At low tide along Zanzibar’s coast, thousands of women wade into the water to tend lines of seaweed that help support their households and communities. Their work has sustained a local industry for decades, linking the Tanzanian island to global markets. Now, researchers and public partners are looking for ways to help that industry withstand a changing ocean.
Seaweed farming is part of Zanzibar’s coastal economy, but it faces pressures familiar to marine industries around the world: rising temperatures, disease and shifting environmental conditions. The farmers have built deep practical knowledge over generations. The challenge, argue three advocates from government, the United Nations and research circles, is to pair that knowledge with science, investment and stronger tools for the future.
For many years, cultivation has relied largely on propagating existing stocks of Kappaphycus seaweeds, known locally as cottonii. That approach helped establish and expand the industry. But researchers now find that the genetic variety among cultivated seaweeds may have narrowed over time. As ocean temperatures rise and environmental stress grows more frequent, that limited range could make crops less able to cope.
Signs of the strain are already showing. Higher-value cottonii varieties that once grew well in shallow water have become harder to cultivate in many places. That can reduce farmers’ potential earnings and put more pressure on coastal livelihoods. The commentary stresses, however, that the farmers themselves are not the problem. Their experience and commitment are an asset to building a more resilient sector.
Collaborative research by Tanzanian and international partners has found that wild populations of Kappaphycus alvarezii still live in Tanzanian waters. These populations offer a source of genetic variety for study. Preliminary findings suggest some may have traits that help them withstand disease and heat stress, while also supporting higher-value production. The findings are not a quick fix, but they point to a possible long-term way to strengthen cultivated seaweed.
That work could include assessing the genes of wild and farmed populations, keeping samples safe in biobanks, and developing responsible breeding programs. The aim would be improved seedstock better suited to future ocean conditions. The authors say sustained investment will be needed to turn research into useful options for farmers.
The partnership described in the commentary brings together Zanzibar’s Revolutionary Government, the U.N. Joint SDG Fund and other organizations. The authors include Mwinyi, Zanzibar’s First Lady; Kurbiel, who leads the fund supporting the sector; and Krusoe, founder of AltaSea, which has taken part in international efforts to advance research and investment. They see science as a way to support, not replace, farmers’ traditional skills.
If research and investment grow alongside farmers’ knowledge, Zanzibar could strengthen both coastal incomes and its role in sustainable seaweed production. The future of the industry, the authors write, will depend not on hope alone, but on partnerships that bring science into traditional practice.