The protection of organic carbon stored in forests is considered as an important method for mitigating climate change. Like terrestrial ecosystems, coastal ecosystems store large amounts of carbon, and there are initiatives to protect these ‘blue carbon’ stores. Organic carbon stocks in tidal salt marshes and mangroves have been estimated, but uncertainties in the stores of seagrass meadows—some of the most productive ecosystems on Earth—hinder the application of marine carbon conservation schemes. Here, we compile published and unpublished measurements of the organic carbon content of living seagrass biomass and underlying soils in 946 distinct seagrass meadows across the globe. Using only data from sites for which full inventories exist, we estimate that, globally, seagrass ecosystems could store as much as 19.9 Pg organic carbon; according to a more conservative approach, in which we incorporate more data from surface soils and depth-dependent declines in soil carbon stocks, we estimate that the seagrass carbon pool lies between 4.2 and 8.4 Pg carbon. We estimate that present rates of seagrass loss could result in the release of up to 299 Tg carbon per year, assuming that all of the organic carbon in seagrass biomass and the top metre of soils is remineralized.
This is a preview of subscription content, access via your institution
Subscribe to this journal
Receive 12 print issues and online access
$259.00 per year
only $21.58 per issue
Rent or buy this article
Prices vary by article type
Prices may be subject to local taxes which are calculated during checkout
Forster, P. et al. in IPCC Climate Change 2007: The Physical Science Basis (eds Solomon, S. et al.) (Cambridge Univ. Press, 2007).
Agrawal, A., Nepstad, D. & Chhatre, A. Reducing emissions from deforestation and forest degradation. Ann. Rev. Environ. Resour. 36, 373–396 (2011).
IPCC Good Practice Guidance for Land Use, Land-Use Change and Forestry (IPCC National Greenhouse Gas Inventories Programme, 2003).
IPCC Climate Change 2007: Synthesis Report 104 (IPCC, 2007).
Keith, H., Mackey, B. G. & Lindenmayer, D. B. Re-evaluation of forest biomass carbon stocks and lessons from the world’s most carbon-dense forests. Proc. Natl. Acad. Sci. USA 106, 11635–11640 (2009).
Chmura, G. L., Anisfeld, S. C., Cahoon, D. R. & Lynch, J. C. Global carbon sequestration in tidal, saline wetland soils. Glob. Biogeochem. Cycles 17, 1111 (2003).
Donato, D. C. et al. Mangroves among the most carbon-rich forests in the tropics. Nature Geosci. 4, 293–297 (2011).
Duarte, C. M., Middelburg, J. J. & Caraco, N. Major role of marine vegetation on the oceanic carbon cycle. Biogeosciences 2, 1–8 (2005).
Mcleod, E. et al. A blueprint for blue carbon: Toward an improved understanding of the role of vegetated coastal habitats in sequestering CO2 . Front. Ecol. Environ 7, 362–370 (2011).
Duarte, C. M. & Chiscano, C. L. Seagrass biomass and production: A reassessment. Aquat. Bot. 65, 159–174 (1999).
Zieman, J. C. & Wetzel, R. G. in Handbook of Seagrass Biology, An Ecosystem Prospective (eds Phillips, R. C. & McRoy, C. P.) 87–116 (Garland STPMPress, 1980).
Kennedy, H. et al. Seagrass sediments as a global carbon sink: Isotopic constraints. Glob. Biogeochem. Cycles 24, GB4026 (2010).
Mateo, M. A., Cebrián, J., Dunton, K. & Mutchler, T. in Seagrasses: Biology, Ecology and Conservation (eds Larkum, A. W. D., Orth, R. J. & Duarte, C. M.) 159–192 (Springer, 2006).
Mateo, M. A., Romero, J., Pérez, M., Littler, M. M. & Littler, D. S. Dynamics of millenary organic deposits resulting from the growth of the Mediterranean seagrass Posidonia oceanica. Estuar. Coast. Shelf Sci. 44, 103–110 (1997).
Orem, W. H. et al. Geochemistry of Florida Bay sediments: Nutrient history at five sites in eastern and central Florida Bay. J. Coast. Res. 15, 1055–1071 (1999).
Serrano, O. et al. The Posidonia oceanica marine sedimentary record: A Holocene archive of heavy metal pollution. Sci. Total Environ. 409, 4831–4840 (2011).
Smith, S. V. Marine macrophytes as a global carbon sink. Science 211, 838–840 (1981).
Waycott, M. et al. Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proc. Nat. Acad. Sci. USA 106, 12377–12381 (2009).
Orth, R. J. et al. A global crisis for seagrass ecosystems. BioScience 56, 987–996 (2006).
IPCC in IPCC Guidelines for National Greenhouse Gas Inventories (eds H.S. Eggleston et al.) (National Greenhouse Gas Inventories Programme,IGES, 2006).
Charpy-Roubaud, C. & Sournia, A. The comparative estimation of phytoplanktonic and microphytobenthic production in the oceans. Mar. Microb. Food Webs 4, 31–57 (1990).
Houghton, R. A. Balancing the global carbon budget. Ann. Rev. Earth Planet. Sci. 35, 313–347 (2007).
Duarte, C. M., Kennedy, H., Marbà, N. & Hendriks, I. Assessing the capacity of seagrass meadows for carbon burial: Current limitations and future strategies. Ocean Coast. Manage. 51, 671–688 (2011).
Hendriks, I. E., Sintes, T., Bouma, T. & Duarte, C. M. Experimental assessment and modeling evaluation of the effects of seagrass (P. oceanica) on flow and particle trapping. Mar. Ecol. Prog. Ser. 356, 163–173 (2007).
Lo Iacono, C. et al. Very high-resolution seismo-acoustic imaging of seagrass meadows (Mediterranean Sea): Implications for carbon sink estimates. Geophys. Res. Lett. 35, L18601 (2008).
Short, F. T. & Wyllie-Echeverria, S. Natural and human-induced disturbance of seagrasses. Environ. Conserv. 23, 17–27 (1996).
Duarte, C. M. et al. Seagrass community metabolism: Assessing the carbon sink capacity of seagrass meadows. Glob. Biogeochem. Cycles 24, GB4032 (2010).
Jandl, R. et al. How strongly can forest management influence soil carbon sequestration? Geoderma 137, 253–268 (2007).
Paul, K. I., Polglase, P. J., Nyakuengama, J. G. & Khanna, P. K. Change in soil carbon following afforestation. Forest Ecol. Manag 168, 241–257 (2002).
Paling, E. I., Fonseca, M., van Katwilk, M. M. & Van Keulen, M. in Coastal Wetlands: An Integrated Ecosystem Approach (eds Perillo, M. E., Wolanski, E., Cahoon, D. R. & Brinson, M. M.) (Elsevier, 2009).
Duarte, C. M. The future of seagrass meadows. Environ. Conserv. 29, 192–206 (2002).
Irving, A. D., Conell, S. D. & Russell, B. D. Restoring coastal plants to improve global carbon storage: Reaping what we sow. Plos One 6, e18311 (2011).
Lawson, S. E., Wiberg, P. L., McGlathery, K. J. & Fugate, D. C. Wind-driven sediment suspension controls light availability in a shallow coastal lagoon. Estuar. Coasts 30, 102–112 (2007).
Orth, R. J., Luckenbach, M. L., Marion, S. R., Moore, K. A. & Wilcox, D. J. Seagrass recovery in the Delmarva Coastal Bays, USA. Aquat. Bot. 84, 26–36 (2006).
Orth, R. J., Moore, K. A., Marion, S. R., Wilcox, D. J. & Parrish, D. Seed addition facilitates Zostera marina L. (eelgrass) recovery in a coastal bay system (USA). Mar. Ecol. Prog. Ser. 448, 177–195 (2012).
McGlathery, K. J. et al. Recovery trajectories during state change from bare sediment to eelgrass dominance. Mar. Ecol. Prog. Ser. 448, 209–221 (2012).
Pedersen, M. F., Duarte, C. M. & Cebrián, J. Rates of change in organic matter and nutrient stocks during seagrass Cymodocea nodosa colonization and stand development. Mar. Ecol. Prog. Ser. 159, 29–36 (1997).
Barrón, C., Marbà, N., Terrados, J., Kennedy, H. & Duarte, C. M. Community metabolism and carbon budget along a gradient of seagrass (Cymodocea nodosa) colonization. Limnol. Oceanogr. 49, 1642–1651 (2004).
Nellemann, C. et al. Blue Carbon. A Rapid Response Assessment 78 (United Nations Environment Programme, GRID-Arenal, 2009).
Duarte, C. M. Seagrass nutrient content. Mar. Ecol. Prog. Ser. 67, 201–207 (1990).
Fourqurean, J. W., Marbà, N., Duarte, C. M., Diaz-Almela, E. & Ruiz-Halpern, S. Spatial and temporal variation in the elemental and stable isotopic content of the seagrasses Posidonia oceanica and Cymodocea nodosa from the Illes Balears, Spain. Mar. Biol. 151, 219–232 (2007).
Fourqurean, J. W., Moore, T. O., Fry, B. & Hollibaugh, J. T. Spatial and temporal variation in C:N:P ratios, δ15N, and δ13C of eelgrass Zostera marina as indicators of ecosystem processes, Tomales Bay, California, USA. Mar. Ecol. Prog. Ser. 157, 147–157 (1997).
Fourqurean, J. W., Zieman, J. C. & Powell, G. V. N. Phosphorus limitation of primary production in Florida Bay: Evidence from the C:N:P ratios of the dominant seagrass Thalassia testudinum. Limnol. Oceanogr. 37, 162–171 (1992).
Hemminga, M. A. & Duarte, C. M. Seagrass Ecology (Cambridge Univ.Press, 2000).
This is a contribution of the International Blue Carbon Science Working Group. We thank the contributors of unpublished data to our database, including A. Paytan, W.H. Orem and M. Copertino. Partial support for J.W.F.’s contribution was provided by a Gledden Visiting Senior Fellowship from the Institute of Advanced Studies, University of Western Australia and an Australian National Network in Marine Sciences Visiting Scholar fellowship and by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research programme under Grant No. DBI-0620409. C.M.D and N.M. were financially supported through the MEDEICG project of the Spanish Ministry of Science and Innovation (project ID CTM2009-07013). G.A.K. was supported by NHT II- Caring for our Country funding. M.H. was financially supported by the Danish Natural Science Foundation (09-071369). M.A.M. and O.S. acknowledge the Spanish Ministry of Science and Innovation (MICINN) and the High Council of Scientific Research (CSIC) for financially supporting various pioneering projects to explore the role of P. oceanica as a coastal C sink and a palaeoecological record. D.K.J. acknowledges the Danish National Monitoring and Assessment Programme for the Aquatic and Terrestrial Environment (NOVANA) and colleagues associated with the programme for support. K.J.M. was supported by the National Science Foundation through the Virginia Coast Reserve Long-Term Ecological Research programme under Grant No. 0621014. This is contribution no. 550 from the Southeast Environmental Research Center at Florida International University.
The authors declare no competing financial interests.
About this article
Cite this article
Fourqurean, J., Duarte, C., Kennedy, H. et al. Seagrass ecosystems as a globally significant carbon stock. Nature Geosci 5, 505–509 (2012). https://doi.org/10.1038/ngeo1477