The continued impact from climate change, pollution, overfishing, and an increase in invasive, non-native species could all result in “dramatic changes” to the distribution and diversity of seaweed species and their habitats with profound reverberations across both ocean and human health, a new study co-authored by the Natural History Museum has warned.

All outlined in a new report titled The State of the World’s Seaweeds, researchers behind the international seaweed research programme have combined the most up-to-date scientific evidence of the increasing threats being faced by global seaweed habitats.

Crucially, it emphasises that despite the importance of seaweeds and the severity of the threats they face, they are currently afforded “inadequate conservation measures”. 

Authors of the study have now called for these major gaps to be addressed.

The programme behind the report is GlobalSeaweed-SUPERSTAR – a project funded by the UK’s Global Centre on Biodiversity for Climate and being led by the Scottish Association for Marine Science in Oban.

“Seaweeds are often the unsung heroes of the marine world,” said Dr Sophie Corrigan, lead author on the report and a researcher with the Natural History Museum in London. “They form some of the largest marine habitats we have and underpin so many marine resources, as well as playing an important role in the function of other marine habitats such as cementing coral reefs together and protecting them from wave damage.

“Food, medicines, and even the cosmetics industry rely on seaweed for the properties they can offer.”

In the report, it is explained that while global interest in kelp is “rightfully” building, other seaweeds are being left behind. 

“This is something we want to change, and we’re hoping that all seaweeds will benefit from the Global Biodiversity Framework’s 30by30 initiative as more protected areas are created or expanded in the coming years,” continued Dr Sophie.

 Seaweeds are red, green, and brown macroalgae with certain species of reds traced back to more than 1.6 billion years ago. Collectively, the world’s population of seaweed spread could cover an area the size of Australia, making them the largest of the planet’s vegetated marine habitats, depended upon by many other species of marine life.

“Safeguarding the future of seaweeds and realising the full potential of seaweeds and their uses will require a global movement to unite governments, researchers, industries, charities, Indigenous Peoples, and local communities into protecting seaweeds. This report is an important step in that process,” said Dr Sophie.

Seaweeds play a significant role in absorbing carbon dioxide, doing so at a far greater rate than many plants on land do and can help to absorb pollution from the ocean, too. 

There are also millions of seaweed farmers in 56 countries worldwide who rely on seaweed for their livelihoods. The vast majority of these farmers are in Asia, which accounts for more than 95% of global seaweed farming.

Last month, the same team behind the report launched a major research project to help tackle the environmental challenges faced by seaweed communities and industries across south-east Asia. It’s here that over one million livelihoods are supported by the seaweed industry, making it the largest producer of red seaweed.

However, its seaweed industry is threatened by a lack of genetic diversity in the cultivators, increasing its vulnerability to pests and diseases. It’s just one of the many issues that seaweed populations currently face the world over.  

And while these seaweeds face an uncertain future and growing pressures from human-induced impact including climate change, pollution, and overfishing, the necessary data to determine the rate at which seaweed habitats are currently being lost does not exist. It’s predicted that the majority of seaweeds will experience a high degree of local extinction and poleward expansions by the end of the century, with overall global declines in coverage and diversity.

Professor Juliet Brodie of the Natural History Museum in London, alongside GlobalSeaweed-SUPERSTAR programme leader, Professor Elizabeth Cottier-Cook of the Scottish Association for Marine Science, and Professor Lim Phaik Eem from the University of Malaya are co-authors on the State of the World’s Seaweeds report.

Professor Juliet said: “A world without seaweeds means devastation to the functioning and food security of Earth as we know it. A world with seaweeds that are healthy and thriving offers hope of a better future for the planet.”

The report – The State of the World’s Seaweeds – will form the evidence base for the Seaweed Breakthrough initiative, a set of conservation targets for all seaweed stakeholders to commit to – including policy makers, governments, farmers, and local communities – that will be launched at the UN Oceans Conference in June.

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