Both, kind of. You are right that consuming grass fed meat exlusively does not hurt the environment that much. At the same time, you still need to think of the rest of the world. If CAFOs were abandoned and everyone switched to grass-fed beef then consumption would still have to be decreased just to match supply. Prices would rise as a matter of course.

I've been thinking about these topics a lot lately and we clearly have a problem with the continuing growth of populations everywhere. As it seems now it is currently impossible to feed everyone sustainably. That is, as soon as fossile fuels run out and synthetic fertilizers are no longer available, we will have a problem.

To keep this paleo: Apart from eating less meat there is still the option of just buying less and throwing less away. Actually, no food should be thrown away. Yet 50-60% of all food in western countries gets thrown into dumpsters. I hate the phrase but here goes: Throwing food away is NOT paleo.

Veg*anism just pushes the killing to where it cannot be seen. The problem of overpopulation is that there are too many people after Earth's limited resources - not that they are eating meat per se.

From a paleo perspective, don't waste food. Eat all the animal (seek out obscure cuts from your butcher), and remember that a carcass has wider utility - although implementing this is 'hardcore'!

Also aim for indigenous meats and wild game as (particularly the former), will support native habitat.

12. Reduce Your Meat Consumption.
Livestock production accounts for about 18 percent of all human-caused greenhouse gas emissions and accounts for about 23 percent of all global water used in agriculture. Yet global meat production has experienced a 20 percent growth rate since 2000 to meet the per capita increase of meat consumption of about 42 kilograms.

http://www.motherearthnews.com/nature-and-community/simple-steps-going-green-zwfz1112zhun.aspx?page=5

I understand the point, but I wonder about the quantitative effect reducing the purchase of some meat once a week actually has. Possibly it is more sustainable to purchase a whole cow for two months, rather than repeatedly buying sirloin steak daily where multiple animals are involved.

Eating select cuts the whole time needs multiple animals, and possibly wastes a lot of space and the animal. (Though we then have to take into account that even though we don't eat the whole animal, the whole animal is used in a large number of industries and the products we use.)

Maybe we should (as higher meat eaters) take the time to find a good organic butcher/farmer, and find out how he runs his farm. Then purchase as much of a single animal as we can. This way we are supporting someone (and his family) who is directly managing his local ecosystem with good stewardship and respect, and we are maximising the utilisation of a single animal for food (as food is the context here).

Just thinking about this as I write, maybe the point should actually be about eating more meat (as in the whole animal) rather then eating less meat. To me the more I think about it the more sustainable it seems to be to me. This seems to me to be the best of both worlds.

Now this is easier said then done, as I personally want to eat meat but now I realise need to eat "more" of it, without so much picking and choosing.