Teleconnected SARgassum risks across the Atlantic: building capacity for TRansformational Adaptation in the Caribbean and West Africa (SARTRAC) In most small islands and many coastal developing countries, the majority of settlements, government, transport and communications infrastructure are located in the coastal zone. Access to the coast allows access to natural resources (e.g. fisheries), transport, recreation, as well as supporting tourism - on which many low and middle income countries depend for employment and income. In the Caribbean, climate change is bringing sea level rise (affecting coastal erosion), warmer seas (associated with coral bleaching), decreased rainfall (affecting agriculture) and the risk of stronger tropical cyclones, for which islands are preparing. These are the known risks and disaster risk reduction measures are often quite advanced e.g. tropical cyclone early warning systems and coastal erosion management. New risks, which have the potential to create significant economic and social damage are only now starting to be documented. These risks are far less well understood, and include large ocean waves from distant sources, transcontinental dust clouds, invasive species moving across boundaries, and the spread of aquatic pathogens. In this latter group is the emergence of very large quantities of Sargassum seaweed inundating beaches of the Caribbean, Central America, and West of Africa since 2011. Such massive and recurrent inundation events are known as golden seaweed tides, with seaweed piling up to 3m high on beaches. The Sargassum decays shortly after reaching the shallow areas and beaches. In the decay process Sargassum consumes oxygen out of the surrounding water, killing fish and other marine creatures, and releasing hydrogen sulphide gas - causing human skin irritation and respiratory problems, and an unpleasant smell. The Sargassum stranding events are unpredictable, but can have major social, economic and environmental impacts. In the SARTRAC project, UK researchers are teaming up with partners in the Caribbean and West Africa to build capacity within the Caribbean and West Africa to answer a number of questions: why did the Sargassum start to mass produce in 2011? Are the large quantities of Sargassum in Spring/Summer, the new 'normal' for the Caribbean and West Africa? What are the trend projections for the Caribbean and West Africa? Can Sargassum stranding predictions be delivered at the local scale and in the short-term? What are the long-term economic and social impacts of the Sargassum strandings? What are the best methods for managing the strandings and are there opportunities for equitable resilience from re-use of the seaweed? Why are communities not already re-using the seaweed - what barriers exist? What are the success stories about re-use, how did they occur, and how transferable are the lessons learned? What are the opportunities for and barriers to regional governance of the Sargassum issue? SARTRAC will address these questions using a multi-disciplinary capacity-building approach to research on: drivers of the growth of the seaweed; risk communications; monitoring and early warning systems; opportunities for re-use of the seaweed; and the opportunities for affected nations to work together to develop regional responses and trans-regional support. By combining knowledge and skills from a range of disciplines and organisations, we can approach these questions from multiple perspectives to gain a more complete understanding. Our approach also encourages the view that opportunities exist from seeing Sargassum as a newly available economic resource. All research will be delivered through a transformational adaptation lens driven by the project PI, i.e. all researchers will be tasked with ensuring that all outputs contribute to the equitable resilience of the poorest groups affected by the Sargassum stranding events. The Global Challenges Research Fund (GCRF) supports cutting-edge research to address challenges faced by developing countries. The fund addresses the UN sustainable development goals. It aims to maximise the impact of research and innovation to improve lives and opportunity in the developing world.