Ocean-Based Natural Climate Solutions: Coastal Ecosystems

The ocean, covering 71% of the Earth's surface, is a remarkable planetary system that stores more carbon than all soil and forest systems combined. Its vastness, remote nature, and intricate biogeochemical and physical characteristics make it both captivating and challenging to study. 

In our active fight against climate change, natural climate solutions (NCS) have emerged as valuable strategies to offset, mitigate, and reverse the impacts of our changing planet. These solutions restore and conserve various ecosystems to sequester carbon and provide additional benefits, including supporting livelihoods in fishing and tourism, protecting coastal regions, preserving biodiversity, and offering recreational opportunities. Natural climate solutions present a holistic approach with multiple advantages.

RELATED | WHAT IS BLUE CARBON

In this 3-part blog series, we're diving into the fascinating world of natural climate solutions by exploring the findings of three reports by SOA partners, the Environmental Defense Fund (EDF), that shine a light on different interventions for carbon sequestration in various ecosystems. We will also highlight real-life examples of individuals and organizations supported by SOA grants that drive positive change through natural climate solutions.

Read Part 1: Ocean-Based Natural Climate Solutions: Seaweed and Part 2: Ocean-Based Natural Climate Solutions: Open Ocean of this blog series

Types of Ocean-Based Natural Climate Solutions 

Within the ocean system specifically, the following reports from EDF examine three points of potential intervention for natural climate solutions: 

• EDF Report on Seaweed: Various interventions to conserve, restore, and increase the productivity of macroalgal (seaweed) systems (natural beds and farms) to avoid greenhouse gas emissions and sequester more carbon.

• EDF Report on Open Ocean: Interventions in the open ocean, including carbon sequestration via the rebuilding of biomass in large marine mammals and epipelagic fishes, and the potential for avoided emissions by restricting or limiting new fishing in the mesopelagic ocean and/or benthic trawling

• EDF Report on Coastal Ecosystems: Interventions to conserve, restore, and manage vegetated, coastal blue carbon ecosystems such as mangroves, marshes, and seagrasses to avoid greenhouse gas emissions and increase carbon sequestration.

It is crucial to note that no approach for removing existing carbon from the Earth's atmosphere can replace the importance of avoiding or reducing emissions. Even if removal is achieved through natural climate solutions or any other method, emission reduction remains paramount.

Part 3 of the series focuses on Natural Climate Solutions in Coastal Mangrove, Marsh, Seagrass, and Coral Ecosystems

Coastal Blue Carbon Ecosystems: Coastal Mangroves, Marshes, Seagrasses, and Corals

Coastal blue carbon systems, which are disappearing ten times faster than tropical forests (Duarte et al., 2013), are not only losing their ability to store carbon but also missing out on the benefits they provide as important ecosystem providers. Mangrove, tidal marsh, and seagrass ecosystems store carbon in both living biomass and in underlying substrates.

Among the coastal NCS pathways discussed in this section, the preservation of existing mangrove ecosystems is regarded as the most feasible option given the extensive scientific knowledge about their functioning and coverage. Restoration of mangroves is the next most viable pathway, followed by preserving and restoring tidal marshes. Restoring and preserving seagrass ecosystems are currently among the least efficient pathways due to uncertainties around their overall status with emissions storage and evidence of unsuccessful attempts for seagrass restoration.

Mangroves

Mangroves, recognized as the most thoroughly studied marine ecosystem, offer exciting opportunities for preservation and restoration initiatives, making them an ideal source of high-quality carbon credits. Despite this, there are lingering uncertainties and areas that require further research and development to deepen our understanding and maximize the potential of mangroves as a carbon sink. 

Scientists have made significant progress in estimating the global extent and carbon storage in the above-ground biomass of mangroves. However, it's important to note that the majority of carbon stored by mangrove ecosystems is actually found in the underlying soils. This means that estimates of total mangrove carbon storage heavily rely on how deep one considers below the land surface.

SOA Grantee Spotlights: Mangroves

Carbon Ethics: Empowerment for Sustained Restoration | Indonesia

Indonesia is among the top global areas for blue carbon sequestration through mangrove forests. Carbon Ethics, supported by multiple SOA grants, aims to expand and improve their blue carbon initiatives in Dompak and Pangkil Islands. With the latest grant, Carbon Ethics will identify a new restoration site, establish a mangrove nursery, enhance waste reduction infrastructure, and continue their efforts to plant 2,000 mangroves per month. 

Ambakofi: Holistic Mangrove Restoration | Tanzania

Ambakofi is providing sustainable mangrove restoration and maintenance training to 75 fishers from three coastal villages, using the Community Based Ecological Mangrove Restoration (CBEMR) course from the Mangrove Action Project. The CBEMR technique helps address the root causes of mangrove degradation, allowing mangroves to regrow naturally without further intervention. This method is far more effective than traditional planting projects. After training, the fishers will restore and monitor 7.5 hectares of mangroves, clearing waterways of debris for enhanced growth.

LINAT (Light for Nature): Community-Led Restoration of Carbon Sink  | Cameroon

LINAT is a newly established organization led by SOA Young Ocean Leader, Anthony Duxell Malle. SOA's support has enabled them to plant over 1,100 mangroves, restore 5 hectares of land, and establish two new mangrove nurseries. Moving forward into 2023, LINAT aims to lay the foundation for a mangrove eco-park and obtain third-party certification for their mangrove restoration efforts.

Tidal Marshes

Tidal marshes have a global range that is poorly mapped compared to that of mangroves. The estimates of reducing emissions through the conservation and preservation of existing marshes, as well as the potential to sequester carbon through restoration, are highly variable. Recent research emphasizes the importance of incorporating multiple stressors and biological changes into management and restoration strategies rather than focusing solely on acute disturbances. 

It's worth noting that the sequestration potential of tidal marshes is vulnerable to factors such as rising sea levels and carbon cycle feedback, which possess the potential for both positive and negative impacts on carbon sequestration.

SOA Grantee Spotlights: Tidal Marshes

Carolina Ocean Alliance: Halsey Creek Saltmarsh Restoration | South Carolina, U.S.

Halsey Creek is one of the last remaining tidal salt marshes on the Charleston Peninsula and serves as a critical source of food, habitat, and protection for a variety of migratory and local birds.

In an effort to restore this critical coastal ecosystem, The Carolina Ocean Alliance, an SOA Hub based in Charleston, partnered with the M.A.R.S.H. Project (formerly the Marshkeepers)—a dedicated coalition of hydrologists, historians, artists, journalists, and students. Together, they implemented a plan to reintroduce native plant species to Halsey Creek, serving as a model for community-led management and restoration efforts across the wider community and region.

Seagrasses

Seagrasses have received relatively limited attention in terms of research, resulting in a lack of comprehensive knowledge regarding their spatial extent and their role in carbon storage. While their ecological significance is generally acknowledged, the capacity of seagrasses to sequester carbon remains uncertain. One of the main reasons behind this uncertainty is the limited effectiveness of passive remote sensing techniques in accurately assessing underwater habitats, leading to estimations of seagrass extent.                

Areas for further research and development in seagrass studies include understanding the global extent of seagrasses and predicting their future distribution, investigating the sources and fate of carbonates in seagrass meadow sediments and their impact on carbon dioxide production, conducting more measurements of air-sea gas exchange above seagrass beds to enhance predictive models, and continuously investigating factors contributing to restoration project failures in seagrass systems.     

SOA Grantee Spotlights: Seagrasses

SOA Tanzania: Grass Underwater | Tanzania 

Ailars David founded SOA Hub Tanzania—now a registered community-based organization in Dar es Salaam, Tanzania—to preserve seagrass beds through community education and restoration. By establishing nurseries and out-planting seagrass in degraded habitats, they also are able to support alternative livelihoods for local fishers. Some of the frequent challenges Ailars and his team face include the difficulty of transplanting seagrass and quantifying its carbon sequestration potential given the high number of variables and the high cost of sophisticated monitoring techniques.

Edinburgh Napier University: Innovating Techniques for Community-Based Seagrass Mapping | Kenya

Edward Mutwiri Mwikamba, a plant ecologist and Ph.D. student at Edinburgh Napier University, focuses on studying the factors that are driving changes in seagrass coverage and health in Kenya.

With support from SOA, Mwikamba's project aims to develop cost-effective methods for measuring and reporting seagrass health. The project will compare two approaches: analyzing video and images using artificial intelligence and manual monitoring through point count and transect methods. The ultimate goal is to identify the most effective methodology to enable community-based conservation efforts funded by bundling recorded (but not accredited) carbon benefits with mangrove carbon credits.

Coral Reefs

While coral reefs themselves are not significant long-term carbon sinks, they likely play an indirect supportive role for other blue carbon systems that do actively sequester carbon. 

Existing studies on the benefits of coral reefs have not specifically addressed their role in contributing to carbon sequestration in nearby blue carbon ecosystems. This research gap underscores the need to adopt a different perspective toward blue carbon ecosystems to recognize their interconnectedness.

Komunitas Sinara Kaimana: Community-led Restoration of Kaimana Coral | Indonesia

Kaimana, an area in Indonesia, has been designated as a regional Marine Protected Area (MPA) in order to preserve its diverse ecosystem and maximize its fishery potential. With support from SOA, this project aims to accelerate the recovery of degraded coral reefs and enhance the populations of keystone marine species. This will be accomplished by installing 60 coral spider structures and establishing five new coral nurseries. In addition, residents of three local communities will receive training in coral conservation. The project leaders will also work towards implementing village regulations to enforce the protection of the marine ecosystem in Kaimana.

Koraï: Reef Restoration | Madagascar

Born and raised in Madagascar, Jeimila Donty established Koraï Africa in 2022 with a mission to restore coastal ecosystems in Africa. The project aims to grow 2,000 corals and hire a biologist to conduct a feasibility study. The study will explore the potential for establishing an active restoration site and a Marine Protected Area along the northern coast of Madagascar.

Aqua-Farms Organization: Restoration of Buyuni Reef | Tanzania

Buyuni Reef, an important breeding and nursery site for vulnerable fish species, has suffered extensive damage over the past two decades due to climate change and destructive fishing practices. This has resulted in the loss of diverse coral species and a decline in the economic and ecological significance of the reef. To address this, the local community designated 4,000 sq. meters as a locally managed Marine Protected Area in early 2022. Aqua-Farms plans to adopt a community-based approach to restore Buyuni Reef by replanting 1,000 coral fragments across 400 square meters, with the larger goal of restoring 1 square kilometer by 2030.

Key Points and Takeaways

In all of the coastal ecosystems mentioned, there are overarching uncertainties regarding the carbon storage, carbon fluxes, and overall sequestration potential of these habitats. Additionally, there has been limited attention given to non-CO2 greenhouse gas fluxes like methane and nitrous oxide, which raises concerns about the stability of carbon storage within these ecosystems.

To effectively conserve these valuable coastal blue carbon ecosystems and advance the cause of natural climate solutions, it is imperative to invest in further research, mapping and exploration efforts, and a deeper understanding of these complex systems.

Conclusion

Many of these marine ecosystems store carbon at rates far exceeding those of other global ecosystems. Additionally, there are many co-benefits associated with the preservation or restoration of these blue carbon ecosystems. 

Addressing the limitations requires the development of new frameworks that conceive individual blue carbon ecosystems as interconnected elements within broader seascapes, rather than as self-contained entities. Such a shift in perspective would enable a more holistic approach to harnessing the potential of these ecosystems.

High-quality blue carbon projects should accurately sequester and store carbon, restore ecological integrity, and provide opportunities for local and Indigenous communities to participate fairly and benefit from the voluntary carbon market. Through an open and consultative research process, this set of principles and guidance has been developed by leading environmental groups to define high-quality blue carbon projects and credit development.