This is an interesting topic, and I've held off commenting so far. To live off the land (as I assume the OP meant) and live off only veg would be tough - if you've watched the Discovery channel show "Naked and afraid" you'll see folks starving themselves for the three weeks they have to stay in country because they cannot reliably catch enough food and don't possess enough local knowledge to forage enough plant based food to survive comfortably.
If you had enough knowledge of local food sources I think you could survive on plant alone - it may not be a tasty diet but you could do it. But obviously adding in meat to the equation makes a huge nutritional boost. It's all about knowing what foods are available, where and when - the Australian Aborigines are a perfect example of this!
As to the question of if it is possible to live on a vegetarian diet alone, that's a no-brainer - yes. I've lived three quarters of my life as a vegan or vegetarian (even macrobiotic for some years) and I'm healthy and very active. I think you can eat a much more varied and nutritious diet when you have to put some thought into it
Only some thoughts, hope this adds something to the discussion.
