by: David Chen and Daniel Frasca | September 29, 2022

Blue carbon includes important coastal and marine ecosystems such as mangroves, seagrass meadows, and tidal marshes.

What is Blue Carbon?

On the fringes of Earth’s continents lies one of nature’s greatest climate regulation mechanisms: vast reserves of organic carbon known as blue carbon. “Blue carbon” refers to the organic carbon captured and stored in coastal and marine ecosystems and can be used to refer to the marine habitats that sequester and store carbon dioxide.

The United Nations first used the term “blue carbon” in a 2009 report that recognized the critical role some coastal and marine ecosystems play in drawing down carbon from the atmosphere. The United Nations Framework Committee on Climate Change defines blue carbon as mangroves, seagrass meadows, and tidal marshes. As the field of blue carbon grows, additional ecosystems will likely be recognized as blue carbon, a topic we will discuss in an upcoming blog.

As of late, blue carbon has become a hot topic due to the immense capacity of these ecosystems to draw down atmospheric carbon levels and provide irreplaceable ecosystem services.

The intricate root systems of mangroves on the Indonesian island of Nias provide protection from storm surge and coastal erosion for local communities.

Blue Carbon as a Climate Solution

What makes coastal and marine ecosystems different than their terrestrial equivalents? After all, aren’t all plants capable of sequestering carbon? While that may be true, blue carbon ecosystems can capture 10-50 times more carbon per unit than their land-dwelling counterparts. In fact, every year, blue carbon ecosystems bury underground a comparable amount of carbon as terrestrial forests despite occupying less than 3% of the global forest area. The open ocean is also no match for the carbon-capturing powers of coastal blue carbon ecosystems. For reference, coastal habitats represent about 2% of the oceans’ surface area yet are responsible for nearly 50% of carbon sequestered in marine sediments. These blue carbon ecosystems, nestled between the endless ocean and vast landmasses, represent a thin slice of Earth working overtime to regulate the climate.

Local Indonesian fisherman sourcing fish and shellfish in a pristine blue carbon ecosystem

How Blue Carbon Ecosystems Sequester Carbon

Coastal habitats capture carbon more effectively than their terrestrial counterparts due to their higher efficiency in converting solar energy into organic matter – often described as a high primary productivity rate. More importantly, blue carbon ecosystems trap sediment and organic matter such as leaf litter in their roots and allow that carbon to accumulate in the seabed. This process is known as “sedimentation” and accounts for 50 – 90% of all the carbon sequestered in these coastal ecosystems.

This ability to store carbon underground in soils and sediment is one of blue carbon’s most unique and essential functions. Aboveground biomass, such as the trees in a forest, will sequester and store carbon over its lifetime. However, at the end of the tree’s lifecycle, the tree will die and release carbon back into the atmosphere during the decomposition process. In contrast, belowground carbon sequestered by blue carbon ecosystems can remain undisturbed for hundreds or even thousands of years. A prime example is a seabed meadow off the coast of Spain that has accumulated over a 35-foot-thick carbon deposit over the span of 6,000 years. The stable and enduring nature of these reserves is created by the seabed’s saltwater and oxygen-deprived conditions, which slow the pace of decomposition and effectively trap carbon underground. Belowground carbon also represents a more resilient store of carbon stock as it is insulated against natural disturbances, such as fire and heavy rainfall, which are expected to become more frequent and intense as the climate continues to warm. Not only can carbon stored underground reduce the symptoms of the climate crisis, but it can also endure the worst effects of climate change.  

Mangrove restoration site at a local village in Aceh, Indonesia

Beyond Carbon

For the people connected to these ecosystems, the benefits of blue carbon extend far beyond combating climate change. Blue carbon habitats provide extensive benefits to biodiversity, local communities, and the millions of people dependent on them for their food supply. Aquatic plants found in these coastal blue carbon environments provide the shelter, nutrients, and water filtration services on which aquatic animals depend- simply put, many forms of animal life cannot survive without these foundational habitats. Flourishing coastal habitats increase food security and provide coastal communities with fishery and ecotourism opportunities. Mangroves and tidal marshes mitigate coastal erosion and insulate coastal communities from storm surges during extreme weather events. It’s been estimated that the annual value of the ecosystem services provided by blue carbon habitats hovers around $190 billion.

The world’s blue carbon ecosystems have a fundamental role in addressing climate change. Focusing our attention on the conservation and restoration of these precious ecosystems will have an immense impact in returning life to coastal waters and uplifting surrounding communities.

About the Authors

David Chen is passionate about nature-based solutions and developing carbon offset projects that protect and restore native ecosystems. From replanting bald cypress trees in the Mississippi River delta to reestablishing mangroves forests in international countries, David understands the positive impact these projects have on biodiversity, coastal resiliency and improving local livelihoods. David is a Program Development Manager at ClimeCo and has a Master of Environmental Management from Duke University’s Nicholas School of the Environment and received his Bachelor of Science from the University of California, Riverside.  

Daniel Frasca is an Associate on the Program Development Team specializing in nature-based solutions. He joined the team with previous business development, finance, and sales experience in the residential solar industry and leadership experience in the nonprofit sector. Daniel earned his Bachelor of Science degree in Management from Boston College, with a concentration in Finance and a minor in Environmental Studies.