Bodil Vaupel has messed up the mussels. In her enthusiasm, the recent recruit to the sea allotment society in the pretty fishing village of Kerteminde in Denmark hung ropes so overstuffed with baby mussels that she was unable to lift them out of the water. “It was a total mess out there. They’re all helping to clean up, restock them and hang them up again,” says the painter and architect as she and two companions pull the straggly “beards” off mussels behind a dark wooden fishing shed. “But now,” she brightens, pointing to the bucket of mussels she is taking home, “I get all the rewards.” Made up of about 80 households, Kerteminde Maritime Haver is the largest of 15 sea allotment societies that have sprung up in Denmark since the first was established in 2011 in Ebeltoft, near the city of Aarhus. As with land-based allotments, members of a sea allotment society share an area granted to them by local authorities and use it to cultivate food. The difference is that instead of a field, growers share a patch of the ocean. In the case of Kerteminde Maritime Haver, it is the Great Belt – the strait between Funen island and Denmark’s capital island, Zealand. Here, ropes strung between buoys are hung with mussels and sea kelp. The original idea for sea allotments was for each member to have their own rope, or line, hung with mussels. “Everybody had an allotment, everybody had a line, but then some people didn’t keep them properly, so they decided to do it in common,” says Hanna Albert, as she carefully stuffs tiny baby mussels back into new cotton mussel socks. This is the way all Denmark’s sea allotments are managed now. At Kerteminde, the annual family membership fee is 500 Danish kroner (£60), which pays for using the harbour area where they prepare and hang mussels, and for renting the clubhouse from the local sailing club. While they get free access to the sea, the society pays into a fund to cover the costs of removing the equipment and remediating the area if something goes wrong. The importance of small clubs in Scandinavian life may partly explain the success of sea allotments. In Kerteminde, the municipality put an announcement in the local paper in 2015, seeking people interested in growing mussels collectively. The idea was to bring life back to the harbour, which had been progressively emptied of commercial fishing boats, due to declining stocks, reduced quotas and fishing bans. Before long, the first 20 enthusiasts had set up a society, with a chairperson, secretary and treasurer. Albert, a medical scientist, was among the pioneers. “We made a lot of mistakes,” she grins. “The biggest one was the eider ducks.” The Great Belt is like a motorway for migrating birds, Albert says. A single eider duck can eat 6kg of mussels a day, and the migrating flocks can contain as many as 25,000 birds. While production was great in the first year, in the second year the eiders spotted the ropes and ate the whole harvest. Members now take mussel ropes into the harbour in winter, when the eiders pass through, and set out new ones in the spring. The society has bought an old fishing boat, Elvira, which is kitted out with mussel farming winches. They have also begun growing sugar kelp in large quantities, and there are proposals to sink an old boat near the farm as a refuge for lobsters. According to Joachim Hjerl, founder of Havhost (Danish for “ocean harvest”), an umbrella group for Denmark’s sea allotment societies, there are now 1,700 people across the country actively engaged in 15 established sea allotment societies, with 10 on the way. Apart from a small project across the Oresund Bridge on the south-eastern tip of Sweden and one in Norway, Hjerl knows of no similar collective sea farming groups in any other country. “There’s a lot of conventional cultivation of these crops, but not by communities doing it on a non-commercial basis to feed themselves and their families. “That’s probably the unique thing about what we’re seeing in Denmark now, and starting to see in Sweden and Norway,” he says. Members decide at meetings what to grow, and also have small groups specialising in seaweed, mussels, boat maintenance, growing vegetables and, importantly, cooking their monthly mussel feasts. It’s not compulsory for members to help grow the mussels and seaweed – if they prefer, they can just eat the harvest. Outside the dinghy club building next to the pontoon, Ulla Due, in leather trousers and a bandana around her neck, is melting butter and rapeseed oil in a giant cauldron on an outdoor gas ring. She throws in garlic, onions, leeks and carrots, for what looks like a vegetable soup. Inside, members are laying out places for the 40 people here today. Once the vegetables have softened into a light broth, in goes a giant bucket of mussels, and the lid goes on. Everyone takes their places at the table, and bowl after steaming bowl comes out, piled with big, fat, yellow mussels. There’s a basket of crusty white bread and bowls of dried seaweed to sprinkle on for extra umami. As they eat, members talk about future projects, such as using sea kelp as fertiliser on their vegetable allotment or seaweed as a flavouring in beer. There’s also a broader mission. For Bernt Kjær Sørensen, the society’s chair, farming mussels and seaweed can help clean up the environment at the same time as helping solve the global food crisis without fertilisers or extra land. “Mussels filter water very effectively and take out excess nutrients, and seaweed is even better,” he says. “We want to spread the knowledge that we have so much food down in the ocean, but nobody is using it. We want to change that.”