Blue Carbon and wetlands

What are wetlands?

According to Ramsar Convention, wetlands are areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tide does not exceed six meters. In general, wetlands are unique ecosystems where water plays a crucial role in shaping the environment and supporting diverse plant and animal species.

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Examples of wetland from the Ramsar Classification

Marine/Coastal Wetland

  • Intertidal mud or sand flats
  • Mangrove swamp
  • Salt marshes

Inland Wetland

  • Rivers, streams, freshwater lakes
  • Peatland

Human-made Wetland

  • Wet agricultural lands
  • Aquaculture ponds

Why are wetlands important?

Wetlands are one of the valuable ecosystems on Earth, with a productivity as high as that in the tropical rainforests and coral reefs. Wetlands provide numerous ecosystem services for nature, wildlife, and human well-being:

Supply of
Food Resources

Flood
Control

Water
Purification

Carbon
Storage

Climate
Regulation

Biodiversity
Hotspot

Key Roles of
Coastal Wetland

What is Coastal Wetland?

Coastal wetlands include all wetlands in the coastal watersheds, from which tidal streams drain to the ocean or inland seas. They are influenced by both marine and terrestrial processes due to their unique location at the interface. Coastal wetlands experience the combined effects of tidal movements, wave action and the flow of freshwater from rivers, as well as the influence of terrestrial ecosystems and human activities.

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The magic power of coastal wetland – carbon sequestration

What is carbon sequestration?

Carbon sequestration refers to the process of capturing and storing carbon dioxide (CO2) from the atmosphere or other sources that would otherwise be emitted to, or remain in the atmosphere. It plays a crucial role in mitigating climate change.

Next, what is blue carbon?

Blue carbon refers to the carbon that is captured and stored in the marine and coastal environment. The term “blue” emphasizes the presence of carbon in the water.

So, how can coastal wetlands sequester significant amounts of CO2 effectively?

  1. Photosynthesis: Plants in coastal wetlands can undergo photosynthesis to absorb atmospheric CO2 and store the carbon in organic form in their tissues.
  2. Biomass accumulation: Coastal wetland plants exhibit rapid growth rates and have the ability to accumulate biomass at a significant pace. As they grow, they capture and store carbon in their aboveground and underground biomass.
  3. Sediment trapping: The vegetation in coastal wetlands acts as a physical barrier, trapping sediments and allowing them to settle on the wetland surface. This process leads to the accumulation of mineral sediment and organic materials, which contribute to the formation of carbon-rich deep soil.
  4. Slow decomposition: The waterlogged and anaerobic environment of coastal wetlands leads to a slow decomposition rate of organic matter. This increases the time for the organic carbon to remain in the wetlands instead of being broken down and released back into the atmosphere, which allows for a better performance in carbon sequestration.
Coastal wetlands have been found to store up to ten times more CO2 on a per unit area basis than terrestrial forests.[4][5]

Then, where is it stored in coastal wetlands?

Carbon deposits within these ecosystems are sequestered and stored in different compartments: Firstly, aboveground biomass such as tree trunks, stems and leaves. Secondly, belowground biomass comprises plant roots and rhizomes. Additionally, a significant portion of carbon (approximately 50-99%)[1][2][3] is stored in the soils of coastal wetlands, and persist for an extended duration when undisturbed.

Blue Carbon as a
Nature-based Solution

Healthy coastal wetland ecosystems can effectively sequester vast amounts of carbon dioxide from the atmosphere, store the organic carbon in their vegetation and sediments, and act as a significant carbon sink. This carbon sequestration ability helps to mitigate the greenhouse effect and reduce global warming, which is invaluable for us to cope with and adapt to the challenges of climate change. As a nature-based climate solution, the conservation and restoration of coastal wetlands can provide many other co-benefits including recreation and coastal protection.

Examples of blue carbon as a nature-based solution

Unfortunately, these coastal habitats are under increasing threat from destruction, putting them at great risk. Globally, less than 2% of the blue carbon ecosystems are included in marine protected areas[6]. When these ecosystems are disturbed, degraded, or converted to other land uses, the blue carbon stored within them becomes vulnerable and can be released back into the atmosphere, exacerbating the problem of climate change. This is why preserving and protecting coastal wetlands is so critical.

Blue carbon has gained increasing international attention. Blue carbon has been recognized in some international climate agreements, such as the Paris Agreement and the United Nations Framework Convention on Climate Change, as a nature-based solution that can contribute to achieving the climate goals and enhancing climate resilience. At the recent COP28 in 2023, blue carbon conservation had been put on the agenda and many countries had showcased their experiences and affirmed their commitment to restore and protect blue carbon ecosystems. It is hopeful that increasing awareness and commitment towards blue carbon will drive the continued efforts of coastal wetland conservation.

[1] Conservation International. (2019). The Blue Carbon Initiative: About Blue Carbon.

[2] Pan, et al. (2011). Science, 333, 988-993.

[3] Pendleton, et al. (2012). PLoS One, 7, e43542

[4] Mcleod, et al. (2011). Front. Ecol. Environ., 9, 552-560.

[5] NOAA's National Ocean Service. (n.d.). Coastal Blue Carbon.

[6] International Ocean & Climate Initiatives Alliance. (2017). Marine protected areas and climate change.