This is what it looks like to cross the tipping point. Over 95% of the kelp forest along the Northern California coast has disappeared in a matter of a few years. If you’ve ever walked the beaches and seen the kelp washed up on the shore; if you’ve ever kayaked over the top of the canopy; if you ever dived down into that dark forest teeming with fish, colorful starfish, and abalone; you are lucky because that world is almost all gone.
A Unique Environment
The beaches in Northern California, as uninformed tourists quickly learn, are rugged and very cold. The North Pacific Subtropical Gyre (clockwise ocean current) results in coastal upwelling of nutrients from the deep waters off the continental shelf. The abundant nutrients feed a wide variety of life in the cool water, including the dense forest of kelp. Often over 100 feet tall, they regulate coastal currents, which limits erosion and creates a protected environment for fish. The rapidly growing kelp forest absorbs an estimated 20 times more carbon dioxide per acre than forests on land. Bull Kelp — unlike the smaller Giant Kelp found further south — grow and die annually and are therefore constantly at risk.
Kelp grow each spring, as quickly as 10 inches a day. Abalone feed on their fronds. Urchins and sea stars wander the seafloor, protected from storm currents by the kelp which attach to the rocky floor. Kelp absorb carbon dioxide and give off oxygen through photosynthesis. Fish and land mammals also thrive in the nutrient- and oxygen-rich habitat.
Native Americans lived along the coast for thousands of years, fishing, diving for abalone, and hunting otter. Their culture respected nature and sustained that balance.
Between Russians venturing down from the north and Spaniards venturing up from the south, the otter population was decimated by the early 1800s.
Otters were the primary predators of purple urchin, which are the primary predators of bull kelp.
Sunflower sea stars are also predators of purple urchin and they alone maintained the balance once the sea otters were gone. The balance has been tested for centuries, but the kelp have always proved resilient. Until now.
The Tipping Point
Scientists at the UC Davis — Bodega Marine Lab, in 2016, described a “Perfect Storm” of environmental factors leading to the kelp forest collapse. I’ve updated it.
- 2011: A toxic algal bloom centered off Fort Ross killed large numbers of abalone and other invertebrates.
- 2013: Sea Star Wasting Syndrome was first observed, causing mass mortality among the huge sunflower sea star. About 5.75 billion are estimated to have died, placing them on the critically endangered species list.
- 2014: A marine heat wave known as “the Blob’’ occurred in the Pacific Ocean, disturbing the nutrient upwelling, weakening the kelp. Without sunflower sea stars, purple urchin populations grew unchecked, feeding on the weakened bull kelp.
- 2015–2016: A 2-year El Niño event compounded the warm ocean conditions.
- 2018: Without a new crop of bull kelp for several seasons, red abalone populations fell dramatically. The state Fish and Game Commission closed the $44 million abalone fishery and just extended the closure until at least 2026.
- 2021: A report from UC Santa Cruz confirms more than 95% of the bull kelp have vanished off the coasts of Sonoma and Mendocino counties since 2013.
Divers from Reef Check California’s volunteer program have observed fish and plant species much further north of their traditional habitats. Such sightings indicate the whole California coast is undergoing “Tropicalization.” This term describes a shift of the distributions of species away from the equator as ocean temperatures rise due to climate change.
Without the canopy of kelp absorbing the sunshine and maintaining cool temperatures below, this coastal process of tropicalization will accelerate.
Many different efforts are underway, attempting to revive the sunflower sea stars and reintroduce more resilient bull kelp. “In a warming world, it’s not just about restoring the status quo but about managing kelp forests for resilience,” said ecologist Tristin McHugh, kelp project director with The Nature Conservancy.
In addition to suspending abalone fishing, the State removed the limits for recreational divers to take purple urchins in Caspar Cove, on the Mendocino Coast, and on Tanker Reef in Monterey Bay. Unfortunately, there is no viable market for purple urchins so divers are doing this simply to restore balance in hopes of reviving the kelp.
In a State-sponsored experiment (conducted by Reef Check in support of earlier work done by the Watermen’s Alliance and Noyo Marine Center), commercial divers in Fort Bragg’s Noyo Harbor removed 13 tons of purple urchins to clear a 10-acre area to a minimum density of urchins.
But you and I can help, too! Join Reef Check California and become a Citizen Scientist.
“Reef Check California volunteer citizen scientists are divers, fishermen, kayakers, surfers, boaters, and a wide range of Californians who take a proactive role in making sure that our nearshore ecosystems are healthy and well managed. We train scuba divers to be citizen scientists familiar with California’s marine life and how to survey kelp forests. We provide them with the skills to conduct scientific surveys and then lead them in monitoring kelp forests along the entire coast of California.”
Technically, your scuba diving certification doesn’t expire. So if you’re a diver, we need your help!
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