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Blue carbon is a concept within climate change mitigation that refers to "biologically driven carbon fluxes and storage in marine systems that are amenable to management".^[2]^: 2220 Most commonly, it refers to the role that tidal marshes, mangroves and seagrass meadows can play in carbon sequestration.^[2]^: 2220 These ecosystems can play an important role for climate change mitigation and ecosystem-based adaptation. However, when blue carbon ecosystems are degraded or lost, they release carbon back to the atmosphere, thereby adding to greenhouse gas emissions.^[2]^: 2220

The methods for blue carbon management fall into the category of "ocean-based biological carbon dioxide removal (CDR) methods".^[3]^: 764 They are a type of biological carbon fixation.

Scientists are looking for ways to further develop the blue carbon potential of ecosystems.^[4] However, the long-term effectiveness of blue carbon as a carbon dioxide removal solution is under debate.^[5]^[4]^[6]

The term deep blue carbon is also in use and refers to storing carbon in the deep ocean waters.^[7]

Definition

Blue carbon is defined by the IPCC as "Biologically driven carbon fluxes and storage in marine systems that are amenable to management."^[2]^: 2220

Another definition states: "Blue carbon refers to organic carbon that is captured and stored by the oceans and coastal ecosystems, particularly by vegetated coastal ecosystems: seagrass meadows, tidal marshes, and mangrove forests."^[8]

Coastal blue carbon focuses on "rooted vegetation in the coastal zone, such as tidal marshes, mangroves and seagrasses". Seagrass, salt marshes and mangroves are sometimes referred to as "blue forests" in contrast to land-based "green forests".^[9]^[10]

Deep blue carbon is located in the high seas beyond national jurisdictions.^[11] It includes carbon contained in "continental shelf waters, deep-sea waters and the sea floor beneath them" and makes up 90% of all ocean carbon.^[12] Deep blue carbon is generally seen as "less amenable to management" and challenging due to lack of data "relating to the permanence of their carbon stores".^[3]^: 764

Role in climate change context

The term blue carbon was coined in 2009.^[13]^[8] At the time, the term was coined to highlight that coastal vegetated ecosystems have a disproportionately large contribution to global carbon sequestration.^[8] Others use the term to describe the carbon captured by the entire ocean, not just the coastal ecosystems.^[14] The role of blue carbon in climate change mitigation and adaptation has now reached international prominence.^[8]

The vegetated coastal ecosystems of tidal marshes, mangroves and seagrasses (which are grouped as "blue carbon") have high carbon burial rates. This is because they accumulate carbon in their soils and sediments.^[2]^: 2220

Such ecosystems can contribute to climate change mitigation and also to ecosystem-based adaptation. However, when coastal blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere.^[2]^: 2220

Mangroves, salt marshes and seagrasses can store carbon and are highly efficient carbon sinks. They capture CO₂ from the atmosphere by sequestering the carbon in their underlying sediments, in underground and below-ground biomass, and in dead biomass.^[15]

Although vegetated coastal ecosystems cover less area and have less aboveground biomass than terrestrial plants they have the potential to impact long term C sequestration, particularly in sediment sinks.^[16]

One of the main concerns with blue carbon is that the rate of loss of these important marine ecosystems is much higher than any other ecosystem on the planet, even compared to rainforests. Current estimates suggest a loss of 2-7% per year, which is not only lost carbon sequestration, but also lost habitat that is important for managing climate, coastal protection, and health.^[16]

As habitats that sequester carbon are altered and decreased, that stored amount of C is being released into the atmosphere, continuing the current accelerated rate of climate change. Impacts on these habitats globally will directly and indirectly release the previously stored carbon, which had been sequestered in the sediments of these habitats. Declines in vegetated coastal habitats are seen worldwide.

Quantifying rates of decrease are difficult to calculate, however measurements have been estimated by researchers indicating that if blue carbon ecosystems continue to decline, for any number of reasons, 30-40% of tidal marshes and seagrasses and approximately 100% of mangroves could be gone in the next century.^[19]

Reasons for the decline of mangroves, seagrass, and marshes include land use changes, climate and drought related effects, dams built in the watershed, convergence to aquaculture and agriculture, land development and sea-level rise due to climate change. Increases in these activities can lead to significant decreases in habitat availability and thus increases in released C from sediments.

As anthropogenic effects and climate change are heightened, the effectiveness of blue carbon sinks will diminish and CO₂ emissions will be further increased. Data on the rates at which CO₂ is being released into the atmosphere is not robust currently; however, research is being conducted to gather better information to analyze trends. Loss of underground biomass (roots and rhizomes) will allow for CO₂ to be emitted changing these habitats into sources rather than carbon sinks.^[20]

Impacts of nutrient load

Increases in carbon capture and sequestration have been observed in both mangrove and seagrass ecosystems which have been subjected to high nutrient loads, either intentionally or due to waste from human activities.^[21]

Research done on mangrove soils from the Red Sea have shown that increases in nutrient loads to these soils do not increase carbon mineralization and subsequent CO₂ release.^[22] This neutral effect of fertilization was not found to be true in all mangrove forest types. Carbon capture rates also increased in these forests due to increased growth rates of the mangroves. In forests with increases in respiration there were also increases in mangrove growth of up to six times the normal rate.^[23]

Carbon storage by type of biome

Tidal marshes

Tidal marshes can be found globally on coastlines from the arctic to the subtropics. They are intertidal ecosystems dominated by herbaceous vegetation. In the tropics, marshes are replaced by mangroves as the dominant coastal vegetation.^[24]

Marshes have high productivity, with a large portion of primary production in belowground biomass.^[24] This belowground biomass can form deposits up to 8m deep.^[24] Marshes provide valuable habitat for plants, birds, and juvenile fish, protect coastal habitat from storm surge and flooding, and can reduce nutrient loading to coastal waters.^[25] Similarly to mangrove and seagrass habitats, marshes also serve as important carbon sinks.^[26] Marshes sequester C in underground biomass due to high rates of organic sedimentation and anaerobic-dominated decomposition.^[26] Salt marshes cover approximately 22,000 to 400,000 km² globally, with an estimated carbon burial rate of 210 g C m⁻² yr⁻¹.^[24]

Salt marshes may not be expansive worldwide in relation to forests, but they have a C burial rate that is over 50 times faster than tropical rainforests. Rates of burial have been estimated at up to 87.2 ± 9.6 Tg C yr⁻¹ which is greater than that of tropical rainforests, 53 ± 9.6 Tg C yr⁻¹.^[20] Since the 1800s salt marshes have been disturbed due to development and a lack of understanding of their importance. The 25% decline since that time has led to a decrease in potential C sink area coupled with the release of once buried C. Consequences of increasingly degraded marsh habitat are a decrease in C stock in sediments, a decrease in plant biomass and thus a decrease in photosynthesis reducing the amount of CO₂ taken up by the plants, failure of C in plant blades to be transferred into the sediment, possible acceleration of erosive processes due to the lack of plant biomass, and acceleration of buried C release to the atmosphere.^[20]

Tidal marshes have been impacted by humans for centuries, including modification for grazing, haymaking, reclamation for agriculture, development and ports, evaporation ponds for salt production, modification for aquaculture, insect control, tidal power and flood protection.^[27] Marshes are also susceptible to pollution from oil, industrial chemicals, and most commonly, eutrophication. Introduced species, sea-level rise, river damming and decreased sedimentation are additional longterm changes that affect marsh habitat, and in turn, may affect carbon sequestration potential.^[28]

Mangroves

Globally, mangroves stored 4.19 ± 0.62 Pg (CI 95%) of carbon in 2012, with Indonesia, Brazil, Malaysia and Papua New Guinea accounting for more than 50% of the global stock.^[29] 2.96 ± 0.53 Pg of the global carbon stock is contained within the soil and 1.23 ± 0.06 Pg in the living biomass.^[29] Of this 1.23 Pg, approximately 0.41 ± 0.02 Pg is in the belowground biomass in the root system and approximately 0.82 ± 0.04 Pg is in the aboveground living biomass.^[29]

Global mangrove canopy cover is estimated as between 83,495 km² and 167,387 km² in 2012 with Indonesia containing approximately 30% of the entire global mangrove forest area.^[30] Mangrove forests are responsible for approximately 10% of global carbon burial,^[31] with an estimated carbon burial rate of 174 g C m⁻² yr⁻¹.^[32]

Mangroves, like seagrasses, have potential for high levels of carbon sequestration. They account for 3% of the global carbon sequestration by tropical forests and 14% of the global coastal ocean's carbon burial.^[33]

Mangroves are naturally disturbed by floods, tsunamis, coastal storms like cyclones and hurricanes, lightning, disease and pests, and changes in water quality or temperature.^[32] Although they are resilient to many of these natural disturbances, they are highly susceptible to human impacts including urban development, aquaculture, mining, and overexploitation of shellfish, crustaceans, fish and timber.^[34]^[32] Mangroves provide globally important ecosystem services and carbon sequestration and are thus an important habitat to conserve and repair when possible.^[35]^[36]

Dams threaten habitats by slowing the amount of freshwater reaching mangroves. Coral reef destruction also plays a role in mangrove habitat health as reefs slow wave energy to a level that mangroves are more tolerant of.

Seagrass meadows

Although seagrass makes up only 0.1% of the area of the ocean floor, it accounts for approximately 10–18% of the total oceanic carbon burial.^[37] Currently global seagrass meadows are estimated to store as much as 19.9 Pg (gigaton, or billion tons) of organic carbon.^[37] There has been considerable attention to how large-scale seaweed cultivation in the open ocean can act as a form of carbon sequestration.^[38]^[39] Studies have demonstrated that nearshore seaweed forests constitute a source of blue carbon, as seaweed detritus is carried by wave currents into the middle and deep ocean thereby sequestering carbon.^[38]^[40]^[41]^[42]^[43]

Carbon primarily accumulates in marine sediments, which are anoxic and thus continually preserve organic carbon from decadal-millennial time scales. High accumulation rates, low oxygen, low sediment conductivity and slower microbial decomposition rates all encourage carbon burial and carbon accumulation in these coastal sediments.^[44]

Compared to terrestrial habitats that lose carbon stocks as CO₂ during decomposition or by disturbances like fires or deforestation, marine carbon sinks can retain C for much longer time periods. Carbon sequestration rates in seagrass meadows vary depending on the species, characteristics of the sediment, and depth of the habitats, but on average the carbon burial rate is approximately 138 g C m⁻² yr⁻¹.^[45]

Seagrass habitats are threatened by coastal eutrophication, increased seawater temperatures,^[44] increased sedimentation and coastal development,^[45] and sea level rise which may decrease light availability for photosynthesis. Seagrass loss has accelerated over the past few decades, from 0.9% per year prior to 1940 to 7% per year in 1990, with about 1/3 of global loss since WWII.^[46] The decline in seagrasses is due to a number of factors including drought, water quality issues, agricultural practices, invasive species, pathogens, fishing and climate change.^[47]

Scientists encourage the protection and continued research of these ecosystems for organic carbon storage, valuable habitat and other ecosystem services.

Restored seagrass meadows were found to start sequestering carbon in sediment within about four years. This was the time needed for the meadow to reach sufficient shoot density to cause sediment deposition.^[48]

Deep ocean

The deeper layers of the ocean are greatly unsaturated in CO₂ and its dissolved forms, carbonic and bicarbonic acid, and their salts.^[50] At depths greater than 3 km, CO₂ becomes liquefied and sinks to the seafloor due to it being higher density than the surrounding seawater. Mathematical models have shown that CO₂ stored in deep sea sediments beyond 3 km could provide permanent geological storage^[51] even with large geomechanical perturbations. Deep ocean storage can present a potential sink for large amounts of anthropogenic CO₂.^[52] Other deep water carbon storage techniques currently being explored include, seaweed farming and algae, ocean fertilization, artificial upwelling, and basalt storage.

The deep blue carbon terminology has been used in passing as early as 2017.^[53] The Ocean Frontier Institute has made it a centrepiece of their participation at COP27.^[54] It is investing significant resources into deep blue carbon research.^[55] In terms of net-new-carbon sequestration deep blue carbon offers an estimated 10-20 times higher potential than coastal blue carbon to achieve net-zero goals.^[56] There is still a lack of data in this area along with financial, ecological and environmental concerns.^[55] Advancements in research and technical capabilities are raising international interest in this kind of storage.^[57]^[11]^[58]

Example projects

Microsoft and Running Tide signed Two-Year agreement in 2023 to remove up to 12,000 tons of carbon through an ocean-based carbon removal system.^[59]
In Canada, a North Atlantic Carbon Observatory (NACO) project is underway to establish an accurate measurement of the ocean's ability to continue to absorb carbon with particular emphasis on deep blue capacity.^[60]^[61]
In Denmark, the "Greensand" project is underway to capture carbon at source and deposit it in the deep blue regions of the North Sea, creating a 'CO₂ graveyard'. The project is expected to store up to eight million tonnes of CO₂ per year by 2030.^[62]
A restoration project in South Australia will cover 2,000 ha (4,900 acres) of mangroves, salt marsh and sea grasses extending 700 km (430 mi) in the St Vincents Gulf and Spencer Gulf in South Australia. The project will also look at various possibilities of insuring the huge expanse of existing blue carbon ecosystems.^[63]
In South Korea, macroalgae have been utilized as part of a climate change mitigation program. The country has established the Coastal CO₂ Removal Belt (CCRB) which is composed of artificial and natural ecosystems. The goal is to capture carbon using large areas of kelp forest.^[64]
Marine permaculture also fixes carbon in seaweed forest projects offshore in Tasmania and the Philippines, with potential use from the tropics to temperate oceans.^[65]

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^ Waycott, M (2009). "Accelerating loss of seagrasses across the globe threatens coastal ecosystems". Proceedings of the National Academy of Sciences of the USA. 106 (30): 12377–12381. Bibcode:2009PNAS..10612377W. doi:10.1073/pnas.0905620106. PMC 2707273. PMID 19587236.
^ Orth, Robert J.; Carruthers, Tim J. B.; Dennison, William C.; Duarte, Carlos M.; Fourqurean, James W.; Heck, Kenneth L.; Hughes, A. Randall; Kendrick, Gary A.; Kenworthy, W. Judson (2006-12-01). "A Global Crisis for Seagrass Ecosystems". BioScience. 56 (12): 987–996. doi:10.1641/0006-3568(2006)56[987:AGCFSE]2.0.CO;2. hdl:10261/88476. ISSN 0006-3568. S2CID 4936412.
^ Greiner, J. T.; McGlathery, K. J.; Gunnell, J.; McKee, B. A. (2013). "Seagrass restoration enhances "blue carbon" sequestration in coastal waters". PLOS ONE. 8 (8): e72469. Bibcode:2013PLoSO...872469G. doi:10.1371/journal.pone.0072469. PMC 3743776. PMID 23967303.
^ Bax, Narissa; Barnes, David K. A.; Pineda-Metz, Santiago E. A.; Pearman, Tabitha; Diesing, Markus; Carter, Stefanie; Downey, Rachel V.; Evans, Chris D.; Brickle, Paul; Baylis, Alastair M. M.; Adler, Alyssa M.; Guest, Amy; Layton, Kara K. S.; Brewin, Paul E.; Bayley, Daniel T. I. (2022-06-10). "Towards Incorporation of Blue Carbon in Falkland Islands Marine Spatial Planning: A Multi-Tiered Approach". Frontiers in Marine Science. 9: 872727. doi:10.3389/fmars.2022.872727. hdl:2164/18700. ISSN 2296-7745.
^ "Ocean acidification". www.noaa.gov. Retrieved 2023-05-09.
^ House, Kurt Zenz; Schrag, Daniel P.; Harvey, Charles F.; Lackner, Klaus S. (2006). "Permanent carbon dioxide storage in deep-sea sediments". Proceedings of the National Academy of Sciences. 103 (33): 12291–12295. Bibcode:2006PNAS..10312291H. doi:10.1073/pnas.0605318103. PMC 1567873. PMID 16894174.
^ Leung, Dennis Y.C.; Caramanna, Giorgio; Maroto-Valer, M. Mercedes (2014). "An overview of current status of carbon dioxide capture and storage technologies". Renewable and Sustainable Energy Reviews. 39: 426–443. Bibcode:2014RSERv..39..426L. doi:10.1016/j.rser.2014.07.093. S2CID 73620527.
^ "Deep blue carbon storage". EurekAlert!. Retrieved 2023-05-09.
^ "The Importance of Deep Blue Carbon".
^ ^a ^b "Ocean-Based Carbon Dioxide Removal: Deep Sea Storage". Ocean Visions. Retrieved 2023-05-09.
^ "A Research Strategy for Ocean Carbon Dioxide Removal and Sequestration". National Academies of Sciences, Engineering, and Medicine. Retrieved 2023-05-09.
^ "Carbon dioxide could be stored below ocean floor, research shows". ScienceDaily. Retrieved 2023-05-09.
^ BAS-WOHLERT, Camille. "Undersea graveyard for imported CO2 opens in Denmark". phys.org. Retrieved 2023-05-09.
^ "RUNNING TIDE BECOMES MICROSOFT'S FIRST OPEN OCEAN-BASED CARBON REMOVAL SUPPLIER". 10 March 2023.
^ "Concept Brief: Ocean Carbon Observatory" (PDF).
^ "North Atlantic Carbon Observatory (NACO)". www.ofi.ca. Retrieved 2023-05-09.
^ "Denmark, the first country to import CO2 and bury it undersea". 8 March 2023.
^ Sutton, Malcolm (13 August 2021). "Blue carbon to create 'insurable' value from muddy wetlands in South Australia". ABC News. Australian Broadcasting Corporation. Archived from the original on 16 August 2021. Retrieved 16 August 2021.
^ Chung, I. K., Oak, J. H., Lee, J. A., Shin, J. A., Kim, J. G., & Park, K. S. (2013). Installing kelp forests/seaweed beds for mitigation and adaptation against global warming: Korean Project Overview. ICES Journal of Marine Science: Journal du Conseil, fss206.
^ Bryce, Emma (6 July 2020). "Can the Forests of the World's Oceans Contribute to Alleviating the Climate Crisis?". Resilience. Archived from the original on 17 April 2021. Retrieved 16 August 2021.

External links

[Huxham2018-1] Huxham, M.; Whitlock, D.; Githaiga, M.; Dencer-Brown, A. (2018). "Carbon in the Coastal Seascape: How Interactions Between Mangrove Forests, Seagrass Meadows and Tidal Marshes Influence Carbon Storage". Current Forestry Reports. 4 (2): 101–110. Bibcode:2018CForR...4..101H. doi:10.1007/s40725-018-0077-4. S2CID 135243725. Material was copied from this source, which is available under a Creative Commons Attribution 4.0 International License. Archived 2017-10-16 at the Wayback Machine.

[IPCC_AR6_WGI_Glossary-2] ^ ^a ^b ^c ^d ^e ^f IPCC, 2021: Annex VII: Glossary [Matthews, J. B. R., V. Möller, R. van Diemen, J. S. Fuglestvedt, V. Masson-Delmotte, C. Méndez, S. Semenov, A. Reisinger (eds.)]. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, doi:10.1017/9781009157896.022.

[:2-3] Canadell, J. G., P. M. S. Monteiro, M. H. Costa, L. Cotrim da Cunha, P. M. Cox, A. V. Eliseev, S. Henson, M. Ishii, S. Jaccard, C. Koven, A. Lohila, P. K. Patra, S. Piao, J. Rogelj, S. Syampungani, S. Zaehle, and K. Zickfeld, 2021: Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks. In Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, doi:10.1017/9781009157896.007.

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[47] Orth, Robert J.; Carruthers, Tim J. B.; Dennison, William C.; Duarte, Carlos M.; Fourqurean, James W.; Heck, Kenneth L.; Hughes, A. Randall; Kendrick, Gary A.; Kenworthy, W. Judson (2006-12-01). "A Global Crisis for Seagrass Ecosystems". BioScience. 56 (12): 987–996. doi:10.1641/0006-3568(2006)56[987:AGCFSE]2.0.CO;2. hdl:10261/88476. ISSN 0006-3568. S2CID 4936412.

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[51] House, Kurt Zenz; Schrag, Daniel P.; Harvey, Charles F.; Lackner, Klaus S. (2006). "Permanent carbon dioxide storage in deep-sea sediments". Proceedings of the National Academy of Sciences. 103 (33): 12291–12295. Bibcode:2006PNAS..10312291H. doi:10.1073/pnas.0605318103. PMC 1567873. PMID 16894174.

[52] Leung, Dennis Y.C.; Caramanna, Giorgio; Maroto-Valer, M. Mercedes (2014). "An overview of current status of carbon dioxide capture and storage technologies". Renewable and Sustainable Energy Reviews. 39: 426–443. Bibcode:2014RSERv..39..426L. doi:10.1016/j.rser.2014.07.093. S2CID 73620527.

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[56] "A Research Strategy for Ocean Carbon Dioxide Removal and Sequestration". National Academies of Sciences, Engineering, and Medicine. Retrieved 2023-05-09.

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[62] "Denmark, the first country to import CO2 and bury it undersea". 8 March 2023.

[sutton2021-63] Sutton, Malcolm (13 August 2021). "Blue carbon to create 'insurable' value from muddy wetlands in South Australia". ABC News. Australian Broadcasting Corporation. Archived from the original on 16 August 2021. Retrieved 16 August 2021.

[Chung2013-64] Chung, I. K., Oak, J. H., Lee, J. A., Shin, J. A., Kim, J. G., & Park, K. S. (2013). Installing kelp forests/seaweed beds for mitigation and adaptation against global warming: Korean Project Overview. ICES Journal of Marine Science: Journal du Conseil, fss206.

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+{{Short description|Carbon stored in coastal and marine ecosystems}}
-'''Blue carbon''' is the [[carbon]] captured by the world’s [[ocean]]s and coastal [[ecosystem]]s. The carbon captured by living organisms in oceans is stored in the form of [[biomass]] and [[sediment]]s from [[mangrove]]s, [[salt marsh]]es and [[seagrass]]es.<ref>Nellemann, Christian et al. (2009): Blue Carbon. The Role of Healthy Oceans in Binding Carbon. A Rapid Response Assessment. Arendal, Norway: UNEP/GRID-Arendal</ref>
+[[File:Ways_one_blue_carbon_habitat_can_influence_carbon_processing_in_an_adjacent_habitat.webp|thumb|Ways one blue carbon habitat can influence the carbon concentration and future [[carbon sequestration]] in an adjacent blue carbon habitat<ref name= Huxham2018>{{cite journal |doi = 10.1007/s40725-018-0077-4 |title = Carbon in the Coastal Seascape: How Interactions Between Mangrove Forests, Seagrass Meadows and Tidal Marshes Influence Carbon Storage |year = 2018 |last1 = Huxham |first1 = M. |last2 = Whitlock |first2 = D. |last3 = Githaiga |first3 = M. |last4 = Dencer-Brown |first4 = A. |journal = Current Forestry Reports |volume = 4 |issue = 2 |pages = 101–110 |s2cid = 135243725 |doi-access = free|bibcode = 2018CForR...4..101H }} [[File:CC-BY icon.svg|50px]] Material was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License]. {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=2017-10-16 }}.</ref>]]
+'''Blue carbon''' is a concept within [[climate change mitigation]] that refers to "biologically driven carbon fluxes and storage in marine systems that are amenable to management".<ref name="IPCC AR6 WGI Glossary" />{{rp|2220}} Most commonly, it refers to the role that [[tidal marsh]]es, [[mangrove]]s and [[Seagrass meadow|seagrass meadows]] can play in [[carbon sequestration]].<ref name="IPCC AR6 WGI Glossary" />{{rp|2220}} These ecosystems can play an important role for climate change mitigation and [[ecosystem-based adaptation]]. However, when blue carbon ecosystems are degraded or lost, they release carbon back to the atmosphere, thereby adding to [[greenhouse gas emissions]].<ref name="IPCC AR6 WGI Glossary" />{{rp|2220}}
+The methods for ''blue carbon management'' fall into the category of "ocean-based biological [[carbon dioxide removal]] (CDR) methods".<ref name=":2">Canadell, J. G., P. M. S. Monteiro, M. H. Costa, L. Cotrim da Cunha, P. M. Cox, A. V. Eliseev, S. Henson, M. Ishii, S. Jaccard, C. Koven, A. Lohila, P. K. Patra, S. Piao, J. Rogelj, S. Syampungani, S. Zaehle, and K. Zickfeld, 2021: [https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-5/ Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks]. In ''[https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change]'' [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 673–816, {{doi|10.1017/9781009157896.007}}.</ref>{{rp|764}} They are a type of [[biological carbon fixation]].
-== Relevance of blue carbon ==
+Scientists are looking for ways to further develop the ''blue carbon potential'' of ecosystems.<ref name="Ricart2022">{{cite journal |last1=Ricart |first1=Aurora M. |last2=Krause-Jensen |first2=Dorte |last3=Hancke |first3=Kasper |last4=Price |first4=Nichole N. |last5=Masqué |first5=Pere |last6=Duarte |first6=Carlos M. |title=Sinking seaweed in the deep ocean for carbon neutrality is ahead of science and beyond the ethics |journal=Environmental Research Letters |date=2022 |volume=17 |issue=8 |page=081003 |doi=10.1088/1748-9326/ac82ff|bibcode=2022ERL....17h1003R |s2cid=250973225 |doi-access=free |hdl=10754/679874 |hdl-access=free }}</ref> However, the long-term effectiveness of blue carbon as a carbon dioxide removal solution is under debate.<ref>{{cite journal |last1=Hurd |first1=Catriona L. |last2=Law |first2=Cliff S. |last3=Bach |first3=Lennart T. |last4=Britton |first4=Damon |last5=Hovenden |first5=Mark |last6=Paine |first6=Ellie R. |last7=Raven |first7=John A. |last8=Tamsitt |first8=Veronica |last9=Boyd |first9=Philip W. |title=Forensic carbon accounting: Assessing the role of seaweeds for carbon sequestration |journal=Journal of Phycology |date=2022 |volume=58 |issue=3 |pages=347–363 |doi=10.1111/jpy.13249|pmid=35286717 |s2cid=247453370 |doi-access=free |bibcode=2022JPcgy..58..347H }}</ref><ref name="Ricart2022" /><ref name="Boyd2022">{{cite journal |last1=Boyd |first1=Philip W. |last2=Bach |first2=Lennart T. |last3=Hurd |first3=Catriona L. |last4=Paine |first4=Ellie |last5=Raven |first5=John A. |last6=Tamsitt |first6=Veronica |title=Potential negative effects of ocean afforestation on offshore ecosystems |journal=Nature Ecology & Evolution |date=2022 |volume=6 |issue=6 |pages=675–683 |doi=10.1038/s41559-022-01722-1 |pmid=35449458 |bibcode=2022NatEE...6..675B |s2cid=248322820 }}</ref>
-The rates of blue [[carbon sequestration]] and storage capacities in ecosystems are comparable to (and often higher than) those in carbon-rich terrestrial ecosystems such as [[tropical rainforest]]s or [[peatland]]s. Unlike most terrestrial systems, which reach soil carbon [[chemical equilibrium|equilibrium]] within decades, deposition of carbon dioxide in coastal ecosystem sediment can continue over millennia. However, when these coastal ecosystems are degraded or destroyed they can become carbon dioxide sources due to the oxidization of biomass and organic soil.<ref>Laffoley, Dan and Grimsditch, Gabriel (2009): The Management of Natural Coastal Carbon Sinks. Gland, Switzerland: IUCN</ref>
+The term ''deep blue carbon'' is also in use and refers to storing carbon in the deep ocean waters.<ref>{{Cite web |date=2022-11-04 |title=What Is Blue Carbon? |url=https://carbonbetter.com/story/blue-carbon/ |access-date=2023-05-20 |website=CarbonBetter |language=en}}</ref>
-Because coastal ecosystems do contain substantial amounts of carbon, and because this carbon is in danger of being released, they are important in [[mitigation of climate change|mitigating climate change]]. However, the rate of loss of mangroves, seagrasses and salt marshes (driven mostly by human activities) is estimated to be among the highest of any ecosystem on the planet, prompting international interest in managing them more effectively for their carbon benefits.<ref>Murray et al. (2010): Payments for Blue Carbon. Potential for Protecting Threatened Coastal Habitats. Durham, USA: Nicholas Institute for Environmental Policy Solutions</ref>
+== Definition ==
-These ecosystems are highly valuable not only for their contribution to climate change mitigation on a global scale, but also for the many valuable services they provide locally.<ref>Crooks, Stephen et al. (2011): Mitigating Climate Change through Restoration and Management of Coastal Wetlands and Near-shore Marine Ecosystems: Challenges and Opportunities. Washington D.C., USA: World Bank</ref>
+''Blue carbon'' is defined by the [[Intergovernmental Panel on Climate Change|IPCC]] as "Biologically driven carbon fluxes and storage in marine systems that are amenable to management."<ref name="IPCC AR6 WGI Glossary">IPCC, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_AnnexVII.pdf Annex VII: Glossary] [Matthews, J. B. R., V. Möller, R. van Diemen, J. S. Fuglestvedt, V. Masson-Delmotte, C.  Méndez, S. Semenov, A. Reisinger (eds.)]. In [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J. B. R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, pp. 2215–2256, {{doi|10.1017/9781009157896.022}}.</ref>{{rp|2220}}
+Another definition states: "Blue carbon refers to organic carbon that is captured and stored by the oceans and [[coastal ecosystems]], particularly by vegetated coastal ecosystems: [[Seagrass meadow|seagrass meadows]], [[Tidal marsh|tidal marshes]], and [[Mangrove forest|mangrove forests]]."<ref name=":5">{{Cite journal |last1=Macreadie |first1=Peter I. |last2=Anton |first2=Andrea |last3=Raven |first3=John A. |last4=Beaumont |first4=Nicola |last5=Connolly |first5=Rod M. |last6=Friess |first6=Daniel A. |last7=Kelleway |first7=Jeffrey J. |last8=Kennedy |first8=Hilary |last9=Kuwae |first9=Tomohiro |last10=Lavery |first10=Paul S. |last11=Lovelock |first11=Catherine E. |last12=Smale |first12=Dan A. |last13=Apostolaki |first13=Eugenia T. |last14=Atwood |first14=Trisha B. |last15=Baldock |first15=Jeff |date=2019 |title=The future of Blue Carbon science |journal=Nature Communications |language=en |volume=10 |issue=1 |pages=3998 |doi=10.1038/s41467-019-11693-w |issn=2041-1723 |pmc=6728345 |pmid=31488846 |bibcode=2019NatCo..10.3998M |doi-access=free}} [[File:CC-BY icon.svg|50px]] Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].</ref>
-== See also ==
-* [[Carbon sequestration]]
-* [[Carbonic acid]]
-* [[Climate change]]
-* [[Ecosystem services]]
-* [[Fisheries and climate change]]
-* [[Kelp]]
-* [[Mangroves]]
-* [[Marine ecosystem]]
-* [[Seagrass]]
-* [[Seawater]]
-* [[Salt marsh]]
+''Coastal blue carbon'' focuses on "rooted vegetation in the coastal zone, such as [[tidal marsh]]es, [[mangrove]]s and [[seagrass]]es". Seagrass, salt marshes and mangroves are sometimes referred to as "blue forests" in contrast to land-based "green forests".<ref name="UNEP">{{cite web |date=13 Apr 2017 |title=Blue Forests: Finding Coastal and Marine Solutions to meet the Paris Agreement |url=https://www.unep.org/news-and-stories/story/blue-forests-finding-coastal-and-marine-solutions-meet-paris-agreement |url-status=live |archive-url=https://web.archive.org/web/20210817031528/https://www.unep.org/news-and-stories/story/blue-forests-finding-coastal-and-marine-solutions-meet-paris-agreement |archive-date=17 August 2021 |access-date=17 August 2021 |website=UN Environment Program}}</ref><ref>{{cite news |last1=Twilley |first1=Robert |last2=Rovai |first2=Andre |date=January 15, 2019 |title=Why protecting 'blue carbon' storage is crucial to fighting climate change |work=GreenBiz |url=https://www.greenbiz.com/article/why-protecting-blue-carbon-storage-crucial-fighting-climate-change |url-status=live |access-date=17 August 2021 |archive-url=https://web.archive.org/web/20210817142111/https://www.greenbiz.com/article/why-protecting-blue-carbon-storage-crucial-fighting-climate-change |archive-date=17 August 2021}}</ref>
-== References ==
+''Deep blue carbon'' is located in the [[International waters|high seas]] beyond national jurisdictions.<ref name=":3">{{Cite web |title=Deep Blue Carbon |url=https://www.ofi.ca/impact/policy/deep-blue-carbon |access-date=2023-05-09 |url-status=dead |archive-url=https://web.archive.org/web/20240118065649/https://www.ofi.ca/programs/north-atlantic-carbon-observatory/deep-blue-carbon |archive-date=2024-01-18 |website=Ocean Frontier Institute}}</ref> It includes carbon contained in "[[continental shelf]] waters, [[Deep sea|deep-sea]] waters and the sea floor beneath them" and makes up 90% of all ocean carbon.<ref>{{Cite web |title=Advancing responsible deep blue carbon: a business strategist perspective |url=https://impact.economist.com/ocean/ocean-and-climate/advancing-responsible-deep-blue-carbon-a-business-strategist-perspective |access-date=2023-05-09 |website=impact.economist.com |language=en-gb}}</ref> Deep blue carbon is generally seen as "less amenable to management" and challenging due to lack of data "relating to the permanence of their carbon stores".<ref name=":2" />{{rp|764}}
-{{reflist}}
+== Role in climate change context ==
+The term ''blue carbon'' was coined in 2009.<ref>{{cite journal |last1=Cathrine E. |first1=Lovelock |last2=Duarte |first2=Carlos M. |date=2019 |title=Dimensions of Blue Carbon and emerging perspectives |journal=Biology Letters |volume=15 |issue=3 |page=20180781 |doi=10.1098/rsbl.2018.0781 |pmc=6451379 |pmid=30836882}}</ref><ref name=":5" /> At the time, the term was coined to highlight that coastal vegetated ecosystems have a disproportionately large contribution to global [[carbon sequestration]].<ref name=":5" /> Others use the term to describe the carbon captured by the entire ocean, not just the coastal ecosystems.<ref>{{Cite web |title=What is Blue Carbon? |url=https://oceanservice.noaa.gov/facts/bluecarbon.html}}</ref> The role of blue carbon in [[climate change mitigation]] and [[Climate change adaptation|adaptation]] has now reached international prominence.<ref name=":5" />
+The [[vegetated coastal ecosystem]]s of tidal marshes, mangroves and seagrasses (which are grouped as "blue carbon") have high [[carbon burial]] rates. This is because they accumulate carbon in their soils and [[sediment]]s.<ref name="IPCC AR6 WGI Glossary" />{{rp|2220}}
+Such ecosystems can contribute to [[climate change mitigation]] and also to [[ecosystem-based adaptation]]. However, when coastal blue carbon ecosystems are degraded or lost they release carbon back to the atmosphere.<ref name="IPCC AR6 WGI Glossary" />{{rp|2220}}
+Mangroves, salt marshes and seagrasses can store carbon and are highly efficient [[carbon sink]]s. They capture {{CO2}} from the atmosphere by [[Carbon sequestration|sequestering the carbon]] in their underlying sediments, in underground and below-ground biomass, and in dead biomass.<ref>{{Cite book|last=National Academies of Sciences, Engineering, and Medicine|url=https://www.nap.edu/catalog/25259|title=Negative Emissions Technologies and Reliable Sequestration: A Research Agenda|year=2019|isbn=978-0-309-48452-7|pages=45–48|language=en|chapter=Coastal Blue Carbon|doi=10.17226/25259|pmid=31120708|s2cid=134196575|access-date=2020-02-21|archive-date=2021-11-22|archive-url=https://web.archive.org/web/20211122220527/https://www.nap.edu/catalog/25259/negative-emissions-technologies-and-reliable-sequestration-a-research-agenda|url-status=live}}</ref>
+Although [[vegetated coastal ecosystems]] cover less area and have less aboveground biomass than [[terrestrial plant]]s they have the potential to impact long term C sequestration, particularly in sediment sinks.<ref name="Nelleman2016">{{Cite web|last=Nelleman| first=C.| title=Blue carbon: the role of healthy oceans in binding carbon.|url=http://www.grida.no/files/publications/blue-carbon/BlueCarbon_screen.pdf|url-status=dead|archive-url=https://web.archive.org/web/20160304204843/http://www.grida.no/files/publications/blue-carbon/BlueCarbon_screen.pdf|archive-date=2016-03-04}}</ref>
+One of the main concerns with blue carbon is that the rate of loss of these important marine ecosystems is much higher than any other ecosystem on the planet, even compared to [[rainforest]]s. Current estimates suggest a loss of 2-7% per year, which is not only lost carbon sequestration, but also lost habitat that is important for managing climate, coastal protection, and health.<ref name="Nelleman2016" />
+[[File:Economic value of blue carbon ecosystems per hectare.webp|thumb|upright=1.35| Estimates of the economic value of blue carbon ecosystems per hectare. Based on 2009 data from UNEP/GRID-Arendal.<ref name="Nellemann2009">Nellemann, Christian et al. (2009): Blue Carbon. The Role of Healthy Oceans in Binding Carbon. A Rapid Response Assessment. Arendal, Norway: UNEP/GRID-Arendal</ref><ref name="Macreadie2019">Macreadie, P.I., Anton, A., Raven, J.A., Beaumont, N., Connolly, R.M., Friess, D.A., Kelleway, J.J., Kennedy, H., Kuwae, T., Lavery, P.S. and Lovelock, C.E. (2019) "The future of Blue Carbon science". ''Nature communications'', '''10'''(1): 1–13. {{doi|10.1038/s41467-019-11693-w}}.</ref>]]As habitats that sequester carbon are altered and decreased, that stored amount of C is being released into the atmosphere, continuing the current accelerated rate of [[climate change]]. Impacts on these habitats globally will directly and indirectly release the previously stored carbon, which had been sequestered in the sediments of these habitats. Declines in vegetated coastal habitats are seen worldwide.
+Quantifying rates of decrease are difficult to calculate, however measurements have been estimated by researchers indicating that if blue carbon ecosystems continue to decline, for any number of reasons, 30-40% of tidal marshes and seagrasses and approximately 100% of mangroves could be gone in the next century.<ref name=Pendleton2012>{{Cite journal| last1 = Pendleton| first1 = Linwood| last2 = Donato| first2 = Daniel C.| last3 = Murray| first3 = Brian C.| last4 = Crooks| first4 = Stephen| last5 = Jenkins| first5 = W. Aaron| last6 = Sifleet| first6 = Samantha| last7 = Craft| first7 = Christopher| last8 = Fourqurean| first8 = James W.| last9 = Kauffman| first9 = J. Boone| title = Estimating Global "Blue Carbon" Emissions from Conversion and Degradation of Vegetated Coastal Ecosystems| journal = PLOS ONE| volume = 7| issue = 9| doi = 10.1371/journal.pone.0043542| pmc = 3433453| pmid = 22962585| pages=e43542| year=2012| bibcode = 2012PLoSO...743542P| doi-access = free}}</ref>
+Reasons for the decline of mangroves, seagrass, and marshes include land use changes, climate and drought related effects, dams built in the watershed, convergence to aquaculture and agriculture, land development and sea-level rise due to climate change. Increases in these activities can lead to significant decreases in habitat availability and thus increases in released C from sediments.
+As anthropogenic effects and climate change are heightened, the effectiveness of blue carbon sinks will diminish and CO<sub>2</sub> emissions will be further increased. Data on the rates at which CO<sub>2</sub> is being released into the atmosphere is not robust currently; however, research is being conducted to gather better information to analyze trends. Loss of underground biomass (roots and rhizomes) will allow for CO<sub>2</sub> to be emitted changing these habitats into sources rather than carbon sinks.<ref name="Macreadie2013">{{Cite journal |last1=Macreadie |first1=Peter I. |last2=Hughes |first2=A. Randall |last3=Kimbro |first3=David L. |year=2013 |title=Loss of 'Blue Carbon' from Coastal Salt Marshes Following Habitat Disturbance |journal=PLOS ONE |volume=8 |issue=7 |pages=e69244 |bibcode=2013PLoSO...869244M |doi=10.1371/journal.pone.0069244 |pmc=3704532 |pmid=23861964 |doi-access=free}}</ref>
+===Impacts of nutrient load===
+Increases in [[Carbon capture and storage|carbon capture]] and sequestration have been observed in both mangrove and seagrass ecosystems which have been subjected to high nutrient loads, either intentionally or due to waste from human activities.<ref name="Kumar, K. 2014">{{cite journal |last1=Kumar |first1=K. |last2=Banerjee |first2=D. |last3=Das |first3=D. |year=2014 |title=Carbon dioxide sequestration from industrial flue gas by Chlorella sorokiniana |journal=Bioresource Technology |volume=152 |pages=225–233 |doi=10.1016/j.biortech.2013.10.098 |pmid=24292202|bibcode=2014BiTec.152..225K }}</ref>
+Research done on mangrove soils from the [[Red Sea]] have shown that increases in nutrient loads to these soils do not increase carbon [[Mineralization (soil science)|mineralization]] and subsequent CO<sub role="presentation">2</sub> release.<ref>{{cite journal |last1=Keuskamp |first1=J. A. |last2=Schmitt |first2=H. |last3=Laanbroek |first3=H. J. |last4=Verhoeven |first4=J. T. |last5=Hefting |first5=M. M. |year=2013 |title=Nutrient amendment does not increase mineralisation of sequestered carbon during incubation of a nitrogen limited mangrove soil |url=https://pure.knaw.nl/portal/en/publications/nutrient-amendment-does-not-increase-mineralisation-of-sequestered-carbon-during-incubation-of-a-nitrogenlimited-mangrove-soil(d8918399-488b-4f7e-8289-177bd6bffe5c).html |url-status=live |journal=Soil Biology and Biochemistry |volume=57 |pages=822–829 |doi=10.1016/j.soilbio.2012.08.007 |bibcode=2013SBiBi..57..822K |archive-url=https://web.archive.org/web/20211122220552/https://pure.knaw.nl/portal/en/publications/nutrient-amendment-does-not-increase-mineralisation-of-sequestere |archive-date=2021-11-22 |access-date=2020-05-11 |hdl-access=free |hdl=20.500.11755/d8918399-488b-4f7e-8289-177bd6bffe5c}}</ref> This neutral effect of fertilization was not found to be true in all mangrove forest types. Carbon capture rates also increased in these forests due to increased growth rates of the mangroves. In forests with increases in [[Respiration in plant|respiration]] there were also increases in mangrove growth of up to six times the normal rate.<ref name="Mcleod2011">{{cite journal |last1=Mcleod |first1=E. |last2=Chmura |first2=G. L. |last3=Bouillon |first3=S. |last4=Salm |first4=R. |last5=Björk |first5=M. |last6=Duarte |first6=C. M. |last7=Silliman |first7=B. R. |year=2011 |title=A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering {{CO2}} |url=https://espace.library.uq.edu.au/view/UQ:251863/UQ251863_OA.pdf |url-status=live |journal=Frontiers in Ecology and the Environment |volume=9 |issue=10 |pages=552–560 |doi=10.1890/110004 |archive-url=https://web.archive.org/web/20161220195926/http://espace.library.uq.edu.au/view/UQ:251863/UQ251863_OA.pdf |archive-date=2016-12-20 |access-date=2019-09-30 |doi-access=free|bibcode=2011FrEE....9..552M }}</ref>
+== Carbon storage by type of biome ==
+=== Tidal marshes ===
+{{Further|Tidal marsh}}
+[[File:HHI Tide.jpg|thumb|[[Tidal marsh]]]]
+[[Tidal marsh|Tidal marshes]] can be found globally on coastlines from the arctic to the subtropics. They are [[Intertidal zone|intertidal]] ecosystems dominated by [[Herbaceous plant|herbaceous]] vegetation. In the tropics, marshes are replaced by mangroves as the dominant coastal vegetation.<ref name="Chmura2003">{{Cite journal |last1=Chmura |first1=Gail |last2=Anisfield |first2=Shimon |date=2003 |title=Global carbon sequestration in tidal, saline wetland soils |journal=Global Biogeochemical Cycles |volume=17 |issue=4 |pages=n/a |bibcode=2003GBioC..17.1111C |doi=10.1029/2002GB001917 |doi-access=free}}</ref>
+Marshes have high productivity, with a large portion of primary production in belowground biomass.<ref name="Chmura2003" /> This belowground biomass can form deposits up to 8m deep.<ref name="Chmura2003" /> Marshes provide valuable habitat for plants, birds, and juvenile fish, protect coastal habitat from [[storm surge]] and flooding, and can reduce [[Eutrophication|nutrient loading]] to coastal waters.<ref>{{Cite journal |last=Chmura |first=Gail L |date=2013 |title=What do we need to assess the sustainability of the tidal salt marsh carbon sink? |journal=Ocean and Coastal Management |volume=83 |pages=25–31 |doi=10.1016/j.ocecoaman.2011.09.006|bibcode=2013OCM....83...25C }}</ref> Similarly to mangrove and seagrass habitats, marshes also serve as important [[carbon sink]]s.<ref name="Mudd2009">{{Cite journal |last=Mudd |first=Simon, M. |date=2009 |title=Impact of dynamic feedbacks between sedimentation, sea-level rise, and biomass production on near-surface marsh stratigraphy and carbon accumulation |journal=Estuarine, Coastal and Shelf Science |volume=82 |issue=3 |pages=377–389 |bibcode=2009ECSS...82..377M |doi=10.1016/j.ecss.2009.01.028}}</ref> Marshes sequester C in underground biomass due to high rates of organic sedimentation and [[Anaerobic decomposition|anaerobic]]-dominated decomposition.<ref name="Mudd2009" /> Salt marshes cover approximately 22,000 to 400,000&nbsp;km<sup>2</sup> globally, with an estimated carbon burial rate of 210&nbsp;g C m<sup>−2</sup> yr<sup>−1</sup>.<ref name="Chmura2003" />
+Salt marshes may not be expansive worldwide in relation to forests, but they have a C burial rate that is over 50 times faster than tropical rainforests. Rates of burial have been estimated at up to 87.2&nbsp;± 9.6&nbsp;Tg C yr<sup>−1</sup> which is greater than that of tropical rainforests, 53&nbsp;± 9.6&nbsp;Tg C yr<sup>−1</sup>.<ref name="Macreadie2013" /> Since the 1800s salt marshes have been disturbed due to development and a lack of understanding of their importance. The 25% decline since that time has led to a decrease in potential C sink area coupled with the release of once buried C. Consequences of increasingly degraded marsh habitat are a decrease in C stock in sediments, a decrease in plant biomass and thus a decrease in photosynthesis reducing the amount of CO<sub>2</sub> taken up by the plants, failure of C in plant blades to be transferred into the sediment, possible acceleration of erosive processes due to the lack of plant biomass, and acceleration of buried C release to the atmosphere.<ref name="Macreadie2013" />
+Tidal marshes have been impacted by humans for centuries, including modification for grazing, haymaking, reclamation for agriculture, development and ports, evaporation ponds for salt production, modification for [[aquaculture]], insect control, tidal power and flood protection.<ref name=":05">{{Cite journal |last=Adam |first=Paul |date=2002 |title=Saltmarshes in a time of change |journal=Environmental Conservation |volume=29 |issue=1 |pages=39–61 |doi=10.1017/S0376892902000048 |bibcode=2002EnvCo..29...39A |s2cid=83610071}}</ref> Marshes are also susceptible to pollution from oil, industrial chemicals, and most commonly, [[eutrophication]]. Introduced species, sea-level rise, river damming and decreased sedimentation are additional longterm changes that affect marsh habitat, and in turn, may affect carbon sequestration potential.<ref name="Fourqurean2002">{{cite journal |last1=Fourqurean |first1=James W. |last2=Zieman |first2=Joseph C. |year=2002 |title=Nutrient Content of the Seagrass Thalassia Testudinum Reveals Regional Patterns of Relative Availability of Nitrogen and Phosphorus in the Florida Keys USA |journal=Biogeochemistry |volume=61 |issue=3 |pages=229–45 |doi=10.1023/A:1020293503405 |s2cid=4948302}}</ref>
+=== Mangroves ===
+{{Further|Mangrove restoration}}
+[[File:Mangrove trees in Everglades.JPG|thumb|[[Mangrove forest]]]]
+Globally, mangroves stored 4.19 ± 0.62&nbsp;Pg (CI 95%) of carbon in 2012, with Indonesia, Brazil, Malaysia and Papua New Guinea accounting for more than 50% of the global stock.<ref name=":1">{{Cite journal|last1=Hamilton|first1=Stuart E.|last2=Friess|first2=Daniel A.|date=2018-02-26|title=Global carbon stocks and potential emissions due to mangrove deforestation from 2000 to 2012|journal=Nature Climate Change|volume=8|issue=3|pages=240–244|doi=10.1038/s41558-018-0090-4|issn=1758-678X|arxiv=1611.00307|bibcode=2018NatCC...8..240H|s2cid=89785740}}</ref> 2.96&nbsp;± 0.53&nbsp;Pg of the global carbon stock is contained within the soil and 1.23&nbsp;± 0.06&nbsp;Pg in the living biomass.<ref name=":1" /> Of this 1.23 Pg, approximately 0.41 ± 0.02 Pg is in the belowground biomass in the root system and approximately 0.82&nbsp;± 0.04&nbsp;Pg is in the aboveground living biomass.<ref name=":1" />
+Global mangrove canopy cover is estimated as between 83,495&nbsp;km<sup>2</sup> and 167,387&nbsp;km<sup>2</sup> in 2012 with Indonesia containing approximately 30% of the entire global mangrove forest area.<ref>{{Cite journal|last1=Hamilton|first1=Stuart E.|last2=Casey|first2=Daniel|date=2016-03-21|title=Creation of a high spatio-temporal resolution global database of continuous mangrove forest cover for the 21st century (CGMFC-21)|journal=Global Ecology and Biogeography|language=en|volume=25|issue=6|pages=729–738|doi=10.1111/geb.12449|issn=1466-822X|arxiv=1412.0722|bibcode=2016GloEB..25..729H |s2cid=55999275}}</ref> Mangrove forests are responsible for approximately 10% of global carbon burial,<ref>{{Cite journal
+| last = Duarte
+| first = C.M.
+| date = 2005
+| title = Major rule of marine vegetation on the oceanic carbon cycle
+| url = https://hal.inria.fr/file/index/docid/297509/filename/bg-2-1-2005.pdf
+| journal = Biogeosciences
+| doi = 10.5194/bg-2-1-2005
+| volume = 2
+| issue = 1
+| pages = 1–8
+| bibcode = 2005BGeo....2....1D
+| doi-access = free
+| access-date = 2016-03-02
+| archive-date = 2016-03-05
+| archive-url = https://web.archive.org/web/20160305183736/https://hal.inria.fr/file/index/docid/297509/filename/bg-2-1-2005.pdf
+| url-status = live
+}}</ref> with an estimated carbon burial rate of 174 g C m<sup>−2</sup> yr<sup>−1</sup>.<ref name="Alongi2002">{{Cite journal |last=Alongi |first=DM |date=2002 |title=Present state and future of the world's mangrove forests |url=http://faculty.washington.edu/timbillo/Readings%20and%20documents/CO2%20and%20Forests%20readings/mangroves%20CO2.pdf |url-status=live |journal=Environmental Conservation |volume=29 |issue=3 |pages=331–349 |doi=10.1017/S0376892902000231 |bibcode=2002EnvCo..29..331A |archive-url=https://web.archive.org/web/20160306191808/http://faculty.washington.edu/timbillo/Readings%20and%20documents/CO2%20and%20Forests%20readings/mangroves%20CO2.pdf |archive-date=2016-03-06 |access-date=2016-03-02 |s2cid=1886523}}</ref>
+Mangroves, like seagrasses, have potential for high levels of carbon sequestration. They account for 3% of the global carbon sequestration by tropical forests and 14% of the global coastal ocean's carbon burial.<ref name="Alongi2012">{{Cite journal |last=Alongi |first=Daniel M |date=2012 |title=Carbon sequestration in mangrove forests |url=https://www.researchgate.net/publication/274116107 |url-status=live |journal=Future Science |archive-url=https://web.archive.org/web/20211122220532/https://www.researchgate.net/publication/274116107_Carbon_sequestration_in_mangrove_forests |archive-date=2021-11-22 |access-date=2019-07-26}}</ref>
+Mangroves are naturally disturbed by floods, [[tsunami]]s, coastal storms like [[cyclone]]s and [[hurricanes]], lightning, disease and pests, and changes in water quality or temperature.<ref name="Alongi2002" /> Although they are resilient to many of these natural disturbances, they are highly susceptible to human impacts including urban development, [[aquaculture]], [[mining]], and [[overexploitation]] of shellfish, crustaceans, fish and timber.<ref name="Spaulding2010">{{Cite web|url=https://www.cbd.int/cooperation/pavilion/nagoya-presentations/2010-10-21-session1-mangroves-en.pdf|title=World atlas of mangroves|last=Spaulding|first=MD|date=2010|access-date=2016-03-02|archive-date=2016-03-07|archive-url=https://web.archive.org/web/20160307152357/https://www.cbd.int/cooperation/pavilion/nagoya-presentations/2010-10-21-session1-mangroves-en.pdf|url-status=live}}</ref><ref name="Alongi2002" /> Mangroves provide globally important ecosystem services and carbon sequestration and are thus an important habitat to conserve and repair when possible.<ref name="Zimmer">{{cite journal |last1=Zimmer |first1=Katarina |title=Many mangrove restorations fail. Is there a better way? |journal=Knowable Magazine |date=22 July 2021 |doi=10.1146/knowable-072221-1 |url=https://knowablemagazine.org/article/food-environment/2021/many-mangrove-restorations-fail |access-date=11 August 2021 |doi-access=free |archive-date=16 August 2021 |archive-url=https://web.archive.org/web/20210816114657/https://knowablemagazine.org/article/food-environment/2021/many-mangrove-restorations-fail |url-status=live }}</ref><ref name="Friess">{{cite journal |last1=Friess |first1=Daniel A. |last2=Rogers |first2=Kerrylee |last3=Lovelock |first3=Catherine E. |last4=Krauss |first4=Ken W. |last5=Hamilton |first5=Stuart E. |last6=Lee |first6=Shing Yip |last7=Lucas |first7=Richard |last8=Primavera |first8=Jurgenne |last9=Rajkaran |first9=Anusha |last10=Shi |first10=Suhua |date=17 October 2019 |title=The State of the World's Mangrove Forests: Past, Present, and Future |journal=Annual Review of Environment and Resources |volume=44 |issue=1 |pages=89–115 |doi=10.1146/annurev-environ-101718-033302 |doi-access=free}}</ref>
+Dams threaten habitats by slowing the amount of freshwater reaching mangroves. Coral reef destruction also plays a role in mangrove habitat health as reefs slow wave energy to a level that mangroves are more tolerant of.
+=== Seagrass meadows ===
+{{Main|Seagrass meadow}}
+[[File:Seagrass at Rapid Bay Jetty P1262907.JPG|thumb|[[Seagrass meadow]]]]
+[[File:Results_of_trawling.png|right|thumb|(A) untrawled seamount and (B) a trawled seamount. [[Bottom trawling]] has destroyed many coastal habitats.]]
+Although [[seagrass]] makes up only 0.1% of the area of the ocean floor, it accounts for approximately 10–18% of the total oceanic carbon burial.<ref name="Fourqurean2012">{{Cite journal |last=Fourqurean |first=James W. |date=2012 |title=Seagrass ecosystems as a globally significant carbon stock |journal=Nature Geoscience |volume=5 |issue=7 |pages=505–509 |bibcode=2012NatGe...5..505F |doi=10.1038/ngeo1477}}</ref> Currently global [[Seagrass meadow|seagrass meadows]] are estimated to store as much as 19.9&nbsp;Pg (gigaton, or billion tons) of organic carbon.<ref name="Fourqurean2012" /> There has been considerable attention to how large-scale seaweed cultivation in the open ocean can act as a form of carbon sequestration.<ref name=":0">{{Cite journal |last1=Duarte |first1=Carlos M. |last2=Wu |first2=Jiaping |last3=Xiao |first3=Xi |last4=Bruhn |first4=Annette |last5=Krause-Jensen |first5=Dorte |date=2017 |title=Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation? |journal=Frontiers in Marine Science |volume=4 |pages=100 |doi=10.3389/fmars.2017.00100 |issn=2296-7745 |doi-access=free|hdl=10754/623247 |hdl-access=free }}</ref><ref>{{Cite web |last=Temple |first=James |date=2021-09-19 |title=Companies hoping to grow carbon-sucking kelp may be rushing ahead of the science |url=https://www.technologyreview.com/2021/09/19/1035889/kelp-carbon-removal-seaweed-sinking-climate-change/ |url-status=live |archive-url=https://web.archive.org/web/20210919212025/https://www.technologyreview.com/2021/09/19/1035889/kelp-carbon-removal-seaweed-sinking-climate-change/ |archive-date=2021-09-19 |access-date=2021-11-25 |website=MIT Technology Review |language=en}}</ref> Studies have demonstrated that nearshore seaweed forests constitute a source of blue carbon, as seaweed detritus is carried by wave currents into the middle and deep ocean thereby sequestering carbon.<ref name=":0" /><ref>{{Cite journal |last1=Wernberg |first1=Thomas |last2=Filbee-Dexter |first2=Karen |date=2018-11-21 |title=Grazers extend blue carbon transfer by slowing sinking speeds of kelp detritus |journal=Scientific Reports |volume=8 |issue=1 |pages=17180 |bibcode=2018NatSR...817180W |doi=10.1038/s41598-018-34721-z |issn=2045-2322 |pmc=6249265 |pmid=30464260}}</ref><ref>{{Cite journal |last1=Berg |first1=Peter |last2=Delgard |first2=Marie Lise |last3=Polsenaere |first3=Pierre |last4=McGlathery |first4=Karen J. |last5=Doney |first5=Scott C. |last6=Berger |first6=Amelie C. |date=2019-06-24 |title=Dynamics of benthic metabolism, O 2 , and pCO 2 in a temperate seagrass meadow |journal=Limnology and Oceanography |language=en |volume=64 |issue=6 |pages=2586–2604 |doi=10.1002/lno.11236 |bibcode=2019LimOc..64.2586B |s2cid=198383189 |issn=0024-3590|doi-access=free }}</ref><ref>{{Cite journal |last1=Pessarrodona |first1=Albert |last2=Franco-Santos |first2=Rita M. |last3=Wright |first3=Luka Seamus |last4=Vanderklift |first4=Mathew A. |last5=Howard |first5=Jennifer |last6=Pidgeon |first6=Emily |last7=Wernberg |first7=Thomas |last8=Filbee-Dexter |first8=Karen |date=December 2023 |title=Carbon sequestration and climate change mitigation using macroalgae: a state of knowledge review |url=https://onlinelibrary.wiley.com/doi/10.1111/brv.12990 |journal=Biological Reviews |language=en |volume=98 |issue=6 |pages=1945–1971 |doi=10.1111/brv.12990 |pmid=37437379 |issn=1464-7931|hdl=11250/3102733 |hdl-access=free }}</ref><ref>{{Cite journal |last=Filbee-Dexter |first=Karen |last2=Pessarrodona |first2=Albert |last3=Pedersen |first3=Morten F. |last4=Wernberg |first4=Thomas |last5=Duarte |first5=Carlos M. |last6=Assis |first6=Jorge |last7=Bekkby |first7=Trine |last8=Burrows |first8=Michael T. |last9=Carlson |first9=Daniel F. |last10=Gattuso |first10=Jean-Pierre |last11=Gundersen |first11=Hege |last12=Hancke |first12=Kasper |last13=Krumhansl |first13=Kira A. |last14=Kuwae |first14=Tomohiro |last15=Middelburg |first15=Jack J. |date=2024-05-22 |title=Carbon export from seaweed forests to deep ocean sinks |url=https://www.nature.com/articles/s41561-024-01449-7 |journal=Nature Geoscience |language=en |volume=17 |issue=6 |pages=552–559 |doi=10.1038/s41561-024-01449-7 |issn=1752-0908}}</ref>
+Carbon primarily accumulates in [[Pelagic sediment|marine sediments]], which are [[Anoxic waters|anoxic]] and thus continually preserve organic carbon from decadal-millennial time scales. High accumulation rates, low oxygen, low sediment [[Electrical resistivity and conductivity|conductivity]] and slower microbial [[decomposition]] rates all encourage carbon burial and carbon accumulation in these coastal sediments.<ref name="Duarte2011">{{Cite journal |last=Duarte |first=CM |date=2011 |title=Assessing the capacity of seagrass meadows for carbon burial: current limitations and future strategies. |journal=Ocean Coastal Management}}</ref>
+Compared to terrestrial habitats that lose carbon stocks as CO<sub>2</sub> during decomposition or by disturbances like fires or deforestation, marine carbon sinks can retain C for much longer time periods. Carbon sequestration rates in seagrass meadows vary depending on the species, characteristics of the sediment, and depth of the habitats, but on average the carbon burial rate is approximately 138&nbsp;g C m<sup>−2</sup> yr<sup>−1</sup>.<ref name="McLeod">{{Cite web |last=McLeod |first=E. |title=A blueprint for blue carbon: toward an improved understanding of the role of vegetated coastal habitats in sequestering {{CO2}} |url=http://espace.library.uq.edu.au/view/UQ:251863/UQ251863_OA.pdf |url-status=live |archive-url=https://web.archive.org/web/20160308095312/http://espace.library.uq.edu.au/view/UQ:251863/UQ251863_OA.pdf |archive-date=2016-03-08 |access-date=2016-03-02}}</ref>
+Seagrass habitats are threatened by coastal [[eutrophication]], increased seawater temperatures,<ref name="Duarte2011" /> increased sedimentation and coastal development,<ref name="McLeod" /> and [[sea level rise]] which may decrease light availability for [[photosynthesis]]. Seagrass loss has accelerated over the past few decades, from 0.9% per year prior to 1940 to 7% per year in 1990, with about 1/3 of global loss since WWII.<ref>{{Cite journal |last=Waycott |first=M |date=2009 |title=Accelerating loss of seagrasses across the globe threatens coastal ecosystems |journal=Proceedings of the National Academy of Sciences of the USA |volume=106 |issue=30 |pages=12377–12381 |bibcode=2009PNAS..10612377W |doi=10.1073/pnas.0905620106 |pmc=2707273 |pmid=19587236 |doi-access=free}}</ref> The decline in seagrasses is due to a number of factors including drought, water quality issues, agricultural practices, invasive species, pathogens, fishing and climate change.<ref>{{Cite journal |last1=Orth |first1=Robert J. |last2=Carruthers |first2=Tim J. B. |last3=Dennison |first3=William C. |last4=Duarte |first4=Carlos M. |last5=Fourqurean |first5=James W. |last6=Heck |first6=Kenneth L. |last7=Hughes |first7=A. Randall |last8=Kendrick |first8=Gary A. |last9=Kenworthy |first9=W. Judson |date=2006-12-01 |title=A Global Crisis for Seagrass Ecosystems |journal=BioScience |language=en |volume=56 |issue=12 |pages=987–996 |doi=10.1641/0006-3568(2006)56[987:AGCFSE]2.0.CO;2 |issn=0006-3568 |hdl-access=free |hdl=10261/88476 |s2cid=4936412}}</ref>
+Scientists encourage the protection and continued research of these ecosystems for organic carbon storage, valuable habitat and other ecosystem services.
+Restored seagrass meadows were found to start sequestering carbon in sediment within about four years. This was the time needed for the meadow to reach sufficient shoot density to cause sediment deposition.<ref name="Greiner2013">{{cite journal |last1=Greiner |first1=J. T. |last2=McGlathery |first2=K. J. |last3=Gunnell |first3=J. |last4=McKee |first4=B. A. |year=2013 |title=Seagrass restoration enhances "blue carbon" sequestration in coastal waters |journal=PLOS ONE |volume=8 |issue=8 |page=e72469 |bibcode=2013PLoSO...872469G |doi=10.1371/journal.pone.0072469 |pmc=3743776 |pmid=23967303 |doi-access=free}}</ref>
+=== Deep ocean ===
+{{Further|Carbon sequestration#Sequestration in oceans|Direct deep-sea carbon dioxide injection}}
+[[File:Blue Carbon Levels.jpg|thumb|Blue carbon at coastal, medium and deep ocean levels<ref>{{Cite journal |last1=Bax |first1=Narissa |last2=Barnes |first2=David K. A. |last3=Pineda-Metz |first3=Santiago E. A. |last4=Pearman |first4=Tabitha |last5=Diesing |first5=Markus |last6=Carter |first6=Stefanie |last7=Downey |first7=Rachel V. |last8=Evans |first8=Chris D. |last9=Brickle |first9=Paul |last10=Baylis |first10=Alastair M. M. |last11=Adler |first11=Alyssa M. |last12=Guest |first12=Amy |last13=Layton |first13=Kara K. S. |last14=Brewin |first14=Paul E. |last15=Bayley |first15=Daniel T. I. |date=2022-06-10 |title=Towards Incorporation of Blue Carbon in Falkland Islands Marine Spatial Planning: A Multi-Tiered Approach |journal=Frontiers in Marine Science |volume=9 |pages=872727 |doi=10.3389/fmars.2022.872727 |issn=2296-7745 |doi-access=free |hdl=2164/18700 |hdl-access=free }}</ref>]]The deeper layers of the ocean are greatly unsaturated in CO<sub>2</sub> and its dissolved forms, carbonic and bicarbonic acid, and their salts.<ref>{{Cite web |title=Ocean acidification |url=https://www.noaa.gov/education/resource-collections/ocean-coasts/ocean-acidification |access-date=2023-05-09 |website=www.noaa.gov |language=en}}</ref> At depths greater than 3&nbsp;km, CO<sub>2</sub> becomes liquefied and sinks to the seafloor due to it being higher density than the surrounding seawater. Mathematical models have shown that CO<sub>2</sub> stored in deep sea sediments beyond 3&nbsp;km could provide permanent geological storage<ref>{{Cite journal |last1=House |first1=Kurt Zenz |last2=Schrag |first2=Daniel P. |last3=Harvey |first3=Charles F. |last4=Lackner |first4=Klaus S. |year=2006 |title=Permanent carbon dioxide storage in deep-sea sediments |journal=Proceedings of the National Academy of Sciences |volume=103 |issue=33 |pages=12291–12295 |bibcode=2006PNAS..10312291H |doi=10.1073/pnas.0605318103 |pmc=1567873 |pmid=16894174 |doi-access=free}}</ref> even with large geomechanical perturbations. Deep ocean storage can present a potential sink for large amounts of anthropogenic CO<sub>2</sub>.<ref>{{Cite journal |last1=Leung |first1=Dennis Y.C. |last2=Caramanna |first2=Giorgio |last3=Maroto-Valer |first3=M. Mercedes |year=2014 |title=An overview of current status of carbon dioxide capture and storage technologies |journal=Renewable and Sustainable Energy Reviews |volume=39 |pages=426–443 |doi=10.1016/j.rser.2014.07.093 |s2cid=73620527|doi-access=free |bibcode=2014RSERv..39..426L }}</ref> Other deep water carbon storage techniques currently being explored include, seaweed farming and algae, [[ocean fertilization]], [[artificial upwelling]], and [[basalt]] storage.
+The ''deep blue carbon'' terminology has been used in passing as early as 2017.<ref>{{Cite web |title=Deep blue carbon storage |url=https://www.eurekalert.org/news-releases/509471 |access-date=2023-05-09 |website=EurekAlert! |language=en}}</ref> The [[The Ocean Frontier Institute|Ocean Frontier Institute]] has made it a centrepiece of their participation at [[COP27]].<ref>{{Cite web |title=The Importance of Deep Blue Carbon |url=https://www.ofi.ca/event/cop27-the-importance-of-deep-blue-carbon}}</ref> It is investing significant resources into deep blue carbon research.<ref name=":4">{{Cite web |title=Ocean-Based Carbon Dioxide Removal: Deep Sea Storage |url=https://oceanvisions.org/deep-sea-storage/ |access-date=2023-05-09 |website=Ocean Visions |language=en-US}}</ref> In terms of net-new-carbon sequestration deep blue carbon offers an estimated 10-20 times higher potential than coastal blue carbon to achieve net-zero goals.<ref>{{Cite web |title=A Research Strategy for Ocean Carbon Dioxide Removal and Sequestration |url=https://www.nationalacademies.org/our-work/a-research-strategy-for-ocean-carbon-dioxide-removal-and-sequestration |access-date=2023-05-09 |website=[[National Academies of Sciences, Engineering, and Medicine]]}}</ref> There is still a lack of data in this area along with financial, ecological and environmental concerns.<ref name=":4" /> Advancements in research and technical capabilities are raising international interest in this kind of storage.<ref>{{Cite web |title=Carbon dioxide could be stored below ocean floor, research shows |url=https://www.sciencedaily.com/releases/2022/03/220307113139.htm |access-date=2023-05-09 |website=ScienceDaily |language=en}}</ref><ref name=":3" /><ref>{{Cite web |last=BAS-WOHLERT |first=Camille |title=Undersea graveyard for imported CO2 opens in Denmark |url=https://phys.org/news/2023-03-undersea-graveyard-imported-co2-denmark.html |access-date=2023-05-09 |website=phys.org |language=en}}</ref>
+== Example projects ==
+* [[Microsoft]] and Running Tide signed Two-Year agreement in 2023 to remove up to 12,000 tons of carbon through an ocean-based carbon removal system.<ref>{{Cite web |title=RUNNING TIDE BECOMES MICROSOFT'S FIRST OPEN OCEAN-BASED CARBON REMOVAL SUPPLIER |date=10 March 2023 |url=https://finance.yahoo.com/news/running-tide-becomes-microsofts-first-130000738.html}}</ref>
+* In Canada, a North Atlantic Carbon Observatory (NACO) project is underway to establish an accurate measurement of the ocean's ability to continue to absorb carbon with particular emphasis on deep blue capacity.<ref>{{Cite web |title=Concept Brief: Ocean Carbon Observatory |url=https://global-uploads.webflow.com/61082dc068d2d4fd1cc4461e/61b39939ac261f2a2f807671_Concept%20Brief%20-%20Ocean%20Carbon%20Observatory.pdf}}</ref><ref>{{Cite web |title=North Atlantic Carbon Observatory (NACO) |url=https://www.ofi.ca/impact/policy/ocean-carbon/carbon-observatory |access-date=2023-05-09 |website=www.ofi.ca}}</ref>
+* In Denmark, the "Greensand" project  is underway to capture carbon at source and deposit it in the deep blue regions of the North Sea, creating a 'CO<sub>2</sub> graveyard'. The project is expected to store up to eight million tonnes of CO<sub>2</sub> per year by 2030.<ref>{{Cite web |title=Denmark, the first country to import CO2 and bury it undersea | date=8 March 2023 |url=https://www.euronews.com/2023/03/08/denmark-the-first-country-to-import-co2-and-bury-it-undersea}}</ref>
+* A restoration project in South Australia will cover {{cvt|2,000|ha}} of mangroves, salt marsh and sea grasses extending {{cvt|700|km}} in the [[St Vincents Gulf]] and [[Spencer Gulf]] in [[South Australia]]. The project will also look at various possibilities of insuring the huge expanse of existing blue carbon ecosystems.<ref name="sutton2021">{{cite web |last=Sutton |first=Malcolm |date=13 August 2021 |title=Blue carbon to create 'insurable' value from muddy wetlands in South Australia |url=https://www.abc.net.au/news/2021-08-13/blue-carbon-creating-value-from-magnificent-mud/100371238 |url-status=live |archive-url=https://web.archive.org/web/20210816053611/https://www.abc.net.au/news/2021-08-13/blue-carbon-creating-value-from-magnificent-mud/100371238 |archive-date=16 August 2021 |access-date=16 August 2021 |website=ABC News |publisher=[[Australian Broadcasting Corporation]]}}</ref>
+* In South Korea, macroalgae have been utilized as part of a climate change mitigation program. The country has established the Coastal CO<sub>2</sub> Removal Belt (CCRB) which is composed of artificial and natural ecosystems. The goal is to capture carbon using large areas of [[kelp forest]].<ref name="Chung2013">Chung, I. K., Oak, J. H., Lee, J. A., Shin, J. A., Kim, J. G., & Park, K. S. (2013). Installing kelp forests/seaweed beds for mitigation and adaptation against global warming: Korean Project Overview. ''ICES Journal of Marine Science: Journal du Conseil'', fss206.</ref>
+* [[Marine permaculture]] also fixes carbon in seaweed forest projects offshore in Tasmania and the Philippines, with potential use from the tropics to temperate oceans.<ref>{{cite web |last=Bryce |first=Emma |date=6 July 2020 |title=Can the Forests of the World's Oceans Contribute to Alleviating the Climate Crisis? |url=https://www.resilience.org/stories/2020-07-06/can-the-forests-of-the-worlds-oceans-contribute-to-alleviating-the-climate-crisis/ |url-status=live |archive-url=https://web.archive.org/web/20210417032021/https://www.resilience.org/stories/2020-07-06/can-the-forests-of-the-worlds-oceans-contribute-to-alleviating-the-climate-crisis/ |archive-date=17 April 2021 |access-date=16 August 2021 |website=Resilience}}</ref>
+==See also==
+{{portal|Oceans}}
+* [[Ocean Data Viewer]]: contains datasets on worldwide sea grasses, mangroves and salt marshes
+* [https://oceandecade.org/ UN Decade for Ocean Science for Sustainable Development]
+* [[UN Decade on Ecosystem Restoration]]
+==References==
+{{reflist|30em}}
 == External links ==
+* [[The Ocean Frontier Institute]]
-* [http://www.bluecarbonportal.org GRID-Arendal Blue Carbon Portal]
-* [http://bluecarbonblog.blogspot.no Blue Carbon Blog]
+* [https://www.thebluecarboninitiative.org/ The Blue Carbon Initiative]
+{{climate change}}
+[[Category:Blue carbon| ]]
-{{climate-stub}}
 [[Category:Biological oceanography]]
 [[Category:Biomass]]
-[[Category:Carbon sequestration]]
 [[Category:Chemical oceanography]]
 [[Category:Ecosystems]]