A chance emerges for the planet … and from a most unlikely source — seaweed

‘We need to give our children hope and solutions. Otherwise, they will just stop fighting’

Fairy stories for children usually don’t come true, but those about changing climate will. Vincent Doumeizel was so worried about the negative impact that the issue was having on his children that he decided he had to make a change in his own career.

The result is The Seaweed Revolution, his recently published book which “offers hope” amid our environmental crisis, he says.

It shines a spotlight on seaweed, which Ireland is rich in, and its many qualities, ranging from carbon capture to animal feed to human health and nutrition.

I had been working in the food industry for 20 years, and began to realise the planet could not feed its growing population, with one billion people starving and an additional 250,000 people to feed daily

—  Vincent Doumeizel

“My main motivation, initially, was to have something positive to offer my children,” he says. Illustrations of various seaweed types in his book were drawn by his teenage daughter, Neige Doumeizel.


Doumeizel, from Burgundy in France, is senior adviser on the oceans to the United Nations (UN) Global Compact, a non-binding UN pact to encourage businesses to adopt sustainable and socially responsible policies. He is also director of the food programme at the Lloyd’s Register Foundation independent charity.

“I had been working in the food industry for 20 years, and began to realise the planet could not feed its growing population, with one billion people starving and an additional 250,000 people to feed daily,” he says.

“For the next 50 years, we are going to have to produce as much food as we ever produced as human beings over the last 10,000 years,” he continues.

“How can we do that? It won’t be possible on land. We have to look to the oceans, which cover 70 per cent of the planet but only contribute to two per cent of our food and calorie supply,” he says.

“Of course, we are worried about human impact on the oceans, with acidification, pollution and all those issues. But if we want to repair the ocean, we have to start with the lowest trophic level, and that’s the level where seaweed thrives.”

As Doumeizel says, it’s not just in Ireland that seaweed has been misunderstood. He believes hunter-gatherers knew its qualities. He tracked how the first settlers in the Americas who came from Asia 13,000 years ago sustained themselves by taking a giant kelp (Macrocystis) route up the Pacific.

Closer to his own home, he found that sixth-century Irish monks introduced seaweed recipes to people living on unproductive land in northwest Finistère in Brittany, In more recent centuries, Aran islanders depended on seaweed to turn sand and rock into fertile soil.

He blames the Greeks and Romans for “writing seaweed out of history”, as they lived on a Mediterranean coastline which was warm and enclosed. Latterly, seaweed has been negatively associated with invasive algal blooms, a feature of increasing pollution once large European cities were constructed.

“It is no coincidence that the only place not colonised by Europeans in the 19th century is north Asia, as in Japan and Korea, where seaweed is central to diet,” he says.

There are thousands of types of macroalgae in the oceans, and more than 600 species in Ireland, of which some 13 species are used. Doumeizel points out that farming seaweed was almost “non-existent” at the turn of the last century, but took off in Asia due to the need to feed growing populations.

Asia now grows about 98 per cent of 35 million tonnes of seaweed sold worldwide, feeding almost two billion people and employing millions, he points out.

Seaweed is the healthiest food you can get on the planet — anti-fungal, antibacterial, antiviral and anti-inflammatory

—  Vincent Doumeizel

“So Asia has been ahead of us for those important reasons, but also because these cultures tend to view food in terms of health properties, and not just for supplying energy,” Doumeizel says.

“Seaweed is the healthiest food you can get on the planet — anti-fungal, antibacterial, antiviral and anti-inflammatory,” he says.

Higher consumption of sea vegetables — as they should really be described — is often cited as one of the reasons for a very low incidence of obesity, diabetes and cardiovascular issues in Japan and South Korea.

Alginates, polysaccharides produced by a wide variety of brown seaweed, have been used in dressings for many years to activate wound healing. They are also used in making dental impressions and regenerating cell tissue, while the most common medications to protect the stomach lining or prevent reflux are alginate-based, he says.

Farmed animals benefit from seaweed, as it boosts their immune systems, and there is now ongoing research on using a red seaweed named Asparagopsis in cattle feed to reduce methane emissions.

However, seaweeds also have other environmentally friendly properties, Doumeizel says, the most compelling being their ability to absorb carbon at a better rate than any terrestrial biotope.

He describes how the proliferation of a small aquatic plant named Azolla, also known as mosquito fern, duckweed fern, water fern or fairy moss, is believed to have influenced a 20-degree drop in the planet’s temperature some 50 million years ago.

Doumeizel cites Australian environmentalist Tim Flannery, who argues that if 9 per cent of the world’s oceans were properly managed to cultivate seaweed, these areas would absorb more greenhouse gas emissions than we emit today.

I am not saying that seaweed has all the answers, and this is not an excuse for inaction

—  Vincent Doumeizel

He recounts how Portuguese marine ecologist Carlos Duarte and Ocean 2050, an NGO led by Alexandra Cousteau, are involved in a research programme to calculate the level of carbon sequestered in 23 existing seaweed farms around the world.

After his book’s publication, Doumeizel met French president Emmanuel Macron twice, resulting in a decision to prepare a seaweed strategy in France.

The first EU Algae Awareness Summit will be held in early October 2023 at the Maison de l’Océan in Paris and France is hosting a UN Ocean Summit, which will include discussions on the topic, in 2025.

“I am not saying that seaweed has all the answers, and this is not an excuse for inaction,” he says.

“We should curb our emissions anyway, but you don’t build anything out of the fears and drama we have passed on to our children, and we need to give them hope and solutions. Otherwise, they will just stop fighting.”

  • The Seaweed Revolution: How Seaweed Has Shaped Our Past and Can Save Our Future by Vincent Doumeizel, with illustrations by Neige Doumeizel, and translated by Charlotte Coombe is published by Legend Press.

Cultivating a natural resource

For decades, Ireland appeared to ignore the potential of its seaweed resource, with State-owned company Arramara Teo exporting much of its wild harvest to Scotland for processing.

Back in 2014, Arramara was sold to Canadian company Acadian in a deal which caused some unease over the 10-year embargo on the actual figures.

However, greater appreciation of its potential is reflected in the seaweed strategy drawn up by Bord Iascaigh Mhara and the work being undertaken at Bantry Marine Research Station in west Cork.

As Julie Maguire, research director at Bantry explains, of some 600 species of seaweed, 13 are wild-harvested or farmed.

“Ascophyllum nodosum or feamainn bhuí is harvested, and then 95 per cent of farmed seaweed tends to be one of the kelp species,” she says.

“Ireland is producing a total of 30,000 tonnes annually, mainly wild, whereas in Asia some 95 per cent of all seaweed [is] farmed. However, farmed seaweed is beginning to pick up here,” she says.

The Bantry research station began cultivating seaweed 10 years ago and has two farms — one comprising six hectares in Bantry Bay and a 16-hectare farm in Roaringwater Bay.

“We now produce the seed for 13 companies growing seaweed in Ireland and some have multiple sites,” she says. “With a streamlined procedure, licensing doesn’t take quite so long, and so there were 180 hectares of farmed seaweed in 2021, 254 hectares in 2022, and now there is a total of 522 hectares awaiting a decision. The UN has a seaweed manifesto which is very aspirational, but the EU has a 23-point plan which requires member governments to take certain actions.”

Researching the potential for seaweed in agricultural feed to lower emissions is one of many projects in which the Bantry station is involved.

“We hope to work on trials with Teagasc over the next winter-spring on the impact of Asparagopsis armata in animal feed,” she says.

The Bantry station scientists are also involved in the EU-funded Ultfarm project to develop six pilot seaweed aquaculture sites on wind farms in the Baltic and North Seas.

“There are big gaps between wind turbines where there is nothing going on, and so there are pilot trials with seaweed, and also shellfish and mussels between turbines,” says Dr Maguire.

“This may push the technology in seaweed farming to a whole other level. For instance, if a big storm comes in, you need to have a remote way of dropping the lines. One issue with offshore sites is that there are far more nutrients nearer [the] coast, so growth is not as good further out,” she says.

Lorna Siggins

Lorna Siggins

Lorna Siggins is the former western and marine correspondent of The Irish Times