Island refuges for surviving nuclear winter and other abrupt sunlight-reducing catastrophes.

Some island nations in the Southern Hemisphere might survive a severe sun-reducing catastrophe such as nuclear winter and be well placed to help reboot-collapsed human civilization. Such islands must be resilient to the cascading effects abrupt sunlight reduction scenarios (ASRS) would impose beyond the impacts on agricultural systems. We aimed to identify island nations whose societies are most likely to survive nuclear winter or other ASRS. We also aimed to conduct a case study of one island nation to consider how it might enhance its resilience and therefore its chance of aiding a global reboot of complex technological society. We performed a threshold analysis on food self-sufficiency under severe nuclear winter conditions to identify islands. We then profiled each island across global macroindices representing resilience factors reported in the literature. We undertook a case study of the island nation of New Zealand. The island nations of Australia, New Zealand, Iceland, the Solomon Islands, and Vanuatu appear most resilient to ASRS. However, our case-study island nation of New Zealand is threatened in scenarios of no/low trade, has precarious aspects of its energy supply, and shortcomings in manufacturing of essential components. Therefore, inadequate preparations and critical failures in these systems could see rapid societal breakdown. Despite some islands' favorable baseline conditions and apparent food security even in a severe ASRS, cascading impacts through other socioecological systems threaten complex functioning. We identified specific resilience measures, many with cobenefits, which may protect island nodes of sustained complexity in ASRS.