If we actually just ate free-ranging, naturally occurring herds, then it wouldn't contribute to climate change. What contributes is clearing 70% of Brazil to raise imported cattle at a population density hundreds to thousands of times what they would ever achieve without feedlots.

A push toward grass-fed beef is fine, but you can't feed the world by eating grass-fed, local food only, nor organic, nor non-GMO, nor even sustainably raised. There isn't enough of it.