Since the (first) Industrial Revolution, the soundscape of the ocean has been undergoing a drastic revolution too. No longer do whale calls or pounding surf dominate – instead, sounds generated by human activity ring through the water, from fishing, shipping and resource exploration, to infrastructure development and more.
An international team of scientists has now released the biggest review of marine noise pollution yet, finding significant evidence that anthropogenic noise is affecting marine wildlife, from whales to invertebrates, as well as their ecosystems.
They document how human-generated noise disrupts animals’ behaviour, physiology and reproduction, and in extreme cases even causes death.
The study is published in Science.
Anthropo-sound is a problem that’s long been “ignored in the assessment of ocean health informing global policy initiatives,” says lead researcher Carlos M. Duante, from King Abdullah University of Science and Technology (KAUST), in Saudia Arabia. “The reason is that the evidence, which is abundant and compelling, was scattered across a large body of literature that had never synthesised.”
To combat this, the team delved into more than 10,000 scientific studies from the past 40 years, to assess and collate data from around the world.
Co-author Michelle Havlik, also from KAUST, says that this unprecedented effort “has shown the overwhelming evidence for the prevalence of impacts from human-induced noise on marine animals, to the point that the urgency of taking action can no longer be ignored”.
Sound travels fast and far underwater, meaning that the surface is acoustically connected to the deeper ocean. Most marine animals use sound for navigation and communication, so disrupting the natural soundscape takes its toll.
Intriguingly, the research revealed that humans don’t just make the oceans noisier and drown out natural sounds – in some areas we actually make the oceans quieter. This is often the result of the destruction of habitat – such as coral reefs, seagrass meadows or kelp beds – due to the warming water temperatures and other human pressures, or the hunting of large marine mammals like whales.
This silence also negatively impacts marine critters. Duante explains that animals such as invertebrates and fish begin their lives as eggs and larvae, drifting in the surface layers of the ocean, and they use sound to navigate to their adult habitats.
“Failing to settle in the right habitat leads to mortality,” he says. “Habitat loss and degradation have rendered the ‘call from home’ – ie, the soundscape of healthy habitats directing wandering juveniles to settle on their right habitat – to be silenced.”
The accelerating loss of sea ice due to our rapidly changing climate has also altered the natural acoustics of Arctic marine environments, with increasing sounds from ice cracking and bergs calving. Even the weather conditions change soundscapes. In the tropics, the study finds, climate change may increase surface sounds due to increased winds, rainfall and waves from tropical storms.
The researchers even note that greenhouse gas emissions can change sound propagation in the ocean due to increasing acidification.
But Duante explains that there’s still much we don’t understand.
“Multiple questions remain unanswered, including impacts on marine reptiles such as sea turtles, and seabirds,” he explains – because very few studies exist for these species.
“We have no understanding [about] the role sound plays on their ecology and to what extent they may be vulnerable to noise derived from human activities.”
“Changing ocean soundscapes have become the neglected ‘elephant in the room’ of global ocean change,” the authors write in their paper. “In an era when societies increasingly look to the blue economy as a source of resources and wealth, it is essential that ocean soundscapes be responsibly managed to ensure the sustainable use of the ocean.”