Seagrass for Carbon Dioxide Removal

Seagrass meadows can remove atmospheric carbon dioxide (CO2) and help heal the planet. Oft-confused with seaweed, seagrass is not an algae, but more akin to an inverse amphibian: terrestrial plants wound up in the ocean and adapted to become seagrasses. By now, over 50 seagrass species take root in the ocean floor, cross-pollinate, and flower [1].

Like all plants, seagrasses use photosynthesis to convert CO2 to biomass. In doing so, they pull the greenhouse gas into the soil--a safe place for long-term sequestration. Compared to other plants, seagrasses are highly effective CO2 stores, achieving 60% the sequestration of the "green standards" (salt marshes and mangroves) and 30x more efficient sequestration than forests [2].

I'd argue seagrasses represent nature's best combination of carbon sequestration, available area, and proliferation speed [2]. Seagrasses are capable of thriving in ocean floors as deep as 100 feet (30 m) [3], making them less restricted to coastal lines than marshes and mangroves. Likewise, seagrass restoration in the Chesapeake Bay has seeded fast-growing meadows within a decade [4]. Once seeded, healthy meadows can sprout new ones when marine herbivores ingest and redeposit seagrass seeds [5]. The protection and expansion of seagrass meadows could have positive feedback loops far into the future.

Seagrasses, salt marshes, and mangroves are wet ecosystems collectively known as “blue carbon sinks” [6]. These blue carbon sinks are especially vital because they remove carbon from the oceans, which absorb 50% of all our CO2 emissions [7] and 90% of the heat trapped by greenhouse gases [8]. Blue carbon sinks thus maintain the flow of airborne CO2 into the ocean, with air-ocean interfaces driving more airborne CO2 into the ocean when the dissolved concentration of CO2 reduces. The same CO2 removal reduces ocean acidity, mitigating a harmful marine toxin.

What's more, seagrass meadows enhance coastal flood resiliency [9] and catalyze the development of entirely new marine habitats [10]. Seagrass proliferation not only helps mitigate climate change, but also helps to build aquatic ecosystems, bolster fishery outputs, and improve the safeties of coastal communities. Restoration projects should be supported by all.

If readers want to help out, you can implore coastal governments to pilot or expand wetland restoration or seagrass seeding. Otherwise, you might donate to the Smithsonian, the Virginia Institute of Marine Science, or the Florida Sea Grant, all of whom do excellent seagrass-related work.