Could sea otters save kelp forests off Northern California coast?

A sea otter floats in Kachemak Bay, Alaska, in this July 1, 2003 file photo. (Laura Rauch, File/AP Photo)

SAUSALITO, California — The health of the ocean off the Northern California coast is in trouble, as biologists have seen a massive die-off of the kelp forests that are essential to a healthy ecosystem. Scientists think bringing back sea otters may be one solution.

Sea otters may be adorable to look at and fun to watch, but what and how much they eat has put them at the centre of a debate.

Last summer, the U.S. Fish and Wildlife Service began floating the idea of reintroducing sea otters to Northern California and Oregon. The agency is now holding public open houses, including one that took place Wednesday morning in Sausalito.

The problem is the kelp forests that have been dying off, thanks to an explosion of sea urchins. That's happening because sea stars, the urchin's primary natural predators, are being killed by rising water temperatures.

But the urchins' only other natural predator—sea otters—were hunted nearly to extinction in the 1800s for their fur. The idea is to bring them back to try to save the kelp.

"They eat a lot of sea urchins," said Southern Sea Otter Recovery Coordinator Lillian Carswell. "And by eating a lot of sea urchins, they help to defend the kelp from overgrazing. And when the kelp is protected, it tends to expand and create resilient kelp beds. Kelp beds support a really huge diversity of species in the marine environment."

In many places the ocean floor looks desolate, carpeted with nearly-dead urchins and not much else. They call them "urchin barrens."

"Basically, it's an underwater desert in which the kelp has been wiped out," said Leah Schrodt with the U.S. Fish and Wildlife Service.

In a 2013 study, otters were reintroduced in British Columbia and, within one year, most of the urchins were gone and kelp was beginning to regrow.

Doug Jung, a Santa Rosa resident and avid abalone diver, thinks that's disingenuous. He said while scientists are waiting for the forest to regrow, the otters will be wiping out all existing shellfish.

"They're cute. We all love them," said Jung. "But we don't want them to strip mine—and let me repeat the term 'strip mine'—the rest of the coast."

Jung said abalone are already in short supply and would be sitting ducks for the otters.

"They're out in the open where, if sea otters come up, they will wipe them out immediately. Then you will have no biological diversity and no abalone," Jung said.

Scientists think the likely place to start would be somewhere along the Oregon coast. But reintroducing otters can be tricky. In the 1960s and 70s, wildlife officials tried to relocate them to the Pacific Northwest, but 90 per cent of the otters either left the area or died.