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Executive Summary

It is a commonplace among divers and oceanographers that the ocean is no "silent world," as Jacques Cousteau had written, but an exceptionally noisy place. Most whales and many other marine species depend on sound as they hunt for food, detect predators, find mates, and maintain their awareness in the darkness of the sea. Over the past century, however, the acoustic landscape of the ocean has been transformed by human activity. Some biologists have compared the increasing levels of background noise in many places off our coasts to a continuous fog that is shrinking the sensory range of marine animals. Others, concerned about a growing number of whale mortalities linked to military sonar, have compared the effects of intense sound to those of dynamite. Together these analogies suggest the range of impacts that noise can have: from long-term behavioral change to hearing loss to death.

Since 1999, when the first edition of this report was published, the scientific record and the public's awareness of the issue have grown with astonishing rapidity. It has become increasingly clear that the rise of ocean noise presents a significant, long-term threat to an environment that is utterly dependent on sound. Our purpose in this report is to review the science, survey the leading contributors to the problem, and suggest what might be done to reduce the impacts of noise on the sea-before the proliferation of noise sources makes the problem unmanageable.

The Rise of an Environmental Problem

There is general agreement that hearing is probably the primary sense of whales, dolphins, and other marine species, as vitally important to them as seeing is to us. Yet the acoustic environment is increasingly overshadowed by a gamut of military, commercial, and industrial sources: dredgers that clear the seabed for ship traffic, pipelines, and structures; high explosives for removing oil platforms and testing the seaworthiness of military ships; pile drivers for construction; harassment devices for fisheries; tunnel borers; drilling platforms; commercial sonar; modems; transmitters; and innumerable jet skis and power boats. In deep water, background noise seems to be growing by about three to five decibels per decade in the band occupied by commercial ships. In some areas near the coast, the sound is persistently several orders of magnitude higher than in less urbanized waters, raising concerns about chronic impacts on marine life. Among the leading contributors to the problem:

  • Military active sonar systems put out intense sound to detect and track submarines and other targets. Midfrequency tactical sonar, which is currently installed on close to 200 American vessels and on the ships of other navies, is linked to a growing number of whale strandings worldwide. Low-frequency sonar, which has proliferated rapidly over the last decade, can travel hundreds of miles at intensities strong enough to affect marine mammals. Navies are increasingly using both types of systems (a list of which is contained in the report) in coastal waters.

  • High-energy seismic surveys are used by industry to detect oil and gas deposits beneath the ocean floor. Surveys typically involve firing airguns every few seconds at intensities that, in some cases, can drown out whale calls over tens of thousands of square miles. The industry conducts more than 100 seismic surveys each year off the coast of the United States, and that could increase significantly with the passage of the Energy Policy Act of 2005, which mandates an inventory of the entire U.S. outer continental shelf. Global hot spots (which are mapped in the report) include the Gulf of Mexico, the North Sea, and the west coast of Africa.

  • The low-frequency rumble of engines, propellers, and other commercial shipping noise can be heard in virtually every corner of the ocean. Over the last 75 years, the number of merchant ships has tripled, and their cargo capacity (which relates roughly to the amount of sound they produce) has increased steadily. Some believe that the biggest ships will become faster and larger still, possibly tripling in capacity, and that their numbers will double over the next 20 to 30 years. Increasingly, short hauls between ports could take cargo ships nearer to shore-directly through coastal habitat for many marine species.

That some types of sound are killing some species of marine mammals is no longer a matter of serious scientific debate. A range of experts, from the International Whaling Commission's Scientific Committee to the U.S. Navy's own commissioned scientists, have agreed that the evidence linking mass strandings to mid-frequency sonar is convincing and overwhelming. Suspect strandings have occurred off the Bahamas, the Canary Islands, the U.S. Virgin Islands, North Carolina, Alaska, Hawaii, Greece, Italy, Japan, and other spots around the world. Some stranded animals have been found to suffer bleeding around the brain, emboli in the lungs, and lesions in the liver and kidneys, symptoms resembling a severe case of decompression sickness, or "the bends." That these injuries occurred in the water, before the animals stranded, has raised concerns that whales are dying in substantially larger numbers than are turning up onshore. Other sources of noise, such as the airguns used in seismic surveys, may have similar effects.

But to many scientists, it is the cumulative impact of subtle behavioral changes that pose the greatest potential threat from noise, particularly in depleted populations: what has been called a "death of a thousand cuts." We know that sound can chase some animals from their habitat, force some to compromise their feeding, cause some to fall silent, and send some into what seems like panic. Preliminary attempts at modeling the "energetics" of marine mammals (the amount of energy an animal has to spend to compensate for an intrusion) suggest that even small alterations in behavior could have significant consequences for reproduction or survival if repeated over time. Other impacts include temporary and permanent hearing loss, which can compromise an animal's ability to function in the wild; chronic stress, which has been associated in land mammals with suppression of the immune system, cardiovascular disease, and other health problems; and the masking of biologically important sounds, which could be disastrous for species, like the endangered fin whale, that are believed to communicate over long distances.

Although marine mammals have received most of the attention, there are increasing signs that noise, like other forms of pollution, is capable of affecting the entire web of ocean life. Pink snapper exposed to airgun pulses have been shown to suffer virtually permanent hearing loss; and the catch rates of haddock and cod have plummeted in the vicinity of an airgun survey across an area larger than the state of Rhode Island. Indeed, fishermen in various parts of the world have complained of declines in catch after intense acoustic activities, like oil and gas surveys and sonar exercises, moved onto their grounds, suggesting that noise is seriously altering the behavior of commercial species. Other potentially vulnerable species include brown shrimp, snow crabs, and the giant squid, which is known to have mass stranded in the vicinity of airgun surveys.


The Domestic And Global Response

As yet, there is no domestic or international law to deal comprehensively with ocean noise. The closest approximation in the United States is the Marine Mammal Protection Act (MMPA), which requires those who would harm animals incidentally, as an unavoidable consequence of their business, to first obtain permission from one of the wildlife agencies. Congress dictated a precautionary approach to management given the vulnerable status of many of these species, their great cultural and ecological significance, and the exceptional difficulty of measuring the impacts of human activities on marine mammals in the wild.

When it has come to ocean noise, however, the MMPA's mandate has not been fulfilled.

  • Most of the leading contributors to the problem of ocean noise are not currently regulated. With few exceptions, the U.S. Navy has not sought to comply with the MMPA on its sonar training exercises; oil and gas companies often conduct surveys off Alaska and in the Gulf of Mexico without authorization; and commercial shipping remains entirely unregulated. Lack of adequate funding is partly to blame, as is the recalcitrance of some powerful noise producers; but it can also be said that the agency with primary authority, the National Marine Fisheries Service (NMFS), has tied its own hands, declining to use the enforcement power available under law.

  • Mitigation measures that could make the most difference are generally not imposed. As concern has mounted, scientists and policymakers have given more thought about ways to prevent and mitigate the needless environmental impacts of ocean noise. Among the most promising measures are geographic and seasonal restrictions and technologies that curb or modify sound at the source. To date, however, regulators have relied primarily on operational requirements, such as visual monitoring, whose effectiveness -- particularly for some of the most vulnerable species of whales -- is highly limited.

  • Legal standards are increasingly being defined in ways that limit the MMPA's effectiveness. The NMFS has moved the threshold for regulatory action steadily upward over the years without any breakthroughs in research and, indeed, while studies on some species would seem to lead in the opposite direction. And changes that Congress has made to the threshold make the Act more difficult to enforce.

  • Cumulative impacts of ocean noise have not been addressed in a meaningful way. This record is partly due to the basic empirical difficulty of determining when a population-level impact might occur, but also to the fragmentation of the permitting process, which relieves pressure on the agency to consider a broader set of impacts.

But undersea noise is not just a national issue: It is a global problem. Many noise-producing activities occur on the high seas, a gray zone of maritime jurisdiction, and both sounds and affected species have little respect for boundaries. Fortunately, as scientific and public consensus has crystallized around ocean noise, so has international recognition that the strategy for reducing it must be regional and global. A number of international bodies, including the European Parliament, the International Whaling Commission's Scientific Committee, and several regional seas agreements, have begun to address the problem, urging that nations work together. Options range from the direct, comprehensive control that a federal system like the European Union can exercise; to the guidelines or regulations that specialized bodies such as the North Atlantic Treaty Organization and the International Maritime Organization can propose for certain activities; to the coordination that regional agreements can bring, particularly to matters of habitat protection. Unfortunately, the present U.S. administration has opposed the international regulation of active sonar, which may weaken its leadership and standing on the broader issue of ocean noise.


The Way Forward

The mass strandings that have emerged over the last several years are a wake-up call to a significant environmental problem. We do not believe that an issue of this complexity can or will be settled tomorrow. Yet now is the moment when progress is possible, before the problem becomes intractable and its impacts irreversible.

With this in mind, NRDC recommends that the following steps be taken:

  • Develop and implement a wider set of mitigation measures. Regulatory agencies in the United States, the NMFS and the Fish and Wildlife Service, should move beyond the inadequate operational requirements that are currently imposed and develop a full range of options, particularly geographic and seasonal restrictions and technological (or "sourcebased") improvements.

  • Build economies of scale. Agencies should use programmatic review and other means to develop economies of scale in mitigation, monitoring, and basic population research. In conducting programmatic review of noise-producing activities, the agencies should take care to make threshold mitigation decisions early in the process and to allow public participation at every stage, as the law requires.

  • Improve enforcement of the Marine Mammal Protection Act. The NMFS should exercise the enforcement authority delegated by Congress under the Act to bring clearly harmful activities, such as sonar exercises and airgun surveys, into the regulatory system and should adopt process guidelines to ensure that an arm's length relationship is maintained with prospective permittees. And Congress should add a "citizen-suit" provision to the MMPA, which would empower the public to do what, in some cases, the regulatory agencies will not.

  • Increase funds for permitting and enforcement. The U.S. Congress should increase the NMFS's annual budget for permitting and enforcement under the MMPA.

  • Set effective standards for regulatory action. So that the MMPA can serve the protective role that Congress intended, the act's standards for "negligible impact" and behavioral "harassment" should protect the species most vulnerable to noise, ensure that major noise-producing activities remain inside the regulatory system, and enable wildlife agencies to manage populations for cumulative impacts.

  • Establish a federal research program. Congress should establish a National Ocean Noise Research Program through the National Fish and Wildlife Foundation, or similar institution, allowing for coordination, reliability, and independence of funding. A substantial portion of the budget should be expressly dedicated to improving and expanding mitigation measures.

  • Commit to global and regional solutions. The United States and other nations should work through specialized bodies such as the International Maritime Organization to develop guidelines for particular activities like shipping noise; through regional seas agreements to bring sound into the management of coastal habitat; and through intergovernmental regimes, like the European Union, to develop binding multinational legislation.


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