How Mangroves Store Carbon - and Why It Matters

Dr Pierre Taillardat, Nanyang Assistant Professor at Nanyang Technological University and Principal Investigator of the Wetland Carbon Lab, shares about the importance of mangroves as one of the main Blue Carbon ecosystems, along with salt marshes and seagrasses.  

The term “blue carbon” was coined in a United Nations Environment Programme (UNEP) report published in 2009, to refer to these coastal forests with the aim of connecting scientific knowledge with policy making. The term was built on the earlier concept of “Green Carbon”, which refers to carbon stored in terrestrial forests.  

Blue Carbon ecosystems are some of the most efficient in absorbing carbon from the atmosphere and storing it in the ground for a long period of time. Dr Taillardat provides the analogy: “We can see the carbon cycle as a bank account. We are interested to know how much carbon is in the system, where it is being stored, and how it is moving between the atmosphere, oceans, and the rest of the ecosystem.” 

Through his work, the exchange of carbon gases, such as carbon dioxide and methane, between these various components is quantified. These gases are also known as “greenhouse gases” because they trap heat from the sun. And while heat is required for life on Earth to exist, too much in the atmosphere as a consequence of fossil fuel burning from human activities is causing Earth to heat up. Mangroves and other Blue Carbon ecosystems can help remove this excess of carbon from the atmosphere. 

Mangrove forests tick many boxes when it comes to effective carbon removal from the atmosphere. Firstly, they are highly productive vegetation which helps to absorb and store carbon in their biomass. Secondly, due to their waterlogged soils which are low in oxygen, decomposition of fallen plant matter is slow, which also helps to store more carbon in these ecosystems. Thirdly, with the protruding breathing roots of mangrove trees, sediments floating from other places and brought in by the tide are also trapped, enabling gradual accumulation of carbon-rich soil over time. 

Most of the world’s pristine mangroves are in remote locations which are difficult to access. The quantitative field-based data that Dr Taillardat gathers is needed to provide evidence for policy makers to “value” such ecosystems, in a quantitative way.   

The push for “blue carbon” has successfully incentivized the development and implementation of community-based mangrove conservation and restoration projects around the world.  

Dr Taillardat shares that one of their strengths is how they are often supported by international funding and organizations. Typically, they also engage local communities and provide economic benefits. However, he also notes some limitations: “The success rate of mangrove plantations is often poorly documented, and where data exist, survival rates can be disappointingly low. A key issue is that many projects rely on mechanical planting without adequately considering ecological and hydrological site conditions,” he elaborates. 

While much attention on mangroves focuses on their role as carbon offsets, Dr Taillardat emphasises that carbon storage is far from the only reason these ecosystems deserve protection. He notes: “Mangroves had some negative connotations in the past. They were seen as a muddy wasteland infested with mosquitoes with no economic value. But now Blue Carbon science helps spread the word that they are one of the most valuable ecosystems for the numerousecosystem services they provide. Other than for carbon sequestration, they are also important habitats for biodiversity, coastal protection against erosion and sea level rise, and a place for local communities where they can fish and generate income – these are also services that we should advertise.”