculture or crop agriculture. But they're great for livestock as like a land use that can produce calories; those animals are playing a role in building future soil.