Although I'm not a devout local-vore, I do prefer to eat locally. In terms of meat and poultry, buying locally allows me to know what the birds/beasts were fed, whether they were shot full of antibiotics, that sort of thing. In terms of fish, local means fresh-caught (and "fresh" means within the past couple of hours). But neither of those particular preferences carries much of a lesson with it (unless you want to get into that "teach a man to fish" thing).
The form of local sourcing which teaches lessons best relates to fruits and vegetables. And the reason they're great teachers is that any student worth feeding will immediately taste the difference. Local fruits and veg just taste better.
Local corn, for instance, is sweeter and crisper for any given variety. The sugars in corn start turning to starches soon after the ear is harvested -- the sooner you cook it up, the higher the sugar content and the sweeter the taste. When I was raising my kids, corn on the cob was probably the first food for which they learned to appreciate locality. (I didn't grow corn most years, so it was a question of buying at the supermarket or the farm stand. The kids quickly learned that supermarket corn really didn't taste the same.)
By contrast, tomatoes are probably the fruit/veg (let's not get started on that one) where locality makes the greatest difference in taste. But my kids didn't learn to appreciate the difference until they first saw hothouse ("styrofoam") tomatoes at a restaurant salad bar. Until that point, the only 'maters they'd tasted were home-grown. (In the immortal words of Guy Clark, "there's only two things that money won't buy, and that's true love and home-grown tomatoes.")
All of our tomatoes, and all of our summertime vegetables, came out of the kitchen garden. Herbs we air-dried. Most of the peas, beans, beets and squash we stored for the winter was also home-grown, although most years we supplemented the bean yield with a few bushels from a local truck farm. And we generally bought potatoes, onions and root crops locally. (Except garlic. Like tomatoes and herbs, garlic was a must-grow.) So while my kids ate fresh vegetables from the supermarket, they grew up thinking of those as second-best.
Fruit was somewhat similar. Apples, some berries, and one old tree's worth of pears grow on the farm. Additional pears and berries (especially for canning) were purchased locally, as were most of our peaches, plums, strawberries and cherries. Where my kids first picked up on the difference was in the blueberries -- the wild ones we picked just tasted better than the cultivated berries, even the ones bought just down the road.
It's on peaches, plums and cherries that I probably muddied the message. Those seasons aren't long here in the Northeast, and local production has faded over the decades. I started buying commercial fruit from across the country in order to extend seasonal availability. But now, I don't have a truly local source for any of the three. You do what you can.
People of any age who get exposed to the difference between local and shipped-in produce can usually tell the difference. (That statement is based solely on personal experience. I have absolutely no statistical data on the subject.) Local produce is more likely to be at peak ripeness, it's more likely to be of a variety selected for flavor instead of shipping/handling hardiness, and it's just plain fresher. If my kids hadn't learned to associate "local" with "tasty" when it came to produce, they probably wouldn't readily prefer local grass fed beef or local truly free-ranging poultry.
In fact, if my kids hadn't grown up on local produce, they probably wouldn't be so sensitive to how food tastes. None of them is particularly a food snob, but they dislike industrialized sustenance ("fast food", most industrially prepared foods, etc.) and they notice (and sometimes report back) when something has been created from low-quality ingredients.
Kids who grow up appreciating food and understanding where it comes from just naturally understand why ecological conservation and sustainability are important. Kids who grew up thinking that food is defined by what comes from the supermarket or the deli in plastic packages seem to be more ambivalent about nature. And less discriminating about what they put in their mouths. I'd like to think that Greenback can play a role in addressing the former by getting them to think about the latter.