Abstract
Carbon stock and carbon accumulation rate data are vital to multiple aspects of tidal wetland conservation and restoration policy. In California, USA tidal soil data are rare outside of the San Francisco Bay and Sacramento Delta regions, despite the differing conditions experienced by the outer coastline. Here we provide carbon stocks and decadal-to-centennial-scale carbon accumulation rate calculations. This dataset presents 83 soil depth profiles from 15 sites, with 58 cores from 12 tidal wetland sites analyzed for carbon stock, mostly from the outer coastline of California. Mean organic matter content was 11%, and stocks estimated to 1 meter depth ranged from 15.4 to 44.7 kgC m−2. Organic matter content generally declined asymptotically with depth. Carbon accumulation rates ranged from 39.2 to 130.0 gC m−2 yr−1. Neither carbon stock nor carbon accumulation rates were notably different from global average values. Data at this level of reporting are vital for establishing restoration baselines, informing greenhouse gas mitigation planning, and projecting future ecosystem response to sea-level rise.
Similar content being viewed by others
Data availability
Both disaggregated and derived data presented in this paper is available in Brown et al.75, at the following link (https://doi.org/10.25573/serc.28672772). Data is published under a Creative Commons (BY-4) license.
Code availability
The code used to calculate carbon stocks, accretion rates, and carbon accumulation rates, as well as generate figures, is available in Brown et al.75, at the following link (https://doi.org/10.25573/serc.28672772). Code is published under a Creative Commons (BY-4) license.
References
Morris, J. & Callaway, J. Chapter 6: Physical and biological regulation of carbon sequestration in salt marshes. in A Blue Carbon Primer: The State of Coastal Wetland Carbon Science, Practice, and Policy (eds. Windham-Meyers, L., Crooks, S. & Troxler, T.) (2018).
Morris, J. T., Sundareshwar, P. V., Nietch, C. T., Kjerfve, B. & Cahoon, D. R. Responses of Coastal Wetlands to Rising Sea Level. Ecology 83, 2869–2877 (2002).
Chmura, G. L., Anisfeld, S. C., Cahoon, D. R. & Lynch, J. C. Global carbon sequestration in tidal, saline wetland soils. Global Biogeochem. Cycles 17 (2003).
Callaway, J. C., Borgnis, E. L., Turner, R. E. & Milan, C. S. Carbon Sequestration and Sediment Accretion in San Francisco Bay Tidal Wetlands. Estuaries and Coasts 35, 1163–1181 (2012).
Morris, J. T. et al. Contributions of organic and inorganic matter to sediment volume and accretion in tidal wetlands at steady state. Earths Future 4, 110–121 (2016).
Nyman, J. A., Walters, R. J., Delaune, R. D. & Patrick, W. H. Jr. Marsh vertical accretion via vegetative growth. Estuar. Coast. Shelf Sci. 69, 370–380 (2006).
Mueller, P. et al. Global-change effects on early-stage decomposition processes in tidal wetlands–implications from a global survey using standardized litter. Biogeosciences 15, 3189–3202 (2018).
Rosencranz, J. A. et al. The role of sediment dynamics for inorganic accretion patterns in southern California’s Mediterranean-climate salt marshes. Estuaries Coast. 40, 1371–1384 (2017).
Ward, K. M., Callaway, J. C. & Zedler, J. B. Episodic colonization of an intertidal mudflat by native cordgrass (Spartina foliosa) at Tijuana Estuary. Estuaries 26, 116–130 (2003).
Kirwan, M. L. et al. Limits on the adaptability of coastal marshes to rising sea level: ECOGEOMORPHIC LIMITS TO WETLAND SURVIVAL. Geophys. Res. Lett. 37 (2010).
Eagle, M. J. et al. Soil carbon consequences of historic hydrologic impairment and recent restoration in coastal wetlands. Sci. Total Environ. 848, 157682 (2022).
Kroeger, K. D., Crooks, S., Moseman-Valtierra, S. & Tang, J. Restoring tides to reduce methane emissions in impounded wetlands: A new and potent Blue Carbon climate change intervention. Sci. Rep. 7, 11914 (2017).
Barbier, E. B., Hacker, S. D. & Kennedy, C. The value of estuarine and coastal ecosystem services. Ecological (2011).
Woo, I. et al. Carbon flux, storage, and wildlife co‐benefits in a restoring estuary: Case study at the Nisqually river delta, Washington. Wetland Carbon and Environmental Management 103–125, https://doi.org/10.1002/9781119639305.ch5 (2021).
Arias-Ortiz, A. et al. Tidal and nontidal marsh restoration: a trade-off between carbon sequestration, methane emissions, and soil accretion. Journal of Geophysical Research: Biogeosciences, https://doi.org/10.1029/2021JG006573 (2021).
Morris, J. T., Drexler, J. Z., Vaughn, L. J. S. & Robinson, A. H. An assessment of future tidal marsh resilience in the San Francisco Estuary through modeling and quantifiable metrics of sustainability. Frontiers in Environmental Science 10, 1039143 (2022).
Raposa, K. B. et al. Evaluating Thin-Layer Sediment Placement as a Tool for Enhancing Tidal Marsh Resilience: a Coordinated Experiment Across Eight US National Estuarine Research Reserves. Estuaries and Coasts 46, 595–615 (2023).
Thorne, K. et al. U.S. Pacific coastal wetland resilience and vulnerability to sea-level rise. Science Advances 4, eaao3270 (2018).
Thorne, K. M. et al. Nature-based solutions could offset coastal squeeze of tidal wetlands from sea-level rise on the U. S. Pacific coast. Sci. Rep. 15, 11443 (2025).
Fargione, J. E. et al. Natural climate solutions for the United States. Sci. Adv. 4, eaat1869 (2018).
California Natural Resources Agency. California’s Nature-Based Solutions Climate Targets. https://resources.ca.gov/-/media/CNRA-Website/Files/Initiatives/Expanding-Nature-Based-Solutions/Californias-NBS-Climate-Targets-2024.pdf (2024).
Ward, M. A. Assessing Existing Data, Models, and Opportunities for California’s Blue Carbon Ecosystems in the Context of California Air Resources Board’s 2027 Climate Change Scoping Plan. https://opc.ca.gov/wp-content/uploads/2024/07/Blue-carbon-model-assessment-report-508.pdf (2024).
California Air Resources Board. 2022 Scoping Plan for Achieving Carbon Neutrality. https://ww2.arb.ca.gov/sites/default/files/2023-04/2022-sp.pdf (2022).
Holmquist, J. R. et al. The Coastal Carbon Library and Atlas: Open source soil data and tools supporting blue carbon research and policy. Glob. Chang. Biol. 30, e17098 (2024).
Coastal Carbon Network. Database: Coastal Carbon Library (Version 1.5.0). https://doi.org/10.25573/SERC.21565671 (2025).
Arias-Ortiz, A., Masque, P., Paytan, A. & Baldocchi, D. D. Dataset: Tidal and nontidal marsh restoration: a trade-off between carbon sequestration, methane emissions, and soil accretion. https://doi.org/10.25573/serc.15127743.v2 (2021).
Schile-Beers, L. M., Altieri, A. H. & Megonigal, J. P. Dataset: Mangrove, tidal wetland and seagrass soil carbon stocks along latitudinal gradients. https://doi.org/10.25573/SERC.11971527 (2023).
Buffington, K., Janousek, C., Thorne, K. & Dugger, B. Dataset: Carbon stocks and accretion rates for wetland sediment at Miner Slough, Sacramento-San Joaquin Delta, California. https://doi.org/10.25573/SERC.11968740 (2020).
Marsh Vertical Accretion in a Southern California Estuary, U.S.A. Estuarine, Coastal and Shelf Science 43, 19–32 (1996).
Callaway, J. C., Borgnis, E. L., Turner, R. E. & Milan, C. S. Dataset: Carbon sequestration and sediment accretion in San Francisco Bay tidal wetlands. https://doi.org/10.25573/DATA.9693251 (2019).
Carlin, J. et al. Dataset: Sedimentary organic carbon measurements in a restored coastal wetland in San Francisco Bay, CA, USA. https://doi.org/10.25573/SERC.16416684 (2021).
Curtis, J. A., Thorne, K. M., Freeman, C. M., Buffington, K. J. & Drexler, J. Z. A Summary of Water-Quality and Salt Marsh Monitoring, Humboldt Bay, California. USGS Publications Warehouse https://doi.org/10.3133/ofr20221076 (2022).
Curtis et al. Salt marsh monitoring during water years 2013 to 2019, Humboldt Bay, CA â water levels, surface deposition, elevation change, and carbon storage. https://doi.org/10.5066/P9QLAL7B (2022).
Drexler, J. Z., de Fontaine, C. S. & Brown, T. A. Peat Accretion Histories During the Past 6,000 Years in Marshes of the Sacramento-San Joaquin Delta, CA, USA. Estuaries and Coasts 32, 871–892 (2009).
Holmquist, J. R. et al. Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States: Public Soil Carbon Data Release. https://doi.org/10.25572/ccrcn/10088/35684 (2018).
Kauffman, J. B. et al. Total ecosystem carbon stocks at the marine-terrestrial interface: Blue carbon of the Pacific Northwest Coast, United States. Global Change Biology https://doi.org/10.1111/gcb.15248 (2020).
Kauffman, J. B. et al. Dataset: Carbon stocks in seagrass meadows, emergent marshes, and forested tidal swamps of the Pacific Northwest. https://doi.org/10.25573/serc.12640172 (2020).
Maxwell, T. L. et al. Database: Tidal Marsh Soil Organic Carbon (MarSOC) Dataset. https://doi.org/10.5281/ZENODO.8414110 (2023).
Maxwell, T. L. et al. Global dataset of soil organic carbon in tidal marshes. Scientific Data 10 (2023).
Nahlik, A. M. & Fennessy, M. S. Siobhan. Carbon storage in US wetlands. Nature Communications https://doi.org/10.1038/ncomms13835 (2016).
National Wetland Condition Assessment 2011. https://www.epa.gov/national-aquatic-resource-surveys/data-national-aquatic-resource-surveys (2016).
National Wetland Condition Assessment: 2011 Technical Report. https://www.epa.gov/national-aquatic-resource-surveys/national-wetland-condition-assessment-2011-technical-report (2016).
Patrick, W. H. & DeLaune, R. D. Subsidence. accretion. and sea level rise in south San Francisco Bay marshes. Limnol. Oceanogr. 35, 1389–1395 (1990).
Rogers, K. et al. Wetland carbon storage controlled by millennial-scale variation in relative sea-level rise. Nature 567, 91–95 (2019).
Ward, M. A. et al. Blue carbon stocks and exchanges along the California coast. Biogeosciences 18, 4717–4732 (2021).
Ward, M. Data from: Organic carbon, grain size, elemental/isotopic composition. https://doi.org/10.5061/dryad.m0cfxpp31 (2021).
Watson, E. B. & Byrne, R. Late Holocene Marsh Expansion in Southern San Francisco Bay, California. Estuaries and Coasts 36, 643–653 (2013).
Weis, D. A., Callaway, J. C. & Gersberg, R. M. Vertical Accretion Rates and Heavy Metal Chronologies in Wetland Sediments of the Tijuana Estuary. Estuaries 24, 840 (2001).
Weis & Anthony, D. Vertical accretion rates and heavy metal chronologies in wetland sediments of Tijuana Estuary. (San Diego State University, 1999).
Windham-Myers, L. et al. Biogeochemical processes in an urban, restored wetland of San Francisco Bay, California, 2007-2009: methods and data for plant, sediment and water parameters. https://doi.org/10.3133/ofr20101299 (2010).
Drexler, J. Z., Fontaine, C. S. & Deverel, S. J. The legacy of wetland drainage on the remaining peat in the Sacramento — San Joaquin Delta, California, USA. Wetlands (Wilmington) 29, 372–386 (2009).
Holmquist, J. R. et al. Accuracy and Precision of Tidal Wetland Soil Carbon Mapping in the Conterminous United States. Sci. Rep. 8, 9478 (2018).
Janousek, C. N. et al. Blue carbon stocks along the Pacific coast of North America are mainly driven by local rather than regional factors. Global Biogeochem. Cycles 39 (2025).
Fard, E., Brown, L. N., Lydon, S., Smol, J. P. & MacDonald, G. M. High-resolution sedimentological and geochemical records of three marshes in San Francisco Bay, California. Quat. Int. 602, 49–65 (2021).
Brown, L. N. California salt marsh accretion, ecosystem services, and disturbance responses in the face of climate change. (University of California, Los Angeles, 2019).
Zedler, J. B. et al. Californian salt-marsh vegetation: An improved model of spatial pattern. Ecosystems 2, 19–35 (1999).
Heiri, O., Lotter, A. F. & Lemcke, G. Loss on ignition as a method for estimating organic and carbonate content in sediments: reproducibility and comparability of results. J. Paleolimnol. 25, 101–110 (2001).
Craft, C. B., Seneca, E. D. & Broome, S. W. Loss on ignition and kjeldahl digestion for estimating organic carbon and total nitrogen in estuarine marsh soils: Calibration with dry combustion. Estuaries 14, 175–179 (1991).
Sanderman, J. et al. A global map of mangrove forest soil carbon at 30 m spatial resolution. Environ. Res. Lett. https://doi.org/10.1088/1748-9326/aabe1c (2018).
Maxwell, T. L. et al. Soil carbon in the world’s tidal marshes. Nature Communications 15, 10265 (2024).
IPCC. 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands. (IPCC, Switzerland, 2014).
Lovelock, C. E., Fourqurean, J. W. & Morris, J. T. Modeled CO2 emissions from coastal wetland transitions to other land uses: Tidal marshes, mangrove forests, and seagrass beds. Front. Mar. Sci. 4 (2017).
Holmquist, J. et al. Uncertainty in United States coastal wetland greenhouse gas inventorying. Environ. Res. Lett. 13 (2018).
R Core Team. R: A Language and Environment for Statistical Computing. https://www.R-project.org/ (2019).
Delaune, R., Patrick, W. H. & Buresh, R. Sedimentation rates determined by 137Cs dating in a rapidly accreting salt marsh. Nature 275, 532–533 (1978).
Drexler, J. Z., Fuller, C. C. & Archfield, S. The approaching obsolescence of 137Cs dating of wetland soils in North America. Quat. Sci. Rev. 199, 83–96 (2018).
Thompson Hobbs, N. & Hooten, M. B. Bayesian Models: A Statistical Primer for Ecologists. (Princeton University Press, 2015).
Aquino-López, M. A., Blaauw, M., Christen, J. A. & Sanderson, N. K. Bayesian analysis of 210Pb dating. J. Agric. Biol. Environ. Stat. 23, 317–333 (2018).
Appleby, P. G. & Oldfield, F. The calculation of lead-210 dates assuming a constant rate of supply of unsupported 210Pb to the sediment. Catena 5, 1–8 (1978).
Holmquist, J. R., Brown, L. N. & MacDonald, G. M. Localized scenarios and latitudinal patterns of vertical and lateral resilience of tidal marshes to sea‐level rise in the contiguous United States. Earths Future 9 (2021).
Zhang, F. et al. A comprehensive global dataset of atmospheric 7 Be and 210 Pb measurements: air concentration and depositional flux. Earth System Science Data Discussions 2021, 1–75 (2021).
Gräler, B., Pebesma, E. & Heuvelink, G. Spatio-Temporal Interpolation using gstat. R J. 8, 204 (2016).
Pebesma, E. & Heuvelink, G. Spatio-temporal interpolation using gstat. RFID Journal (2016).
NOAA. Sea-Level Trends. https://tidesandcurrents.noaa.gov/sltrends/ (2025).
Brown, L. N. et al. Tidal wetland soil carbon accumulation rates for coastal California. https://doi.org/10.25573/serc.28672772 (2026).
Arias-Ortiz, A. et al. Reviews and syntheses: 210 Pb-derived sediment and carbon accumulation rates in vegetated coastal ecosystems–setting the record straight. Biogeosciences 15, 6791–6818 (2018).
Clymo, R. S., Turunen, J. & Tolonen, K. Carbon Accumulation in Peatland. Oikos 81, 368 (1998).
Forbrich, I., Giblin, A. E. & Hopkinson, C. S. Constraining Marsh Carbon Budgets Using Long-Term C Burial and Contemporary Atmospheric CO 2 Fluxes. J. Geophys. Res. Biogeosci. 18, 83 (2018).
Crooks, S. et al. Coastal wetland management as a contribution to the US National Greenhouse Gas Inventory. Nat. Clim. Chang. 8, 1109–1112 (2018).
Needelman, B. A. et al. The science and policy of the verified carbon standard methodology for tidal wetland and seagrass restoration. Estuaries Coast. 41, 2159–2171 (2018).
Schile, L. M. et al. Modeling tidal marsh distribution with sea-level rise: evaluating the role of vegetation, sediment, and upland habitat in marsh resiliency. PLoS One 9, e88760 (2014).
Acknowledgements
The authors acknowledge the following funding sources: Department of Interior establishing grant #Y561461:03, the Southwest Climate Adaptation Science Center, and USGS research grants #G12AC20505, #G13AC00083, #G14AP00178, the Environmental Protection Agency, the UCLA Graduate Research Mentorship Program, the UCLA Muir Endowment, and the Smithsonian Institution. We would like to thank the U.S. Geological Survey (USGS) Western Ecological Research Center. Any use of trade, firm, or product names in this publication is for descriptive purposes only and does not imply endorsement by the U.S. government. We would like to thank Katie Glover, Kate Willis, Marcus Thompson, Scott Lydon, Remi Bardou, Jordan Rosencranz, Jiwoo Han, Ben Nauman, Taylor McCleery, Cameron Powell, Megan Brown, and Mike Fischella for assistance with fieldwork. We thank Keith Schaffer, Maoqiao Mao, Sam Trumbly, Tongwei Wang, Allison Bell and Tian Gao for laboratory assistance. We thank Kirk Gilligan, Rick Nye, Mason Hill, and Valerie Vartanian for facilitating site access. We thank Chase Freeman for assistance in choosing sampling locations. Finally, we thank Jaxine Wolfe for assisting in data curation and Jennifer Curtis.
Author information
Authors and Affiliations
Contributions
James R. Holmquist (Data curation, Formal analysis, Software, Visualization, Writing – original draft), Lauren N. Brown (Conceptualization, Data curation, Investigation, Project administration, Writing – review & editing), Elizabeth Fard (Conceptualization, Data curation, Investigation, Project administration, Writing – review & editing), Richard F. Ambrose (Conceptualization, Funding acquisition, Writing – review & editing), Kathryn E. Hargan (Investigation, Resources, Writing – review & editing), Douglas E. Hammond (Investigation, Resources, Writing – review & editing), Nathaniel J. Kemnitz (Investigation, Resources, Writing – review & editing), John Smol (Resources, Writing - review & editing), Karen Thorne (Conceptualization, Project administration, Funding acquisition, Writing – review & editing), Glen M. MacDonald (Conceptualization, Funding acquisition, Field work, Supervision, Writing – review & editing).
Corresponding authors
Ethics declarations
Competing interests
The authors declare no competing interests.
Additional information
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
Rights and permissions
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
About this article
Cite this article
Holmquist, J.R., Brown, L.N., Fard, E. et al. Tidal Wetland Soil Carbon Accumulation Rates for Coastal California. Sci Data (2026). https://doi.org/10.1038/s41597-026-06935-8
Received:
Accepted:
Published:
DOI: https://doi.org/10.1038/s41597-026-06935-8
