An area of kelp (right) that used to be covered in sea urchins (left) – credit, The Bay Foudnation, provided to the Guardian
GNN has reported before that conservation works, almost wherever, and with whatever method it’s undertaken—though to be honest, hammers aren’t usually involved.
They are, however, very much the tool of choice for the Bay Foundation, an extraordinary, dedicated outfit that has brought about the resurrection of the Santa Monica area’s kelp forests, an ecosystem described as an underwater cathedral or a grove of underwater sequoias.
They were decimated by the endemic purple spiny sea urchin, and for the last 13 years, an all-volunteer squad of divers have spent thousands of hours below the waves smashing them.
Smashing, smashing, and smashing.
Then smashing some more.
Mass extermination of non-invasive species surely is one of the strangest conservation methods you’ll read about, but the explanation is an understandable one.
Since the early 1900s, kelp-devouring spiny sea urchins have gradually been freed from the pressures of predation. Sea otters, who also love smashing a sea urchin or two, were overhunted for their furs. Recently, populations of sea stars have collapsed due to a wasting disease.
Thusly liberated, the sea urchins grew into horde-like populations that would wipe out kelp forests in a matter of days. Their spines scrape up the seabed and prevent any kelp spores—single-cell reproductive organelles that anchor themselves in the seabed—from taking hold and regrowing the forest.
The undersea barrens where the kelp used to grow has been described by the Guardian as covered in “zombie urchins” sometimes 70-80 individuals per square meter of seabed, which linger “hungry, empty of their meat, just hanging on and preventing kelp from growing.”
The Bay Foundation’s divers began routinely going down for astonishing shifts of up to 9 hours. Armed with hammers, they smash the zombie urchins one by one, leaving the larger, healthier urchins that provide a tidy profit to local fishermen, intact.
“You just tap, tap, and sometimes you have to reach into crevices to get the urchins out,” says Sean Taylor, a volunteer diver with the foundation. “Your forearms get super tired.”
Divers told the Guardian that the work is indeed tiring: manual labor underwater, in a wet suit and scuba gear. 15,575 hours were logged in smashing urchins—a mind-boggling 5.8 million of which have been smashed; clearing 61 football fields worth of seabed.
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“Within three months, the kelp came back,” Mitch Johnson, another volunteer with the foundation said. “I’ve never seen a kelp forest that dense—and it was insane to see how quickly it returned.”
Kelp can grow almost as fast as the urchins can eat it—sometimes 2 feet per day. It can grow 100 feet high, providing a vital ecosystem service of dampening the impact of storm surges.
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When fully grown, Johnson and Taylor describe swimming through kelp like flying through an unbelievably dense jungle of life, but with the canopy of a cathedral, with sunlight passing through the diaphanous kelp with a brazen hue like light through stained glass windows.
Hundreds of species inhabit the kelp forest preferentially, and the foundation is now seeing many return, like the California spiny lobster, now that the forests have regrown.
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