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Forests and renewable energy are often the focus of the headlines in the race to decarbonize the global economy; however, another powerful climate solution that is rapidly gaining traction is blue carbon. Blue carbon does not involve planting or replanting trees like typical carbon offsets but rather derives from the ocean’s coastal ecosystems, specifically mangroves, seagrass and tidal marsh areas. Coastal ecosystems have high levels of biodiversity and provide protection from storms, but they also function as highly efficient natural sinks for carbon dioxide thus introducing a new class of climate-based assets with an increasing amount of financial value.¹

What Is Blue Carbon? The Science of Mangroves, Seagrass, and Salt Marshes

Blue carbon encompasses sequestration of CO2 in coastal marine ecosystems including Mangrove forests, Salt Marshes and Seagrass beds through plant uptake (photosynthesis), soil incorporation and sedimentation.

These ecosystems are submerged in water but are equivalent to terrestrial forests because they sequester carbon via photosynthesis and storage in soil, where anaerobic or low oxygen conditions inhibit decay and contribute to long-term retention of carbon in soils below ground (50%-99%). ²

In many cases, carbon may be stored in soil several meters down where it may be sequestered for long periods of time; hundreds to thousands of years.

According to several studies, coastal wetlands sequester carbon at much faster rates (10 to 50 times) than any land-based forest and, consequently, have the potential to maintain vast amounts of carbon stock due to the accumulation of sediment that occurs over time. Coastal wetlands are also known to provide additional benefits such as helping stabilize shorelines against storms, providing habitat for commercially important fish species, and protecting biodiversity. As a result of the numerous ecosystem services associated with these unique ecosystems, coastal wetlands present an opportunity for both energy and financial support by investors and policy makers alike.³

Quantifying Carbon Sequestration in Marine Systems

In relation to global warming, the amount of carbon stored by all blue carbon ecosystems combined is significant enough to warrant their inclusion when considering efforts to combat climate change. This is particularly true for:

Global mangrove ecosystems store a large amount of carbon in both above-ground plant biomass and below-ground sediments. Many mangroves ecosystem carbon

stocks are estimated to be three to four times higher than those of tropical forests (per cubic meter).

Despite only representing approximately 0.1% of the ocean floor, seagrass meadows contribute 10%–18% of the total carbon being buried within the ocean and are capable of sequestering (i.e., absorbing) tens of millions of tons of CO₂ through the process of photosynthesis each year.

Salt marshes, found worldwide on temperate coastlines, offer the ability to store large amounts of carbon through the accumulation of sediments derived from plant detritus and decomposition of organic matter. Salt marshes have an incredible ability to import carbon and store it for extremely long periods of time.

To accurately account for carbon in coastal salt marshes and seagrasses, scientists and researchers utilize various types of information, including field sampling, sediment cores, remote sensing, modelling and other methods, to develop reliable estimates for carbon accounting.

Blue Carbon vs. Green Carbon: Efficiency and Permanence

When comparing blue and green (terrestrial) carbon solutions, there are two main points of interest with respect to both: Efficiency & Permanence.

Efficiency: Coastal ecosystems can store carbon much more quickly than terrestrial forests due to carbon being rapidly sequestered through the generation of new biomass and the buildup of new sediments. Coastal ecosystems have an increased capacity to capture and bury carbon – up to 50X faster than some terrestrial ecosystems (on a per area basis).

Permanence: Coastal ecosystems’ ability to store Carbon is much longer-lasting, with buried carbon remaining stable in low-oxygen soils for hundreds of years. Forests may be subjected to wildfires, Climate Change-induced heat stress, and Drought; however, blue carbon storage is protected from many of these threats due to their being located underwater. The underlying factor to their longevity is the requirement that coastal ecosystems are protected from degradation and conversion. If an area of mangroves or salt marshes is removed, their once-stored carbon would be re-released back to the atmosphere.

How Blue Carbon Credits Are Verified and Traded

To enable the trading of blue carbon as a climate asset, continual and methodical measurement reporting and Verification (MRV) must be established in order for Carbon Credit Standards such as the Verra Verified Carbon Standards (VCS) and the Gold Standard to recognize Blue Carbon. ⁴

A methodology (VM0033) dedicated to the measurement of GHG removals from tidal wetlands and seagrass restoration efforts is included in the Verra VCS alternative (VM0033).
Gold Standard has developed methodologies specifically for sustainable mangrove management projects, which focus on the environmental and social co-benefits as well as the removal of Carbon Dioxide (co2).

Independent third-party assessment of each project’s baseline and ongoing monitoring data, as well as carbon accounting, will allow the verification of net GHG emission reduction; thus, allowing for the Carbon Credits to be traded in voluntary and (in limited cases) compliance markets.⁵

Case Studies: Australia and Kenya

Australia’s Blue Carbon Methodology

Australia has established a leadership position in the development and implementation of national blue carbon crediting systems, via the establishment of one of the first national methods on blue carbon. Australia developed its methodology as part of its Emissions Reduction Fund (ERF), for projects that restore/rehabilitate coastal wetland ecosystems through initiatives such as restoring tidal flows to wetlands, accumulate carbon and avoid carbon emissions through the accrual of Australian Carbon Credit Units (ACCUs).⁶

As one of the leading nations in blue carbon, Australia has approximately 12% of the world’s coastal carbon ecosystems and contains diverse and extensive seagrass meadows on/near the Great Barrier Reef, which in and of themselves contain a significant quantity of global blue carbon stocks.⁷

Kenya’s Mikoko Pamoja Project

On the opposite side of the world, Mikoko Pamoja in Kenya, which translates to “Mangroves Together”, is one of the greatest blue carbon projects available today. Mikoko Pamoja began in 2012 in Gazi Bay and is a community-based project that works to protect and restore mangrove forests while selling carbon credits on the voluntary carbon market. The revenue generated is then used to fund clean drinking water, education and other local development projects.⁸

Mikoko Pamoja sold thousands of carbon credits each year based on its reforested mangroves (a tonne of CO₂ sequestered by mangroves equals 1 carbon credit), while using certified standards such as Plan Vivo to ensure all carbon credits are authenticated. Mikoko Pamoja exemplifies how carbon financing can bring about positive climate and community benefits.⁹

Blue Carbon as a New Asset Class

Blue carbon projects represent less than 1% of all voluntary carbon credits so far, yet their advantages, availability for implementation, are getting more attention than ever from investment firms, governments and corporations. They are seen as viable alternatives to traditional land-based carbon offset projects due to the environmental benefits, climate change mitigation characteristics, longevity, and economic potential associated with blue carbon projects.¹⁰

While the potential is great; there are still challenges associated with the expansion of the use of blue carbon projects. To scale up blue carbon projects and have transparent and verifiable measurement, reporting and verification processes and a stable carbon market is necessary. Also, the policies supporting the use of blue carbon projects must be developed and made available for use.

As climate change adaptation efforts grow, blue carbon may be poised to take center stage as the next emerging market for the climate market and the place where hidden value is found with the oceans representing an untapped resource for climate change mitigation and resilience.