Michael Hinge , Vasco Amaral Grilo, Florian Ulrich Jehn, Juan Bartolomé García Martínez, Farrah Dingal, Michael Roleda, David Denkenberger

An event such as a large volcanic eruption, nuclear winter or asteroid/comet impact has the potential to seriously reduce incoming sunlight, impacting both the global climate and conventional crop yields. This could have catastrophic impacts on human nutrition, unless the food system can adapt. One possible answer is seaweed, where growth is projected to be less impacted (or even enhanced) by the climate shock due to overturning of the ocean bringing nutrients to the surface. We assess the expected cost of producing dry edible seaweed under the climatic conditions of a severe 150 Tg nuclear winter, using Gracilaria Tikvahiae as a benchmark species. To do this we incorporate projected yields and estimated costs under either a capital intensive or labor intensive model, covering both the cost of cultivation and drying. Overall, we find that seaweed costs would range between $ 400-450/dry tonne for the highest yielding/lowest labor cost clusters, and could potentially be produced in significant quantities even when constrained to shallow waters close to ports. This cost is higher than the current reported ~$300-350/dry tonne price of Gracilaria tikvahiae, reflecting additional capital costs and additional drying requirements during the catastrophe. The cost is also higher than current staple cereal prices on a caloric equivalent. However, given the sharp rise in food prices expected post disaster, it is likely a large scaleup would be justified, offering an important contribution to global nutrition, either via direct consumption or when used as animal feed.