Ocean-Based Natural Climate Solutions: Seaweed


SOA Blog

Sustainable Ocean Alliance is accelerating ocean solutions around the world. Here are their stories.

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.


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.

Blue Carbon Blog Series Blog Headers (2)

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.



The Climate Potential of Seaweed

To further enhance carbon sequestration by seaweed, three interventions have been proposed by EDF: conserving and restoring existing seaweed stands, increasing the productivity of existing seaweed farms, and expanding seaweed farming.

Conserving and Restoring Existing Seaweed Stands

In some areas around the world, natural populations of seaweed have decreased significantly, primarily due to various factors such as climate change, overfishing, and excessive sedimentation. The decline of global kelp forests, in particular, has been occurring at rates two to four times faster than coral reefs and tropical forests (Feehan et al., 2021).

Conserving seaweed populations involves addressing factors like climate change, predator depletion, sediment accumulation, and diseases that hinder restoration and contribute to their decline. Through strategic research and targeted actions, such as harvesting grazing species, fishing regulations, and pollution management, we can keep existing seaweed stands thriving.

Moreover, it is essential to understand the carbon sequestration potential of seaweed. Accurately measuring their carbon absorption capacity requires a deeper understanding of the factors influencing carbon flow in these ecosystems. The species of seaweed, the density of the seaweed bed, the intensity of harvesting, nutrient availability, grazing levels, and seasonal variations all influence the rate at which seaweed can sequester carbon. Furthermore, environmental conditions such as strong currents, wave energy, and ocean floor topography also impact the capabilities of seaweed. 

Increasing Productivity of Existing Seaweed Farms

In addition to conserving existing seaweed populations, we can also boost the productivity of existing seaweed farms to expand the carbon sequestration potential of seaweed. By identifying and addressing factors that constrain productivity, such as disease, pollution, and financing, it is possible to optimize farming practices. This can be achieved through strategic measures like adjusting spacing, selecting appropriate species, timing seeding and harvesting, and improving operational aspects.

Expanding Seaweed Farming

Seaweed farming in offshore areas shows considerable potential for enhancing carbon sequestration, making it a promising solution for climate stabilization. Furthermore, seaweed farming can increase habitat and biodiversity provisioning as floating debris and seaweed attract more marine life.

Ongoing advancements in infrastructure, operations, and monitoring have made offshore seaweed farming more feasible. However, challenges such as rough seas, limited resources, proximity to supportive infrastructure, and the need to mitigate negative impacts must be addressed. The establishment of governance systems and research on social and ecological risks will also contribute to the success of offshore seaweed farming.



SOA Grantee Spotlights: Seaweed-Based Solutions

Salty Gold Uni: Purple Urchin Food Products | California, United States of America

Max Diamond founded a startup that harvests purple sea urchin—a species that aggressively consumes giant kelp ecosystems in the nutrient-rich waters off of California—to create sustainable food products that will indirectly improve the degradation of kelp ecosystems.

With SOA's support, Max has taken the first steps (permitting, licensing, packaging/branding) to bring his product to market and work with mentors to help quantify the environmental impact that will drive the sustainability narrative of his product. 

Kelp Forest Foundation: Researching the Ecosystem Impacts of Giant Kelp | Namibia

As a researcher with the Kelp Forest Foundation, Master's student Protasius Mutijda aims to measure the biogeochemical impact of cultivated giant kelp off the coast of Namibia. These magnificent kelp forests thrive in the nutrient-rich Benguela Current, home to some of the world's most fertile waters. The valuable data Protasius collects will contribute to developing a comprehensive kelp Carbon Dioxide Removal model, thereby enhancing global understanding of these vital ecosystems.



Coastal Carbon: Quantifying Seaweed Biomass for Sequestration | Canada

Kelly Zheng, MBA/PhD candidate in AI and co-founder of Coastal Carbon, has spent the last three years developing AI models for Coastal Carbon. Presently, the focus lies on the ongoing task of segmenting and classifying seaweed using remote sensing data. The ultimate goal is to develop AI that can accurately measure underwater seaweed biomass. This groundbreaking innovation will vastly improve the current time-consuming, expensive, and labor-intensive methods of manually sampling seaweed while mitigating potential risks. By automating these measurements, it will revolutionize our understanding and quantification of seaweed-based ocean restoration.



Key Points and Takeaways

Seaweed stands and farms offer a wide range of benefits, including food production, alternative economic opportunities, biodiversity support, and contributions to reducing ocean acidification and carbon sequestration. To fully harness the potential benefits of seaweed, a combination of farms producing different types of products and staggering harvest cycles would be necessary.

To comprehend the impact of seaweed carbon sequestration, it is imperative to identify which carbon fluxes related to seaweed have been measured, determine the most effective method for measuring carbon sequestration rates, compare the effectiveness of seaweed stands to other ocean-based methods, and explore the possibility of using restoration of these stands as a long-term strategy for carbon sequestration. There remain significant data gaps that need to be filled in order to quantify carbon sequestration accurately and create high-quality carbon credits. 




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, a set of principles and guidance was developed to define high-quality blue carbon projects and credit development. 




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