“Coastal wetlands store a lot of carbon in their soils and are important long-term natural carbon sinks, while kelp, corals and marine fauna are not.”
Coastal wetlands outperformed other marine systems in just about every measure. For example, the researchers estimated that mangrove forests alone capture and store as much as 34 million metric tons of carbon annually, which is roughly equivalent to the carbon emitted by 26 million passenger cars in a year. Estimates for tidal marshes and seagrass meadows vary, because these ecosystems are not as well mapped globally, but the total for each could exceed 80 million metric tons per year.
All told, coastal wetlands may capture and store more than 200 metric tons of carbon per year globally. Importantly, these ecosystems store 50-90 percent of this carbon in soils, where it can stay for thousands of years if left undisturbed.
“When we destroy coastal wetlands, for coastal development or aquaculture, we turn these impressive natural carbon sinks into additional, significant human-caused greenhouse gas sources.”
Clarifying the role of coastal and marine systems in climate mitigation – Howard – 2017 – Frontiers in Ecology and the Environment