Restoring seagrass beds for climate protection

Off the northern German city of Kiel, divers use hand trowels to dig emerald-green seagrass shoots, complete with roots, out of a dense underwater meadow and carefully shake off the sediment. On land, they store the shoots in large coolers before heading to a barren area further north the following day to replant them in a circle.

Divers collect flowering seagrass to harvest the seeds. The SeaStore research project in Kiel, led by the GEOMAR Helmholtz Centre for Ocean Research, is one of the first to train local residents to restore beds of seagrass in the Baltic Sea.

Beds of seagrass act as huge natural sinks that can store millions of tons of carbon. However, they have sharply declined in the past century due to deteriorating water quality, according to scientists.

Angela Stevenson, postdoctoral researcher at GEOMAR, leads the seagrass initiative in the Baltic Sea. She has established three test fields in recent years and found that the shoots are more resilient than the seeds. "Our aim is to scale it up after this pilot period," said Stevenson. "The ultimate goal is to regreen the Baltic Sea."

"It's like underwater gardening," said Lea Verfondern, 21, a veterinary assistant who was part of the first batch of residents to attend the training in early July. "Everyone should make a contribution to protecting the environment because it affects us all." Verfondern, along with six other divers and some volunteers on shore, planted about 2,500 plants during the weekend course.

A stalk of seagrass with seeds (top) and a female flower with its pistil (bottom) are shown by a staff member. According to a 2019 study, Europe alone lost one-third of its regions of seagrass between the 1860s and 2016, which released carbon dioxide into the atmosphere and helped to accelerate climate change.

Even a glance provides an idea of how much work and time planting the seagrass beds requires. Stevenson estimates it would take half a million divers planting shoots for 12 hours a day for an entire year to restore all the seagrass lost in the Baltic Sea along the German coast.

Thorsten Reusch is a marine scientist at GEOMAR Helmholtz Center. In his laboratory, he is researching seagrasses' resistance to temperature increases. One hope is to breed heat-resistant strains, because seagrasses, unlike fish, cannot migrate to cooler climes when the oceans warm up.

Flowering seaweed collected for seed harvesting floats in a catch basin. "We will have to think up new technologies that help us remove carbon artificially, too," said Stevenson. "But if we have the nature-based solutions for storing carbon already, we might as well use it."