Op-Ed: Warmer Oceans Threaten Another California Forest, This One Underwater

RICHMOND, Calif. — The bull kelp forests off Northern California are sometimes spoken of as the redwoods of the sea. And like the redwoods, these forests are in danger. In less than a decade, these otherworldly undersea landscapes, lush with life, have all but disappeared along 200 miles of coast north of San Francisco’s Golden Gate Bridge.

The warming climate has set in motion this disaster and it is unclear whether it can be reversed as greenhouse gas emissions continue to flood the atmosphere. Energy-related carbon dioxide emissions rose by 6 percent globally in 2021, the biggest increase ever, as the world began bouncing back from pandemic. These kelp forests are yet another ocean casualty of fossil-fueled climate disruption, along with habitats ruined by coral bleaching, rising sea levels, warming ocean waters and the pronounced loss of Arctic sea ice.

I have often visited the kelp forests as a recreational diver. Translucent green-brown stalks rise from the ocean floor to the surface, their fronds swaying in the current. Beams of sunlight shoot through the kelp canopy, turning it into cathedral windows illuminating strawberry anemones, abalone, wolf eels and rockfish. Harbor seals swim close for a look before twisting away into the forest. An indifferent leopard shark may glide by. You might become suddenly distracted as a cormorant dives down from the sky in search of a meal.

From its floating canopies to its “holdfast” roots, kelp supports coastal biodiversity and sequesters more carbon than redwood groves, while also protecting the coastline from the full force of storms. California’s thousands of acres of giant and bull kelp forest shelter fin fish, shellfish, seals and sharks, more than 1,000 animal and plant species in all, making it one of the most productive ecosystems on earth.

But their future does not look good. Using satellite imagery, scientists estimate that 95 percent of these bull kelp forests have vanished in less than a decade. The collapse of these kelp forests — despite a few local rebounds in 2020 and 2021 — has hurt the small coastal communities that rely on fishing and tourism dollars and Indigenous traditions of kelp and seaweed harvesting.

In 2014, an ocean heat wave that scientists called “the blob” caused water temperatures to spike along the West Coast, weakening and killing the kelp, which thrives in cold, nutrient-rich currents. Then a disease supercharged by the warmer waters, according to a study published in 2019, devastated sea stars and allowed their prey, purple urchins, to proliferate. These voracious eaters took out almost all the surviving kelp.

The disease, known as sea star wasting syndrome, melts the bodies of what we used to call starfish, including the many-armed sunflower sea star. This sea star had become the principal urchin predator, replacing sea otters, whose numbers plummeted over the last two centuries, victims of the fur trade and the depletion of their habitat. Unfortunately, today’s other top urchin predator, commercial fishermen, target only larger, meatier species of urchin.

Since 2013 the small purple urchins have run amok, replacing the complex near-shore kelp forest habitat with “urchin barrens” — a seabed carpeted with pastel-colored pincushion-like urchins.

To combat the devastation, divers — initially volunteers and now some paid by the state of California — have used suction tubes or hammers to destroy the urchins by the tens of thousands and have also begun planting new kelp. Newer strategies include collecting and fattening up urchins in tanks for the restaurant and sushi market.

But there’s no indication any of this is seriously helping. Hungry urchins — which can survive for decades in a “zombie” state of near starvation — can revive enough to take out the restored kelp.

Still, collaborative efforts continue among fishermen, scientists, academics and conservationists with help from California’s Department of Fish and Wildlife and other state agencies. At the federal level, Jared Huffman, the chairman of the House Natural Resources Subcommittee on Water, Oceans and Wildlife, is deeply concerned about the loss of the kelp in his district, which includes five Northern California coastal counties.

“We have to regard this as a wake-up call that conditions like this can hit us suddenly and take away entire ecosystems,” he said. Last year, he introduced the Keeping Ecosystems Living and Productive Act to provide federal research and recovery grants through the National Oceanic and Atmospheric Administration. In February, the Natural Resources Committee voted to pass the bill on to the full House for a final vote.

All of these efforts are heartening. The bottom line, however, may be more of a downward spiral. Brian Tissot, the recently retired longtime director of Humboldt State Polytechnic University’s marine lab in far Northern California, has warned that nothing may change until the ocean returns to a cooler, nutrient-rich condition, which still periodically occurs. In the long term, though, ocean heat waves will become more frequent as the planet continues to warm. At the same time the kelp has been disappearing, Humboldt County, normally a temperate rainforest, has been experiencing its own devastating wildfires.

“All these things are related to climate change,” Dr. Tissot told me, “and they’re coming together in ways we never thought about, making it very difficult to know what to do other than address climate change.”

Bull kelp is among the fastest-growing plants in the world, expanding up to 10 inches a day and stretching 100 feet and more from the ocean bottom to the surface of the sea. But even it can’t outpace our failure to slow the warming of our planet.