What is “Blue Carbon”? Blue Carbon is the term coined for carbon dioxide (CO2) stored in the world’s coastal and marine ecosystems such as mangroves, saltmarshes, and seagrasses. It’s called “Blue” Carbon because of its proximity to the ocean: it is stored mostly in the soil and silt up to 6 meters under the seabed. Besides coastal Blue Carbon, there is also “deep sea carbon”. Each type is measured using a specific methodology to understand its impacts and benefits. Why is Blue Carbon important? Oceans are the largest heat sink on the planet, absorbing 90% of the excess heat caused by climate change and 23% of human-caused CO2 emissions. Blue Carbon is critical because of the multiple benefits that it offers. First is the huge storage capacity of Blue Carbon coastal ecosystems. They cover just 2% of the total ocean surface, but account for 50% of the ocean’s carbon absorption. For example, one hectare of mangroves stores five times more carbon than a similar area of forest on land. Seagrasses are another type of coastal ecosystem critical for carbon storage. Stopping seagrass destruction and degradation worldwide could save up to 650 million tons of CO2 emissions annually, roughly equivalent to the entire annual emissions of the global shipping industry. Second are the benefits that protecting and restoring these ecosystems have on making people and communities more resilient, such as reduction in flooding and erosion, storm protection, and increased job creation and food security. Third is the potential for healthy mangroves, seagrasses, and saltmarshes to generate high quality carbon credits, which, once verified and sold through transparent carbon markets, can earn additional income for local communities. In spite of their multiple benefits, coastal areas storing Blue Carbon have been seriously eroded, with more than 50% of the world’s original salt marshes lost during the 20th century. Up to 35% of mangroves were destroyed through deforestation in the 1980s and 1990s, and an estimated 25% of total seagrass beds lost to date. How does Blue Carbon fight climate change? Healthy ocean and marine ecosystems are essential to fighting climate change. Coastal ecosystems store carbon in soils and dead natural matter such as broken twigs and dead leaves that gather on the ground in the shallows. For example, seagrass has a unique ability to prevent organic carbon from decomposing back into CO2 and carbon in seagrass is stored to six meters under the seabed in the silt on the ocean floor. Blue carbon ecosystems can store larger quantities carbon compared to terrestrial forests for two reasons: First, their plants naturally grow quickly, and in the process, capture large amounts of carbon dioxide. For instance, juvenile red mangroves can grow up to 5 feet in a single year. This fast rate of growth enables mangrove forests to bounce back quickly from climatically induced events like hurricanes. Second, their soils are largely anaerobic (do not have oxygen) so the carbon dioxide gets incorporated into the soils, decomposes very slowly and can be stored for hundreds or even thousands of years. Many countries are optimizing their marine and coastal natural assets in a way that contributes to the economy and to the health of those marine ecosystems and the planet. What are the barriers to Blue Carbon or Blue Carbon conservation? We know how important the accurate measurement and verification of carbon storage is. Whereas highly robust and sophisticated methodologies have been developed for forests, those for Blue Carbon are still in development. Blue Carbon habitats may have different carbon sequestration potential, which makes it difficult to estimate and compare the carbon potential between projects. Another big challenge is ensuring emission reductions are permanent; that they won’t occur elsewhere in the future. There are some challenges around this because of other factors impacting ocean and marine ecosystems: what happens on the land affects the sea and vice versa, as these ecosystems are all connected by water. Measures for Blue Carbon conservation Protect and restore coastal ecosystems for their role in reducing impacts of global climate change. Promote and build essential scientific knowledge about these ecosystems Marine Protected Areas (MPAs) and other area-based management efforts offer opportunities for no-regret climate change tools and are now needed more than ever for sustaining a functioning ocean which continues to serve as a carbon sink. Establish global and national policies to enable blue carbon restoration and conservation projects and sustainable management initiatives that improve the livelihoods of coastal communities. Research into the sequestration, storage and loss of carbon from blue carbon systems Sources: What You Need to Know About Blue Carbon - World Bank Climate explainer series The International Blue Carbon Initiative