Please Silence Your Sonar

The U.S. Navy agrees to give marine mammals off California and Hawaii a break from deafening noise.

Photo: John C. Bruckman/Flickr

Scientists often say that whales and dolphins see with their ears, mapping out their vast, dark underwater environment with an exquisite sensitivity to sound. And for many years now, the growing amount of manmade noise in the ocean has been blinding them.

One particularly devastating source of that noise is used by naval vessels to detect submarines and other objects beneath the surface. The intense, high-volume, and far-ranging sound waves blasted by active sonar are traumatic for marine mammals, and evidence has been mounting for more than a decade that they pose an existential threat to many species.

Since the mid-1990s, NRDC (disclosure) and partner conservation groups have pushed the U.S. Navy to deploy its sonar systems and conduct training exercises in ways that will reduce their impact on whales and dolphins, winning a series of court battles stretching back to 2003 (and going all the way to Supreme Court).

Over the weekend, NRDC and the U.S. Navy finally reached a federal court agreement regarding one of those long-running fights—in the whales’ favor. As a result of the settlement deal, the navy will silence its sonar in areas around Southern California and Hawaii during certain periods of the year when marine mammal populations are most vulnerable. The agreement, signed off on by the judge today, runs until the end of 2018, when the U.S. National Marine Fisheries Service is scheduled to issue new environmental impact statements and authorizations regarding military exercises in sensitive waters.

Advocates hope the win represents a turning point in the military's view that marine mammals are acceptable collateral damage in its training exercises.

Mass strandings are the most visible effect of active sonar on wildlife, and they often coincide with nearby naval deployments. In 2000, for example, 17 whales swam themselves aground in the Bahamas. A government investigation, published more than a year later, concluded that the most likely explanation was mid-frequency sonar emitted by the navy. The sonar caused “some sort of acoustic or impulse trauma” that drove the whales ashore, killing them.

Since the publication of that report, a rise in whale strandings worldwide has provided marine biologists with many unwanted research opportunities. We now know that intense sound waves can have direct physiological impacts on whales, including internal hemorrhaging and ruptured lung tissue. Sudden loud blasts not only lead to whales fleeing from their natural foraging and breeding grounds but can also make the animals rocket toward the surface, causing gas to precipitate out of their blood and tissue. The condition—which in human divers is known as decompression sickness, or “the bends”—can prevent the transport of oxygen and cause organ systems to fail.

Even if these acute ills do not occur, chasing whales away from their natural habitat decreases their chances to feed and breed successfully, potentially threatening the long-term survival of numerous species, many of which have already been hunted close to extinction.

The U.S. Navy doesn't deny the evidence linking its training exercises to whale deaths—it has even put its imprimatur on some of the research—but for many years, it has declined to respond appropriately. Conservation groups wanted the military to avoid sonar-based exercises at certain times and in defined places where marine mammals forage, breed, and migrate, but the navy drew a red line around such so-called "time-area closures."

In the NRDC-led lawsuit challenging the military's unfettered right to deploy sonar throughout the ocean, the U.S. Navy warned the judge that the proposed closures would hamper its “ability to adapt training” and “evolve as the threat emerges.” Forcing ships to move farther out to sea for training exercises, away from whale habitat, would also threaten the safety of our sailors, the navy argued.

U.S. District Court Judge Susan Oki Mollway was not convinced. In March, she accused the navy of refusing to contemplate any restrictions whatsoever, describing the national-security warnings as “pure hyperbole.” The strength of Judge Mollway’s opinion forced officials back to the negotiating table with NRDC and its allies, and the military brass finally accepted that time-area closures were unavoidable.

A well-defined area off the California coast between San Diego and Orange County, for instance, will be off-limits to sonar and explosives testing during the months-long summer migration of blue whales, the largest animal on earth. And the navy says it will no longer conduct training and testing in large portions of its most frequently used real estate west of San Clemente, California—where beaked whales, the leviathans most vulnerable to stranding, have the unfortunate fate of living.

The stakes are even higher in Hawaii, where the topography creates unique currents that bring otherwise deepwater species to the surface. Some whales and dolphins that spend almost their entire lives around the islands are severely threatened. Hawaii’s population of false killer whales, for example, has dwindled to around 150—a critically low census. The navy has agreed to place time limitations, or in some cases year-round prohibitions, on the use of sonar to protect these animals.

There’s a time and a place for sonar. For now, at least, the navy has agreed to fall in line.

onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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