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Sonar and Seismic
Exploration: A Major Headache for Whales
Use of Sound-based Technologies for
Ocean Exploration Has Scientists Worried
By Xanthe Pamboris, AquaNews Correspondent
September 13, 2004
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In
the Strait of Juan de Fuca in 2003, the USS Shoup (horizon)
deployed its mid-range sonar in the presence of killer
whales. Whalewatchers reported seeing distressed behaviour
from the whales.
Photo:
Centre for Whale Research/Ken Balcomb |
Imagine trying
to function with a jackhammer thundering on and off outside
your window, night and day.
Dr Lance Barrett-Lennard, Senior Marine Mammal
Research Scientist at the Vancouver Aquarium Marine Science
Centre, uses this analogy to describe the deafening torment
endured by whales in areas of oil and gas exploration.
Noise is even more detrimental to marine mammals
than to terrestrial creatures, as hearing is their primary sense.
And because sound travels so well in water, the noise could
be 50 kilometres away but will still seem like it is just around
the corner.
Marine noise is not a new phenomenon. Natural
noises occur in the oceans constantly, including earthquakes,
storms and singing baleen whales. However, it is the man-made
noises that are causing problems: in particular, military sonar
and the use of seismic testing for oil and gas exploration.
The Navy uses sonar to detect enemy submarines.
Sounds are emitted across the ocean and bounce back when they
hit an object. The lower the frequency of the sounds, the further
they travel. At present, mid-frequency active sonar (MFA) is
in widespread use and low frequency active sonar (LFA) is being
developed for use by the US and its allies. LFA sonar can generate
one of the loudest sounds that it is possible for humans to
make.
Whales use their own form of sonar – echolocation
– to navigate and to find food. They also use sound for
communication. The loud and far-carrying noise of sonar is thought
to disrupt the whales’ ability to navigate, forage and
communicate. It is also believed to cause the whales to panic,
inducing strandings and collisions.
Mid-frequency sonar can cause whales to make
a dramatic change in behaviour. On hearing sonar, whales may
dive or rise deeply and rapidly. This can cause a form of decompression
sickness, also known as ‘the bends’, resulting in
sometimes fatal damage to the lungs, brain and ears.
Sonar and Strandings
The International Whaling Commission (IWC) recently
released a report that backs up previous claims of the harm
sonar can do. The report suggests that the noise produced by
the military is damaging to cetaceans (whales, dolphins and
porpoises) and in particular, rare beaked whales.
The report cites recent cases, such as the unusual
behaviour in Hawaii of 200 melon-headed whales (Peponocephala
electra) in July 2004. These typically deep-water whales
were observed swimming in a tight circle in shallow water just
100 feet from shore, showing clear signs of distress. One of
the whales was later found to have died. This bizarre and near-stranding
behaviour coincided with a U.S.-Japanese naval training exercise.
A previous case documented the mass stranding
of 17 cetaceans in the Bahamas in March 2000. Six of the dead
animals, which included five Cuvier’s beaked whales and
one Blainville’s beaked whale, were found to have experienced
acoustic or impulse trauma that led to their stranding and subsequent
death. The strandings also coincided with ongoing Naval activity
using MFA sonar in the area.
When other sonar exercises have taken place,
mass strandings and whale mortalities have occurred. These include
cases in the Haro Strait off the coast of Washington State,
the Canary Islands, Madeira, the U.S. Virgin Islands, and in
Greece.
Despite numerous scientific studies and reports
proving the damaging effects of sonar, the US Congress passed
a new bill in November of last year that will allow the Secretary
of Defense to permit the Navy to use sonar wherever and whenever
they “need” to.
A coalition of conservation groups, including
NRDC (Natural Resources Defense Council) and The International
Fund for Animal Welfare (IFAW), are threatening to sue the US
Navy. They say the military’s use of mid-frequency sonar
violates laws imposed to protect marine mammals, such as The
Marine Mammal Protection Act, set up in 1972.
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Acoustic
researchers use spectrograms like this one to analyze
the calls of whales and dolphins.
Photo:
Volker Deecke |
Seismic Exploration
Another source of man-made marine noise is ‘seismic
exploration’ or ‘seismic testing’, which is
used by the oil and gas industry to detect the presence of fossil
fuels underwater. It is similar to sonar in that both rely to
varying extents on making sounds and listening for echoes. However,
seismic exploration takes advantage of the fact that sound penetrates
objects and surfaces to different degrees, depending on their
geological or biological makeup. This enables engineers to locate
oil deposits below the surface.
While man-made sonar devices measure distances
(the time interval between a sound pulse and its echo), seismic
sounds continue for long periods and provide more of a chronic
threat that can drive cetaceans from their critical habitat.
Environmentalists are currently condemning plans
by the Shell corporation to drill
for oil in the Russian Far East. The proposed construction
of an offshore drilling platform and the installation of a seabed
pipeline near Sakhalin Island could threaten the survival of
the area’s western gray whales, of which only 100 remain
world-wide.
In Canada, there are fears that a 32-year moratorium
on oil and gas exploration off the BC coast may soon be lifted.
As well as the considerable underwater noise that this would
cause, there is also the risk of an oil spill. If the moratorium
is lifted, exploration and drilling would take place in the
Queen Charlotte Basin, which is home to endangered species such
as the blue whale, sei whale, and North Pacific right whale,
as well as killer whales, fin whales, beaked whales, dolphins
and porpoises.
According to Dr. Barrett-Lennard, if things
are allowed to continue the way they are going, the outlook
for marine mammals is not good.
“Noise as a form of chronic environmental
degradation is a relatively new notion,” he says, “but
it is my opinion that seismic exploration and the use of sonar
are two of the greatest threats to cetaceans at present, and
all the indications are that they are going to get worse.”
Xanthe
Pamboris is a British freelance
wildlife writer with five years' experience
at the BBC's Natural History Unit.
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