If you can't do it all yourself, the next level of thinking is "buy it here".  That applies to locally grown food, as well.

A sustainable local economy doesn't depend upon outside sources for survival.  That means that our area can't be considered "sustainable" if we have to go outside to find something to eat.  That means encouraging, supporting, and buying from local farmers.

Within the farming community, "sustainable farming" generally also means lowering our dependence upon outside sources of fertilizer and chemicals. 

Some of the key tools to achieve this include:
(1) Organic farming practices
(2) Integrated pest management
(3) Erosion control practices