Navy under fire over sonar range - Soundings Online

Navy under fire over sonar range

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Critics say a sonar training area off North Carolina could endanger whales and other marine mammals

Critics say a sonar training area off North Carolina could endanger whales and other marine mammals

A Navy plan to establish an underwater range to train sonar operators in antisubmarine warfare has come under heavy fire because of sonar’s potential for causing whale strandings.

Read the other story in this package:  Navy under fire - Cause of stranding unclear

The Navy’s first choice for the 500-square-mile range is 60 miles off southeastern North Carolina. The waters are home to humpback, beaked and sperm whales, as well as a variety of dolphins, but critics are most concerned about the endangered right whale and the evidence of links between sonar and beaked-whale strandings.

The National Oceanic and Atmospheric Administration says it has “significant concerns” about the range because, among other things, the Navy plan doesn’t address right whales migrating through the Carolinas’ offshore waters in fall and spring. The North Atlantic right whale population is estimated to be about 300.

Critics of the range say evidence is mounting that sonar impairs hearing in whales and dolphins, and in extreme cases causes physical injury — bleeding around the ears and brain. Autopsies of some stranded whales — mainly beaked whales — suggest that an intense blast of sonar may cause them to surface too quickly and develop gas bubbles in their tissue, causing something like the “bends” that divers suffer. The Natural Resource Defense Council says some midfrequency sonar, the kind that would be used on the training range, can generate a 235-decibel blast of underwater sound. That sound travels through the water in a very short pulse and has a different quality than sound traveling through air.

Brandon Southall, NOAA acoustics program director, says the sound emitted by midfrequency sonar is comparable to that of lightning striking the water or of an underwater earthquake. The Navy’s studies suggest that permanent damage to a whale’s hearing generally doesn’t occur until 215 decibels, temporary hearing impairment at 195 to 215 decibels.

The science committee of the International Whaling Commission says the accumulated evidence that sonar is linked to beaked-whale strandings is “compelling.” Beaked-whale strandings in the Canary Islands, on the Greek coast, in the Bahamas and Puerto Rico, and Washington State and Hawaii have occurred during nearby naval exercises in which ships or submarines were using sonar. The committee estimates that in most cases the whales were exposed to sonar levels of 160 to 170 decibels.

“[The link] is becoming increasingly clear,” says Kyla Bennett, director of the New England branch of Public Employees for Environmental Responsibility, which opposes the range. “All the science is behind this.”

The Navy, which has funded a lot of the research into sonar’s effects on whales, joined the National Marine Fisheries Service in investigating a mass stranding of beaked whales in the Bahamas in 2000. Their findings concluded that midfrequency sonar from U.S. Navy ships was the likely cause. Yet the Navy says no one has a clear understanding of precisely how sonar might have caused this stranding.

“Right now there’s not a lot of evidence out there about the [specific] impacts of sonar,” says Jim Brantley, spokesman for Fleet Forces Command in Norfolk, Va. He says the Navy spends $10 million a year researching this, and the environmental impact statement reflects the current state of scientific knowledge. He says Navy critics can’t cite much hard science to support their position.

“They’re not using science,” he says. “They’re using speculation. They say, ‘We believe. We feel. We think.’”

Brantley says training sonar operators in shallow-water submarine detection is necessary to prepare them for hunting super-quiet diesel-electric subs that operate along the coast near shipping lanes.

The Navy received a deluge of comments — some 35,000 — in response to its draft environmental impact statement for the range (projects.earth tech.com/USWTR). The Navy concludes in the draft EIS that short-term exposure to its sonar might disturb some dolphins or some humpback and sperm whales, but it isn’t likely to injure them. Its prognosis for the beaked whale is less clear.

The International Whaling Commission report on the 2000 Bahamas stranding of 17 beaked whales says it appeared linked to the use of the sonar in a deep channel between two islands where the whales might have been swimming. The Navy EIS says conditions off North Carolina are different than those in the Bahamas where the beaked whales beached themselves, and the way the sonar will be used on the range will be different than the way it was used in Naval exercises in the islands.

The Navy says its research suggests that midfrequency sonar can cause physical injury to whales only when they get within 33 feet of a ship. It plans to use trained spotters and passive sonar to look for whales and dolphins during exercises, and will reduce sonar power when any of these creatures gets within 350 yards of a ship. It plans to closely monitor the range for evidence of marine-mammal injuries.

Aside from its concern about the range’s potential impact on right whales, NOAA told the Navy it was unsatisfied with the EIS because it bases its analysis of sonar’s impact on studies of captured whales. It should broaden its analysis to whales in the wild, does not consider that some beaked whales might die in strandings from exposure to sonar, and should offer more mitigating and monitoring measures.

While the link between sonar and strandings might not be conclusive, scientists are “seeing a correlation” between sonar and beaked whale strandings, says Donna Wieting, deputy director of the National Marine Fisheries Service’s office of protected species. She says NMFS must sign off on any impact the range might have on marine mammals that is more than “negligible.”

Brantley says the Navy and NOAA were talking over their differences. He says the Navy is confident a compromise can be reached and a final EIS adopted by summer’s end. He says the range wouldn’t be ready to open for at least two years, if approved. The Navy has identified waters off the Virginia Capes and Jacksonville, Fla., as alternatives.