Blue Carbon Challenges and Opportunities
By Emily Vidovich. Emily has a background in environmental journalism and sustainability and is a member of the George Washington University Class of 2019.
The ocean is nature’s most powerful carbon sink—absorbing 25 percent of annual carbon emissions. Over the past century, the ocean’s ability to capture and store so-called blue carbon has been significantly reduced by coastal development, pollution, and habitat destruction. Restoring blue carbon ecosystems so that they can protect the planet from climate change will require a combination of conservation, restoration, and innovation.
Blue carbon coastal habitats—including mangroves, tidal marshes, and seagrass meadows—constitute only two percent of the ocean, but are responsible for half of its carbon absorption. Mangroves can store three to five times more carbon than terrestrial forests of the same size. Compared to tropical rainforests, sea grass and marshes absorb carbon four times more effectively. Macroalgaes—including seaweed and kelp—are also powerful blue carbon sinks. And small, fast-growing microalgaes have gained recognition for their powerful blue carbon sequestration.
Humans have destroyed over half of global mangroves in the process of building coastal developments and aquaculture farms. At least 30 percent of tidal marshes and sea grass meadows have been lost as well. And rising seawater temperatures has led to a decline in kelp forests. When these blue carbon ecosystems are damaged or degraded, they lose their capacity as carbon sinks and release massive amounts of previously stored carbon dioxide—up to one billion tons annually. This exceeds the annual emissions of the United Kingdom, France, and Italy combined.
The necessity of blue carbon ecosystem conservation exists within a complicated reality. Aquaculture, the world’s fastest growing food industry that employs 22 million people worldwide and plays a vital role in global food security, is one of the main culprits of blue carbon ecosystem destruction—Southeast Asian shrimp aquaculture is the primary driver of mangrove loss.
With aquaculture growth projected to continue, sustainable aquaculture practices must become a global priority. When better practices are instituted, it is possible for aquaculture to restore blue carbon ecosystems instead of destroying them. For example, several of the Subnational Climate Fund’s partner projects combine blue carbon ecosystem restoration and regenerative aquaculture. Seawater Solutions showcases this approach by revitalizing degraded African coastal land using seawater, and then creating mangroves and wetlands as well as sustainable aquaculture projects.
Similarly, in Southeast Asia, blue carbon aquaculture projects spearheaded by the IUCN are attempting to transform shrimp aquaculture. One of these projects, an Indonesian farm covering 100 hectares, is restoring its land so that 60 percent of the area will be covered in mangroves. The farm’s shrimp production methods also minimize negative environmental externalities—avoiding supplemental feeds, fertilizers, antibiotics, and chemicals.
While this project proves that it is possible for shrimp aquaculture and environmental restoration to occur simultaneously, there is still much progress to be made in reforming shrimp aquaculture. This challenge is compounded by the fact that Asian farms—primarily in countries that lack the funds and regulatory will necessary to establish and enforce widespread sustainable production—produce a vast majority of the world’s aquaculture, especially shrimp.
In 2022, North American aquaculture production made up only 0.5 percent of the global total. The resulting reliance on imported products equates to the U.S. seafood market funding the degradation of blue carbon ecosystems abroad. Increasing domestic sustainable aquaculture production would reduce reliance on unsustainable imported seafood, create market pressure to drive global industry reforms, and create economic opportunities.
The U.S. is primed to increase aquaculture production, particularly in California. NOAA has identified large swathes of the water off of California’s coast that are capable of supporting multiple aquaculture operations in an environmentally sustainable manner. Off the coast of Los Angeles, Pacific Mariculture is already developing the first offshore mussel farm in U.S. federal waters. Farmed mussels are zero-impact because they require no feeding, antibiotics, or chemicals. Mussels also clean the surrounding water and provide a structural habitat for other species. These positive externalities make mussel farming the aquatic archetype of regenerative agriculture.
Molluscs—including mussels—and algae are the aquaculture species most capable of restoring the environment and mitigating climate change. And they are also the aquaculture species that have seen the greatest increase in global production over the past decade.
Importantly, kelp and algae aquaculture are effectively manmade blue carbon ecosystems. Naturally grown algae has up to fifty times the carbon sequestration ability of trees, and when grown in bioreactors, algae becomes several hundred times more effective than trees at capturing carbon. Because of this, bioreactor-grown algae is a potent natural method of carbon capture and storage.
Fully harnessing the climate change mitigating power of algae aquaculture requires supporting the industry in countries with strong growth opportunities. A new study by the Subnational Climate Fund found that the Global South has vast potential to increase the capacity of seaweed farming—providing economic benefits while increasing blue carbon sequestration. Expanding this nascent blue carbon industry requires initiatives that develop, accelerate, and scale regenerative aquaculture technology.
Accelerating regenerative aquaculture is a cornerstone of AltaSea at the Port of Los Angeles, the world’s leading blue economy campus. At AltaSea, Pacific Mariculture and various other blue technology innovators are advancing technologies for regenerative bivalve and algae aquaculture. Many of these innovations involve growing bivalves, kelp, and even shrimp in bioreactors and closed-loop systems—the aquatic equivalent of greenhouse farming—instead of in the ocean. At scale, these technologies will be vital to protecting blue carbon ecosystems from the impacts of traditional aquaculture.
Also at AltaSea, the Kelp Ark lab has created a “biobank” that houses, cultivates, and preserves genetic diversity in kelp and algae species. The lab’s researchers identify and cross-breed strains of kelp that can withstand warmer, more acidic waters—helping these blue carbon ecosystems survive climate change. Kelp Ark is also building a genetically diverse seed bank of ‘farmable’ seaweed—species that simultaneously produce valuable byproducts and harness the power of algae to sequester carbon—that can be distributed to aquafarmers worldwide.
AltaSea’s regenerative aquaculture leaders recognize that conservation and innovation are both essential to the future of blue carbon. Kelp Ark and its partners rushed to collect and preserve kelp species impacted by the historically devastating 2025 Los Angeles wildfires. During coastal wildfires like the ones seen in 2025, ash, debris, and toxins like arsenic enter the ocean in large amounts. Rain exacerbates the problem, sending toxins and debris into the coastal environment and increasing the likelihood of kelp forest die-off. By collecting and safeguarding species from impacted ecosystems, Kelp Ark ensured these blue carbon ecosystems can be restored when conditions improve.
Enabling kelp forests, mangroves, and other blue carbon ecosystems to thrive safeguards their role as long-term carbon sinks, allows them to capture climate-damaging emissions, and prevents them from releasing previously absorbed carbon back into the atmosphere. In the fight against climate change, the importance of conserving remaining blue carbon ecosystems and restoring those that have been degraded cannot be overstated.