Underwater cacophony caused by commercial and military ships has become so intense that it is killing whales, scientists at the World Conservation Congress here say.
Sounds ranging from the hum of yacht motors to sonar blasts strong enough to destroy a whale’s inner ear are wreaking havoc on the ability of these cetaceans to migrate, feed and breed, they said as a historic case began to be heard by the US Supreme Court. “The noises generated by ships create what I call acoustic smog,” said Michel Andre, director of the Laboratory of Applied Bio-Acoustics in Barcelona.
Many shipping lanes follow the coastal routes that whales have traced for millions of years as they roam the planet’s seas. The result is a crescendo of beachings, strandings and collisions as whales and other sea mammals disoriented or physically damaged by noise lose their bearings.
Recent research on a population of some 300 sperm whales living around the Canary Islands provide an unique window onto the problem.
Sperm whales normally migrate, but the squid upon which they feast are so plentiful in these waters that this group has made the region their permanent home, Andre said.
Maritime traffic, however, is taking a terrible toll — since researchers began monitoring the area, six to 10 whales have been killed each year by collisions with ships.
The consequences would extend beyond the loss of a whale population, he warned. “Each whale eats about one tonne of squid per day. All that uneaten squid would completely disrupt the food chain,” he said.
Some forms of noise pollution are so powerful that “a whale can be killed outright by the shock,” said Carl Gustav Landin, head of marine programmes for the International Union for the Conservation of Nature (IUCN).
Sonars used by the military and the oil industry can exceed 230 decibels in volume, and can be deadly within a one- or two-kilometer (-0.6 or 1.2-mile) radius, Andre said. Eighty-five decibels — the unit used to measure sound pressure — can cause permanent damage to the human ear.
The acidification of oceans caused by rising sea temperatures reduces sound absorption in the water by up to 40 percent, meaning that noise travels much further.
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– from AFP
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