For the last several years the U.S. Navy has been making plans to deploy Low Frequency Active Sonar (LFA), a new extended-range submarine-detection system that will create noise billions of times more intense than before in the world?s oceans. The National Marine Fisheries Service has proposed issuing a permit that would allow the Navy to proceed with LFA deployment and, in the process, to harass, injure, or even kill marine mammals while flooding the ocean with sound. The Navy wants to use LFA to deploy a global surveillance system to hunt for a new generation of silent enemy submarines. But marine scientists and environmentalists are fighting the proposal, saying it could prove lethal to whales and other marine mammals.
The Navy has used sonar to hunt for submarines for decades. Undeniable evidence that high-powered sonar systems kill marine animals emerged in March 2000, when beach strandings of four different species of whales and dolphins in the Bahamas coincided with a Navy battle group?s use of extremely loud active sonar there. Kenneth Balcomb, of the Center for Whale Research in Friday Harbor, Washington concluded that some whales died from a vibration in their cranial air spaces that tore delicate tissues around the brain and ears. The LFA sonar could cause the same damage, he believes. Despite efforts to save the whales, seven of them died. A National Marine Fisheries Service and Navy investigation established a connection between the strandings and the sonar.
The Navy wants to use four sonar ships in the Pacific and Atlantic oceans. On each ship, an array of 18 loudspeakers, each the size of a Volkswagen, hang in the ocean at a depth of about 200 feet. LFA functions like a floodlight, allowing its operator to peer enormous distances into the ocean in search of enemy submarines. Each one of the system?s long array of transmitters can generate 215 decibels of sound, a level millions of times more intense than is considered safe for human divers. After several hundred miles, the sound waves produced by the array converge, boosting the noise level to more than 240 decibels, the equivalent of the sound generated by an exploding rocket. Thanks to all these converging sound waves, LFA can explore hundreds of thousands of square miles of ocean at one time.
For years the Navy has been testing the LFA system in complete secrecy and in violation of environmental laws. According to a Navy study, scientists briefly exposed a 32-year-old Navy diver to LFA sonar at a level of 160 decibels — a fraction of the intensity at which the LFA system is designed to operate. After 12 minutes, the diver experienced severe symptoms, including dizziness and drowsiness. After being hospitalized, he relapsed, suffering memory dysfunction and seizure. Two years later he was still being treated with anti-depressant and anti-seizure medications.
Whales use their exquisitely sensitive hearing to follow migratory routes, locate one another over great distances, find food and care for their young. Noise that undermines their ability to hear can threaten their ability to function and survive. According to one scientist, ?A deaf whale is a dead whale.?
?There’s a possibility that it could disrupt whale communication,? admits Navy spokesman Lt. Douglas Spencer. ?But these systems are operated for a short period of time (about 430 hours a year) and they?re mobile. It?s highly unlikely there would be a permanent long-term effect.?
But what concerns marine scientists even more than short-term effects on individual animals is the potential long-term impact that the Navy’s LFA system might have on the behavior and viability of entire populations of marine mammals. Sound has been shown to divert bowhead and gray whales and other whales from their migration paths, to cause sperm and humpback whales to cease vocalizing, and to induce a range of other effects, from distressed behavior to panic. It is such long-term effects on vital activities, say the experts, that pose the greatest risk of pushing endangered species over the brink into extinction.
A mass stranding of beaked whales off the west coast of Greece in 1996 has been associated with an LFA-type system being tested by NATO. And last year?s whale deaths in the Bahamas add further evidence of the risks of intense active sonar. ?The Navy’s conclusions that the low-frequency sonar will work are premature and based on inadequate data,? says Naomi Rose, a marine mammal biologist at the Humane Society of the United States in Washington.
The Bahamas incident has led some scientists to speculate that military uses of sonar technology might explain other mysterious strandings. ?The Navy could very well have been causing these kind of traumas all over the world,? Rose says. ?Now comes a technology that is more likely to affect baleen whales. It?s as loud or louder. Because it?s a lower frequency, it?s going to travel farther over a larger area. And it?s never been out there before.?
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