Additionality Revisited for Blue Carbon Ecosystems: Ensuring Real Climate Mitigation

作者：Phillip Williamson, Catrina Gore, Sophia C. Johannessen, Erik Kristensen, Axel Michaelowa, Faming Wang, Jingfan Zhang · 发表于：Global Change Biology · 年份：2025 · DOI：10.1111/gcb.70181 · 被引用次数：10 · 研究领域：Coastal and Marine Management、Coastal wetland ecosystem dynamics、Marine and coastal plant biology

The rules for international carbon credit markets agreed at UNFCCC COP29 require that emissions credits represent real mitigation (Betz et al. 2022), providing unequivocal and quantifiable climate benefits. The concept of additionality is crucial in this regard, demonstrating that credited CO2 removal or emission reduction would not have happened without the sale of the carbon credits (Michaelowa et al. 2019). Whilst anthropogenic enhancement of biological CO2 sinks is eligible for the carbon market mechanism under Article 6.4 of the Paris Agreement, the rules exclude “natural CO2 uptake not directly caused by human activities” (https://unfccc.int/sites/default/files/resource/A6.4-STAN-METH-002.pdf), as also excluded from reputable voluntary carbon markets. Houston et al. (2024) assess carbon credit potential and additionality for coastal blue carbon ecosystems (BCEs, comprising saltmarsh, mangrove and seagrass habitats), focusing on the problem of allochthonous carbon, originating outside these ecosystems. We welcome their discussion of this issue; nevertheless, we dispute their premise that protecting stored carbon in BCEs is generally additional and reject their recommendation that, in the absence of site-specific information, allochthonous organic carbon should be included in the calculation of carbon credits. We recognise there is greater theoretical potential for carbon release due to loss and degradation of BCEs than for carbon gain by their restoration, at least on a ...