Is local food always better?

Local food has become a new trend, and probably not a bad one. But unlike all the positive press for it, I assume it isn't always better. So I started looking to see if I could find more details about when local food is better and when it isn't. I did find this article by The Sunday Times. Except for this article and a few tidbits here and there, could not find much beyond the same mantra we hear over and over again that local food benefits local economies and uses less energy in transportation. And if all else is equal, then local food should be better. Actually, supporting local businesses of all sorts, not just food, should help the local economy. But I guess I am more interested in whether local food is greener.

Reasons local food should be greener:
-Less energy transporting food from growers to people
-If you have a backyard and are using rainwater (or are watering your garden instead of grass), then most of the energy is your own sweat and there aren't transportation costs beyond the initial supplies
-Possibly less packaging when bought at the farmers market

Reasons local food may not be greener:
-Foods grown may not be adapted to local climate and take more resources to be produced locally (e.g. shorter growing seasons may require more fertilizers, greenhouses)
-Where you live may be environmentally sensitive, so growing certain foods could take away precious resources (e.g. water)
-If local growers are smaller scale, they may actually be less energy efficient at producing and transporting food (and eliminate any potential energy benefit of growing locally)
-The details of meat: if it's local, are they transporting the feed for the animals? This might be more energy than just transporting the animals (though from what I understand most meat is not produced where the feed is, so maybe free range grazing animals are best, and better than worrying about the meat being produced locally, or of course, being vegetarian)
-If you are choosing conventionally produced local foods over other organic foods, then the food uses more energy because of the energy costs from producing the fertilizer and pesticides
-You need to factor in the energy associated with getting smaller amounts of food to the farmers market, and getting yourself to the farmer's market (I am assuming it is an extra trip since I know I still have to go to the grocery store)

One reason I was interested in this topic is that local food has been catching on in Austin, and I wonder with Austin being drought-prone and already strapped for resources, what the local food movement is going to do. I would like to see the city require water harvesting systems so that they aren't taking water from the aquifers. I would like this required for everyone watering their lawns too. It's not that the area couldn't sustain any local food, there has always been local, but the population of the Austin area is probably already unsustainable for the amount of resources we consume. From what I understand (although I couldn't find a link for this) the water laws in Texas were written based on years of above average rainfall, which means municipalities use unrealistic numbers when calculating what kind of water pressures the city can sustain.

To sum up my opinion on this, I think the local food trend overall is good. I think there are a lot of other things we also have to consider, and if we want to eat locally we need to be willing to change the way we eat to fit the foods that grow in that region as opposed to trying to grow everything everywhere. I also think that choosing to support a local economy that is a local green economy will lead to a local economy that is more sustainable-both in the economic and ecologic sense.