Scientists say underwater sound is reaching a critical mass, causing damage to ocean life, but fixing the problem isn’t easy.
In 1992, Lindy Weilgart spent a year traipsing around the Pacific, following several groups of sperm whales as they moved between the coasts of Ecuador and the Galapagos Islands. Then a postdoctoral researcher at Cornell University, Weilgart was monitoring whale codas: the short, punctuated clicking-sounds that whales use to communicate. But as she spent more time on the ocean, she noticed how sensitive the whales were to noise. “Even a little splash by a swimmer would freak them out,” she recalls.
Human-caused noise pollution in the world’s oceans is causing problems for marine animals like dolphins, which rely on sound for communication. (Visual by Niklas Morberg/Flickr)
That realization, coupled with an awareness of how much noise humans were adding to the marine ecosystem “completely derailed me,” Weilgart says. Now a researcher at Dalhousie University, Weilgart writes about the effects of sound on marine life, joining a group of researchers who are increasingly concerned about the growing noise pollution in our oceans.
Increased activity and traffic from boats, commercial shipping traffic, military sonar systems, and seismic air guns — used by oil companies to detect natural gas deposits — have all contributed to what scientists call a “cocktail party effect,” an accumulation of sounds that threaten underwater life.
“Twenty years ago, the issue was virtually nonexistent, but since then there’s been a great infusion of science and regulatory concern,” says Michael Jasny, director of the Marine Mammal Protection Project at the Natural Resources Defense Council.
A documentary exploring the trouble with noisy waters debuted on the Discovery Channel last week, coupled with a Whitehouse.gov petition asking for enhanced regulations. As of Monday, the petition — which was created by Discovery, the NRDC, and the International Fund for Animal Welfare — had 10,137 of the 100,000 signatures needed for a response.
In sea water, sound travels around 1,500 meters per second, about four times faster than it does in the air. And it travels farther, explaining why whales can communicate across such large distances.
“Marine mammals have evolved to take advantage of this basic physical fact to rely on hearing for virtually everything they do in the wild,” Jasny says. “We have radically altered a critical element of the marine environment.”
Noise from small vehicles, like motorboats, can block sounds, making fish more susceptible to predators, while noise from commercial shipping can occur at frequencies used by killer whales for echolocation.
More compelling is the critical mass of anecdotal evidence of whales coming ashore to die during sonar exercises. Scientists are now beginning to believe that sonar can give whales a form of ‘the bends,’ where gases build into air bubbles inside the body.
But figuring out how to temper underwater sound is harder than it looks. In 1972, Congress passed the Marine Mammals Protection Act, which requires that companies that harm marine life as a side effect of their business receive a go-ahead from wildlife organizations before conducting activities. Yet for the most part, companies haven’t followed this rule.
Even tracking noise from ships and other marine-based technology is tricky. In one study, a sound deployed off of Heard Island, in the southern Indian Ocean, was picked up by far-off monitors in the Northern and Southern Atlantic Ocean, as well as the Pacific. Getting a solid figure on how much this type of sound has increased is difficult, requiring a calibrated underwater microphone to be stationary over a period of decades. Using a sound surveillance system put in place during the Cold War, the U.S. Navy has tracked the rise of ocean noise in some locations. Surveying this data, scientists have discovered a steady increase of noise each decade, roughly corresponding with the doubling of commercial vessels between 1965 and 2003.
Still, despite all the challenges, researchers see a path forward. Some scientists have recommended that ocean noise be recognized as a pollutant, with global caps similar to those used for air pollution. Others have recommended creating designated quiet zones that would act as preserves for marine life.
“The point is not to have all human activity grind to a halt, and eliminate all shipping, all oil and gas exploration, all naval exercises,” says Weilgart. “But there are ways, there are solutions, for all these noise sources.”