As a species, Homo sapiens is characterized by the abilities to make tools and conduct complex communication. It is these attributes that have set us apart from all others on this planet, not because we're any better or more important than any other species, but because we have the greatest impact on all living things and the physical planet itself. Short of the evolution of oxygen-producing cyanobacteria billions of years ago that created the livable atmosphere, no other species has had such a large influence on the existence of so many other organisms.
As time progresses, the communication and tool-building abilities of the human species becomes increasingly complex, and from the days we started with the bludgeon and the cutting tool thousands of years ago, we have arrived at the advent of such things as the MacBook Air and Ununoctium (slightly different technology, I know). Essentially unchecked until recently, however, have been the effects of our creations and their byproducts on the atmosphere, land, and seas.
Ironically, one of our more advanced tools, one that is causing very damaging effects to other species, was adopted from them almost a century ago.
The members of the clade Cetacea, which includes whales, dolphins, and porpoises, live exclusively in the water, and hence have evolved special mechanisms of communication and hearing that work exceptionally well in that environment. Since water is a much better medium for transmission of sound than is air, cetacean ears are quite different from those of terrestrial mammals. In their evolution from land mammals, whales and other cetaceans have lost all external auditory anatomy, and have developed much more powerful internal ears, capable of sensing the direction of sounds up to tens of miles away. Some cetaceans, the odontoceti (toothed whales) also have developed an adaptation called echolocation, similar to that used by bats, some shrews, and cave-dwelling oilbirds.
The dolphin, for example, makes a series of rapid clicking noises (up to 600 per second!) by passing air through phonic lips, located just inside the blowhole. Sounds are transmitted through the dolphin's head, reflect off of bones in the skull, and are focused and modified by the varying-density lipids in the melon. These clicks are broadcast outward, and some sound waves are reflected off of objects in the water and return to the dolphin. The dolphin then receives the reflected waves through its jaw bone, which transmits the signal to the inner ear. The brain then processes the clicks (at 600/second) to determine the location, size, shape, trajectory, and density of the reflecting object. It is with these abilities that toothed whales can successfully navigate and hunt in low-visibility waters.
Through our advanced tool-making and communication abilities, humans have figured out how to replicate this adaptation with modern technology, called SONAR, short for SOund NAvigation and Ranging. There are two kinds: active and passive. Passive sonar consists of listening in the water to the sounds generated by other things. Active sonar works in a similar fashion to that of the dolphin's, by sending out sound waves to be reflected and returned. This is the "ping" that you often hear in movies with submarines (although modern submarines don't use active sonar very often any more because it can easily give away your position).
The first modern echolocation device was patented a month after the Titanic sank in 1912, and a similar device was demonstrated to detect the presence of icebergs up to 3 km away. Sonar technology has remained relatively consistent over the past century, with developments only in the use of computers and the power of listening devices.
Both active and passive sonar are commonly found in warships, submarines, and airplanes, and active sonar is used in some torpedoes. It's also common in fish-finders on personal and commercial fishing boats, and has several scientific uses, such as ocean-floor mapping.
The United States Navy continues to run trials and experiments with active sonar, with the goal of advancing threat-detecting abilities, using high-powered arrays with frequencies of 3-8 kHz and volumes up to 235 decibels. For comparison [PDF], standing one foot away from a jet engine as it's taking off is 180 decibels, which causes immediate inner ear tissue death, and a sonic boom, the loudest sound possible in air, is around 200 db.
Not surprisingly, with the use of these powerful sounds, the nearby marine life is being negatively affected. On several occasions, mass beachings of whales have been reported after sonar exercises in the Bahamas, Greece, and the Canary Islands and the Madeiras in the Eastern Atlantic. The stranded whales have been found with ears and eyes bleeding, and on necropsy of the heads of several after a 2000 Navy exercise in the Bahamas, scientists found massive hemorrhaging around the ears and brain due to severe sonic trauma. After a NATO test in 2002, another mass stranding of rare beaked whales gave scientists an opportunity to dissect whole whales, wherein they found the same brain hemorrhaging, but also bleeding of the vessels surrounding the liver, kidneys, and other internal organs, in addition to gas and fat bubbles, similar to "the bends." Based on this evidence, it would appear that, after being subjected to organ-crushing blasts of sound, the disoriented whales shot to the surface to try to escape the noise, incurring fatal air and fat emboli in the bloodstream.
The Navy, when confronted with this information, has consistently denied responsibility, and has been uncooperative with efforts by environmental and non-governmental panels to work toward a solution. Also problematic is the fact that a large percentage of marine mammal research in the United States is funded by the Navy, and so scientists aware of the damage being done have remained largely silent for fear of losing their funding.
In March of last year, the NRDC filed a lawsuit against the Navy to keep them from conducting dangerous sonar exercises off of the coast of southern California. In November, a US District Court judge in Los Angeles ruled that the Navy had not conducted sufficient environmental impact investigations, and ordered them to do so.
On January 16th, President Bush issued a special exemption to the Navy from provisions of the Coastal Zone Management Act, and the White House Council on Environmental Quality gave the Navy a waiver from the National Environmental Protection Act, effectively reversing the judge's ruling. The Navy is expected to resume their sonar testing activities, while lawyers for the NRDC are struggling to challenge the exemption.
Here's a dramatic yet motivating video by the NRDC on the effects of sonar on the whale populations around the world, and this is an article in the NRDC's OnEarth Magazine that provides some more information on the history and effects of sonar.
Keep tabs on this story, and to show your support you can visit the NRDC's Action Center, where you can learn about the many ways you can help them defend the environment.
Paddy
