Having our kelp and eating it too: Minimising trade-offs from seaweed farming

Seaweed farming is promoted as a facet of the Blue Economy that may provide food, support local livelihoods, bolster marine biodiversity, and sequester carbon. While the potential for each of these benefits is often studied in isolation, here we explore the potential for ‘holistic’ management, which realizes all four benefits simultaneously. Applying a stock and flow model to different environmental and socio- economic scenarios, we simulate ten years of operations on a one-hectare kelp (Macrocystis pyrifera) farm. We explore trade-offs among the food, livelihoods, marine biodiversity, and carbon sequestration benefits of each scenario to identify the management conditions under which holistic seaweed farming can be achieved. Our results demonstrate that holistic seaweed farming is possible under many – but not all – scenarios, and that holistic management is distinct from management that prioritises maximising any single benefit, frequently requiring a reduction in financial benefits to maintain others. Proper farm placement and robust management in marine environments will be critical for seaweed industries to support multiple sustainable development objectives at once.