The world’s waters are humming with dangerous, unnatural noise
To compare the sounds of technology and whale calls, listen to this online exclusive feature.
Up north in the Pacific Ocean near Washington, the orcas are changing their calls. Twenty degrees south near Baja California, gray whales have drifted from the lagoon that served as their nursery for millennia. On the shores of the Canary Islands off the northwestern coast of Africa, an area teeming with marine life and ferryboats, sperm whales are turning up dead, their jaws smashed and backbones splintered by collisions with ships.
In three distinct areas of two different oceans, these animals are plagued by a raucous cacophony of unnatural noise. The orcas struggle to be heard over the persistent buzz of whale-watching ships. The grays flee not only the briny discharge of the Guerrero Negro salt factory, but also the constant thrumming of its diesel pumps. The sperm whales may have gone deaf to approaching vessels: When French biologist and engineer Michel André examined two that had collided with a cargo ship, he found their sensitive hearing mechanisms severely damaged—perhaps, he hypothesized, from constant exposure to the thwack of propellers.
As the mainstream media have reported, marine biologists know that high-powered military sonar has immediate and lethal consequences for marine life. Whales and dolphins have stranded and died following Navy experiments with mid- and low-frequency sonar all over the globe, spurring hard-fought court battles to limit sonar exercises in sensitive ocean habitat.
What is not widely known is that researchers also worry about constant background noise in the sea: sound that causes little in the way of instant injury, and whose effects are harder to prove, but may have a long-term, chronic impact on marine mammals. “It may be preventing them from doing things that they need to do,” says John Hildebrand, a professor at the Scripps Institution of Oceanography in La Jolla, California, “like detect signals from other animals of their own species and detect signals that would help them find food.”
Male blue whales in the Pacific Ocean, for instance, send out a specific call to find a mate. That call falls roughly in the same frequency as the hum a ship’s propeller makes as it pulls through the water. Underwater, hums carry: “You can hear container ships in the Pacific up by Alaska all the way down in Southern California,” Hildebrand says. As ever-faster vessels loaded with exports crisscross the globe in greater numbers, the ambient drone in the oceans threatens to drown out whales’ voices.
For a male blue whale on the make, “that’s a big problem,” Hildebrand says. “If the girl of your dreams is never going to hear you, you’re never going to breed.”
In 2003 and 2004, Hildebrand, along with Mark McDonald of WhaleAcoustics in Bellvue, Colorado, and Sean Wiggins of Scripps, measured noise levels south of the Santa Barbara Channel, an unusually diverse marine habitat off the Southern California coast. They then compared their data with recently declassified sound records from the same area made by the U.S. military from 1964 to 1966. What they found was an area of the ocean 10 times noisier than it was 40 years ago, rattling with engines, explosions, sonar, and ships.
Throughout the ocean, petroleum outfits use seismic air guns to sound the depths for oil-rich pockets, and fishing operations use acoustic deterrent devices to warn marine mammals away from their nets. But in Southern California’s coastal waters, which flow into two of the nation’s busiest ports, Hildebrand blames ship traffic for most of the noise. “It’s as if I put a freeway next to your house,” he says. “You wouldn’t be happy about it.”
Nature, of course, makes its own racket. Before humans harvested most of the ocean’s inhabitants, whistling dolphins, snapping shrimp, and clicking sperm whales filled the water with sound that, combined with the calving of glaciers and the rushing of tides, produced a ruckus to rival modern industry. Michael Stocker, director of the Lagunitas, California–based advocacy group Ocean Conservation Research, acknowledges that several centuries back, the ocean was even noisier than it is now. “But it was a different kind of noise,” Stocker says. To a whale, the sounds of technology may be like “somebody following you around all day running their fingernails down a blackboard.”
Stocker uses kurtosis, the statistical term for a graph’s spikes and dips, to contrast synthetic sound with the ocean’s natural clamor. Applied to acoustics, “ ‘high kurtosis’ refers to a sound that has a very peaky spectrum,” Stocker says. “It’s grating and obnoxious, and to animals it indicates things that are fast and out of control.” Think the squeal of tires on pavement as you slam on the brakes.
“High kurtosis sounds are rare in nature,” Stocker explains, “and understanding that is going to be the key to managing noise in the ocean.” He envisions a day when everything from military sonar to ships’ propellers could be tweaked to sound more like the singing of humpbacks and less like the screaming of electronics and metal.
While we wait for industry to embrace the principles of biomimicry, Stocker, like Hildebrand, advocates developing stricter acoustic criteria for the places where whales are known to congregate. In the Northern Atlantic, part-time home to a few hundred grievously endangered right whales, the Canadian government requires ships to slow down and steer around whale habitat. Could international laws someday require mariners to quiet their ships as they approach coastal waters where cetaceans feed and raise their young?
Hildebrand thinks it’s possible. “In the same way there are regulations about what ships can discharge, there could be regulations about noise,” he suggests. “They can’t come in discharging oil. Maybe someday in the future they can’t come in discharging sound.”