I think it might have an impact, just not this much. To put it in perspective by playing with the numbers, the US has a population of roughly 308 million. Let us conservatively assume that roughly 10% of the population is of a similar mindset to us and round the number off at 31 million. Let us further assume that at the other end of the spectrum there is another roughly 10% that have essentially empty refrigerators, call it 31 million as well. We'll place the rest of the population somewhere in the middle and say that they have somewhere between 1 week and 1 month of food on hand.
If these numbers are even close to true, that leaves roughly 31 million people who might panic. Of those, let's get adventurous and say half of those actually listen to the warnings. That leaves 15.5 million people who have empty cupboards and a desire to change their situation.
Each day's worth of stores at 2 meals a day those people purchase represents a total food purchase of 31 million meals worth of food. It doesn't sound like much in the grand scheme of things, but in our JIT supply chain that is set up to minimize loss due to spoilage, 31 million meals is significant. Now what if the numbers held true across the board with the exception of people like us who are already stocked up well beyond 2 weeks? Take us out of the mix and we have roughly 277 million people. Half of those purchasing to build up the pantry would represent 277 million meals worth of food per day they increase their stores. Increases in those numbers would really do a number on supply.
Now even if this is all similar to reality, the hit to the supply chain would be real and significant, but short lived. What's more, many of these people would have a "what have I done" moment as soon as they got home with the goods and would simply live off them for the next 2 weeks. During that time, they would buy little and then go back to their old shopping habits...whatever those might be.
No, I think there is real potential of supply shortages. I also think part of the problem can be traced back to farm subsidies. When it is more profitable to leave land fallow than to put it in production, it would require a fool or a person with an exceptional grasp of the future to plant that ground anyway. Add to that, there has been no real incentive to add significant storage capacity for foodstuffs in the past. Part of the reason the farmers don't grow more is that there literally is no place to put it at harvest and no place to sell it without the bottom dropping out of the prices. Oh sure, the 3rd world could really use the food, but who's going to pay for it. Let's face facts. From those like us who plant home gardens to the family farm to Monsanto and ADM, nobody does it purely for charity. We do it for the supply and cost saving advantages and the professional growers at all levels do it for their living. We might all of us give away part of our harvest for various reasons, but not nearly as much as we keep or sell respectively.