Authors 1
Dr. Atsushi Watanabe 2
Ocean Policy Research Institute, The Sasakawa Peace Foundation
Dr. Tomohiro Kuwae 3Port and Airport Research Institute, National Institute of Maritime, Port and Aviation Technology
Dr. Carlos Manuel Duarte 4
King Abdullah University of Science and Technology
Dr. Ryo Kohsaka 5
The University of Tokyo
Dr. Jay Mar D. Quevedo 6
The University of Tokyo
Mr. Hiromichi Nagai 7
Sterling Partners, LLC

1 This document was prepared to facilitate dialogue at COP 27/CMP17/CMA4 in November for final release in January 2023
under the financial support from the Government of Japan (The Innovation for Cool Earth Forum (“ICEF”) Innovation Roadmap
Project), especially for the policymakers and the enterprises. The contents of this report do not necessarily reflect the views orpolicies of the contributory organizations. The designations employed and the presentations do not imply the expressions of any
opinion whatsoever on the part of contributory organizations concerning the legal status of any country, territory, city, company,or area, its authority, or concerning the delimitation of its frontiers or boundaries.
2 Senior Fellow, Ocean Policy Research Institute of Sasakawa Peace Foundation. Councilor, the International Coral Reef Society.
Representative, the Japanese Coral Reef Society. Formerly: Assistant Professor, the graduate school of information science andengineering, Tokyo Institute of Technology.
3 Group Head, Coastal and Estuarine Environment Research Group Port and Airport Research Institute, National Institute of
Maritime, Port and Aviation Technology. President, Japan Blue Economy Association. Formerly: Adjunct Professor, Center for
Marine Environment Studies, Kumamoto University. Adjunct Associate Professor, Faculty of Urban and Civil Engineering, Tokyo
City University.
4 Distinguished Professor and Professor and Tarek Ahmed Juffali Chair in Marine Ecology, Red Sea Research Center, the King
Abdullah University of Science and Technology. Adjunct Professor, Arctic Research Centre and Department of Bioscience of
Aarhus Universitet. Formerly: Adjunct Professor, University of Trømso. Distinguished Adjunct Professor, King Abdulaziz UniversityJeddah. Director and Winthrop Professor, The University of Western Australia. Research Professor, Instituto Mediterraneo deEstudios Avanzados-Esporles.
5 Professor, Graduate School of Agricultural and Life Sciences, Department of Forest Science, Laboratory of Forest LandscapePlanning and Design, The University of Tokyo. Guest Professor, Graduate School of Environmental Studies Education and ResearchCenter for Sustainable Co-Development, Nagoya University. Guest Professor, Graduate School of Environmental Studies, Tohoku
University.
6 Research fellow, Graduate School of Agricultural and Life Sciences, The University of Tokyo.
7 COO, Sterling Partners, LLC.

Contents
Executive Summary
Chapter 1 Introduction・・・ 1(1) The Development of Blue Carbon(2) The Sink and Reservoir under the UNFCCC(3) Blue Carbon in the Global Discourse

Chapter 2 Scientific Understandings of Blue Carbon・・・ 10(1) The Criteria for Inclusion as actionable Blue Carbon Ecosystems(2) Established Blue Carbon Ecosystem (Mangrove, Salt Marsh, and Seagrass)(3) Natural and Farmed Macroalgae(4) Mitigation in the Open Ocean(5) The Climate Change Adaptation Effects

Chapter 3 Current and Future Technologies to Scale Blue Carbon・・・22(1) Technology to Measure and Track(2) Technology to Create(3) Technology to Protect(4) Technology to Use

Chapter 4 Policy and Institutional Requirements・・・34(1) The Blue Carbon and Nationally Determined Contribution (“NDC”) and national GHG inventories(2) Article 6 of Paris Agreement(3) IPCC guideline revision(4) Requirements for blue carbon projects(5) Environmental concerns from large-scale macroalgal farming on deep-sea biological communities

Chapter 5 Potentials of Carbon Removals by and Credits from Blue Carbon・・・50(1) Changes in Market Perceptions of Blue Carbon(2) Current estimates of carbon removals by blue carbon(3) The Blue Carbon and Voluntary Carbon Mechanisms

Recommendations・・・65

Executive Summary
Climate change action to limit global warming to 1.5 °C above preindustrial levels has come too late to wait. Rapid andeffective emission reductions must be achieved through technological innovation, intersectoral and multisectoralcollaboration, and international cooperation. Simultaneously, examining the carbon sequestration capacity of coastal andocean coastal ecosystems and taking action to maintain, restore, and rehabilitate these ecosystems are important.
The carbon absorbed and sequestered by coastal vegetation, such as mangrove forests, seagrass beds, and salt marshes,
is called coastal blue carbon. The sequestration potential per unit area and sequestration time of coastal blue carbon are
higher than those of terrestrial forests. Expectations are high for its use as a nature-based solution (NbS) and as a negativeemission technology (NET). Large macroalgae (seaweed) beds and macroalgal cultivation, which have been attracting
attention in recent years as new candidates for blue carbon, have yet to establish a unified international scientificmethodology. Nevertheless, the scientific knowledge is accumulating, and methodologies have been developed in Japanand around the world.
In addition to its mitigation function, blue carbon is expected to benefit local communities, thus attracting worldwide
attention. Blue carbon will introduce various synergistic benefits, such as coastal defense, biodiversity maintenance, water
purification, and cultural use value, which are also related to climate change adaptation. As an action that links global andlocal needs and an activity that prompts mitigation, human, and biodiversity “triple benefits,” Blue Carbon Projects are
attracting considerable anticipation.
In this roadmap, Chapter 1 introduces the development of blue carbon in international policy and scientific forums, suchas the United Nations Framework Convention on Climate Change (UNFCCC) and IPCC, and Chapter 2 describes the scientificunderstanding of mangrove forests, seagrass beds, and salt marshes in the context of blue carbon, as well as macroalgal
beds and farming, which are gaining salience for their significant blue carbon potential. Chapter 3 introduces existing
technologies and those expected to be developed in the future to produce, protect, measure, and use blue carbon
ecosystems and their products, especially from macroalgal farming. Chapter 4 describes the points to be considered interms of international treaties, institutional requirements, and environmental impacts when expanding Blue Carbon
Projects to scale. Finally, Chapter 5 describes the current status and potential development of the Blue Carbon Credit asan economic tool necessary to make the Blue Carbon Project a sustainable action and maximize its potential.
Through the above, we envisage that this roadmap will help recognize the gap between the current status of Blue Carbon
and the goals to be reached within the next few decades and provide a roadmap on filling that gap from scientific,
technological, policy, and economic aspects.

Chapter 1
Introduction“Blue Carbon” is a relatively new term coined in a 2009 report compiled primarily by the United Nations Environment
Program (UNEP) 8. Even before the term was coined, international research and discussion on the coastal and oceaniccarbon cycle existed. However, within a decade, a recapping of knowledge on blue carbon and significant progress ininternational research and policy has been observed. This introductory chapter will describe the evolution of ocean
carbon cycle and blue carbon research and concepts in the international community and then present the structure andobjectives of this roadmap.

(1) Development of Blue Carbon
First, we look at the brief discussion of CO2 sinks before the term "blue carbon" was coined and the developments in the
UNFCCC and IPCC since the publication of the Blue Carbon Report in 2009 (Table 1.1). Research on carbon sequestrationin coastal ecosystems, which is connected to the concept of blue carbon, has been available since the 1800s. As longterm observations of atmospheric CO2 concentrations began to reveal increments in atmospheric CO2 concentrations,research on the measurement of CO2 concentrations in the ocean and the role of the ocean and coastal zones in the
carbon cycle became increasingly active. By contrast, seagrass beds, salt marshes, and mangrove forests, which are active
carbon cycle sites in coastal areas, have been declining worldwide due to population growth and development in coastal
areas.
The 2009 Blue Carbon report is the result of a movement to conserve and restore seagrass beds, salt marshes, andmangrove forests, which are important carbon sinks and resources for coastal communities. Since 2009, scientificknowledge on the three ecosystems of seagrass beds, salt marshes, and mangrove forests has been reorganized and theircoverage by the IPCC and UNFCCC has dramatically increased, leading to a significant rise in interest from countries,
academia, and NGOs.
In relation to Table 1.1, we outline the treatment of carbon sinks and storage under the UNFCCC (a) and then summarize
the science and policy developments around the UN system since 2009 (b).

(2) Sink and Reservoir under the UNFCCCThe UNFCCC, adopted in 1992, declares that “All Parties, taking into account their common but differentiatedresponsibilities and their specific national and regional development priorities, objectives, and circumstances, shall:
Promote sustainable management, and promote and cooperate in the conservation and enhancement, as appropriate,of sinks and reservoirs of all greenhouse gases not controlled by the Montreal Protocol, including biomass, forests, andoceans as well as other terrestrial, coastal and marine ecosystems” in Article 4, paragraph 1(d).
The calculation and accounting scope of “Sink” and “Reservoir” have become remarkably comprehensive and inclusive
since the Kyoto Protocol (COP3/1997). In Kyoto Protocol, the scope of “Sink” was only "from direct anthropogenic land
use change and forest activities" and the activities were limited to “new plantations and reforestation, deforestation, and(on an optional choice) forest management 9 since 1990.” In Doha Climate Gateway (COP18/CMP8/2012), “forest
activities” became mandatory from the optional choice, and “Re-flooding of wetlands (peatlands)” was added as an
optional choice from the 2nd commitment period of Kyoto Protocol (2013–2020). The prevailing view is that the scopeshould cover all land use, land-use change, and forestry (LULUCF)-related carbon stock changes from the perspective ofequity and completeness under certain scientific and social rules 10.

8 Nellemann, C., Corcoran, E., Duarte, C. M., Valdrés, L., Young, C. D., Fonseca, L., & Grimsditch, G. (2009). Blue Carbon: The Role of Healthy Oceans in Binding
Carbon. UN Environment, GRID-Arendal.
9 Farmland management, grazing land management, vegetation restoration.
10 The projects related to sink activities under the Clean Development Mechanism (CDM), established as one of the Kyoto Mechanisms (flexibility measures), wereallowed only for "afforestation and reforestation.”1

Table 1.1. Brief history of Blue Carbon and relevant concepts
Year
1841
1914
1981

1992

1997
2005
2009
2010
2012
2013

2015

2018

2019

2021

Main Scientific and Political Events regarding Blue Carbon Concepts
J.B.A. Dumas, a French chemist, published “Leçon sur la Statique Chimique des Etres Organisés” (“The Chemical andPhysiological Balance of Organic Nature,” discussed scientifically about Marine Carbon Cycles 11.
Boysen-Jensen P., a Danish botanist, provided the first estimate of the contribution of Blue Carbon (seagrass) in carbon storage
and burial.
S.V. Smith proposed the role of marine macrophytes in sequestering CO2 and suggested the overlooked role of seagrasses andmacroalgae. 12
Adoption of the United Nations Framework Convention on Climate Change (UNFCCC), entered into force in 1994, in which theultimate objective lies in the stabilization of the greenhouse gas (GHG) concentrations in the atmosphere at a level that would
prevent dangerous anthropogenic interference with the climate system. The meaning of “Sink” is defined as “Any process,activity or mechanism which removes a greenhouse gas, an aerosol or a precursor of a greenhouse gas from the atmosphere”
and “Reservoir” as “a component or components of the climate system where a greenhouse gas or a precursor of a greenhousegas is stored.”
Kyoto Protocol was published, obligating the Annex I Parties to reduce their GHG emissions for the commitment period basedon 1990 (at COP3).
The true-up period of the 1st commitment period of the Kyoto Protocol was decided as 2008–2012.
United Nations Environment Program (UNEP) published “Blue Carbon: The Role of Healthy Oceans in Binding Carbon” in January
2009, which first coined the term “Blue Carbon.”Cancun Agreements published, pledged the Annex I Parties to declare the quantified economy-wide emission reduction targets
for 2020 and submit the annual GHG inventory and progress reports (COP16/COP6).
Doha Climate Gateway published, the true-up period of the 2nd commitment period of the Kyoto Protocol was decided as 2013–2020 and the scope of sinks expanded (LULUCF). Japan, Russia, Canada, and New Zealand left, while the EU, Norway, Australia,
and Switzerland joined (COP18/CMP8).
IPCC Task Force on National Greenhouse Gas Inventories “2013 Supplement to the 2006 Guidelines for National Greenhouse
Gas Inventories: Wetlands” (“Wetlands Supplement”) was accepted at the 37th Session of IPCC held in Batumi, Georgia in
October 2013.

The Paris Agreement was published, indicating all parties to promote the conservation and enhancement of sinks (COP21).
Article 5.1 states “Parties should take action to conserve and enhance, as appropriate, sinks and reservoirs of greenhouse gases
as referred to in Article 4, paragraph 1 (d), of the Convention, including forests.” All parties (regardless of whether Annex I or
non-Annex I) will proceed with the calculation, reporting, and verification of GHG inventories under a common mechanism
while retaining a certain degree of flexibility to consider the capabilities and experience of non-Annex I parties.
An IPCC special report on the impacts of global warming of 1.5 °C (SR15) projected that “intact wetland ecosystems can reduce
the adverse impacts of rising sea levels,” “intensifying storms by protecting shorelines, and their degradation could reduceremaining carbon budgets by up to 100 GtCO2” and “under 1.5°C of warming, natural sedimentation rates are projected to
outpace SLR, but other feedbacks, such as landward migration of wetlands and the adaptation of infrastructure, remain
important” in each medium confidence level.
An IPCC “Special Report on the Ocean and Cryosphere in a Changing Climate” (“SROCC”) released in November 2019. The
Report addresses the improvement of conservation and management of blue carbon ecosystems, which absorb, fix, andsequester carbon dioxide in coastal areas, as a climate change mitigation strategy using marine ecosystems.
The IPCC and the IPBES, providing scientific advice to the UNFCCC and UN CBD, respectively, released their first joint reportexamining the Climate-Biodiversity nexus 13. Blue Carbon actions are highlighted in this report as holding a high potential tocontribute to climate and biodiversity goals while contributing to human well-being at a moderate cost and with minimal or no
unintended consequences.

*The lines in blue are directly related to blue carbon.

(3) Blue Carbon in the Global Discoursea) UNEP” Blue Carbon: The Role of Healthy Oceans in Binding Carbon” published in January 2009
The term “Blue Carbon” was first coined in a United Nations Environment Program (UNEP) report “Blue Carbon: The Roleof Healthy Oceans in Binding Carbon” published in January 2009 14 complied by the experts at GRID-Arendal incollaboration with the UN Food and Agricultural Organization of the United Nations (FAO) and the United Nations
Educational, Scientific, and Cultural Organization International Oceanographic Commissions and other scientists.
The report highlights the carbon fluxes and storage in marine systems. In contrast to the carbon absorbed andsequestered by terrestrial forests and vegetation (“Green Carbon”), this report depicts the importance of coastal

11 Gordon A. Riley.(1994). The Carbon Metabolism and Photosynthetic efficiency of the Earth as a whole, American Scientist, 32(2),129-134
12 Smith, S. V. Marine macrophytes as a global carbon sink. Science 211, 838–840 (1981).
13 Pörtner, H.O., Scholes, R.J., Agard, J., et al.. 2021. IPBES-IPCC co-sponsored workshop report on biodiversity and climate change; IPBES and IPCC
14 See supra note 72

ecosystems in the carbon cycle and catalyzed to draw attention to the necessity and urgency of halting the decline of thecoastal ecosystem. Additionally, the ocean, which is the interconnected body of saline water that covers 71% of the Earth’s
surface, contains 97% of the Earth’s water and provides 99% of the Earth’s biologically habitable space.
The report scientifically presented that more than 50% of the carbon dioxide produced on the Earth is absorbed by theocean and covers ~360 million square kilometers, half of which is stored in the soil, especially in seagrass beds, salt
marshes, and mangrove forests, which cover only 0.5% of the ocean’s surface area (Figure 1.1).

Figure 1.1. Global “Green Carbon” and “Blue Carbon” Cycling 15
The coastal Blue Carbon ecosystems have high carbon burial rates on a per unit area basis and accumulate carbon in theirsoils and sediments. The flow of carbon (in various forms, as carbon dioxide (CO2), carbon in biomass, and carbon
dissolved in the ocean as carbonate and bicarbonate ions) is cycling through the atmosphere, hydrosphere, ocean,terrestrial and marine biosphere, and lithosphere. If degraded or lost, then coastal blue carbon ecosystems are likely torelease some of the carbon back into the atmosphere.
The climate mitigation effectiveness of other natural carbon removal processes in coastal waters, such as macroalgal
ecosystems and proposed nonbiological marine CO2 removal methods, is small or currently has high associateduncertainties. Macroalgal aquaculture warrants further research attention.

b) IPCC Wetlands Supplements in 2013
The IPCC Task Force on National Greenhouse Gas Inventories published the “2013 Supplement to the 2006 Guidelines
for National Greenhouse Gas Inventories: Wetlands” (“Wetlands Supplement”), which constitutes an important scientificmilestone in the development of blue carbon.
In 2010, UNFCCC invited the IPCC to undertake further methodological work on wetlands, focusing on the rewetting andrestoration of peatland, with a view to filling in the gaps in the 2006 IPCC Guidelines for National GHG as Inventories. The
work on the production of the Wetlands Supplement was conducted in 2011–2013 over four Lead Author meetings andtwo rounds of review followed by a round of written comments by governments. The IPCC Government and Expert
Reviews of the Final Draft of the Wetlands Supplement were held in August and September 2013. The Overview Chapterof the Wetlands Supplement was adopted, and the entire report was accepted at the 37th Session of the IPCC (IPCC 37)
held in Batumi, Georgia, in October 2013.
During the multistage review process, which was first conducted by experts and then by governments and experts, expert
reviewers, and governments are invited to comment on the accuracy and completeness of the scientific, technical, andsocioeconomic contents and the overall balance of the drafts.
The IPCC developed the inventory methodological guidance on wetlands, including default emission factor values. Typical

15 Tomohiro Kuwae & Stephen Crooks (2021) Linking climate change mitigation and adaptation through coastal green–gray infrastructure: a perspective,
Coastal Engineering Journal, 63:3, 188-199, DOI: 10.1080/21664250.2021.1935581

3

management practices for organic matter and wet soils related to blue carbon are shown in Figure 1.2. Chapter 4 of theguidelines provides guidance on methodologies for estimating carbon stock changes and CH4 emissions from mangrove
forests, tidal marshes, and seagrass meadows in coastal wetlands and N2O emissions from aquaculture in coastal wetlands.
CO2 and GHG emissions (or absorption) are expressed as the product of the area covered by the activity (called activitydata) and the emission (absorption) factor. The amount of activity can be regarded as the distribution area (above acertain coverage) of blue carbon ecosystems found within the area covered by the activity in the case of conservation,
rehabilitation, or restoration activities. The absorption coefficient is the amount of CO2 absorbed per unit area by thetarget ecosystem.

Figure 1.2. Typical management practices on organic and wet soils 16

16 IPCC (2014). 2013 Supplement to the 2006 IPCC Guidelines for National Greenhouse Gas Inventories: Wetlands. IPCC, Switzerland

4c) IPCC SROCC in 2019
The IPCC “Special Report on the Ocean and Cryosphere in a Changing Climate” (“SROCC”) 17 released in 2019 was animportant scientific milestone. This report addresses the improvement of conservation and management of blue carbon
ecosystems, which absorb, fix, and sequester carbon dioxide in coastal areas, as a climate change mitigation strategy
using marine ecosystems.
In the report on Blue Carbon, the adaptation responses (A), the impacts (I), and the expected benefits (B) in coastal
ecosystems within physical, ecological, social, governance, economic, and knowledge categories are indicated as listed inTable 1.2 (A “+” sign indicates robust evidence and a “-“ indicates medium evidence. Dark blue cells indicate highagreement and light blue indicates medium agreement (denoted by the presence of a sign). A systematic evaluation of
the adaptation responses of blue carbon was conducted based on scientific validity as of 2019.
Table 1.2. Blue Carbon Adaptation Responses (A), Impacts (I), and Benefits (B)Adaptation(A)/Impacts(I)/Benefits(B)
1. Physical Category(A) Supporting physical processes(I) Coastal physical processes disrupted(B) Physical process supported(A) Hard engineering responses(I) Catchment physical processes disrupted(B) Coastal infrastructure resilience increased(A) Soft engineering responses & buffers(I) Coastal infrastructure damage(B) Improved infrastructure functionally(A) Integrated hard & soft engineering(I) Disruption of urban systems(B) Increased structural heterogeneity
2. Ecological Category(A) Ecosystem restoration and protection(I) Ecosystem degradation and loss(B) Ecosystem/ecological resilience supported(A) Bioengineering(I) Biodiversity and genetic diversity loss(B) Physical processes supported(A) Assisted evolution & relocation(I) Habitat range shifts(B) Coastal infrastructure resilience increased(A) Nature-based solutions(I) Sublethal species impacts(B) Increased biodiversity
Social Category(A) Improving access to/storage of natural resources(I) Decreased access to ecosystem services(B) Access to sustainable ecosystem services(A) Sustainable resource use(I) Livelihood impacts(B) Improved socioeconomic services(A) Maintaining or switching livelihoods(I) Increased food insecurity(B) Improved employment and livelihoods(A) Community participatory programs(I) Public health risks increased(B) Improved health
Knowledge Category(A) Better monitoring and modeling(I) Uncertainty for decision makers(B) Informed decision-making tools(A) Integrating knowledge systems(A) Stakeholder identification, outreach, and education

CoastalCommunities
I
A
B

Built
Infrastructure
I
A
B

Fisheries &Aquaculture
I
A
B

CoastalTourism
I A B

-

-

+

+

-

-

+

-

-

Government
I

A

+

B

Health
I

A

B

+

-

+

-

+

+

+

+

-

-

-

-

-

-

+

-

17 https://www.ipcc.ch/site/assets/uploads/sites/3/2022/03/SROCC_FullReport_FINAL.pdf (accessed on January 8, 2023)－

5d）High-Level Panel for a Sustainable Ocean Economy (Ocean Panel) in December 2020
In 2018, Norway co-chairing with Palau led the launch of a high-level panel for a sustainable ocean economy (Ocean
Panel), comprising the leaders of maritime nations. Participating countries as of November 2022 include the following 17
countries: Norway, Palau, Japan, Australia, Canada, Chile, Fiji, Ghana, Indonesia, Jamaica, Kenya, Mexico, Namibia andPortugal, the UK, France, and the USA.
Through its December 2020 High-Level Panel Leaders’ Document, the Ocean Panel is committed to managing 100% of
the ocean area under national jurisdiction sustainably with guidance from the Sustainable Ocean Plans by 2025. The panel
urged all coastal and ocean states to join in this commitment to manage all ocean areas under national jurisdiction
sustainably by 2030.
Sixteen blue papers and special reports were published by the Ocean Panel. One of the reports was “The Ocean as a
Solution to Climate Change: Five Opportunities for Action 18,” which highlighted blue carbon (described as coastal andmarine ecosystems) as one of the five ocean-based solutions for climate change. Assessment revealed that ocean-based
mitigation measures could contribute 4%–12% and 6%–21% by 2030 and 2050, respectively, to limit temperature increase
to within 1.5 °C since the Industrial Revolution.
In the long term, the contribution of ocean-based renewable energy is expected to become substantially large by 2050
due to the expected increase in the scale of offshore wind power generation. However, when considering the next decade
until 2030, the potential for conservation and restoration of blue carbon ecosystems is relatively large (0.9 GtCO2e yr−1),
accounting for up to 25% of total ocean-based solutions.

e) IPCC AR6 Synthesis Report (late 2022 or early 2023)
The IPCC is currently in its Sixth Assessment cycle; the AR6 Synthesis Report (SYR)19 will be finalized in late 2022 or early2023. The AR6 SYR is based on the content of the following three Working Groups Assessment Reports: WGI – The PhysicalScience Basis; WGII—Impacts, Adaptation, and Vulnerability; WGIII—Mitigation of Climate Change (Table 1.3 and thethree Special Reports: Global Warming of 1.5 °C, Climate Change and Land, and the Ocean and Cryosphere in a Changing
Climate).
The first section, namely “Current Status and Trends,” covers the historical and present period. The second section,
namely “Long-term Climate and Development Futures,” addresses projected futures up to 2100 and beyond. The final
section, namely “Near-term Responses in a Changing Climate,” considers current international policy timeframes and thetime interval between now and 2030–2040.
Table 1.3. IPCC AR6 Synthesis Report Contents
Synthesis Report of AR6 (Synthesis Report)
Comprising two parts: a Summary for Policymakers (SPM) of 5 to 10 pages and a Long Report of 30 to 50 pages. Approval and distributionof the AR6 Synthesis Report are expected in early 2023. 21 Nov–15 Jan 2023 SYR Final Government Distribution.
Working Group I Report (Physical Science Basis)
Addressing the most up-to-date physical understanding of the climate system and change, bringing together the latest advances in climate
science, and combining multiple lines of evidence from paleoclimate, observations, process understanding, and global and regional climate
simulations.
Working Group II Report (Impacts, Adaptation, and Vulnerability)
Assessing the impacts of climate change from a worldwide to a regional view of ecosystems and biodiversity and of humans and their diverse
societies, cultures, and settlements. This report considers their vulnerabilities and the capacities and limits of these natural and humansystems to adapt to climate change and thereby reduce climate-associated risks together with options for creating a sustainable future forall through an equitable and integrated approach to mitigation and adaptation efforts at all scales.
Working Group III Report (Mitigation of Climate Change)
Assessing all aspects of mitigation, including technical feasibility, cost, and the enabling environments that would allow measures to be

18 Hoegh-Guldberg. O., et al. 2019. ‘‘The Ocean as a Solution to Climate Change: Five Opportunities for Action.’’ Report. Washington, DC: World Resources
Institute. Available online at http://www.oceanpanel.org/climate (accessed on January 8, 2023)
19 According to IPCC procedures, the SYR should “synthesize and integrate materials contained within the Assessment Reports and Special Reports” and “should
be written in a non-technical style suitable for policymakers and address a broad range of policy-relevant but policy-neutral questions approved by the Panel.”
The report comprises two parts: a Summary for Policymakers (SPMs) of 5 to 10 pages and a Long Report of 30 to 50 pages.

6

taken. Enabling environments cover policy instruments, governance options, and social acceptability. Synergies and tradeoffs withadaptation measures as well as co-benefits, risks, and links to sustainable development are of increasing interest. Taking a near-term
perspective relevant to decision makers in the government and the private sector and a long-term perspective that helps identify how highlevel climate policy goals might be met.

In the Working Group I Report (Physical Science Basis), the SROCC discussions mentioned Blue Carbon as one of the
carbon dioxide removal (CDR) methods and current potentials are shown below (Table 1.4). Therefore, the feasibility ofopen ocean fertilization and alkalinization approaches was negligible due to their inconclusive influence on ocean carbon
storage on long time scales, unintended side effects on marine ecosystems, and associated governance challenges. The
assessment of blue carbon ecosystems concluded their minimal contribution to global atmospheric CO2 reduction butemphasized that the benefits of protecting and restoring coastal blue carbon extend beyond climate change mitigation.
Table 1.4. Characteristics of various Carbon Dioxide Removal (CDR) methods including Blue Carbon 20
Methods(Category Methods)

StatusCost
Mitigation
Nature of CO2 Removal Process/Storage(TRL*(USD tPotential
Form Description
−1
-1
)
CO2 )
(GtCO2 yr )Category I: Enhanced biological production and storage on land (in vegetation, soils, or geologic formations)
Afforestation, reforestation,
0–Store carbon in trees and soils by
and forest management(8–9)
0.5–10240
planting, restoring, or managing forests(Biological/Organic)
Soil carbon sequestration
45–
Use agricultural management practices(8–9)
0.6–9.3(Biological/Organic)
100
to improve soil carbon storage
Burn biomass at high temperature under
Biochar10–(6–7)
0.3–6.6
anoxic conditions to form biochar and(Biological/Organic)345
add to soils
Insuffi(8–
Peatland restoration
Store carbon in soil by creating or
cient
0.5–2.1※(Biological/Organic)
restoring peatlands
9)※
Data
Bioenergy with carbon
Production of energy from plant biomass
15–
capture and storage (BECCS)(5–6)
0.5–11
combined with carbon capture and400(Biological/Inorganic)storage
Category II: Enhanced biological production and storage in coastal and open ocean
Fertilize upper ocean with micro (Fe) andmacronutrients (N, P) to increase
Ocean fertilization
50–
1–2
1–3
phytoplankton photosynthesis and(Biological/Organic)500
biomass and deep ocean carbon storage
through the biological pumpTime Scale of Carbon Storage(Factors that Affect Carbon Storage
Time Scale)

Decades to millennia(ocean stratification and circulation;
efficiency of carbon sequestration in
deep ocean)

Uncertain-

Pump nutrient-rich deep ocean water tothe surface to increase carbon uptake
and storage through the biological pump

Centuries to millennia (ocean
circulation; dissolved inorganic carbon
content of upwelled waters)

Warming beyond
temperatures
experienced if
artificial ocean
upwelling had notbeen deployed

0.5–2.1※

Manage coastal ecosystems to increase
net primary production and store carbon
in sediments

Decades to centuries if functional
integrity of ecosystem maintained(Land-use change of coastal
ecosystems, extreme weather (e.g.,
heatwaves and sea level change)

None

Spread alkaline minerals on land to
remove atmospheric CO2 in reactions
that form solid minerals chemically(carbonates and silicates) that are storedin soils or in the ocean

10,000 to 106 years(Storage in soils or ocean)

None

Artificial ocean upwelling(Biological/Organic)--

Restoration of vegetatedcoastal ecosystems (Blue
Carbon)(Biological/Organic)

(8–
9)※

Insufficient
Data

Termination
Effects

Decades to centuries (disturbances(e.g., fires, pests), extreme weather)

None

Decades to centuries(Soil and crop management)

None

Decades to centuries(Fire)

None

Decades to centuries (Peatland
drainage, fire, drought, land-use
change)Potentially permanent –analogous todirect air carbon capture with carbon(Leakage)

None

None

Category III: Enhanced geochemical processes on land and in ocean
Enhanced weathering(Geochemical/Inorganic)

Ocean alkalinization(Geochemical/Inorganic)

3–4

50–
200
(24–
578)

1–2

40–
260

6

100–
300
(84–
386)

2–4 (<1–
95)

1–100

Increased CO2 uptake via increased
alkalinity by deposition of alkaline
minerals (e.g., olivine)

10,000 to 100,000 years(Carbonate chemistry; ocean
stratification and circulation)

Higher rates ofwarming andacidification than if
alkalinization had
not begun (undera high emission
scenario)

5–40

Direct removal of CO2 from air throughchemical adsorption, absorption ormineralization, and storage undergroundin deep ocean or in long-lasting usable
materials

Potentially permanent(Leakage)

None

Category IV: Chemical
Direct air carbon capture
with storage (DACCS)(Chemical/Inorganic)* TRL means “Technology Readiness Level”. (※) is the total amount of Peatland restoration and Restoration of vegetated coastal ecosystems.

20 IPCC (2021). 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.

7

In the Working Group II Report (Impacts, Adaptation, and Vulnerability) and the Working Group III Report (Mitigation of
Climate Change), which are both based on the SROCC discussions, the impacts and the mitigation and restoration
potentials were analyzed for three coastal Blue Carbon ecosystems as shown below (Table 1.5).
Table 1.5. Impacts on organic carbon storage and burial rates in mangroves, salt marshes, and seagrass.

Sea Level Rise

Extreme Storms

Warming

Risingconcentrations ofatmospheric CO2

Landward expansion by vegetation
Coastal squeeze
Loss of low-lying or submerged land or vegetation
Human adaptation to increase accommodation
space
Erosion, loss of area, subsidence
Enhanced sedimentation
Vegetation damage and mortality
Increased productivity
Vegetation mortality
Increased decomposition of soil
Poleward expansion of mangroves
Poleward expansion of seagrasses
Poleward expansion of bioturbators
Change in dominant species
Increased productivity of some species
Biodiversity loss

Mangroves
+C
−C
−C
+C

Salt marshes
+C
−C
−C
+C

Seagrasses
+C
−C
−C

−C
+C
−C to +C+C

−C
+C

0 to −C
+C
−C
+C
−C

−C
+C

−C to +C
−C
+C

ΔC
ΔC
ΔC
−C

ΔC

+C

Vegetation mortality−C
Reduced productivity−C−C
AlteredIncreased productivity+C+C
precipitation
Increased remineralization−C−C
Low-salinity events
0 to −C“+C” indicates potential positive effects on blue carbon stocks, “−C” indicates potential negative effects, “0” indicates no effects, and “ΔC” indicates positive
potential or negative effects.

Blue Carbon data (e.g., carbon accumulation and sequestration rates) vary widely depending on the climatic andsedimentary conditions of each region. Additionally, the quantification of their overall mitigation value is difficult due tothe variable production of CH4 and N2O uncertainties considering the provenance of the accumulated carbon and therelease of CO2 by biogenic carbonate formation in seagrass ecosystems.
The median costs of CDR methods are estimated as 240, 30,000, and 7800 USD per tCO2 for mangroves, salt marsh, andseagrass management, respectively. Currently, estimated cost-effectiveness (for climate change mitigation) is generally
remarkably low. The total potential carbon sequestration rate through blue carbon CDR is generally estimated in the range
0.02–0.08 GtCO2 yr-121. Gattuso et al. (2021) 22 estimated the theoretical cumulative potential of coastal blue carbon
management to be 95 GtCO2 by 2100 considering the maximum area that can be occupied by these habitats and historiclosses of mangrove, seagrass, and salt marsh ecosystems.
The blue carbon science has evolved, thereby encompassing different scientific fields, engaging actors at various scales,and emerging in multiple international climate change discussions since its conception in 2009 based on a recent
assessment of peer-reviewed and gray publications (Quevedo et al., accepted). As presented in Table 1.6, the blue carbon
research has progressed from potential blue carbon payments to quantifying blue carbon stocks from 2009 to 2015.
These years also focused on understanding and investigating carbon dynamics in coastal ecosystems. The years 2016 to2018 had witnessed a growth of mapping blue carbon ecosystems across the world using various technologies. This
information has paved the way to the emergence of multidisciplinary approaches in blue carbon research, particularly
toward their management and restoration. Consequently, this phenomenon led to an increase in social and policy-driven
investigations in 2021. However, challenges in bringing blue carbon to market and project implementations in theinternational arena remain despite the progressive development.

21 Babiker, M., G. Berndes, K. Blok, B. Cohen, A. Cowie, O. Geden, V. Ginzburg, A. Leip, P. Smith, M. Sugiyama, F. Yamba (2022). Cross-sectoral perspectives. In
IPCC, 2022: Climate Change 2022: Mitigation of Climate Change. Contribution of Working Group III to the Sixth Assessment Report of the Intergovernmental
Panel on Climate Change [P.R. Shukla, J. Skea, R. Slade, A. Al Khourdajie, R. van Diemen, D. McCollum, M. Pathak, S. Some, P. Vyas, R. Fradera, M. Belkacemi, A.
Hasija, G. Lisboa, S. Luz, J. Malley, (eds.)]. Cambridge University Press. Based on Wilcox, J., P.C. Psarras, and S. Liguori (2017). Assessment of reasonable
opportunities for direct air capture. Environ. Res. Lett., 12(6).
22 Gattuso, J.-P. et al. (2021). The Potential for Ocean-Based Climate Action: Negative Emissions Technologies and Beyond. Frontiers in Climate, Vol. 2, p. 37

8

Thus far in the introduction, we have examined the evolution of the blue carbon debate, mainly in the international policy
arena. This roadmap aims to examine the potential for progress on Blue Carbon over the next 10 to 30 years. Chapter 2
summarizes the current state of scientific knowledge on Blue Carbon, which is the basis for policy trends, with a particularemphasis on natural macroalgal beds and macroalgae cultivation, which have been the focus of increasing attention inrecent years. Chapter 3 summarizes the current status and future prospects of methods for quantitatively evaluating theexisting amount, dynamics, and sequestration rate of blue carbon, technologies for protecting and increasing blue carbon
through conservation, restoration, and creation, and technologies for utilizing blue carbon, especially macroalgae.
Chapter 4 describes the institutional, legal, and ethical considerations and potential challenges in promoting the Blue
Carbon Project, particularly considering large-scale macroalgal aquaculture. Chapter 5 summarizes mitigation measuresand the potential for carbon credits in the event of progress in blue carbon conservation, restoration, and creation. We
conclude with recommendations for future consideration after examining the above discussion.
Table 1.6. Timeline and progress of Blue Carbon research since its conception in 2009

*Notable publications and significant contributions in blue carbon research are reflected on the basis of the review of1179 documents (peer-reviewed and gray publications) 23

23 Quevedo, J. M. D., Uchiyama, Y., & Kohsaka, R (2023). Progress of blue carbon research: 12 years of global trends based on content analysis of peer-reviewed
and “gray literature” documents. Ocean and Coastal Management. Accepted.

9Chapter 2
Scientific Understandings of Blue Carbon(1) Criteria for Inclusion as actionable Blue Carbon Ecosystems
Blue Carbon has multiple definitions. Established and emerging areas in scientific and political fields currently exist in the
climate change mitigation and conservation measures using Blue Carbon. Lovelock and Duarte (2019)24 summarized theassessment of disciplines and criteria for inclusion as actionable Blue Carbon based on the current status of the scienceor policy (Table 2.1). Mangrove forests, tidal marshes, and seagrass meadows are established Blue Carbon ecosystems
because they often have high carbon stocks, support long-term carbon storage, offer the potential to manage GHG
emissions, and support other adaptation policies. Some marine ecosystems do not meet key criteria for inclusion within
the Blue Carbon framework (e.g., oyster and coral reefs). Others are potential emerging Blue Carbon but have gaps inscientific understanding of carbon stocks or greenhouse gas fluxes. Moreover, potential for management or accounting
for carbon sequestration (macroalgae and phytoplankton) is currently limited.
In addition to the blue carbon ecosystems already defined as actionable, this roadmap will primarily focus on natural andcultivated macroalgae: mangrove forests, salt marshes, and seagrass beds. Despite their exclusion in the IPCC Guidelines,
we focus on natural and farmed macroalgae because scientific knowledge has dramatically accumulated in recent years
and their quantitative potential is estimated to be sufficiently large to be manageable by humans.
Table 2.1. Criteria for Inclusion as actionable Blue Carbon Ecosystem (adopted from Lovelock and Duarte, 2018)

MangroveTidal Marsh
Seagrass
Macroalgae
Salt Flats(Sabkhas)Freshwater
Tidal Forest
Phytoplankton
Coral Reef
MarineFauna (fish)
Oyster Reefs

Scale of GHG
removals or
emissionsaresignificant

Longterm
storageof fixed
CO2

Undesirable
anthropogenic
impacts on theecosystem

Yes
Yes
Yes
Yes
Uncertain

Yes
Yes
Yes
Uncertain
Uncertain

Yes
Yes
Yes
Yes
Yes

Management ispractical/possib
le to maintain/enhance C
stocks andreduce GHG
emissions
Yes
Yes
Yes
Yes
Uncertain

Interventio
ns have nosocial or
environme
ntal harm

Alignmentwith otherpolicies:
mitigation
andadaptation

Uncertain
Uncertain
Yes
Uncertain
Uncertain

Yes
Yes
Yes
Yes
Uncertain

Uncertain

Yes

Yes

Yes

Uncertain

Uncertain

Yes
No
No

Uncertain
No
No

Uncertain
Yes
Yes

Uncertain
No
No

Uncertain
Uncertain
Uncertain

No
Yes
No

No

Uncertain

Yes

No

Yes

Yes

The use of phytoplankton as a climate change mitigation strategy has been proposed since the first ocean fertilization
experiments were conducted in the 1990s. A hypothesis indicates the existence of ocean areas with sufficient macro
nutrients, such as nitrogen and phosphorus in the surface seawater but few phytoplankton due to a lack of micronutrients,
especially iron. Thirteen major experiments have been conducted since the 1990s to date, and the evidence that large
amounts of fixed carbon reach the deep ocean is ambiguous 25. Various adverse effects have been indicated, including thepotential occurrence of harmful algal blooms. In 2008, the UN Convention on Biological Diversity (CBD) decided to placea moratorium on all marine fertilization projects, except for small-scale ones in coastal waters. Five years later, the London
Convention on Marine Pollution adopted rules for assessing marine fertilization research.

24 Lovelock Catherine E. and Duarte Carlos M (2019).Dimensions of Blue Carbon and emerging perspectives. Biology Letters.
25 Tollefson, J (2017). Iron-dumping ocean experiment sparks controversy. Nature 545, 393–394.

10

Marine Fauna (including fish, marine mammals, and invertebrates) influence the carbon cycle of the ocean through arange of processes, including consumption, respiration, and excretion. The net carbon sequestration benefit from marine
fauna, once allowance is made for respiration over the lifetime of the animal, respiration and carbon output from thespecies feeding on feces and carcasses before final burial in the seafloor, remains uncertain. Marine Fauna activity canstimulate production by plants (Lapointe et al., 2014 26 ) and phytoplankton, leading to sequestration of 0.0007
GtCO2e/year (Lavery et al., 2010 27). Populations of vertebrates are an important component of the carbon cycle in ocean
ecosystems (Schmitz et al., 2018 28), including predators, which can regulate grazers (Atwood et al., 2015 29) and may be
given consideration when developing policies to secure nature-based carbon functions.
Other coastal ecosystems that are considered Blue Carbon ecosystems include tidally influenced forests. For example,
bald cypress and Melaleuca forests, which can have enormous soil carbon stocks in their soils, have been markedly
reduced in cover. Sabkhas, which comprise high intertidal salt flats dominated by microbial mats and can be extensive inarid environments, may also be candidates for Blue Carbon-based conservation despite the currently limited information
on C stocks and fluxes and on their role in adaptation to climate change.

(2) Established Blue Carbon Ecosystem (Mangrove, Salt Marsh, and Seagrass)
Mangrove, salt marsh, and seagrass ecosystems (Figure 2.1) fall within the IPCC definition of “wetlands” and mangroves
are often classified as “forests” (and therefore often included in national forest inventories), enabling their inclusion
within GHG accounting guidance of the IPCC. The IPCC provided emission factors (CO2, CH4, and N2O) for land-use change
in coastal wetlands for activities that result in loss and conversion or those leading to restoration. Mangroves, where they
are included in national forest inventories, may also be included in existing GHG reduction schemes, such as Reduced
Emissions from Deforestation and Degradation and fostering conservation (REDD+).
Subsequent use of the term has focused on carbon-accumulating coastal habitats structured by rooted plants, such as
mangroves, tidal salt marshes, and seagrass meadows, which are relatively amenable to management (Lovelock andDuarte, 2019 30). Comparisons across the full range of freshwater and saline wetland types are assisted by standardized
approaches (Vázquez-González et al., 2017 31).
A total of 20%–50 % of global blue carbon ecosystems have already been converted or degraded, leading some analysts
to conclude that restoring wetlands can offer 14 percent of the mitigation potential needed to hold global temperature
to below 2°C above the preindustrial period (Griscom et al., 2017 32). Rates of mangrove loss have declined from 2.1%/yearin the 1980s (Valiela et al., 2001 33 ) to 0.11%/year in the past decade (Bunting et al., 2018 34 ) due to improved
understanding, management, and restoration (Lee et al., 2019 35). However, mangrove areas still emit an estimated 0.007
GtCO2e/year (Atwood et al., 2017 36). Rates of loss and degradation of seagrass cover are between 2% and 7%/year mainly

26 Gea-Izquierdo, G., Bergeron, Y., Huang, J. G., Lapointe-Garant, M. P., Grace, J. & Berninger, F.(2014). The relationship between productivity and tree-ring
growth in boreal coniferous forests. Boreal Env. Res. 19: 363–378.
27 Trish J. Lavery, Ben Roudnew, Peter Gill, Justin Seymour, Laurent Seuront, Genevieve Johnson, James G. Mitchell and Victor Smetacek (2010). Iron defecationby sperm whales stimulates carbon export in the Southern Ocean. Proceedings of the Royal Society Biological Sciences 22 November 2010. vol 277. Issue 1699
28 Corinna Bang, Tal Dagan, Peter Deines, Nicole Dubilier, Wolfgang J. Duschl, Sebastian Fraune, Ute Hentschel, Heribert Hirt, Nils Hülter, Tim Lachnit, Devani
Picazo, Lucia Pita, Claudia Pogoreutz, Nils Rädecker, Maged M. Saad, Ruth A. Schmitz, Hinrich Schulenburg, Christian R. Voolstra, Nancy Weiland-Bräuer, Maren
Ziegler, Thomas C.G. Bosch(2018).Metaorganisms in extreme environments: do microbes play a role in organismal adaptation?. Zoology, Volume 127,1-19.
29 Atwood, T., Connolly, R., Ritchie, E. et al(2015). Predators help protect carbon stocks in blue carbon ecosystems. Nature Clim Change 5, 1038–1045.
30 Catherine Lovelock and Carlos M Duarte (2019). Dimensions of Blue Carbon and emerging perspectives. Biology Letters. Vol. 15. Issue 3. Royal Society
31 Vázquez-González, C., Moreno-Casasola, P., Hernández, M.E. et al(2017). Mangrove and Freshwater Wetland Conservation Through Carbon Offsets: A CostBenefit Analysis for Establishing Environmental Policies. Environmental Management 59, 274–290.
32 Griscom, B. W., Adams, J., Ellis, P. W., Houghton, R. A., Lomax, G., Miteva, D. A., Schlesinger, W. H., Shoch, D., Siikamäki, J. V., Smith, P., Woodbury, P., Zganjar,
C., Blackman, A., Campari, J., Conant, R. T., Delgado, C., Elias, P., Gopalakrishna, T., Hamsik, M. R., … Fargione, J. (2017). Natural climate solutions. Proceedingsof the National Academy of Sciences of the United States of America, 114(44), 11645–11650
33 Ivan Valiela, Jennifer L. Bowen, Joanna K. York(2001). Mangrove Forests: One of the World's Threatened Major Tropical Environments: At least 35% of thearea of mangrove forests has been lost in the past two decades, losses that exceed those for tropical rain forests and coral reefs, two other well-known
threatened environments. BioScience, Volume 51, Issue 10, October 2001, 807–815.
34 Bunting, P.; Rosenqvist, A.; Lucas, R.M.; Rebelo, L.-M.; Hilarides, L.; Thomas, N.; Hardy, A.; Itoh, T.; Shimada, M.; Finlayson, C.M.(2018). The Global Mangrove
Watch—A New 2010 Global Baseline of Mangrove Extent. Remote Sens.10(10).1669.
35 Lee, S.Y., Hamilton, S., Barbier, E.B. et al. Better restoration policies are needed to conserve mangrove ecosystems. Nat Ecol Evol 3, 870–872 (2019).
36 Trisha B. Atwood, Rod M. Connolly, Hanan Almahasheer, Paul E. Carnell, Carlos M. Duarte, Carolyn J. Ewers Lewis, Xabier Irigoien, Jeffrey J. Kelleway, Paul S.
Lavery, Peter I. Macreadie, Oscar Serrano, Christian J. Sanders, Isaac Santos, Andrew D. L. Steven & Catherine E. Lovelock (2017). Global patterns in mangrove
soil carbon stocks and losses. Nature Climate Change volume 7, 523–528

11due to pollution of coastal waters (Waycott et al., 2009 37). Emissions are estimated at 0.05 to 0.33 GtCO2e/year (Pendleton
et al., 2012 38), although gains in cover have recently been observed in Europe (de los Santos et al., 2019 39). Global rates
of salt marsh loss are uncertain (1%–2% per year), but losses are estimated to be responsible for 0.02 to 0.24 GtCO2e/year(Pendleton et al., 2012). The area covered by blue carbon ecosystems is equivalent to only 1.5% of terrestrial forest cover;
however, their loss and degradation are equivalent to 8.4% of CO2 emissions from terrestrial deforestation because of
their high carbon stocks per hectare (Griscom et al., 2017).

Figure 2.1. Global Distribution of the Established Blue Carbon Ecosystem 40
The area of mangroves and salt marshes may also be adversely affected by sea level rise in some regions (Lovelock et al.,2015) but could expand in others (Schuerch et al., 2018 41), increasing their mitigation benefits. Sea level rise will affecthabitat areas for all coastal vegetated ecosystems as well as their mitigation potential (Schuerch et al., 2018). The impactof sea level rise on these ecosystems will be strongly influenced by the following: human activities (e.g., sediment supply,
land-use changes, population, and seawall defenses), the effects of climate change on adjacent ecosystems (such as coral
reefs, mudflats, or barrier islands), and GHG emissions from freshwater wetlands (Luo et al., 2019 42). Extreme events
could also reduce the effectiveness of restoration. Small-scale macroalgae cultivation is considered low risk; however, alarge-scale expansion of the industry requires a considerable understanding of impacts and the balance of environmental
risks and benefits that macroalgae cultivation projects can offer (Campbell et al., 2019 43). In addition to climate change,marine and coastal ecosystems are also vulnerable to failure due to socioeconomic factors, including inadequate andinappropriate incentives (Lee et al., 2019). Similar to those developed for forests (Chhatre et al., 2012 44), social safeguards
should also be established.
The estimated mitigation potential of coastal and marine ecosystems (Figure 2.2) is via the two main pathways.
37 Michelle Waycott, Carlos M. Duarte, Tim J. B. Carruthers, Robert J. Orth, William C. Dennison, Suzanne Olyarnik, Ainsley Calladine, James W. Fourqurean,Kenneth L. Heck, Jr., A. Randall Hughes, Gary A. Kendrick, W. Judson Kenworthy, Frederick T. Short, and Susan L. Williams(2009). Accelerating loss of seagrasses
across the globe threatens coastal ecosystems. Proceedings of the National Academy of Sciences of the United States of America, 106 (30).12377-12381
38 Pendleton L, Donato DC, Murray BC, Crooks S, Jenkins WA, et al. (2012) Estimating Global “Blue Carbon” Emissions from Conversion and Degradation of
Vegetated Coastal Ecosystems. PLOS ONE 7(9)39 de los Santos, C.B., Krause-Jensen, D., Alcoverro, T. et al. (2019). Recent trend reversal for declining European seagrass meadows. Nat Commun 10, 3356.
40 Peter I. Macreadie, Micheli D. P. Costa, Trisha B. Atwood, Daniel A. Friess, Jeffrey J. Kelleway, Hilary Kennedy, Catherine E. Lovelock 2, Oscar Serrano andCarlos M. Duarte (2021).Blue Carbon as a natural climate solution. Nature Reviews Earth & Environment 2(12)41 Mark Schuerch, Tom Spencer, Stijn Temmerman, Matthew L. Kirwan, Claudia Wolff, Daniel Lincke, Chris J. McOwen, Mark D. Pickering, Ruth Reef, Athanasios
T. Vafeidis, Jochen Hinkel, Robert J. Nicholls & Sally Brown(2018).Future response of global coastal wetlands to sea-level rise. Nature volume 561, pages231–
234
42 Luo, M., Huang, JF., Zhu, WF. et al(2019). Impacts of increasing salinity and inundation on rates and pathways of organic carbon mineralization in tidal
wetlands. Hydrobiologia 827, 31–49.
43 Justin E. Campbell, Andrew H. Altieri,Lane N. Johnston,Caitlin D. Kuempel,Richard Paperno,Valerie J. Paul,J. Emmett Duffy(2018). Herbivore community
determines the magnitude and mechanism of nutrient effects on subtropical and tropical seagrasses. British Ecological Society Journal of Ecology. Vol.106. 401-

412

44 Ashwini Chhatre, Shikha Lakhanpal, Anne M Larson, Fred Nelson, Hemant Ojha, Jagdeesh Rao(2012). Social safeguards and co-benefits in REDD+: a review of
the adjacent possible. Current Opinion in Environmental Sustainability, Vol 4(6), 654-660.

12

1.

Conserving and protecting blue carbon ecosystems, which involves stopping the loss and degradation of theseecosystems, thus avoiding direct land-use change emissions and additional emissions from alternative land use, suchas agriculture.
2. Restoration and expansion of degraded blue carbon ecosystems, which involves rehabilitating the soil and associatedorganisms, thereby restoring their ability to sequester and store carbon.
The World Economic Forum (2021) 45 illustrated the mitigation potential of land-based ecosystems to blue carbon
ecosystems. The mitigation potential of restoring green carbon ecosystems, notably forests, is generally high, while thatof blue carbon ecosystems per unit area is substantially high.

Figure 2.2. Mitigation Potential per Unit Area of Restoring Land-based and Marine Ecosystems
Achieving high levels of mitigation through conservation and restoration is dependent on increased investment inprotection, restoration, and enabling the expansion of ecosystem cover where sea level rise provides new opportunities.
However, ambitious conservation and restoration targets must be considered within local socioeconomic contexts toprevent perverse outcomes (Lovelock and Brown 2019). Efforts to restore blue carbon ecosystems are growing in number,area, and success (Unsworth et al., 2018 46; Lee et al., 2019 47; Gittman et al., 2019 48, Kuwae and Hori, 2019 49) but remain
relatively small scale in most instances (An exception is the 589 km2 of salt marsh restoration in the United States between
2006 and 2015, Gittman et al., 2019 50).
Estimates of CO2 emissions associated with prevented anthropogenic degradation of mangrove, salt marsh, and seagrassecosystems are sensitive to uncertainties in global cover and loss rates (2%–7%/year), which is particularly the case forseagrass (Table 2.2). Estimates of salt marsh area and its losses (1%–2%/year) are also uncertain (McOwen et al., 2019 51).
Losses of mangrove ecosystems have slowed in the last decades (Table 2.2); thus, emissions associated with their losses
have also declined compared to those estimated by Pendleton et al. (2012). The range in potential mitigation that could
be achieved through restoration of mangroves, salt marshes, and seagrass ecosystems varied with the level of effort andinvestment. Low-end estimates of mitigation that could possibly be achieved through restoration by 2050 are 0.2 GtCO2e/
year, reflecting limited restoration activities and success (Table 2.3).

45 World Economic Forum (2021). Green New Deals: These blue carbon ecosystems could slow climate change.
46 Unsworth, R.K.F., L.M. Nordlund, and L.C. Cullen-Unsworth (2018).Seagrass Meadows Support Global Fisheries Production. Conservation Letters. 12:e12566.
47 Lee, S.Y., S. Hamilton, E.B. Barbier, J. Primavera, and R.R. Lewis (2019). Better Restoration Policies Are Needed to Conserve Mangrove Ecosystems.Nature
Ecology & Evolution 3 (6): 870.
48 Keller, D A., R.K. Gittman, M.C. Brodeur, M.D. Kenworthy, J.T. Ridge, L.A. Yeager, A.B. Rodriguez, and F.J. Fodrie (2019). Salt Marsh Shoreline Geomorphology
Influences the Success of Restored Oyster Reefs and Use by Associated Fauna. Restor Ecol.
49 Kuwae, T., and M. Hori (2019). The Future Of Blue Carbon: Addressing Global Environmental Issues.In Blue Carbon in Shallow Coastal Ecosystems. 347‒73.
Singapore: Springer.
50 Keller, D A., R.K. Gittman, M.C. Brodeur, M.D. Kenworthy, J.T. Ridge, L.A. Yeager, A.B. Rodriguez, and F.J. Fodrie (2019). Salt Marsh Shoreline Geomorphology
Influences the Success of Restored Oyster Reefs and Use by Associated Fauna. Restor Ecol.
51 McOwen, H Klimmek, L Weatherdon. Monitoring and Indicators. Background briefs for 2020 Ocean Pathways Week, 201913

Ecosystem
Mangroves
Salt Marshes
Seagrasses
Macroalgae

Table 2.2. Global Extent and Loss Rates of Blue Carbon Ecosystems 52
Areal Cover (square km)
Recent Rates of Loss (% Year)138,0000
0.11
55,000
1–2
325,000
2–7
3,540,000
Unknown

Information on the dynamics of GHGs other than CO2 (CH4 and N2O) in the established blue carbon ecosystems. Somestudies suggest that mangrove forests are net sources of CH4 globally, and the CH4 emissions can offset C burial inmangroves by 20 % 53. In contrast, some mangrove forests are sinks for N2O 54. However, no concurrent measurements of
CO2, CH4, and N2O at relevant temporal and spatial scales are unavailable, and future research is needed.
Table 2.3. Summary of Mitigation Potential from Blue Carbon Ecosystems(Coastal and Marine Ecosystem) by 2030 and 2050
Mitigation Option
Conservation: potential mitigationfrom halting loss and degradationof ecosystems (avoided emissions)
Restoration: potential mitigationfrom restoring and rehabilitating
ecosystems and organisms
Increased macroalgae production
via aquaculture
End overexploitation of the ocean
to support recovery of biodiversity
and increase biomass
Total

Description
Mangroves
Salt/tidal marshes
Seagrasses
Macroalgae
Mangroves
Salt/tidal marshes
Seagrasses
Macroalgae－－－

Mitigation Potential 2030
(GTCO2E/YEAR)
0.02–0.04
0.04–0.07
0.19–0.65

Mitigation Potential
2050 (GTCO2E/YEAR)

Knowledge gaps currently too large
0.05–0.08
0.004–0.01
0.01–0.02

0.16–0.25
0.01–0.03
0.03–0.05

Knowledge gaps currently too large
0.01–0.02

0.05–0.29

Knowledge gaps currently too large
0.32–0.89

0.50–1.38(3) Natural and Farmed Macroalgae
Macroalgae can also be regarded as coastal blue carbon (Krause-Jensen et al., 2018 55; Raven, 2018 56). However, theirclimate mitigation potential is currently assessed separately because of differences in their carbon processing than theestablished Blue Carbon ecosystems.
The most extensive and productive coastal vegetated ecosystems are globally formed by macroalgae, which are a diverse
group, including brown algae (e.g., kelps), red algae, and green algae. Though with large uncertainty, the areal extent ofmacroalgae is estimated to be 3.5 million km2 of coastal regions (Table 2.2). The global distribution of kelp forests isprovided in Figure 2.3.

52 Global Mangrove Watch (2018); Bunting et al. (2018) (mangroves); McOwen et al. (2018) (salt marsh cover); Bridgham et al. (2006) (salt marsh loss);
Unsworth et al. (2018) (seagrass cover); Duarte et al. (2008), Waycott et al. (2009) (seagrass loss); Krause-Jensen et al. (2016) (macroalgae cover).
53 Rosentreter, J. A., Maher, D. T., Erler, D. V., Murray, R. H. & Eyre, B. D. CH4 emissions partially offset ‘Blue Carbon’ burial in mangroves. Sci. Adv. 4, eaao4985(2018).
54 Erler, D. V. et al. Applying cavity ring-down spectroscopy for the measurement of dissolved nitrous oxide concentrations and bulk nitrogen isotopic
composition in aquatic systems: correcting for interferences and field application. Limnol. Oceanogr. Methods 13, 391–401 (2015).
55 Dorte Krause-Jensen, Paul Lavery, Oscar Serrano, Núria Marbà, Pere Masque and Carlos M. Duarte(2018). Sequestration of macroalgal carbon: the elephantin the Blue Carbon room. The Royal Society Biology Letters. Vol.14 (6)56 John Raven (2018). Blue carbon: past, present and future, with emphasis on macroalgae. The Royal Society Biology Letters. Vol.14(10).

14Figure 2.3. Global distribution of kelp forests 57
Macroalgae are mainly attached to rocks or occasionally free-floating. They lack root structures that would sequester andtrap soil carbon, which indicates that the climate mitigation value of wild macroalgae habitats is largely through the exportof organic carbon in plant biomass to sinks located in shelf sediments and in the deep ocean (Krause-Jensen and Duarte
2016 58). Similar to the case in mangroves, salt marshes, or seagrass beds, the loss of macroalgae habitats reduces carbon
sequestration but does not result in CO2 emissions to the atmosphere from sediments below the habitats. Macroalgaecarbon sequestration is estimated to be 0.64 (range 0.22–0.98) GtCO2e/year, representing 11 percent of annual global
net macroalgae primary production (Figure 2.4; Krause-Jensen and Duarte 2016 59). Recent studies also underline thelarge carbon export fluxes of macroalgae (Filbee-Dexter et al., 2018 60; Queirós et al., 2019 61; Ortega et al., 2019 62).

Figure 2.4. Macroalgae Contributions for Climate Change Mitigations 63

57 Eger, A. M. and Wernberg, T. (2022). Introduction. In Kelp Restoration Guidebook: Lessons Learned from Kelp Projects Around the World, (Eger, A. M., Layton,
C., McHugh, T. A., Gleason, M., and Eddy, N.), pp 5-9. The Nature Conservancy, Sacramento, CA, USA.
58 Krause-Jensen, D., Duarte, C (2016). Substantial role of macroalgae in marine carbon sequestration. Nature Geosci 9, 737–742.
59 Krause-Jensen, D., Duarte, C (2016). Substantial role of macroalgae in marine carbon sequestration. Nature Geosci 9, 737–742.
60 Karen Filbee-Dexter, Thomas Wernberg(2018). Rise of Turfs: A New Battlefront for Globally Declining Kelp Forests, Bio Science, Vol.68(2),64–76,
61 Ana Moura Queirós,Nicholas Stephens,Stephen Widdicombe,Karen Tait,Sophie J. McCoy,Jeroen Ingels,Saskia Rühl,Ruth Airs,Amanda Beesley,Giorgia
Carnovale,Pierre Cazenave,Sarah Dashfield,Er Hua,Mark Jones,Penelope Lindeque,Caroline L. McNeill,Joana Nunes,Helen Parry,Christine Pascoe,Claire
Widdicombe,Tim Smyth,Angus Atkinson,Dorte Krause-Jensen,Paul J. Somerfield(2019). Connected macroalgal-sediment systems: blue carbon and food websin the deep coastal ocean. Ecological Society of America Ecological Monographs. Vol89(3)62 Ortega, A., Geraldi, N.R., Alam, I. et al.(2019). Important contribution of macroalgae to oceanic carbon sequestration. Nat. Geosci. 12, 748–754
63 Krause-Jensen, D., Duarte, C. Substantial role of macroalgae in marine carbon sequestration. Nature Geosci 9, 737–742 (2016).
https://doi.org/10.1038/ngeo2790

15Overall assessment of the global change rate of macroalgae habitats is unavailable and the net area is lost; thus, kelps(brown canopy-forming macroalgae) are estimated to have experienced a global average annual loss rate of ~0.018%/year
over the past 50 years, demonstrating large geographic variability (Wernberg et al., 2019 64 ). The protection andrestoration of wild macroalgae habitats also hold potential for GHG emission mitigation, but knowledge gaps are currently
too large to estimate the potential contribution due to the unknown extent of lost macroalgal habitats that could berestored. Moreover, methods and success rates of restoration and protection measures (including sustainable harvest
methods) must be explored and reviewed.
Policy recognition of the mitigation benefits of coastal ecosystems requires quantitative information on their actual andpotential carbon uptake and storage at the local and national scales within an international framework for carbon
accounting. Proposals to apply carbon accounting to the amount of refractory (poorly soluble) dissolved organic carbon(DOC) produced by macroalgae and the amount of seafloor deposition and burial and deep-sea transport of organic
matter derived from macroalgae are underdeveloped. As a national project (March 2021–March2025), models in Japanare being developed to evaluate seafloor deposition and burial, deep-sea transport of organic carbon, and refractoryorganic matter production for natural and farmed macroalgae by function and region to evaluate CO2 absorption.
Evidence that macroalgae produce highly refractory compounds and that organic carbon may be buried in sediments ortransported to the deep sea and thus stored for thousands of years is growing (Figure 2.5). In addition to conserving wild
kelp beds, macroalgae aquaculture offers opportunities for climate change mitigation and adaptation. However,macroalgae (and phytoplankton) necessitates a different approach to those typically involved in established Blue Carbon
ecosystems because they require management of the future of their carbon production and the locations of carbon
accumulation, which may be distant from the production sites (e.g., in water column and deep water).

Figure 2.5. Carbon Flows and Macroalgal Community Metabolism 65*“NCP” indicates “net community production”; “NCC” indicates “net community calcification”; NDR indicates “net DOC release”; in the macroalgal bed,
calculated using the results of field-bag experiments 66.
Macroalgae aquaculture is inherently manageable as a mitigation measure. If linked to biofuel or biogas production, thenpotential to reduce emissions (as an alternative to fossil fuels); if also linked to carbon capture and storage, then achieving
negative emissions may be possible (net CO2 removal from the atmosphere). Full life cycle analyses are needed to assess

64 Thomas Wernberg and Karen Filbee-Dexter(2019). Missing the marine forest for the trees. Mar Ecol Prog Ser 612. 209-215
65 Watanabe, K., Yoshida, G., Hori, M., Umezawa, Y., Moki, H., & Kuwae, T. (2020). Macroalgal metabolism and lateral carbon flows can create significant carbon
sinks. Biogeosciences, 17(9), 2425-2440.
66 Biomass growth in terms of organic carbon (OC) is calculated by subtracting NDR from NCP. Biomass growth in terms of inorganic carbon (IC) is the same as
NCC. DIC and DOC flows via water exchange are estimated by mass-balance modeling. Community metabolism, biomass growth, and DOC outflow indicate thesum of macroalgal and planktonic carbon flows. Carbon fluxes are calculated in units of millimoles per square meter of the surface area of the macroalgal bed
per day. RDOCM indicates refractory DOC released by macroalgae.

16the energy efficiency of such approaches and the viability of scaling up these approaches to climatically important levels
considering associated environmental and socioeconomic implications. A different mitigation option using macroalgae
relates to their use as a dietary supplement for ruminants to suppress methane production. In vitro studies have provided
promising results. However, confidence in this approach as a mitigation option is low because its potential scale of realworld benefits has yet to be quantified.
Rather than accumulate carbon (similar to most wild algal forests), macroalgae farms found in sites over coarse sediment(coarse sand to stony soils) and sites with strong currents export carbon. Carbon accumulation and sequestration below
the farm were documented for many types of farms. Remarkably high sedimentation and carbon burial rates were foundin farms from Ningde farm (China), Seriwe and Naim Island (Indonesia), and Semporna (Malaysia) and Atlantic Sea Farms(USA).
Two-thirds of the farms demonstrated elevated organic carbon in farm soils (the rest of the farms were placed in erosive,high-energy environments). A total of 75% of farms where sedimentation rates could be resolved showed increased
sedimentation rates, accounting for 0.27 ± 0.17 g m−2 year−1 in soils under farms on average (across all farms). Meanwhile,
75% of farms, wherein carbon accumulation rates could be resolved, accumulated excess carbon compared to referenceor before farm operation. Carbon sequestration averaged 2.0 tCO2 ha−1 year−1 and increased (compared to reference or
before operation) by 1.4 tCO2 ha−1 year−1 (max 8.0 tCO2 ha−1 year−1) on average. Highest carbon accumulation rates insites that supported high carbon accumulation rates before operation emphasized the importance of selecting sink sites
to maximize macroalgae climate and carbon benefits without causing tradeoffs, such as seabed environmental
degradation.
Projections of mitigation from macroalgae farming could reach 0.05–0.29 GtCO2e/year by 2050 (Table 2.3). However,expansion rates of the industry and the production proportion that would be sequestered demonstrate uncertainties.
Scaling up macroalgae production via aquaculture offers different potential mitigation pathways.
•
Macroalgae products might replace those with a high CO2 footprint, thereby avoiding emissions (rather than directly
contributing to sequestration) in fields, such as food, feed, fertilizers, nutraceuticals, biofuels, and bioplastics(Duarte et al., 2017 67). The extent of this mitigation pathway is currently unknown.
•
Addition of macroalgae to animal feeds might lead to reduced enteric methane emission from ruminants, a potential
technology that is currently being explored and may substantially increase the mitigation potential of macroalgae.
In vitro experiments have shown that the red alga, Asparaguses taxonomies, can reduce methane emissions fromruminants by up to 99% when constituting 2% of the feed; several other species, including common ones, show apotential methane reduction of 33% to 50% (Machado et al., 2016 68). The Sea Forest team has currently been
attempting to cultivate Asparagopsis at a commercial scale as the first case in the world in Australia and New Zealand.
•
Similar to wild macroalgae, farmed macroalgae contribute to carbon sequestration through export of dissolved andparticulate carbon to oceanic carbon sinks during the production phase (Duarte et al., 2017 69).
Two scenarios were considered for estimating the mitigation potential of macroalgae farming by 2030 and 2050. The
assumptions underlying the two scenarios are presented below.
1. Macroalgae farming develops at 8.3%/year (the current rate, calculated on the basis of the increase in the farmed
and harvested production of green, red, and brown macroalgae between 2000 and 2017) (FAO 2018), 100% of
production is assumed sequestered, and farming and processing are assumed CO2 neutral. Conversion factors fromwet weight to carbon are from Duarte et al. (2017).
• Average annual yield is 1000 tons dry weight/km2 (current best practices) (World Bank 2016). Estimatedproduction by 2030 (9.4 Mt dry weight/year, equivalent to 2.3 megatons of carbon/year [MtC/ year)] and 2050
(49.3 Mt dry weight/year, equivalent to 12.2 MtC/year) would require an area of 9383 and 49,348 km2,
respectively. This finding represents 0.02% and 0.1% of the global area suitable for macroalgal aquaculture

67 Duarte CM, Wu J, Xiao X, Bruhn A and Krause-Jensen D (2017) Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation? Front. Mar.
Sci. 4:100.
68 Machado, L., Magnusson, M., Paul, N.A. et al(2016). Dose-response effects of Asparagopsis taxiformis and Oedogonium sp. on in vitro fermentation andmethane production. J Appl Phycol 28, 1443–1452.
69 Duarte CM, Wu J, Xiao X, Bruhn A and Krause-Jensen D (2017) Can Seaweed Farming Play a Role in Climate Change Mitigation and Adaptation? Front. Mar.
Sci. 4:100.

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(estimate based on suitable temperature and nutrient conditions, Froehlich et al., 2019 70).
2. Macroalgae farming develops at 14%/year from 2013 onward (rate assumed in a scenario developed by the World
Bank, 2016), 100% of production is assumed sequestered, and farming and processing are assumed to be CO2 neutral.
Conversion factors from wet weight to carbon are from Duarte et al. (2017). Average annual yield is 1000 tons dry
weight/km2 (current best practices) (World Bank 2016), leading to a production of 324 Mt dry weight/ year, which isequivalent to carbon assimilation of 80 MtC/ year by 2050.
• The scenario of a 14% annual increase in production provides an upper limit of the sequestration potential by2030 and 2050; it is further assumed that farming could proceed at this increase rate without meeting
constraints before 2050. An even high production estimate of 10 billion tons dry weight/year was recently
proposed (Lehahn et al., 2016 71), indicating that the estimated upper limit of macroalgae production is realistic.
• The assumption that 100% of the macroalgae harvest is sequestered is highly unlikely because macroalgae arefarmed for economically profitable purposes other than carbon sequestration. Energy is also required in the
production process. However, carbon sequestration through export of the “non seen production” during
farming will contribute to the sequestration potential (Duarte et al., 2017).
Recent estimates suggest that this export may constitute 60% of what is eventually harvested (Zhang and Kitazawa,
2016 72). Assuming that 25% of the macroalgae export is sequestered (Krause-Jensen et al., 2016 73).
Farms must not harm wild blue carbon ecosystems (mangroves, seagrasses, saltmarshes, and macroalgae) to maximize
the mitigation benefit of macroalgae farming. Conversely, sustainable macroalgae farming may have the advantage ofreducing the harvest of wild macroalgae.
Research on the dynamics of GHGs other than CO2 in natural macroalgal beds and farms is necessary. Recent studies haveshown that the Baltic Sea macroalgae Fucus vesiculosus releases methane equivalent to 28%–35% of the annual CO2
uptake by this macroalgae 74. Future studies should consider the process of CH4 release by macroalgae to constrain thepotential of blue carbon effectively.

(4) Mitigation in the Open Ocean(a) Ocean Fertilization 75
Current net primary production by marine phytoplankton is estimated to be 58 ± 7 GtC Cyr−1, equal to 212.86 ± 25.69
GtCO2 Cyr−1; this estimated value is similar to terrestrial primary production and around six times larger thananthropogenic emissions. However, over 99% of the biologically fixed carbon returns to the atmosphere over a range oftimescales.
The direct method of increasing marine productivity involves adding land-derived nutrients that may currently limit
primary production, particularly iron. This approach has been investigated experimentally by modeling and observing
natural system behavior. Experimental studies to date have shown that primary production can be occasionally enhancedby the addition of iron.
Difficulties arise in demonstrating the timescale of additional carbon removal and obtaining information on theconsequences of the fertilization for other marine ecosystem components, including ocean acidification and other
70 Halley E. Froehlich, Jamie C. Afflerbach, Melanie Frazier, Benjamin S. Halpern (2019). Blue Growth Potential to Mitigate Climate Change through Seaweed
Offsetting. Current Biology. Vol 29 (18),3087-3093.
71 Yoav Lehahn, Kapilkumar Nivrutti Ingle, Alexander Golberg (2016). Global potential of offshore and shallow waters macroalgal biorefineries to provide forfood, chemicals and energy: feasibility and sustainability. Algal Research, Vol17, 150-160.
72 Junbo Zhang, Daisuke Kitazawa (2016). Assessing the bio-mitigation effect of integrated multi-trophic aquaculture on marine environment by a numericalapproach. Marine Pollution Bulletin, Vol 110 (1), 484-492.
73 Krause-Jensen, D., Duarte, C (2016). Substantial role of macroalgae in marine carbon sequestration. Nature Geosci 9, 737–742.
74 Roth, F., Broman, E., Sun, X. et al. Methane emissions offset atmospheric carbon dioxide uptake in coastal macroalgae, mixed vegetation and sedimentecosystems. Nat Commun 14, 42 (2023). https://doi.org/10.1038/s41467-022-35673-9
75 Wingard, G.L., Bergstresser, S.E., Stackhouse, B.L., Jones, M.C., Marot, M.E., Hoefke, K., Daniels, A. and Keller, K. (2019). Impacts of Hurricane Irma on Florida
Bay Islands, Everglades National Park, USA. Estuaries and Coasts, 1-20., GESAMP (2019). High level review of a wide range of proposed marine geoengineering
techniques. (Boyd, P.W. and Vivian, C.M.G., eds.). (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UN Environment/UNDP/ISA Joint Group of Experts on the
Scientific Aspects of Marine Environmental Protection).
Rep. Stud. GESAMP No. 98, 144 p

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potential side effects. Modeling studies indicate that the climatic benefits could be relatively short-lived. Furthermore,
public and political acceptability for ocean fertilization is low. Ocean iron fertilization is regulated by the London Protocol,
with amendments prohibiting such an action unless constituting legitimate scientific research authorized under permit.
There are additional governance constraints for the Southern Ocean where ocean iron fertilization is theoreticallyconsidered to be most effective.
Open ocean fertilization by macronutrients (e.g., nitrate) has also been proposed, with modeled potential for gigatonscale carbon removal. Similar technical and governance considerations apply with regard to the quantification of
mitigation benefits the monitoring of potential adverse impacts and the political acceptability of large-scale deployment.
This approach would also involve high costs because of the remarkably large quantities of required nutrients.
Recent reviews of the scope for using natural processes in the open ocean for climate mitigation are provided. The
summary assessment provided herein is limited to direct and indirect biologically based approaches, consistent with thescoping of this report and the major governance constraints on the large-scale application of open ocean interventions.

(b) Increasing Upwelling
The indirect method of enhancing marine productivity uses physical devices to increase upwelling, thereby raising the
supply of a wide range of naturally occurring nutrients from deep water. This technique risks releasing additional CO2 tothe atmosphere, reducing its potential for climate mitigation. Other undesirable climatic consequences, including
disruption of regional weather patterns and long-term warming rather than cooling, may also be observed if enhanced
large-scale upwelling is deployed.
Confidence that such open ocean manipulations provide a viable mitigation measure is low due to the many technical,
environmental, and governance issues relating to marine productivity enhancement by either direct fertilization or
upwelling.

(5) Climate Change Adaptation Effects(a) Climate Change Impacts for the Ocean

Figure 2.6. Observed Regional Impacts from changes in the Ocean 76

Ocean and cryosphere changes particularly impact islands and coasts with cascading and compounding risks for both
extreme events: for example, marine heat waves, tropical and extratropical storms, associated storm surges, and heavy
precipitation; slow onset changes, such as the retreat of glaciers and ice sheets, sea ice and permafrost thawing, sea level
76 IPCC (2019). IPCC Special Report on the Ocean and Cryosphere in a Changing Climate. Cambridge University Press.

19rise, and ocean warming and acidification. The scientific analysis of the impacts was described in the above part of IPCC
SROCC in 2019, which featured each sea area as shown below (Figure 2.6). Some ocean indexes are expected to emerge
earlier than others and could therefore be used to prioritize planning and building resilience.
Low-lying islands and coasts are particularly at risk from climate-related changes to the ocean and the cryosphere,
whether urban or rural, continental or island, at any latitude and regardless of development level, which has the potential
to increase the level of loss and damage experienced by local coastal livelihoods significantly (e.g., fishing, logistics, or
tourism). For example, accelerating sea level rise will combine with storm surges, tides, and waves to generate extreme
sea level events that affect flooding, shoreline changes, and salinization of soils, groundwater, and surface waters. Sea
level rise will also combine with ocean warming to accelerate permafrost thawing in the Arctic. Ocean acidification will
combine with ocean warming and deoxygenation to impact benthic and pelagic organisms, associated ecosystems (e.g.,coral reefs, oyster beds), and top predators, with subsequent impacts on the abundance and distribution of species andthe ecosystem services benefiting human societies.
Nearly 50% of the preindustrial, natural extent of global coastal wetlands has been lost since the 19th century 77. Such a
reduction in wetlands is primarily caused by non-climatic drivers, such as alteration of drainage, agriculture development,
coastal settlement, hydrological alterations, and reductions in sediment supply. Local factors are driven by regional
processes, such as extensive coastal urbanization, human-induced sediment starvation (and implications on subsidence),
degradation of vegetated coastal ecosystems (e.g., mangroves, coral reefs, and saltmarshes), lack of long-term integrated
planning, changing consumption modes, and conflicting resource use and socioeconomic inequalities. These factors are
vehicles of increasing exposure and vulnerability at multiple scales.
Large-scale mortality events of mangroves from “natural causes” have also occurred globally since the 1960s; ~70% of
this loss has been attributed to low frequency, high-intensity weather events (such as tropical cyclones (45%)) and climatic
extremes (such as droughts, SLR variations, and heat waves). The compounding effects of heat waves, hypersalineconditions, and increased turbidity and nutrient levels associated with floods have negatively changed the composition
and biomass of co-occurring seagrass species.
Substantial evidence supports with high confidence that warming and salinization of wetlands due to SLR are causing
shifts in the distribution of plant species inland and poleward, such as mangrove encroachment into subtropical salt
marshes or seagrass meadows contraction at low latitudes. Plants with low tolerance to flooding and extreme
temperatures are particularly vulnerable and may be locally extirpated. The flooded area of salt marshes can become amudflat or be colonized by considerably tolerant, invasive species whose expansion is favored by combined effects ofwarming, rising CO2, and nutrient enrichment. The loss of vegetated coastal ecosystems causes a reduction in carbon
storage with positive feedback to the climate system. SLR and warming are expected to continue to reduce the area ofcoastal wetlands, with a projected global loss of 20%–90% by the end of the century depending on emission scenarios.
High risk of total local loss is projected under the RCP8.5 emission scenario by 2100, especially if landward migration andsediment supply are constrained by human modification of shorelines and river flows.

(b) Climate Change Adaptation Effects of Blue Carbon
The Blue Carbon ecosystem conservation and restoration activities can help the ecosystem (including local communities
and human residents) cope with changes in response to climate change and reduce damage. Consequently, this approachleads to the implementation of blue carbon ecosystem restoration as NbSs, especially to addressing the impacts of climatechange and other societal challenges. Specifically, blue carbon ecosystems provide protection from storms and sea levelrise, prevent shoreline erosion, regulate coastal water quality, provide habitat for marine life including commercially

77 Highly context-specific territorial and societal dynamics have resulted in major changes at the coast, for instance the growing concentration of people andassets in risk prone coastal areas, and the degradation of coastal ecosystem services such as coastal protection and healthy conditions for coastal fisheries andaquaculture. Local drivers of exposure and vulnerability include, for example, coastal squeeze, inadequate land use planning, changes in construction modes,
sand mining and unsustainable resource extraction, as well as loss of Indigenous Knowledge and Local Knowledge. Poor planning can combine with coastal
population growth and climate-related ocean change to create maladaptation. Betzold, C. and I. Mohamed (2016).Seawalls as a response to coastal erosion
and flooding: a case study from Grande Comore, Comoros (West Indian Ocean). Regional Environmental Change, 17 (4), 1077-1087., Ratter, B. M. W., J. Petzold
and K. M. Sinane (2016). Considering the locals: coastal construction and destruction in times of climate change on Anjouan, Comoros. Natural Resources
Forum, 40 (3), 112-126., Juhola, S., E. Glaas, B.-O. Linnér and T.-S. Neset (2016).Redefining maladaptation. Environmental Science & Policy, 55, 135-140., Magnan,
A. K. et al.(2016). Addressing the risk of maladaptation to climate change. Wiley Interdisciplinary Reviews: Climate Change, 7 (5), 646-665.

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important fish species and endangered species, and provide food security for coastal communities (often describing theseadaptation effects as “blue carbon co-benefits”).
For example, soft protection systems were found to exhibit effectiveness in reducing wave heights at 62%–79% for salt
marshes, 36% for seagrass meadows, and 31% for mangroves 78. Arguing that coral reefs can provide comparably higher
wave attenuation benefits to artificial defenses such as breakwaters, and reef defenses for reducing coastal hazards canbe enhanced cost effectively on the order of 1/10th79. If applied place specific and adequate (e.g., use of indigenous rather
than exotic species 80), then ecosystem-based measures are usually considered low-regret in that they can stabilize thecoastal vegetation and protect against coastal hazards while simultaneously enhancing the adaptive capacity of natural
ecosystems 81.
Coastal and oceanic adaptation responses are greatly complicated by the presence of competing interests (either
between user groups, communities, or nations), where considerations other than climate change need to be incorporated
into cooperation agreements and policy. The deployment of either built or natural protection systems or adopting a “waitand see” approach, is subject to the social acceptance of these approaches in communities. Similarly, the willingness tomove away from climate change impacted zones is dependent upon a range of other socioeconomic factors, such as age,access to resources, and crime. Adaptation to climate change includes a range of nonclimatic and social variables thatcomplicate implementation of adaptation plans.
In coastal communities and in most other sectors, despite consensus on the importance of cooperation in tackling climatechange, adaptation progress may be hampered by competing economic interests and worldviews, which can becompounded by limited climate change knowledge. Thus, another critical factor that limits climate change adaptation
through a blue carbon framework is the lack of awareness of communities or relatively low perceptions of this particular
benefit. For example, local communities in the Philippines and Indonesia were surveyed for blue carbon ecosystem service
awareness and results showed relatively low level of awareness 82 . Thus, improving community participation andintegrating knowledge systems (local, traditional, and scientific) is necessary to support coastal community adaptation
responses, for better co-production of knowledge, improved community awareness and better-informed, and cohesive
coastal communities. Social responses should include increasing climate change awareness and improving participatory
decision making through bottom-up approaches. Additionally, community organization for action and engagements withlocal management authorities is highly encouraged because local people actively participate in management activities
with proper information 83. Climate change adaptation capacity is shaped by historical path dependencies, local context,
and international linkages, while action is influenced by science, research partnerships, and citizen participation. Thus,
locally context-specific data to guide appropriate adaptation response should be integrated although, this remains aknowledge gap.

78 Pontee, N., S. Narayan, M. W. Beck and A. H. Hosking (2016). Nature-based solutions: lessons from around the world. Proceedings of the Institution of Civil
Engineers – Maritime Engineering, 169 (1), 29-36
79 Ferrario, F. et al.(2014). The effectiveness of coral reefs for coastal hazard risk reduction and adaptation. Nature Communications, 5, 3794,
80 Duvat, V. K. E. et al.(2016). Assessing the impacts of and resilience to Tropical Cyclone Bejisa, Reunion Island (Indian Ocean). Natural Hazards, 83 (1), 601640
81 Schoonees, T. et al. (2019). Hard Structures for Coastal Protection, Towards Greener Designs. Estuaries and Coasts, 1-12↩
82 Quevedo, J. M. D., Uchiyama, Y., Lukman, K. M., and Kohsaka, R. 2021. How blue carbon ecosystems are perceived by local communities in the Coral Triangle:
Comparative and empirical examinations in the Philippines and Indonesia. Sustainability, 13(1), 127.
83 Quevedo, J. M. D., Uchiyama, Y., & Kohsaka, R. 2021. A blue carbon ecosystems qualitative assessment applying the DPSIR framework: Local perspective ofglobal benefits and contributions. Marine Policy, 128, 104462.

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Chapter 3
Current and Future Technologies to Scale the Blue Carbon
This chapter describes technologies to measure or track, regenerate, conserve, and create blue carbon to use its products.
Areas where research and development are expected to be conducted in the future are also presented in this chapter.

(1) Technology to Measure and Track
The ability to parameterize sequestration accurately and cost-effectively from blue carbon ecosystems using standardized
methods must be improved. Relatively unknown physicochemical pathways in the blue carbon cycle, including carbonate
production and dissolution, alkalinity (carbonate and bicarbonate in seawater) export, and the exports of the blue carbon
to deep ocean sinks, must be explored but may have globally significant implications.
The area and activity of each blue carbon ecosystem must be accurately determined. Several methods to determine thearea, including satellite imagery, drones, underwater drone photography, ground truth by diving operations, andbiologging, are available. Each method has its strengths and weaknesses, and an appropriate combination is necessary.
In addition, technologies to aggregate data and perform calculations on the cloud and technologies to extract blue carbon
from images automatically using AI are necessary (Figure 3.1).

Figure 3.1. Observation technology and analytical tools to improve the parameterization of blue carbon.
The use of machine learning methods and data integration of optical and synthetic aperture radar data is increasing in
the mapping and monitoring of blue carbon (BC) ecosystems. The use of drones in combination with machine learning

22

methods is also promising for BC monitoring when applied to salt marshes 84 and seagrass beds 85. A new approach todisplaying seagrass and its surroundings on a map has also been developed by combining the cloud computing power of
Google Earth Engine, free satellite imagery, and machine learning 86. This approach has resulted in a new method to map
seagrass distribution and its changes, mapping the seagrass beds of Posidonia oceanica in the Aegean Sea, Greece, withan overall accuracy of 72% for ~2510 km2. An excellent review of remote sensing monitoring of BC ecosystems is alsoavailable 87. Remote sensing from the air can be adapted for monitoring macroalgal farming, but the development ofmethods from the sea using operating underwater robots (so-called AUVs) has also begun 88.
Visual and camera imaging by Stand-Up Paddleboard, waterborne drones, and onboard and scuba-diving are effective forground truthing, which is the field data necessary to validate remote sensing. Biologging using tiger sharks and sea turtles
can also be an effective monitoring method for some ecosystems. A recent paper reported that at least 66,000 km2 andup to 92,000 km2 of seagrass habitat is identified by utilizing recently obtained movement data from tiger sharks on the
Bahama Banks 89.
Scientific investigations are needed on slightly understood pathways, such as alkalinity transport from mangroves to theocean 90,91, transport of dissolved and suspended form carbon from seagrass and macroalgal beds 92, mangroves 93, andcultivated macroalgae to the deep sea, and understanding the interaction between carbonate sediments and BC 94 .
Tracking exported BC using environmental DNA (eDNA) in marine sediments and water samples 95 and utilizing recent
high-resolution shelf-scale current models 96 should further be developed to assess exports of macroalgae(‘‘allochthonous’’ BC) from coastal habitats to deep ocean sinks.

(2) Technology to Create
When creating BC ecosystems, cases in which reforestation is conducted by planting trees (such as mangroves) or shallow
areas that have been lost due to land reclamation or some reasons, are created by artificial materials to create macroalgal
and seagrass beds. In some cases, ecological engineering technology is used to create macroalgal beds by creating
varieties that are tolerant to high temperatures. In some cases, macroalgae is cultivated together with fish and bivalve
mollusks through integrated multitrophic aquaculture (IMTA).
Several manuals and guidelines have been published by international organizations and others on the ecological

84 Lanceman D, Sadat-Noori M, Gaston T, Drummond C and Glamore W (2022), Blue carbon ecosystem monitoring using remote sensing reveals wetland
restoration pathways. Front. Environ. Sci. 10:924221. doi: 10.3389/fenvs.2022.924221
85 Hamad, I.Y.; Staehr, P.A.U.; Rasmussen, M.B.; Sheikh, M. Drone-Based Characterization of Seagrass Habitats in the Tropical Waters of Zanzibar. Remote Sens.
2022, 14, 680. https://doi.org/10.3390/rs14030680
86 Traganos D, Aggarwal B, Poursanidis D, Topouzelis K, Chrysoulakis N, Reinartz P. Towards Global-Scale Seagrass Mapping and Monitoring Using Sentinel-2 on
Google Earth Engine: The Case Study of the Aegean and Ionian Seas. Remote Sensing. 2018; 10(8):1227. https://doi.org/10.3390/rs10081227
87 Pham TD, Xia J, Ha NT, Bui DT, Le NN, Tekeuchi W. A Review of Remote Sensing Approaches for Monitoring Blue Carbon Ecosystems: Mangroves, Seagrasses
and Salt Marshes during 2010–2018. Sensors. 2019; 19(8):1933. https://doi.org/10.3390/s19081933
88 Stenius, I. Folkesson, J. Bhat, S. Sprague, C.I. Ling, L. Özkahraman, Ö. Bore, N. Cong, Z. Severholt, J. Ljung, C. et.al. A System for Autonomous Seaweed Farm
Inspection with an Underwater Robot. Sensors 2022, 22, 5064. https://doi.org/10.3390/s22135064
89 Gallagher, A.J., Brownscombe, J.W., Alsudairy, N.A. et al. Tiger sharks support the characterization of the world’s largest seagrass ecosystem. Nat Commun
13, 6328 (2022). https://doi.org/10.1038/s41467-022-33926-1
90 Sippo, J.Z., Maher, D.T., Tait, D.R., Holloway, C., and Santos, I.R. (2016). Are mangroves drivers or buffers of coastal acidification? Insights from alkalinity anddissolved inorganic carbon export estimates across a latitudinal transect. Glob. Biogeochem. Cycles 30, 753–766. https://doi.org/10.1002/2015GB005324.
91 Raghab R., Miyajima, T., Watanabe, A., et al. (2021). Dissolved and particulate carbon export from a tropical mangrove-dominated riverine system. Limnol.
Oceanogr. 66(11) 3944-3962. https://doi.org/10.1002/lno.11934.
92 Ortega, A., Geraldi, N.R., and Duarte, C.M. (2020). Environmental DNA identifies marine macrophyte contributions to Blue Carbon sediments. Limnol.
Oceanogr. 65, 3139–3149. https://doi.org/10.1002/lno.11579.
93 Miyajima T., Hamaguchi M., Nakamura T., Katayama H. and Hori M. (2022) Export and dispersal of coastal macrophyte-derived organic matter to deep
offshore sediment around the Tokara and Yaeyama Islands, southwest Japan: Evaluation using quantitative DNA probing techniques. Bulletin of the Geological
Survey of Japan, vol. 73(5/6), 313–321.
94 Macreadie, P.I., Serrano, O., Maher, D.T., Duarte, C.M., and Beardall, J. (2017). Addressing calcium carbonate cycling in blue carbon accounting. Limnology
Oceanography Lett. 2, 195-201.https://doi.org/10.1002/lol2.10052.
95 Geraldi, N.R., Ortega, A., Serrano, O., Macreadie, P.I., Lovelock, C.E., Krause-Jensen, D., Kennedy, H., Lavery, P.S., Pace, M.L., Kaal, J., and Duarte, C.M. (2019).
Fingerprinting blue carbon: rationale and tools to determine the source of organic carbon in marine depositional environments. Front. Mar. Sci. 6, Unsp 263.
https://doi.org/10.3389/fmars.2019.00263.
96 Liu, X., Dunne, J. P., Stock, C. A., Harrison, M. J., Adcroft, A., & Resplandy, L. (2019). Simulating Water Residence Time in the Coastal Ocean: A Global
Perspective. Geophysical Research Letters, 46, 13,910–13,919. https://doi.org/10.1029/2019GL085097

23

restoration of mangrove forests 97. We will defer to these publications for details. However, the following general rules
are presented.
• Abiotic parameters, such as hydrodynamic, topographic, and physicochemical conditions of the target area, should
be understood.
• Natural colonization should be prioritized by restoring favorable hydrological conditions.
• Mangrove planting should be conducted in a manner acceptable to the local community only when naturalcolonization is impossible.
• Transplantation will be performed by selecting appropriate species to the abiotic conditions within the intertidal
zone.
• Appropriate post-planting monitoring should be conducted.
Similarly, manuals on restoration have been published for seagrass beds98, salt marshes 99, and kelp forests 100. As with
mangrove forests, the guiding principle is to first identify the factors or abiotic parameters surrounding the degradedseagrass beds responsible for the degradation if the factors can be eliminated and addressed to promote natural recovery
and only if natural recovery cannot be achieved even after addressing the factors to plant appropriate seagrass or marsh
species actively. Preliminary identification of factors will also be important in establishing project baselines.
Japan has many projects to restore macroalgal beds using artificial structures. Activities to restore kelp beds are currently
conducted in the coastal areas of Hokkaido, where underwater kelp forests have become barren by herbivores, using
steelmaking slag 101. A project is also underway to measure the creation of macroalgal beds by attaching macroalgae towave-dissipating blocks while reducing manufacturing costs by 20% and CO2 emissions by 43% using copper slag mortar
for the blocks. In sea areas where three-dimensionality or rugosity has been lost and macroalgal restoration has notprogressed, restoring macroalgal beds or kelp forests using artificial reefs and structures while considering theenvironmental risks may be necessary.
Biotechnology is also being developed for the restoration of underwater forests. One example is the development oftechnology for perennial macroalgae, such as Ecklonia cava and Eisenia bicyclis, in which mother algae are collected
before the disappearance of macroalgal beds and “free-living gametophyte technology” is used to enable seedling
production of large macroalgae at any time. In Japan, efforts are underway to restore underwater forests by combining
such seedling production with artificial reefs.
Macroalgal cultivation methods that utilize man-made structures used for other purposes are also being considered. For
example, the use of floating or bottom-set offshore wind farm facilities for macroalgal cultivation purposes has been
proposed 102 . Moreover, IMTA, a kind of aquaculture that combines primary producers, primary consumers, andsecondary consumers, is attracting attention (Figure 3.2). For example, research is also underway to enable bivalves, sea
cucumbers, and macroalgae to utilize nutrients from salmon 103, sea bream, and yellowtail aquacultures, respectively.
Studies indicated that commercializing IMTA faces challenges; however, the inclusion of climate change mitigation as an
option can add values and is worth considering.

97 Mangrove Restoration: the key elements to be considered in any restoration project. Technical guide, Pôle-relais zones humides tropicales, 2018; Claudia
Teutli-Hernández, Jorge A. Herrera-Silveira, Diana J. Cisneros-de la
Cruz, Daniel Arceo-Carranza, Andrés Canul-Cabrera, Pedro Javier Robles-Toral, Oscar J. Pérez-Martínez, Daniela Sierra-Oramas, Karla Zenteno, Heimi G. UsBalam,
Eunice Pech-Poot, Xavier Chiappa-Carrara, Francisco A. Comín. 2021. Manual for the ecological restoration of mangroves in the Mesoamerican Reef Systemand the Wider Caribbean. Integrated Ridge-to-Reef Management of the Mesoamerican Reef Ecoregion Project - MAR2R, UNEP-Cartagena Convention,
Mesoamerican Reef Fund. Guatemala City, Guatemala.
98 Gamble C., Debney, A., Glover, A., Bertelli, C., Green, B., Hendy, I., Lilley, R., Nuuttila, H., Potouroglou,M., Ragazzola, F., Unsworth, R. and Preston, J, (eds)(2021). Seagrass Restoration Handbook. Zoological Society of London, UK., London, UK Region; UNEP-Nairobi Convention/ WIOMSA (2020). Guidelines for
Seagrass Ecosystem Restoration in the Western Indian Ocean Region. UNEP, Nairobi, 63 pp.
99 Hudson, R., Kenworthy, J. and Best, M. (eds) (2021). Saltmarsh Restoration Handbook: UK and Ireland. Environment Agency, Bristol, UK.
100 Eger, A. M., Layton, C., McHugh, T. A, Gleason, M., and Eddy, N. (2022). Kelp Restoration Guidebook: Lessons Learned from Kelp Projects Around the World.
The Nature Conservancy, Arlington, VA, USA.; Ward, M., McHugh, T.A., Elsmore, et al. (2022) Restoration of North Coast Bull Kelp Forests: A Partnership BasedApproach. Reef Check Foundation, Marina del Rey, CA.
101 Steelmaking slag is a byproduct of the reduction and refining process that produces steel from iron ore, in which silica (SiO2) and other non-iron components
are melted and combined with lime (CaO).
102 Stelzenmüller, V., Gimpel, A., Gopnik, M., Gee, K. (2017). Aquaculture Site-Selection and Marine Spatial Planning: The Roles of GIS-Based Tools and Models.
In: Buck, B., Langan, R. (eds) Aquaculture Perspective of Multi-Use Sites in the Open Ocean. Springer, Cham.
103 Fossberg J, Forbord S, Broch OJ, Malzahn AM, Jansen H, Handå A, Førde H, Bergvik M, Fleddum AL, Skjermo J and Olsen Y (2018) The Potential for Upscaling
Kelp (Saccharina latissima) Cultivation in Salmon-Driven Integrated Multi-Trophic Aquaculture (IMTA). Front. Mar. Sci. 5:418.

24

Figure 3.2. Conceptual model for an Integrated Multitrophic Aquaculture (IMTA) System 104
The search for precocious macroalgae and their artificial cultivation is also currently underway. In Sagami Bay, Japan,
research to find a fast-growing, precocious species of Ecklonia cava, which normally takes a year and a half to grow, isongoing; this species has been found to grow in approximately six months, which is one-third the normal time. Artificial
cultivation technology for this macroalgae is also under development 105. Solutions are also being considered for thepromotion of blue infrastructure, which can lead to the creation of BC ecosystems, as well as integrated land and sea
approaches to promote eco-engineering or NbSs (Box 1).

104 https://www.dfo-mpo.gc.ca/aquaculture/sci-res/imta-amti/index-eng.htm (accessed on January 8, 2023)
105 https://www.pref.kanagawa.jp/docs/kb2/prs/r5306312kajime.html (accessed on January 8, 2023)

25

Box 1. Eco-engineering and blue infrastructure
The application of ecological engineering principles to build coastal defense structures that “mimic” natural coastal
areas, including dynamic coastal landforms (such as beaches, barrier islands, and dunes) and coastal vegetation (suchas mangroves, seagrasses, dune vegetation, saltmarshes, and kelp forests), continues to increase. Steven et al.
(2020 106) illustrate the co-benefits of implementing blue infrastructure and the advantages and disadvantages of eachform of infrastructure (Figure 3.3, Table 3.1).

Figure 3.3. Benefits of Implementing Blue Infrastructure 107
Kuwae and Crocks (2020) suggested the implementation of green and gray 108 hybrid infrastructure to add
multifunctionality to coastal infrastructure. Reducing costs and appropriately quantifying green infrastructure
functions and monetizing the co-benefits, which currently have underestimated value because quantifying
multifunctionality is difficult, is necessary to improve cost-effectiveness. In addition, practitioners must
quantitatively confirm that cost-effectiveness is better with green infrastructure than without it in relation to realprojects and explain the quantitative benefits of green infrastructure to doubtful stakeholders regarding its efficacy
and profitability.

106 Kelleway, J. J., Serrano, O., Baldock, J. A., Burgess, R., Cannard, T., Lavery, P. S., Lovelock, C. E., Macreadie, P. I., Masqué, P., Newnham, M., Saintilan, N. andSteven, A. D. L.(2020).A national approach to greenhouse gas abatement through blue carbon management, Global Environmental Change, Vol. 63.
107 Thiele, T., G. Alleng, A. Biermann, E. Corwin, S. Crooks, P. Fieldhouse, D. Herr, N. Matthews, N. Roth, A. Shrivastava, M. von Unger and J. Zeitlberger (2020).
Blue Infrastructure Finance: A New Approach, Integrating Nature-based Solutions for Coastal Resilience. Gland, Switzerland: International Union forConservation of Nature
108 gray means the traditional coastal infrastructure typically built with concrete and steel

26

Table 3.1. Eco-Engineering advantages and disadvantages compared with traditional coastal infrastructures 109
Traditional
CoastalInfrastructure
typically built
withconcreate &steel

Advantages
Significant expertise on the design and building of suchapproaches at large scales exists
Decades of experience with implementation
Excellent understanding of the function of these approaches
and the level of protection provided by different types ofstructures built to specific engineering standards
Infrastructure can withstand a storm event as soon as it isconstructed

Naturaland Hybrid
Infrastructure

Capitalizes on best characteristics of built and natural
Allows for innovation in designing coastal protection systems
Provides some co-benefits in addition to coastal protection
Provides a higher level of confidence than natural
approaches alone
Possible use in areas with minimal space to implement
natural approaches alone
Balances conservation with development

Ecosystem
Restoration

Provides many co-benefits in addition to coastal protection,
including fishery habitat, water quality improvements, andcarbon sequestration and storage,
and offers these benefits to coastal communities all thetime, not only during storm events
Ecosystem grows strong with time as established
Demonstrates self-recover potential after a storm or otherdisturbance events
Maintain pace with sea level rise
Cheap to construct
Increased CO2 storage capacity in created, maintained, or
restored ecosystems; reduction of urban heatwave islandeffect; improvement in water quality
Can enhance tourism, recreational, and local employment
opportunities included in establishment and maintenance
Enhances the natural environment and implicit value
Saves raw materials and improves public health

Disadvantages
Does not adapt with changing conditions, such as weakeningof sea level rise with time, and has a built-in lifetime
Disrupt longshore coastal sediment transport and cause
downdrift coastal erosion
Cause coastal habitat loss and have negative impacts on theecosystem services provided by nearby coastal ecosystems
May sustain additional damage during small storm events
Only provides storm protection benefits when a storm isapproaching; no co-benefits accrue in good weather
Needs continuous monitoring and regular maintenance
Barrier to dispersal and movement of fauna and flora,
resulting in loss of ecosystem connections
Data on the current performance of these systems are limited
Does not provide the same benefits given by natural systems
Additional research is needed to design the best hybrid
systems
Growing but limited expertise in the coastal planning anddevelopment community on which approaches to use
Hybrid systems can still have some negative impacts on
species diversity due to their built part
Uncertainty in cost-effectiveness and long-term performance
Permission for hybrid projects can be a more difficult process
than for built projects
Response to native species colonization is unpredictable
Development of best practices for restoring ecosystems
according to a set of starting criteria is needed
Provides variable levels of coastal protection (nonlinearity ofthe provisioning of coastal protection benefits) depending on
the ecosystem, geography, and the type and severity of storm
events; additional research is needed to understand effectivel
the estimation or prediction of the provided coastal protectio
Establishing restored ecosystems can take a long time;
therefore, the natural systems can provide the necessary leveof coastal protection
Possibly requires a substantial amount of space to implement
natural approaches (such as ecosystem restoration orprotection of existing ecosystems), which may be impossible ihighly urban or industrial contexts
Uncertainty in cost-effectiveness and long-term performance
Permitting for natural projects can be a more difficult process
than for built projects
Uncertainty over responsibility for ownership andmaintenance
Uncertainty in assessing levels of risk for insurance cover andpremiums for coastal assets(3) Technology to Protect
The description of technologies to protect BC ecosystems will focus on macroalgal beds, wherein feeding damage is amajor problem. Seagrass beds are also occasionally observed to be damaged by fish and sea turtles, and the samemeasures may be required as for macroalgal beds.
Various factors that contribute to the decline of macroalgal beds, including feeding damage by fish and sea urchins (Figure3.4), deterioration of water quality, and increments in water temperature, are available. Considering measures for thedeterioration of water quality and rise in water temperature, such as the aforementioned land-sea integrated ecoengineering and adaptation through seedling production, is necessary. By contrast, for sea urchins in particular, various
measures have been attempted with some success. Macroalgal feeding damage by sea urchins is widespread worldwide,
and its countermeasures include physical culling, chemical culling, exclusion, and predator protection 110.
109 Thiele, T., G. Alleng, A. Biermann, E. Corwin, S. Crooks, P. Fieldhouse, D. Herr, N. Matthews, N. Roth, A. Shrivastava, M. von Unger and J. Zeitlberger (2020).
Blue Infrastructure Finance: A New Approach, Integrating Nature-based Solutions for Coastal Resilience. Gland, Switzerland: International Union forConservation of Nature
110 See supra note 10027

Figure 3.4. Typical herbivores: (a) Mesocentrotus nudus, (b) Diadema setosum, (c) Siganus fuscescens,and (d) Calotomus japonicus. Photos are taken from the “Isoyake taisaku guidelines (the sea
desertification control guidelines) 111.”
In physical culling, sea urchins are destroyed underwater by scuba or free diving using a variety of tools. In chemicalculling, quicklime is applied to seawater, creating a strong base that destroys the sea urchins. Exclusion removes
herbivores from the macroalgal beds, and the removed herbivores may be stocked and raised elsewhere, such as inmarine areas or in land-based facilities. Predator protection is a way of using natural processes to protect predators ofherbivores, such as fish, lobsters, and sea star, to exert top-down controls. In many cases, such predators have been
depleted by human harvest. Therefore, this approach will be effective through the establishment of marine protectedareas or reserves.
Each method has its strengths and weaknesses considering labor, cost, temporal and spatial range of effectiveness,environmental side effects, and social acceptability.

(4) Technology to Use
Mangrove wood is used for firewood, charcoal, and poles for building materials in Southeast Asia, Africa, and SouthAmerica, respectively. In Malaysia, mangroves are used for poles and charcoal through the management of separate
conservation and utilize areas on a 30-year rotation; thus, it is recognized that carbon neutrality can be achieved throughsilvicultural activities 112. Industrial use of seagrasses and salt marsh plants is limited. Examples of seagrass used as organic
fertilizer are available. Macroalgae have a variety of industrial uses and have potential for further development.
Macroalgal aquaculture offers significant potential for developing low-carbon alternatives for food, feed, and many otherapplications. Macroalgae are not only utilized as food but also provide benefits, such as climate change action, foodsecurity, health and welfare, and clean energy, through their use as feed, drug discovery, and fiber (Figure 3.5).

111 https://www.jfa.maff.go.jp/j/gyoko_gyozyo/g_gideline/attach/pdf/index-34.pdf (in Japanese)
112 Wolswijk, G., Barrios Trullols, A., Hugé, J., Otero, V. (2022) Satyanarayana, B.; Lucas, R.; Dahdouh-Guebas, F. Can Mangrove Silviculture Be Carbon Neutral?
Remote Sens. 2022, 14, 2920. https://doi.org/10.3390/rs14122920

28

Figure 3.5. Various ecosystem services and benefits of macroalgae utilization 113
Japan has a long history of using macroalgae since ancient times. For example, the Taiho Ritsuryo, a legal system enacted
in 701, mentioned that red seaweed nori and other macroalgae were paid to the Imperial Court as a tax. In 720, themacroalgae Sargassum was mentioned in the “Nihon shoki,” a Japanese Chronicle or a history book. In the oldest
anthology of Japanese poetry, the Manyoshu, which was compiled in 759, mentioned macroalgae in more than 100 outof 4500 poems in total.
Most farmed macroalgae are currently used for human consumption (90% of production), either directly or as additives.
The latter are mainly hydrocolloids, such as agar, alginates, and carrageenans, which are used as viscosity modifiers in thefood and pharmaceutical industries 114. Macroalgae are an essential part of the human diet, providing macro and micro
nutritional elements, antioxidants, fiber, and healthy fatty acids that contribute to reducing the risk of various diseases 115.
Food use alone would have to increase to 150 MtFW at present and 187 MtFW in 2050 of macroalgal production(assuming populations of 7.8 and 9.7 billion, respectively) to bring the world population’s consumption of macroalgae inline with that of the current Japanese population (5.3 gDW d−1). Future demand for macroalgal products would be evenhigh if macroalgal hydrocolloids used in the food industry, which currently account for over 54% of global macroalgal
production, are included. Regular monitoring of toxic elements in macroalgae is necessary because they can accumulate
toxic elements from the environment 116. This practice is required for all foods.
Macroalgae provide an opportunity to produce sustainable, nonherbivorous forages for farmed animals. Arguably,
replacing fish oil and meal in animal diets with seaweed aquaculture products in feeds is essential for the developmentof sustainable animal aquaculture on the scale needed to feed a growing population sustainably. The use of somemacroalgae in fish diets has positive effects on fish growth and immune systems. However, the formulation of fish dietsfrom macroalgae (either directly or indirectly using them as small invertebrate food and as feed) has not been
implemented at any scale and remains an opportunity for the future. Realizing this opportunity will require considerable
research and development (R&D) to optimize macroalgae as a substitute for fish meal and oil.
Macroalgae has also traditionally been used as a supplement to livestock feed in coastal areas, and this practice iscurrently gaining renewed attention. Inclusion of macroalga in livestock diets may contribute to the protein and energy
requirements of livestock, provide beneficial bioactive compounds that may improve the production and health of
113 Duarte, C.M., Bruhn, A. & Krause-Jensen, D. A seaweed aquaculture imperative to meet global sustainability targets. Nat Sustain 5, 185–193 (2022).
https://doi.org/10.1038/s41893-021-00773-9
114 Mazarrasa, I., Olsen, Y. S., Mayol, E., Marbà, N. & Duarte, C. M. Rapid growth of seaweed biotechnology provides opportunities for developing nations. Nat.
Biotechnol. 31, 591–592 (2013).
115 Holdt, S. L. & Kraan, S. Bioactive compounds in seaweed: functional food applications and legislation. J. Appl. Phycol. 23, 543–597 (2011).
116 http://extwprlegs1.fao.org/docs/pdf/eri42405.pdf

29

monogastric and ruminant livestock 117, and contribute to a significant reduction in methane emissions from ruminants 118.
The amount of Sargassum (mainly two species, Sargassum natans and Sargassum fluitans) drifting ashore in the
Caribbean and west African region has dramatically increased, adversely affecting the marine environment, the fishingand tourism industry, and the health of the local population. Together with the government and local authorities,
programs to collect and remove drifting Sargassum have been initiated with the support of FAO 119 to develop policies,
standards, and incentives. Simultaneously, FAO is promoting the repurpose, commercial use, and creation of employment
and income through the development of guidelines for the use of Sargassum. Moreover, Sargassum is already currently
used to make bricks, shoe soles, soaps, plant stimulants, and paper, and its conversion to renewable energy, bioplastics,
and compost is considered. Isolated compounds are known to exhibit a variety of biological activities, such as analgesic,
anti-inflammatory, antioxidant, anti-tumor, anti-bacterial, and anti-viral, and are expected to be utilized in the medical
field. For example, antioxidants in Sargassum fluitans are effective in inhibiting liver cirrhosis 120.
The development of technology to utilize macroalgae (especially kelp) for carbon capture and sequestration in the ocean
is also currently considered. This technology can be used as a CO2 removal technology (CDR) by efficiently increasing thenumber of macroalgae, especially kelps, through photosynthesis and transporting CO2 from the ocean surface to the deepsea or into sediments 121. Some companies are actually conducting demonstrations of this technology. The keys to future
large-scale applications of this technology involve the following: potential increase in amount of carbon absorbed bymacroalgae compared to that of carbon already fixed by phytoplankton, possibility of reducing the cost to approximately$100 per metric ton, possibility of coordinating with other industries when occupying ocean areas on a large scale, andpotential detrimental effect on the environment in the areas where the biomass can be transported and stored.
Environmental assessment in lifecycles should also be considered for the industrial use of macroalgae farming (Box 2).

117 Makkar, H. P. S. et al. Seaweeds for livestock diets(2016). a review. Anim. Feed Sci. Technol. 212, 1–17.
118 Kinley, R. D. et al(2020). Mitigating the carbon footprint and improving productivity of ruminant livestock agriculture using a red seaweed. J. Clean. Prod.
259, 120836.
119 https://www.fao.org/fao-stories/article/en/c/1617549/ (accessed on January 8, 2023)
120 Quintal-Novelo C, Rangel-Méndez J, Ortiz-Tello Á, Graniel-Sabido M, Pérez-Cabeza de Vaca R, Moo-Puc R. A Sargassum fluitans Borgesen Ethanol Extract
Exhibits a Hepatoprotective Effect In Vivo in Acute and Chronic Liver Damage Models. Biomed Res Int. 2018 Dec 20;2018:6921845. doi: 10.1155/2018/6921845.
PMID: 30671467; PMCID: PMC6317085.
121 National Academies of Sciences, Engineering, and Medicine. 2022. A Research Strategy for Ocean-based Carbon Dioxide Removal and Sequestration.
Washington, DC: The National Academies Press. https://doi.org/10.17226/26278.

30

Box 2. Life cycle environmental impacts of macroalgal farming (plastic ropes, CO2 release during drying) (van Oirschot et al., 2017) 122

LCA is a well-established tool to clarify the environmental performance of product (and production) systems byquantifying their cradle-to-grave (or gate) contribution to a range of impact categories. Some LCA studies have been
conducted with a focus on speciﬁc aspects of macroalgae supply chains (for instance, wild harvests and valorization
strategies, photobioreactor cultivation and oil extraction, macroalgae bioreﬁnery, and production of biofuels from
cultivated macroalgae biomass).
Large-scale commercial macroalgae cultivation has not yet taken place in Europe; thus, the possible design of theinfrastructure and the drying subsystems are relevant outcomes of this exploratory LCA. The drying process provides
a large contribution to all impact categories, with the exception of human toxicity and fresh water ecotoxicity.
The possible design of the macroalgae cultivation infrastructure subsystem, more importantly of their permanent
infrastructure in the marine environment, is therefore ﬁrst comprehensively described. The results for the biomass
and proteins yields are then presented, followed by a description of the drying process.
It particularly dominates ozone layer depletion due to emissions of methane and ethane compounds from the burningand reﬁning of light fuel oil for production of heat. Other dominated impact categories include abiotic depletion,
climate change, photochemical oxidation, and acidiﬁcation.
The majority of nonrenewable CED also is attributed to the drying process. Considering the drying process, the relative
contribution toward impacts notably remains exactly the same regardless of the single or dual layer conﬁguration.

Figure 3.6. Dried macroalgae production system 123
The stack diagram shows the relative contributions of each infrastructural component for the single and dual layer
conﬁgurations. The chains provide the highest contribution, followed by the ropes, anchors, buoys, and strip
strengtheners.

122 Roel van Oirschota, JeanBaptiste E. Thomasc,, Fredrik Gröndahlc, Karen P.J. Fortuina, Willem Brandenburgd, José Pottinga,b,e (2017).Explorativeenvironmental life cycle assessment for system design of macroalgae cultivation and drying.
123 Roel van Oirschota, JeanBaptiste E. Thomasc,, Fredrik Gröndahlc, Karen P.J. Fortuina, Willem Brandenburgd, José Pottinga,b,e (2017).Explorativeenvironmental life cycle assessment for system design of macroalgae cultivation and drying.

31

Table 3.2. Eco Invent process applied for calculating environmental outputs of the reference dried macroalgae
production systems.
Economic
inputsused
Seeding
lines

Life

1
Year

Polypropylene, 2 mm ø,
0.0014 kg/m

Cultivati
on andinfrastru
cture
rope
Chains

5
Years

20
Years

Anchors

Small
buoys

Large
markerbuoys
Strip
strengtheners

Transp
ort

Therm
al
drying
of
macro
algae
biomas
s

n/a

Input
characteristi
cs

Source of
input
InformationAuthormeasurement

Quantity of input used
Single layer
Dual layer
0.00021 ton/
100 m oflongline/y

0.00021
ton/100 oflongline/yPolypropylene, 22 mm
ø,0.22 kg/m

TouwfabriekLangman
BV

0.030 ton/100
m oflongline/5 y

Chromium
steel, 19mm ø, 8.3kg/m

Authorcalculation

Concrete,rectangular
block, 1000kg
Polyvinyl
chloride,
0.31 mø, 1.2kg/buoy
Polyvinyl
chloride,
0.59 m ø,
4.1 kg/buoy
Polyvinyl
chloride,
1.98 kg perrod

5 × 20 km
returntrips fordelivery of
seedinglines andmonitoring
1× loadedbarge withharvest 10
km85%
moisturecontent of
S. latissima
83%
moisturecontent atstart ofdrying22%
moisturecontent at
end ofdryingEco Invent v3.0 processapplied to calculate
environmental outputs

Single layer

Dual
layer

0.028 ton/100
m oflongline/5 y= 0.016
ton/
tonprotein/
20y= 0.46 ton/
tonprotein/
20 y= 0.022
ton/
tonprotei
n/20 y= 0.58ton/
tonprotei
n/20 y0.048 ton/100
m oflongline/20 y

0.024 ton/100
m oflongline/20 y= 0.18 ton/
tonprotein/
20 y= 0.12ton/
tonprotei
n/20 yAuthorassumption2.033 ton/100
m oflongline/20 y

1.017 ton/100
m oflongline/20 yt = 7.9
ton/tonprot
ein/20 y

ChandelryWorld Ltd.

0.011 ton/100
m oflongline/20 y

0.0055
ton/100 m oflongline/20 y= 0.043
ton/
tonprotein/
20 y

= 5.3
ton/
tonprotei
n/20 y= 0.028
ton /tonprotei
n/20 yAuthorcalculation

0.054 ton/100
m oflongline/20 y

0.054 ton/100
m oflongline/20 y= 0.021ton/
tonprotein/
20 y= 0.028
ton/
tonprotei
n/20 y“Disposal, polyvinyl chloride,
0.2% water, to municipal
incineration/CH”

AuthorcalculationValidatedby pilotresearche
rs
Seafarm246
tkm/100 moflongline/20
y138
tkm/100 moflongline/20
y= 955
tkm/tonprotein/2
0y= 951
tkm/tonprotein/
20 yBarge production,
operation & maintenance:
at “Transport, barge/RER”

Schiener
et al.
Authorassumption
Scogganet al.

15 tons/100
m oflongline/20
y (ofevaporated
water)

11 tons/100
m oflongline/20
y (ofevaporated
water)= 59 tons/
tonprotein/20 y (ofevaporated water)

= 59
tons/
tonprot
ein/20 y(ofevaporatedwater)“Maize drying/CH”“Fleece, polyethylene
terephthalate/RER, at plant/
RER,” adjusted through thefollowing: (a) replacing
production of polyethylene
granulate by polypropylene
granulate; (b) adding apolypropylene end of life
incineration scenario
Chain manufacturing: “Productmanufacturing, average metal
working/kg/RER”
Steel production: 55.5%
recycled “Steel, electric,
chromium steel 18/8, atplant/RER U” and 44.5% virgin“Steel, converter, chromium
steel 18/8, at plant/ RER U”
based on scrap average inEuropean steel“Concrete block, atplant/kg/DE”“Polyvinyl chloride, granulate,
at plant/RER” PVC “Blowmolding/RER” for manufactureof buoys and strip
strengtheners

The sensitivity analysis of the total environmental impacts of dried macroalgae production systems for the single
layer cultivation conﬁguration.

32

Figure 3.7. Impact Analysis of the Environment Effects
The impacts of both reference systems are represented by the “0” on the x-axis, the other % shows the inﬂuenceof changing input values compared to the reference system for rope diameter (blue), rope replacement frequency(red), chain diameter (green), infrastructure replacement frequency (purple), biomass yield (emerald blue), water
loss during harvest (orange), water content of outgoing biomass (gray), and the speciﬁc moisture extraction rate
(SMER) of the biomass dryer (pink).

33

Chapter 4
Policy and Institutional Requirements
Large-scale promotion of BC will require a place in the nationally determined contributions (NDC) of the Paris Agreement
and inclusion in the inventories reported by each country to the UNFCCC. Consideration must also be given to meeting
the requirements for promoting high-quality carbon credits. In addition, when large-scale macroalgal aquaculture isdeveloped, new considerations for treatment under existing international conventions and environmental impact
assessments are reasonable. This chapter explains the aforementioned points.

(1) Blue Carbon and Nationally Determined Contribution (“NDC”) and National GHG inventoriesA) General
Mangrove, salt marsh, and seagrass habitats are widely recognized as BC ecosystems with mitigation potential. More than150 countries have at least one of these ecosystems; 71 countries have all three and 74 countries mention such coastal
wetlands in their NDCs to the Paris Agreement. However, the incorporation of BC into NDC reveal significant differencesin the situation in each country (Table 4.1). Gallo et al. (2017)124 reported that 27 countries include BC in their NDCs.
Table 4.1. Status of NDCs and inventories on wetland guidelines in major countries 125
Countries
Australia and USA
Antigua and Barbuda, Bahrain, UAE,
and the Philippines
Guinea, Bahama, Angola, Burundi,
Haiti, and Senegal
Bangladesh
Suriname, Sri Lanka, and El Salvador
IcelandHandling of Blue Carbon in NDCs/Inventory Calculation Status
Included in the numerical targets of the NDC. Calculated BC in the inventory based on 2006
and wetland guidelines.
Referencing to sinks by BC but not yet reflected in the numerical targets and not yet
calculated in the inventory.
They include forests as well as mangroves in their mitigation measures (Angola also includes
wetlands). However, the calculations are based on the 1996 guidelines, and soil is excluded
from the calculations (Senegal uses the 2006 guidelines but soil is excluded from thecalculations). Therefore, the numerical targets do not yet reflect this phenomenon.
Forests, including mangroves, are involved in the mitigation measures. However, the entire
LULUCF sector is not included or reflected in the numerical targets.
Forests, including mangroves, are included in the mitigation measures but are not a GHG
emission reduction type target.
The decision to exclude them in the numerical targets of the NDC is made. Wetland
restoration is included as a mitigation measure and refers to the restoration of peatlandfrom degradation; thus, it should not be interpreted as a blue carbon target.

The following is a brief examination on the situation in several countries with some background information.

B) Australia
Australia ranks second in the world in seagrass beds (52,051 km2), mangrove forests (9,780 km2), and salt marshes (13,259
km2), making it a major “BC country.” The establishment of the International Partnership for Blue Carbon, which was
spearheaded by the Australian government during COP21 in 2015 during the adoption of the Paris Agreement, is believed
to reflect this BC potential and their political will. Australia is also one of the few countries in the world that has
incorporated BC into its National GHG inventory using the IPCC wetland guidelines (2013). Australia reports net emissions
associated with mangrove forest harvesting and regeneration, salt marsh conversion, and seagrass dredging.
Commonwealth Scientific and Industrial Research Organization (CSIRO) (2020)126 drew 4 strategies and 17 actions to
reframe policy debates on biodiversity conservation, climate change adaptation and mitigation, and sustainable use ofnatural resources to address conflicts and tradeoffs associated with the use and management of ecosystem services andinvest in blue infrastructure and ocean finance (Table 4.2).

124 Gallo, N. D., D. G. Victor, and L. A. Levin (2017). Ocean commitments under the Paris Agreement. Nature Climate Change 7(11):833-838.
125 Based on Mai Fujii and Atsushi Sato (2020).Current Status and Issues Related to "Blue Carbon" under the United Nations Framework Convention on Climate
Change. Ocean Policy Studies. No.14.
126 Steven, A.D.L., Appeaning Addo, K., Llewellyn, G., Vu, T.C. et al. (2020). Coastal Development: Resilience, Restoration, and Infrastructure Requirements.
Washington, DC, World Resources Institute.

34

In January 2022, the Australian government announced tidal reinstatement as the first methodology for the Blue Carbon
Project under the emissions reduction fund (ERF) 127 through the accumulation of study results by CSIRO and otherorganizations. The ERF of Australia allows earning of Australian Carbon Credit Units (ACCUs) by projects that remove ormodify tidal flow restriction mechanisms and introduce tidal flow to an area of land. This condition results in the rewettingof fully or partially drained coastal wetland ecosystems and the conversion of freshwater wetlands to brackish or saline
wetlands 128. This approach will result in the acquisition of ACCUs for the restoration of coastal wetland ecosystems due
to project activities. The project can contribute to carbon emission control through three components: carbon
sequestration in soil, carbon fixation in above- and below-ground biomass, and emissions avoided through theintroduction of tidal currents.
Table 4.2 CSIRO’s 4 Strategies and 17 Actions of CSIRO regarding climate action and biodiversity conservation
1
2

3

4

Protect: Protection strategies use regulations and area-based management to designate where and how much of specified activities
can and cannot occur in coastal environments and in the adjacent catchment and legislate areas for conservation, such as marine
protected areas (MPAs) or implement area, habitat, and species-specific conservation plans.
Mitigate: Mitigation strategies aim to reduce local stressors caused by human action through the use of technology, regulation, andthe promotion of stewardship to minimize the introduction of pollutants and the overexploitation of resources or activities that willotherwise harm coastal environments.
Adapt: Adaptation strategies explicitly consider the coastal social–ecological system and are implicitly related to resilience; adaptation
leads to resilience, which is a property needed for having the capacity to adapt (Nelson 2011). They use principles of ecosystem-based
adaptation and ecological engineering to incorporate natural infrastructure into existing gray infrastructure, relocate at-risk activities
and populations away from the coast, and also use incentives to change behaviors and practices.
Repair: Repair strategies seek to restore damaged ecosystems by rebuilding the composition and/or function of lost or fragmented
habitats, restoring (reinstating) the natural hydrology, sediment and nutrient balance entering and cycling through coastal ecosystems
or by assisted evolution.

C) The United States of America
The US included the wetland in the numerical targets of the NDC, calculating the National GHG inventory based on IPCC
2006 and IPCC wetland guidelines. The United States of America accounts for the world’s largest area of salt marshes(18,849 km2). The Blue Carbon in the US has recently been promoted through several wetland restoration projects led bya nonprofit organization called Restore America’s Estuaries (RAE). The Herring River Estuary Restoration Project is a carbon
offset project that is being tested as a demonstration of a voluntary carbon market initiated in 2016. REA, along with the
US EPA, National Oceanic and Atmospheric Administration, which maintains a Restoration Atlas (NOAA), and others,
established the coastal wetland carbon working group in 2016 and began studying the inclusion of BC ecosystems in the
US GHG inventory. Consequently, coastal wetlands were incorporated into the National GHG emissions and sinks for the
first time in the world in 2017.
Seagrass restoration efforts have been underway along Virginia’s Eastern Shore coast for the past 20 years. Therefore,
over 9000 acres of seagrass beds have been restored and NGOs and local research institutions are preparing to launch a
BC credit program for seagrass with the state 129.

D) People's Republic of China
Coastal BC ecosystems have been the focus of considerable attention in China in recent years as a mitigation andadaptation measure. People’s Republic of China has lost an estimated 9236–10,059 km2 of BC ecosystems such as
mangroves, salt marshes, and seagrass beds from 1950 to the present, and currently reports 1326–2149 km2 of naturaland 2–15 km2 of regenerated or created ecosystems 130. Macroalgae cultivation, on the other hand, is estimated to cover
1252–1265 km2, about the same size as natural BC ecosystems. Annual CO2 absorption is estimated to be 151.8 × 1000
t-CO2 for seagrass beds, 960-2720 × 1000 t-CO2 for salt marshes, and 399 × 1000 t-CO2 for mangroves 131.
127 https://www.cleanenergyregulator.gov.au/ERF/Pages/News%20and%20updates/News-item.aspx?ListId=19b4efbb-6f5d-4637-94c4121c1f96fcfe&ItemId=1043
128 https://www.bluecarbonlab.org/blue_carbon_accus/#:~:text=The%20Emissions%20Reduction%20Fund%20(ERF,technologies%20to%20reduce%20their%20emissions
129 https://www.pilotonline.com/news/environment/vp-nw-seagrass-blue-carbon-program-20220205-ake65u7pzbbkbbkipe7rjihacm-story.html
130 Wu et al. (2020) Opportunities for blue carbon strategies in China. Ocean & Coastal Management
Volume 194, 15 August 2020, 105241
131 http://eascongress2018.pemsea.org/wp-content/uploads/2018/12/S1.1-Blue-Carbon-Policy-andStrategy-Development-in-China_ZPeng.pdf

35

In recent years, China has become the world’s largest producer of macroalgae with 18 million tons, far ahead of second
place Indonesia’s 10 million tons 132, and including macroalgae farming as a source of BC has received considerable interest.
By contrast, as macroalgae cultivation grows in scale, investing in anchor systems with buoyancy adjustment functions isnecessary to cultivate macroalgae in offshore areas where waves and other factors create a high-energy environment.
In Wenzhou City’s Dongbang District, a new technology is being demonstrated in Sargassum fusiform aquaculture. The
creation of carbon credits for such additional investment aims to contribute to the sustainability of the aquaculturebusiness. In addition, cultivated macroalgae is currently mainly used for food but has a limited mitigation effect because
the macroalgae is converted back to CO2 during consumption. Macroalgae yields must be used for biofuel production,
long-lasting products, and residues for biochar production for soil improvement to maximize climate change mitigation
through macroalgae farming. Some reports include research on BC ecosystems, monitoring andstandardization/regulation, and promotion of international cooperation as part of the vision for marine cooperation in
the Belt and Road Initiative.

E) Republic of Indonesia
Indonesia also has vast BC ecosystems. With ~31,000 km2 of mangrove forests, its mangroves account for 20% of theworld’s total 133. Estimations revealed that Indonesia’s mangroves can sequester and store 3 billion tons of mangrove BC
and their conservation can reduce emissions by 0.2 GtCO2e per year or 30% of the country’s annual land-based emissions.
Meanwhile, seagrass beds in Indonesia are estimated to be around 30,000 km2, with carbon sequestration potential ofroughly 5.62–8.40ton C per hectare per year. In addition, after the above-mentioned China, Indonesia is the second
largest producer of macroalgae aquaculture in the world.
As an example, for the BC program in the country, the “Indonesia Blue Carbon Strategic Framework” has been formulated
for the “National Medium-Term Development Plan (RPJMN) 2020–2024,” which is currently implemented by the agencies
in charge of development and planning, marine policy, fisheries, and natural resource conservation. The framework aims
to address key strategic issues for BC in Indonesia, such as the policy, science, outreach and communication, learning
sites, and sustainable financing.
The Presidential Decree also sets a goal of restoring 1.82 million hectares of mangrove ecosystems by 2045, with anumerical target of 60,000 hectares to be restored annually to achieve this goal. Indonesia aims to integrate BC into the
National GHG inventory. Mangrove forests in Indonesia are currently declining with several pressures of degradation
identified across the country such as land use conversion, increasing management efforts. This phenomenon can also be
observed for seagrass conservation for their BC potentials 134.

F) JapanJapan has seagrass beds, salt marshes, mangrove forests, and macroalgae beds of 620, 470, 30, and 1,720 km2,
respectively, with an estimated total annual CO2 absorption of 1320–4040 × 1000 t-CO2. These figures are on the same
scale as those of China. However, the difference is that the macroalgae beds of Japan are mainly natural macroalgae beds
while those of China are farmed.
Japan does not include marine areas in its GHG inventory and does not calculate coastal wetlands in accordance with its
wetland guidelines. The Blue Carbon Study Group, comprising academic experts and related organizations, wasestablished in 2017 to overcome the aforementioned situation and focused on research, such as estimating CO2
absorption by BC ecosystems. Based on the results of the study group, the "Promotion of Efforts to Utilize Blue Carbon
Ecosystems: Establishment of a Study Group on the Role of Blue Carbon in Contributing to Global Warming Prevention"
was established in 2019 as a national study group led by the Marine and Environment Division of the Port and Harbor
Bureau of the Ministry of Land, Infrastructure, Transport, and Tourism, and concrete studies are underway to utilize BC
as a sink.
132 FAO. 2020. The State of World Fisheries and Aquaculture 2020. Sustainability in action. Rome.
133 Mark Spalding, Mami Kainumaand Lorna Collins(2010). World Atlas of Mangroves.London, Washington D.C.,Earthscan
134 Jay Mar D. Quevedo, Kevin Muhamad Lukman, Yaya Ihya Ulumuddin, Yuta Uchiyama, Ryo Kohsaka (2023). Applying the DPSIR framework to qualitatively
assess the globally important mangrove ecosystems of Indonesia: A review towards evidence-based policymaking approaches. Marine Policy, Volume 147,
2023, 105354.

36

The committee is currently working on specific studies to utilize Blue Carbon as a sink. Furthermore, the Japan Blue
Economy Association (JBE) was established in July 2020 as a corporation authorized by the government (competent
minister) using the scheme called Collaborative Innovation Partnership. In particular, JBE is conducting R&D on the roleof BC ecosystems as CO2 sinks and on the design of a new system for the assessment, certification, and issuance of BC
credits to accelerate efforts toward climate change mitigation and adaptation in other coastal and marine areas. Under
the JBE, R&D and social demonstrations related to BC, including natural and cultured macroalgae, are underway. From
the fiscal year 2020 onward, a BC credit system called J-Blue Credit® has been established, and the certification, issuance,and management of credits are conducted 135. To date, projects at 22 sites have been certified, generating a total of over
3800 tons of credits. In response to this trend, discussions are underway across ministries and agencies in the country toincorporate BC into the GHG inventory.

G) The Bahamas
On June 7, 1997, the Government signed the Ramsar Convention on Wetlands to have a comprehensive wetland policythat clearly outlines the guidelines and objectives for the protection of wetlands. This policy can be used by those
responsible for the administration of existing laws and regulations related to wetlands as a guideline to ensure theirsustainable management. It also serves as a guide for activities that may be carried out in and around wetlands.
Since 2015, the government has reestablished and rehabilitated Davis Creek in Andros to improve sequestration potential
as the mitigation route of the Land Use, Land Use Change and Forestry (LULUCF) sectors. The mangrove forest areas havebeen conserved and recovered, and the seagrass beds, reefs and mangroves are protected and rehabilitated.
Following the discovery of the largest seagrass meadow in the ocean (up to 92,000 km2 in size 136), the government of
Bahamas issued a Carbon bill 137 and established a carbon market to release credits to investors against the conservationof areas at risk of this seagrass meadow.

H）Republic of Colombia
Mangroves dominant the ecosystem of both the Pacific and the Caribbean coastlines of Colombia covering 6,500 km2
were described as the most luxuriant and wettest of the Americas, 138 and as carbon-rich-tall tidal forests. 139 The seagrassbeds in the Colombian Caribbean cover 43,223ha. The mangroves continue to decline in many areas due to increase ofindustrial and artisanal salt pans as well as agricultural fields.
Colombia ratified the Paris Agreement by Act 1844 of 2017, which also set a series of longer-term climate targets,
including 2030 GHG emission reduction goal of 20% which was updated to 51% below BAU in December 2020, and to
reduce black carbon emissions by 40% compared to 2014 levels by 2025. This target translates to 2030 emissions level of
169.44 million tCO2e, implying a net reduction of 176 million tCO2e. 140
A recently launched blue carbon finance project for the first time considers not only the carbon that mangrove trees store
in their trunks and leaves, but also the carbon they sequester in their soils. Developed by Conservation International andpartners — including Colombia’s Marine and Coastal Research Institute (INVEMAR) and the country’s Environmental
Authority — the project creates a long-term funding opportunity that is expected to conserve and restore mangroves in

135 T. Kuwae, Watanabe, A., Yoshihara, S., Suehiro F., Sugimura, Y. (2022) Implementation of blue carbon offset crediting for seagrass meadows, macroalgal
beds, and macroalgae farming in Japan. Marine Policy,138, 104996
136 Gallagher, A.J., J. W. Brownscombe, N. A. Alsudairy, A. B. Casagrande, C. Fu, L. Harding, S. D. Harris, N. Hammerschlag, Wells. Howe, A. Delgado Huertas, S.
Kattan1, A. S. Kough, A. Musgrove, N. L. Payne, A. Phillips, B. D. Shea, O. N. Shipley, U. R. Sumaila, M. S. Hossain, and C.M. Duarte. 2022. Tiger sharks support
the characterization of the world’s largest seagrass ecosystem. Nature Communications 13, 6328 (2022).
137 The Commonwealth of The Bahamas Office of The Prime Minister the Climate Change and Carbon Market Initiatives Bill (https://opm.gov.bs/climatechange-and-carbon-market-initiatives-bill/)
138 West, R. C. (1956). Mangrove swamps of the Pacific coast of Colombia. Ann. Assoc. Am. Geogr. 46, 98–121.
139 Hamilton, S. E., and Friess, D. A. (2018). Global carbon stocks and potential emissions due to mangrove deforestation from 2000 to 2012. Nat. Clim.
Chang. 8, 240–244.
140 IETA (2021) Carbon Market Business Brief Colombia

37Cispatá, an 11,000-hectare (27,000-acre) mangrove forest along Colombia’s Caribbean coast. Scientists there used a
simple but effective system for measuring the carbon locked away in the tropical sediment: Wading into the mangroves,they used a special pipe to extract soil one to three meters deep. The soil’s carbon content was then analyzed in a lab.
With its carbon stores fully calculated by the Verified Carbon Standard and the Climate, Community & Biodiversity
Standards, the most widely used programs for certifying emissions reductions, the Cispatá forest can now be valued for
its climate benefits and included in carbon markets. This critical step opens a path for other blue carbon ecosystems
around the world to be added to those markets. 141

I）United Arab Emirates
The UAE’s coastal carbon ecosystems include mangrove swamps (150 km2), seagrass beds (5500 km2), salt marshes andalgal mats, as well as associated blue carbon ecosystems such as coastal sabkha.
Regarding to the updated second Nationally Determined Contribution of UAE, submitted in September 2022, more than
3,000 coral fragments have been transplanted, and it is expected that over 10,000 more will be transplanted in the next
10 years. The Fujairah Cultured Coral Reef Gardens project was initiated in 2019 and targets the cultivation of 1.5 million
coral reef colonies over five years. The UAE had deployed 4,500 artificial reefs across its marine and coastal zones, andthese were being monitored for improved marine life and fish stocks. Additionally, natural rock barriers are being installedin coastal areas across the country in order to recreate natural habitats and breeding grounds for marine species. Taken
together, the UAE’s efforts to protect and restore coral reefs has the potential to provide jobs and reinforce livelihoods toyoung people, while helping ensure access to this innovative and emerging sector.
The National Biodiversity Strategy and the National Strategy for Coastal and Marine Environment have been guiding thecountry’s initiatives in environmental conservation and nature-based climate solutions. The National Biodiversity Strategy
lays down the framework for establishing a network of protected and effectively managed ecosystems, considering thelinking of important areas of biodiversity and ecosystem services. This has entailed biodiversity surveys; issuance of
relevant legislation and guidelines; programs to plant and protect native trees; initiatives to protect terrestrial, marine,
and freshwater fauna; and designation of new protected areas. Currently, the UAE’s 49 protected areas occupy 15.5% of
its total territory. The country is developing the UAE Smart Map of Natural Capital to identify biologically rich ecosystems
as well as the services they provide.
In the context of climate change, these ecosystems serve both adaptation and mitigation needs. Owing to a range ofrestoration and conservation efforts implemented since the 1970s, the UAE is amongst the few countries that haveproactively expanded their mangrove forest cover. Following the success of the Abu Dhabi Blue Carbon Demonstration
Project that has significantly contributed to the understanding of blue carbon stocks in the UAE, the value of these stocks
has been incorporated into federal and emirate-level policies. The UAE government is undertaking further field research
to determine mangrove soil carbon sequestration rates using radiometric dating techniques. The findings will aid thedevelopment of emission inventories and inform coastal management.
To enhance its natural carbon sinks, the UAE has taken an active role in restoring the ecosystems through planting native
trees, such as mangroves, which sequester 1,073,696 metric tons of CO2 in the country annually. During the 26th UN
Climate Change Conference (COP26) in Glasgow, the UAE announced its ambition to plant 100 million mangrove seedlings
by 2030, significantly increasing the target of 30 million seedlings set in 2020. Further, as part of its efforts to improve theconservation and to build a network of protected areas between 2021 and 2025, the emirate of Abu Dhabi targets theinclusion of a minimum of 20% marine blue carbon habitats within protected areas.
On a global level, the UAE is working on the Mangrove Alliance for Climate (MAC) that seeks to leverage a vast collectiveof expertise and resources to scale up and accelerate mangrove conservation, restoration, and resilience. Specifically, themembers commit to plant, rehabilitate, and restore mangroves within their countries and to support other members indoing the same.

141 https://www.conservation.org/blog/in-colombia-a-new-way-to-protect-mangroves-takes-root

38J）Kingdom of Saudi Arabia
In the updated first Nationally Determined Contribution submitted to UNFCCC in 2021, the Kingdom declared to
implement coastal management strategies to reduce coastal erosion, increase the sinks for blue carbon, maintain related
ecosystems and address the threats that climate change poses for marine livelihoods. In October 2021, the Kingdom
announced the Saudi Green Initiative, in which they committed to protecting 30% of its terrestrial and marine area by2030. These goals are well aligned to Vision 2030, the country’s unique transformative economic and social reform
blueprint as well as to the global Sustainable Development Goals, particularly Goal 14: Life Below Water.

Figure 4.1 Saudi & Middle East Green Initiative Commitment of safeguarding land and sea 142
The Kingdom has supported the planting of mangrove seedlings along its coasts and strengthened and enhanced thecoral reef restoration program throughout the northwestern Arabian Gulf. Saudi Arabia’s new generation coral reef
restoration technologies accelerator aims to develop innovative technologies that enhance the thermal resilience of coral
reefs and provide cost-effective options to scale up reef restoration by bringing together national stakeholders.
Several studies were conducted to estimate the outtake of mangroves and other blue carbons for the Red Sea and theArabian Gulf. These studies will be utilized in estimating a more accurate blue carbon sink.

K）People's Republic of Bangladesh
The table 143 below shows the ecosystem areas and the estimates of carbon sequestration in vegetated estuaries andcoastal habitats of Bangladesh.
HabitatMangroves
Saltmarshes
Seagrass beds

Table 4.3 Blue Carbon Habitats of People's Republic of Bangladesh
Area(ha)Tons CO2-eq/ha/year
Total CO2-eq/year(tons)
441,455
4.73
2,088,082
111,585
10.16
1,133,704
660,048
10.26
Unknown

Bangladesh’s first INDC, submitted in August 2021, proposed for 12 million tons (5%) unconditional reduction in GHG
emission from Business-as-Usual scenario by 2030 and a further 24 million tons (10%) conditional reduction in GHG
emission with support from the international community taking the base year 2011. As part of the global initiative,
Bangladesh is updating the NDC incorporating additional sectors following IPCC guidelines. The updated NDC covers
Energy, Industrial Processes and Product Use (IPPU), Agriculture, Forestry, and other Land use (AFOLU) and Waste. For
the NDC update, 2012 has been considered as the base year following the Third National Communication of Bangladesh,

142 Kingdom of Saudi Arabia “Saudi Green Initiative 2022”
143 Chowdhury Sayedur et al (2015). Blue carbon in the coastal ecosystems of Bangladesh

39which details a comprehensive national GHG emission inventory for 2012. In this NDC update, information to facilitateclarity, transparency and understanding of Bangladesh’s NDC in line with the guidelines set out in Katowice decisions(COP24/CMA1) is presented in the form of template in the last part of this document.
The NDC update aims to further mitigation actions that Bangladesh may take to tackle its growing emissions and play itsrole in global efforts. The NDC calls for a number of mitigation actions that will help limit the country’s GHG emissions.
These actions will play a key role in realizing the move to a low-carbon, climate-resilient economy and becoming a middleincome country whilst ensuring that it will not cross the average per capita emissions of the developing countries.

L）Republic of India
The updated first NDC, submitted in August 2022, the government set the long-term goal of reaching net-zero by 2070.
No.
1
2
3
4
5
6
7
8

Table 4.4 Republic of India NDC Committed Activities
Descriptions
To put forward and further propagate a healthy and sustainable way of living based on traditions and values ofconservation and moderation, including through a mass movement for ‘LIFE’– ‘Lifestyle for Environment’ as a
key to combating climate change.
To adopt a climate friendly and a cleaner path than the one followed hitherto by others at corresponding levelof economic development.
To reduce Emissions Intensity of its GDP by 45 percent by 2030, from 2005 level
To achieve about 50 percent cumulative electric power installed capacity from non-fossil fuel-based energy
resources by 2030, with the help of transfer of technology and low-cost international finance including fromGreen Climate Fund (GCF)
To create an additional carbon sink of 2.5 to 3 billion tons of CO2equivalent through additional forest and tree
cover by 2030.
To better adapt to climate change by enhancing investments in development programs in sectors vulnerable
to climate change, particularly agriculture, water resources, Himalayan region, coastal regions, health, anddisaster management.
To mobilize domestic and new & additional funds from developed countries to implement the above mitigation
and adaptation actions in view of the resource required and the resource gap.
To build capacities, create domestic framework and international architecture for quick diffusion of cuttingedge climate technology in India and for joint collaborative R&D for such future technologies

Akhand A. et al (2022) 144collated data on the Indian blue carbon repository (mangroves, seagrasses, and salt marshes)from peer-reviewed literature on carbon stock assessment. The research indicated the blue carbon ecosystems of India
could have a collective carbon stock of 67.35 Tg C (mangroves, seagrass, and salt marsh accounting for 67 Tg C, 0.0630 Tg
C, and 0.0049 Tg C, respectively). Several studies have ubiquitously measured the spatial extent of mangroves (-4,991
km2), seagrasses (- 517 km2), salt marshes (290–1,398 km2) in India.
The study identified that less than half of the total mangrove habitats of India are yet to be sampled leaving a scope of
substantial uncertainty in nationwide blue carbon estimates. The spatial extent of India’s salt marshes is another aspectthat needs to be delineated with a higher confidence level.

M）Arab Republic of Egypt
On June 2022 Arab Republic of Egypt submitted the Egypt’s first updated Nationally Determined Contributions. The
adaptation policy chooses mainly the accommodation and protection approaches to the risks resulting from climatechange by the combination of soft and hard interventions. The government develops the climate resilient Integrated
Coastal Zone Management Plan for the North Coast of Egypt, which links the land use development plans, and the coastal
protection works over the next 10-15 years.

144 Akhand, A., Chanda, A., Jameel, Y. et al (2022). The present state-of-the-art of blue carbon repository in India: a meta-analysis. Sustain Sci.

40

They have adopted the structural and architectural interventions of the engineering protection work (ex. maritime walls,
submersible barriers, soil fixation), the artificial nourishments to compensate for the erosion of beaches andconstructions and reinforcements of anti-flood protection structures. From the nature-based approach, they reinforce
the sand dune stabilities and the natural defense lines against sea encroachment during storms by the cultivation of wild
plants and wooden barriers.
From the point of the tourism, they maintain and expand the protectorates to cover 17% of the national marine andwildlife areas with at least 5% constituting coastal areas. They will assess the degree of fragility and vulnerability of
touristic sites, marine and wildlife protectorates, and sites of archaeological value, orienting tourism growth away fromenvironmentally sensitive areas, and implementation of integrated environmental management systems in touristic sites.

N）United Kingdom of Great Britain and Northern Ireland
In December 2020, the United Kingdom of Great Britain and Northern Ireland (the UK) communicated its Nationally NDC
to the UNFCCC in line with Article 4 of the Paris Agreement. In the NDC, the UK committed to reducing economy-wide
greenhouse gas emissions by at least 68% by 2030, compared to 1990 levels. At COP26 in November 2021, the UK hosted
in Glasgow to pursue efforts to limit global temperature increase to 1.5°C. The NDC encompasses emissions and removals
from England, Scotland, Wales, and Northern Ireland.
The UK’s vision for the marine environment is for clean, healthy, safe, and biologically diverse ocean and seas. The
sustainable use, protection and restoration of the UK’s marine environment is underpinned by the UK Marine and Coastal
Access Act (2009), the Environment Act (2021) and Fisheries Act (2020), UK Marine Policy Statement, Marine Strategy,commitment to an ecologically coherent well-managed network of Marine Protected Areas, and Joint Fisheries Statement.
Through the UK Marine Strategy, HM Government and Devolved Administrations are working closely together to achieve
Good Environmental Status in the UK’s seas.
The Scottish Government has set out a new Blue Economy vision for the sustainable management of Scotland’s seas,
establishing long term outcomes to 2045 and including a dedicated climate outcome to support ecosystem health,improved livelihoods, economic prosperity, social inclusion, and wellbeing. New actions to increase protection of themarine environment include delivery of a network of highly protected marine areas by 2026, fishery management
measures across the Marine Protected Areas network by 2024 and introduction of a Scottish Wild Salmon Strategy. New
evidence is also being delivered through the Scottish Blue Carbon Forum, building upon actions set out in the second
Scottish Climate Change Adaptation Program to address Scotland’s marine climate risks.
In November 2019 the Welsh Government published the first Welsh National Marine Plan for the next 20 years to achieve
healthy and resilient seas and marine ecosystems, in support of a thriving, sustainable economy.
The Marine Plan for Northern Ireland, published in April 2018, supports the UK Marine Policy Statement, the UK Marine
Strategy and the UK’s vision for the marine environment. The sustainable development of Northern Ireland’s marine area
is further underpinned by the Marine Act (Northern Ireland) 2013 and the Marine and Coastal Access Act 2009. A second
iteration of the Plan is currently being drafted which will take account of the advancements in science, technology, policy,
and legislation, particularly in relation to climate change mitigation and adaption including Blue Carbon, Sustainable
Fisheries and Offshore Renewable Energy. The Marine Plan for Northern Ireland is expected to be finalized, adopted andpublished in 2023.

O）Kingdom of Norway (Nordic Area)
The Nordic Blue Carbon Project, funded by the Norwegian Environment Agency, opened the final report 145 regarding the
project about the climate adaptation, carbon capture and long-term storage in blue forests in the Nordic region in 2020.
The project was led by the Norwegian Institute for Water Research, and cooperated with GRID-Arendal, the Institute of
145 Helene Frigstad, Hege Gundersen, Guri S. Andersen, Gunhild Borgersen, Kristina Ø. Kvile, Dorte Krause-Jensen, Christoffer Boström, Trine Bekkby, Marc Anglèsd'Auriac, Anders Ruus, Jonas Thormar, Kaya Asdal and Kasper Hancke (2021). Results from the Nordic Blue Carbon Project. TemaNord 2020:541

41

Marine Research, Aarhus University and Åbo Akademi University. Followers are depended on the final report.
The following map shows the indications of rockweed, kelp, and seagrass (The dotted lines are predicted). Around 5,550
km2 of rockweed beds are found along most of the coastlines of the Nordic region, but with low coverage in Denmark.
Seagrass covers 2600 km2, a relatively small areal distribution compared to kelp and rockweed, but it is still an important
habitat along the coastlines of Norway, Sweden, and Denmark.

Figure 4.2 Blue Carbon Habitats in Nordic146
Kelp forests are the most common of the Nordic Blue Forests, covering approximately 11,000 km2. They are mostwidespread along the rocky shores of Norway, Iceland, and the Swedish west coast. There are few to no kelp forests along
the Swedish and Finnish coasts. Greenland (as part of Denmark) has potentially large kelp forests, but due to limited data
availability, the distribution of Blue Forest habitats has not been estimated there.
The compiled estimates Blue Carbon in Kingdom of Norway are estimated as below. The estimates are predicted or are
the weighted average of available data. The 69% of the blue forest are kelp forests, storing 2.7 million tons of CO2, the
19% are rockweed beds, storing 0.8 million tons of CO2 and 12% are seagrass meadows, storing 0.5 million tons of CO2.
Table 4.5 The Compiled estimates Blue Carbon Parameter of Norway 147
Kelp
RockweedParameter
Unit(SD/Min/Max)(SD/Min/Max)
Area of Norway
Area
km2
7,417(-/-/-)
3,090(-/-/-)Net Primary Production (NPP)
NPP
Million tons FW y-1
49.3(-/24/70)
17.2(0/-/-)
NPP, C units
Gg C y-1
2,292(-/1,090/4,309)
903(862/-/-)
Particulate Organic Carbon (POC)
POC exported from beds/meadows
Gg C y-1
2,195(-/1,602/5,325)
865(294/-/-)
POC sequestered on the shelf
Gg C y-1
95(-/59/134)
40(-/-/-)
POC sequestered in seagrass meadows Gg C y-1-(-/-/-)-(-/-/-)
POC exported to the deep sea
Gg C y-1
53(-/0/115)
21(-/0/45)
Dissolved Organic Carbon (DOC)
DOC exported
Gg C y-1
1,146(-/458/2,750) 181(-/<45/362)
DOC exported below 1,000m
Gg C y-1
355(107/-/-)
56(42/-/-)
Total
Total sequestration
Gg C y-1503(-/141/601)
117(-/33/139)
Total sequestration
Mill CO2equiv. y-1
1.8(-/0.5/2.2)
0.4(-/0.1/0.5)* SD: Standard Deviation

Seagrass(SD)
90(-)
0.5(-)
29(10)
5(2.3)-(-)
3.2(1.3)
0.8(-)
2.0(-)
0.7(-)
4.6(1.3)
0.02(0.005)

146 Helene Frigstad, Hege Gundersen, Guri S. Andersen, Gunhild Borgersen, Kristina Ø. Kvile, Dorte Krause-Jensen, Christoffer Boström, Trine Bekkby, Marc
Anglès d'Auriac, Anders Ruus, Jonas Thormar, Kaya Asdal and Kasper Hancke (2021). Results from the Nordic Blue Carbon Project. TemaNord 2020:541
147 Helene Frigstad, Hege Gundersen, Guri S. Andersen, Gunhild Borgersen, Kristina Ø. Kvile, Dorte Krause-Jensen, Christoffer Boström, Trine Bekkby, Marc
Anglès d'Auriac, Anders Ruus, Jonas Thormar, Kaya Asdal and Kasper Hancke (2021). Results from the Nordic Blue Carbon Project. TemaNord 2020:541

42

As the result of the project, they pointed the following knowledges as the knowledge gaps to need for collaborative theNordic projects:

•
•
•
•
•
•
•
•
•
•
•
•

Improve distribution mapping and monitoring of Blue Forests.
Address kye uncertainties in the Nordic Blue Carbon budget, such as the rates of long-term carbon storage.
Improve collaboration between scientists and policymakers to develop IPCC guidelines for kelp forests.
Establish greenhouse gas inventories for Blue Forest habitats.
Research the distribution and function of salt marshes.
Establish the effects of climate change and other human pressures on Blue Forests.
Research trophic cascade and other effects of overfishing.
Develop management measures to improve resilience of Blue Forests.
Establish methods for successful restoration of Blue Forests.
Conduct in-field testing of the effectiveness of management measures.
Map and develop measures to preserve areas of high sedimentation and long-term storage of Blue Carbon in shelf anddeep-sea sediments.
Determine possibilities for using kelp cultivation to increase Blue Carbon biomass and its potential role in climate mitigation.

P）Republic of Fiji
The adverse climate change impacts from the intense floods, and extreme weather events, to rising sea levels and its
resultant saltwater intrusion and loss of habitable land has been affected all aspects of life for Fijians – the environment,
economy, social development, as well as cultural practices and traditional ways of life. Fiji is facing loss and degradation ofvital ecosystems and natural resources, including its coral reefs, coasts, and catchments, on which key sectors of its
economy such as agriculture and fisheries are dependent. Further, its critical infrastructure is frequently damaged by theincreasing extreme weather events, which are impacting the social well-being, employment and livelihoods of the Fijian
people.
Regarding to the first NDC, submitted in December 2020, Fiji sees this NDC update as an opportunity to further support
its commitment towards the Paris Agreement by mainstreaming its blue economy ambitions in to its NDC targets throughenhanced ocean governance to not only achieve national ocean conservation but also contribute towards enhancing theocean as a carbon sink.
Through the Implementation of the National Ocean Policy, Fiji will be allocating 30% of its EEZ as Marine Protected Areas
and work towards 100% management of its EEZ by 2030. This compliments Fiji’s National Adaptation Plan concurrently its
Low Emission Development Strategy, which highlights the need to sustainably manage and protect marine and coastal
ecosystems, strengthen their resilience, and restore them when they are degraded. This includes conserving ocean
reservoirs as carbon sinks through supporting the restoration, enhancement, and conservation of coastal ecosystems suchas mangroves, sea grasses and coral reefs.

43

No.
Target 1
Target 2
Target 3
Target 4
Target 5
Target 6
Target 7
Target 8
Target 9
Target 10
Target 11
Target 12

Table 4.6 Republic of Fiji’s NDC Mitigation targets
Mitigation Targets Descriptions
To reduce 30% of BAU CO2 emissions from the energy sector by 2030.
As a contribution to Target 1, to reach close to 100% renewable energy power generation (grid connected)
by 2030, thus reducing an expected 20% of energy sector CO2 emissions under a BAU scenario.
As a contribution to Target 1, to reduce energy sector CO2 emissions by 10% through energy efficiency
improvements economy-wide, implicitly in the transport, industry, and electricity demand-side
subsectors.
As a contribution to Target 1, to reduce domestic maritime shipping emissions by 40%. Adaptation Target
To adopt Climate Smart Agriculture practices, with emphasis on the promotion of sustainable practices incrop management, livestock and sugarcane farming Fiji’s Updated NDC 2020 and fisheries.
To enhance resilience by upgrading, repairing, and relocating existing critical public infrastructure.
Develop simplified and standardized early warning and monitoring systems and prioritize nature-based
solutions to mitigate the impact of flooding and cyclones.
Relocate highly vulnerable communities and implement the concept of ‘build back better’.
Build strong healthcare system by implementing the ‘Guidelines for climate-resilient and environmentally
sustainable health care facilities in Fiji’.
To conserve natural environment and biodiversity wealth enabling sustainable long-term provision of
ecosystem services, including carbon sequestration potential.
To plant 30 million trees by 2035.
To establish 30% of our Exclusive Economic Zones (EEZ) as Marine Protected Areas and work towards
100% management of our EEZ by 2030 through the implementation of the National Ocean Policy.

The Republic of Fiji National Adaptation Plan in 2018 declared the Adaptation Measures of Biodiversity and the Natural
Environment. The national marine ecosystem services have been valued at FJD 2.5 billion per annum. These goods andservices provide the biophysical foundation for much economic activity, particularly those vital for the national economy(fisheries, forestry, agriculture, and tourism).
Tourism is of relevance as one of the most important components of the economy. Approximately 40 percent of Fiji’s GDP
and employment can be traced some to the tourism sector. It supports and provides livelihoods as well as having a vitalrole in supporting the national balance of payments. For instance, our coral reef ecosystems are one of the most vulnerable
ecosystems to climate change and the longer-term outlook for coral reefs in the Pacific is poor.
More immediately, national ecosystems are degrading due to insufficient protection from development-related activities
such as unsustainable logging, clearance for commercial developments, infrastructure and agriculture, and over-fishing.
This in turn renders them less capable of adapting to climate change impacts, reducing their climate resilience benefits tosociety. As Fiji’s largest income earner, the economic benefits of intact ecosystems to the tourism sector are of paramountimportance.

44

No.
Action 1
Action 2
Action 3
Action 4
Action 5
Action 6
Action 7
Action 8
Action 9
Action 10
Action 11
Action 12
Action 13

Table 4.7 Republic of Fiji’s Adaption Measures
Adaptation Actions Descriptions
16.1 Strengthen enforcement of planning and environmental legislative and institutional frameworks,
most notably the Environment Management Act and Environment Impact Assessment process.
Prioritize and delineate critical areas for protection and sustainable management based on ecosystemservices, cultural importance, biodiversity, food security, water security, access and benefit sharing, andimportance for adaptation and disaster risk reduction.
Gain endorsement of mangrove management plan, implement mangrove rehabilitation projects, andstrengthen the regulations regarding mangrove removal and conversion.
Assess and monitor the state of coastal ecosystems and protect and enhance the natural coastal
defenses.
Strengthen the management and monitoring of ecosystems.
Regularly update and publish the National Environment Management Strategy and ‘State of Environment
Reports’ on a five-year cycle to inform development and disaster management planning processes atboth national and sub-national levels.
Integrate green and blue accounting/ ecosystem valuation into the GDP formulation and budget processby 2020.
Implement ecosystem-based approaches to adaptation to protect, maintain, and restore degradedhabitats with active community,111 NGO and private sector engagement in particular the restoration ofcritical watersheds, riparian, and coastal zones.
Expand ‘Tree-Planting Campaign’ to encourage voluntary tree and/or mangrove planting activities which
are to be conducted as a part of school curriculums, community stewardship and the Corporate Social
Responsibility.
Implement a national program for the monitoring and management of rivers and watersheds (ridge toreef) to reduce the negative impacts of unsustainable activities linked to logging, river and seabed mining.
Identify and map ‘climate-vulnerable’ species of flora and fauna and their habitat (lifecycle), including
connections with the need to control invasive species, and create a national plan and monitoring system
to support climate vulnerable species.
Increase and mobilize resources available for the implementation, monitoring and enforcement of the
National Biodiversity Strategy and Action Plan.
Endorse and implement a comprehensive waste management plan for rural and urban areas to reducethe impact of pollution on terrestrial and marine ecosystems and the reliance upon landfill as a waste
management option.

(2) Article 6 of Paris Agreement
As governments work on achieving NDCs and cooperative approaches under Article 6 of the Paris Agreement, the benefits
and challenges of voluntary carbon markets (VCMs) and work with project investors, developers, and local communities
must be considered to understand the implications of different approaches and decisions. Negotiations are underway toclarify the potential implementation of international trading, with authorization being the most controversial issue during
the Article 6 consultations at COP 27. Some countries want to retain the right to revoke or modify their authorizations
after emission reductions become Internationally Transferred Mitigation Outcomes or are credited as emission reductions
under Article 6.4. This condition could undermine the viability of the market mechanism under this article because market
participants are markedly concerned regarding the risk of a host country withdrawing its approval of a project.
Furthermore, the approach could stall the flow of funds to support emission reduction projects and even undermine theintegrity of the already announced Article 6.2 bilateral agreements.

(3) IPCC guideline revision
A BC accounting framework, which includes internationally recognized BC habitats but so far excludes seaweed ormacroalgae, has been compiled 148 . Carbon budget methodologies for nearshore macroalgal farming have been

148 Ross F, Tarbuck P and Macreadie PI (2022) Seaweed afforestation at large scales exclusively for carbon sequestration: Critical assessment of risks, viability
and the state of knowledge. Front. Mar. Sci. 9:1015612. doi: 10.3389/fmars.2022.1015612

45

considered 149 , but carbon sequestration methodology studies for offshore macroalgal farming are still underdevelopment. However, macroalgae may sink directly to the storage site through marine afforestation; thus,
methodologies to document this transport may be simpler than mapping detritus export and sediment transport
pathways from the nearshore environment to offshore sink sites. This timescale may be faster than current pathways forcarbon sequestration in macroalgae, which are difficult to track because carbon may be easily monitored and quantified.
However, monitoring carbon storage sites and quantifying carbon sequestration in the deep sea remains a challenge.
Biomass accumulation by macroalgae would be relatively simple, but mapping pathways for viable sequestration remains
a major challenge for marine afforestation 150 . For any carbon offset project or proposal, providing an accurate
methodology for determining the amount of sequestered carbon is critical. The verification methodology must meetinternational standards for carbon sequestration, such as the United Nations Framework Convention on Climate Change(UNFCCC), must be met to increase the eligibility of ocean macroalgal farming for carbon credits (Michaelowa et al., 2019).
This methodology would include criteria around proving additionality, permanence, and accuracy; consideration would
need to be provided to incorporating a new international standard for carbon sequestration by natural and farmed
macroalgae in the IPCC wetland guidelines or setting a separate international standard.

(4) Requirements for BC projects
The number of BC projects is gradually increasing; in addition to carbon sequestration, institutional design is underway
to ensure project quality and promote initiatives that contribute to fair benefit sharing and biodiversity conservation.
High-quality BC principles and guidance 151 was released at COP27 held in Egypt in November 2022. The guiding principles
are based on the following: the “Quality Assessment Principles for Voluntary Carbon Markets (Core Carbon Principles) 152”
proposed by the Taskforce on Scaling Voluntary Carbon Markets as key points that must be met by projects to avoid
climate change and biodiversity crises and advance climate justice and the “Quality Assessment Principles for Voluntary
Carbon Markets (Core Carbon Principles)” proposed by the Taskforce on Scaling Voluntary Carbon Markets and theProvisional Claims Code of Practice introduced by the Voluntary Carbon Markets Integrity (VCMI) Initiative 153. The Core
Carbon Principles call for additionality, baseline setting, permanence, avoidance of double counting, and avoidance ofadverse environmental and social impacts that BC projects should consider. By contrast, The Code of Practice of VCMI
requires carbon credit users to prioritize CO2 emission reductions before using credits to purchase high-quality credits
and report on the transparency of credit use.
Tables 4.3–4.7 summarize the requirements for the restoration and conservation of carbon sinks in actionable BC
ecosystems, conservation and restoration of macroalgal beds, macroalgal farming and carbon sequestration, andmacroalgal farming and product utilization. Table 2.1 shows the requirements to meet Actionable Blue Carbon criteria.

149 Duarte, C. M., Wu, J., Xiao, X., Bruhn, A., and Krause-Jensen, D. (2017). Can seaweed farming play a role in climate change mitigation and adaptation? Front.
Mar. Sci. 4, 100
150 GESAMP (2019). “High level review of a wide range of proposed marine geoengineering techniques”.(Boyd, P.W. and Vivian, C.M.G., eds.).
(IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UN Environment/UNDP/ISA Joint Group of Experts on the Scientific Aspects of Marine Environmental
Protection). Rep. Stud. GESAMP No. 98, 144 p
151 https://merid.org/wp-content/uploads/2022/11/HQBC-PG_FINAL_11.8.2022.pdf (accessed on January 8, 2023)
152 “Taskforce on Scaling Voluntary Carbon Markets Final Report.” Taskforce on Scaling Voluntary Carbon Markets, January 2021. https://iif.com/
Portals/1/Files/TSVCM_Report.pdf.
153 Provisional Claims Code of Practice.” Voluntary Carbon Markets Integrity (VCMI) Initiative, June 7, 2022. https://vcmintegrity.org/wpcontent/uploads/2022/06/VCMI-Provisional-Claims-Code-of-Practice.pdf.

46

Table 4.8. Solution for the Restoration of the Carbon Sink 154
RealAdditionality
based on credible
baselines
Monitored,
reported, andverified (MRV)No net harm
Permanent
Leakage
Double counting
Implementation
challenges
Key new
opportunities

Ok
Ok
Potentially high costs to monitor and verify carbon sequestered in sediments, especially thoseof large underwater seagrass
Ok
Long-term viability is affected by multiple stressors, including climate change (e.g., sea levelrise, warming); can account for long-term uncertainty (e.g., buffer system or metric ton/year
accounting approach)Ok
If on public land or in marine jurisdiction; accounting process outlined by Article 6 of the Paris
Agreement prevents most, but not all, cases of double counting but not double claiming
Large dependence on upstream or nonlocal environmental factors (e.g., pollution andwarming affecting viability of seagrass and macroalgal bed restoration). Large upfront costs
before credit issuance
Implement latest science-based standard restoration methods to increase project successrates. Consider methodologies to support required upstream interventions (e.g., runoff
nutrient load reduction)

Table 4.9. Solution of avoid loss (or conservation) of carbon stock and sink.
(e.g., halt deforestation, development, and pollution) 155
Real
Ok
Additionality based
Projects can face similar challenges to REDD+ (e.g., additionality depends on assumptions ofon credible baselines
future socioeconomic incentives and environmental policy; for seagrass, limited data on
historical extent)
Monitored, reported,Ok
and verified
No net harm
Ok
Permanent
Depends on continued protection; uncertainty can be addressed with buffer systems
LeakageCan be an issue for small-scale, fragmented projects
Double counting
Pending further Article 6, excoriations on whether emission avoidance credits (e.g., projectbased and/or jurisdictional REDD+) may be internationally traded and counted toward NDCs
Implementation
Typically involves many stakeholders and requires multifaceted community-led development
challenges
projects to address underlying drivers of destruction and unsustainable use; in some cases,lack of clear ownership or carbon rights within the tidal zone can pose challenges
Key new
Large-scale jurisdictional approach to facilitate baseline setting, avoid leakage, and address
opportunities
nonlocal upstream threats. Project bundling approach and cost-efficient remote monitoring
to decrease verification cost per credit. Consider methodologies to support required
upstream interventions (e.g., runoff nutrient load reduction)

154 McKinsey & Company, Blue carbon: The potential of coastal and oceanic climate action Nature-based climate solutions in the world's oceans can play animportant role in conservation and carbon abatement efforts worldwide, 2022.
155 McKinsey & Company, Blue carbon: The potential of coastal and oceanic climate action Nature-based climate solutions in the world's oceans can play animportant role in conservation and carbon abatement efforts worldwide, 2022.

47

Table 4.10. Solution of avoid loss of and restore macroalgal beds, including kelp forests 156
RealOk
Additionality based on
Limited historical datacredible baselines
Monitored, reported, and Complex due to the dispersal of carbon biomass to nonlocal, allochthonous sinks
verified
No net harm
Ok
Permanent
Limited to fraction of carbon biomass exported to sediments (nonlocal)
Leakage
Ok
Double counting
Similar issues faced by other coastal BC ecosystem projects
Implementation
Large dependence on upstream or nonlocal environmental factors (e.g., pollution andchallenges
warming), impacts from herbivores (fish, sea urchins)
Non-standardized, context-dependent restoration
Key new opportunities
Map extent and trends of kelp ecosystems. Model carbon sequestration of kelp in nonlocal
sinks. Develop cost models for restoration
Table 4.11. Solution of the farm and sequester biomass (via sinking) 157
Real
Ok
Additionality based on
Additionality depends on role of limited nutrients in counterfactual scenarios
credible baselines
Monitored, reported,
Requires process monitoring and possibly needs modelingand verified
No net harm
Uncertain ecological impact of large-scale farms and deep-sea sinking
Permanent
Possibly over 100-year duration if sunk below 1000 m
Leakage
Ok
Double counting
Requires clear rules regarding attribution between farm operator and sedimentjurisdiction
Implementation
Unproven technical viability and financial requirements of large-scale or offshore farming
Challenges
Key new opportunities
Conduct pilot projects to verify sequestration models and study environmental impacts.
Develop methods to mitigate impacts on ecology and commerce. Establish policy
framework regulating large-scale biomass sinking at sea
Table 4.12. Solution of the farm and harvest biomass (e.g., food consumption, processing as a biofuel) 158
Real
Ok
Additionality based on
Avoided emissions depending on type of displaced product and production process
credible baselines
Monitored, reported,
Requires process monitoring, likely modelingand verified
No net harm
Uncertain ecological impact of large-scale farms and deep-sea sinking
Permanent
Satisfied only for avoided emissions
Leakage
Ok
Double counting
Requires clear rules regarding attribution between operator and sediment jurisdiction
Implementation
Unproven technical viability and financial requirements of large-scale or offshore farming
Challenges
Key new
Conduct pilot projects to verify sequestration models and study environmental impacts.
opportunities
Develop methods to mitigate impacts on ecology and commerce

156 McKinsey & Company, Blue carbon: The potential of coastal and oceanic climate action Nature-based climate solutions in the world's oceans can play animportant role in conservation and carbon abatement efforts worldwide, 2022.
157 McKinsey & Company, Blue carbon: The potential of coastal and oceanic climate action Nature-based climate solutions in the world's oceans can play animportant role in conservation and carbon abatement efforts worldwide, 2022.
158 McKinsey & Company, Blue carbon: The potential of coastal and oceanic climate action Nature-based climate solutions in the world's oceans can play animportant role in conservation and carbon abatement efforts worldwide, 2022.

48

(5) Environmental concerns from large-scale macroalgal farming on deep-sea biological communities
Large-scale farming in offshore areas, including the high seas, is considered in the strategy for CDR through macroalgal
farming. Therefore, considering the national and international legal frameworks applicable to macroalgal farming is also
necessary. Specifically, international legal frameworks, such as UNCLOS, the CBD, the Convention on the Prevention ofMarine Pollution by Dumping of Wastes and Other Matter (London Convention), and the Protocol to that Convention(London Protocol), may be applicable. Macroalgae cultivation activities in territorial waters are mostly regulated similarly
as shellfish farming (Billing et al 2021, Wood et al 2017), and explicit regulations regarding sinking macroalgae in the deep
ocean are unavailable at any national or international level.
National laws may also apply depending on the implementation method. For example, in the United States, the Outer
Continental Shelf Lands Act, National Environmental Policy Act, Endangered Species Act, Coastal Zone Management Act,
Marine Protection, Research and Reserve Act, and Clean Water Act may apply 159.
Science cannot currently discern the impacts of large-scale macroalgae sinking in the ocean on marine life or the carbon
cycle (Ricart et al., 2022 160). The ecological carrying capacity of large-scale offshore farming and sinking is unresolved.
The consequences for primary productivity in the upper ocean and associated food webs (e.g., from diverting nutrients
into large-scale production of macroalgae), as well as the impacts of large macroalgae biomass to deep-sea biologicalcommunities (e.g., from oxygen depletion), are largely unknown. Moreover, not all macroalgae ecosystems, farmed orwild, may sequester carbon (Gallagher et al 2022 161); the storage amount, time, and turnover rate of carbon by sunkmacroalgae in the deep ocean, which likely will depend on the location, remains unknown (Siegel et al 2021 162).
If the objective of farmed macroalgae is to sink it for financial gain through carbon credits, then should the valued biomass
be considered waste? Furthermore, comprehensive third-party environmental impact assessments will be crucial.
Similarly, accreditors of carbon credits should enforce reliable verification processes and hold companies accountable forthe accuracy and precision of carbon removal estimations. Commensurate with emergent scientific evidence, a plural
oversight approach that embraces and coordinates the diversity of actors, which include governments, managers, civilsociety (as consumers and final beneficiaries), and the private sector, is urgently needed. All these factors play a vital rolein climate action governance.

159 Korey Silverman-Roati, Michael B. Gerrard & Romany M. Webb, Removing Carbon Dioxide Through Seaweed Cultivation: Legal Challenges and Opportunities,
Sabin Center for Climate Change Law, Columbia Law School, September 2021 (2021).
Available at: https://scholarship.law.columbia.edu/faculty_scholarship/2980
160 Ricart, Aurora & Krause-Jensen, Dorte & Hancke, Kasper & Price, Nichole & Masqué, Pere & Duarte, Carlos. (2022). Sinking seaweed in the deep ocean for
carbon neutrality is ahead of science and beyond the ethics. Environmental Research Letters.
161 John Barry Gallagher, Victor Shelamoff, Cayne Layton, Seaweed ecosystems may not mitigate CO2 emissions, ICES Journal of Marine Science, Vol. 79(3),585–592
162 D A Siegel, T DeVries, S C Doney and T Bell(2021). Assessing the sequestration time scales of some ocean-based carbon dioxide reduction strategies.
Environmental Research Letters, Vol16(10).

49

Chapter 5
Potentials of Carbon Removals by and Credits from Blue Carbon
This chapter outlines the quantitative potential of BC through its conservation, regeneration, and creation and how large
the credits could be in the next few decades.

(1) Changes in Market Perceptions of Blue Carbon
Remarkably ambitious carbon prices can help close the gap between pledges and policy and “keep 1.5 alive.” Record ETS
prices were observed in the European Union (EU), California, New Zealand, and Republic of Korea, among other markets,
while several carbon taxes also saw prices hit their highest levels yet. A combination of policy reforms, anticipated changes,
speculative investment interests, and broad economic trends, especially in global energy commodity markets, are driving
these ETS price spikes. Nonetheless, prices must rise considerably to meet the Paris Agreement temperature goals
because less than 4% of global emissions are currently covered by a direct carbon price within the range needed by 2030.
Credits from independent crediting mechanisms dominate the carbon market (Figures 5.1 and 5.2). Driven by corporate
commitments, annual VCM value exceeded USD 1 billion for the first time. Compliance demand for carbon credits remains
limited despite new rules for international carbon markets under Article 6 of the Paris Agreement provide clarity that may
enable future growth.

Figure 5.1. Global volume of issuances by crediting mechanism category 163

163 The World Bank International Bank for Reconstruction and Development “State and Trends of Carbon Pricing 2022” (2022)

50

Figure 5.2. Credit issuance and number of projects in 2021 by category of mechanisms 164(2) Current estimates of carbon removals by blue carbon
With the emergence of the BC market, various entities have published estimates of Potentials of Carbon Removals by andCredits from BC. For example, McKinsey (2022) estimated the scale of blue carbon removals and the cost per solution(Figure 5.3). The report showed that established BC solutions offer abatement of 0.4 to 1.2 metric gigatons of carbon
dioxide (GtCO₂) per year; emerging solutions could add up to ~1.8 GtCO₂ per year for a total of ~3 GtCO₂ per year. Thispotential jumps to ~3 GtCO2 of annual abatement (~7% of total current annual emissions) if the solutions in the emerging
category, such as large-scale macroalgae farming and bottom-trawling management, were to be fully confirmed andimplemented. Nascent solutions might add another 1 to 2 GtCO2 of annual abatement potential in the long term but thescience remains highly uncertain. Annual human emissions are currently around 40 GtCO2 to put these numbers into
context.

164 The World Bank International Bank for Reconstruction and Development “State and Trends of Carbon Pricing 2022” (2022)

51

Figure 5.3. Abatement potential from established and emerging BC solutions by 2050, GtCO2 equivalent per year 165
Moreover, in the estimation of the abatement or conservation potential on a 2050 timeline, the deep dives on kelp
reforestation and bottom trawling show how economies of scale in these emerging solutions could help reduce costs.
The analysis suggests that around one-third of the total abatement potential would be viable below $18 per tCO2 (Figure5.4). This value is more than the $5 to $15 per tCO2 average price paid in the VCMs but below the $40 to 100 per tCO2
paid in the European compliance markets over the past year (February 2021–2022).

Figure 5.4. Abatement cost curve, nature-based solutions, $ per metric ton of carbon dioxide (tCO2)166(3) Blue Carbon and Voluntary Carbon Mechanismsa) Plan Vivo
Plan Vivo generated the world’s first carbon credits to the voluntary carbon market (VCM), which are sold to organizations,such as the World Bank in 1997 (Scolel'te Project, Planting trees in Chiapas, United Mexican States, through acollaboration between the University of Edinburgh, El Colegio de la Frontera Sur, other local partners, Table 5.1).
Plan Vivo created proto standard in 2001/2002, the second standard in 2004, the third standard in 2008, the fourth
standard in 2013, and the fifth standard in 2022. In 2013, the Plan Vivo-certified Mikoko Pamoja project in Gazi, Kenya,
became the world’s first Blue Carbon Project by receiving Plan Vivo Certificates for the conservation and restoration of its
mangrove forests. The project later won a UN Equator Prize award.

165 McKinsey & Company “Blue carbon: The potential of coastal and oceanic climate action (2022). Source: Peter Macreadie et al., “Blue carbon as a natural climate
solution,” Nature Reviews Earth & Environment, November 2021, Volume 2; Ove Hoegh-Guldberg et al., The ocean as a solution to climate change: Five
opportunities for action, World Resources Institute, 2019; Enric Sala et al., “Protecting the global ocean for biodiversity, food and climate,” Nature, March 2021,
Volume 592; McKinsey analysis
166 The abatement potential shown for blue-carbon solutions corresponds to the lower-end estimates. An additional 1.9 metric gigatons (Gt) of natural-climatesolutions abatement is not costed (avoided deforestation: 0.95 Gt; peatland restoration: 0.21 Gt; reforestation: 0.36 Gt; cover crops: 0.22 Gt; trees in cropland: 0.11
Gt). This analysis filter out low-feasibility lands (those with high economic returns—ex., >$45/hectare—from agriculture), which are more likely to be accessed bymechanisms other than voluntary carbon markets. Lower-end estimate of bottom-trawling emission abatement, limited to activity in the top 50 meters of the ocean.
The higher-end estimate offers 1.5 Gt at a (lower) average opportunity cost of $11/tCO2.Macroalgae farming potential based on current cost and implementation
growth estimates; chart does not reflect potential cost reductions from technology learning curves and scaling.

52

Table 5.1. Plan Vivo-certified and under processed (project approved only) Blue Carbon Projects List
Country

Date

Project
size

Kenya

2013

117 haMadagascar

2018

1,200ha

Kenya

2019

450 ha

Kenya

2022

300 haProject (Lead Organization/Activity)
Mikoko Pamoja(ACES/ Mangrove avoided deforestation, Restoration)
Tahiry Honko(Blue Ventures /Mangrove avoided deforestation, Restoration)
Vanga Blue Forest(ACES/Mangrove avoided deforestation, Restoration)
Vanga Blue Forest(ACES/ Seagrass conservation)
Mikoko Ujamaa(Women Against Poverty/ Mangrove avoided deforestation, Restoration)
Taab Che(Resiliencia Azul/ Mangrove avoided deforestation, Restoration)
Restoration of Abandoned or Under-utilized Shrimp Farms to Mangroves on Village Owned
Land in Southeast Sulawesi (Yayasan Bunga Bakau /Mangrove Restoration)
Restoration and Protection of Mangroves and Blue Carbon Ecosystems in North Yucatan(CINVESTAV, Sociedad Cooperativa Tulum Sostenible/ Mangrove restoration)
Restoration of Mangroves Removed for Shrimp Farms and Firewood in the Gulf of Fonseca(Mangrove restoration / Instituto de Conservacion Foresta Servimos por Naturaleza,
CODDEFFAGOLF)

Tanzania
MexicoIndonesia
MexicoHonduras

Approved
2020
Approved
2021
Approved
2021
Approved2021

1426 ha
10,080ha
4487 ha700 haApproved2022

1400 hab) Verified Carbon Standard (VCS) (later Verra)
In 2015, the Verified Carbon Standard (VCS) published a methodology (VM0033) that can be adapted to the restorationof seagrass beds and saltmarshes. In September 2020, Verra extended the methodology to the conservation of wetlands(revised VM0007). VM0007 has been used to register the world’s first project on the conservation of mangrove
ecosystems, including sediments, in Cispatá in the Gulf of Morroquillo, Colombia; the project is supported byConservation International and Apple. In May 2021, Apple purchased 17,000 tons of CO2 equivalents (t-CO2e) to offset its
comprehensive carbon footprint for fiscal year 2020. In 2022, a 60-year conservation and regeneration project for
350,000 ha of mangrove forests in Sindh Province, Pakistan, was verified by Verra. Table 5.2 presents the BC projects of
Verra.
Table 5.2. VCS Certified and under processed (project approved only) Blue Carbon Projects List
Project (Lead Organization/Activity)
India Sundarbans Mangrove Restoration(Livelihoods Fund, Danone/Mangrove restoration)
Cispatá Bay(Conservation International / Mangrove avoided deforestation)
Community-based Avoided Deforestation Project Guinea-Bissau(Bio Guinea Foundation/Mangrove avoided deforestation)
Magdalena Bay(Marvivo/Mangrove avoided deforestation, restoration)
Delta Blue Carbon(Indus Delta Capital/Mangrove avoided deforestation, restoration)

Country

Date

Project size

India

2015

4675 haColombia

2021

11,000 ha

Guinea- Bissau

2021

35,927 ha

Mexico2022

222,000 ha

Pakistan

2022~350,000 hac) Blue Carbon Credits in Japan 167
The three BC credits have been issued in Japan (Table 5.3).
Table 5.3. Current blue carbon (BC) credit schemes
Name (Developer andsecretariat / Year)
Yokohama BC Credit(Yokohama City/2015)

Estimated project budget& Trading amount
5,600,000 JPY (2020)
120.3 t CO2 (2020)

VVB

ApproverNot
establishedYokohama City

Fukuoka BC Credit(Fukuoka City/2019)
J-Blue Credit (JBE approved
by GoJ/2021)

1,850,000 JPY (2020)
43.4 t CO2 (2021)
990,000 JPY (2021)
22.8 t CO2 (2021)

Not
establishedEstablishedwith JBE

Fukuoka City
JBE

Project activities
Seagrass meadows (Tier 1)
Macroalgal beds
Macroalgae aquaculture
Seagrass meadows (Tier 3)
Macroalgal beds
Seagrass meadows (Tier 3)
Macroalgal beds

167 Tomohiro Kuwae, Atsushi Watanabe, Satoru Yoshihara, Fujiyo Suehiro, Yoshihisa Sugimura(2022). Implementation of blue carbon offset crediting for seagrassmeadows, macroalgal beds, and macroalgae farming in Japan. Marine Policy, Volume 138, 104996.

53

In Yokohama and Fukuoka projects, the BC offset credit scheme is based on the IPCC Guidelines, which outline
methodologies for calculating the CO2 sink capacity of BC ecosystems (mangroves, tidal marshes, and seagrass meadows)
and are based on compilations of domestic and international data. Furthermore, in line with the IPCC Guidelines, thesemethodologies can be used to estimate the CO2 sink capacities of macroalgal beds and tidal flats throughout Japan.
JBE, established in 2020, has created a system called J-Blue Credit and is promoting demonstrations, such as Blue Carbon
Credit audits, certification, trading, and offsets; FY2020 has one project, but the number is gradually expanding to 4 and21 projects in FY2021 and FY2022, respectively. The number of projects is gradually increasing from 1 in FY2020 to 4 and21 in FY21 and FY22, respectively. Established methodologies are subject to continuous review and revision by JBE,
whereas the methodologies of many domestic and international credit schemes are nearly fixed. A flexible scheme inwhich methodologies are reviewed and revised considering the rapid progress in science and technology (e.g., area
determination using aerial and above-water sailing drones and remote sensing) should improve certainty and reduce
costs. However, project management may become increasingly difficult. Simplifying methodologies should help facilitate
cost reductions and efficient project development, particularly for small-scale projects, and move the carbon market
forward.

(d) Limitations of the size and number of the Blue Carbon Project
New guidance for BC first presents the methodology for conserving BC approved under any major greenhouse gas
program released in September 2020 by Verra. Only a few projects have been launched to date. By 2020, five projects
were registered under approved methodologies, and all five projects are small scale: compared to 2.4 million tCO2e forother NbS using international standards, the current average project size is 0.3 million tCO2e over the project lifetime.
Blue carbon credits are still small in number and scale compared to green carbon credits and is approximately onehundredth as large in 2020 (Figure 5.5).
35.0

0.3

30.0
25.0
0.2
20.0

0.1

10.0
5.0
0.0

32.4

0.1

15.0

0.1
0.4

1.4

1.9

2.9

2010

2011

2012

2013

9.4

2014

25.2

0.1

0.1

7.7

8.5

2015

2016

Green (terrestrial) carbon projects (credits retired)

20.8
14.0

2017

2018

2019

2020

Blue-carbon projects (credits issued)

Figure 5.5. Carbon credits issued or retired for nature-based solutions, MtCO2 168
Nature-based credits are in especially high demand: Forestry and land use transactions more than doubled between 2020
and 2021 with the strengthening of the transparency and quality. Increasing demand for carbon removals has resulted inprice increases for these credits. The VCM continues to be strongly diverse, with purchasers placing widely different
values on characteristics, such as sector, geography, and perceived co-benefits.
If additional evidence of carbon fixation by macroalgae accumulates in the future, then revising the wetland guideline
168 American Carbon Registry; Catherine E. Lovelock and Carlos M. Duarte, 2019; Climate Action Reserve; The Gold Standard; Plan Vivo; Verra

54

based on such evidence may be an option. The UNFCCC should make a request to the IPCC under the agreement of eachcountry, and the IPCC should develop a methodology by experts.
Box 3. Discussion on blue carbon project requirements(1) Project Boundarya) Temporal Boundaries(I) Peat depletion time (PDT)
Drained peat is subject to oxidation and subsidence and areas with peat at t = 0 may lose all peat before the end of
the crediting period. The time at which all peat has disappeared or that at which the peat depth reaches a level where
no further oxidation or other losses occur (e.g., at the average water table depth) is referred to as the PDT.
(II) Soil organic carbon depletion time (SDT)
Projects that do not quantify reductions of baseline emissions (i.e., those which limit their accounting to GHG removals
in biomass and/or soil) need not estimate SDT. SDT for a stratum in the baseline scenario limits the period when the
project is eligible to claim emission reductions from restoration and is estimated at the project start date for eachstratum.
SDT is conservatively set to zero for project sites drained more than 20 years before the project start date. SDT is
also conservatively set to zero, wherein significant soil erosion occurs in the baseline scenario. Considering theestimation of SDT, the accretion of sediment in the baseline scenario is conservatively excluded.
b) Geographic Boundaries
The project proponent must define the geographic boundaries of the project area at the beginning of project
activities. The project proponent must provide the geographic coordinates of lands (including subtidal seagrassareas, where relevant) included in the project area to facilitate accurate delineation of the project area. Remotelysensed data, published topographic maps and data, land administration and tenure records, and/or other official
documentation that facilitates clear delineation of the project area must be used.
When describing physical project boundaries, the following information must be provided for each discrete area:
Name of the project area (including compartment numbers, local name (if any)):
Unique identifier for each discrete parcel of land:
Map(s) of the area (preferably in digital format):
The project area must be georeferenced and provided in digital format according to VCS rules:
Total area:
Details of land rights holder and user rights.
Land tenure and its intersection with the BC market, such as who “owns” the BC and who has the right to transact
carbon credits for a given BC project (the landholder, the project developer, Indigenous groups, or thenational/subnational government), is complicated. For example, mangroves often straddle the boundary between
privately owned and state-owned land, and seagrasses and macroalgae can exist beyond exclusive economic zones orwithin countries with conflicting state and national laws.

(I) Ineligible wetland areas
For projects quantifying CO2 emission reductions, project areas that fail to achieve a significant difference incumulative carbon loss over a period beyond the project start date are ineligible for crediting based on the reductionof baseline emissions. Thus, these areas must be mapped.
The maximum quantity of GHG emission reductions, which may be claimed from the soil carbon pool, is limited to thedifference between the remaining soil organic carbon stock in the project and baseline scenarios after years (total
stock approach) or the difference in cumulative soil organic carbon loss in both scenarios over a period of years
since the project start date (stock loss approach).

55

Box 4 Case of Australia
In Australia, tenure issues have been overcome to some extent through contractual agreements whereby parties
agree where carbon ownership lies irrespective of underlying property-based rights.
To generate ACCUs from the coastal wetland ecosystems, including the supratidal forests, saltmarshes, mangroves,and seagrass Australian government identified “Carbon Credits (Carbon Farming Initiative-Tidal Restoration of BC
Ecosystems) Methodology” as the first BC methodology determination in 2022 and restricted by “The Carbon Credits(Carbon Farming Initiative) Act 2011.” For completeness, the National Inventory Report is not incorporated byreference. Factors have been derived from that document; thus, they have been set out in a manner that does not
require reference to the National Inventory Report.
The key features of the determination are as listed.
1
The project proponents must remove or modify one or more tidal restriction mechanisms to introduce
tidal flow to their project area and use, remove, modify, install, or construct additional necessary
infrastructure or drainage infrastructure to manage the subsequent extent of tidal inundation.
2
The land is eligible to be included in a tidal restoration project if either:
tidal flow has been excluded or impeded from the land by one or more tidal restriction mechanisms
for at least seven years immediately before the project registration application was submitted, or
tidal flow has been excluded from the land due to reasons other than a tidal restriction mechanism forat least seven years immediately before the project registration application was submitted and by
conducting the eligible project activities the land will be inundated during the 25 year crediting period.
3
The project proponents are required to undertake hydrological mapping as part of the projectregistration process to ascertain consent and regulatory approval requirements and potential adverse
impacts.
4
The project proponents must not conduct prohibited activities and must conduct restricted activities
only in accordance with the determination.
5
The project proponents can estimate carbon abatement at intervals of 6 months to 5 years using amodeled approach via the Blue Carbon Accounting Model. No sampling is required under thedetermination.
6
The determination applies discounts to account for the risks that carbon sequestered by a tidal
restoration project is not maintained, or that the coastal wetland biomass that establishes due to themigration of project outside the project area over time.
Particularly, Section 10 (Project Area) and Section 11 (Duty to disclose information relating to project to owners andrelevant landholders) of the methodology symbolizes determination.
Section 10 (Project Area)
Section 10 sets out the requirements for determining the boundaries of a project area.
Subsection 10(1) requires that all land identified as impacted land by the project start tidal inundation map (prepared as part of
the hydrological assessment) is included in the project area.
Subsection 10(2) requires that the project area must include eligible land.
Subsection 10(3) clarifies that the project area may also include areas of land that are ineligible provided that these areas of land
will not be included in CEAs for the project.
Section11 (Duty to disclose information relating to project to owners and relevant landholders)
Section 11 sets out the requirements for project proponents to provide written notices to owners and relevant landholders of land
identified by a permanence period tidal inundation map (prepared as part of the hydrological assessment) as land that will be
impacted by tidal inundation arising from the eligible project activities (referred to in the Determination as “impacted land”).
Paragraph 11(2)(a) requires that a notice is provided between 35 and 40 days of the commencement of the removal or modificationof a tidal restriction mechanism in accordance with paragraph 7(2)(a). This requirement is intended to ensure that relevant
landholders are aware when tidal inundation will occur and are provided with sufficient notice to allow any preparations to be
made. Paragraph 11(2)(b) outlines the information required to be included in the notification.
The effect of subsection 11(3) is that for the duration of the permanence period for the project, the project proponent must takereasonable steps to inform themselves of the owners and relevant landholders of all land outside the project area that is identified
as future impacted land by the most recent permanence period tidal inundation map prepared or revised for the project.
Subsection 11(4) requires project proponents to provide anyone identified under subsection 11(3) with information about the
project.
The intent of subsections 11(3) and 11(4) is to ensure that when a change of ownership or operational control of land is identified
as future impacted land, the new owner and relevant landholder are provided with adequate information regarding the project
within a reasonable timeframe.

56c) Carbon Pools
Carbon pools may be deemed de minimis and do not need to be accounted for if the omitted decrease in carbon
stocks or increase in GHG emissions jointly amounts to less than 5% of the total GHG benefit generated by the
project.
(2) Baseline Scenarioa) Reassessment of the Baseline Scenario
The historic reference period must be extended for this reassessment to include the original reference period andall subsequent monitoring periods up to the beginning of the current monitoring period.
Activity data (in the context of sinks, data on changes in area over time) are unavailable. Absorption and emissions
from mangrove forests, salt marshes, and seagrass beds, which are currently considered major BC ecosystems, canbe calculated if activity data are available in addition to the Tier 1 absorption factors provided in the wetland
guidelines. When countries calculate GHG absorption emissions, many international data are currently used inaddition to domestic data to determine the amount of activity. For example, for energy use, the International Energy
Agency Energy Balance Table, FAO (Food and Agriculture Organization of the United Nations) International Statistics
Database FAOSTAT55 provides data over time. Even if data for a country are lacking, calculating the Tier 1 level ispossible using international data as the amount of activity. However, for BC ecosystems, no such international
statistics exist, and the creation of data on activity amounts is left entirely to the self-help efforts of individual
countries.
Guidance for countries for BC calculation and its incorporation into their NDCs has been published by the Blue
Carbon Initiative, and support for methodology development, including data preparation methods, is graduallystrengthened. In addition, there are moves toward the development of international data on salt marshes, such as
the provision of global data on the area of salt marshes.
(3) Additionality 169
The project must ensure that the carbon credit project takes place outside of mandated protections, such as nationallaws, regulations, or other government policies, to demonstrate additionality. A project is additional if (1) it would
not have been undertaken without the carbon credit incentive and (2) the benefits (including carbon sequestration)
would not have been realized without the project.
Conservation is less costly and provides a large amount of credits because of the considerable amount of protectedcarbon stocks. However, similar to other conservation credit projects, proving additionality in conservation projects
can be difficult because the absence of m negative impacts due to the project intervention must be demonstrated.
In conservation projects, establishing baselines and additionality usually involves an analysis of the causes, rates,and patterns of deforestation, degradation, and wetland conversion. Many BC ecosystems face factors of loss caused
upstream (e.g., sedimentation and water quality degradation). These factors are often difficult to measure or include
in predictions.
In restoration projects, baselines must consider removed emissions (carbon that is taken up as ecosystems arerebuilt, also known as removals) and avoided emissions. If a BC ecosystem is destroyed, then avoided emissions
must be considered because carbon-rich soils can emit carbon for up to 20 years. The amount of avoided emissions
depends on when the intervention is made for the initial destruction. If the project starts after all the carbon in thesoil has been emitted, then the counterfactual hypothetical baseline would have zero avoided emissions, similar toa reforestation project.
(4) Quantification of GHG Emission Reductions and Removalsa) Baseline Emissions
Emissions in the baseline scenario are attributed to carbon stock changes in biomass carbon pools, soil processes, or a
combination of these factors. In addition, emissions from fossil fuel use may be quantified where relevant.
169 https://merid.org/wp-content/uploads/2022/11/HQBC-PG_FINAL_11.8.2022.pdf (accessed on January 8, 2023)

57

Estimation of GHG emissions and removals related to the biomass pool is based on carbon stock changes. Estimation of
GHG emissions and removals from the SOC pool is based on either various proxy (e.g., carbon stock change, water table
depth) or through the use of literature, data, or default factors or models.
Assessing GHG emissions in the baseline scenario includes determining GHG emission proxies/parameters andevaluating their pre-project spatial distribution, constructing a time series of the chosen proxies/parameters for eachstratum for the entire project crediting period, and determining annual GHG emissions per stratum for the entire projectcrediting period.
Current development patterns and plausible future land use changes must be mapped to a scale sufficient to estimate
GHG emissions from the baseline scenario. Particular attention must be provided to existing or future construction of
barriers to tidal and/or river hydrology and sediment supply from rivers and/or along the coast, as well as barriers thatwill impair wetland capacity to migrate landwards with sea level rise.
In the case of abandonment of pre-project land use in the baseline scenario, the project proponent must consider
nonhuman induced hydrologic changes induced by collapsing dikes or ditches that would have naturally closed overtime and progressive subsidence, leading to rising relative water levels, increasingly thin aerobic layers, and reduced
CO2 emission rates. Regarding infrastructure impediments to tidal hydrology, the baseline scenario must consider thecurrent and historic layout of any tidal barriers and drainage systems to derive trends in tidal wetland evolution.
Historic information on the preexisting channel network as determined by aerial photography may serve to set trends
in post-project dendritic channel formation in the field. Derivation of such trends must be performed on the basis ofhydrologic modeling using the total tidal volume, soil erodibility, and/or expert judgment. Considering hydrological
functioning, the baseline scenario must be restricted by climate variables and quantify any impacts on the hydrological
functioning as caused by planned measures outside the project area (e.g., dam construction or further changes inhydrology, such as culverts) by demonstrating a hydrological connection to the planned measures.
Natural plant succession, based on the assessment of changes in water table depth, a time series of vegetation
composition must be derived ex ante according to vegetation succession schemes in the baseline scenario from scientific
literature or expert judgment. For example, diked agricultural land will undergo natural plant succession to forests,
freshwater wetlands, tidal wetlands, rank uplands, or open water based on the land use trajectory scenario, inundation
scenario, proximity to native or invasive seed sources, plant succession trajectories of adjacent natural areas, or possible
maintenance consistent with projected future human land use (e.g., pasture, lawn, landscaping).
GHG emissions from disturbed carbon stocks in stockpiles (originating from piling, dredging, and channelization) exposed
to aerobic decomposition must be accounted for in the baseline scenario.
The baseline scenario may involve the construction of levees to constrain flow and flooding patterns, the constructionof dams to hold water, and/or upstream changes in land surface, leading to intensified runoff. In such cases, the project
proponent must account for hydrological processes that lead to increased carbon burial and GHG reductions within the
project area using procedures provided in this section.
The subsections below provide guidance considering the methods which may be used to estimate net GHG emissions
from soil in the baseline scenario. Project proponents may choose the most suitable method for their project
circumstances and data availability. However, default and emissions factors cannot be used in the presence of
published data suitable for use in the project area.

b) Project Emissions

Emissions in the project scenario are attributed to carbon stock changes in biomass carbon pools, soil processes, or a
combination of these factors. In addition, emissions from organic soil burns and fossil fuel use may be quantified where
relevant.
The long-term average carbon stock must be calculated for the baseline and the project scenario. For projects
undertaking even-aged management, the time period n, over which the long-term average GHG benefit is calculated,
involves at minimum one full harvest/cutting cycle, including the last harvest/cut in the cycle. For projects underconservation easements with no intention to harvest after the project crediting period (which must be shown in the58

project description based on verifiable information), or in case of selective cutting, the time period n, over which thelong-term average is calculated, is the length of the project crediting period.

Measurements of carbon burial rates show high site-specific variability, which are strongly affected by a wide range
of environmental factors for mangroves (Adame et al., 2017; Schile et al., 2017), seagrasses (Lavery et al., 2013),
and salt marshes (Kelleway et al., 2017b).
The reliable determination of sediment accumulation rates is a key consideration, with associated uncertainties
only partially reflected in the McLeod et al. (2011) estimates presented above. Geochemical-based studies haveindicated that seagrass carbon burial may have been markedly overestimated (Johannessen and Macdonald, 2016).
These issues are contentious (Johannessen and Macdonald, 2018a; Johannessen and Macdonald, 2018b;
Macreadie et al., 2018; Oreska et al., 2018); their scientific resolution is highly desirable.
Lateral transfers are ineffectively quantified. Some of the carbon stored in coastal marine sediments may berecalcitrant carbon from terrestrial or atmospheric sources (and should therefore be excluded) (Chew andGallagher, 2018), but export of DOC, inorganic carbon, and alkalinity may be considered as additional sequestration(Maher et al., 2018; Santos et al., 2019). Even if well-protected, the permanence of vegetated coastal systems
cannot be assumed under future temperature regimes (Ward et al., 2016; Duke et al., 2017; Jennerjahn et al.,2017; Nowicki et al., 2017).
Responses to future SLR are also uncertain and complex (Spencer et al., 2016). However, impacts are notnecessarily negative: carbon sequestration capacity may increase where totally new habitats are created (Barnes,2017) or if salt marshes are replaced by mangroves (Kelleway et al., 2016).
Overall, a combination of conservation and restoration of mangroves, salt marshes, and seagrass habitats cancontribute to national mitigation efforts for those countries with relatively large coastlines where such ecosystems
naturally occur (Atwood et al., 2017). However, the associated current uncertainties in quantifying relevant carbon
storage and flows are expected to be problematic for reliable measurement, reporting, and verification.
c) Emission Reduction
Emission reductions are estimated using a conservative default factor based on fire occurrence and extension in
the project area in the baseline scenario. This method avoids the need for direct assessment of GHG emissions
from fire in the baseline and the project scenarios.
d) Leakage of Blue Carbon Project
For climate change mitigation, impacts outside the boundary (e.g., activity-shifting leakage, market leakage,
ecological leakage, and emissions upstream and downstream (life cycle) of business activities) are generally
assumed to be zero unless significant impacts are observed.
The vast potential of nascent BC NbS is offshore, occasionally overlapping and context-dependent jurisdictions andpublic domains that lack straightforward carbon rights concepts for private property.
The ecological leakage may be achieved by a project design, which causes no alteration of mean annual water table
depths or flooding frequency or duration in adjacent areas or limiting such alteration to levels that do not influence
GHG emissions. In tidal wetland restoration projects, dewatering downstream wetlands is unexpected if project
areas are set sufficiently large to include expected areas of changed hydrology. Procedures for monitoringalterations of water table depth at the project area. The tidal range and sediment delivery experienced by wetlands
outside the project area must remain within the system tolerance, which is defined by the high and low tides andregional sediment budget and assessed using hydrological models (and/or empirical analysis) and expert judgment.

59

Table 5.4. Processes Associated with Ecological Leakage Outside Project Boundary
and Related Criteria for their Avoidance 170
Ecological leakage process outside project boundary
Lowering water table that causes increased soil carbon
oxidation
Lowering water table that causes increased N2O emissions
Raising water table that causes increased CH4 emissions
Raising water table that causes decreased vegetation
production that causes decreased new soil carbon
sequestration

Avoidance criterion
Maintain wetland conditions (e.g., converting fromimpounded water to a wetland does not cause soil oxidation)
No conversion of non seagrass wetland to open water
No conversion of non wetland to wetland
No causation of vegetated to no vegetated (or poorly
vegetated) conditionse) Net GHG Emission Reductions and Removals(I) Calculation of net GHG emissions reductions
The total net GHG emission reductions project activity is calculated as follows:
NER RWE = GHGBSL − GHGWPS + FRP − GHGLKNERRWE = Net CO2e emission reductions from the RWE project activity; t CO2e
GHGBSL = Net CO2e emissions in the baseline scenario; t CO2e
GHGWPS = Net CO2e emissions in the project scenario; t CO2e
FRP = Fire Reduction Premium (net CO2e emission reductions from organic soil combustion due to rewetting
and fire management); t CO2e
GHGLK = Net CO2e emissions due to leakage; t CO2e
For projects claiming reductions of baseline GHG emissions or for conservation and restoration projects where sea
level rise may cause a loss of tidal wetland and/or soil organic carbon stocks, the maximum quantity of GHG
emission reductions or removals that may be claimed from the biomass and soil organic carbon pool is limited to
the net GHG benefit generated by the project years after its start date.
(II) Estimation of uncertainty
The estimation of uncertainty of emissions and carbon stock changes (i.e., for calculating a precision level and any
deduction in credits for lack of precision following project implementation and monitoring) must be justified byusing a conservative precision. Levels of uncertainty must be known for all aspects of baseline and project
implementation and monitoring.
Estimated carbon emissions and removals arising from BC activities have uncertainties associated with themeasures and estimates of several parameters. These parameters include the project area or other activity data,carbon stocks, biomass growth rates, expansion factors, and other coefficients. Either as default factors given in
the IPCC Guidelines (2006), IPCC-GPG-LULUCF (2003), expert judgment, or estimates based on sound statisticalsampling, the uncertainties associated with the estimates of various input data are assumed to be available.
Applying this procedure at an early stage to identify the data sources with the highest uncertainty is good practice
to conduct further work to diminish uncertainty.
(III) Calculation of Verified Carbon Units
The project proponent must consider the number of buffer credits, which must be deposited in the pooled buffer
account, to calculate the number of verified carbon units. The number of buffer credits, which must be depositedin the pooled buffer account, is based on the net change in carbon stocks.
The percentage of buffer credits to be contributed to the pooled buffer account must be determined by applying
each mechanism tool similar to the VCS AFOLU Non-Permanence Risk Tool.
(5) Other Issues(a) Cost Effectiveness170 VERRA “VM0033 Methodology for Tidal Wetland and Seagrass Restoration v2.0” (2021)

60

Restoration costs could also be an important constraint for large-scale application. Based on published data from246 observations, Bayraktarov et al. (2016) estimated median total costs for restoration of one hectare ofmangrove, salt marsh, and seagrass habitat to be ~2508, 151,129, and 383,672 in 2010 USD. Each ecosystem had
high variability in costs according to the economy of the country where the restoration projects were conducted,
and the restoration technique was applied. Assessment of coastal conservation and restoration costs is also given.
(b) Lack of historical data
National governments, international research agencies, and local universities can provide basic forestry
information, namely suitable species, management regimes, growth rates, and market information.
In the case of USA tidal wetland and seagrass restoration VCS project, no complete national data sets exist for either
tidal wetland loss or restoration in USA for OA 171 and MAP 172, and conservative approximations can be made byexamining the data from several sources. All US estuaries face a common set of barriers to tidal wetland restoration,
including insufficient funding, lack of willing landowners and community support, and physical and ecologicallimitations and changes, such as sea level rise (Vigmostad et al 2005). The critical need to provide funding forestuary habitat restoration, including tidal wetlands, and help counter the mentioned socioeconomic factors wasrecognized in 2000. The United States Congress passed, and President Clinton signed into law, The Estuary Act of
2000, which was passed by the United States Congress and signed into law by President Clinton, authorized $275
million over five years for restoration activities. Seagrass meadow restoration also occurs at a remarkably low level
relative to its maximum adoption level provided by the NOAA 2014).
Box 5: Case of USA(Time Period)
The time period selected for determining the OAy is 2000 to 2013 for the following reasons.
The NEPs began reporting annual activities in 2000 and have been required to do so since 1993 by theGovernment Performance Results Act. The NEP database captures activities before 2000 as well as those from2000 forward.
The Estuary Restoration Act was signed into law in 2000. This act made restoring estuaries a national priority andrepresents a recognition of the growing importance of estuary habitat restoration, including tidal wetlands.
Moreover, this act provided funding authorization and appropriations for restoration projects and created afederal interagency council to promote a coordinated federal approach to estuary habitat restoration, forge
effective partnerships among public agencies and between the public and private sectors, provide financial andtechnical assistance for estuary habitat restoration projects, and develop and enhance monitoring and researchcapabilities. Before 2000, the lack of interagency coordination created sporadic and uncoordinated restoration
actions.
Th community-based Restoration Program of NOAA was created in 1999 within its Restoration Center and beganfunding projects that year with only $500,000 in funding. The creation of this national center for restoration also
indicates that a turning point for restoration was anticipated at that time. Since then, annual funding of NOAA for
restoration has exceeded over 10 million dollars.
RAE was established in 1997 as a national umbrella organization for regional nonprofit organizations. These
organizations identified estuary restoration as an emerging opportunity and established RAE to promote estuary
restoration at the national level and provide financial support for new restoration activities. The creation of RAE
at this time reflects the need for a national voice to catalyze increased investment in estuary restoration.
Collectively, these milestones represented a sea change in the restoration community, which has markedly
increased funding and capacity for restoration activities since the year 2000. Therefore, the time period 2000 to2013 will capture the preponderance of restoration activities.

171 Observed adoption of the project activity. In the project, OA (of tidal wetland restoration excluding seagrass meadows) + OA (of seagrass meadow
restoration); The average annual aggregate of tidal wetlands restored from 2000 to 2013 as reported by the 28 National Estuary Programs (NEPs) and theirpartners in the U.S. Environmental Protection Agency (measured in acreage) and expanded to include restoration activities that occur in a U.S. estuary that is
not an NEP + The percentage of seagrass meadow restoration projects compared to other estuary restoration projects funded by NOAA since 2000.
172 Maximum adoption potential of the project activity. In the project, MAP (of tidal wetland restoration excluding seagrass meadows) + MAP (of seagrassmeadow restoration): A portion of the 1991 100-year Coastal Floodplain as determined by the Federal Emergency Management Agency (FEMA) Past tidal
wetland losses to shallow open water in Louisiana due to coastal erosion + Tidal wetland losses reported by the U.S. Fish and Wildlife Service (USFWS) from1991 to 2013.

61

(Observed Adoption Analysis)
OA for the NEPs was determined through a systematic review of the data sets provided by the EPA for each of the
NEPs. The NEP OA calculation is provided in Table 5.5. Once the NEP OA was determined, it is increased by 50%
for the Activity Penetration calculation (OAy = NEP OAy × 1.5 = 97,422.17 acres × 1.5 = 146,133 acres) to ensure
capture of nonNEP activities.
The NOAA database contains information regarding 2701 habitat projects that have occurred since 2000, and only
120 (4%) are seagrass meadow projects. The database includes numerous habitats (e.g., dunes, in-stream, kelp,
mangrove, and oyster reef) as well as numerous activities in wetland habitats (restoration, invasive species
removal, and marine debris removal). Only a portion of the 120 seagrass meadow projects would meet theapplicability conditions of this methodology. Therefore, including all identified seagrass meadow restoration
projects is conservative. The total acreage of estuary habitat restoration projects in the NOAA database is 49,837
acres. Seagrass meadow projects are typically conducted at a smaller scale than other habitat activities; therefore,
4% of the total acreage attributed to seagrass restoration is a conservative assumption. Hence, the OAy for
seagrass restoration is 4% of 49,837 = 1,993 acres.
(Maximum Adoption Potential Analysis)
An estimate of the available area for tidal wetland restoration must be established to determine MAPy. The
starting point for this estimate is the “Projected Impact of Relative Sea Level Rise on the National Flood Insurance
Program” prepared by the Federal Emergency Management Agency.
Table 5.5. Calculation of OAy for the NEPs
Tidal Wetland Acres Restored
Estuary Program

2009

2010

2011

2012

Peconic Bay Estuary Program
Piscataqua Region Estuaries Partnership
Buzzards Bay National Estuary Program
Tillamook Estuaries Partnership
Mobile Bay National Estuary Program
Santa Monica Bay Restoration Commission
Tampa Bay Estuary Program
Delaware Center for the Inland Bays
Lower Columbia River Estuary Partnership
Indian River Lagoon National Estuary
Program
Maryland Coastal Bays Program
Galveston Bay Estuary Program
New York–New Jersey Harbor Estuary
Program
Chesapeake Bay Program
Puget Sound PartnershipCharlotte Harbor National Estuary Program
San Francisco Estuary Partnership
Barataria–Terrebonne Estuary Program
Sarasota Bay Estuary ProgramLong Island Sound Study
Partnership for the Delaware Estuary
Albemarle–Pamlico
National
Estuary
ProgramBarnegat Bay Partnership
Narragansett Bay Estuary Program
Massachusetts Bays Program
Casco Bay Estuary Partnership
Coastal Bend Bays and Estuaries Program
Morro Bay National Estuary Program
One year average, 2009–2012
2000 to 2013 total estimate = 14 × One year
average

3.74
46.00
137.00142.70
26.00
-

44.00
21.00
61.28
4.00
-

12.00
16.00
6.50
184.00

0.05
4.40
2.00
44.54
58.00

3.01
0.94
27.60
36.38
5.25
62.13
7.50
60.50

1,395.75

21.26

419.00140.30494.0864.43
158.001.80
46.81

104.00407.06

189.009.00

89.81
155.22

11.00

34.00

65.80

50.00

40.20

622.001,277.00
600.501,469.00
673.58516.0058.65
1.30

1,005.00
140.00496.00401.00
n/a
88.00
6.50

3,775.00
505.40795.003,250.00
35.00
30.00
42.56
-

n/a
101.00140.00983.36
182.005.00
137.70-1,800.67
505.85507.88
1,525.84
296.86137.75
81.73
1.95

1.10

4.00

84.20

0.31

22.40

63.00
1,442.00
1,597.00
n/a

58.00
133.00568.00n/a

54.00
351.00
n/a

21.00
21.80
72.00
n/a

30.25
412.505.45
647.00n/a
6,958.73

4 Year average

97,422.17

62

FEMA calculated the area of coastal floodplain that would flood under a 100-year coastal flood event for 1990 tobe 19,500 mi2 (12,800,000 acres). A 100-year flood event is defined as a flood that statistically has a 1% chanceof occurring in any given year. By definition, the coastal floodplain does not include either upland or existing
wetland areas (wetland areas do not flood because they are already regularly inundated). The coastal floodplain
substantially comprises former wetland areas that were drained and/or filled and converted to other land uses,
such as agricultural, commercial, or residential uses. This area includes only some former tidal wetland areas thatwere diked or drained for agriculture and other uses (some former wetland areas are no longer in the floodplain
because they are now well protected by dikes or levees and therefore are not included in this estimate, which isconservative). Only some of the coastal floodplain areas identified by FEMA are restorable or suitable for wetland
creation. However, 33% of this area (4,224,000 acres) is used as a conservative (low) estimate for establishing an
estimate of MAPy.
The FEMA estimate was made in 1991 and only includes land areas subject to flooding. Therefore, VCS are also
included in the MAPy tidal wetland losses since 1991 and tidal wetlands that have drowned or converted to open
water in coastal Louisiana. All these areas are virtually suitable for tidal wetland restoration.
Louisiana wetland losses from 1900 to 1978 are reported to be 901,200 acres (US Department of the Interior
1994). The MAPy estimate does not include Louisiana coastal wetland losses between 1978 and 1986; thus,
excluding this area from the MAPy is conservative.
Tidal wetland losses from 1986 to 1997 were reported to be 8450 acres (Dahl 2000). The 1991 to 1997 portionof these losses is assumed to be 4225 acres, a prorated portion of the total.
Tidal wetland losses from 1998 to 2004 were reported to be 32,400 acres (Dahl 2006). Tidal wetland losses from2004 to 2009 were reported to be 124,290 acres (Dahl 2011).
Data for 2010 to 2013 (four years) are unavailable. We apply the average rate of loss from the previous five-year
period, that is, 2004 to 2009, which is 124,290 acres / 6 years = 20,715 acres/year.
Table 5.6. Calculation of Maximum Adoption Potential for tidal wetland restoration (non-seagrass)Maximum Adoption Potential
33% of FEMA 1991 Floodplain Estimate
Louisiana Delta Wetland Losses
Tidal Wetland Losses 1991 to 1997
Tidal Wetland Losses 1998 to 2004
Tidal Wetland Losses 2004 to 2009
Tidal Wetland Losses 2010 to 2013
Total MAPy (non-seagrass)Acres
4,244,000
901,200
4,228
32,400124,290
82,8605,388,978Waycott et al. (2009) demonstrated that seagrass meadow habitat losses in the US were 853,845 acres between
1937 and 2006. The primary causes of the loss of seagrass meadows, which include sediment deposition,
declining water quality, scarring from vessels, and disease, are typically reversible. Therefore, all areas
documented as lost are restorable. Therefore, MAPy for seagrass meadow restoration is 853,845 acres.
(Conclusion)
This project provides the following conclusion based on the presented results: the (1) Activity Penetration
Calculation for Tidal Wetlands (non-seagrass): 2.71%; OAy; 146,133 acres/MAPy; 5,338,978 acres and (2) Activity
Penetration Calculation for Seagrass Restoration: 0.2%; OAy; 1993/MAPy; 853,845(c) Complex Transaction
National and local governments can ensure that regulations do not unduly restrict forest management and harvest
activities, especially in circumstances where managers subscribe to internationally recognized third-party ESG
certification. The regulations should be well defined, enforced transparently, and applied equally to domestic andinternational owners.
The benefits of including BC investments must exceed the transaction costs of making these investments.
Understanding BC investments is complicated. Few investment personnel will have a specific personal education in
the field, which is characterized by specialized and often impenetrable terminology. General workers and consultants
63

typically have no knowledge of the field; therefore, obtaining adequate knowledge to provide informed advice isexpensive. Plan leadership and boards are justifiably uncomfortable investing in an asset class they do not fully
understand; for example, anticipated BC returns are typically reported on a real, unlevered basis, while the practicein the broad private field is to report anticipated returns on a high nominal and levered basis.

64

Recommendations
The discussions have been summarized, and the short-term (next few years) to long-term (up to 25 years or so) roadmap
and barriers to be cleared are summarized in Table 6.1 below for science, technology, economics, and policy aspects.
Table 6.1. Roadmap toward blue carbon implementation
Short-term (1–3 years) by
2025

Mid-term (2–7
years) until 2030

Long-term(5–25
years) until 2050

Science•Establish scientific evidence ofmacroalgal BC, especially interms of the long-term storage
potential.
•Other wetland data tailored toeach country (IPCC Tier 2) will
be developed.

•Supplement to IPCC
Guidelines or otherinternational rules
will be updated.
•Visualization methodof co-benefits of BC
ecosystems, such as
biodiversity, will be
developed.

•Visualization method of
co-benefits of BC
ecosystems, such as
biodiversity, will be
developed (cont’d).
•Environmental impact
assessment (EIA) of
macroalgal farming inscale.

Technology•Low-cost sensors (hyperspectral, multispectral, Lidar, UAV,
satellites, biologging, cloud computing) will be developed;•R&D of various uses of macroalgal material will bepromoted;•Macroalgal farming on multiple scales will bedemonstrated;•High-temperature tolerant seeds and seedlings will be
developed;•Use of herbivores will be developed.

•Large-scale offshore
macroalgal farming will
be demonstrated orcommercialized.

Economy•Additional projects on BC
Credits on domestic VCM will
be developed.

•Additional projects
on BC Credits on
domestic andinternational
markets (VCM andpost-CDM) will be
developed.

•Credit mechanisms thatconsider co-benefits (e.g.,
biodiversity credits) will
be demonstrated.
•Commercialization ofmacroalgal products will
be promoted.

Policy(or Social•IPCC AR7 scoping will reflect
macroalgal BC.
•Negotiations to clarify themodalities of Article 6 of theParis Agreement will beconcluded.
•Macroalgae and other BC
ecosystems will beincorporated into national
inventories in many countries.
•Laws and markets for carbon
trading in each country will be
developed.
•Registry mechanisms to avoid
double counting andoverselling (use of blockchain
technology) will be developed.
•Remarkably ambitious NDCs
reflecting BC (2025) will be
submitted.

•Consistency with theinternational legal
framework for largescale macroalgal
aquaculture will bebuilt under (e.g.,
UNCLOS, CBD, andLondon Protocol);•Consistency withnational laws will bebuilt.
•Capacity on
multidisciplinary
areas will be built
and mobilized.

•Macroalgae will be
included in IPCC wetland
guidelines or otherinternational standards
and rules.

awareness)

Recommendation 1: Answers to Fundamental Questions in Blue Carbon Science
Scientific understanding of the impacts of climate change, particularly sea level rise and climatic disturbance, on the
distribution, carbon sequestration, and carbon stock of BC ecosystems and their geographic variability, is required. Thisknowledge is particularly needed as a factor affecting the permanence of BC. An understanding of the global distribution
area and its changes from past to present is needed to understand the baseline for established BC ecosystems andmacroalgae.
65For the accurate estimation of BC, in-situ CO2 gas exchange between the atmosphere and ocean and inorganic carbon
production, as well as production and sequestration of organic carbon, must be understood. In addition, combining
carbon and nitrogen stable isotopes (13C and 15N), environmental DNA, and high-resolution ocean current models is
crucial to understand the origin of organic carbon. In the context of climate change mitigation, knowledge of the dynamics
of other GHG gases, such as CH4 and N2O, within BC ecosystems, must also be increased.
Many have indicated the diversity and importance of the co-benefits of BC. These co-benefits, especially the effects ofenhancing biodiversity (e.g., fish), are often more important to local residents than the carbon value. Developing a system
to evaluate such co-benefits scientifically and holistically is crucial.
Momentum from the ongoing UN Sustainable Development Goals, the UN Decade of Ocean Science, and the UN Decadeof Ecosystem Restoration should be used to advance the scientific foundation to be built, targeting 2030.
Recommendation 2: Create Blue Carbon Credit projects targeting various ecosystems
Policies, management (conservation, restoration, and creation), and demonstration of BC benefits (including payments)
targeting BC ecosystems are still limited. Projects targeting mangroves have increased but those targeting seagrasses, salt
marshes, and macroalgae are expected to develop. Projects are recommended to develop Tier 2 or higher assessments
using data specific to each country and site. Such assessments in developing countries will be implemented underinternational cooperation and collaboration.
Scientific knowledge, observational techniques, economic incentives, policies, and governance are lacking in some areas,
including that for macroalgae. However, this insufficiency will be partly resolved through effective project implementation,
monitoring, and reporting across sectors. Industry, government, and academia are also expected to work together toincrease the number of high-quality BC credit cases in the VCM. Moreover, trading rules in the international carbon
market must be urgently clarified to be handled under Article 6 of the Paris Agreement, and the value of BC ecosystems
must be fairly shared to return the value to local communities.
Recommendation 3: Development of Technologies Related to the Restoration and Creation of Blue Carbon Ecosystems
BC ecosystems and macroalgal beds have been markedly reduced in areas due to anthropogenic impacts and climatechange, and investment in various technological developments will be necessary to rebuild these ecosystems by 2050
and bring them back to their pre-degradation state. Technology to mitigate land-based pollution, which is the initial causeof degradation, civil engineering methods (such as blue infrastructure) to restore the lost three-dimensionality or rugosity,and seedling production of macroalgae and seagrass species that are adapted to changing environments whileconsidering genetic diversity, will be necessary. In addition, the development of inexpensive sensors, data sharing on thecloud, and the development of automatic image identification technology using machine learning are required to monitor
the outcomes of restoration and creation.
Recommendation 4: Large-scale macroalgal aquaculture projects
Large-scale seaweed farming is expected to be developed not only as a climate change mitigation measure but also in
combination with fish farming and industrial use of the products. Along with R&D by research institutions, medium- tolarge-scale pilot projects in coastal to offshore areas in collaboration with private sector are expected. The transport of
DOC and other forms of carbon to other sinks, such as the deep sea, the development of storage mechanisms andindustrial utilization technologies for the products, and the coordination of ocean utilization with other industries, suchas fishing and shipping (i.e., marine spatial planning, MPA), can be promoted through these projects. Developing various
monitoring technologies would also be possible.
Recommendation 5: Establish international rules related to blue carbon
The IPCC wetland guidelines or similar international standards should be updated to include macroalgal BC and other BC
related findings. Furthermore, considering large-scale macroalgal farming, which has remarkable potential for carbon
sequestration and storage, clarifying how impacts on coastal and deep-sea ecosystems will be handled under the UNCLOS,
CBD, and London Convention based on scientific findings, such as environmental impact assessments (EIA), is necessary.

66

CITATION
Cite report as: Atsushi Watanabe, Tomohiro Kuwae, Carlos M. Duarte, Ryo Kohsaka, Jay Mar D. Quevedo, and Hiromichi
Nagai (2023) Blue Carbon Roadmap: Carbon Captured by the World’s Coastal and Ocean Ecosystems (ICEF Innovation
Roadmap Project)67