Blue Carbon: Challenges and Ways Forward for Carbon Accounting in Marine Environments
A recent study titled Counting (on) blue carbon—Challenges and ways forward for carbon accounting of ecosystem-based carbon removal in marine environments by Nadine Mengis, Allanah Paul, and Mar Fernández-Méndez highlights the need for negative emissions via carbon dioxide removal (CDR) measures to reach ambitious mitigation goals. In particular, ecosystem-based CDR measures are currently the focus of national net-zero strategies and novel carbon crediting efforts.
Blue carbon dioxide removal (blueCDR) options are anthropogenic activities that aim to enhance such ecosystem-based carbon sinks in the marine environment. The protection and conservation of existing marine ecosystems that naturally sequester carbon, does not qualify as CDR.
Using blueCDR as an example, the study highlights key challenges concerning the monitoring and evaluation of marine carbon fluxes for carbon crediting. Challenges specific to ecosystem-based CDR measures are:
- The definition of baseline natural carbon fluxes.
- Clear anthropogenic CDR signal attribution.
- Accounting for possible natural or anthropogenic disturbances of the carbon stock and hence an assessment for the durability of the carbon storage.
In addition, the marine environment poses further monitoring and evaluation challenges due to:
- Temporal and spatial decoupling of the carbon capturing and sequestration processes.
- Signal dilution due to high ecosystem connectivity.
- Large pre-existing carbon stocks which makes any human-made increase in carbon stocks even harder to quantify.
To increase the scientific rigour and ensure additionality behind issued carbon credits, the authors support the current trend of focusing monitoring efforts on carbon sequestration rather than on capturing processes, and on establishing a baseline for natural carbon sequestration in diverse marine ecosystems. Finally, they believe that making carbon credits subject to dynamic adjustments over time will increase their credibility.