Beyond their imminent beauty, coastal areas across our planet, with mangroves, tidal marshes, and seagrass meadows do many vital things to help us deal with climate change. They protect us from storms and rising seas, stop the shore from eroding, keep coastal water clean, and give a home to important fish and endangered sea creatures. They’re also a source of food for communities living by the coast. Plus, these ecosystems soak up significant amounts of carbon from the air and ocean, which is necessary for fighting climate change. (Initiative, n.d.)
Despite their major benefits, coastal blue carbon ecosystems face significant threats, with 340,000 to 980,000 hectares being destroyed each year. Globally, up to 67% of mangroves, 35% of tidal marshes, and 29% of seagrass meadows have been lost. If current trends persist, an additional 30–40% of tidal marshes and seagrasses, along with nearly all unprotected mangroves, could be lost in the next century. When these ecosystems are degraded or lost, they can become major sources of the greenhouse gas carbon dioxide. (Initiative, n.d.)
What is Blue Carbon?
Blue carbon refers to carbon dioxide absorbed from the atmosphere and stored in the ocean, with “blue” indicating its watery storage. The majority dissolves directly into the ocean, while smaller amounts are stored in underwater sediments, coastal vegetation, soils, DNA, proteins, and ocean life. Climate change agreements are increasingly focusing on coastal blue carbon, such as carbon stored in saltwater ecosystems like forementioned tidal marshes, mangroves, and seagrass meadows. Despite their small global footprint, these ecosystems can bury much more carbon per acre than tropical rainforests due to their deep, water-logged soils. Alternatively, disturbed, or drained coastal ecosystems can release significant carbon dioxide, protected or restored ones become vital for offsetting emissions, particularly for low-emission island nations and developing countries. The multifaceted benefits of these ecosystems, including wildlife habitat and hurricane protection, make strategies for their protection and restoration likely to play an expanding role in U.S. and international climate policy in the coming years. (LINDSEY, 2022)
Biology of Coastal Blue Carbon
Coastal blue-carbon ecosystems, notably these salt marshes, mangroves, and seagrass meadows, are recognized for their carbon storage potential. Seagrass beds, consisting of flowering plants thriving in salty marine environments, and mangroves, found in coastal swamps subject to saltwater flooding, contribute to this storage. Salt marshes, dense configurations of salt-tolerant grasses, herbs, and shrubs, flourish between land and open salt water.
All vegetation absorbs atmospheric carbon dioxide, utilizing it to develop roots, leaves, and other components. When animals consume plants, they disperse captured carbon throughout the ecosystem. In flooded soils, where oxygen is scarce, decomposition is slower, allowing these soils to retain atmospheric carbon for centuries or even millennia. Disturbed or drained, these soils become carbon sources as plant growth halts, exposing blue-carbon soils to oxygen and triggering rapid microbial decomposition, releasing carbon dioxide back into the atmosphere. (Initiative, n.d.)
Seaweeds like kelp, often excluded from blue carbon discussions due to the complexity of accounting for their carbon fate, grow rapidly, consuming substantial carbon dioxide. Although they typically grow in areas with minimal carbon-rich soil build-up, kelp can sequester carbon for thousands of years when buried in deep seafloor sediments. Estimates suggest that the annual carbon absorption by kelp ecosystems may surpass that of other coastal blue-carbon ecosystems. Additionally, kelp can be farmed for food or other plant-based products, showing promise in mitigating ocean acidification in oyster habitats. Despite these advantages, uncertainties about the destination of stored carbon have delayed the inclusion of kelp forests and other macroalgae in plans and policies for reducing atmospheric carbon dioxide. (LINDSEY, 2022)
Benefits of Blue Carbon Initiatives
Coastal ecosystems are like compact carbon powerhouses, holding 10-24 billion metric tons of carbon. They stash away 30-70 million more each year, a fraction compared to oceanic carbon dioxide (40 trillion metric tons) and global vegetation (450-650 billion metric tons).
Blue-carbon ecosystems, key players in carbon mitigation, contribute 126 million tons to sediments beyond vegetated areas. They’re responsible for about half of the annual carbon burial in coastal zones, even without counting kelp. These coastal heroes, like seagrass, outshine larger counterparts. A square meter of seagrass locks away over half a pound of carbon annually which is triple tropical rainforests, seven times temperate forests, and ten times grasslands. In our crowded world, preserving these efficient carbon sinks could be more practical than safeguarding larger, less productive areas. (Understanding Blue Carbon, n.d.)
However, if these natural gems are disturbed, they unleash massive CO2 emissions. A thin coastal fringe of tidal marshes, mangroves, and seagrasses contributes disproportionately to land-use carbon emissions—2-6% of tropical forest area but up to 19% of deforestation emissions.
The beauty of coastal blue carbon? They’re everywhere, except Antarctica. Recognizing them in national emission reduction plans offers a diverse range of countries carbon credits for protecting natural lands and enjoying coastal ecosystem benefits. (LINDSEY, 2022)
Examples of Blue Carbon Projects
Blue carbon projects are diverse initiatives aimed at harnessing the carbon sequestration potential of coastal and marine ecosystems. One approach involves reforesting mangrove areas along coastlines, recognizing their pivotal role in sequestering carbon and providing critical marine habitat. Another strategy focuses on the restoration of seagrass beds, acknowledging their efficiency as carbon sinks and their importance in maintaining marine biodiversity. Additionally, efforts to conserve salt marshes, coupled with ongoing carbon monitoring, contribute to our understanding of these ecosystems’ carbon storage benefits while offering coastal protection. (Understanding Blue Carbon, n.d.)
Community involvement is integral to many blue carbon projects, as seen in initiatives that engage local communities in the restoration of these vital ecosystems. Such community-based efforts not only enhance carbon sequestration but also promote sustainable practices, creating economic opportunities tied to the health of these ecosystems. Furthermore, education and awareness campaigns play a key role in informing the public about the significance of blue carbon ecosystems and encouraging actions to protect and restore them. (Smoot, 2022)
To ensure the effectiveness of blue carbon projects, research and monitoring programs are essential. By establishing initiatives that collect data on blue carbon dynamics, adaptive management strategies can be implemented for the long-term health of these ecosystems. Moreover, international collaboration is crucial for scaling up blue carbon efforts as part of a broader strategy for carbon offsetting and global climate change mitigation. Blue Carbon projects are multifaceted in nature, emphasizing the importance of local engagement, education, and global cooperation in the ongoing battle against climate change. (Reef Resilience Network , n.d.)
A number of existing mechanisms exist that encourage climate change mitigation through conservation and restoration of natural systems. Many of these mechanisms can be adapted and applied to coastal blue carbon ecosystems. However, most of these opportunities focus on carbon found in the above ground vegetative biomass and do not currently account for the carbon in the soil. International policy bodies like the United Nations Framework Convention on Climate Change (UNFCCC) and others are including blue carbon in their discussions of natural ecosystems. Relevant mechanisms such as Reducing Emissions through Degradation and Deforestation (REDD+) and National Appropriate Mitigation Actions (NAMAs) are emerging as means for developing countries to access international carbon mitigation financing streams and to implement programs and policies on the national level. On a local scale, carbon market initiatives are being developed to help fund climate mitigation actions that may include coastal ecosystem conservation. And voluntary carbon markets seem likely as a source of financial support for coastal ecosystem conservation and restoration activities. (Initiative, n.d.)
Coastal ecosystems, vital for carbon capture, offer diverse benefits like supporting livelihoods, stabilizing shorelines, and filtering runoff. Existing national and international policies protect these ecosystems, making it easier to include blue carbon considerations. However, development pressures have led to significant losses in salt marshes, mangrove forests, and seagrass meadows. Climate change exacerbates the challenge, forcing coastal vegetation to migrate inland, but development limits this movement. Introducing carbon credits could assign monetary value, safeguarding these ecosystems from development and preserving their benefits.
By Jarett Emert