The Dangers of High Intensity Military Sonar

There is now strong evidence linking fatal whale strandings to military sonar exercises. Other harmful effects of intense sonar to marine mammals include avoidance of and displacement from habitats, permanent tissue damage, and temporary hearing loss.

In order to detect enemy submarines over long distances, military sonar systems transmit some of the loudest manmade noises. Active sonar technology seeks targets by emitting high-energy acoustic pulses and then recapturing the echo from these pulses. High frequency systems (above 10kHz), which are used for weapon and counterweapon targetting, range from tens to thousands of meters.

Today, many countries including Australia, Canada, France, Italy, the Netherlands, Norway, Spain, Sweden, Turkey, the United Kingdom, and the United States deploy multiple high-intensity active sonar systems. Nearly 60 percent of the U.S. Navy’s 294 ships and submarines are currently equipped with mid-frequency active sonar systems. And powerful new “low-frequency” systems have begun to proliferate among member states of NATO.

During the Cold War, sonar programs were focused in large part on the deep-water environment, but today’s sonar systems are increasingly tested in coastal and shallow waters – environments that are home to endangered species of marine mammals, many important fisheries, and much of the richest habitat in the sea.

The link between sonar and whale strandings

Among the most dramatic and visible impacts of high-intensity sonar are mass whale strandings. The best documented cases occurred in the Bahamas in March 2000, when a naval exercise using sonar resulted in strandings of three different species across 150 miles of beach; one of those species, which local biologists had tracked for years, has subsequently all but disappeared from the area. But that stranding is only one of a mounting number of similar events including the Canary Islands (2002), US Virgin Islands (2002) and the US Pacific Northwest coast (2003).

The exact mechanism by which these sonars result in the death of the whales has yet to be established, but post-mortem studies found evidence of damage rather similar to decompression sickness or the ‘bends’ suffered by human divers.

Other harmful impacts of military sonar

Active sonar has been shown to alter the singing of humpback whales, an activity essential to the reproduction of this endangered species; to disrupt the feeding of orcas; and to cause porpoises and other species to panic and flee. It is feared that, over time, these effects could undermine the fitness of populations of animals, contributing to what the former Chief Scientist at NOAA has called “the death of a thousand cuts.”

When exposed to a Navy low-frequency sonar experiment in California, blue whale vocalizations decreased by approximately 50%, while fin whales decreased their vocalizations by about 30%. During a Navy-funded LFA experiment in Hawaii, humpback whales lengthened their songs by as much as 29%.