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 5 years with conversion of existing vegetation and fossil fuels to edible food.
The writers presents 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. They 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.