Sonar System Threatens Marine Mammals
For the last several years the U.S. Navy has been moving ahead with plans to deploy Low Frequency Active Sonar, or LFA -- a new extended-range submarine-detection system that will introduce into the world's oceans noise billions of times more intense than that known to disturb large whales. Now 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 intense noise.
Undeniable evidence that high-power "active" sonar systems can and do 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. Despite efforts to save the whales, seven of them died; A National Marine Fisheries Service and Navy investigation established with virtual certainty a connection between the strandings and the sonar -- and that active-sonar system put out mid-frequency sound, which generally does not travel as far as LFA.
Although active sonar has been suspected in previous strandings, analysis of the inner ears of several dead whales enabled scientists to confirm, for the first time, the dangerous role of active sonar to a level of certainty that even the Navy could not ignore. All but one of the whales suffered hemorrhages in the inner ear, almost certainly the result of a sonic blast. And in February 2001, a marine scientist observed that at least one of the whale species that stranded in the Bahamas had virtually disappeared from the area, raising questions about impacts well beyond the initial strandings and deaths.
According to the Navy, LFA functions much 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 meters, the sound waves produced by the array converge, boosting the noise level to an equivalent of more than 240 decibels. (To understand just how powerful these sounds are, keep in mind that the decibel scale used for measuring noise is like the Richter scale used for measuring earthquakes -- both use small differences to express increasing orders of magnitude.) Thanks to all these converging sound waves, LFA can illuminate hundreds of thousands of square miles of ocean at one time. In 1991, for example, scientists produced a loud, low-frequency signal off the coast of Heard Island in the southern Indian Ocean, and found that it was still detectable off the West Coast of the United States. That signal was effectively 100 times less powerful than LFA's.
For years the Navy had been testing the LFA system in complete secrecy and in violation of environmental laws. In 1995, NRDC brought the sonar tests to light and demanded that the Navy comply with federal and state statutes and disclose how the sonar would affect marine mammals, sea turtles and other ocean species. As a result, the Pentagon agreed to conduct a full-scale study of environmental impacts before putting the LFA system into use across an estimated 80 percent of the world's oceans.
In late January, the Navy released its Environmental Impact Statement, which according to law should be a "rigorous and objective evaluation" of environmental risks. Yet the Navy's study fails to answer the most basic questions about its controversial system: How will LFA affect the long-term health and behavior of whales, dolphins and hundreds of other species? Taking place as it does over an enormous geographic area, what effect might it have on marine populations?
According to the Navy's 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 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. As one scientist succinctly put it: "A deaf whale is a dead whale." 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. 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.
Leading marine experts say the Navy's limited assessment cannot tell us how long-term exposure to LFA sonar will affect the breeding, feeding, and migration of whales and other marine species. It is exactly such long-term effects on vital activities, say the experts, that pose the greatest risk of pushing endangered species over the brink into extinction.
The National Marine Fisheries Service announced its proposal to permit LFA even as its own investigations into the Bahamas strandings continue. In the wake of the recent dramatic confirmation of the dangers of active sonar, NRDC is calling on the Fisheries Service to withdraw its proposed permit and deny the Navy's application to deploy LFA. Please add your voice to this call and tell the Fisheries Service to stop LFA deployment.