Accounting and monitoring challenges for blue carbon enhancement in national climate policy targets and international carbon markets

“Blue carbon” refers to carbon sequestration in marine ecosystems. While carbon uptake in coastal vegetated areas has been well-studied, emerging techniques to enhance carbon uptake in open ocean environments pose new challenges in terms of accounting and monitoring, reporting, and verification (MRV). Establishing baselines for carbon sequestration is particularly difficult, as the natural ocean sink is influenced by human activities and increased atmospheric CO₂. Furthermore, the durability of biogenic oceanic carbon sinks is uncertain, particularly in the face of climate change impacts. Legal complexities arise due to the transboundary nature of open ocean ecosystems, making it difficult to attribute carbon credits to specific nations. Current MRV methodologies and accounting frameworks do not sufficiently address open ocean blue carbon enhancement. Without robust frameworks and internationally accepted standards, integrating these approaches into national climate policy and carbon markets could lead to overestimating mitigation outcomes. We conclude that governance to incentivize and regulate blue carbon activities should address both climate and environmental impacts and benefits and develop financing models which do not rely on carbon crediting mechanisms.