The duty to know: monitoring, reporting and verification as an obligation of due diligence in the legal protection of blue carbon ecosystems

Blue carbon ecosystems, comprising mangroves, tidal marshes and seagrass meadows, are increasingly enrolled in State climate strategies, yet the legal basis of their protection under international law remains insufficiently theorized. Blue carbon protection has become an evidentiary problem before it is a substantive one: international law now protects these ecosystems principally by obliging States to know their condition, so that protection is conditional upon a State’s capacity to generate legally cognizable proof, a relationship termed here the epistemic conditionality of blue carbon protection. Combining treaty interpretation under Articles 31 and 32 of the Vienna Convention, analysis of recent jurisprudence, and comparative normative mapping across three regimes, the article advances three claims. First, monitoring, reporting and verification (MRV) is not merely a climate policy technique derived from Article 13 of the Paris Agreement but, following the 2024 and 2025 advisory opinions of the International Tribunal for the Law of the Sea and the International Court of Justice, is the operational content of binding obligations under Articles 192, 194 and 204 to 206 of the United Nations Convention on the Law of the Sea, which are not discharged by compliance with the climate treaties. Second, the BBNJ Agreement, in force since 17 January 2026, modernizes that architecture and, through Article 28(2), reaches activities within national jurisdiction. Third, because verification capacity is unevenly distributed, epistemic conditionality inverts common but differentiated responsibilities, transferring protective benefit towards States able to afford proof. It proposes a doctrinal reconstruction: Article 204(2) as a continuing surveillance duty; Article 205 publication as distinct from transparency reporting; capacity building under UNCLOS Part XIV and BBNJ Part V as a corollary of the duty to know; and admissibility criteria for algorithmically derived earth observation evidence, by extension of the Pulp Mills line.