Restore Ecosystems - Saltmarshes - Ocean Central
Saltmarshes are vital coastal wetlands that play an outsized role in ocean health, acting as blue carbon sinks that capture and store large amounts of carbon in their soils and biomass, helping to mitigate climate change.
They also serve as critical nurseries for fish and invertebrates, supporting coastal livelihoods and food security.
Salt marshes are being lost rapidly due to land reclamation, coastal development, and the pressures of rising seas. Their global extent, carbon sequestration potential, and economic value underline the urgency of their conservationing and restorationing them.
More resources and datasets are available via the Blue Carbon Initiative.
Key Stats
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5.45 Million Hectares
Source: Mcowen CJ, Weatherdon LV, Bochove JV, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S. A global map of saltmarshes. Biodivers Data J. 2017 Mar 21;(5):e11764. https://doi.org/10.3897/BDJ.5.e11764Global salt marsh extent.
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6–8 Tons CO₂e/hectare/yr
Carbon sequestration rate per hectare per year.
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$144 – $3,705 /hectare/year
Total annual global economic value of salt marsh services.
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43
Source: Mcowen CJ, Weatherdon LV, Bochove JV, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S. A global map of saltmarshes. Biodivers Data J. 2017 Mar 21;(5):e11764. https://doi.org/10.3897/BDJ.5.e11764Countries with saltmarshes within their EEZs.
Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes (v6.1). Biodiversity Data Journal 5: e11764. Paper DOI: https://doi.org/10.3897/BDJ.5.e11764 ; Data DOI: https://doi.org/10.34892/07vk-ws51
Globally, saltmarsh ecosystems have decreased 49.3% between 1900 and 2019.
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Temporal Coverage
The number of years of available data.
20Years
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Data Frequency
Sufficient - At least 2 data points available for trend analysis AND at least one data point in the last 7 yearsInsufficient – Does not have any data at all for analysis Expired – Does not have any data in the last 10 years Not Recent – At least one data point in the last 8 to 10 years Recent – At least one data point in the last 7 years Sufficient – At least 2 data points available for trend analysis AND at least one data point in the last 7 years
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Geographic Range
100% of global data avaliableThe percentage of the ocean represented by the available data
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Goal Assessment
2030 Goal – High Quality (Measurable)None – No Global Goal Established Low – The goal is broad Medium – The goal is specific High – The goal is measurable
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2050 Goal – High Quality (Measurable)
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Saltmarsh loss is largely driven by coastal development, agricultural expansion, and sea level rise intensified by climate change.
While restoration efforts are underway, many projects remain fragmented, underfunded, or lack long-term monitoring.
Enablers such as the EU Habitats Directive, the US Blue Carbon Initiative, Payment for Ecosystem Services (PES), blue carbon markets, and international funding are creating momentum, yet significant roadblocks persist.
These include inconsistent global mapping, limited integration into coastal planning, and weak local engagement. A key challenge remains whether enough pre-industrial or pre-development data exists to accurately model fully restored saltmarsh ecosystems.
Salt marsh restoration presents an unparalleled opportunity to enhance climate resilience, sequester carbon, restore biodiversity, and protect vulnerable coastlines.
Explore where saltmarshes are most prevalent and how those habitats are changing.
Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes (v6.1). Biodiversity Data Journal 5: e11764. Paper DOI: https://doi.org/10.3897/BDJ.5.e11764 ; Data DOI: https://doi.org/10.34892/07vk-ws51
Flanders Marine Institute (2024). The intersect of the Exclusive Economic Zones and IHO sea areas, version 5. Available online at https://www.marineregions.org/. https://doi.org/10.14284/699
There are approximately 54,550 km² of saltmarshes globally — 100% of which lie within national EEZs.
Campbell, A.D., Fatoyinbo, L., Goldberg, L. et al. Global hotspots of salt marsh change and carbon emissions. Nature 612, 701–706 (2022). https://doi.org/10.1038/s41586-022-05355-z
Globally, saltmarsh ecosystems have gained 1,361 km² and lost 2,675 km² resulting in a net change of -1,314 km² between 2000 and 2019.
Salt marsh loss stems from coastal development, land reclamation, and agriculture, now compounded by erosion and accelerating sea level rise. While global data on the exact share of each driver is still limited, sea level rise is the most consistently tracked threat.
Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes (v6.1). Biodiversity Data Journal 5: e11764. Paper DOI: https://doi.org/10.3897/BDJ.5.e11764 ; Data DOI: https://doi.org/10.34892/07vk-ws51
Sea Level Research Group, University of Colorado Boulder (no date) Sea Level Trend Map – Sea Level Trends from Satellite Altimeters. Available at: https://sealevel.colorado.edu/trend-map (Accessed: 13 January 2026).
Globally, approximately 11.64% of saltmarshes lie within areas experiencing high sea level rise.
See where salt marshes are safeguarded and how restoration efforts are expanding their coverage.
Mcowen C, Weatherdon LV, Bochove J, Sullivan E, Blyth S, Zockler C, Stanwell-Smith D, Kingston N, Martin CS, Spalding M, Fletcher S (2017). A global map of saltmarshes (v6.1). Biodiversity Data Journal 5: e11764. Paper DOI: https://doi.org/10.3897/BDJ.5.e11764 ; Data DOI: https://doi.org/10.34892/07vk-ws51
UNEP-WCMC and IUCN (2026), Protected Planet: The World Database on Protected Areas (WDPA) and World Database on Other Effective Area-based Conservation Measures (WD-OECM) [Online], January 2026, Cambridge, UK: UNEP-WCMC and IUCN. Available at: www.protectedplanet.net.
Globally, approximately 22.34% of saltmarshes lie within established protected areas.
Duarte, C.M., Agustí, S., Barbier, E., Britten, G.L., Castilla, J.C., Gattuso, J.-P., Fulweiler, R.W., Hughes, T.P., Knowlton, N., Lovelock, C.E., Lotze, H.K., Predragovic, M., Poloczanska, E., Roberts, C. and Worm, B. (2020) Rebuilding marine life. Nature, 580(7801), pp. 39–51. https://doi.org/10.1038/s41586-020-2146-7
Globally, there was an increase of 92 saltmarsh restoration projects between 1972 and 2010.
For most of human history, living nature was not given a financial value.
When saltmarshes were drained or reclaimed decades ago to make way for agriculture and coastal development, the carbon locked within their soils was not counted, priced, or considered worth protecting. Nature was treated as a free good — and as a result, vast stretches of saltmarsh were lost without any reckoning of the true cost to our climate and our coastlines.
When we lost these saltmarshes, we did not just lose grass and mud. We lost one of Earth's most carbon-dense coastal habitats - storing carbon not just in their plants, but deep within their waterlogged soils for centuries. While this platform focuses on valuing carbon, saltmarshes provide many other critical services, including:
- Flood protection (absorbing wave energy and buffering storm surges)
- Biodiversity support (vital habitats for wading birds, invertebrates, and juvenile fish)
- Water quality improvement (trapping sediments and filtering agricultural runoff)
- Shoreline stabilisation (binding sediments and reducing coastal erosion)
Atwood, T.B., Witt, A., Mayorga, J., Hammill, E. and Sala, E., 2020. Global patterns in marine sediment carbon stocks. Frontiers in Marine Science, 7, p.165. Open access: https://doi.org/10.3389/fmars.
Total Organic Carbon was obtained from Atwood et al. (2020). This value was then multiplied by 1) a stoichiometric factor to convert to CO₂ equivalent and 2) the social cost of carbon (SCC), a number that reflects the negative externalities associated with emissions of CO₂. There are a range of estimates that can be used for the SCC, and the Ecosystem Valuation tool currently implements the value defined under the Obama Administration (and repeated under the Biden Administration) of $56 (2020 dollars) per additional tonne of CO₂ equivalent emitted in 2025.
Note: The $56/tonne SCC used here comes from the U.S. Interagency Working Group's 2021 interim technical support document [1] - a science-based estimate of the economic damage from emitting one additional tonne of CO₂, rather than a market price. For context, voluntary carbon markets average around $6.34/tonne across all credit types [2], verified blue carbon credits trade in the $25–$30/tonne range [3], and compliance markets like the EU ETS sat between €60-€80/tonne through 2025 [4] - so the SCC falls somewhere in the middle, above current blue carbon market prices but well below mandatory compliance levels.
A 2026 Nature Climate Change study which found that once ocean ecosystem impacts are factored in, the SCC nearly doubles from $51 to $97/tonne, suggesting conventional frameworks may significantly understate the true cost of blue carbon loss [5].''
References:
[1] Biden Interagency Working Group on the Social Cost of Greenhouse Gases. Technical Support Document: Social Cost of Carbon, Methane, and Nitrous Oxide. February 2021.
[2] Ecosystem Marketplace. State of the Voluntary Carbon Market. 2025.
[3] S&P Global Commodity Insights. Blue Carbon Price Assessments. August 2025.
[4] Senken. Understanding Carbon Credit Prices: A Market Analysis. 2026. Available at: senken.io
[5] Bastien-Olvera, B.A. et al. Accounting for ocean impacts nearly doubles the social cost of carbon. Nature Climate Change, January 2026. https://doi.org/10.1038/
As of 2020, the global saltmarsh biomass is estimated at 71.23 million tonnes with an estimated carbon value of $14.63 billion.
As of 2020, the global saltmarsh biomass is estimated at 71.23 million tonnes with an estimated carbon value of $14.63 billion.
Evidence of their critical value:
12-20%
Möller, I., Kudella, M., Rupprecht, F. et al. Wave attenuation over coastal salt marshes under storm surge conditions. Nature Geosci 7, 727–731 (2014). https://doi.org/10.1038/ngeo2251
Wave height reduction over 40 metres of saltmarsh vegetation
~$625 million
Narayan, S., Beck, M. W., Wilson, P., Thomas, C. J., Guerrero, A., Shepard, C. C., … Trespalacios, D. (2017). The value of coastal wetlands for flood damage reduction in the northeastern USA. Scientific Reports, 7, 9463. https://doi.org/10.1038/s41598-017-09269-z
Flood damage avoided as a result of saltmarshes during Hurricane Sandy in 2012
75%
Beck, Michael W., et al. 2001. “The Identification, Conservation, and Management of Estuarine and Marine Nurseries for Fish and Invertebrates.” BioScience 51 (8): 633–641. https://doi.org/10.1641/0006-3568(2001)051[0633:TICAMO]2.0.CO;2
Amount of commercial fisheries species that use coastal marshes as a nursery habitat
We know what was lost, but how much can we bring back? Even restoring a fraction of former saltmarsh extent can deliver substantial climate and ecological benefits. Saltmarsh does not recover instantly. It recolonises gradually, season by season, as soils rewaterlog and vegetation returns. The carbon begins accumulating from the moment restoration begins.
Note:
As of June 2026. Carbon pricing is dynamic and therefore these numbers may not reflect the latest pricing but provide an indicative estimate of the ecosystem service of sequestering carbon provided by Saltmarshes. Any references to carbon pricing or carbon value are not real-time trading prices and are a scientifically assessed Social Cost of Carbon determined by the United States Goverment's Interagency Working Group on the Social Cost of Greenhouse Gases. Prices or values referenced are indicative estimates only, and should not be relied on as source material for valuation decision making purposes for restoration of ecosystems. Rather, the prices or values referenced should be used for indicative purposes only.
Restoring salt marshes is one of the most effective nature-based solutions for climate mitigation and coastal resilience. These ecosystems buffer storm surges, store carbon long-term, and support biodiversity, making their restoration essential for both people and nature.
Taking Action
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Protect Existing Marshes
Establishing new marine protected areas, inclusive of salt marshes, and strengthening legal protections can safeguard remaining salt marshes.
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Restore Hydrology
Reconnecting tidal flows and improving freshwater inflows can revitalize marshes and restore their natural processes.
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Manage Sediment
Allowing marshes to migrate inland and restoring sediment flows through reduced damming and dredging helps them thrive.
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Address Pollution
Promoting sustainable farming and fishing practices reduces nutrient runoff and other pollutants that harm marshes.
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Nature-Based Solutions
Encouraging natural coastal defense systems, like salt marshes, to combat erosion is a cost-effective strategy for climate adaptation.
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Mitigate Climate Change
Recognizing salt marshes as key carbon sinks and incorporating them into climate strategies is crucial for long-term preservation.
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Marine Spatial Planning
Comprehensive marine and coastal zoning plans that prioritize conservation and restoration efforts can ensure sustainable management of salt marshes.
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Engage Communities
Involving local communities and stakeholders ensures the success and sustainability of restoration efforts.
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Create Financial Incentives
Developing markets for the ecosystem services provided by salt marshes, such as carbon sequestration and flood protection, can attract investment in marsh restoration.
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Research and Monitoring
Ongoing scientific research and long-term monitoring will help track restoration success and inform best practices.
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Enhance International Alignment
Linking the benefits of salt marshes to the UN’s Sustainable Development Goals, aligning national and international policies, and fostering international collaboration encourages the protection and recovery of these vital ecosystems.
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By regenerating salt marshes at low cost, this model boosts blue carbon storage, safeguards migratory birds, and offers a scalable solution for climate adaptation worldwide.
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View relevant data layers on the globe using the available map toggle in the top right of each card in the left panel.
View relevant data layers on the globe using the available map toggle in the top right of each card in the left panel.