Seaweed farms offer many benefits. They provide food for people, habitat for fish and other organisms, and protection against erosion during storms. They can help prevent “red tides,” and could become a source of biofuel.

Seaweed stores carbon in the sediments on the ocean floor. That helps reduce the amount of carbon dioxide in the atmosphere, which is the major cause of our warming climate.

Wild seaweed forests already stash away huge amounts of carbon. Farms cover a much smaller area, so their benefit is smaller. But seaweed farming is a “growing” business—the yield has been increasing by more than seven percent per year. Almost all of the farming takes place in Asia. The United States is a minor player, but farms have been developed in New England, the Pacific Northwest, and Alaska.

Researchers studied the sediments below 20 seaweed farms in various parts of the world. The oldest, in Tokyo Bay, has been around for 320 years. The largest, in China, covers 58 square miles.

The scientists found that the amount of carbon in the sediments below the farms was twice that found in the surrounding sediments. And they found that as a farm ages, it becomes more efficient at “planting” the carbon.

Estimates say that seaweed farms could cover many times their present area by 2050. And the researchers said that if the farms are efficiently managed, they could become important weapons in the fight against our warming climate.