TOWARDS QUIETER SEAS: A REVIEW OF ANTHROPOGENIC NOISE AND RECOMMENDATIONS FOR REDUCING ITS IMPACTS ON CETACEANS

I became aware of WDC’s quest early in my research career over three decades ago. Then known as WDCS, this energetic charity was championing better awareness and conservation of the world’s cetaceans. They were looking for scientifically rigorous information on the lives of the wild dolphins that I was studying for their adopt-a-dolphin programme. Through the years, WDC has kept up their conservation pursuits and in this report are turning their passion and influence towards the global threat coming from humans’ injection of polluting underwater noise into the world’s ocean and seas.

It has long been known that underwater sound is important for whales, dolphins and porpoises and as we have learnt more about them, the importance and fragility of their hearing and sophisticated use of sound have become ever more apparent. In recent years, the concept of soundscapes has risen to the fore, with the realisation that the sounds animals, such as cetaceans, produce and listen to are intricately tuned around the other natural sounds that exist in their habitats. From waves, rain and earthquakes to the grunts, moans, clicks and buzzes of all the other soniferous inhabitants, cetaceans evolved so that they could hear one another’s calls and also the pertinent sounds and even the echoes coming from their prey.

Unfortunately, much of what we’ve learnt about cetacean sonic capabilities and these intricate relationships has come about because of urgent concerns that our human activities on, under, above and beside the marine environment can be noisy, often extremely, harmfully noisy. Prospectors searching for oil and gas below the seabed, for example, routinely use devices known as airguns to make intense sounds loud enough to reverberate across entire sea basins. Military ships use high power sonar to search for submarines. The myriad cargo ships, tankers and ferries plying their way from one port to another fill the sea with the noise from their engines and propellors. For these activities, impacts on the acoustic worlds of cetaceans and other marine life are collateral damage. For other activities, marine life is the specific target. Devices like Acoustic Deterrent Devices are intended to keep sensitive wildlife away from human interests at sea. Perhaps a good thing in the short term for some species in terms of avoiding their injury from something we are doing, but ultimately these noises also add to the cacophony of all our activities in what is otherwise known as the Blue Economy. In addition to these established and widespread sound sources, new sounds are entering the mix as we, the human race, march into technologically sophisticated, lower carbon futures. Removing outdated oil and gas infrastructure requires cutting, blasting and huge vessels to carry away the debris. Most offshore wind turbines are fixed with one or many massive steel pins hammered into the seabed which may require clearance of unexploded bombs from previous wars. Other sea-based industries are on the cusp of becoming widespread. Coastal seas may offer real estate for launching and retrieving space rockets with all the associated blast-off and splash-down noises (and greenhouse gas emissions) that propelling rockets skyward entails. In the deep sea, a new industry poised to take shape far from shore in the global search of rare-earth minerals, is deep-sea mining. As well as being highly controversial for deep sea ecology on environmental grounds, scraping, lifting and transporting these resources will add new noise pollution to previously relatively pristine far offshore cetacean habitats.

I am delighted to see this forward-looking WDC report which summarises the background of what we now know about the many widespread and long-term sources of anthropogenic noise in coastal and offshore waters. The perspective is global but with a UK-centric viewpoint particularly around policy and regulation. As much as it outlines the basics of what we do know, it avoids getting lost in the intricacies of a very complex and evolving scientific field but does pay particular attention to crucially what isn’t known yet and needs to be understood. A large area of uncertainty receiving fresh attention is how the impacts of all these noise sources in aggregate come together to have cumulative impacts that may have effects on individual cetaceans or at the scale of entire populations.

From this overall summary, we are left in no doubt that that the sound energy we inadvertently, and sometimes deliberately, put into the ocean and seas is pollution. It’s impacts on cetaceans are becoming better known and ever more concerning but one good thing about noise (unlike chemicals, plastic or heat) is that the moment we stop making the sound, as a pollutant it’s gone. Moreover, if we pay attention, it is possible to engineer these activities to make less sound or bleed less energy into the water or can be tuned away from the most harmful frequencies. So, there is hope and, in this report, fresh eyes are cast on global efforts to improve the current situation. In particular, UK legislation, management practices and mitigations are considered. I am especially pleased to see that this report provides clear, actionable recommendations for regulators, industry, researchers and NGOs to improve the protection of cetaceans from underwater noise. In doing so, this report further continues WDC’s quest to champion better awareness and conservation of the world’s cetaceans from the threats they face in modern seas.