I’ll be giving several talks over the next few months on the Real Vegan Cheese project. I’m doing some of my own background research to supplement what I have from the group and I came across this interesting paper:

Food-Miles and the Relative Climate Impacts of Food Choices in the United States

The finding from this paper is that 83% of the greenhouse gas emissions caused by our food come from the production of that food. Transportation is only a small part and much of that is upstream of the farm (that is, equipment, fertilizer and feed delivered to the farm). Red meat is by far the most GHG intensive to produce, followed by dairy.
This means that (not even counting antibiotics and runoff from animal agriculture), it is environmentally better to eat vegetables and grain grown in another hemisphere than it is to eat animal products from a local ranch. (although other meats came out very close to vegetables by most measures).