As humans continually add carbon dioxide to the atmosphere, getting rid of the excess greenhouse gas has become a priority. Scientists are searching for new ways to remove carbon from the atmosphere and put it into long-term lockdown.
The ocean’s ability to soak up carbon like a sponge is well known, but researchers are now taking a fresh look at ocean shores. Our planet has about 620,000 kilometers (372,000 miles) of coastline, long enough to wrap around Earth almost 15 times.
The 2016 Paris Agreement has intensified pressure on nations that signed the pact to meet carbon goals and find better ways to sequester carbon. There are many solutions, but deciding which is most effective—oceans, forests, mangroves, or kelp farming, for example—can be daunting. In addition, many studies use different timescales or measurements, further muddying carbon storage comparisons.
“The goal of the paper was to try and compare apples to apples,” said Jennifer Howard, lead author of the paper and marine climate change director at Conservation International in Arlington, Va. On 1 February, she and her colleagues published their detailed report online, which compares carbon storage by coastal blue carbon ecosystems to storage by algae and marine animals.
Carbon Storage Powerhouses
Plants take carbon out of the atmosphere, storing it in leaves, roots, and branches. On land, when vegetation falls to the ground, the bits break down quickly, releasing carbon back into the atmosphere. Not so in coastal wetlands. There, Howard explained, tidally driven salt water saturates soil twice a day in mangrove forests and tidal marshes and continuously in seagrass ecosystems, which are perpetually submerged. Saltwater inundation inhibits the microbial breakdown of plant debris, trapping it in the soil. The authors note that 50% to 90% of coastal blue carbon storage occurs in the soil, not the plants. “You can still see intact leaves 3 meters down,” said Howard. “The carbon is stable.”