This is the bittersweet tale of a great forest’s struggle to survive.
Unlike the trees that blanket the High Sierra, this forest is invisible to most of us because it lies beneath the ocean. Swaying to and fro with changing currents, the huge kelp forests that stretch intermittently from below Southern California to the Aleutian Islands have drifted to the edge of extinction several times in recent decades.
Kelp is a dynamic part of the marine life cycle. It produces enormous amounts of oxygen and provides nutrients and an irreplaceable habitat for a range of marine creatures. One species, known as the giant kelp, is one of the fastest-growing plants on Earth, sometimes growing as much as 3 feet in a single day.
Yet it is surprisingly vulnerable.
“The kelp was smashed by pollution during the 1950s” as municipalities along the California coastline pumped raw sewage into the sea, says marine biologist Paul K. Dayton of Scripps Institution of Oceanography. And at the same time, the kelp forest was being nibbled to death by a growing army of sea urchins.
The sea urchins thrived because their predators had been decimated by overfishing, Dayton says. Moving slowly through the forest like a swarm of locusts, sea urchins have been known to strip an entire coastline of kelp.
Adding insult to injury, nature also moved to pull the plug on the kelp forests. Intense storms bashed the coastline, literally ripping kelp out of the thin layer of sediments on the ocean floor and sweeping away the algae that augmented the urchin’s diet, thus forcing them to graze more intensely on the kelp.
So much of the kelp disappeared that scientists feared at the time that it might never come back. But new sewage treatment facilities were built, dramatically reducing pollution levels and, therefore, reversing the kelp forests’ fate.
“It took them awhile to get back,” Dayton says. “But the kelps are quite robust right now.”
A happy ending, right? Wrong.
Dayton, like so many of his colleagues, spends as much time underwater as possible. He has been an ardent diver for 30 years. He has seen the forest survive, but it is not what it once was. It has become, he says, a ghost community.
Missing from the forest, he says, are the large sea animals that help maintain nature’s balance. There was a time many years ago, he adds, when huge schools of sea bass, numbering in the tens of thousands, roamed through the giant kelp, taking more than an hour to pass a single point.
But when he dives now, he says, “I never see even one.”
That story can be repeated for dozens of creatures.
Dayton’s colleague at Scripps, Mia J. Tegner, recalls seeing fields of abalone when she began diving 25 years ago off Southern California. When she dives these days, she says, “often I don’t see any.”
The abalone, savored for its delicate flavor, draws much of its food from the kelp beds.
“These are slow-growing, long-lived animals that are found in highly predictable locations,” she says, making them an easy target for overfishing.
“Abalones are very sedentary organisms. They find a rock they like and sit there and wait for the food to drift to them,” she says.
Since a typical abalone may move no more than 10 meters in its entire lifetime, they must remain in densely packed communities to reproduce.
“When they get spread out over very large distances, which they are now, then spawning is not successful,” she says.
Four of the five species of abalone found on Southern California’s coast have become so decimated that they are now off-limits to fishermen. And Tegner’s research indicates that one species of abalone, H. sorenseni, will become the first marine invertebrate to become biologically extinct as a result of human fishing.
The loss of so many creatures, including large lobsters and sea otters, has left sea urchins devoid of predators, and their numbers have exploded, once again threatening the kelp. But, as we said, this is a bittersweet story, and these voracious grazers now find themselves in demand as a delicacy, particularly in Japan. Aggressive fishing for urchins off California’s shores is restoring an equilibrium that other humans had taken away.
So what’s the worry? A lot, according to Dayton and Tegner and others who are studying a world few of us ever see.
If the plight of the kelp forest tells us anything, Dayton says, it is that we don’t know nearly enough about the crucial region that lies just beyond our sandy beaches.
And when he straps on his diving tank and plunges into the Pacific, Dayton worries about something else.
“I worry about the missing pieces,” the creatures he no longer sees, he says. And he worries that the rest of us are oblivious to overfishing and other human activities that are changing the world beneath the sea.
For most of us, he says, the problem remains out of sight and out of mind. Everything looks OK when we go to the beach, he says. After all, “the waves look fine.”
Lee Dye can be reached via e-mail at email@example.com