IMHO, there are quite a few reasons small "organic" (certified or not) farms like our CSA are more sustainable:
- Small scale focuses more on adapting crops to the land rather than adapting land to the crops (using fertilizer, pesticides, herbicides, irrigation, etc.)
- Crop rotation allows the land to produce more yield in the same space without chemical augmentation
- Reduced emissions from transportation (the farm is about 10 miles away)
- Fresher means better taste, so we eat more vegetables—and therefore less meat; and we also throw away less food (especially since our CSA uses a points system that allows us to choose veggies we're more likely to eat)
- Reduced packaging use
- No treatments required to preserve freshness (I know someone who has a severe intolerance for corn who has to be extremely careful with fresh vegetables, as they're often sprayed with a corn-based preservative)
- More genetic variety, since freight-tolerance isn't nearly as important
