How to Revive California’s Underwater Forests? Smash a Spiky, Hungry Foe.

Cove by cove, scientists, divers and volunteers are hauling up urchins to protect kelp.

by Raymond Zhong

From the bluffs, you might have mistaken the little brown heads poking out of the ocean this month for seals, hundreds of them, gathered for a morning conclave. In fact, they were something almost as surprising: bulb upon glistening bulb of kelp, more of it than this cove in Northern California had seen in years.

Beneath the milky water, the kelp’s ropelike stems stood in thickets dense enough to snag the valve on a scuba tank. The parade of long, luxuriant blades, streaming out of each bulb like wavy tresses, made diving these waters feel a bit like touring a hairdressers’ convention.

A decade ago, the coastline north of San Francisco was the site of one of the most horrific deforestations ever recorded. More than 90 percent of the towering, majestic kelp forests, across 200 miles of glittering shore, were dead and gone in years. Felled by freakishly warm ocean water.