- Kelp forests support a kaleidoscope of biodiversity and perform crucial ecosystem functions, yet they are in trouble globally.
- A recent journal commentary shows that just 15.9% of kelp forests are in protected areas, and only 1.6% of them are in areas with the highest levels of protection.
- The authors said they hope their findings will motivate policymakers to include kelp forests in international conservation targets, such as the “30×30” mandate to protect 30% of Earth’s land and sea by 2030.
Using only fins, divers wild-harvest abalone off eastern Australia’s coast. The marine snail, known for its beautiful iridescent shell but sought for its meat, is a fishery worth more than 150 million Australian dollars ($93 million) annually. But the divers’ craft is changing as the coast’s kelp forest — an abalone home — has succumbed to urchins. Droves of the spiky creatures munch down the forest, leaving so-called urchin barrens in their wake.
Shocked, the abalone divers started a kelp forest restoration cooperative in 2011, one of the first ever. But despite some successes, including restoring 42 hectares (105 acres), the forest continues to dwindle.
Their story is part of a global trend, with kelp forests declining along most of the high-latitude, cool-water coastlines they inhabit. Toward helping stem this decline, a recent journal commentary catalogued how many kelp forests are in conservation zones and the degree of those protections, finding that less than one-fifth are protected at all. It also detailed the causes of kelp decline, including predation by urchins, and cataloged global restoration projects.
“[K]elp forests are often forgotten” in the global conservation conversation, Aaron Eger, program director at Kelp Forest Alliance, a research-focused network of more than 200 conservationists, kelp lovers and seaweed professionals headquartered in Sydney, Australia, and the lead author of the commentary, told Mongabay. “This is the first global assessment of where kelp forests are, where they’re threatened, how much of that has been restored, where it’s been lost and how much of that is actively protected and managed to try to safeguard those habitats and prevent them from further decline.”
Eger said in writing the commentary, published in November in the journal One Earth, he and his co-authors hoped to make it easier for kelp forest conservation to be included in global treaties like the Kunming-Montreal Global Biodiversity Framework, which includes the “30×30” mandate to protect 30% of Earth’s land and sea by 2030.
Including kelp in conservation conversations
Stretching as high as 53 meters (174 feet) in the ocean, underwater kelp forests fringe a third of the world’s coastlines, providing foundational habitat and food for species as large as the humpback whale (Megaptera novaeangliae) and as small as the abalone (genus Haliotis). They are important for terrestrial life too: Marine scientists consider kelp forests crucial to shoring up the ocean’s defense against climate change, buffering increasing acidity and providing natural barriers to storm surge. In 2023, The Nature Conservancy estimated they provide more than $500 billion in ecosystem services annually.
Globally, kelp forests are declining at a rate of 1.8% annually, according to 2016 research, and an estimated 40-60% of them are degraded, according to the U.N. Environment Programme’s 2023 report on kelp forests. Threats include climate change and its symptoms, like increasing ocean acidification, marine heat waves and freshwater infusions from glacial runoff, along with pollution, disease, invasive species, overfishing, cold spells, kelp harvest and coastal development, according to the new commentary.
In some places, the effects are devastating.
“I live in a region where 96% of kelp forests have been lost,” Tristin Anoush McHugh, kelp project director at The Nature Conservancy’s California Oceans Program and a co-author of the new study, told Mongabay. Concentrating on removing urchins, McHugh works to stabilize the last 4% of forest remaining along a 350-kilometer (217-mile) stretch of coastline in northern California. “If that was happening on land, we would be completely all hands on deck,” she said.
The challenge of measuring a (mostly) invisible biome
To map ecosystems like forests or coral, scientists can use drone or satellite imagery. But that’s not possible for kelp. Of the more than 100 species of kelp, only three are visible from above: bull kelp (Nereocystis luetkeana), giant kelp (Macrocystis pyrifera) and bamboo kelp (Ecklonia maxima).
To determine how much kelp was protected, the scientists took an existing kelp forest biome distribution map and remapped the distributions in higher resolution and with greater accuracy. Then they overlaid marine protected areas (MPAs) onto this more accurate map.
From this, they estimated that 15.9% of kelp forests globally are in protected areas. However, only 1.6% of the forests are in areas with the highest levels of protection, suggesting that some MPAs may not effectively protect kelp forests from threats.
Eger said he and his co-authors hope their map and findings can offer a baseline for kelp conservation moving forward, and that kelp forests will be included in the 30×30 framework. Unlike mangroves, coral or terrestrial forests, kelp is not included in international biodiversity targets.
“The study of Eger and colleagues sounds [a] strong alarm over conservation of biodiverse kelps forests that are fundamentally cold-water species and are rapidly lost due to ocean warming,” said Sergey Nuzhdin, a kelp researcher at University of Southern California, in an email to Mongabay.
Sharing kelp help
Additionally, the authors conducted more than 200 interviews to track every kelp conservation initiative globally. They found more than 238 projects focused on kelp forest restoration, with approximately 19,000 hectares (47,000 acres) in restoration. These efforts have been led by Japan and South Korea for the past few decades.
Kelp restorationists take different approaches depending on the factor or factors driving decline. For example, when predation by urchins is the most acute problem, oftentimes it’s due to the loss of apex predators, such as sea otters or sea stars, combined with the kelp forest being weakened by marine heat waves or increased ocean acidification. Restoration efforts would focus on getting rid of urchins as well as planting new forest. Nuzhdin, who also works at Kelp Ark, a seed bank in California that was established in the 1980s, said seed banks are crucial to restoration efforts, as they could one day provide diverse genetic material for reseeding forests.
The world’s leader in kelp restoration is South Korea, Eger said. The country has 29,000 hectares (71,660 acres) of kelp forest under restoration, with a 50% success rate, and a goal of regreening 75% of its coastline. The project combines community marine gardening days with a roving paid kelp-planting workforce.
Marine scientists don’t want to be “reinventing the wheel every time a kelp forest is lost,” McHugh said, so connecting scientists across the world facing the same kelp forest declines was a main impetus behind the One Earth commentary.
As its members learned about the lack of kelp forest protection, the Kelp Forest Alliance launched the Kelp Forest Challenge , a global call to action to restore 200,000 hectares (494,000 acres) and protect 1 million hectares (2.5 million acres) by 2030, with higher goals for 2040. To date, it has received 55,000 hectares (about 136,000 acres) of pledges to restore these marine forests and 7,000 hectares (17,300 acres) of pledges to protect them.
Initiatives in “kelpie” countries like Canada, Chile, Australia, the United Kingdom and Norway would be the most impactful, Eger said.
“Major cultural economic centers like London or Los Angeles or New York or Vancouver or Sydney have a marine forest right in their blue backyard,” he said, offering hope that proximity will lead to conservation. “International policymakers … can see the relevancy and the potential to do for kelp forests what has been done for a lot of other ecosystems.”
Banner image: Bull kelp (Nereocystis luetkeana) in California. Image courtesy of Tristin Anoush McHugh.
Kelp forests contribute $500 billion to global economy, study shows
Citations:
Eger, A. M., Eddy, N., McHugh, T. A., Arafeh-Dalmau, N., Wernberg, T., Krumhansl, K., … Vergés, A. (2024). State of the world’s kelp forests. One Earth. Retrieved from https://www.cell.com/one-earth/abstract/S2590-3322(24)00532-3
Krumhansl, K. A., Okamoto, D. K., Rassweiler, A., & K. Byrnes, J. E. (2016). Global patterns of kelp forest change over the past half-century. PNAS. doi:10.1073/pnas.160610211
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