The decline of California’s kelp forests since the marine heat wave of 2013-17 has seen only minor recovery despite heroic efforts at restoration carried out by scientists, fishermen, coastal tribes, volunteer divers and conservationists. Nor is the threat to kelp localized. Rather the loss, like the expansion of mega-wildfires on land from Los Angeles to Siberia and from Canada to Australia comes in response to an ever-warming world where 90% of the human-generated heat from the burning of fossil fuels is absorbed by the ocean.

Kelp forests cover some 2.8 million square miles, more area than the Amazon rain forest, and generate some $500 billion a year in value. This includes edible marine species (including many species of kelp itself), thickeners and emulsifiers used in ice cream and cosmetics, and powerful storm and coastal erosion protection, according to a 2023 report in Nature Communications. Photosynthesizing kelp, a form of algae, also generates more oxygen (and sequesters more carbon dioxide) than does the Amazon basin. Along with coral reefs they constitute one of the most complex and productive — if little-known — ecosystems on the planet.

Kelp forests are a challenging cold-water realm, but for those of us who dive into these marine forests in places like Monterey in Northern California or Catalina off L.A., they are an entrancing cathedral of light and life. Here you’ll find orange garibaldi (like goldfish on steroids), wolf eels, leopard sharks, curious harbor seals and multicolored marine snails known as nudibranch. They are vibrant, entangling and light-shifting habitats of wonder and warning in our rapidly changing seas.

Historically, overfishing, loss of predators like sea otters, pollution and overharvesting have posed the main threat to kelp forests. Today, it’s marine heat waves. A 2026 study carried out by scientists from the National Oceanic and Atmospheric Administration and 30 other institutions around the world reports the ocean absorbed more heat in 2025 than ever before. This in turn has set off a record number of marine heat waves that can increase regional water temperatures 5-10 degrees, enough to radically alter ocean conditions.

Because of this warming, these large macroalgae are facing the biggest threat to their existence since they evolved more than 32 million years ago. If they disappear, what happens to the salmon, cod, abalone, whales and more than 1,000 other creatures dependent on kelp forests? What happens to us? Neither science nor society has figured that one out.

A number of coastal communities have been hammered by the loss, such as Fort Bragg, California, which has lost 95% of its kelp forest. The closure of recreational abalone diving alone (abalone feeds on kelp or starves to death in its absence) is estimated to have cost the area $25 million a year. Tasmania, Australia, Norway, Mexico and southern Maine have seen similar kelp loss of 80% or more.

The hopeful news is that kelp is one of the most resilient and fastest-growing organisms on earth — the bamboo of the sea — capable of growing up to 2 feet a day, even as it faces rapid decline. I’ve swum through a kelp forest in a site that 10 years earlier was a moonscape-like sea urchin barren. One California cove full of kelp was wiped out by a landslide but fully recovered within two years.

I’ve gone out with the nonprofit Bay Foundation off Southern California, where divers culled overgrown populations of urchins off Palos Verdes till there were fewer than two urchins per square meter. The organization was then able to see 80 acres of healthy giant kelp forest restored largely through natural spore dispersion. I’ve also gone diving with volunteers in Northern California where similar efforts are producing modest recovery in several rugged coves.

In the Azores, Chile and Argentina, citizen action has led to the creation of large marine parks that protect wild kelp, while in South Korea, whose fisheries agency invests $29 million a year in restoring wild kelp for food security, restoration efforts have brought back 50,000 acres of marine forest to date.

And yet, short of a rapid transition off fossil fuels, which is not happening at this time, you really can’t talk about hope for the future of kelp but instead may have to focus on triage, saving what’s left, with the understanding that kelp forests, although resilient, are now in need of active human intervention.

This could include investing in essential research, as proposed “Help Our Kelp” legislation in Congress has sought to do. Other interventions could include restoring damaged habitat to ensure that these wondrous underwater forests continue to exist, expand where possible and perhaps someday thrive again, to the benefit of coastal communities both human and wild across the temperate seas of our still-awesome blue-marble planet.

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David Helvarg is the executive director of Blue Frontier, an ocean policy group, and co-host of “Rising Tide: The Ocean Podcast.” He is the author of the forthcoming “Forest of the Sea: The Remarkable Life and Imperiled Future of Kelp.”

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