The constant plowing and addition of chemical fertilizers and pesticides and herbicides to continue this mono-culture farming ritual we perform today is far more harmful (my opinion) on the environment than grazing cattle on the land. The cattle return a large amount of nutrients to the soil, and the land can be re-used for other animals or crops between letting the field go fallow for the next round of grazing. No real "inputs" are needed for the cattle, other than water, and we can find great permaculture ways to provide them with water/food that restores the land instead of destroys it.