Restoring Kelp Forests: 15,575 Hours Of Smashing 5.8 Million Sea Urchins By Hand Over 13 Years To Protect 81 Acres

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ed by the Bay Foundation, divers in the Santa Monica Bay have spent 15,575 hours underwater over the past 13 years. To bring the kelp back, they focus on minimizing the impact of one voracious eater: the purple urchin. The effort has been successful, smashing 5.8 million purple urchins and clearing 80.7 acres (32.7 hectares, the size of 61 football fields), and allowing the kelp to return. But with the results contained far offshore and underwater, has anyone noticed? Ford wonders the same thing. “We call it the forgotten forest,” he says.

The fast-growing kelp ecosystems are known as the “sequoias of the sea” for good reason: they store large amounts of carbon, create habitat for more than 800 marine species and blunt the powerful force of storm waves. Technically, they are a macro-algae, and can grow as much as 2ft each day, reaching 100ft from reef bed to surface. For those lucky enough to see the kelp from under the waves, it can feel like a fairytale – a forest, but instead of walking through it, you’re flying underwater. Ford still remembers the first time he dived into the forest as a scuba diver. The sunlight looked like tongues of flame rippling through the blades from underwater, and the shafts of light peeked through the small holes in the canopy. “It looked like a cathedral, with light shooting through the stained glass,” he says. “And sometimes you float down through this and there’s thousands of fish of all sorts of colors just flitting around everywhere. It’s like flying through an unimaginably dense forest of life.”

But for a time, these glorious environments were at risk of disappearing. When the Bay Foundation started working in these waters in 2012, the sea bed looked like carpets of purple – blanketed in endemic golf ball-sized spiky urchins. It was a symptom of an ecosystem gone haywire, with multiple overlapping injuries: sea otters, which eat urchins as a staple of their diet, were almost wiped out by hunters in the 19th century. Then, from the 1940s to the 1970s, a large amount of DDT was discharged from a chemical plant into the sea off Palos Verdes. Sediment from landslides also buried the reefs in silt, preventing anything from growing. More recently, the local sea stars, which eat the urchins, were hit with a wasting disease, and turned to goo. All that was left was urchins, which eat kelp at an incredible rate, and scratched the reef bed so much that any kelp spores still circulating couldn’t grab a foothold.

Ford and the Bay Foundation did multiple tests to determine the optimal amount of urchins per square meter: two. Meanwhile, some areas of the barrens had 70-80 urchins per meter. Since they didn’t have much to eat, they were basically empty zombie urchins – hungry, empty of their meat, just hanging on and preventing kelp from growing. There was a lot to do. The Bay Foundation applied for grants from the state and federal authorities and started hiring divers, gathering 75 volunteers, and even working with commercial fishers to help out. Ford points out that the team was not smashing the healthy urchins that people depend on for their livelihood. “We were paying the fishermen to put back the forest, and then they could then go back in and fish from there again,” he says.

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https://www.theguardian.com/us-news/2025/aug/31/california-pacific-kelp-forest

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1. oh man....so much uni!