There's an interesting UN report from a while back,
Livestock's Long Shadow [1], that observes that, nowadays, it's not necessarily even ecologically sound to use the grasslands in the first place. A big feature of their findings are that large-scale grazing tends to prevent forests from forming in wetter climates, and contributes to desertification in more arid ones. Both of those consequences have
huge implications if you're worried about climate change.
One of the key goals they set out, aside from getting people to rely less on livestock agriculture in the first place, is to try and convert more of it to CAFOs. Yeah, factory farms are ugly, but they found that it's much more efficient from a land and energy use perspective. As have other disinterested parties. The loudest voices saying otherwise seem to be ones that have a financial interest in selling more grass-fed beef.
A subtext here is that we live in a very different era than the one that the one invoked by more nostalgic approaches to agriculture. Once upon a time, people had no choice but to figure out how to feed themselves off the land they occupied, and nature put much firmer limits on how many people could occupy certain areas. Nowadays, not only is getting food shipped in a realistic option, sometimes it's even the more economical and sustainable one.
1: http://www.fao.org/docrep/010/a0701e/a0701e00.HTM