Mapping blue carbon ecosystems from Earth observations at a national scale for Papua New Guinea

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.

Blue carbon (BC) ecosystems are an important coastal resource, as they provide a range of goods and services to the environment. They play a vital role in the global carbon cycle by reducing greenhouse gas emissions and mitigating the impacts of climate change. However, there has been a large reduction in the global BC ecosystems due to their conversion to agriculture and aquaculture, overexploitation, and removal for human settlements. Effectively monitoring BC ecosystems at large scales remains a challenge owing to practical difficulties in monitoring and the time-consuming field measurement approaches used. As a result, sensible policies and actions for the sustainability and conservation of BC ecosystems can be hard to implement. In this context, remote sensing provides a useful tool for mapping and monitoring BC ecosystems faster and at larger scales. Numerous studies have been carried out on various sensors based on optical imagery, synthetic aperture radar (SAR), light detection and ranging (LiDAR), aerial photographs (APs), and multispectral data. Remote sensing-based approaches have been proven effective for mapping and monitoring BC ecosystems by a large number of studies. However, to the best of our knowledge, this is the first comprehensive review on the applications of remote sensing techniques for mapping and monitoring BC ecosystems. The main goal of this review is to provide an overview and summary of the key studies undertaken from 2010 onwards on remote sensing applications for mapping and monitoring BC ecosystems. Our review showed that optical imagery, such as multispectral and hyper-spectral data, is the most common for mapping BC ecosystems, while the Landsat time-series are the most widely-used data for monitoring their changes on larger scales. We investigate the limitations of current studies and suggest several key aspects for future applications of remote sensing combined with state-of-the-art machine learning techniques for mapping coastal vegetation and monitoring their extents and changes.

Operationalizing marketable blue carbon

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.

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

Using standards for coastal nature-based solutions in climate commitments: Applying the IUCN Global Standard to the case of Pacific Small Island Developing States

The international consensus on the urgent necessity to act to protect a vulnerable environment and endangered biodiversity raises key challenges, including the need to improve and accelerate estimating carbon stocks and changes in coastal ecosystems on a global scale. Remote sensing methods, combined with ground truthing and modelling, are essential for addressing this challenge cost-effectively.The ESA Coastal Blue Carbon project is an unprecedented effort to review, assess, and attempt to provide key elements for the sustainable management of Blue Carbon Ecosystems (BCEs) through diverse case studies. Over two years, a multidisciplinary consortium is investigating the mangrove, seagrass, and tidal salt marsh BCEs in France, Canada, Spain and French Guiana. The project aims to develop innovative tools and methods based on Earth Observation (EO) to estimate and monitor changes in carbon stocks, and brings together a community of end-users, to ensure the tools meet the operational needs, including:Conservation stakeholders aiming to enhance the impact of their actions. Decision-makers looking to integrate blue carbon into national carbon accounting and set ambitious mitigation targets. The financial sector seeking reliable blue carbon investment opportunities. Our rationale is to capitalise on existing data and multi-scale resolution imagery to assess the potential for global replicability of the space-based methodologies from highly representative pilot regions of the main BCEs across three different continents. The project consists of two phases: the first focuses on developing and consolidating requirements to create new methods on test areas, while the second emphasizes upscaling demonstration, and impact assessment. We aim at producing maps of carbon storage estimates for three different years from 2015 to 2025, with a spatial resolution no coarser than 10m while ensuring active participation from Early Adopters.The project has been submitted to be endorsed under the Global Ocean – Blue Carbon Programme of UNESCO Ocean Decade.

Blue Carbon Ecosystems (BCEs) help mitigate and adapt to climate change but their integration into policy, such as Nationally Determined Contributions (NDCs), remains underdeveloped. Most BCE conservation requires community engagement, hence community-scale projects must be nested within the implementation of NDCs without compromising livelihoods or social justice. Thirty-three experts, drawn from academia, project development and policy, each developed ten key questions for consideration on how to achieve this. These questions were distilled into ten themes, ranked in order of importance, giving three broad categories of people, policy & finance, and science & technology. Critical considerations for success include the need for genuine participation by communities, inclusive project governance, integration of local work into national policies and practices, sustaining livelihoods and income (for example through the voluntary carbon market and/or national Payment for Ecosystem Services and other types of financial compensation schemes) and simplification of carbon accounting and verification methodologies to lower barriers to entry.

Plastics are rapidly accumulating in blue carbon ecosystems, i.e., mangrove forests, tidal marshes, and seagrass meadows. Accumulated plastic is diverted from the ocean, but the extent and nature of impacts on blue carbon ecosystem processes, including carbon sequestration, are poorly known. Here, we explore the potential positive and negative consequences of plastic accumulation in blue carbon ecosystems. We highlight the effects of plastic accumulation on organic carbon stocks and sediment biogeochemistry through microbial metabolism. The notion of beneficial plastic accumulation in blue carbon ecosystems is controversial, yet considering the alternative impacts of plastics on oceanic and aboveground environments, this may be the "lesser of evils". Using environmental life cycle impact assessment, we propose a research framework to address the potential positive and negative impacts of plastic accumulation in blue carbon ecosystems. Considering the multifaceted benefits, we prioritize expanding and managing blue carbon ecosystems, which may help with ecosystem conservation, as well as mitigating the negative effects of plastic.

         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.

“Whose carbon is it?” Understanding municipalities role in blue carbon ecosystems management in Canada

Blue Carbon Ecosystems (BCEs) play a crucial role in carbon sequestration and climate change mitigation. However, their carbon cycle dynamics, particularly under changing environmental conditions, remain insufficiently understood. This study investigates the Qigu lagoon ecosystem, a representative BCE along Taiwan's southwestern coast. Adjacent to mangrove forests, the lagoon harbors rich biodiversity and holds substantial carbon storage potential but faces increasing threats from global climate change and intensified human activities. To address these challenges, we conducted integrated field sampling and laboratory analyses to examine the biogeochemical processes governing carbon cycling in the Qigu lagoon. Sediment cores were collected from multiple locations across the lagoon and analyzed for dissolved methane concentrations, total alkalinity, dissolved ions, and nutrient levels. These measurements aim to quantify sedimentary carbon burial rates, assess greenhouse gas emissions, and evaluate nutrient cycling within the ecosystem. Preliminary results indicate that, while the lagoon effectively sequesters organic matter in its sediments, it simultaneously emits significant amounts of methane (CH₄), a potent greenhouse gas. This discovery raises important questions about whether methane emissions from wetlands—traditionally regarded as natural carbon sinks—may substantially offset the carbon burial and absorption capacity of marine blue carbon systems. Understanding the balance between carbon sequestration and greenhouse gas emissions is critical for accurately evaluating the climate mitigation potential of BCEs. Findings from this study will provide valuable insights for the conservation and sustainable management of coastal ecosystems, contributing to global efforts in combating climate change.

The management of coastal blue carbon ecosystems can contribute to mitigate anthropogenic greenhouse gas emissions. However, limited information on soil organic carbon (OC) decay rates in tidal marsh, mangrove, and seagrass soils hinders their inclusion in climate strategies and carbon-crediting schemes. Here, we analyzed downcore OC trends in 3761 soil cores from blue carbon ecosystems worldwide. A decrease in OC content with soil depth was measured in 63% of the cores, whereas stable and increasing trends were observed in 22% and 15% of the cores, respectively. Based on 85 profiles where OC decay could be modelled, the OC decay rate in blue carbon ecosystems was 0.023 ± 0.002 yr−1 over the last 100 years and 0.007 ± 0.0007 yr−1 over the last 1000 years. This results in the stabilization of 9% and 0.1% of the soil OC inputs 100 and 1000 yr after burial, respectively, showcasing the long residence time of OC in the sinks associated to blue carbon ecosystems. This study provides baseline estimates of soil OC decay under natural conditions for short- and long-term periods, and to assess the carbon abatement and additionally provided by carbon offsetting projects in blue carbon ecosystems.

Remote sensing for cost-effective blue carbon accounting

Blue carbon ecosystems play a strategic role in mitigating climate change through their ability to absorb and store carbon significantly. However, uncontrolled exploitation of marine resources, such as overfishing, destructive fishing methods, and fishing gear waste, have threatened the sustainability of blue carbon ecosystem. Penangkapan Ikan Terukur (PIT) policies implemented by the Indonesian government aims to realize sustainable fisheries by regulating fishing quotas based on zoning. This reserach aims to identify the urgency of integrating blue carbon ecosystems into PIT policies in Indonesia to maintain the sustainability of marine resources and support climate change mitigation. Using qualitative descriptive methods based on literature studies, this research found that integrating blue carbon ecosystems into PIT policies can provide significant ecological benefits. Strict monitoring, restoration of blue carbon ecosystem habitats, and implementation of scientific data-based policies are needed to ensure the success of this policy. This integration is expected to be able to maintain marine ecosystems, support sustainable fisheries, and contribute to global climate change mitigation targets.