March 01, 2015

Effects of sound on marine mammals: Acoustic permitting of ocean activities

Julia Wyman

The oceans are busy, loud places. They are filled with natural and human activities and natural and human sounds. Many marine mammals rely on hearing for multiple reasons, including:

  • finding food,
  • locating and selecting mates,
  • avoiding predators,
  • navigation, and
  • group structure.

Marine mammals are able to communicate underwater across a variety of distances using sound. Human-created sounds can cause disruption to marine mammals through acute impacts, such as an intense noise event that has adverse physical and behavioral impacts affecting health and fitness of the mammal. Human-created sounds can also cause disruption through chronic impacts, where rising background noises limit the mammals’ abilities to communicate and sense their environments. As human uses of the oceans increase and human noise impacts increase, it is becoming increasingly important to monitor and regulate the impact of human noise on marine mammals. To help practitioners identify pertinent legal authorities, this article will briefly discuss several key federal statutes related to acoustic impacts on marine mammals:

  • Marine Mammal Protection Act (MMPA)
  • National Environmental Policy Act (NEPA)
  • Environmental Species Act (ESA)
  • National Marine Sanctuaries Act (NMSA)

Marine Mammal Protection Act

The MMPA recognizes the importance of marine mammals to marine ecosystems and acknowledges that human activities may deplete or extirpate marine mammal species or population stocks. The MMPA’s primary objective is to maintain the health and stability of marine mammals and their marine ecosystems. To do this, the MMPA prohibits the “taking” of marine mammals unless the taking is exempted, authorized, or permitted. The MMPA does allow for the incidental taking of marine mammals within a specified geographical area during otherwise lawful activities, provided the Secretary of Commerce finds that the taking

  • will have a negligible impact on such species or stock and
  • will not have an unmitigatable adverse impact of the availability of species or stock for subsistence uses.

The MMPA requires that permissible methods of taking will have the least practicable impact on species or stock, paying particular attention to rookeries, mating grounds, and areas of similar significance. Activities that have caused incidental takes and that the Secretary of Commerce has deemed permissible under the MMPA include

  • oil and gas exploration,
  • military training and testing,
  • port and highway bridge construction,
  • scientific research, and
  • offshore alternative energy development.

To better assess the impact of human activities on marine mammals, the National Oceanic and Atmospheric Administration (NOAA), the agency responsible for issuing MMPA permits, is in the process of developing “acoustic guidance for assessing the effects of anthropogenic sound on marine mammal species.” The guidance will help “NOAA analysts/managers and other relevant user groups/stakeholders, including other federal agencies[,] to better predict a marine mammal’s response to sound exposure in a manner that has the potential to trigger certain requirements under one or more of NOAA’s statutes,” such as the MMPA, ESA, or NMSA. NOAA’s guidance should help the government better understand and monitor chronic impacts of human noise on marine mammals.

National Environmental Policy Act

Issuance of an MMPA permit triggers analysis under several other environmental statutes. For example, NEPA requires that federal agencies must analyze the impacts of their proposed activities and potential alternatives to those activities. The agency must make this analysis, in the form of an environmental assessment or an environmental impact statement, available to the public and to agency decision makers.

Endangered Species Act

A proposed action must also take into consideration the ESA, which requires federal agencies to ensure that their actions do not jeopardize the continued existence of any threatened or endangered species or result in the destruction or adverse modification of their critical habitat. The Secretary of Commerce may require the applicant to conduct a biological assessment of the species in question, which may be included as part of the NEPA assessment.

National Marine Sanctuaries Act

Similarly, under the NMSA, federal agencies must provide the Secretary of Commerce with a description of any activity that may cause the loss of, or injury to, any resource located in one of the nation’s 13 national marine sanctuaries.

Coastal Zone Management Act

It is important to note that many human activities causing acoustic impacts take place in state waters or have impacts on state coastal resources. Under the consistency provision of the Coastal Zone Management Act (CZMA) (16 U.S.C. § 1456(a)(1)(A)), states have the authority to request that federal activities affecting “any land or water use or natural resource of the coastal zone” be carried out “in a manner which is consistent to the maximum extent practicable with the enforceable policies of approved State management programs.” These state programs can vary widely. Careful practitioners should be familiar with the CZMA and the provisions of approved state coastal management plans (CMPs) and consider whether proposed activities could potentially impact state coastal resources, including marine mammals.

As ocean activities continue to multiply, the protection of marine mammals will become an even greater challenge. Those undertaking such activities should evaluate both acute and chronic impacts. The best available science on acoustic impacts to marine mammals will be critical in evaluating these impacts.

Julia Wyman


Julia Wyman is the interim director of the Marine Affairs Institute/Rhode Island Sea Grant Legal Program and adjunct professor of law at the Roger Williams University School of Law.