Mozambique, with 2,700 km of low-lying coastline and high exposure to tropical cyclones, is on the front line of the climate crisis. In recent years, devastating storms, floods and droughts – increasingly intense and frequent due to climate change – have affected thousands of people and killed hundreds in this southern African nation.
In 2021, the Mozambique Oceanographic Institute (InOM) The country has launched an experimental seaweed farming project in the north of the country. The initiative, which is financially supported by Selt Marine Mozambique, a subsidiary of the Tunisian seaweed farming and processing company Selt Marine Group, promises to combat climate change while improving marine biodiversity and restoring fishing activities.
First, suitable areas for seaweed farms in the ocean were identified, as were the most appropriate varieties for cultivation. Next, around 100 local people – mostly women – were trained to grow the plant by setting equidistant stakes in the ground and placing seaweed along wires and nets between the posts, a process that takes between five and seven days. For the next 60 days, the locals work with the InOM team to measure growth, detect signs of disease and remove harmful algae from the fields twice a week.
The hope is that seaweed farming will help remove carbon from the atmosphere by converting it into organic biomass. According to the Intergovernmental Panel on Climate Change (IPCC), to achieve the goal of 1.5°C global warming 1,000 gigatonnes of carbon dioxide (the equivalent of almost half of what humans have emitted since the Industrial Revolution) must be eliminated this century.
Algae have several Advantages over other carbon sequestration techniques. They grow very quickly compared to many other plants. They capture up to 20 times more carbon per 5,000 square meters than terrestrial forests and currently cover about 3.4 million square kilometers from the ocean. And they don’t run the risk of burning and returning carbon to the atmosphere like trees do. A 2016 report published in the scientific journal Nature He estimated that seaweed absorbs about 200 million tonnes of carbon dioxide a year. This is roughly equivalent to half of Australia’s annual emissions, the 16th largest emitter The hope is that Mozambique, with its vast Indian Ocean coastline, could become a major producer of seaweed, although clear challenges remain, including those arising from the climate crisis itself.
With the money I receive from this project I can buy food for my family, clothes and sometimes school supplies for my children.
Estefania Calisto, 33 years old, mother of eight children
The danger of ocean warming
“If climate change hits the ocean and there’s too much carbon in it, it will warm up and algae will start to die,” said Archibong Akpan, a climate policy expert at the United Nations Framework Convention on Climate Change. Warming oceans could also lead to an increase in algae that develop ice bleaching disease, which causes them to bleach like corals and may have affected one of the two species farmed in the InOM project, according to research assistant Henriques Bustani.[Las del género] Kappaphycus are not developing properly,” he says.
According to Valera Dias, a Mozambican scientist at Eduardo Mondlane University who started experimental algae farming in Mozambique in 2022 with support from the European Union, farmers can take steps to reduce the risk of disease. These include carefully choosing farming areas, cleaning fields regularly and adopting techniques such as the “bottom system,” which allows algae to be grown at greater depths so that they are less exposed to the sun.
Other researchers point to more significant limitations in seaweed’s potential to remove large amounts of carbon from the air. A 2023 study, For example, it indicates that the concentration of iron in the open ocean is insufficient to sustain algae growth. Worse still, an investigation from last year indicated that algae could in fact be a natural source of carbon, releasing 20 tonnes per square kilometre each year. This finding came about by taking into account the additional carbon emitted by organisms gaining more food sources from plankton gliding through the seaweed canopy.
“The idea of using carbon-absorbing seaweed as a means of improving atmospheric carbon levels is not credible,” says Craig Johnson, a professor of marine sciences at the University of Tasmania’s Institute for Marine and Antarctic Studies. The potential for seaweed to absorb carbon permanently – typically defined as at least 100 years – depends on what happens to the plant after cultivation, he adds. “In some cases, seaweed waste ends up in ocean sediments, where it can be buried for 100 years,” he explains.[Pero] If they are used for human consumption, most of the carbon is likely to return to the atmosphere through our metabolic processes.”
Seaweed aquaculture has many benefits for the environment. However, current evidence indicates that algae are not going to be the saviour of our climate crisis.
Craig Johnson, Professor of Marine Sciences at the Institute of Marine and Antarctic Studies at the University of Tasmania
Some varieties of seaweed are widely consumed in Asia and their popularity is growing in other parts of the world as well. The plant is also used to make various food additives, often thickeners or emulsifiers, which can be found in products such as ice cream and beer, as well as in cosmetic and pharmaceutical products. The size of the global seaweed trading market It was valued at $10.66 billion (about €9.6 billion) in 2024 and is expected to grow significantly in the coming years.
InOM’s project in Mozambique aims to tap into this market, although the initiative has only just begun. According to researcher Bustani, the group has collected 1.3 tonnes of dried seaweed since they began harvesting it in 2023. These quantities are not yet sufficient to start exporting.
Locals involved in the project say they have benefited from the extra work, for which they receive about two dollars a day. “The income from work helps me buy some food for my family,” says Muanatruco Rajbo, 30, who trained in May 2022. Her other sources of income, farming and selling firewood, are not enough to feed her family of four children.
Estefánia Calisto, 33, says that before receiving training in August 2023, her income from collecting shellfish on the beaches had decreased “due to problems with the [inusuales] rains. This additional source of income has provided her with a new lifeline. “With the money I receive from this project I can buy food for my family, clothes and sometimes school supplies for my children,” explains this mother of eight.
Bustani adds that the additional algae in the sea has also helped provide additional food sources for marine life and improved biodiversity. “Algae are friends of the ecosystem,” he says. “They are like a home for fish. Thanks to algae farming, we are seeing some species of fish that were not seen before.” He admits that high costs of inputs such as stakes, lack of a local market for materials such as tubular nets and funding problems are limiting the expansion of the project, but he is optimistic about its progress.
Given seaweed’s questionable potential to sequester carbon, especially at the levels needed to significantly mitigate climate change, the Mozambique project suggests that the potential benefits of farming may be far more evident and demonstrable locally than globally, at least for now. In Johnson’s words, “There are many good reasons to grow seaweed in an aquaculture setting, and seaweed aquaculture has many environmental benefits. However, current evidence indicates that seaweed is not going to be the savior of our climate crisis.”
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