Among warnings of coral bleaching events, plastic gyres and oil spills the possible impacts of noise pollution caused by shipping traffic is not high on the list of marine priorities. In spite of the many studies identifying areas of concern, it can be difficult to oppose shipping routes seen as necessary in a globalised market.
However, a new study proposes quiet ‘opportunity areas’ such as Haida Gwaii off the coast of British Colombia, which could help researchers fully understand the impacts of sound pollution on marine ecosytems and how to protect them. It focused on large marine mammals such as elephant seals, steller sea lions, fin whales, humpback whales and common minke whales.
‘For these species, clearly chemical pollution, entanglement in debris and fishing gear and intended cullings are higher risks in some areas,’ says Christine Erbe, Director of the Marine Science Center at Curtin University and co-author of the study. ‘But in others, marine noise seems to be important and on the rise.’
In the ocean, sound penetrates further than light, travelling hundreds of kilometres versus tens of metres. It is known to be the only mode of communication that allows for interactions over greater distances than a few body lengths. Dr Rob Williams, conservation scientist and lead author of the research, says ‘for many species of whales, dolphins and porpoise, sound as is as important as vision is to humans’. While the full impact of human-caused noise is not yet known, scientists speculate that it can interfere with marine mammal communication, hunting behaviour and cause hearing loss.
‘Because sound travels much faster, further and at much less loss underwater than light does, marine animals have evolved a strong acoustic sense for sensing their environment and for communication,’ he says.
Shipping has increased by 300 per cent since 1992, allowing for a crescendo in the noise around ports and busy routes. The northern hemisphere is notoriously noisy, given the constant back and forth of goods between North America, Europe and Asia. Identifying areas in the northern hemisphere that are already quiet and keeping them that way may come at a lower economic cost than trying to reduce the noise of louder areas, the study says.
‘We tend to focus on problems in conservation biology,’ says Williams. ‘This was a fun study to work on, because we looked for opportunities to protect species by working with existing patterns in noise and animal distribution.’
Compared to many busy coastlines in the northern hemisphere, Canada still has pockets of what Williams calls ‘acoustic wilderness’, which he says should be considered a rich natural resource. The species-rich waters of Haida Gwaii, an archipelago on the north coast of British Columbia, is one example of an ideal opportunity area. As an area with high species diversity and low noise pollution, Haida Gwaii could be used as a noise-free control site to compare other noisier areas with.
In previous years, policy-makers have only considered ocean noise when acute, very loud sound sources are perceived to cause dramatic effects, such as whale strandings following military exercises involving naval sonar. ‘However, many jurisdictions, including Canada, the US and the EU, are now beginning to incorporate the chronic effects of lower-level noise from shipping and other human activities that have become ubiquitous in today’s increasingly industrialised oceans,’ says Williams.
‘We must make every effort to protect quiet ocean regions now,’ says Dr. Christopher Clark from the Bioacoustics Research Program at Cornell University, ‘before they grow too noisy from the din of our activities.’