By Becca Payling
When we think of pollution, we think of smog-filled cities, a rusty pipe spewing chemicals into an algae-choked river; perhaps if you’ve watched Blue Planet II- a plastic bag in the ocean. Air, water, and plastic pollution are the three major pollutive threats to animals-, but less of a din is made about pollution from excessive sound. As a result, wildlife in the air, land and sea are killed daily from being subjected to the ever-growing anthropogenic auditorium.
The cacophony of the 21st century has introduced a myriad of sounds into the world, predominantly caused by the acceleration of technology and traffic. This has not crept by unnoticed. Humans have a limited hearing range of 64-23,000Hz, compared to other species such as beluga whales (1,000-123,000) and mice (1,000-91,000). Noise- specifically lengthened exposure to loud, stress-inducing sounds like aeroplanes- is the second most significant fatal pollution that kills 1 million people p.a. in Western countries alone and is also hypothesised to cause cardiovascular issues such as type 2 diabetes. And we can’t even hear in ultrasonic. On land, traffic and roads have led to a range of behavioural changes which can inhibit bird and mammalian responses to actions that could affect their survival. We’ve all heard the term “rabbit in the headlights” when rabbits freeze in the middle of the road in front of a car, an evolved instinct to escape predators, yet this ultimately leads to their demise. In a study published in 2013, behavioural ecologists set up a ‘phantom road’ to monitor migrating birds’ actions. They discovered that the frequency of birds resting significantly dropped- these birds are fine-tuned to avoid predatory noises- having repercussions on not only the health of the birds but also reducing pollination in the areas, as the birds land in the area less. Similarly, in bats who rely on echolocation to find food, their returning clicks are drowned out by night noise, leading to 40% less activity and proficiency in hunting. In tropical regions, not only do wildlife suffer from noise from the ever-expanding road network, but this also brings the added threat of greater deforestation and poachers. Clearly, diminished resilience caused by traffic has the capacity to send ripples across entire ecosystems.
Human commotion also makes waves in the ocean. In particular, shipping and sonar. 2020 recorded the largest historical strandings, with 450 pilot whales beached on the Tasmanian Coast. Whilst the cause was not apparent, past strandings of similar magnitude have been attributed to sonar, which operates in the same frequency but at a higher decibel than cetacean’s own echolocation, and haemorrhages in inner ears that indicate distressing noise, as well as sonic blasts, shipping and the oil industry, operate in the same acoustic niches, creating acoustic barriers to baleen whale communication. This includes obtruding feeding and mating calls, which forces the whales to change their calls and potentially inhibit the healthy neurological development of calves in tropical breeding grounds. Smaller sea life do not escape the siren’s call either. Research conducted on juvenile European eels displayed that they reacted slower to a potential looming predator than in a noise-free setting, potentially due to stress when subjected to shipping sounds. As the authors conclude, this deafening in a nursery environment impairs the survival of the eel and other vulnerable species.
When you can’t raise your voice loud enough to be heard, you switch tactics. Like the humpback whales changing their calls, some species are tolerant and can adapt to the loud anthroposphere. For example, hummingbirds who preferentially seek noisy habitats heighten pollination in the area, thus rising in influence as a keystone species in the local ecosystem. Furthermore, harbour seals also successfully utilise noisy infrastructure- wind turbines- as foraging grounds for reefs. Yet, the more comprehensive ecological benefits or drawbacks of this behavioural change are still not yet understood.
Anthropogenic silence is not deadly, whereas media, research and policy silence on the matter is. There is almost a murmuring haziness on concrete laws, a mismatch of frequencies with the increasing crowd of published journals clearly defining the correlation between noise pollution and wildlife and human health. For example, in one of their clauses for ocean health, the EU states that member states should limit noise pollution but do not clearly define or limit noise-inducing activities. However, some places are putting in substantial efforts to muffle traffic. In the Port of Vancouver, a public Underwater Noise Management Plan published in December 2020 details annual targets to monitor and mitigate noise produced by vessels in the area, involving a range of stakeholders to protect marine animal health collectively. Interestingly, the Noise Pollution Act in the Netherlands has a ‘noise emission ceiling’, thus formally recognising noise as a form of pollution by relating it to an ‘emission’ and posing an upper limit on noise. Construction and industrial companies must document their proposed level of noise, which is later monitored by local authorities to ensure it is kept. The long term effects are yet to be assessed, and there is limited citizen inclusivity in both projects, but they are a good start.
Elsewhere, vibrations to counter the effects of noise pollution take a bottom-up and creative response. For example, Alicia Hayden, a recent graduate of Oxford University, artivist and budding filmmaker, drew ‘When the Whale Sang’. This piece won the Human Impact prize from the famous David Shepherd Wildlife Art competition. The work was inspired by a blog post she wrote for the British Ecological Society during lockdown. This piece highlights how these beautiful creatures are being “broken” by noise pollution, she aims to make others aware of the damage noise causes to ecosystems because it’s less visible but no less harmful than other forms of pollution.
Much of the commotion in noise pollution starts with traffic, so research facilities and companies aim to tackle this. ‘Quiet pavements’ – the development of honeycomb-like two-layer porous asphalt (TLPA) has significantly reduced noise pollution in European and US cities. Refining the airflow around aircraft has had a similar effect in the skies over the last couple of decades. The recent development of sound-dampening foams has also shown promise, modelling hummingbirds’ wings. The architecture of nature may genuinely hold the answers to sounds that threaten to destroy it.
Globalisation has radically altered the Earth’s landscape, seascapes and even the soundscapes to an abrasive amplitude. Technically speaking, noise is one of the easiest pollutions to treat as it disperses immediately, but through innovation, policy and individual responsibility, all we need is some quiet.