Restore Ecosystems - Seagrasses - Ocean Central
Seagrasses are flowering plants that form dense underwater meadows in shallow coastal waters worldwide.
These ecosystems are ecological powerhouses: they stabilize sediments, improve water clarity, and provide vital shelter for juvenile fish and other marine life. They are among the most effective ecosystems for carbon sequestration, storing vast amounts of carbon in their roots and soils, which makes them a cornerstone of blue carbon habitats.
As nurseries for countless marine species, seagrasses support both biodiversity goals. They also support climate goals through long-term carbon storage.
Despite their immense value, seagrass meadows are in steep decline, threatened by coastal pollution, dredging, and physical damage from boating. Establishing a global baseline of their extent, species diversity, and ecosystem service value is critical to guiding protection and restoration.
Explore more at seagrasswatch.org.
Key Stats
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~314,000 km²
Source: UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). https://resources.unep-wcmc.org/products/aaa46cd3d3d640b2916b8f0a0ffe07cbGlobal seagrass extent.
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83,000 Tons of CO₂e
Source: Fourqurean, J.W., Duarte, C.M., Kennedy, H., Marbà, N., Holmer, M., Mateo, M.A., Apostolaki, E.T., Kendrick, G.A., Krause-Jensen, D., McGlathery, K.J. and Serrano, O., 2012. Seagrass ecosystems as a globally significant carbon stock. Nature Geoscience, 5(7), pp.505–509. https://www.oceanfdn.org/sites/default/files/Seagrass%20ecosystems.pdfCarbon sequestration rate per hectare per year.
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$28-30 Billion/Year
Source: Costanza, R., de Groot, R., Sutton, P., van der Ploeg, S., Anderson, S.J., Kubiszewski, I. and Turner, R.K., 2014. Changes in the global value of ecosystem services. Global Environmental Change, 26, pp.152–158. https://www.sciencedirect.com/science/article/abs/pii/S0959378014000685Total global economic value of seagrass services.
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159
Source: IUCN (International Union for Conservation of Nature) (2025) The IUCN Red List of Threatened Species. Available at: https://www.iucnredlist.org (Accessed: December 12 2025).Number of countries with mapped seagrass.
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76
Source: IUCN (International Union for Conservation of Nature) (2025) The IUCN Red List of Threatened Species. Available at: https://www.iucnredlist.org (Accessed: December 12 2025).Seagrass species globally.
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7%
Source: Waycott, M., Duarte, C.M., Carruthers, T.J.B., Orth, R.J., Dennison, W.C., Olyarnik, S., Calladine, A., Fourqurean, J.W., Heck, K.L., Hughes, A.R. and Kendrick, G.A., 2009. Accelerating loss of seagrasses across the globe threatens coastal ecosystems. Proceedings of the National Academy of Sciences, 106(30), pp.12377–12381. https://www.pnas.org/doi/10.1073/pnas.0905620106Seagrass loss rate per year.
UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. Data DOI: https://doi.org/10.34892/x6r3-d211
Globally, seagrass ecosystems have decreased 28.5% between 1900 and 2020.
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Temporal Coverage
The number of years of available data.
1Year
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Data Frequency
Recent – 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 availableThe 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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Seagrass meadows face mounting pressures from pollution, sedimentation that reduces water clarity, and physical damage from activities such as anchoring and trawling.
While monitoring and restoration efforts have improved significantly in regions such as Europe, Australia, and North America, significant gaps remain in Africa, South Asia, and parts of Oceania, where limited data and financial capacity impede effective management.
At the same time, momentum for seagrass protection is growing. Citizen science programs such as Seagrass Watch are closing knowledge gaps and empowering local stewardship. Seagrasses are now explicitly recognized in global climate and biodiversity frameworks, including the UN Decade on Ecosystem Restoration, blue carbon initiatives, and emerging carbon markets, positioning them as critical nature-based solutions for carbon storage, coastal resilience, and biodiversity recovery.
However, restoration remains challenging, with low recovery rates and high costs limiting large-scale progress. To reverse seagrass decline, restoration must be paired with strong policy, spatial planning, and long-term investment.
Explore where seagrasses are most prevalent.
UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. Data DOI: https://doi.org/10.34892/x6r3-d211
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 314,000 km² of seagrass globally — over 97% of which lie within national EEZs.
Seagrasses are threatened by global pressures like warming and acidification. They begin to become stressed and die when waters reach 40°C, making rising temperatures a critical risk.
UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. Data DOI: https://doi.org/10.34892/x6r3-d211.
National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch (n.d.) Daily Global 5km Satellite Marine Heatwave Watch (MHW) product. NOAA Coral Reef Watch. Available at: https://coralreefwatch.noaa.gov/product/marine_heatwave/ (Accessed: 24 July 2025).
Globally, approximately 31.88% of seagrasses lie within areas experiencing marine heatwaves.
UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. Data DOI: https://doi.org/10.34892/x6r3-d211
Gregor, L. and Gruber, N.: OceanSODA-ETHZ: a global gridded data set of the surface ocean carbonate system for seasonal to decadal studies of ocean acidification, Earth Syst. Sci. Data, 13, 777–808, https://doi.org/10.5194/essd-13-777-2021, 2021
NOTE: Negative pH values and trends indicate increasing ocean acidification
Significant Increasing Acidity Trend – Any pixel where the p-value of a linear trend line is less than 0.05, based on data over the period 1982-2022.
Globally, approximately 51.62% of seagrasses lie within areas experiencing increasing acidification.
IUCN (International Union for Conservation of Nature) (2025) The IUCN Red List of Threatened Species. Available at: https://www.iucnredlist.org (Accessed: December 12 2025).
Globally, there are 73 species of seagrass tracked by the IUCN out of which 3 are endangered which have a significant opportunity for recovery with timely action.
| Species | Status |
|---|---|
| Althenia filiformis | DD |
| Halophila euphlebia | DD |
| Halophila sulawesii | DD |
| Halodule beaudettei | DD |
| Halodule ciliata | DD |
| Halodule emarginata | DD |
| Lepilaena australis | DD |
| Lepilaena marina | DD |
| Ruppia filifolia | DD |
| Halodule bermudensis | DD |
| Heterozostera chilensis | EN |
| Phyllospadix japonicus | EN |
| Zostera geojeensis | EN |
| Posidonia oceanica | LC |
| Cymodocea nodosa | LC |
| Zostera marina | LC |
| Ruppia cirrhosa | LC |
| Ruppia maritima | LC |
| Halophila ovalis | LC |
| Halophila stipulacea | LC |
| Phyllospadix torreyi | LC |
| Posidonia kirkmanii | LC |
| Ruppia polycarpa | LC |
| Halophila johnsonii | LC |
| Halodule pinifolia | LC |
| Halodule uninervis | LC |
| Halophila tricostata | LC |
| Enhalus acoroides | LC |
| Syringodium isoetifolium | LC |
| Posidonia angustifolia | LC |
| Cymodocea angustata | LC |
| Halophila spinulosa | LC |
| Thalassia testudinum | LC |
| Nanozostera japonica | LC |
| Posidonia denhartogii | LC |
| Ruppia megacarpa | LC |
| Halophila decipiens | LC |
| Heterozostera tasmanica | LC |
| Heterozostera nigricaulis | LC |
| Amphibolis antarctica | LC |
| Cymodocea serrulata | LC |
| Amphibolis griffithii | LC |
| Nanozostera noltii | LC |
| Cymodocea rotundata | LC |
| Thalassia hemprichii | LC |
| Halophila capricorni | LC |
| Phyllospadix serrulatus | LC |
| Phyllospadix scouleri | LC |
| Halophila ovata | LC |
| Posidonia coriacea | LC |
| Halophila australis | LC |
| Halodule wrightii | LC |
| Zostera pacifica | LC |
| Thalassodendron ciliatum | LC |
| Halophila minor | LC |
| Ruppia tuberosa | LC |
| Syringodium filiforme | LC |
| Posidonia ostenfeldii | LC |
| Heterozostera polychlamys | LC |
| Thalassodendron pachyrhizum | LC |
| Nanozostera muelleri | LC |
| Posidonia australis | NT |
| Zostera caulescens | NT |
| Halophila engelmanni | NT |
| Zostera asiatica | NT |
| Halophila nipponica | NT |
| Halophila hawaiiana | VU |
| Halophila beccarii | VU |
| Phyllospadix iwatensis | VU |
| Posidonia sinuosa | VU |
| Zostera caespitosa | VU |
| Nanozostera capensis | VU |
| Halophila baillonii | VU |
See where seagrass is safeguarded and how restoration efforts are expanding their coverage.
UNEP-WCMC, Short FT (2021). Global distribution of seagrasses (version 7.1). Seventh update to the data layer used in Green and Short (2003). Cambridge (UK): UN Environment World Conservation Monitoring Centre. Data DOI: https://doi.org/10.34892/x6r3-d211
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 28.47% of seagrass 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 250 seagrass restoration projects between 1943 and 2016.
For most of human history, living nature was not given a financial value.
When seagrass meadows were smothered by pollution, scarred by boat anchors, or lost to coastal development over recent decades, the carbon stored within them was not measured, traded, or treated as something worth saving. Nature was treated as a free good – and as a result, seagrass meadows disappeared across the world's coastlines without anyone counting the true cost.
When we lost these meadows, we did not just lose underwater grass. We lost one of the ocean's most productive and quietly powerful ecosystems - capturing carbon at rates that rival terrestrial forests, while supporting extraordinary marine life. While this platform focuses on valuing carbon, seagrass meadows provide many other critical services, including:
- Coastal protection (dampening wave energy and stabilising seafloor sediments)
- Biodiversity support (nursery habitat for fish, seahorses, and marine invertebrates)
- Water quality improvement (filtering nutrients, trapping fine particles, and oxygenating water)
- Food web support (a foundational food source for turtles, dugongs, and countless species)
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 seagrass biomass is estimated at 20.45 million tonnes with an estimated carbon value of $199 million.
As of 2020, the global seagrass biomass is estimated at 20.45 million tonnes with an estimated carbon value of $199 million.
Evidence of their critical value:
~$6.4 Trillion Annually
Duarte, C. M., Apostolaki, E. T., Serrano, O., et al. (2025). Conserving seagrass ecosystems to meet global biodiversity and climate goals. Nature Reviews Biodiversity, 1, 150–165. https://doi.org/10.1038/s44358-025-00028-x
Estimated total ecosystem services inclusive of carbon sequestration
$3,500 per Hectare per Year
National Research Council. (2005). Valuing Ecosystem Services: Toward Better Environmental Decision-Making. National Academies Press. https://nap.nationalacademies.org/catalog/11139/valuing-ecosystem-services-toward-better-environmental-decision-making
Estimated value of fisheries support seagrass ecosystem services
~$1.9 Trillion
National Research Council. (2005). Valuing Ecosystem Services: Toward Better Environmental Decision-Making. National Academies Press. https://nap.nationalacademies.org/catalog/11139/valuing-ecosystem-services-toward-better-environmental-decision-making
Global estimated value of seagrass nutrient cycling services
20%
Unsworth, R. K. F., Nordlund, L. M., & Cullen-Unsworth, L. C. (2018). Seagrass meadows support global fisheries productivity through nursery habitat provision. (Synthesized in later reviews, including Nature Reviews Biodiversity ecosystem service assessments).
Proportion of world's largest global fisheries with seagrasses as a nursery habitat for hundreds of fish species
€200 Million
UN Environment Programme. (2020). Out of the Blue: The Value of Seagrasses to the Environment and to People. https://www.unep.org/resources/report/out-blue-value-seagrasses-environment-and-people
Estimated seagrass ecosystem services contribution to fisheries in the Mediterranean alone
We know what was lost, but how much can we bring back? Even modest restoration of seagrass extent can unlock significant climate and ecological value. Seagrass does not return quickly. It spreads slowly, shoot by shoot, as roots take hold and meadows begin to form. The value of that restoration begins the moment seeds are sown.
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 Seagrasses. 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.
Seagrass restoration boosts marine life, stabilizes sediments, and captures carbon, supporting both biodiversity and climate mitigation.
Taking Action
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Coastal Development
Expanding cities and infrastructure, such as hotels and piers, degrade seagrass habitats through dredging and land reclamation, which disrupt sediment and light essential for their growth.
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Climate Change
Rising sea temperatures and increased storms can damage or uproot seagrass meadows, while ocean acidification impacts their growth. Sea level rise also reduces the sunlight that reaches these plants.
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Water Pollution
Industrial runoff and agricultural fertilizers lead to algal blooms that block sunlight, stunting seagrass growth and degrading their ecosystems.
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Unsustainable Recreation
Activities such as boating stir up sediment, reducing water clarity and affecting seagrass growth. Boat anchors and chains dropped onto seagrass harm the meadows.
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Overfishing and Trawling
Certain fishing practices, particularly the use of bottom trawling and dredging physically damage seagrass roots and sediment beds.
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Invasive Species and Disease
Non-native species outcompete or overgraze seagrass, while diseases like seagrass wasting disease threaten their survival, exacerbated by warming waters.
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Hydrological Changes
Dams and other water control structures that cause water diversion reduce the flow of freshwater and sediments to coastal areas affecting plant growth and habitat health.
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Project Seagrass shows that large-scale restoration is achievable when science and community come together to regenerate the ocean from the grassroots up. -
This project set a precedent for large-scale marine restoration in Europe, demonstrating that protecting seagrass delivers climate mitigation, fisheries recovery, and coastal resilience all at once. -
Restoring seagrass meadows revives fish habitat, boosts carbon storage, and empowers communities to lead ocean regeneration—not just for nature but for the climate and coastal livelihoods.
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.
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.