Navy weapon tests and ship shock tests generate very high intensity sounds. All of these factors have the potential to interfere with marine mammals.
The issue is primarily legal as well as humanitarian. The United States has enacted a body of laws and is signatory to international agreements designed to protect marine mammals and endangered species. Protection ranges from outright bans on hunting and harvesting to more subtle prohibitions of those actions that might disturb, harass, or "take" these animals. Harassment and takes, as used here, are legal terms that are sometimes interpreted to include any activity that alters the animal's behavior in even minor ways. Behavioral modification, something as innocent as simply causing an animal to change swimming direction, is within the legal definition of take. To harass, to take, is unlawful without a permit.
Under present law, the preparation of detailed environmental impact statements is usually required by the National Environmental Policy Act to assess the potential for a significant environmental effect or the possibility of a take. Even for small-scale operations and experiments, these documents are costly to prepare and can take up to a year to complete.
"Take permits," permission to harass a small number of marine mammals from certain Navy at-sea experiments and operations, are also frequently required. Permits can take more than a year to process before they are granted, if they are granted at all. In some cases, elaborate environmental surveys and observations are required prior to and during the test period. Acoustic monitoring for the presence of marine mammals and for ascertaining the impact of the operation or test on the mammal or its habitat is also usually required. Compliance with the laws protecting marine mammals is expensive, time consuming, and potentially devastating to a Navy program. It can, and has, stopped programs cold.
Unfortunately, the underlying scientific understanding of the effects of sound on marine life, upon which to base reasonable strategies for ensuring that these laws are not violated and that marine life is protected, does not exist. As a consequence, decisions to issue the required permits either are arbitrary or are based on very limited data and frequently incorrect assumptions. For example, the safe level of exposure to underwater acoustic energy being proposed by some is 130 dB at 1 micropascal (about 65 microwatts), a value based on a single experiment involving bowhead whales.
This was the level at which 50 percent of migrating whales observed over a few days altered course to swim around an oil tower equipped with an underwater transmitter that emitted drilling-type noise. Whale tracks were altered by only a few degrees, and most whales resumed their original course after passing the tower. Whether this affected the whales in any negative way, both for the near-term and over the long term, is unknown. Whether it was anything more than an indication of hearing sensitivity is also unknown. Whether other species would react differently is unknown. Whether this event would occur at a different