Active Sonar: How It Works; How It Harms Marine Life
Jim-Bob
Of the 13 beaked whales that stranded in the Bahamas in March 2000 after
exposure to active sonar, seven died. - Center for Whale Research
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According to the Navy, LFA sonar functions like a floodlight, scanning the
ocean at vast distances with intense sound. Each loudspeaker in the system's
long array can generate 215 decibels of sound. Worse yet, not far from the
array the signals begin to combine, and the result as the signals travel can
be as forceful as 240 decibels transmitted at the source. (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.) One hundred miles from the system, the sound level would be from
150 to 160 decibels, still loud enough to cause permanent hearing damage in
humans.
Indisputable evidence of the harm such a barrage of sound can do to marine
life began to accumulate in March 2000, when members of four different
species of whales and dolphins stranded themselves on beaches in the Bahamas
after a U.S. Navy battle group used active sonar in the area.
Despite efforts to save the whales, seven of them died. The Navy initially
denied that active sonar was to blame, but its own investigation later found
hemorrhaging around the dead whales' eyes and ears, indicating severe
acoustic trauma. The government's study of the incident established with
virtual certainty that the strandings in the Bahamas had been caused by
mid-frequency active sonar used by Navy ships passing through the area.
Since the incident, the area's population of beaked whales has disappeared,
leading researchers to conclude that they abandoned their habitat or died at
sea.
Additional strandings and deaths associated with active sonar have occurred
in Madeira (2000), the Canary Islands, Greece (1996), the U.S. Virgin
Islands (1998, 1999), the Canary Islands (1985, 1986, 1989, 2002), and, most
recently, the Northwest coast of the United States (2003).
Perhaps the most graphic evidence of active sonar's dangers came in October
2003, when the scientific journal Nature reported that the technology's
intense sound may kill certain marine mammal species by giving them
decompression sickness or "the bends" -- the same illness that can kill
scuba divers who surface too quickly from deep water. The international team
of scientists that authored the study said compressed nitrogen apparently
formed large bubbles in the tissue of whales exposed to intense active
sonar, damaging their vital organs and causing internal bleeding and
possibly intense pain. This study supports something many scientists have
long suspected: that the whales and porpoises we've seen stranded on shore
are only the visible symptom of a problem affecting entire populations of
marine life.
Immersed in Sound
Whales use their exquisitely sensitive hearing like humans use their eyes --
their hearing helps them 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 stop singing,
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 was
been associated with an active sonar system being tested by NATO. And the
mass mortality of whales in the Bahamas only confirm the risks.
NRDC's Investigation of the U.S. Navy's Use of Active Sonar
LFA sonar was a Navy secret until 1994, when NRDC began investigating rumors
that sound experiments were taking place off the California coast. Despite
the Navy's stonewalling, it soon became clear that the Navy had already
field-tested LFA sonar in 22 operations -- but had never studied its effects
on marine life. Caught in violation of federal and state environmental law,
the Defense Department agreed to conduct a full-scale study of environmental
impacts and disclose how the sonar would affect marine mammals, sea turtles
and other ocean species before putting the LFA system into use.
The Navy released a final Environmental Impact Statement in 2001, but it was
disturbingly limited. Legally required to be a "rigorous and objective
evaluation" of environmental risks, the study failed 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? NRDC fought an eight-year battle
to force the Navy to answer such questions, and in the end the courts
agreed: The science clearly demonstrates "the possibility, indeed
probability, of irreparable injury" to marine mammals should LFA sonar be
deployed widely, and the reckless use of the system would violate a number
of our nation's environmental laws.
NRDC's efforts to bring attention to the serious risks of active sonar are
aided immensely by the tens of thousands of messages our members and other
activists have sent, demanding that active sonar not be used until the
long-term safety of ocean wildlife can be assured. Please continue to help
us keep the pressure on the U.S. Navy to meet its environmental obligations,
and begin to pressure the international community to regulate and lessen the
impact of high-intensity active sonar on the world's marine life, before
it's too late.