In the fruits and vegetables section at the grocery store, one can find produce from everywhere in the world. Garlic from China, tomatoes from Mexico, berries from the States, sand cherries from the Caribbean, and many more. The first problem with this is transportation. The foods that are grown far away from where you live must be put on truck, planes, trains, in order to get to your local store. So the environment suffers from you buying foods from far away. The produce you eat often will have traveled more than you ever have, and that is not a positive thing.
The next thing to consider about local vs global foods is the freshness of your produce. Fruits and vegetables are usually harvested when they are ready to eat, but if they must then travel long distances before being consumed, they cannot possibly be at their freshest when they finally get to your plate. Companies will sometimes insert chemicals in the produce in order to keep the freshness. So, you will have "fresh" produce with chemicals that cannot possibly be healthy.
In all, the better option is to purchase foods that are grown locally. Farmers' markets are excellent places to find local foods. The next time you go out shopping for food, think about what they went through to get to you. The best part is that foods taste so much better when they are fresh and chemical free.