An event like this, or anything else with a significant impact on food production is something many people should be absolutely prepared for. A bulk of countries, including where I live, are completely dependant on importing food. What do you think will happen if the net exporters experience a global supply crisis? Always be cognizant of events that are improbable but have a high impact on survival.
Is it feasible for many countries - particularly small, densely populated ones - to be self-sufficient in food? In the UK, at least, I'm not sure there's physically enough space to farm enough food to supply the population. About 50% of food is imported and basically all the agricultural land is already used.
Unfortunately a trend I'm seeing in my country is that some people are calling for crippling the in-country farming industry because it is "inefficient" due to subsidization and would be cheaper to import food from elsewhere. The trend should be upwards, reducing dependence on importing and focus on local produce. Gut feeling is also that it would be more ecologically efficient although I don't have any concrete numbers on it.