The term "food miles" is the distance from producer to consumer. Since the era of globalization, these food miles have seen a huge increase. What's the issue with that? Well, most transported goods are through ship or air freight. Most foodstuffs with short shelf lives like some fresh fruits exclusively use plane for long haul freights. This encourages even more fossil fuel use. The solution, buying local goods (which you already mentioned) seems like a small thing to do, but reduces these food miles and emissions significantly. I understand that some foodstuffs may not be able to be grown in the area you reside in (I live in the UK, so no exotic fruits grow naturally) but certain seasonal goods should be bought locally when possible. I try to keep my sources of food local, but it can be easier said than done sometimes