Climate Action

These blue carbon ecosystems could slow climate change

Almost a third of the world’s underwater seagrass forests have disappeared since 1879 and they are still shrinking by 11,000 hectares each year. Image: Unsplash/Leon

Douglas Broom
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The Net Zero Transition

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  • Seagrass, mangroves and salt marshes are all under threat.
  • But they could be a key weapon in slowing climate change.
  • They can help deliver the carbon cuts needed by 2050.
  • But we must act now to protect and expand them.

In the hunt for ways to curb the rise of carbon in our atmosphere, have we overlooked a vital marine solution? Seagrass, mangroves and salt marshes could absorb almost 1.4 billion tonnes of CO2 by 2050.

The problem is these are some of the world’s most vulnerable environments. Almost a third of the world’s underwater seagrass forests have disappeared since 1879 and they are still shrinking by 11,000 hectares each year.

The world’s total area of mangroves almost halved between 1990 and 2000 robbing the world of an important carbon sink. They are being lost at a rate of 2% a year, faster than any other type of forest.

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Mangroves are able to capture ten times the amount of carbon as forest trees and they store most of it in the sediments around their roots. Which means that, if they are left undisturbed, none of the carbon will be released back into the atmosphere for thousands of years.

Carbon storage potential of different forms of nature restoration.
The restoration of mangroves, saltmarshes and seagrass has huge carbon storage potential. Image: High Level Panel for a Sustainable Ocean Economy

Less than half of the world’s salt marshes survive and we are still losing them to land reclamation for agriculture and development at the rate of up to 2% a year. Grazing and the effect of invasive species is also helping to destroy this unique environment.


Blue carbon’s big three

Yet despite the rate of loss, these 'big three' blue carbon ecosystems still account for more than half of all carbon storage in ocean sediments. Together they cover almost 50 million hectares on every continent apart from Antarctica.

Global distribution of blue carbon ecosystems.
Global distribution of blue carbon ecosystems. Image:

Scientists say that ocean-based climate actions could account for a fifth of the annual cuts in greenhouse gas emissions that the world needs by 2050 in order to limit the rise in global temperatures to 1.5C.

Although blue carbon ecosystems only cover 1.5% of the area of terrestrial forests, their destruction releases a billion tonnes of carbon every year, equivalent to almost a fifth of the annual emissions caused by tropical deforestation.


What is the World Economic Forum doing on blue carbon?

Ocean-based Climate Action Areas to Mitigating Climate Change in 2050 (Maximum GtCO2e)
Role of five ocean-based climate actions to mitigating climate change in 2050. Image: World Resources Institute

But increasing protection for blue carbon ecosystems would prevent over 1 billion tonnes of carbon from entering the atmosphere by 2050, according to the High Level Panel for a Sustainable Ocean Economy, a group of world leaders that was joined by US President Joe Biden at the COP26 climate summit.

The panel advocates the use of blue carbon offset and global carbon trading schemes and public-private partnerships to raise funds for the restoration and extension of blue carbon environments.

Partnership for mangroves

Friends of Ocean Action, in collaboration with, has created the Mangroves Working Group to raise ambition and deliver action towards the conservation and restoration of mangrove forests. The aim is to enhance the blue carbon market and ultimately strengthen the resilience of coastal ecosystems and communities. The group will enable companies and investors to contribute to the conservation and restoration of mangrove forests with support from non-profit actors that provide complementary expertise and networks. It will also build the capacity of the demand side of the blue carbon market and connect it to mangrove-related projects and platforms.

The Mangroves Working Group will be accepting new corporate members wishing to elevate the agenda of mangrove conservation and restoration as well as blue nature-based solutions more broadly. Find out more here.

“With their value for both mitigation and adaptation, blue carbon ecosystems are a vital part to any climate change solution,” said Dr. Emily Pidgeon, senior director, strategic marine initiatives at Conservation International which is one of the members of the Mangroves Working Group.

The World Economic Forum’s 2021 report on Nature and Net Zero said natural climate solutions, like restoring blue carbon ecosystems, were fundamental to tackling climate change and could deliver around one third of global emission reductions needed by 2030.

As well as combating climate change, natural climate solutions could also play an important role in securing the recovery from the COVID-19 pandemic by delivering sustainable development and providing equitable livelihoods for some of the world’s most disadvantaged people.

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Climate ActionNature and Biodiversity
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