Studies have found that anthropogenic noise is reducing the level of noise that wildlife creates.
As cities fall silent during the pandemic, many have been experiencing nature become louder, with the experience of birdsong sounding somehow more sonorous. This is no illusion – research now reveals the adversity anthropogenic noises create for the survival of a panoply of species, and with them, their sounds. Put simply, the louder humans are, the quieter nature becomes. In our culture’s conversations on the havoc the Anthropocene wreaks upon wildlife, noise pollution is all too frequently absent. Yet drilling, revving, and sawing – the tripartite of sounds that best signify human consumption, production, and destruction – are not just consequential in their linkage to habitat loss or polluting emissions. Their immediate by-product of noise is a unique challenge to the animal kingdom as well.
Why and how? An answer lies with soundscape ecologist Bernie Krause, a pioneer in his observations on how noise pollution affects wildlife. In developing the acoustic niche hypothesis, Krause argued that ecosystems have evolved in a way so that each species acoustically partition through different rhythms and pitches, thereby staying off one another’s turf. By recording natural soundscapes, he observed how man-made sounds disrupted the “animal orchestra”. In one such recording, a chorus of spadefoot toads is interposed by the roar of jet-engines miles overhead, causing a 45 minute lag in re-synchronisation of the amphibians, within which time predators had taken advantage of the disharmony to hunt. It doesn’t take a conservationist to assume the long-term result of such a flight path – the toad’s population drastically decreased. Here we see how the shared orchestra produced by animal life is vital to their survival and how urban encroachment can destabilise entire ecosystems.
Birds are one of the better understood and observed barometers of noise pollution’s impact on fauna owing to their sensitivity to sound and reliance upon acoustic signalling for communication. A recent Pacific University study found that zebra finches’ problem-solving abilities were impaired by exposure to traffic. Given tasks, which included pulling strings and flipping lids on their cage’s floor to retrieve food, the researchers found that in comparison to controlled conditions the exposed birds were almost twice as likely to fail. Christopher Templeton, who led the study, broadens the research findings’ implication in stating: “If we assume that similar processes are going on in other cognitive animals, then it is reasonable to assume that a large number of animals and animal species are being affected by noise pollution.”
Lockdown has functioned as a case study on the effect of anthropogenic noise. The sudden emptying of our streets and consequent noise reduction has opened a vacuum in acoustic space, which we are now finding songbirds and other species fill. Contrary to the widespread view that birdsong is louder during lockdown, the Lombard effect tells us that the quieter our environment is, the quieter all animals become. A 2020 study by Derryberry, et al. compared the soundscape of San Francisco’s Bay area before and during the first series of local restrictions when noise pollution was the lowest it had been since the 1950s, and observed several interesting behaviours in songbird populations. As anticipated, the researchers found that birdsong was softer (sung at much lower amplitudes), but at a reduction unexplained by the Lombard effect.
So why was the loudness of birdsong so highly reported? Despite the quieter singing, the birds’ communication distance had doubled, meaning they could expand their pool of potential mates, with the added effect that human ears received birdsong from twice as far, effectively perceived as there are four times as many birds. Birds also developed a better, more “sultry” vocal performance in a quieter environment, finding it easier to attract mates. Played out in real-time was the complex butterfly effect noise has on animal life, and as Templeton reflects, “may well include our own species”.
So, if silence is this important to our planet’s survival, what can we do to reduce the seemingly inescapable noisiness of modern living? Soundscape ecologist Bernie Krause provides a forthright answer: we need to learn to “shut the hell up”. If we want to retune our place within the animal orchestra, we must first heal the divide between human and non-human. Interacting with nature needs to be less self-centred, with phones put away, chit-chat turned down and the presence of sounds around us embraced. In a country where so-called beauty spots have become tourist destinations, learning to connect with nature without damaging it is of utmost importance. Such action will not save ecosystems, but it is by learning to care deeply and authentically about nature and seeing ourselves not as opposed but as part of it, that we can begin taking important practical steps, like adopting silent electric cars, toward adapting our urban landscapes with their non-human inhabitants in mind.