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Feature Story
Deadly Sonar
Page 2

The navy sonar problem is the controversial edge of a larger problem, the "ensonification" of the seas. John Hildebrand, a professor at the Scripps Institution of Oceanography in La Jolla, California, and a specialist in the effects of anthropogenic (human-generated) sound on marine mammals, is one of the authors of a recently released study that demonstrates that ambient anthropogenic sound in the world’s seas has increased tenfold since the early 1960s. He attributes most of this increase to bigger and more powerful ships. But he also blames it on such phenomena as the growing number of seismic surveys by the oil and gas industry (which can be literally deafening to whales and may cause them to strand) and on navy sonars including MFA (mid-frequency active) sonar, deployed on more than 100 fighting ships, and LFA (low-frequency active) sonar, a new type designed to flood entire ocean basins with sound. Beyond the sometimes fatal effect of sonar on individual whales, it’s unclear what the cumulative effect of this steep growth of ocean noise will be. The fear is that it will mask the ability of whales to communicate with one another, drive them from long-established migration routes, and prevent them from finding food and even from reproducing. "Our ignorance about marine-mammal behavioral responses to sound is abysmal," Hildebrand wrote in a recent book, "and knowledge of this subject must be improved."

In the early 1960s the world's navies began increasingly to experiment with "active" sonar, designed to bounce sound waves off approaching submarines. Prior to that, ships had detected submarines by using "passive" sonar, which consisted essentially of listening devices. From the U.S. Navy’s first deployment of active sonar, however, tests correlated closely with strandings of certain whale species. There had been strandings before, but with active sonar they became more frequent, occurring in close proximity to naval exercises, with whales left bleeding and dying on nearby shores. But the tests of active sonar were done in secret, and it was rare for scientists to be on the scene and in position to examine freshly stranded whales. In the absence of any studies showing a physical connection between sonar and stranding, the navy refused to accept responsibility.

The problem leaped an order of magnitude when, as the cold war wound down, the navy gradually moved away from its focus on containing Soviet nuclear submarines and toward a readiness for the rapid deployment of American power into the world’s coastal zones. In an "operational concept" paper, "Forward…From the Sea," Admiral Jay Johnson, chief of naval operations, articulated the new vision. "Seventy-five percent of the earth’s population and a similar proportion of national capitals and major commercial centers lie in the littorals [coastal regions]. These are the places where American influence and power have the greatest impact and are needed most often."

The challenge of the new strategy, however, was that deploying in narrow channels and close inshore left the navy’s surface ships vulnerable to a new generation of small, silent submarines. Because these submarines were almost impossible to hear with passive listening devices, in the mid-1980s, U.S. and allied navies steeply ramped up their experimentation with active sonar. The details have been shrouded in secrecy, but one indication of the importance the United States attributes to the sonar buildup is that at a recent International Law of the Sea conference in New York City, U.S. delegates quietly let it be known that, along with restrictions on greenhouse gas emissions, regulation of undersea noise was entirely off the table.

The difficulty for cetaceans arose from the navy’s conducting its sonar exercises in the deep, steep-walled underwater canyons that lie between certain islands and along the edges of continental shelves -- the sort of "acoustically complex environments," in navy terminology, where enemy submarines might set up "choke points" and lie in wait for surface ships. Unfortunately, this same underwater topography is used by a little-known family of deep-diving whales called beaked whales. Biologically, these whales have been so little studied that the conservation status of most of them, according to the World Conservation Union, is "data-deficient." They are perhaps the least understood large mammals in the world. Certain species have never been seen in the wild and are known only from carcasses that have washed up onshore.

As the number of active-sonar exercises grew, beaked whales began stranding in increasing numbers. They were found on beaches near the exercise sites, bleeding profusely from their eyes and ears, suffering from massive internal hemorrhaging or, as was discovered in the aftermath of a series of NATO exercises off the Canary Islands in 2002, from a condition similar to the decompression sickness, also called the bends, experienced by divers who have surfaced too quickly. There were major strandings in Greece in 1996 and 1997, in the Bahamas in 2000, in the Madeiras during that same year, and in the Canaries in 1989 and 2002. What many of these stranding sites had in common was that they were near places where deep underwater trenches abutted island archipelagoes. The preponderance of species stranded were beaked whales -- 81 percent were Cuvier’s beaked whales, the most "cosmopolitan," or widespread, members of the family.

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OnEarth. Spring 2007
Copyright 2007 by the Natural Resources Defense Council