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      Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems

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          Recent attention has focused on the high rates of annual carbon sequestration in vegetated coastal ecosystems—marshes, mangroves, and seagrasses—that may be lost with habitat destruction (‘conversion’). Relatively unappreciated, however, is that conversion of these coastal ecosystems also impacts very large pools of previously-sequestered carbon. Residing mostly in sediments, this ‘blue carbon’ can be released to the atmosphere when these ecosystems are converted or degraded. Here we provide the first global estimates of this impact and evaluate its economic implications. Combining the best available data on global area, land-use conversion rates, and near-surface carbon stocks in each of the three ecosystems, using an uncertainty-propagation approach, we estimate that 0.15–1.02 Pg (billion tons) of carbon dioxide are being released annually, several times higher than previous estimates that account only for lost sequestration. These emissions are equivalent to 3–19% of those from deforestation globally, and result in economic damages of $US 6–42 billion annually. The largest sources of uncertainty in these estimates stems from limited certitude in global area and rates of land-use conversion, but research is also needed on the fates of ecosystem carbon upon conversion. Currently, carbon emissions from the conversion of vegetated coastal ecosystems are not included in emissions accounting or carbon market protocols, but this analysis suggests they may be disproportionally important to both. Although the relevant science supporting these initial estimates will need to be refined in coming years, it is clear that policies encouraging the sustainable management of coastal ecosystems could significantly reduce carbon emissions from the land-use sector, in addition to sustaining the well-recognized ecosystem services of coastal habitats.

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          Most cited references 5

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          A large and persistent carbon sink in the world's forests.

          The terrestrial carbon sink has been large in recent decades, but its size and location remain uncertain. Using forest inventory data and long-term ecosystem carbon studies, we estimate a total forest sink of 2.4 ± 0.4 petagrams of carbon per year (Pg C year(-1)) globally for 1990 to 2007. We also estimate a source of 1.3 ± 0.7 Pg C year(-1) from tropical land-use change, consisting of a gross tropical deforestation emission of 2.9 ± 0.5 Pg C year(-1) partially compensated by a carbon sink in tropical forest regrowth of 1.6 ± 0.5 Pg C year(-1). Together, the fluxes comprise a net global forest sink of 1.1 ± 0.8 Pg C year(-1), with tropical estimates having the largest uncertainties. Our total forest sink estimate is equivalent in magnitude to the terrestrial sink deduced from fossil fuel emissions and land-use change sources minus ocean and atmospheric sinks.
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            A world without mangroves?

             K C Ewel,  N Koedam,  K Anger (2007)
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              CO2 Efflux from Cleared Mangrove Peat

              Background CO2 emissions from cleared mangrove areas may be substantial, increasing the costs of continued losses of these ecosystems, particularly in mangroves that have highly organic soils. Methodology/Principal Findings We measured CO2 efflux from mangrove soils that had been cleared for up to 20 years on the islands of Twin Cays, Belize. We also disturbed these cleared peat soils to assess what disturbance of soils after clearing may have on CO2 efflux. CO2 efflux from soils declines from time of clearing from ∼10 600 tonnes km−2 year−1 in the first year to 3000 tonnes km2 year−1 after 20 years since clearing. Disturbing peat leads to short term increases in CO2 efflux (27 umol m−2 s−1), but this had returned to baseline levels within 2 days. Conclusions/Significance Deforesting mangroves that grow on peat soils results in CO2 emissions that are comparable to rates estimated for peat collapse in other tropical ecosystems. Preventing deforestation presents an opportunity for countries to benefit from carbon payments for preservation of threatened carbon stocks.

                Author and article information

                Role: Editor
                PLoS One
                PLoS ONE
                PLoS ONE
                Public Library of Science (San Francisco, USA )
                4 September 2012
                : 7
                : 9
                [1 ]Nicholas Institute for Environmental Policy Solutions, Duke University, Durham, North Carolina, United States of America
                [2 ]Ecosystem & Landscape Ecology Lab, University of Wisconsin, Madison, Wisconsin, United States of America
                [3 ]ESA Phillip Williams & Associates, San Francisco, California, United States of America
                [4 ]United States Environmental Protection Agency, Research Triangle Park, North Carolina, United States of America
                [5 ]School of Public and Environmental Affairs, Indiana University, Bloomington, Indiana, United States of America
                [6 ]Department of Biological Sciences and Southeast Environmental Research Center, Florida International University, North Miami, Florida, United States of America
                [7 ]Department of Fisheries and Wildlife, Oregon State University, Corvallis, Oregon, United States of America and Center for International Forest Research, Bogor, Indonesia
                [8 ]Department of Global Change Research, Mediterranean Institute for Advanced Studies, Esporles, Illes Balears, Spain
                [9 ]Smithsonian Environmental Research Center, Edgewater, Maryland, United States of America
                [10 ]Conservation International, Arlington, Virginia, United States of America
                [11 ]International Union for the Conservation of Nature, Washington, District of Columbia, United States of America
                [12 ]The Ocean Conservancy, Baton Rouge, Louisiana, United States of America
                National Institute of Water & Atmospheric Research, New Zealand
                Author notes

                Competing Interests: Appointment funding for one author (SC) comes from ESA Phillip Williams & Associates, a commercial source. This does not alter the authors' adherence to all the PLoS ONE policies on sharing data and materials.

                Conceived and designed the experiments: LP DCD BCM SC WAJ SS CC JWF JBK NM PM EP DH DG AB. Analyzed the data: LP DCD BCM SC WAJ CC JWF JBK NM PM. Wrote the paper: LP DCD BCM SC WAJ SS CC JWF JBK NM PM EP DH DG AB.


                This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.

                Pages: 7
                Funding for this effort was provided by the Linden Trust for Conservation ( and Roger and Victoria Sant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
                Research Article
                Coastal Ecology
                Conservation Science
                Ecological Economics
                Environmental Protection
                Global Change Ecology
                Marine Ecology
                Restoration Ecology
                Soil Ecology
                Marine Biology
                Coastal Ecology
                Marine Conservation
                Marine Ecology
                Earth Sciences
                Environmental Sciences
                Environmental Economics
                Carbon Cycle
                Carbon Sink
                Marine and Aquatic Sciences
                Coastal Ecology
                Marine Ecology



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