Role of macroalgal blue carbon ecosystems in climate change mitigation

This review explicitly emphasizes the important yet unnoticed potential of macroalgae, such as seaweeds and kelps, as a powerful nature-based solution for climate change mitigation, with greater focus on the Indian Ocean seaweed diversity and efforts towards their conservation and management. Despite the IPCC's recognition of Blue Carbon ecosystems, seaweed ecosystems remain largely excluded from carbon accounting and policy frameworks. Herein, we specifically focus on the immense capacity of macroalgae globally and in the Indian Ocean coastal communities to sequester carbon, support marine biodiversity, and provide a range of ecosystem services. Through comprehensive analysis of existing literature on the primary productivity, species distribution and carbon sequestration capabilities of seaweeds, we highlight their pivotal role in carbon capture and utilization within a circular economy model. This review explores the ecosystem services provided by both wild and cultivated seaweeds, advocating for innovative applications and responsible management practices to maximize their climate mitigation potential. Our investigation identifies significant knowledge gaps and barriers in the conservation of economically significant, dwindling populations of seaweeds in the Indian Ocean and the integration of seaweed ecosystems into blue carbon policies, including the need for standardized classification, valuation, and long-term conservation strategies. Further, we address the impact of anthropogenic activities on wild seaweed biodiversity and the necessity for reliable carbon removal technologies to support seaweed aquaculture beds. This review urges policy reform, increased research and funding to this critical area. We aim to accentuate the importance of a blue economy in establishing carbon-neutral markets and effective climate change mitigation by improving the classification, finance and governance of seaweed ecosystem services. © 2024 Elsevier B.V.