Noisy Neighbors: How Acoustic Pollution Threatens Whales
- Sound for survival
- Listening to global warming
- Impact on migration
- Weapons tested on whales
- Sea lions under fire
- UK Navy deploys lethal sonar
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The oceans now resound to a cacophony of underwater noise from ships, echo sounders, seal scaring devices, underwater loudspeakers, explosives, dredging, seismic survey air guns, drilling rigs, and active sonar systems. Although whales and other marine mammals have evolved to cope with natural ambient sounds such as from air bubbles, waves, even earthquakes, there is mounting evidence that the huge increase in human generated noise invading the ocean depths is strongly detrimental to the health and wellbeing of cetacean populations.
Sound for survival
Whales, dolphins and porpoises rely on underwater sound for survival. Sound is used for communication, social bonding, foraging, feeding and navigation. For the great whales, much of this essential acoustic activity takes place in the low frequencies below 1,000 Hertz – a band increasingly cluttered by some of the loudest human-produced sounds. For example, a cruising super-tanker generates a low frequency sonic roar at about 200 decibels – the equivalent of a commercial jet at take-off. According to the Natural Resources Defence Council (NRDC), ‘the cumulative noise of all sea-going vessels is an incessant drone of near-constant sound in a growing number of oceans regions’. Seismic surveys, conducted during offshore oil and gas exploration, use rapid discharges of compressed air from air gun arrays. These send acoustic shock waves down through the water column that is reflected back from sub-sea rock strata. The blasts are emitted every 10 seconds and may be as loud as 250 decibels. Other sources of acoustic pollution associated with offshore oil and gas activities include drilling, platform machinery, vessel traffic, low-flying aircraft and helicopters, and the movement of oil, gas or water through valves and under-sea pipelines.
Listening to global warming
Sound travels at different speeds, depending on the temperature of the ocean water. Climate researchers know this and at the US Scripps Institution of Oceanography, they aim to use sound transmitted across the North Pacific to help detect global climate change. The Acoustic Thermometry of Ocean Climate (ATOC) experiment is currently underway from near Hawaii. The sound source, located in humpback whale breeding and calving ground, emits a low frequency, deep rumble that travels via the ”Deep Sound Channel” used by several whale species to communicate. It is believed to operate at 195 decibels for 20 minutes – every four hours, one day in four. Such low-frequency sounds can travel thousands of miles, further stressing marine mammals whose lives depend on a highly refined sense of hearing. Although there are large gaps in our knowledge regarding ”bio-acoustics” and the long-term impacts of acoustic pollution on marine mammals, there is sufficient evidence to suggest that the consequences for marine life could be very grave.
Impact on migration
In addition to the risk of cumulative damage to the animals hearing, noise pollution can also disrupt normal behavior including migration patterns, as well as feeding and breeding sites. Gray whales have been seen to alter their migration routes to avoid loud noise. Endangered Bowhead, sperm whales, humpback whales and common dolphins are known to avoid areas of seismic surveys. Likewise, important cetacean prey species such as fish and squid may be affected during seismic surveys. Beluga whales have ceased vocalising for hours, even days, after low-frequency noise encounters. According to the NRDC, two sperm whales, suffering from inner ear acoustic trauma, were struck and killed by a cargo ship they could not hear approaching them.
Weapons tested on whales
The military now threaten to make the world of whales and dolphins even more uncomfortable. During 1998, scientists funded by the US Navy, deliberately exposed humpback and sperm whales off the Hawaiian coast to a battery of low-frequency sound emitted from a Naval vessel. Earlier, tests were conducted on migrating gray whales off the California coast to observe changes in behavior caused by increasing levels of low-frequency sound. The tests are required for an Environmental Impact Statement (EIS) on the Navy’s experimental Low Frequency Active Sonar (LFAS) system.
The US and NATO are developing LFAS to detect ”quiet” submarines. The system emits pulses of very loud low-frequency sound, reportedly in the range of 235 decibels or higher. Naval vessels and installations monitor the returning echoes. The Hawaiian test aimed to use just enough sound to make the endangered whales react, but not enough to ”hurt” them.
However, scientists have not been able to say with any certainty whether the humpbacks, sperm whales and other species nearby were not harmed! Unusual whale behavior was reported over a wide area, often far from the sound source, while humpback whales swam away from the test site to the other side of the island. Scientists and Navy officials were quick to dismiss any links between the tests and sightings of seemingly distressed whales. A young humpback whale was reported to have breached some 230 times in a row during the sound transmissions!
The Military has been testing variants of LFAS since the early 1990s. In 1992, scientists recorded disruption of pilot whale behavior in the Mediterranean caused by sonar signals emitted from an Italian naval vessel. In May 1996, 12 Cuvier’s beaked whales stranded and died on the Greek coast. Coincidence or not, this unusual event occurred during LFAS tests by a NATO vessel.
The US Navy is about to deploy its LFAS system. The Pentagon has concluded that the sonar program ”can be safely operated” with ”negligible impact on marine life”. They must now convince the public that this is the case.
Sea lions under fire
The LFAS system is not the only ”acoustic weapon” being developed in the US that will affect marine mammals. However, this time any negative impact is quite deliberate! The US National Marine Fisheries Service (NMFS) is planning to bombard California sea lions with pulsed underwater noise, as loud as 230 decibels, in a test to protect certain commercial fisheries. The new pulsed-power “acoustic harassment” technology may be a potentially deafening as well as disorienting experience for marine mammals in the vicinity. Damage to a marine mammal’s ears threatens its survival.
Those animals unfortunate enough to be swimming within close range of the pulsed power generator are likely to be seriously injured, even killed by the sheer force of such loud blasts. The danger of temporary or permanent hearing loss is corroborated by a new study that reveals sea lions can suffer hearing loss from prolonged exposure to only 140 decibels. US Government officials have been warned that the tests might contravene several environmental laws, but NMFS has shown no sign of backing down – so far. Not surprisingly, US environmental groups are campaigning against the tests.
The human impact on whale and dolphin habitats can only increase with serious consequences for all ocean life. As we examine and assess these threats individually, it is important to remember that their combined impact remains unpredictable, but potentially catastrophic.
UK Navy deploys lethal sonar
Several UK Navy frigates have now been fitted with Sonar 2087, a type of sonar implicated in the deaths of whales. Despite the repeated concerns of UK based organisations, the MOD has continued with deployment of Sonar 2087 arguing that sufficient environmental safeguards are in place, including onboard observers that will be on the lookout for whales in the vicinity when the sonar is switched on.
The fact that this sonar is powerful enough to harm whales and other sea life over great distances makes a mockery of the MODs claims that onboard observers are in any way an adequate safety measure. Campaign Whale is calling for an immediate suspension of the further deployment and use of powerful military sonar’s that are capable of harming whales and other sea life.
End of report
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