Carbon sequestration in southern temperate saltmarshes – local insight and global comparison

Carbon capture and storage in coastal wetlands constitutes a highly valuable ecosystem service and can provide incentives for their conservation. Saltmarshes in particular can have much higher carbon sequestration rates than... [ view full abstract ]

Carbon capture and storage in coastal wetlands constitutes a highly valuable ecosystem service and can provide incentives for their conservation. Saltmarshes in particular can have much higher carbon sequestration rates than other wetlands or vegetated ecosystems. ‘Blue Carbon’ initiatives have led to intensification in research efforts, yet most studies of carbon capture in saltmarshes still come from northern hemisphere where saltmarshes are dominated by grasses. We will present findings from a study into carbon sequestration in saltmarshes in Gulf St Vincent, South Australia, where soils are mineral dominated. We compared the carbon stocks and burial rates from a relatively pristine, a degraded, and a restored saltmarsh site through analyses of bulk density, carbon elemental analyses, and sediment accretion determined using 210Pb and 14C soil dating methods. The total carbon stock was higher in the pristine saltmarsh than in the restored and degraded saltmarshes, which contained more organic than inorganic C. Carbon sequestration rate at the pristine saltmarsh site was 223 g C m-2 y-1., comparable to a global average for saltmarshes. There are significant and predictable variations in local, regional and global carbon stocks and sequestration rates from saltmarshes and tidal wetlands, which are compared to our South Australian examples. The value of southern temperate saltmarshes on carbon markets will be addressed, with implications for conservation and restoration.