I'm just saying the same applies to eating plants. In fact, if we ate nothing but plants, I suspect there would be very few places left with any trees at all. It would all be fields. Yes, there are some farming practices that are more sustainable than others. The reason we have problems in the heartland as I understand it is because they use the same ground over and over again for crops and strip it of all nutrients, that have to be replaced each year. In fact, the reason it was such good soil to start was because of millions of buffalo pooping on it long ago. So, the logical answer is rotating cows to naturally fertilize the soil and then to crops. It's done in some parts of the world. But the farmers I know are just holding on by the skin of their teeth now. Implementing new practices always takes initial expenses. It seems to me that nowadays it's go big or quit or just hobby farm. The small family farm has a hard time making money.
Another myth is organic is always better for the planet. Organic tends to take more land for the same amount of production, sometimes twice as much land, and it still used animal matter, in most cases, Bone meal, manure, etc. So, the vegan is still eating recycled animal parts, really.
A grass-fed sheep or cow would use the least in resources. It's also not always practical. We kept our cows on pasture in the summer, but they still got some hay when needed and grain. You need a lot of pasture and good pasture for raising on grass. I'm not an expert and I don't have all the answers, but it's not going to all plant-eating.