Enhancing the beneficial environmental impacts of seaweed cultivation: what do we understand about best practices?

Abstract Seaweed is increasingly discussed as a sustainable biomass source of the future, with applications in agricultural, food and cosmetics products and other areas of the biobased economy. The potential positive environmental impacts of seaweed cultivation have triggered public and private sector interest. This paper outlines the evidence for potential environmental benefits arising from seaweed cultivation focusing on climate change mitigation, biodiversity loss mitigation and improved water quality. Our findings are based on a descriptive literature review, coupled with insights and additional literature established during an expert review meeting. We found that seaweed cultivation can help to mitigate climate change and biodiversity loss and have beneficial impacts on water quality, but management practices may be key to maximizing these benefits and preventing negative environmental impacts. In particular, co-cultivating seaweed in integrated multi-trophic systems can enhance benefits. Other management practices expected to enhance environmental benefits of seaweed cultivation were identified, aligned to recently defined Principles of Restorative Aquaculture, including siting and structure used. Evidence of environmental impacts is often site-specific with considerable variability and uncertainty in the reported environmental benefits, due to the complexity of marine ecosystems and variability in cultivation and harvest practices. Systematic, long-term monitoring efforts are scarce, and more quantitative evidence is needed to support public and private sector decision-making for upscaling seaweed production in support of both bioeconomy and environmental restoration objectives. However, the management principles and practices identified in this paper can be used as interim guidance for decision-making.