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International audience; Mass human starvation is currently likely if global agricultural production is dramatically reduced for several years following a global catastrophe: e.g. super volcanic eruption, asteroid or comet impact, nuclear winter, abrupt climate change, super weed, extirpating crop pathogen, super bacterium, or super crop pest. This study summarizes the severity and probabilities of such scenarios, and provides an order of magnitude technical analysis comparing caloric requirements of all humans for five years with conversion of existing vegetation and fossil fuels to edible food. Here we present mechanisms for global-scale conversion including: natural gas-digesting bacteria, extracting food from leaves, and conversion of fiber by enzymes, mushroom or bacteria growth, or a two-step process involving partial decomposition of fiber by fungi and/or bacteria and feeding them to animals such as beetles, ruminants (cattle, sheep, etc), rats and chickens. We perform an analysis to determine the ramp rates for each option and the results show that careful planning and global cooperation could maintain humanity and the bulk of biodiversity. 1. Introduction It is widely assumed that if agricultural production is dramatically reduced over a period of years, this will cause mass human starvation or even extinction. This could be effected by any of six crop-killing scenarios: 1) abrupt climate change [1], 2) super weed [2], 3) extirpating crop pathogen [3], 4) complete loss of bees [4], 5) super bacterium [5], or 6) super crop pest [6], or three sun-obscuring scenarios 1) asteroid or comet impact [7], 2) a super volcanic eruption 1 [7], or 3) nuclear winter [8]. The sun-obscuring scenarios are the most challenging to overcome. The penetration of solar energy into our traditionally defined primary (raw input) energy use, through technologies like photovoltaics (solar cells) and solar heating, is only order of magnitude (order) 1% [9]. However, if we define primary energy more broadly to include the solar energy required to grow humanity's food, feed and forest products, the solar fraction of primary energy is closer to 99.9% [9]. Thus, if the sun were mostly blocked for a period of years it would seem to be an insurmountable task to replace this solar energy, which is three orders of magnitude greater than global fossil-fuel energy consumption.