Predicting Climate Mitigation Through Carbon Burial in Blue Carbon Ecosystems-Challenges and Pitfalls

Area of Science:

• Marine ecology
• Climate science
• Biogeochemistry

Background:

• Blue carbon ecosystems (BCEs) like mangroves, saltmarshes, and seagrasses are vital for carbon sequestration.
• Accurate assessment of long-term carbon storage is crucial for evaluating their climate mitigation potential.

Purpose of the Study:

• Critically evaluate the definitions, measurement approaches, and time scales of blue carbon.
• Assess the reliability of current methods for estimating blue carbon sequestration in BCEs.
• Determine the actual climate mitigation potential of blue carbon, considering emissions and storage limitations.

Main Methods:

• Analysis of sediment carbon inventories and accretion rates.
• Application of carbon mass balance models.
• Long-term decomposition simulations using a 3-G exponential model.
• Evaluation of greenhouse gas (GHG) emissions (CH4 and N2O) from BCEs.

Main Results:

• Current inventory and mass balance methods overestimate blue carbon sequestration by 3-18 times.
• Sediment mobility and bioturbation invalidate long-term tracer methods (e.g., 210Pb).
• Mass balance models struggle with climatic variations and incomplete carbon budgets over >100 years.
• GHG emissions (CH4, N2O) from BCEs can negate or exceed carbon sequestration benefits.

Conclusions:

• Published estimates of blue carbon sequestration in BCEs are likely significant overestimates.
• The long-term climate mitigation potential of blue carbon is questionable due to methodological limitations and simultaneous GHG emissions.
• Rethinking blue carbon assessment is necessary for accurate climate policy and conservation efforts.