Ambition Disparity Reveals Unlocked Mitigation Potential for Blue Carbon in the Paris Agreement

Blue carbon ecosystems, despite their significant climate change mitigation potential, remain underrepresented in the Paris Agreement. Only 20% of the blue carbon-holding countries have incorporated them into National Inventory Reports (NIRs), and 46% have included them as mitigation targets in Nationally Determined Contributions (NDCs), with Non-Annex I countries accounting for the majority of these inclusions. Full protection and restoration of blue carbon ecosystems could sequester up to 122.3 GtCO₂e (95% CI: 84.03 – 160.57 GtCO₂e) by 2050—effectively offsetting 10 years of the world's current land cover change carbon footprint. However, only 25.52 GtCO₂e (95% CI: 17.52 – 33.48 GtCO2e), i.e., 30%, of their mitigation potential is currently pledged. Non-Annex I countries have committed twice (37%) the potential of Annex I countries (16.4%), highlighting both the opportunity and the disparity in policy uptake relative to mitigation potential. We demonstrate that NDCs can be utilised to incrementally integrate blue carbon, transforming disparity into strategic entry points, catalysing more ambitious climate targets while safeguarding coastal resilience.