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@prefix dcterms: <http://purl.org/dc/terms/> . @prefix xsd: <http://www.w3.org/2001/XMLSchema#> . @prefix gcis: <http://data.globalchange.gov/gcis.owl#> . @prefix cito: <http://purl.org/spar/cito/> . @prefix biro: <http://purl.org/spar/biro/> . <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/tidal-wetlands-and-estuaries/finding/key-message-15-1> dcterms:identifier "key-message-15-1"; gcis:findingNumber "15.1"^^xsd:string; gcis:findingStatement "The top 1 m of tidal wetland soils and estuarine sediments of North America contains 1,886 ± 1,046 teragrams of carbon (Tg C) (<em>high confidence, very likely</em>)."^^xsd:string; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/tidal-wetlands-and-estuaries>; gcis:isFindingOf <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report>; ## Properties of the finding: gcis:descriptionOfEvidenceBase "Several sources were available to verify the extent of intertidal wetland and subtidal habitats in North America for Key Finding 1. First, the U.S Fish and Wildlife Service National Wetlands Inventory (USFWS NWI 2017) is a conservative but definitive source due to inclusion of tidal modifiers to clarify hydrology. Second, a synthesis of Mexican, Canadian, and U.S. saline coastal habitats was provided by the Commission for Environmental Cooperation (CEC 2016). For carbon density in intertidal wetland environments, a synthesis of datasets from tidal wetland habitats reviewed (Chmura et al., 2003; Ouyang and Lee 2014; Holmquist et al., 2018a) found a very narrow distribution measured in kilograms (kg; 27.0 ± 13.0 kg C per m) in wetland carbon stocks across North American tidal wetlands, regardless of salinity or vegetation type, as did a national dataset review (28.0 ± 7.8; Nahlik and Fennessy 2016). A global synthesis (Sanderman et al., 2018) provided data to synthesize a new estimate for Mexico’s mangroves (31.8 ± 1.3 kg C per m). For carbon stocks in seagrass environments, synthetic data from literature reviews reporting bulk density and organic carbon along 1-m profiles were used for coast-specific estimates: 2.0 ± 1.3 for the Atlantic Coast, 3.1 ± 2.4 for the Gulf of Mexico coast, 1.4 ± 1.2 for the Pacific Coast, and 2.0 for boreal and Arctic regions. For carbon density in estuarine open-water sediments, coastal regions played no clear role and geomorphic settings were not available (Smith et al., 2015), so a mean of 1.0 kg per m was chosen, using a literature-based average for total organic carbon (TOC) content (0.4% organic carbon; range 0.17% to 2%; Premuzic et al., 1982; Kennedy et al., 2010) coupled with a literature average of percentage of dry bulk densities (2.6 g C per cm; Muller and Suess 1979)."^^xsd:string; gcis:assessmentOfConfidenceBasedOnEvidence "There is theoretical and empirical convergence on tidal marsh carbon densities but a likely bias to underrepresenting tidal freshwater habitats. Further, seagrass carbon densities show a wider range and an apparent latitudinal gradient of decreasing carbon density from tropical to temperate environments. Geomorphic variability (e.g., shallow waters versus fjords) in estuarine sediments may reduce uncertainty in stock assessments, but map layers are not available for North America."^^xsd:string; gcis:newInformationAndRemainingUncertainties "Uncertainties vary for each subhabitat, and these data likely represent an underestimate of total stocks, which may be many meters deep. For tidal wetland soils to 1 m in depth, the primary uncertainty is in underestimates of mapped boundaries, with, for example, no accounting of freshwater tidal systems in either Mexico or Canada, and likely undercounting of freshwater tidal wetlands in the United States. For seagrass, the spatial data are conservative estimates of located and documented habitat, although seagrass populations can shift boundaries rapidly and potentially there are far more currently unmapped seagrass beds in North America. For estuarine spatial data, the boundaries are constrained by bathymetry maps, which generally are more uncertain in higher latitudes. In contrast, carbon densities have narrow ranges in tidal wetland and estuarine soils but a skewed representation in seagrass soils, a difference which may be due to limited sampling in northern latitudes."^^xsd:string; a gcis:Finding . ## This finding cites the following entities: <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/tidal-wetlands-and-estuaries/finding/key-message-15-1> prov:wasDerivedFrom <https://data.globalchange.gov/report/second-state-carbon-cycle-report-soccr2-sustained-assessment-report/chapter/preface/figure/figurep-4>.