June 10, 2024

Why sinking seaweed is not an answer to climate change

UN Ocean and Climate Dialogue should reject 'Blue Carbon' wave
Artist's illustration of industrial seaweed production

Even though the earth is burning, investors are being allowed to promote profit-generating climate projects in the UN – even projects that are unlikely to generate, and could even prevent, the reductions in carbon emissions that the world so urgently needs.

The planet’s oceans and their vast wealth of biodiversity are now in investors’ line of fire. They are promising that a so-called “seaweed revolution” will increase the ocean's capacity to absorb CO2 and generate profitable carbon credits – but our research shows these claims do not stand up to scrutiny.

Mass seaweed cultivation has been increasingly hyped since the UN Framework Convention on Climate Change (UNFCCC)’s Paris Agreement on climate change in 2015. By mid-2023 there were more than 1,300 companies involved in commercial seaweed, including more than 200 start-ups, and the global commercial seaweed market is estimated to reach US$25 billion by 2028.

Seaweed is a growing market dominated by agribusiness giants, mainly for food and ingredients, but this new “blue carbon” wave is ushering in new plans to grow large quantities of seaweed biomass with a view to physically sinking them into the deep oceans thereby capturing carbon and supposedly helping to cool down the climate.

However, it turns out that seaweed does not capture much carbon, and scientific evidence shows that, taking the whole production cycle into account, industrial seaweed ecosystems can actually lead to more CO2 in the atmosphere, not less.

In an article published in the ICES Journal of Marine Science, researchers put it this way: “Seaweed ecosystems, we found, were natural carbon sources, releasing on average around 20 tonnes per square kilometre every year. But it could be much higher still. (…) We estimate it could be potentially as high as 150 tonnes emitted to the atmosphere per km² every year.” To make things worse, those estimates don’t take into account the pollution caused by farming and dumping seaweed.

Second, the development of marine monocultures and the use of chemical inputs could harm existing ecosystems that naturally capture carbon and provide livelihoods to local communities.

The potential risks of seaweed plantations also include shading the seabed, seagrasses and natural algae, altering local ocean currents, contaminating genetic diversity and robbing plankton of vital nutrients.

The International Maritime Organisation (IMO) states that marine geoengineering technologies “have the potential to cause deleterious effects that are widespread, long-lasting or severe” and highlights that “there is considerable uncertainty regarding the effects on the marine environment, human health, and on other uses of the ocean”.

Third, carbon financiers are attracted to the ocean for its vast size and perceived untapped potential. However, the oceans are not empty. The areas most suitable for seaweed farming have cultural and historical significance and are often the basis for the traditional livelihoods of coastal communities. Industrial seaweed farms would need to occupy a significant portion of global coastlines to claim even a small impact on reducing greenhouse emissions. This would deprive local communities of their rights to live and to work in coastal areas.

Despite all of the above, industry is still lobbying for seaweed farming and sinking to be recognised as “sequestering carbon” in new carbon markets under the UNFCCC. Furthermore, even though there is no formal carbon market for seaweed cultivation yet, industrial players such as Canopy Blue, The Seaweed Company and Running Tide are already selling carbon offsets to corporations on the voluntary market. Running Tide, for example, has sold credits to high-profile buyers such as Microsoft, Chan Zuckerberg Initiative, Stripe and Shopify, and other initiatives are in the pipeline.

Looking at the big picture, sinking seaweed is another false solution promoted by large polluters to supposedly remove carbon from the atmosphere. Other damaging marine geoengineering proposals include reviving ocean fertilization techniques; spreading synthetic reflective beads over Arctic areas; brightening marine clouds; and sinking huge amounts of minerals to change ocean chemistry.

These geoengineering technologies are so risky that they are already under a global moratorium in the UN Convention on Biodiversity and under the London Convention on Ocean Dumping. A large group of civil society organisations are also calling for stronger moratoria on geoengineering, and are advocating that these speculative new technologies must not be allowed to distract from UN climate negotiations focusing on the real measures needed: cutting greenhouse gas emissions.

It is critical that the global community uses every opportunity, including the forthcoming UN Ocean and Climate Change Dialogue, to foster the real solutions to climate change that we urgently need, prohibiting false and unproven “get rich quick” schemes, including “blue carbon” credits.

To find out more:

You can also contact us in Bonn:

Silvia Ribeiro, Latin America Director, silvia [at] etcgroup.org

Neth Daño, Asia Director, neth [at] etcgroup.org

Artwork: Isabelle Morgan, https://isabellemorganillustration.weebly.com

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