Seaweed collectives in Zanzibar tap into ancient feminist practice and offer a glimpse into the future of food

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On an early August morning in the village of Paje on the eastern shore of Zanzibar, an island 15 miles off the coast of Tanzania, women gathered on the beach, carrying sticks, plastic bags, and black leather purses. As tourists did sun salutations on the soft sand, the women waded into the ocean, their skirts floating like lilies on the water.                                       

In front of them, rows of red and green bundles dotted the ocean, evoking winning lines in a game of Connect Four. The seaweed seedlings stretched as far as the eye could see. These women were there to harvest them.

Mwanaisha Makame, a seaweed farmer, stood knee-deep in the water, tending to her crop. The seaweed grows on thin raffia strings (tie-tie, in the local Kiswahili), attached to nylon ropes suspended between stakes, which are pegged to the ocean floor. Seaweed prefers white, clean sand, away from coral heads or other formations that attract algae-grazing fish. Like plants, seaweed relies on photosynthesis to grow, and can thrive in waters up to 16 feet deep. Unlike plants, the cellular structure of seaweed is flexible, and even while firmly attached to the strings, it will yield to the rhythms of the waves and tides.

The tides set the agenda of Makame’s day. Starting at 4 a.m., a few hours before sunrise, she prays, cooks, and cleans. Then, for the two weeks a month when tides are low—during the new moon and full moon— she works on the beach, harvesting seaweed, repairing ropes that broke during storms, and removing stones, seagrass, and silt from her crop. Work continues until about 4 p.m., when the ocean comes rushing in, and Makame, who does not know how to swim, returns home. For six weeks, the length of each growth cycle, seaweed gathers on the strings, amassing weight and nutrients before it is harvested.

As lunar cycles structure seaweed growth cycles, so has seaweed shaped the stages of Makame’s life: Profits from farming helped her gain financial independence and sent her 22-year-old daughter to college. In Zanzibar’s conservative Islamic society, married women are traditionally confined to their homes, and to domestic labor. Seaweed farming, and the additional income it brings in—up to 1,125,745 shillings (around $500) per year, compared to an average annual income of 1,263,100 shillings ($561)—have disrupted traditional gender roles. At the beach, women can work freely, earning money they spend at their discretion. “The fast money that I got from seaweed planting I used to build my own house,” Makame said. Before her daughter went to college, they would work together on the farm.

In this coastal village, life is cyclical. Steady demand for seaweed has kept more women in control of their incomes. But recent changes brought on by global warming have disrupted these routines.

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In Zanzibar, seaweed is a women’s business: The industry  employs 26,000 farmers, about 80 percent of whom are female. Farmers started growing seaweed commercially here in 1989, after two strains were imported from the Philippines. (In Asia, seaweed production has been big business for centuries.) Globally, seaweed yields a $6.4-billion profit. China is the world’s largest producer, followed by Indonesia and the Philippines. In Zanzibar, seaweed is the third-largest industry after tourism and cloves, bringing in about $2.4 million annually. Each year, about 11,000 tons of seaweed are exported from Zanzibar to Denmark, France, Spain, and the United States to produce carrageenan, an additive that thickens, gels, and stabilizes products like toothpaste, soap, and cosmetics. Carrageenan is also commonly used in foods, including processed meals, yogurt, and smoothies. Thanks to McDonald’s, Kraft, and Starbucks, millions of people eat seaweed every day without realizing it.

By 2050, the world will need about twice as much food to feed an estimated 9.6 billion people, according to a 2016 World Bank report. Producing a total of 500 million tons of seaweed for consumption per year—about 14 percent more than current levels—would add 10 percent to the global food supply over the next three decades. This could be done by cultivating just 0.03 percent of the oceans’ total surface area. And in the long arc of human history, eating seaweed may be a return to form. Last March, scientists in India suggested that red algae may be the oldest form of eukaryotic life on earth, and subsequently, the oldest food known to humans. Seaweed may also have guided humans on one of their most significant migrations in history. For much of the 20th century, archaeologists held that early peoples crossed the Bering Strait by walking across an ice corridor between what are now Russia and Alaska. This hypothesis was gradually overtaken by the Coastal Migration Theory, positing that settlers from Asia traveling by boat colonized the Americas via the Pacific, relying on Pacific Rim seaweed for sustenance. In other words, these voyagers on the “kelp highway” likely followed a marine version of the paleo diet, writes anthropologist Kaori O’Connor in Seaweed, A Global History. To more recent generations, seaweed is a slimy, smelly, “famine food,” foraged on the shores of Ireland during the Great Hunger of the 1840s.

There are other benefits to cultivating seaweed: It absorbs phosphorous and nitrogen from the atmosphere, it can be used as fertilizer, and its biomass can be turned into plastics, chemicals, and electricity. ExxonMobil, the largest U.S. oil company, has major investments in algae. Researchers at the University of Texas—the biggest collector of algae in the world, with 3,000 specimens—founded a startup, AlgEternal Technologies, which grows algae in 12-foot tubes in the hopes of one day extracting oil on a commercial scale. Although the technology is far from commercialization, in 2011, a U.S. passenger flight was the first to fly on a mix of algae biofuel and petroleum jet fuel.

There is just one problem, which Makame is now intimately familiar with. As climate change raises temperatures in both cold and warm waters, seaweed forests, the oldest ecosystems in the world, are slowly disappearing.

She shows me a bundle of Eucheuma denticulatum, the primary strain cultivated on the island. It’s pink and shiny, like frosting on a cake in a brightly lit shop, but the tips of the thalli look bleached—a telltale sign of a disease called ice-ice, which in recent years started infecting crops.

“It will completely die,” Makame says.


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During the hot season, between December and February, about 80 percent of Zanzibar’s seaweed harvest is lost. While the ideal temperature for seaweed is between 77 and 88 degrees Fahrenheit, water temperatures in Zanzibar now far exceed that. Ice-ice, the disease responsible for the failed crops, proliferates more easily in warm waters, said Claire Gachon, a senior lecturer in phycology at the Scottish Association of  Marine Science and a specialist in seaweed diseases. She likened the effects of climate change on seaweed to that of HIV on a person—it is rarely HIV itself, but rather opportunistic diseases that prove deadly. “The stress that their immune system is under makes them much more vulnerable,” she said, by means of comparison. All around the world, climate change has been linked to strange seaweed phenomena: In China, algal blooms—noxious, runaway growths of algae linked to warmer waters—nearly prevented  the 2008 Olympic sailing races when athletes’ boats got caught in a thick, slimy mulch. And in California, large tracts of kelp forests have been lost to global warming over the past  three years.

Flower Msuya, a senior researcher at the University of Dar es Salaam’s Institute of Marine Sciences, has studied seaweed in Zanzibar for more than 30 years. She confirms that environmental conditions are changing for the worse: “In the early 1990s up to the early 2000s, when we were measuring the temperature of the seawater, temperatures did not exceed 88 degrees. Now, when we go to the same areas—the shallow water areas—it goes all the way up to 98, 100 degrees Fahrenheit.” As a result, many villages have stopped growing cottonii (Kappaphycus alvarezii), a lucrative seaweed strain that produces particularly thick carrageenan. “Cottonii has the best price, but due to climate change we can no longer use it,” Makame told me.

When I met Msuya, who goes by Flower, at her office in the Zanzibari capital of Stone Town, she lived up to her name: She was wearing a button-down shirt with a floral print and sipping coffee from a mug adorned with pink blossoms. Raised near Kilimanjaro, the highest mountain in Africa, Msuya’s interest in botany was sparked by the fruit trees in her mother’s garden. As a student at the University of Dar es Salaam in the 1980s she turned her focus downward, to seaweed. Since then, she has published more than 70 scholarly, policy, and conference papers on the organism, earning a reputation as the “mother” of the Zanzibari seaweed farmers. All over the island, she is credited with putting roofs over women’s heads and enabling them to become more independent from their husbands. These advancements are often paid forward: Children ride to school on bicycles their mothers bought them, and fishermen have their wives to thank for boats purchased with seaweed profits.

In 2006, Msuya founded the Zanzibar Seaweed Cluster Initiative (ZaSCI), a network of academics, government officials, and farmers committed to improving the working conditions of seaweed farmers, in part by addressing the challenges posed by climate change. In July, she and Gachon were part of a group of scientists that received a $7.9 million grant from the U.K. government to develop disease-resistant seaweed strains that can withstand higher temperatures.

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In Zanzibar’s seaweed industry, men control the equipment, while women do most of the work. The system is set up as a monopsony,  in which one buyer per village controls the market and the means of production—seeds, sticks, and ropes—leaving little room for outside negotiation. The buyers, some of whom are foreigners, are always men; the farmers, all locals, primarily women. Zanzibari women haul about 1 ton of seaweed from the ocean per month, and 1 pound sells at 250 Tanzanian shilling ($0.10), or less, depending on the fluctuating market price of carrageenan. Yet, the workforce came to be mostly female for a dispiriting reason: Declining prices drove out most men, who cited too much effort for little reward: “Both men and women wanted to do the farming,” said Msuya, “but with time, the men were like, ‘Ah, wait, I have to plant, to harvest, to dry, and then how much do I make? $0.10 per pound?’ They said no.” To drag the harvest to the shore, and onto trucks to the capital, women sometimes employ carriers, whose wages further drive down profits. “It’s very big work, very hard work, but small pay,” Makame said. (For better or worse, pain relief comes cheap: At the end of a long day, seaweed can be ground, mixed with coconut oil, and massaged into the skin to soothe pain.)

To offset market pressures, Makame joined a women’s cooperative, Furahia wanawake (“Enjoy, women!” in Kiswahili), which is a member of ZaSCI. The collective, founded in 1998, divides a share of its profits among its members. Some of the money is set aside so the women can purchase materials together, subverting the dominant buyers. There are 15 seaweed collec- tives in Zanzibar, about one per village. Only 28 of Paje’s 500 seaweed farmers are members. Elsewhere, 1 to 5 percent of farmers are affiliated with cooperatives. Msuya hopes their numbers will grow, but they still face problems: In addition to the challenges of social conservatism, mass production and climate change have rendered ecosystems more vulnerable to disease and pushed out seaweed species native to Zanzibar. And as warmer temperatures continue to creep into shallow waters, women are forced to farm farther and farther offshore.

In a country where about half the population lives below the poverty line, some experts are skeptical about whether seaweed farming will make a difference. To really raise people out of poverty, according to the World Bank, you need more development. “If you really want to help poor people with seaweed, you can’t just do it on a small scale,” said Randall Brummett, a Washington, D.C.-based senior specialist of aquaculture and inland fisheries at the World Bank. “If you want to try and salvage these little communities, they need a much more robust economic basis.”

To justify that basis—by which he means building a processing plant—farmers would need to scale up and produce more seaweed. But, he added, there are technological and logistical barriers to doing so in Zanzibar. “There’s no more space close to shore—you can’t move in front of the hotel that’s up the way, and then there’s a rich guy that’s got a house on the other side. So you have to go out farther.” Reaching cooler waters means doing “what the Indonesians do,” Brummett said, “which is [use] floats and ropes from a suspending system.” Indonesia’s seaweed farms have certainly benefitted from this approach—they account for 27 percent of the global seaweed crop—yet Gachon, the seaweed disease specialist, warns that zeroing in on rapid industrialization means losing sight of the larger picture. Like many figures in the profession, she said, the World Bank “completely misses disease as an operational risk, and seems to focus on economic opportunities with little or no reference to environmental sustainability.”

With Furahia wanawake, Msuya is taking a one-step-at-a-time approach toward adopting a more sustainable system. She is currently piloting a project involving tubular nets—structures that prevent seaweed from breaking during storms—that will allow the algae to grow in deeper waters. “If we concentrate on developing these technologies,” she said, “then we are sure that the women will continue to farm seaweed.”


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In Asia, seaweed has historically been associated with motherhood and female environmental stewardship. Kathleen Drew, a British phycologist famed for discovering the life cycle of Porphyra, a red algae, is honored as the “Mother of the Sea” at a shrine in Japan’s Ariake Bay. (Her finding, published in Nature in 1949, led to the mass production of nori, the papery sheets used in sushi.) In South Korea, seaweed soup is traditionally given to new mothers after childbirth, a custom that originated after people saw whales—a symbol of longevity—eat the algae. In the West, meanwhile, misogyny lurks in the mythology around seaweed. Greek and Roman literature reflect a deep fear of the sea, which, teeming with female dangers—such as the Nereids, sea nymphs who wore seaweed skirts and seduced sailors into underwater caves—nearly prevented Odysseus from returning home. To ancient cultures that revered the land, seaweed evoked a fear of uncertainty and entanglement. “Algae” might derive from the Latin alliga, which translates as binding or entwining. This aversion was epitomized in Virgil, who once declared, “nothing is viler than seaweed.”

In 19th-century England, kelp lapped against the shores in abundance—brown forests of seaweed fractured light like stained glass, drawing women to admire it. Spurred by the enthusiasm of Charles Darwin, who hailed “these great aquatic forests” as more diverse than tropical rainforests, seaweed found its way into the popular imagination. While botany, and science more generally, was a field then reserved for men, women’s study of seaweed escaped social opprobrium, and they headed  to the beach in unwieldy petticoats and surreptitious boots. English children’s author and ardent seaweed collector Margaret Gatty praised the rush of strolling the beach alone, and in the seaside village of Ilfracombe, George Eliot’s seaweed-collecting excursions led to similar exaltations, of which she wrote, “so necessary is it for the eye to be educated by objects as well as ideas.” After seaweed mania ended in the 1890s, said Juliet Brodie, research leader of phycology at London’s Natural History Museum, which preserved some of the Victorian seaweed herbaria, overzealous collecting had wiped out at least two species common to the area—Codium bursa, which looks like a green football, and Padina pavonica, known as peacock’s tail, which is used in some luxury cosmetics. The episode offered a cautionary tale about what happens when humans disrupt seaweed ecosystems.

More than a century later, Msuya, Brodie, and Gachon, along with researchers in the U.K., Indonesia, and the Philippines, are poised to learn from those mistakes and carry on the legacy of women working with seaweed. With their $7.9 million grant, they hope to mitigate the risks of mass cultivation and train Zanzibari Ph.D. students in developing disease-resistant strains over the next four years. But perhaps the most striking aspect of their grant is that it acknowledges a role for seaweed on the international development aid agenda, which, “I think no one would have expected a year ago,” Gachon said.

In addition to the World Bank report, the United Nations development goals for 2030 included an emphasis on sustainable food production, which has in turn heightened the focus on seaweed. In May, Denmark, Finland, Iceland, Norway, and Sweden met to discuss the implementation of the U.N. agenda. The 2004 launch of the New Nordic Food Manifesto, a program designed to promote healthy foods, including seaweed, is expected to help the region reach the U.N. goals. At the meeting, Nordic leaders were offered a menu featuring seaweed, and at ongoing “seaweed events” across the region, celebrity chefs have offered tastings to curious passersby.

As the West warms to seaweed consumption, Zanzibari farmers are adapting to more immediate pressures. The path toward sustainability, Msuya and Brummett agree, is reaching cooler waters and producing locally. “What I see is Zanzibar having its own seaweed industry, instead of exporting raw materials. I see Zanzibar as an exporter of processed products,” Msuya said. But before Zanzibari women take on cooler waters and invest in tubular nets, they needed Msuya to take care of one thing. So she secured government aid to get them swimming lessons. “We’ll make sure they have life jackets when they work in the deep water, so that they will not be afraid if they fall from the boat,” she said. “We want them to overcome this fear, otherwise the men will take over.” “And that,” Msuya added, “is not what we want.”

Reporting for this story was supported by a grant from the International Women’s Media Foundation.