Hope for kelp recovery in California as underwater forest returns to Monterey Bay

Ever since California’s coastal kelp forests began to disappear in mid-2010, decimated by a heat wave and voracious native sea urchins, people have been trying to fix the problem.

Now one project is showing signs of success.

At a site called Tanker Reef in Monterey, right near the tourist shops and restaurants of Old Fisherman’s Wharf, the kelp forest has rebounded after volunteer divers removed over half a million sea urchins since spring 2021. The underwater zone slowly transformed from the so-called urchin bare, an area where the spiky purple creatures eat the remaining algae, back to a leafy forest full of life.

It’s “really just a night and day difference. Like if you dived down there in 2021, it was nothing but rocks and urchins, really just no life and no diversity,” said Dan Abbott, director of the kelp forest program at the nonprofit Reef Check, a partner in the mostly volunteer project. who said it is the most successful so far in California. “Now you go there and it looks completely different.

Data collected at the site indicate that the density of the kelp, measured by the number of individual plants called petioles that cling to the ocean floor with multiple vanes, increased from almost zero to 1.5 per square meter as the voracious predators dropped from 8 to 1. square meter on a plot of 2.5 acres.

“It’s very encouraging to see such positive results,” Abbott said, referring to the first year of data in the three-year project.

The nonprofit group Giant Giant Kelp Restoration organized volunteers who completed 1,070 dives and spent 800 hours dislodging sea urchins, working with state and federal agencies on the experimental project.

“When I first surveyed there, you could count the fish on two hands,” said Keith Rootsaert, founder of Giant Giant Kelp Restoration. Then we “started to see all the little fish coming closer and then we saw the bigger fish coming to eat the little fish.”

Rootsaert, who has a day job as a building systems engineer, has personally participated in about 200 dives. There are 150 volunteers in the group, all trained by local dive shops.

The kelp forests that once covered hundreds of miles of coastline provided vital habitat for young fish, crabs and other creatures, as well as the marine mammals and seabirds that eat them. In Sonoma and Mendocino counties, the size of the kelp forest decreased by 95% between 2014 and 2019, according to a UC Santa Cruz analysis. The Monterey Peninsula has not been extensively studied, but Abbott estimates that its kelp forest has shrunk by about two-thirds over a similar period.


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