An ecosystem of carbon dioxide removal reviews – part 2: CO2 removal via blue carbon ecosystems

Abstract

Carbon dioxide removal (CDR) is essential for achieving global climate goals, such as those outlined in the Paris Agreement. This systematic review investigates the current state of CDR through management pathways for blue carbon ecosystems (BCEs) and assesses their role in the global CDR portfolio. This article analyzed 2622 peer-reviewed and gray literature articles out of 13 859 identified using a machine learning-assisted review process published through November 2025. The review focuses primarily on mangroves, seagrass meadows, salt marshes, and macroalgae. These ecosystems collectively sequester approximately 270 MtC year⁻¹ (106–516) to various long-term sinks, with macroalgal export to deep ocean environments and dissolved inorganic carbon (DIC) pools contributing the most. BCE conservation and restoration offer potential CO₂ emission reductions between 60–96 MtC year⁻¹ and removals between 21–448 MtC year⁻¹ by 2050, though these estimates remain uncertain and vary widely in cost and feasibility. The study highlights significant gaps in integrating BCEs into climate policy, particularly regarding their representation in national inventories, carbon accounting frameworks, and cost assessments. It emphasizes the need for multi-benefit strategies that balance carbon sequestration with local livelihoods and ecosystem co-benefits. Translating these insights into practice will require that climate policy frameworks explicitly incorporate blue carbon pathways through combining carbon sequestration with financial reward systems and additional incentives to realize co-benefits and interaction effects that would also increase social acceptance.