Refining the Global Estimate of Mangrove Carbon Burial Rates Using Sedimentary and Geomorphic Settings

Background

Previous research has focused on calculating accurate estimates of global mangrove carbon stock, while lacking studies examining global patterns of organic carbon (OC) burial. Mangrove forests are naturally highly variable, existing in different sedimentary (i.e., terrigenous- or carbonate-dominant) and geomorphic (i.e., delta, estuary, lagoon, open coast) environments. In addition, different anthropogenic factors affect their structure. Therefore, it is necessary to examine how the spatial variability of mangrove sedimentary and geomorphic settings affects global OC burial estimates.

Goals and Methods

The authors conducted a literature search to compile OC burial rate data, and joined each of these burial rate observations to a mangrove sediment category and geomorphic type on ArcGIS. They used the adjusted means from this data set to find a global estimate of annual OC burial for each sedimentary and geomorphic setting (SGS) and sediment category.

Conclusions and Takeaways

This study calculates that the global annual OC burial rate based on total mangrove area is 20.18 teragrams per year. However, scaling this estimate by sediment category or SGS increases the OC burial rate to 22.10 and 24.17 teragrams per year, respectively. This shows the tendency to overestimate global OC burial rates when ignoring sedimentary and geomorphic traits and assuming that mangrove forests uniformly bury carbon. Burial rates differ between SGSs, with terrigenous deltas having the highest annual burial rates and carbonate estuaries, lagoons, and open coasts having the lowest. Scaling global burial rates by the global area of each SGS creates more accurate estimates of total annual OC burial.