Summary of the global wild harvesting and seaweed aquaculture industry. Credit: Applied Phycology (2025). DOI: 10.1080/26388081.2025.2574676

Some of the ocean’s most important habitats aren’t included in protected areas.

Seaweeds capture carbon and provide shelter for marine wildlife, but new research reveals that they often lack direct protections.

Local support could be crucial to securing the future of struggling seaweeds.

Rising temperatures and increasing levels of disease are known to be a major threat to the survival of many crucial ecosystems, including seagrass meadows and coral reefs. But while seaweed habitats are at just as much risk, very little action is being taken to directly protect them.

A recent analysis led by scientists at the Natural History Museum suggests that workers in the seaweed industry could help. Around the world, millions of people are involved in the cultivation and harvesting of seaweed, which could provide a large pool of future conservationists.

Professor Juliet Brodie, one of the co-authors of the paper, says that allowing locals to take responsibility for their area’s habitats would ensure both their continued livelihoods and the protection of important seaweeds.

"Roughly half of the global seaweed industry is located within a kilometer of marine protected areas," Juliet explains. "This means we should collaborate with seaweed farmers on the ground so they can lead on conserving the seaweeds within these areas while protecting their incomes."

"This can be assisted by capacity building and knowledge exchange, together with community science initiatives, to help integrate seaweed conservation into their farming techniques. We’ve started this process already, but we’ll need a lot more capacity to make this dream a reality."

The paper was published in the journal Applied Phycology.

What are seaweeds used for?

Seaweeds are increasingly big business, with the industry expected to be worth around £19 billion by 2028. The fast growth of seaweeds and their limited demand for land and resources has made them a promising crop for a more sustainable future.

The vast majority of seaweed is grown in dedicated farms, with around three quarters used for food. This includes seaweed that’s eaten directly, like the nori used to wrap sushi, as well as algal products like carrageenan that are used as additives.

Seaweed is also used in many other industries, such as biofuels, fertilizers and medicines. However, just 2% of the more than 12,000 known species of seaweed are used by the seaweed industry. As the algae are often grown clonally, this means just a fraction of their overall diversity is being made use of.

This is an issue, as seaweed stocks are under pressure. While the cultivation of seaweeds is partly dictated by demand, production appears to be declining.

"One of the most commercially important groups of seaweeds are the ecuheumatoids, which are used to produce carrageenan," Juliet says. "However, when looking at global statistics, it seems that their production peaked in 2015 and has been on a downward trend since then."

"It’s hard to tell exactly why, but it appears that some major producers have experienced declines of up to 25% and aren’t as productive as they used to be. This could be related to a lack of genetic diversity, which has seen seaweeds become much smaller and more vulnerable to pests."

Trying to understand these changes has been complicated by historic issues in studying seaweeds, with many difficult to identify to the species level.

Securing the future of seaweeds

To improve the genetic health of seaweeds, it will be important to make use of wild populations. Not only could creating new cultivars help to improve the productivity of farmed seaweeds, but it could also transfer genes that could help them tolerate environmental changes.

This is where marine protected areas (MPAs) can come in. Currently, the researchers estimate that around 18% of these areas overlap with the seaweed industry, though the true figure could be higher as not all farms are formally reported.

By ensuring that MPAs are designed to protect specific seaweed habitats, they could provide places that wild cultivars can grow and be drawn on by farmers when needed. Juliet and the rest of her team hope to test how this might work in their future research.

"We’ve got permission to run a study inside a marine protected area to see if seaweed farms can contribute to the restoration of seaweed stocks," Juliet says. "We’ve already had some promising results, as our Malaysian partners have managed to grow wild stocks in nursery farms."

"Some of these cultivars have been able to tolerate pests and the El Niño climate event, which is an exciting prospect for what’s to come."

The findings of this research are feeding into GlobalSeaweed-SUPERSTAR, a conservation project that hopes to protect seaweeds through a series of initiatives with clear and measurable goals. The most prominent is the Seaweed Breakthrough, a strategy to protect the world’s seaweeds and drive their recovery.

The team are currently consulting on the goals of the Seaweed Breakthrough, with the final strategy set to be unveiled at the COP31 climate summit in 2026.

More information: Juliet Brodie et al, Global seaweed stock and Marine Protected Area assessments provide potential opportunities to protect wild seaweeds, Applied Phycology (2025). DOI: 10.1080/26388081.2025.2574676

Citation: Vital seaweed habitats aren’t being protected by ocean reserves (2025, December 4) retrieved 4 December 2025 from https://phys.org/news/2025-12-vital-seaweed-habitats-ocean-reserves.html

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