For global catastrophic risks the costs of food storage become impractical for most of the population  and for some such catastrophes conventional agriculture would not function due to the loss of a large fraction of sunlight (e.g. during nuclear winter or a supervolcano). In such situations, alternative food is necessary, which is converting natural gas and wood fiber to human edible food.
Some preppers have considered ramping up efforts since President Obama's re-election last week, convinced it means the economy will soon collapse in a cascade of debt. Some are convinced Iran or another enemy is developing an electromagnetic pulse weapon that would wipe out the power, communication and transportation grids, rendering useless any device with a microchip.
The present disambiguation page holds the title of a primary topic, and an article needs to be written about it. It is believed to qualify as a broad-concept article. It may be written directly at this page or drafted elsewhere and then moved over here. Related titles should be described in Survival, while unrelated titles should be moved to Survival (disambiguation).