An event such as a large volcanic eruption, nuclear winter, and asteroid/comet impact has the potential to seriously reduce incoming sunlight, impacting the global climate, and 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; however, this requires seaweed to be cost-effective, which has not yet been assessed. Here, we estimate the economic viability of producing Gracilaria Tikvahiae seaweed under the climatic conditions of a severe 150 Tg nuclear winter, as a benchmark. To do this, we incorporate projected yields and estimated costs under either a capital-intensive or labor-intensive model, including drying, assuming sales only occur in the initial 7 years when food prices would be highest. Overall, we find that seaweed costs would range between $ 400 and 450/dry tonne for the lowest cost clusters, and could potentially be produced in significant quantities, up to 250 million tonnes annually. Given the rise in food prices expected post-disaster a scaleup in seaweed would likely be justified, and could support global nutrition, either via direct consumption or when used as animal feed.

Nuclear war could inject millions of tonnes of soot into the stratosphere, cooling the Earth and devastating crop yields. We assess crop relocation—switching which crops are grown where—as an adaptation strategy. Using the Mink crop model, we simulate six major crops under three nuclear winter scenarios (16, 47, and 150 Tg of soot). Without adaptation, global caloric production falls 23%, 53%, and 85% respectively during the worst year of each scenario. We find that mild cooling scenarios favor expanding high-calorie warm-season crops like rice and maize, while severe scenarios require extensive conversion to cold-tolerant crops like rapeseed. In the extreme 150 Tg scenario, crop relocation could double food production compared to current planting patterns. While insufficient to prevent widespread famine in severe scenarios, crop relocation has the potential to save billions of lives.

Purpose: An abrupt sunlight reduction scenario (ASRS) can be triggered by a nuclear war, a large volcanic eruption, or an asteroid strike, resulting in global agricultural collapse. A wide portfolio of resilient food interventions has been developed to address these issues, but even if they succeed in providing sufficient food energy for the global population, economic inequality could still result in fatal malnutrition in low-income countries (LICs). Methods: Low-cost diets (<$1/person/day) based on ASRS-resilient foods were optimized to reduce malnutrition with sufficient energy intake. The generated dietary combinations were compared to dietary guidelines. Results: The estimated diets were insufficient to achieve balanced diets, resulting in widespread malnutrition. We find that not only continued international trade but also significant food aid is needed to prevent widespread LIC starvation in a severe ASRS. Severe nutritional deficiencies are present: at the onset (Period 1), vitamins A, E, D, C, B3, B5, calcium, zinc, iodine, and selenium; and in the longer term (Period 2), vitamins E, D, K, B5, B6, B12, zinc, and selenium. Seaweed and single-cell proteins are resilient foods that contain notable quantities of many of these; however, large intakes of these are likely to be unfeasible without extensive processing. Conclusion: To reduce the risk of malnutrition and mass starvation in a severe ASRS, LICs would need to develop the capability to ramp up resilient food production internally, perhaps through international cooperation, and/or establish international trade agreements for food and supplements in case of a disaster. Otherwise, if a global food shock occurs, they risk being left dependent on the mercy of catastrophe-stricken, wealthier nations.

In the eventuality of a major volcanic eruption or nuclear war, particles would accumulate in the stratosphere and reduce sunlight, potentially altering climate conditions severely and decreasing crop yields. Mass starvation could be prevented with the help of resilient foods, such as transforming natural gas into protein, wood into sugar, and relocating crops. One intervention not yet analysed is expanding cropland area by converting other types of land, such as pasture and second-growth forests into land that could be cultivated. We find approximately 515 million hectares would be fit for cropland expansion during a catastrophe. Three land-clearing scenarios were explored: the global-equipment-sharing scenario, in which the area fit for expansion is cleared in 12 months, feeding 39% of the global population by the end of the first year after the catastrophe; the no-equipment-trade scenario, in which 442 million hectares of land are cleared in 7 years, feeding 20% of people by the end of the first year, and the export-pool-equipment-trade scenario, where the supply of extra machinery to a few countries allows for the clearing of 511 million hectares in 7 years, feeding 27% of people by the end of the first year. This project shows the potential to mitigate starvation during catastrophes. By sparing old-growth forests, the impact on biodiversity would be limited and could mitigate desperate humans from hunting species to extinction.

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.

An abrupt-sunlight-reduction scenario combined with a catastrophic collapse of electricity/industry has the potential to disrupt food production and distribution worldwide, creating widespread food insecurity. This paper explores the potential of animal draught power to cultivate current cropland and expand cropland area in each country with winter wheat during an abrupt-sunlight-reduction scenario with global collapse of industry. For a 150 tera-gram soot injection with no fertiliser application, the country-level allocation of draught animals allows for the global cultivation of over 700 million hectares (Mha) of current cropland, and expansion of global cropland area by 120 Mha, mostly focused in tropical regions of the globe. Over the course of seven years, over 8.3 billion tons of wheat are produced globally, 25% of which is fed to working animals, while the remaining surplus is used to meet human calorie demand. Although enough wheat is eventually produced to meet 80% of the human global calorie demand, animal demand and trade collapse only makes it possible to meet 30% of the global calorie demand. This presents outdoor agriculture and cropland expansion as viable and sustainable methods to mitigate starvation and prevent animal extinction in a catastrophe in some select countries.