Oceans have become substantially noisier since the Industrial Revolution. Shipping, resource exploration, and infrastructure development have increased the anthrophony (sounds generated by human activities), whereas the biophony (sounds of biological origin) has been reduced by hunting, fishing, and habitat degradation. Climate change is affecting geophony (abiotic, natural sounds). Existing evidence shows that anthrophony affects marine animals at multiple levels, including their behavior, physiology, and, in extreme cases, survival. This should prompt management actions to deploy existing solutions to reduce noise levels in the ocean, thereby allowing marine animals to reestablish their use of ocean sound as a central ecological trait in a healthy ocean.
Sound is the sensory cue that travels farthest through the ocean and is used by marine animals, ranging from invertebrates to great whales, to interpret and explore the marine environment and to interact within and among species. Ocean soundscapes are rapidly changing because of massive declines in the abundance of sound-producing animals, increases in anthropogenic noise, and altered contributions of geophysical sources, such as sea ice and storms, owing to climate change. As a result, the soundscape of the Anthropocene ocean is fundamentally different from that of preindustrial times, with anthropogenic noise negatively impacting marine life.
We find evidence that anthropogenic noise negatively affects marine animals. Strong evidence for such impacts is available for marine mammals, and some studies also find impacts for fishes and invertebrates, marine birds, and reptiles. Noise from vessels, active sonar, synthetic sounds (artificial tones and white noise), and acoustic deterrent devices are all found to affect marine animals, as are noise from energy and construction infrastructure and seismic surveys. Although there is clear evidence that noise compromises hearing ability and induces physiological and behavioral changes in marine animals, there is lower confidence that anthropogenic noise increases the mortality of marine animals and the settlement of their larvae.
Anthropogenic noise is a stressor for marine animals. Thus, we call for it to be included in assessments of cumulative pressures on marine ecosystems. Compared with other stressors that are persistent in the environment, such as carbon dioxide emitted to the atmosphere or persistent organic pollutants delivered to marine ecosystems, anthropogenic noise is typically a point-source pollutant, the effects of which decline swiftly once sources are removed. The evidence summarized here encourages national and international policies to become more ambitious in regulating and deploying existing technological solutions to mitigate marine noise and improve the human stewardship of ocean soundscapes to maintain a healthy ocean. We provide a range of solutions that may help, supported by appropriate managerial and policy frameworks that may help to mitigate impacts on marine animals derived from anthropogenic noise and perturbations of soundscapes.