Professor Steve Simpson in Blue Planet II - credit Roger Munns

Healthy oceans need healthy soundscapes

Oceans were once filled with the sounds of nature, but overfishing, climate change and human noise have fundamentally changed the natural underwater "soundtrack", researchers say.

A global team of scientists, including six experts from three UK institutions, has documented how ocean soundscapes have changed, explored all impacts of noise on marine animals and ecosystems, and identified ways to restore a more natural soundscape.

The team set out to understand how human-made noise affects wildlife, from invertebrates to whales, and found overwhelming evidence of negative impacts on behaviour, physiology and reproduction – causing death in extreme cases.

They call for this issue to be considered a global threat to marine ecosystems, and for policy to be developed to limit its effects.

The review, led by Professor Carlos Duarte at the King Abdullah University of Science and Technology (KAUST), and published in the journal Science, shines a light on the global impacts of ocean noise.

“Since the Industrial Revolution, humans have made the planet, the oceans in particular, noisier through fishing, shipping, infrastructure development and more, while also silencing the sounds from marine animals that dominated the pristine ocean," Professor Duarte said.

Professor Steve Simpson, of the University of Exeter, said: “Many marine habitats are under threat from increased cyclones, ocean warming, overfishing and pollution, devastating the communities of animals that generate natural soundscapes, and robbing future generations of marine animals of the cues they use to find and select suitable places to live.

"The call of home is no longer audible to fish, crabs, clams and corals in many ecosystems.”

Today's marine environment, according to the researchers, is polluted by man-made acoustic phenomena, and should therefore be restored along "sonic dimensions", as well as along more traditional chemical and climatic ones.

However, current frameworks to improve ocean health ignore the need to mitigate noise as a pre-requisite for a healthy ocean.

Sound travels far, and quickly, underwater – and marine animals are sensitive to sound, which they use to inform many aspects of their behaviour and ecology.

“The ocean soundscape is one of the most important sources of information for marine animals,” explains Professor Andy Radford, of the University of Bristol.

“So we hope that our study will prompt management actions to reduce man-made noise levels in the ocean, thereby allowing marine animals to re-establish full use of their acoustic world.”

Dr Harry Harding, also of the University of Bristol, added: “We assessed the evidence contained in more than 10,000 papers to amass compelling evidence that man-made noise impacts marine life, from plankton to whales, in a whole suite of ways spanning physiology and behaviour to survival and reproduction.”

Dr Lucille Chapuis, of the University of Exeter, said: “This unprecedented effort, bringing together an international coalition of the willing from across the marine acoustics community, showcases overwhelming evidence for the prevalence of impacts of human-induced noise on marine animals, highlighting the need for taking urgent action."

The collaboration involved 25 scientists from Saudi Arabia, UK, Netherlands, Germany, Spain, Denmark, Norway, USA, Canada, Australia and New Zealand.

“The deep, dark ocean is conceived as a distant, remote ecosystem, even by marine scientists,” Professor Duarte said

“However, as I was listening, years ago, to a hydrophone recording acquired 1km underwater off the US West Coast, I was surprised to hear the clear sound of rain falling on the surface as the dominant sound in the deep-sea ocean environment.

"I then realised how acoustically connected the ocean surface, where most human noise is generated, is to the deep sea; just 1,000 m, less than one second apart!"

Dr Nathan Merchant, of the Centre for Environment, Fisheries and Aquaculture Science, said: "In this comprehensive review, we demonstrate that to recover the health of the world’s oceans, we need to turn down the volume on human noise pollution.

“Our study identifies relatively easy ways to achieve this, from modifying ship propellers to using bubble curtains when building offshore windfarms.

"Policymakers can implement these measures by setting binding targets and providing economic incentives.”

Dr Tim Gordon, of the University of Exeter, added: “Deploying these mitigation actions is a low-hanging fruit as – unlike many other forms of human pollution, such as emissions of chemical pollutants and greenhouse gases – the effects of noise pollution cease upon reducing the noise, so the benefits are immediate.”

The study points at the rapid response of marine animals to the human lockdown under COVID-19 as evidence for the potential rapid recovery from noise pollution.

Using sounds gathered from around the globe, multimedia artist, and co-author of the study, Jana Winderen created a six-minute audio track that demonstrates both the peaceful calm, and the devastatingly jarring, acoustic aspects of life for marine animals.

Date: 4 February 2021