Skip to Main Navigation
FEATURE STORYNovember 21, 2023

What You Need to Know About Blue Carbon

Climate Explainers Series visual, blue and red stripes

#ShowYourStripes graphic by Professor Ed Hawkins (University of Reading)

Did you know that coastal and marine ecosystems can store up to five times more carbon than forests, while providing a host of other benefits to communities? We spoke with Michele Diez, Senior Environmental Specialist, and Juliana Castano Isaza, Natural Resources Management Specialist, to learn about the benefits of “Blue Carbon” for people and the planet.

What is “Blue Carbon”?

Blue Carbon is the term coined for carbon dioxide (CO2) stored in the world’s coastal and marine ecosystems such as mangroves, saltmarshes, and seagrasses.  It’s called “Blue” Carbon because of its proximity to the ocean: it is stored mostly in the soil and silt up to 6 meters under the seabed.

Besides coastal Blue Carbon, there is also “deep sea carbon”. Each type is measured using a specific methodology to understand its impacts and benefits. The World Bank Group focuses on coastal Blue Carbon, namely mangroves, tidal marshes, and seagrasses, which come with accounting methodologies recognized by the Intergovernmental Panel on Climate Change (IPCC). Additional habitats may be added in the future.

Blue Carbon is the term coined for carbon dioxide (CO2) stored in the world’s coastal and marine ecosystems such as mangroves, saltmarshes, and seagrasses.


Why is Blue Carbon important?

Oceans are the largest heat sink on the planet, absorbing 90% of the excess heat caused by climate change and 23% of human-caused CO2 emissions. Blue Carbon is critical because of the multiple benefits that it offers.

First is the huge storage capacity of Blue Carbon coastal ecosystems. They cover just 2% of the total ocean surface, but account for 50% of the ocean’s carbon absorption. For example, one hectare of mangroves stores five times more carbon than a similar area of forest on land. Seagrasses are another type of coastal ecosystem critical for carbon storage. Stopping seagrass destruction and degradation worldwide could save up to 650 million tons of CO2 emissions annually, roughly equivalent to the entire annual emissions of the global shipping industry.

Second are the benefits that protecting and restoring these ecosystems have on making people and communities more resilient, such as reduction in flooding and erosion, storm protection, and increased job creation and food security. Our last Changing Wealth of Nations report calculated that mangrove ecosystems protect more than 6 million people from flooding annually and prevent losses of $24 billion in productive assets.

Third is the potential for healthy mangroves, seagrasses, and saltmarshes to generate high quality carbon credits, which, once verified and sold through transparent carbon markets, can earn additional income for local communities.

In spite of their multiple benefits, coastal areas storing Blue Carbon have been seriously eroded, with more than 50% of the world’s original salt marshes lost during the 20th century. Up to 35% of mangroves were destroyed through deforestation in the 1980s and 1990s, and an estimated 25% of total seagrass beds lost to date.

The World Bank, with support from the PROBLUE trust fund, has developed a Blue Carbon Readiness Framework  to empower governments to reverse these trends. The framework is a step-by-step guide on how to support investment in Blue Carbon to benefit people and economies and enable countries to meet their climate commitments under the Paris Agreement.

Our last Changing Wealth of Nations report calculated that mangrove ecosystems protect more than 6 million people from flooding annually and prevent losses of $24 billion in productive assets.

How does Blue Carbon fight climate change?

Healthy ocean and marine ecosystems are essential to fighting climate change. Coastal ecosystems store carbon in soils and dead natural matter such as broken twigs and dead leaves that gather on the ground in the shallows. For example, seagrass has a unique ability to prevent organic carbon from decomposing back into CO2 and carbon in seagrass is stored to six meters under the seabed in the silt on the ocean floor.

Blue carbon ecosystems can store larger quantities carbon compared to terrestrial forests for two reasons:

First, their plants naturally grow quickly, and in the process, capture large amounts of carbon dioxide. For instance, juvenile red mangroves can grow up to 5 feet in a single year. This fast rate of growth enables mangrove forests to bounce back quickly from climatically induced events like hurricanes.

Second, their soils are largely anaerobic (do not have oxygen) so the carbon dioxide gets incorporated into the soils, decomposes very slowly and can be stored for hundreds or even thousands of years.

Many countries are optimizing their marine and coastal natural assets in a way that contributes to the economy and to the health of those marine ecosystems and the planet. The World Bank is helping countries meet this ambition. For instance, a US$419 million project is supporting the Government of Indonesia to enhance the management of mangroves and the connected livelihoods of local communities.

What are the barriers to Blue Carbon or Blue Carbon conservation?
The Blue Carbon Readiness Framework aims to help simplify this complex space and offers practical steps for countries to maximize the impact of Blue Carbon.

We know how important the accurate measurement and verification of carbon storage is. Whereas highly robust and sophisticated methodologies have been developed for forests, those for Blue Carbon are still in development. Blue Carbon habitats may have different carbon sequestration potential, which makes it difficult to estimate and compare the carbon potential between projects.

Another big challenge is ensuring emission reductions are permanent; that they won’t occur elsewhere in the future. There are some challenges around this because of other factors impacting ocean and marine ecosystems: what happens on the land affects the sea and vice versa, as these ecosystems are all connected by water.

Take one example. Building a dam for energy purposes inland can impact the flow of fresh and clean water and block sediment from moving to mangroves growing in coastal areas. This could cause the mangroves to grow less effectively, and therefore affect their ability to store carbon – potentially causing emissions elsewhere. Through the Blue Carbon Readiness Framework, we are supporting governments to take a holistic approach to policy and nature management to ensure that one activity doesn’t negatively impact another.


Can Blue Carbon be measured and then traded in carbon markets?

Carbon sequestration and storage by mangrove, saltmarsh and seagrass ecosystems has been valued to be worth up to $190 billion per year. The World Bank is supporting governments to develop projects to bring high quality Blue Carbon credits to markets and earn a good price.

We want to be sure that we get this process right. We are helping build transparent carbon markets that can bring multiple benefits to communities in developing countries – financial as well as environmental, delivering a better quality of life and job creation for vulnerable groups including women and Indigenous Peoples and local communities.


How is the bank helping countries maximize the benefits of Blue Carbon?

The Bank is committed to addressing the nexus between climate change, oceans, and development. By restoring and protecting Blue Carbon habitats we are helping this mission across all three areas. We have recently seen this approach rolled out in countries, showing that the Blue Carbon agenda is gaining momentum on the ground. We are ready to take it to the next level to ensure that people and countries are empowered to play a meaningful role.

The readiness framework is an extension of this approach, with all the basic elements or conditions that are needed for countries to have a successful Blue Carbon project.

It is built around three pillars:

  1. Data and Analytics – developing greenhouse gas inventories and promoting the consideration of blue natural capital in decision making.
  2. Policies and Institutions – strengthening the enabling environment to maximize local benefits of Blue Carbon and leveraging partnerships to manage risks and influence the global agenda.
  3. Finance – adopting a holistic approach to mobilizing finance, accessing international grant funding for Blue Carbon readiness, promoting public-private partnerships for market development, and identifying value chains to reduce ecosystem degradation.

If we don’t protect these precious coastal and marine ecosystems, we will lose highly efficient natural carbon storage areas. This will mean more carbon in the atmosphere, which we know has a damaging impact on our climate. There are also multiple other rewards from restoring and protecting these precious habitats including job creation and food security.

Blue Carbon can play a major role in ending poverty on a livable planet. Working with governments, the private sector, and key partners, we are committed to delivering this mission by bringing together development, climate, and nature to feed, protect, empower, and uplift communities.   



    loader image


    loader image