A framework for compiling a blue carbon resource balance sheet: integrating physical and value accounts

Operationalizing marketable blue carbon

Abstract. Mangrove forests and seagrass meadows, collectively termed as blue carbon ecosystems (BCEs), play a pivotal role in carbon sequestration and climate mitigation. Blue carbon research enables advancing scientific knowledge and gaining insights into their current state, which is crucial for making informed decisions on its conservation and management practices. The Japan International Cooperation Agency (JICA) launched the “Comprehensive Assessment and Conservation of Blue Carbon (BC) Ecosystems and their Services in the Coral Triangle” or BlueCARES to pioneer joint research on blue carbon ecosystems and formulate conservation strategies at local and national levels. BlueCARES aims to establish a robust Blue Carbon Strategy and initiate the establishment of the Blue Carbon Network (BCnet), convening various stakeholders, including government agencies, local government units, academic institutions, and non-governmental organizations. BCnet organizes summits, workshops, and conferences to facilitate collaboration. Through capacity development initiatives, the project empowers stakeholders to actively engage in field surveys, conservation efforts, and the implementation of the Blue Carbon Strategy, even after the project concludes. This paper narrates the capacity-building engagements made by the Geomatics team, leveraging remote sensing and geospatial technologies to foster sustainable blue carbon management practices and ensure the long-term resilience of BCEs in the country.

Blue carbon has made significant contributions to climate change adaptation and mitigation while assisting in achieving co-benefits such as aquaculture development and coastal restoration, winning international recognition. Climate change mitigation and co-benefits from blue carbon ecosystems are highlighted in the recent Intergovernmental Panel on Climate Change Special Report on Ocean and Cryosphere in a Changing Climate. Its diverse nature has resulted in unprecedented collaboration across disciplines, with conservationists, academics, and politicians working together to achieve common goals such as climate change mitigation and adaptation, which need proper policy regulations, funding, and multi-prong and multi-dimensional strategies to deal with. An overview of blue carbon habitats such as seagrass beds, mangrove forests, and salt marshes, the critical role of blue carbon ecosystems in mitigating plastic/micro-plastic pollution, as well as the utilization of the above-mentioned blue carbon resources for biofuel production, are critically presented in this research. It also highlights the concerns about blue carbon habitats. Identifying and addressing these issues might help preserve and enhance the ocean’s ability to store carbon and combat climate change and mitigate plastic/micro-plastic pollution. Checking out their role in carbon sequestration and how they act as the major carbon sinks of the world are integral parts of this study. In light of the global frameworks for blue carbon and the inclusion of microalgae in blue carbon, blue carbon ecosystems must be protected and restored as part of carbon stock conservation efforts and the mitigation of plastic/micro-plastic pollution. When compared to the ecosystem services offered by terrestrial ecosystems, the ecosystem services provided by coastal ecosystems, such as the sequestration of carbon, the production of biofuels, and the remediation of pollution, among other things, are enormous. The primary purpose of this research is to bring awareness to the extensive range of beneficial effects that can be traced back to ecosystems found in coastal environments.

Plastics in blue carbon ecosystems: a call for global cooperation on climate change goals

Photoautotrophic marine ecosystems can lock up organic carbon in their biomass and the associated organic sediments they trap over millennia and are thus regarded as blue carbon ecosystems. Because of the ability of marine ecosystems to lock up organic carbon for millennia, blue carbon is receiving much attention within the United Nations' 2030 Agenda for Sustainable Development as a nature-based solution (NBS) to climate change, but classically still focuses on seagrass meadows, mangrove forests, and tidal marshes. However, other coastal ecosystems could also be important for blue carbon storage, but remain largely neglected in both carbon cycling budgets and NBS strategic planning. Using a meta-analysis of 253 research publications, we identify other coastal ecosystems-including mud flats, fjords, coralline algal (rhodolith) beds, and some components or coral reef systems-with a strong capacity to act as blue carbon sinks in certain situations. Features that promote blue carbon burial within these 'non-classical' blue carbon ecosystems included: (1) balancing of carbon release by calcification via carbon uptake at the individual and ecosystem levels; (2) high rates of allochthonous organic carbon supply because of high particle trapping capacity; (3) high rates of carbon preservation and low remineralization rates; and (4) location in depositional environments. Some of these features are context-dependent, meaning that these ecosystems were blue carbon sinks in some locations, but not others. Therefore, we provide a universal framework that can evaluate the likelihood of a given ecosystem to behave as a blue carbon sink for a given context. Overall, this paper seeks to encourage consideration of non-classical blue carbon ecosystems within NBS strategies, allowing more complete blue carbon accounting.

Combating climate change requires reducing greenhouse gas (GHG) emissions from human activities and enhancing carbon dioxide removal (CDR) through blue carbon ecosystems (BCEs). Progress is measured by international reporting of national GHG inventories under the UNFCCC, following IPCC guidelines. The EU Green Deal, particularly the EU Biodiversity Strategy to 2030, recognizes BCEs’ potential by advocating for the restoration of carbon-rich habitats. However, the IPCC Wetlands Supplement is underutilized in national GHG reporting, and few countries, especially in Europe, include blue carbon in their Nationally Determined Contributions (NDCs) under the Paris Agreement. This is due to limited awareness, the non-mandatory nature of the IPCC Wetlands Supplement, and data gaps. Our research aims to advance blue carbon knowledge, promoting BCEs as nature-based solutions, and addressing key gaps and scientific uncertainties to improve quantification and reporting of blue carbon under the UNFCCC in GHG inventory reporting under the Paris Agreement. The C-BLUES project, part of the Joint EU-China Flagship Initiative on Climate Change & Biodiversity, seeks to enhance the IPCC Wetlands Supplement, increase BCE inclusion in national GHG inventories, and explore additional BCEs like natural and farmed kelp systems. We document best practices for monitoring and verifying BCE actions, model BCE sequestration capacity, and upscale GHG budgets to estimate BCE contributions to EU and Chinese inventories. We assess carbon stock changes, GHG emissions, and removals from various management interventions, and evaluate the integration of BCEs into national reporting mechanisms. We present a roadmap and invite participation with the scientific community, policy makers and the wider civil society to generate knowledge, raise awareness of BCEs and build capacity for BC research, as well as provide guidance on voluntary reporting on BCE.

The concept of "blue carbon" is, in this study, critically evaluated with respect to its definitions, measuring approaches, and time scales. Blue carbon deposited in ocean sediments can only counteract anthropogenic greenhouse gas (GHG) emissions if stored on a long-term basis. The focus here is on the coastal blue carbon ecosystems (BCEs), mangrove forests, saltmarshes, and seagrass meadows due to their high primary production and large carbon stocks. Blue carbon sequestration in BCEs is typically estimated using either: 1. sediment carbon inventories combined with accretion rates or 2. carbon mass balance between input to and output from the sediment. The inventory approach is compromised by a lack of accurate accretion estimates over extended time periods. Hence, short-term sedimentation assays cannot be reliably extrapolated to long timescales. The use of long-term tracers like 210Pb, on the other hand, is invalid in most BCEs due to sediment mobility by bioturbation and other physical disturbances. While the mass balance approach provides reasonable short-term (months) estimates, it often fails when extrapolated over longer time periods (> 100 years) due to climatic variations. Furthermore, many published budgets based on mass balance do not include all relevant carbon sources and sinks. Simulations of long-term decomposition of mangrove, saltmarsh (Spartina sp.), and eelgrass (Zostera sp.) litter using a 3-G exponential model indicate that current estimates of carbon sequestration based on the inventory and mass balance approaches are 3-18 times too high. Most published estimates of carbon sequestration in BCEs must therefore be considered overestimates. The climate mitigation potential of blue carbon in BCEs is also challenged by excess emissions of the GHG methane (CH4) and nitrous oxide (N2O) from biogenic structures in mangrove forests and saltmarsh sediments. Thus, in many cases, carbon sequestration into BCE sediments cannot keep pace with the simultaneous GHG emissions in CO2 equivalents.

Photoautotrophic marine ecosystems can lock up organic carbon in their biomass and the associated organic sediments they trap over millennia and are thus regarded as blue carbon ecosystems. Because of the ability of marine ecosystems to lock up organic carbon for millennia, blue carbon is receiving much attention within the United Nations’ 2030 Agenda for Sustainable Development as a natural climate solutions and possible nature-based solution, but classically still focuses on seagrass meadows, mangrove forests, and tidal marshes. However, other coastal ecosystems could also be important for blue carbon storage, but remain largely neglected in carbon cycling budgets. Using a meta-analysis of 253 research publications, we identify other coastal ecosystems – including mud flats, fjords, coralline algal (rhodolith) beds, and some coral reef systems – with a strong capacity to act as blue carbon sinks in certain situations. Features that promote blue carbon burial within these ‘non-classical’ blue carbon ecosystems included: (1) balancing of carbon release by calcification via carbon uptake at the individual and ecosystem levels; (2) high rates of allochthonous organic carbon supply because of high particle trapping capacity; (3) high rates of carbon preservation and low remineralisation rates; and (4) location in depositional environments. Some of these features are context-dependent, meaning that these ecosystems were blue carbon sinks in some locations, but not others. We provide a universal framework that can evaluate the likelihood of a given ecosystem to behave as a blue carbon sink for a given context. We seek to encourage consideration of non-classical blue carbon ecosystems within management strategies, allowing more complete blue carbon accounting.

         Blue carbon ecosystems (mangroves, seagrass beds, and salt marshes) are one of the most effective carbon sinks on Earth and are critical to climate change mitigation and adaptation. Hainan Province in China accounts for 82% of the country's mangrove area and 64% of the country's seagrass bed area. Hainan's blue carbon plays an important role in local and national carbon sink enhancement efforts. From the perspective of economics, Hainan's blue carbon system plays a major supporting role in the local economy. Existing research on the protection of China's blue carbon ecosystems focuses on carbon sink accounting and economic valuation, and rarely involves microeconomic impact analysis of blue carbon protection actions. In particular, there are few studies specifically conducted on the impact on residents' livelihoods and well-being in Hainan.        In this context, we are attempting to conduct research in Hainan Province to answer the following questions: What impact does the protection and restoration of Hainan's blue carbon ecosystem have on the livelihoods of its coastal communities? We refined this question into three points: First, what are the livelihood sources and livelihood structures of Hainan's coastal and non-coastal communities; what changes have occurred around 2020? Second, has Hainan's special action on the protection and restoration of blue carbon ecosystems had an impact on the livelihoods of coastal communities? Third, through what channels does Hainan's special action on the protection and restoration of blue carbon ecosystems affect the livelihoods of coastal communities?        According to preliminary research, Hainan Province's special action for the protection and restoration of blue carbon ecosystems has a two-way impact on the livelihoods of coastal communities. On the one hand, blue carbon protection can maintain and promote the local fishery economy and tourism; on the other hand, due to restrictive regulations on the relevant use of marine resources at the policy level, the protection and restoration of mangroves may have a negative impact on fisheries. Maintaining a balance between fishermen's livelihoods and blue carbon protection may be one of the difficulties in blue carbon conservation. Treating the special action for the protection and restoration of blue carbon ecosystems as a quasi-natural experiment, we are going to conduct policy evaluation in our study. We will conduct a community questionnaire survey and introduce the propensity matching difference-in-difference (PSM-DID) model to reveal the net effect of Hainan's blue carbon ecosystem protection on the livelihoods of coastal communities.

This paper offers a comprehensive synthesis of 9 research papers from the Asia-Pacific Network for Global Change Research (APN) project titled "Enhancing Capacities of Local Stakeholders in Coral Triangle in Managing Blue Carbon Ecosystems for Climate Mitigation and Adaptation." These papers are organised into four key thematic areas: (1) assessing the status of mangrove degradation and its underlying factors, (2) exploring community perceptions of seagrass ecosystems and their associated services, (3) analysing local perspectives on sustainable tourism and its influence on blue carbon (BC) ecosystem services, and (4) discerning trends in research and coastal management strategies for BC ecosystems. The findings presented within these papers illuminate the intricate challenges surrounding BC ecosystems in the Philippines and Indonesia, underscoring a range of human-induced pressures and natural vulnerabilities. These studies emphasise the significance of incorporating community perceptions and socio-economic dynamics into the BC ecosystems' conservation and management strategies framework. The comparative insights derived from these papers hold vital implications for local stakeholders and policymakers. Practical training in Geographic Information Systems (GIS) can empower local communities to enhance their capacity-building efforts in the future. This is valuable guidance for shaping future BC ecosystem management plans and programs, particularly in a rapidly changing climate.

Evolution of blue carbon management policies in China: review, performance and prospects

Blue carbon ecosystems require conservation and restoration to maximize organic carbon (CORG) sequestration to ameliorate greenhouse gas emissions. Salt marshes, mangrove forests and seagrass meadows are all autotrophic and are considered blue carbon ecosystems. Macroalgae and tidal flats are currently not considered blue carbon habitats. Blue carbon ecosystems contribute globally to climate change mitigation and at local and national scales, especially in the provision of other ecosystem goods and services. Financial investment is constrained by large uncertainties in CORG dynamics and best practices in restoration, rehabilitation and conservation. Several key emerging perspectives include (1) the fact that groundwater discharge of dissolved carbon is a major pathway of blue carbon loss; (2) allochthonous CORG inputs are required to achieve ecosystem carbon mass balance; (3) blue carbon dynamics are enhanced by habitat connectivity and biotic activities; (4) CH4 and N2O emissions reduce blue carbon potential; (5) habitat destruction causes blue carbon stock losses, but variable gas emissions; (6) sediment blue carbon stocks are increasing at the poles; and (7) land-use and land-cover changes (LULCC) drive changes in blue carbon stocks and emissions. Further research is needed to clarify the applicability of these emerging perspectives.

Prioritising plastic pollution research in blue carbon ecosystems: A scientometric overview

Blue carbon ecosystems (BCEs), including mangrove forests, seagrass meadows and tidal marshes, store carbon and provide co-benefits such as coastal protection and fisheries enhancement. Blue carbon sequestration has therefore been suggested as a natural climate solution. In this Review, we examine the potential for BCEs to act as carbon sinks and the opportunities to protect or restore ecosystems for this function. Globally, BCEs are calculated to store >30,000 Tg C across ~185 million ha, with their conservation potentially avoiding emissions of 304 (141–466) Tg carbon dioxide equivalent (CO2e) per year. Potential BCE restoration has been estimated in the range of 0.2–3.2 million ha for tidal marshes, 8.3–25.4 million ha for seagrasses and 9–13 million ha for mangroves, which could draw down an additional 841 (621–1,064) Tg CO2e per year by 2030, collectively amounting to ~3% of global emissions (based on 2019 and 2020 global annual fossil fuel emissions). Mangrove protection and/or restoration could provide the greatest carbon-related benefits, but better understanding of other BCEs is needed. BCE destruction is unlikely to stop fully, and not all losses can be restored. However, engineering and planning for coastal protection offer opportunities for protection and restoration, especially through valuing co-benefits. BCE prioritization is potentially a cost-effective and scalable natural climate solution, but there are still barriers to overcome before blue carbon project adoption will become widespread.

Remote sensing for cost-effective blue carbon accounting