Unfortunately powerplants dont graze on a field of grass

A few of things:

1) Even if cows would only eat the grass that was there (and we would not have converted any forest or other vegetation into grazing lands), the methane and CO2 stays in the atmosphere for a long time before being used by plants again, contributing to the greenhouse effect in that time. The reality is, we can only cover a very small percentage of the demand with this "3 happy cows on a vast pasture" phantasy. Most cow feed is planted additionally, often in countries like Brazil, and then fed to the cows.

2) The carbon impact is not the only negative impact of the scale of livestock agriculture we run these days. As it says in the article, another big impact is eutrophication of water bodies.

3) Just basic physics: Livestock agriculture, especially beef, is a very inefficient way of producing protein and calories. Have a look at this data: https://ourworldindata.org/grapher/ghg-per-protein-poore

So, please don't come at me with your cute comments. The reality is that we have too much livestock agriculture. It's not sustainable to feed 8 billion people like this. The scientific consesus is clear on this.