The deep, dark ocean is often thought of as a peaceful, silent world. However, it is an orchestra of sounds, like the snapping of shrimp, the clicks of dolphins and the songs of whales.
New science suggests that in many places, though, human activity may be drowning out those noises — and having a disorienting and destructive impact on marine animals.
“Scientists have been warning about this for a long time,” said Heidrun Frisch-Nwakanma, who leads underwater noise work at the Convention on the Conservation of Migratory Species of Wild Animals (CMS).
“Virtually everything we humans do in the coastal or marine environment creates noise, and such activities are increasing.”
Her warning came just ahead of International Noise Awareness Day, on 27 April 2022, which casts a spotlight on the harmful effects of loud noises.
Marine creatures may be especially susceptible to those sounds. Many use echolocation—which relies on reflected sounds to pinpoint objects—to find prey, communicate, locate mates and offspring, and navigate the vast and interconnected ocean. For example, dolphins and porpoises use high-resolution, high-frequency, underwater biosonar to target prey and navigate while breeding baleen whales communicate using complex songs transmitted at a low frequency over a considerable distance.
We need to urgently build our understanding of how to restore a healthy ocean from visible threats such as marine litter as well as invisible threats including noise pollution.
Getting louder
Since the Industrial Revolution, the the oceans have been flooded with noise from commercial shipping, geophysical surveys, low-flying planes, oil drilling, offshore wind turbines, dynamite fishing, submarines, dredging, military exercises, the destruction of unexploded artillery, sea bed mining, infrastructure development, and sonar navigation systems.
While the science is still new, some experts are raising the alarm about the disruptive consequences of such underwater noise to invertebrates, sea turtles, sharks, dolphins and whales.
A 2021 study published in the journal Science shows that shipping has contributed to an estimated 32-fold increase in low-frequency noise along major shipping routes in the past 50 years. Additionally, noise from sonar has been linked to the stranding of whales ashore.
“While we have some evidence of the detrimental effects of noise pollution, as with much of the science related to understanding life below water, we know far too little to push for changes in policy and practice adequately,” says Leticia Carvalho, Head of the United Nations Environment Programme’s (UNEP) Marine and Freshwater Branch. “We need to urgently build our understanding of how to restore a healthy ocean from visible threats, such as marine litter, and invisible threats, including noise pollution.”
Increasing awareness
Over the last decade, more attention has been paid to marine noise pollution in international frameworks such as CMS, the Regional Seas Conventions, the Convention on Biological Diversity, the International Maritime Organization, and even the UN General Assembly. Specialised working groups are developing solutions to reduce noise from human activities. Some strategies include better maintaining ships, optimising propeller designs and lowering the speeds of vessels. Others focus on underwater oil drilling, dynamite fishing, dredging, and military exercises. Experts say that nature can rebound relatively quickly in areas where noises are reduced.
“At the national level, the first step is to get a realistic picture of the potential noise-related impacts of any activity or project,” said Frisch-Nwakanma, who was part of the team behind the development of global guidelines to manage marine noise.
CMS, an environmental treaty of the United Nations, develops guidelines for Environmental Impact Assessments that can help with that process. They detail which data are needed to gauge the impact of underwater noise pollution. Those assessments often require international cooperation, especially on the high seas, she said.
The climate crisis
Climate change can make noise pollution in the ocean worse, says Frisch-Nwakanma. For instance, melting sea ice opens up previously inaccessible regions to shipping, drilling, and other human activities.
Research also shows that climate change and other human pressures have also led to the deterioration of habitats, such as coral reefs, seagrass meadows and seagrass beds, silencing characteristic sounds that guide fish larvae and other animals to find their habitats. The whoops and growls of healthy coral reefs—teeming with various fish and other organisms—are similar to the sound of food frying.
Noise pollution isn’t restricted to the oceans. The latest edition of the UNEP’s Frontiers report, Noise, Blazes and Mismatches: Emerging Issues of Environmental Concern, shows it is a growing hazard to public health and wildlife in cities. Unwanted, prolonged and high-level sounds from cars and trains have been known to interfere with the communications of birds, insects, and amphibians.
Last year marked the launch of the UN Decade of Ocean Science for Sustainable Development. Running through 2030, the Decade is the ideal opportunity for countries to devote more resources to understanding the impacts of marine noise pollution, says Carvalho.
