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

Journal Article


Abstract


  • Tidal 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.

Authors


  •   Ewers, Carolyn (external author)
  •   Baldock, Jeffrey (external author)
  •   Hawke, Bruce (external author)
  •   Gadd, Patricia S. (external author)
  •   Zawadzki, Atun (external author)
  •   Heijnis, Henk (external author)
  •   Jacobsen, Geraldine (external author)
  •   Rogers, Kerrylee
  •   Macreadie, Peter (external author)

Publication Date


  • 2019

Citation


  • Ewers 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.

Scopus Eid


  • 2-s2.0-85063907432

Number Of Pages


  • 10

Start Page


  • 427

End Page


  • 437

Volume


  • 672

Place Of Publication


  • Netherlands

Abstract


  • Tidal 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.

Authors


  •   Ewers, Carolyn (external author)
  •   Baldock, Jeffrey (external author)
  •   Hawke, Bruce (external author)
  •   Gadd, Patricia S. (external author)
  •   Zawadzki, Atun (external author)
  •   Heijnis, Henk (external author)
  •   Jacobsen, Geraldine (external author)
  •   Rogers, Kerrylee
  •   Macreadie, Peter (external author)

Publication Date


  • 2019

Citation


  • Ewers 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.

Scopus Eid


  • 2-s2.0-85063907432

Number Of Pages


  • 10

Start Page


  • 427

End Page


  • 437

Volume


  • 672

Place Of Publication


  • Netherlands