Blue carbon is the carbon stored in coastal and marine ecosystems like mangroves, tidal marshes, and seagrass meadows. These ecosystems absorb and store more carbon per unit area than terrestrial forests, and are increasingly acknowledged for their role in mitigating climate change. They also offer vital benefits for climate change adaptation, including coastal protection and food security for many coastal communities.
What’s significant?
Seagrasses, mangroves, and salt marshes along our coast act as “carbon sinks,” capturing and holding carbon. While most of this carbon is stored below ground and out of sight, it remains present. Surprisingly, the carbon found in coastal soil can be thousands of years old!
The broader concept of blue carbon emphasizes the conservation of coastal habitats. When these ecosystems are harmed or degraded, a significant amount of carbon is released back into the atmosphere, where it can exacerbate climate change.
Experts suggest that approximately 1.02 billion tons of carbon dioxide are released annually from degraded coastal ecosystems. This amount is equivalent to 19% of emissions from tropical deforestation worldwide.
Coastal ecosystems play a crucial role as globally significant carbon sinks and need to be conserved and restored. Despite their relatively small size compared to other ecosystems, they sequester and store substantial amounts of carbon in their soil. The continued destruction and loss of these ecosystems contribute to additional human-induced greenhouse gas emissions.
What steps to take?
Like tropical forests and peatlands, coastal ecosystems showcase how nature can be harnessed to enhance climate change mitigation efforts. They present opportunities for countries to meet their emissions reduction targets and fulfill their Nationally Determined Contributions (NDCs) under the Paris Agreement.
There is ongoing debate regarding the management of marine ecosystems in the high seas as a climate mitigation option and the use of the UNFCCC to incentivize better management practices. These ecosystems face challenges, including demonstrating globally relevant, long-term climate mitigation potential and jurisdictional issues related to management and carbon emissions or removals allocation.
Further discussion and dialogue are necessary to analyze whether and how an incentive mechanism for areas beyond national jurisdiction should be developed under the UN Climate Convention.
Types of Blues Carbon EcosystemsÂ
Mangroves
Mangroves, a type of tropical forest, thrive at the intersection of land and sea, regularly inundated by tidal waters. They rank among the most carbon-rich forests in the tropics. Experts estimate that mangroves sequester an average of 6 to 8 tons of COâ‚‚ equivalent per hectare annually.
However, over the past 50 years, global mangrove loss has ranged from 30% to 50%, with a continuing decline of 2% annually. This destruction is primarily due to deforestation for aquaculture ponds and unsustainable coastal development.
The emissions resulting from mangrove degradation are estimated to account for up to 10% of total emissions from global deforestation.Â
Seagrasses
Seagrasses are submerged flowering plants with extensive roots, forming meadows along the shores of all continents except Antarctica. These plants accumulate carbon over time, primarily storing it in soils that can be as deep as four meters.
Despite covering less than 0.2% of the world’s oceans, seagrasses sequester around 10% of the carbon buried in ocean sediment annually, totaling about 27.4 teragrams of carbon per year.
Seagrasses are facing significant threats, with global losses occurring at an annual rate of approximately 1.5%, which has been accelerating in recent decades. Around 29% of the world’s seagrass ecosystems have already been lost. Key threats to seagrasses include water quality degradation from land use practices like deforestation and dredging.
Climate change poses additional challenges to coastal vegetation. As sea levels rise, these ecosystems need to migrate inland to survive. However, increased development, such as buildings and pavement, often restricts their ability to move. This situation can lead to the gradual disappearance of these vital ecosystems.
One potential solution is to assign a monetary value to these ecosystems through carbon credits. This approach could help protect them from development pressures by highlighting their economic importance. By recognizing their multiple benefits for both people and nature, we can ensure that these ecosystems are preserved for future generations.
