An evidence-based approach to understanding blue carbon dynamics and distribution on the Pacific coast of Canada

Salt marshes are considered effective "blue carbon" sinks and potential NCSs. However, using blue carbon ecosystems in climate change mitigation requires reliable quantification of area and carbon dynamics. Here I examine sediment cores, vegetation, depth profiles, and porewater salinities to characterize carbon dynamics in the 222-ha Boundary Bay marsh, the largest salt marsh in British Columbia. The marsh exhibits substantial variability in carbon processes depending on marsh location, with marsh expansion and increased carbon storage in western Boundary Bay and marsh loss and erosion in the east. I also map and compare detailed areal estimates for three tidal salt marshes in southern British Columbia with regional and global datasets to test their reliability in estimating marsh extent for blue carbon calculations. My results indicate that existing salt marsh distribution datasets largely overestimate marsh distribution, leading to overestimations in blue carbon storage and accumulation.