Assessing the Potential Conservation Role of Other Effective Area-Based Conservation Measures in Relation to Seaweed Farming

Other effective area-based conservation measures (OECMs) offer opportunities to advance the Convention on Biological Diversity's ‘30 by 30’ conservation targets, while recognising greater stakeholder diversity, including industry, Indigenous peoples and local communities. Although aquaculture sites are generally excluded from OECM consideration, reported low environmental impacts and biodiversity benefits of low-trophic species, including seaweeds, have prompted interest in their potential as regenerative sites or OECMs. We reviewed over 70 published studies assessing the biodiversity impacts of nearly 90 seaweed farms globally, to determine whether there was evidence that farms could meet the OECM screening criteria set by the International Union for Conservation of Nature World Commission on Protected Areas (IUCN-WCPA). Fewer than 4% of the farms assessed qualified as potential OECMs, despite over 50% not occurring in protected areas (passing the first criterion). Over 40% of farms did not support important biodiversity values or had negative biodiversity impacts (failing the second criterion). Fifteen per cent of farms were likely to support important biodiversity values; however, many of these occurred within existing marine protected areas (MPAs), preventing them from qualifying. Additionally, nearly 40% of farms had inconclusive evidence to determine the second criterion, highlighting the need for future studies to explicitly apply IUCN-WCPA guidance and for that guidance to be clarified to reduce ambiguity. With over 50 seaweed farming nations worldwide, stronger regulation and support from international bodies and governments are urgently needed to improve the environmental impact of seaweed farming to help meet global conservation targets while maintaining coastal livelihoods and resilience.