OlderthanI think it’s one of those things where you just have to chose what you think is the better path.
E.g.
So, farming animals produces a lot of greenhouse gases and uses up land very intensively. So not eating meat is a plus for the environment in that sense.
Locavorism (especially in hilly places where land isn’t suitable for much except grazing) can be lower carbon than Veganism which relies on foodstuffs etc from around the world.
I think the important thing is that people in either of those two camps are consciously choosing to do their best. Both are very different from just mindlessly consuming whatever.
The animal welfare aspect is the whole point for some people, with ecological impact being either of secondary or little concern.
For others, the ecological impact is the primary concern, but animal welfare is something which tips the balance in favour of veganism rather say locavorism.
For others, ecological issues are the whole point and in that case you just need to do the Mathis carbon load.
However, I would say that both ecological and animal welfare approaches can have an important similarity. They can be a rejection of the thinking that says man has dominion over land and animal. That we somehow have an ownership or control of other creatures and entities as an inherent right. Both approaches can be expressions of that, and anything that inculcates that more humble and grateful mindset will ultimately be of benefit to the planet.