Impacts of land reclamation on tidal marsh ‘blue carbon’ stocks

dc.contributor.authorEwers Lewis, CJen_AU
dc.contributor.authorBaldock, JAen_AU
dc.contributor.authorHawke, Ben_AU
dc.contributor.authorGadd, PSen_AU
dc.contributor.authorZawadzki, Aen_AU
dc.contributor.authorHeijnis, Hen_AU
dc.contributor.authorJacobsen, GEen_AU
dc.contributor.authorRogers, Ken_AU
dc.contributor.authorMacreadie, PIen_AU
dc.description.abstractTidal marsh ecosystems are among earth's most efficient natural organic carbon (C) sinks and provide myriad ecosystem services. However, approximately half have been ‘reclaimed’ – i.e. converted to other land uses – potentially turning them into sources of greenhouse gas emissions. In this study, we applied C stock measurements and paleoanalytical techniques to sediments from reclaimed and intact tidal marshes in southeast Australia. We aimed to assess the impacts of reclamation on: 1) the magnitude of existing sediment C stocks; 2) ongoing C sequestration and storage; and 3) C quality. Differences in sediment horizon depths (indicated by Itrax-XRF scanning) and ages (indicated by lead-210 and radiocarbon dating) suggest a physical loss of sediments following reclamation, as well as slowing of sediment accumulation rates. Sediments at one meter depth were between ~2000 and ~5300 years older in reclaimed cores compared to intact marsh cores. We estimate a 70% loss of sediment C in reclaimed sites (equal to 73 Mg C ha−1), relative to stocks in intact tidal marshes during a comparable time period. Following reclamation, sediment C was characterized by coarse particulate organic matter with lower alkyl-o-alkyl ratios and higher amounts of aromatic C, suggesting a lower extent of decomposition and therefore lower likelihood of being incorporated into long-term C stocks compared to that of intact tidal marshes. We conclude that reclamation of tidal marshes can diminish C stocks that have accumulated over millennial time scales, and these losses may go undetected if additional analyses are not employed in conjunction with C stock estimates. © 2019 Published by Elsevier B.V.en_AU
dc.identifier.citationEwers Lewis, C. J., Baldock, J. A., Hawke, B., Gadd, P. S., Zawadzki, A., Heijnis, H., Jacobsen, G. E., Rogers, K. & Macreadie, P. I. (2019). Impacts of land reclamation on tidal marsh ‘blue carbon’ stocks. Science of the Total Environment, 672, 427-437. doi:10.1016/j.scitotenv.2019.03.345en_AU
dc.identifier.journaltitleScience of the Total Environmenten_AU
dc.subjectLand reclamationen_AU
dc.subjectGreenhouse gasesen_AU
dc.subjectCarbon sequestrationen_AU
dc.titleImpacts of land reclamation on tidal marsh ‘blue carbon’ stocksen_AU
dc.typeJournal Articleen_AU
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