It is widely assumed that if agricultural production is dramatically reduced over a period of years by a super volcano, asteroid or comet impact, nuclear winter, abrupt climate change, complete loss of bees, super bacterium, extirpating crop pathogen, super crop pest, or super weed, there will be mass human starvation or even extinction. However, we make the order-of-magnitude technical argument that the caloric requirements of all humans (and sufficient populations of many other species) could be satisfied for a half decade by making much of the vegetation edible. We show that these could be ramped up before existing food stocks are depleted. Further work is required to confirm that the diet would be adequate, potentially by ramping up production of supplements. Given the non-negligible chance that one of these disasters may strike each year, risk analysts and policymakers should be aware of these emergency food sources. In addition to revising damage estimates downward, this analysis also suggests possible preparations to make the transition more easily, such as demonstration projects and the creation of emergency plans. We believe that the chance of mass starvation would be significantly reduced with awareness of these backup plans.