"Within a generation we have lost our unmodified seed stock. You can still get them, but not in a large enough quantity to feed our neighbors."
Citation needed.
I call bullshit on this one. Yes Monsanto delivers a scarily large portion of the worlds seed stock, but not all of it is modified (they sell more than one variety) and they don't deliver all of it. There's still a lot of it around. If a large proportion of farmers ever decides to switch back it'll probably be about a year to 2 years before a full switch can be made by all, but it's most certainly NOT out of the question.