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AEI Special Report

Marine Mammal Commission
Advisory Commitee on
Acoustic Impacts
on Marine Mammals


The MMC has made most of the papers presented at the plenary
meetings available online. In February 2006, a report was released that included statements from committee members; in March 2007, the Commission released its final report, which also includes the committee member/caucus statements.




Beginning in early 2004, and continuing through late 2005, the Marine Mammal Commission convened a Federal Advisory Committee on Acoustic Impacts on Marine Mammals (FACA), which attempted to find consensus among diverse stake holders on this difficult issue. Representatives of federal agencies, environmental groups, the shipping and oil and gas industries, and the Navy discussed scientific research (both current knowledge and future priorities), permitting, and mitigation measures over the course of six plenary meetings and one international symposium.

The 28-member Advisory Committee was directed in its charter to:

  1. Review and evaluate available information on the impacts of human-generated (anthropogenic) sound on marine mammals, marine mammal populations, and other components of the marine environment,
  2. Identify areas of general scientific agreement and areas of uncertainty or disagreement related to such impacts,
  3. Identify research needs and make recommendations concerning priorities for research in critical areas to resolve uncertainties or disagreements, and
  4. Recommend management actions and strategies to help avoid and mitigate possible adverse effects of anthropogenic sounds on marine mammals and other components of the marine environment.

The FACA met six times during 2004 and 2005. A final report made it through two formal drafts, but the group was unable to reach consensus in some key areas. As a result, the FACA's "Final Report to the Marine Mammal Commission" issued in February 2006 consists of "statements" from each of the main "caucus" groups, as well as from two other participants.

The Marine Mammal Commission staff and scientists compiled their own final report to Congress, which incorporated information from the caucus statements and material presented in the meetings. This report, entitled Marine Mammals and Noise: A Sound Approach to Research and Management, was released in March 2007, and is a well-constructed overview of the state of research, understanding, and challenges as of early 2007. The MMC report also includes, as appendixes, the FACA "Final Report", a report on a separate workshop held in the UK on international efforts to address noise, and a report on anthropogenic noise and beaked whales. [DOWNLOAD REPORT (pdf)] Among the key recommendations made by the MMC in this report to Congress were:

  • To provide adequate funding to expand research on the effects of noise
  • Such research to be overseen by the MMC as chair of an inter-agency initiative
  • The need to provide uniform regulation of ocean noise (including regulation of currently unregulated activities such as private boating, especially whale-watching, and aquaculture, which is increasingly using acoustic devices to keep seals and dolphins from "harvesting" fish-farms)
  • The importance of addressing sub-lethal impacts, such as acoustic masking and behavioral disruptions.
  • Streamline permitting for research on the effects of noise
  • Encourage the US to take the initiative to provide international leadership on addressing ocean noise, especially of shipping

The major casualty of the failure of the FACA to reach consensus was the promise of clearly identifying areas in which there is substantial agreement about the effects of noise and current management methods. From this point, it would be more likely that areas of disagreement and uncertainty might be addressed in a collaborative, or at least cooperative, way. By separating out the caucus statements, we are left with an incomplete picture of where the common ground lies. The MMC's report attempts to spell out the current state of shared understanding, but steers clear of pinpointing the areas of contention. Of course, underlying most of the disagreement is the level of uncertainty in our understanding of the effects of noise; much of the difficult terrain is shaped by differing approaches to moving forward within this uncertainty.

In this AEI Special Report, I will attempt to give a sense of the main themes presented by each of the caucus statements, and provide a a bit of mild commentary on the areas in which agreement appears to have been impossible.

Scientific Research: Current Knowledge of Marine Mammal Responses to Human-generated Noise

There was agreement among all participants that our knowledge base is limited. The Federal Caucus noted that of 83 species of cetaceans, we only have clear audiograms (which show how sensitive the species is to various frequencies of sound) for 11 species, none of which are large baleen whales. Beyond knowing what animals can hear, our understanding of their behavioral responses to human noise is similarly sketchy, based on a relatively few studies of any given species.

Indeed, the Scientific Research Caucus suggested that "the greatest ambiguity of all for assessing the risk of sound on marine mammals involves our uncertainty in what kind of behavioral response is evoked by a specific dosage of sound. In many cases, we do not even know the correct way to represent the sound dosage. The behavioral responses an animal makes to a sound are more variable than physiological responses, and can depend on the species, population, age-sex class, behavioral context, hearing sensitivity, and history of exposure of the individual. It is impossible to study responses of all species to all sounds, so studies must be prioritized based upon expectation of the potential for harm."

All participants acknowledged that four mass stranding events seem to be linked to exposure to mid-frequency active sonar, and there was no apparent disagreement that many species at times change their behavior so as to maintain some distance from sound sources.

An interesting and key point was made by the Federal Caucus. They noted that while it may be reasonable to assume that animals will avoid sounds that are harmful to them (for example, that are loud enough to cause temporary or permanent hearing damage), we do not have any empirical evidence that the situations that trigger an avoidance response bear a consistent relationship to sound levels that cause injury. (There is, in fact, much contradictory evidence, including some avoidance at sound levels just above perceptible and other situations in which animals remain in close proximity to loud sound sources, likely to continue feeding.)

The Scientific Research Caucus noted that there remains a question about whether sound is a "first-order" problem in marine conservation (i.e., whether it is causing direct effects comparable to known toxins, fishing by-catch, and the like). Is sound a secondary issue, or are we just beginning to appreciate its seriousness? They quote the 2005 National Research Council Report:
"In the presence of clear evidence of lethal interactions between humans and marine mammals in association with fishing and vessel collisions..., the absence of such documentation has raised the question of the relative importance of sound in the spectrum of anthropogenic effects on marine mammal populations... On the one hand, sound may represent only a second-order effect on the conservation of marine mammal populations; on the other hand, what we have observed so far may be only the first early warning or “tip of the iceberg” with respect to sound and marine mammals.

Population-level impacts?

Perhaps most central to the current scientific consensus is the question of how to determine when, or if, noise is causing impacts that move beyond the individual (e.g., triggering a behavioral change such as moving away from a transient sound source or changing call patterns in response to chronic noise), to a point that long-term population health is affected. There is currently sharp contention about whether key regulations (such as the Marine Mammal Protection Act) should be applied to individual animals, or only to populations. There is furthermore a lack of consensus about whether population level effects have already been documented or not, as well as about how or whether to adopt risk assessment models that attempt to address population level affects by extrapolating from cumulative impacts on individual animals in a population.

There was a divergence around the question of whether we have evidence to suggest that such behavioral changes among individuals can affect longer-term population vitality. The Scientific, Federal, and Energy Producers' Caucuses all cited a 2005 National Research Council report that claimed “no scientific studies have conclusively demonstrated a link between exposure to sound and adverse effects on a marine mammal population.” The Environmental Caucus, and the statements of the California Coastal Commission and Kenneth Balcomb, pointed to studies that identified local populations that seemed to make large-scale and long-term changes in behavior, such as leaving long-time feeding or breeding grounds, in response to noise (as well as the apparent disappearance, through either abandonment of habitat or death, of the entire population of beaked whales affected by the 2000 sonar incident in the Bahamas). They also pointed out that there have as yet been no studies aimed at directly addressing the link between population vitality and noise, and that, in any case, population estimates are one of the many weak links in our knowledge of marine mammals (only a handful of species have population estimates more precise than +/- 40%). The Environmental Caucus also cited several studies in which transient disturbances which caused only minor short-term behavioral changes may be associated with measurable long-term population level impacts. They further raised a question about whether a strictly cumulative model can be relied upon to assess population-level impacts. (One such model was suggested by the National Research Council, and supported by the Scientific Research Caucus and Federal Caucus; this mathematical approach, in which each minor behavioral change or impact on individual animals is weighted and added, attempts to assess accumulations of disruption which may compromise population health.) The Environmental Caucus stressed a need to conduct studies that address population health directly, and seemed convinced that the widespread noise in today's oceans is clearly a population-level threat, citing a 2004 International Whaling Commission Scientific Committee report that made the same point: “Repeated and persistent acoustic insults [over] a large area...should be considered enough to cause population level impacts.” By contrast, as noted above, other Committee members remained reluctant to assume population level impacts are being caused by noise.

The Energy Producers Caucus suggested that contrary to to the concern that noise threatens population vitality, some populations have increased even as noise has increased (e.g., grey whales along the California coast).

Chronic Moderate Noise/Rising Ambient Background Noise

Both the Scientific Research and Federal Caucus reports pointed out that short-term exposure to extreme noise sources is not the only issue at hand; they stressed the pressing need to address chronic exposure to moderate noise, and to better understand the impacts of the rising levels of background ambient noise in the oceans. In particular, the Federal Caucus suggested that lower level chronic noise is more likely to cause population-level impacts, due to masking of communication and navigation signals. Similarly, the Federal Caucus listed as their first research priority a need to better assess the cumulative effects of multiple exposures that change behavior, combined with the effects of background noise.

The Environmental Caucus also addressed the rising background ambient noise issue, and further urged more attention to the effects of noise-induced stress, including effects on individuals and populations, including possible synergistic effects (by which increased noise-induced stress may make animals more susceptible to other physical infections and difficulties).

Mitigation Measures and Management of Noise

In considering current practices for managing noise, the Committee addressed several related topics. Most contentious was the level of precaution or conservative assumptions that is appropriate in setting noise limits, safety zones, and the like. Equally important, fostering less disagreement, was the permitting system.

Precautionary/Conservative/Protective Management

There is a tension between groups around the need to formally adopt a "precautionary" approach. Much of this appears to be a semantic argument, though an underlying tension over how aggressively to respond to uncertainty is also in play. It is my impression from the statements that the Federal Caucus (and likely the Scientific Research Caucus, which did not address this issue so directly) believe that current management and mitigation is sufficiently conservative, while the Environmental Caucus favors more stringent controls on noise (or at least more targeted controls, aimed at biological "hot spots"), and the Energy Producers Caucus considers current management practices to be bordering on excessive. It is likely that this was a topic that was especially hard to find consensus on.

Energy Producers favored a "balanced protective approach" and said that "based upon our understanding of the risks, we believe that current management systems are effective, recognizing that future improvements may be warranted," while also stressing that "regulators should not be repeatedly inserting caution intended to mitigate risk into their judgments and assumptions" and stipulated that such insertions of caution into the management process should be made only one time, "and it should be fully documented."

Federal Caucus stressed that the "best available scientific Information" standard that is common in statutory language does not require certainty, and that, given our current uncertainties about effects of sound and in assessing impacts, "it is appropriate for managers to conservatively manage sound producing activities," while favoring a focus on adaptive management, with flexibility to re-evaluate and refine management practices as we learn more, over a stated "precautionary" standard.

The Environmental Caucus suggested that rising background noise, slow reproductive rate of many whale species, poor precision of our population estimates, and general uncertainties in marine mammal science, "necessitates precautionary management and protective mitigation measure to prevent or reduce harm today--before the proliferation of man-made noise sources in the world's oceans becomes intractable and impacts irreversible."


The Federal Caucus noted that "Increasing application requests, public interest, and controversy is generating an increased burden on the Services to process the applications and comply with ESA and NEPA requirements. The Services’ staff and resources for analyzing and processing these applications are limited and the current demand exceeds their capacity." They also cited a pressing need for "more effective, efficient, and transparent management," and stressed the need for better information on the effectiveness of current mitigation measures.

The Federal, Energy Producers, and Environmental Caucuses noted that not all sound-producing activities are currently regulated. Commercial shipping, recreational boating, whale-watching, acoustic alarms on aquaculture facilities, ice-breaking, and sound sources on commercial fishing boats are among the sound sources that receive very little scrutiny. (This is largely because current regulatory measures primarily address effects caused by exposure to extremely loud--potentially physically harmful--sound sources, rather than addressing chronic, moderate noise exposure.)

The Scientific Research Caucus seconded a recommendation made by the Commission on Ocean Policy that the Marine Mammal Protection Act should be amended so that minor, individual behavioral changes are not considered harassment requiring special "small takes" permits.

This request is in part spurred by frustration among scientists about the difficulty of obtaining permits to conduct research aimed at addressing many of the unanswered questions about the effects of noise on ocean life (this concern is shared by some in the oil and gas industry and environmental community, who each suspect the answers will bolster their arguments). Thanks in part to language in the National Environmental Policy Act, which triggers the call for more involved reviews of proposed activities if they are "controversial," and to closer scrutiny and involvement in the permit process by animal rights and environmental advocates, permit applications and agency findings have become much more complicated in recent years. Of course, the growing body of research that examines noise impacts has also raised many questions that need to be addressed by permitees and agency personnel. To help alleviate the burdens of the permit process, several ideas are being explored. The California Coastal Commission statement contains the most detailed summary of possible solutions, including:

  • additional funding for agencies evaluating applications and issuing permits
  • development of standard background documents and references that can be used when submitting applications and evaluating risks (this appears to be taking place on the agency side of the equation, as evidenced by similar language and references in many agency notices regarding academic and industrial seismic surveys).
  • create mechanisms by which permits can be collectively processed and issued, when they affect similar species, regions, or activities
  • expand use of programmatic environmental assessments and impact statements to streamline approval of multiple projects that pursue similar activities (this is also underway, as NOAA Fisheries is doing a Programmatic Environmental Impact Statement covering academic seismic surveys in general).

Note: Some of the most contentious research permits have involved studies that introduce new sound sources into the seas. The highest profile controversies have involved a high-frequency "whale finder" sonar that might help sonar and airgun operators discover nearby whales that are not vocalizing or at the surface, and Controlled Exposure Experiments, which involve carefully monitoring whale responses to a noise source, most commonly an airgun array, that is controlled by the research team. Scientists tend to consider the noise they are introducing to be a negligible addition, applied in moderation, but some environmental advocates have challenged these assumptions, and the permits that agreed, in court.

Commercial Shipping

The Commercial Shipping Representative submitted a statement which indicated a willingness to work toward better understanding of the effects of shipping noise on marine ecosystems, and to pursue ship quieting, especially if such an initiative is implemented in a gradual way that includes the shipping industry in its development. It encouraged the involvement of naval architects and ship engineers, as well as global experts in ship routing and maritime trade, in order to identify current maritime traffic densities around the world. The statement also encouraged the United States to take a lead in the International Maritime Organization (a UN subsidiary that regulates international shipping), to encourage the IMO to address the impacts of shipping noise on ocean ecosystems.

The Federal Caucus noted that the MMS and NMFS are engaged in an ongoing dialogue with the Coast Guard, Navy, and other Federal agencies to address shipping noise and ship quieting. They expect that Naval architects will be sharing expertise with private industry representatives and designers, and that the development of voluntary guidelines for ship quieting may result.

Best Practices

One goal of the consensus process was to come to some agreement about a set of "best practices" that could become the common toolbox from which to design operational procedures for research, oil and gas exploration, and naval activities. The Caucus statements each tossed ideas into the hat, though the lack of consensus makes it difficult to assess which ones have widespread acceptance.

The Environmental Caucus suggested that avoiding sensitive areas is probably the most effective means available of reducing the impacts of ocean noise and should become the backbone of management. They favored geographic and seasonal exclusions of noise sources in key breeding, feeding, calving, or migratory habitats, and designation of marine reserves, including routing ship traffic away from them. They also urged reduction of noise producing activities (eg, sharing seismic data so as to limit duplication), and source modification (ship quieting, engineering advances to limit frequency spectrum of airguns, use of seafloor marine vibrators, etc.).

The Federal Caucus addressed many mitigation and operational options, including the ones listed above. They noted that geographic and seasonal restrictions, especially if they take into account slight annual variations, would require a level of flexibility that may be difficult for permitees to adapt to.

The Energy Producers Caucus noted that mitigation should take into account the level of risk as well as the proven benefits. Some mitigation may not be warranted due to limited risk or unlikely benefit; and some may have "unreasonable cost and operational impacts."

Research Priorities

While there is widespread agreement about the need for expanded research into the extent and effects of noise in the sea, and better evaluation of the effectiveness of current mitigation measures, many of the caucus statements stressed particular research priorities not mentioned in others. Taken together, the suggestions offer a good overview of the range of knowledge that would be useful, while also offering a sense of the difficult decisions to be made about what to prioritize.

The Environmental Caucus encouraged:

  • Identification of areas with greater and lesser concentrations of marine life, so as to limit noise in the former and be more permissive in the latter.
  • Measurement of stress hormones and hearing in noisy and quiet areas, to confirm whether chronic noise increases stress or damages hearing.
  • Research into more effective mitigation tools (eg improved passive acoustic monitoring) and engineering modifications to reduce source levels of noise sources (use of seafloor seismic vibrator sources, more sensitive hydrophones, increased directionality of sonars, etc.).
  • Use of ongoing noise sources (rather than noise introduced by researchers) to study individual animals' response to noise, and long-term, systematic study of individuals so as to get a better sense of possible population-level impacts.

Federal Caucus recommended:

  • Development of new techniques to measure and model the cumulative effects of repeated acoustic exposure on individuals and on ecosystems, including both discrete sound sources and their interaction with chronic ambient noise increases.
  • More focus on chronic moderate noise, and the possible effects of masking.
  • Development of ship quieting technologies, including integration of Naval advances into commercial ship-building.
  • Education of the public about the risks of anthropogenic noise, how to reduce adverse effects, and increasing cooperation among all stakeholders.

Scientific Research Caucus urged:

  • Validation of untested assumptions being used in mitigation measures (e.g.: do observers identify whales effectively? do marine mammals avoid sound sources at distances large enough to avoid injury?)
  • Better risk-assessment approaches, so as to be able to direct our efforts toward activities that are more likely to have population-level impacts.
  • Development of models to quantify individual behavioral responses into measures of likely population-level impacts (following on the work of the NRC 2005 report that sketched out a Population Consequences of Acoustic Disturbance (PCAD) model that moves toward regulating "takes" based on Potential Biological Removal (PBR), broadened to include behavioral impacts).
  • Initiating a coordinated national research program by convening a national workshop charged with converting the research recommendations of the NRC reports on ocean noise (which since 1994 have been making many of the same recommendations as this Committee) into a research strategy and implementation plan.
  • Studies of the hazards caused by currently unregulated sound sources, such as shipping and private boating.
  • Studies of the impacts of high-frequency sound, such as used to keep marine mammals away from fish farms or nets.
  • Design networks of acoustic sensors to monitor ambient noise levels and trends on global, regional, and local scales
  • Survey population levels of marine mammals worldwide so as to better assess likely exposure to sound

Note: while the need to better understand effects of chronic moderate level noise was stressed in the beginning of the Scientific Research Caucus' report, its research recommendations gave this little attention.

Energy Producers Caucus stressed that "in establishing priorities and allocating resources, policy makers must assess risks and benefits and consider all relevant factors in making balanced decisions. Hence, anthropogenic sound must be evaluated in the context of other anthropogenic threats to marine mammals, such as fishing by-catch, ocean pollution, habitat degradation, harmful algal blooms, whaling, vessel/whale collisions, and whale watching. Any biologically-significant adverse effects caused by anthropogenic sound must be examined in the context of other known causes of marine mammal disruption and mortality. And perhaps most important, research, management and mitigation activities must be focused on the most likely areas for potential risks of adverse effects of sound, not simply on sound itself."

The California Coastal Commission urged the adoption of standardized reporting procedures for currently required monitoring of marine mammal activity during permitted activities. They suggested that observations made during oil and gas industry, academic, and naval activities could, if standardized, provide valuable data for systematic statistical analysis of behavioral responses to noise; thus the funds expended in mitigation could have multiple benefits by providing answers to pressing questions, saving limited research dollars, and perhaps reducing the need for studies that involve making sound solely for the purpose of seeing how animals react.

Other issues

A number of issues appear in the Caucus statements of only one of the groups. It is possible that some of these issues were roadblocks to consensus, if a group insisted on their inclusion or if a group or two resisted including items on which the rest of the members either agreed or were willing to include.

The Energy Producers Caucus stressed that noise is likely to be a much smaller population-level threat than many other threats; they specifically cited figures suggesting that fishing by-catch kills over 300,0000 marine mammals annually, many orders of magnitude more than are killed outright by sound. While supporting additional research, they expressed concern about a rush to study noise, suggesting that spending priorities should take into account the relative threat of noise, as compared to other issues.

The Environmental Caucus (and the California Coastal Commission) raised questions about the sources of funding for ocean noise research which were apparently not a concern of other groups. Specifically, they were concerned that, if the Navy is the primary source of funding, researchers will be more likely to report results in keeping with a perceived Navy need to make noise with minimal restrictions. As a possible solution to this issue, they suggested that the Fish and Wildlife Foundation oversee funding through its National Whale Conservation Fund; the California Coastal Commission also suggested the National Oceanographic Partnership Program as a more independent umbrella for research.

The Environmental Caucus also urged extreme caution in the use of Controlled Exposure Experiments, which are becoming a primary research technique to examine the responses of marine mammals to noise. CEEs involve putting temporary tags on individual animal, which record the received levels of sound and the diving patterns, while approaching the animals with a sound source, such as an airgun array. Two concerns were raised: that this technique adds more sound to an already noisy sea, and that there are ethical questions about deliberately exposing animals to additional stress, even temporarily. A similar ethical and biological concern was raised about the stress imposed by Auditory Brainstem Response (ABR) measurements on live, stranded animals (ABR uses passive electric measurements to record an animal's response to sound tones, and is the best, and practially only, way to learn more about the hearing sensitivity of species not kept in captivity).

Straw Men?

The Energy Producers Caucus seemed rather susceptible to a tendency to erect straw-man arguments to knock down. For example, their statement put forth the tenet that "to take the position that no individual marine mammal can ever be affected by anthropogenic sound is to effectively decree that all human activity in the oceans cease." Few, if any, participants on ocean management, and certainly no members of the Advisory Committee, have suggested a "no individuals ever affected" threshold for management of sound. Similarly, they claim that "some seek to oversimplify the sound issue and use a handful of stranding reports for which no causative factors have been conclusively identified as the basis to jump to a conclusion of significant global harm. We believe this is counterproductive to serious work and inquiry into the issue by marine mammal scientists who focus on science rather than advocacy." Again, while some members of the public may make such simple leaps from very limited information, this sort of rhetorical hyperbole is likely to be counterproductive to the obviously much higher level of dialogue taking place within the Advisory Committee; certainly the arguments made by those Advisory Committee members advocating for more concern about noise are based on wide-ranging formal research studies, not on a few strandings coincident with noise events. Finally, they suggest that "regulatory agencies should avoid layering caution and more caution on conservative judgments and assumptions." While they may be taking exception to what they perceive to be unnecessary monitoring or mitigation requirements (or they may be fearful of future constraints), the fact is that, to date, agencies have not markedly increased the burden on energy producers (though academic seismic surveys and the Navy have seen more significant mitigation requirements in the past couple years).

The Environmental Caucus concern about sources of funding could be similarly misplaced. They provide no examples of skewed research reporting, and ignore the fact that some researchers long funded by military and industrial sources have been among those whose work and public statements have raised awareness of the need for closer scrutiny of ocean noise (eg, John Hildebrand, Christopher Clark, Robert McCauley).

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