GMOs are just fine, but the practice of large scale agriculture is problematic. Fossil fuel will likely be in too short of supply to maintain the current system within the next 15-20 years. This means an end to using large machinery to plant and harvest crops as well as an end to using trucks to transport food and other goods. Ports may be able to remain open for some transportation, but infrastructure enabling rapid transportation over land will quickly cease to exist. Working large sections of land with few hands will no longer be possible, either. Doubtless there will come replacements for existing systems, but they will not be gasoline-driven and they will not be as fast. And in the meantime, we either have to come up with a backup plan for the transition period or wing it. I have my backup plan covered, but I strongly recommend you all think of your own precautions.