Blue Carbon : The Ocean’s Role in Combating Climate Change

Blue carbon refers to the carbon captured and stored by coastal and marine ecosystems, such as mangroves, tidal marshes, and seagrass meadows. These ecosystems play a crucial role in mitigating climate change by sequestering large amounts of carbon dioxide (CO₂) from the atmosphere, storing it in biomass and sediment for long periods. 

blue-carbon ecosystems account for around 50% of the total carbon that gets buried in the Ocean's coastal areas each year. As the world grapples with the increasing impacts of climate change, blue carbon ecosystems and their carbon storage potential is critical to shaping effective climate actions.

If degradation or destruction of blue carbon ecosystems continues, the world will lose one of the most effective components to fight climate change and biodiversity crisis. And coastal communities, especially in developing nations and small islands, will lose a critical resource on which they rely for their livelihoods, food and water security, and resilience to climate change impacts.

Blue Carbon Ecosystems 

Blue carbon ecosystems are highly efficient at capturing carbon. Unlike terrestrial forests, which store carbon primarily in plant biomass, marine or coastal ecosystems - mangroves, salt marshes, and seagrass meadows - store carbon in both biomass and the underlying sediments (soils). These sediments can hold carbon for thousands of years, making them one of the most effective natural carbon sinks. Hence the coastal ecosystems play an important role in climate change mitigation.

Salt marshes (Tidal marshes) and mangroves sequester carbon from the atmosphere at a rate 10 times greater than the tropical forests. The coastal habitats also store more carbon per acre than the tropical forests as they store carbon in soil rather than above-ground plants. 

Mangrove Ecosystem 

Mangrove forests, found in tropical and subtropical coastal areas, are among the most productive ecosystems on Earth. They capture carbon through photosynthesis and store it in their roots, trunks, and sediments. They store most of their carbon in the soil and dead roots. A hectare of mangrove forest can store up to four times more carbon than a similarly sized tropical rainforest.

Carbon sequestration rate of mangroves is two to four times greater than the rate of mature tropical forests. 

Seagrass

Seagrass meadows, underwater ecosystems found in shallow coastal waters, also play a vital role in carbon sequestration. They can capture carbon both from the water and from decaying organic matter. Seagrasses trap sediment, allowing carbon to be buried and stored for centuries.

Seagrass meadows hold more than 10% of the ocean's total carbon storage. Per hectare, it stores two times carbon dioxide than the rain forests.

Seagrass is characterized by salt water plants found in the shallow marine coastal water and in the brackish water of estuaries.

Seagrasses form dense meadows underwater. Seagrass beds or meadows are diverse and one of the most productive ecosystems as they provide food and habitats for diversity of marine organisms including fish and invertebrates (shrimp, crab) comparable to that of coral reefs. Some of the important sea species such as green turtle, Dugongs, manatees and sea urchin take shelter and get food in these meadows.

Seagrasses do photosynthesis using sunlight to meet their energy (food) needs in the submerged photic zone and help mitigate climate change by removing carbon dioxide from the atmosphere and sequestering it into sediments in the ocean floor. Seagrass meadows also keep the coastal waters healthy by absorbing bacteria and excess nutrients. 

Tidal Marshes

Tidal marshes are found in temperate and tropical regions, tidal marshes are salt-tolerant grasslands that are periodically flooded by tides. These ecosystems store large amounts of carbon dioxide in their roots and soil for hundreds or thousands of years because their soils are mostly anaerobic, which means they don't have oxygen.

The Importance of Blue Carbon in Climate Change Mitigation

Coastal ecosystems offer unique advantages in the fight against climate change. Their ability to store carbon is not only effective but also long-lasting, with fewer risks of the carbon being released back into the atmosphere compared to terrestrial carbon sinks. Here are some key points highlighting the significance of blue carbon in mitigating climate change:

1.High Carbon Storage Potential

Coastal ecosystems store 50% of the ocean's carbon absorption and sequestration rates are significantly higher than many terrestrial ecosystems. Mangroves, for instance, can absorb carbon up to 40 times faster than tropical rainforests. 

blue-carbon ecosystems are considered the ‘hot-spots’ for carbon storage as they store about half of the total carbon that gets buried in coastal ocean areas each year. 

In per acre area, deep, water-logged soils of coastal ecosystems can bury many times more carbon than even a tropical rainforest.

Coastal ecosystems are like a double-edged sword, if they get disturbed or damaged, they release the stored carbon into the atmosphere further increasing the atmosphere temperature and hence global warming.

2. Long-Term Storage 

Once sequestered, blue carbon can remain stored for centuries or even millennia. This is because the waterlogged soils in these ecosystems slow the decomposition of organic matter, reducing the release of CO₂ back into the atmosphere.

3. Co-Benefits for Biodiversity and Communities 

Beyond their climate benefits, blue carbon ecosystems provide essential services to local communities. They protect coastlines from erosion, provide habitats for fish, reptiles, mammals, birds, and a variety of invertebrate organisms, harboring a diverse array of marine life. 

 

The coastal blue carbon ecosystems also stabilize shorelines by trapping sediments on the seafloor by reducing the intensity of storm surges and wave action, keeping coastal waters clear in the process. They support the livelihood of people in poor countries through fishing and in rich nations, they support commercial fishing.

Blue carbon ecosystems filter runoff and slow the absorption of rainwater. They can help protect coastal communities from storm surges and flooding by absorbing some of the energy of storms like cyclones.

Protecting these ecosystems also helps preserve biodiversity, which is critical for building ecosystem resilience in the face of changing climate.

By including coastal blue carbon as a legitimate part of Nationally Determined Contributions (NDCs) of each country for reducing emissions, a large number of countries can get carbon credits for protecting and restoring these coastal habitats while reaping co-benefits.

Threats to Blue Carbon Ecosystems

Despite their immense value, blue carbon ecosystems are under significant threat emerging from both human activities and climate change.

Human Activities 

Human activities, such as coastal development, over-exploitation of marine resources, pollution, and unsustainable aquaculture, and conversion of wetlands for farming, are degrading or destroying these habitats. For example, mangroves are often cleared for shrimp farming or urban expansion, while seagrass meadows are damaged by dredging and nutrient runoff from agriculture.

Conversion of mangrove wetlands for shrimp ponds releases about 60% of stored carbon back into the atmosphere, according to one study.

Climate Change 

Rising sea level due to climate change is decreasing the space available for blue carbon ecosystems to grow into.

Climate change has increased the intensity of storms like tropical cyclones and hurricanes which in turn disrupt the natural structures of these coastal ecosystems.

The destruction of these ecosystems not only reduces their capacity to sequester carbon but also releases stored carbon back into the atmosphere, contributing to further temperature rise. It is estimated that the loss of blue carbon ecosystems contributes to around 3-19% of emissions from deforestation globally.

Strategies for Protecting and Restoring Blue Carbon Ecosystems

To harness the full potential of blue carbon in climate change mitigation, urgent action is needed to protect and restore these coastal ecosystems. There are some key strategies : 

Conservation : Protecting existing blue carbon ecosystems from further degradation is essential. This includes establishing marine protected areas (MPAs), enforcing laws against illegal logging, and regulating activities that lead to habitat destruction and reducing threats such as human activities that lead to the loss or degradation of coastal wetlands can help conserve blue carbon ecosystems. 

Restoration Projects : Efforts to restore degraded blue carbon ecosystems, such as replanting mangroves or rehabilitating seagrass beds, can enhance their carbon sequestration potential. Restoration also provides opportunities for coastal communities to engage in sustainable livelihoods through eco-tourism or sustainable fishing.

Inclusion in Climate Policy : Incorporating blue carbon into national and international climate policies is critical. Governments and organizations should recognize the role of blue carbon in achieving climate targets under frameworks such as the Paris Agreement. Additionally, financial incentives like carbon credits can promote investment in blue carbon conservation and restoration.

To Monetize Blue Carbon : In addition to gaining climate and biodiversity benefits from blue carbon ecosystems, there is also an opportunity to use blue carbon credits, which monetize the value of stored carbon in mangroves, seagrass beds, and salt marshes, as a source of revenue for local people. These ecosystems have significant carbon storage potential.

Example : The Mikoko Pamoja, first-ever mangrove conservation project in Kenya associated with the global carbon market, raises money by selling carbon credits and invests that money in conservation and plantation of mangroves. This also serves as a source of income for communities.

Designate New Ramsar Sites : Designating new Ramsar Sites can help protect and manage blue carbon ecosystems. Designation of Ramsar Sites provides these ecosystems with an international level of protection which slows down the average loss of coastal wetlands as seen in the mangrove forests in Ramsar Sites.

Conclusion

Blue carbon ecosystems are a powerful but often overlooked tool in the global effort to combat climate change. By conserving and restoring these essential habitats, we can not only mitigate climate change impacts but also protect biodiversity, support coastal communities, and safeguard ecosystem services. As the world searches for solutions to the climate crisis, blue carbon offers hope for a more sustainable future—one where nature is at the forefront of climate action. 

Protecting these habitats is not only a matter of environmental urgency; it is a critical component of a comprehensive climate strategy.