We know noise pollution is bad for humans, increasing our risk of health problems like stress, heart disease and tinnitus, plus cognitive impairment in kids. We also know it harms many other animals, like songbirds, dolphins and whales.
According to a new study, however, human noise is a "major global pollutant" that harms a wider range of animal life than we tend to think. Published in the journal Biology Letters, the study suggests noise pollution not only harms lots of animals, but also threatens the survival of more than 100 different species. Those species hail from all over the animal kingdom, the study found, including amphibians, arthropods, birds, fish, mammals, mollusks and reptiles, living both on land and in water.
And despite many obvious differences among these diverse animal groups, species from each group show surprisingly similar reactions to noise pollution.
"The study found clear evidence that noise pollution affects all of the seven groups of species, and that the different groups did not differ in their response to noise," says lead author Hansjoerg Kunc, a senior lecturer of biology and animal behavior at Queen's University Belfast, in a statement.
Given such broad and consistent damage to so many different kinds of creatures, this suggests noise pollution affecting animals is the norm, not the exception. And on top of raising awareness about the dangers of noise pollution, these findings also "provide the quantitative evidence necessary for legislative bodies to regulate this environmental stressor more effectively," the researchers write.
Noise pollution is now widely recognized as a danger to human health, but as the World Health Organization (WHO) points out, it's still getting worse in much of the world, often lacking the kind of regulation that limits other forms of pollution.
Only relatively recently have we begun to reveal how noise pollution affects wildlife, and while this "led to a number of excellent experimental studies," the researchers write, "single studies cannot provide holistic quantitative assessments on the potential effects of noise across species." That kind of broad analysis is important, they explain, since it can both inform conservation efforts and help us learn how evolutionary ecology makes species more or less susceptible to noisy humans.
For the new study, Konc and co-author Rouven Schmidt conducted a meta-analysis, looking at a variety of published studies on how nonhuman animals respond to noise pollution. By integrating these studies' findings and analyzing them together, they identified several threats from noise pollution that could affect survival and population trends for a wide range of animals.
Lots of species rely on acoustic signals for communication, for example, including many amphibians, birds, insects and mammals who use sound for vital business like finding mates or warning about predators. If noise pollution drowns out enough of these messages, hindering their ability to reproduce or flee mortal danger, it can threaten survival and the stability of their population.
On the other hand, while noise pollution makes some animals more vulnerable to predators, it can also have the opposite effect, making it harder for some predators to find food. Bats and owls rely on sound to hunt, for instance, which may not work if noise pollution obscures the subtle sounds of their prey. Even if noise pollution is mild or intermittent, it might still force them to spend more time and energy searching for food, which could be enough to trigger a decline.
Noise pollution is a well-known risk for whales and dolphins, but it threatens other aquatic animals, too. The researchers cite fish larvae, which are instinctively drawn to the sounds of coral reefs. This is how they find suitable habitats, but if their journey features too much noise from ships and other human sources, more fish larvae may get lost or move into subpar reefs, potentially reducing their lifespan.
Similarly, noise pollution influences the way animals migrate, which in turn can have ripple effects for ecosystems along migration routes. Some migrating birds avoid areas with noise pollution, the researchers note, which may change not only where they travel, but also where they establish long-term homes and raise their young. Many ecosystems and non-migrating species have come to depend on the arrival of migrating birds, and many others may be unprepared for their impromptu detours, so this could trigger a cascade of ecological changes.
"This large-scale quantitative study provides significant evidence that noise pollution must be considered as a serious form of man-made environmental change and pollution, illustrating how it affects so many aquatic and terrestrial species," Kunc says. "Noise must be considered as a global pollutant and we need to develop strategies to protect animals from noise for their livelihoods."
As harmful as noise pollution can be, however, there is reason to be hopeful. Unlike chemical pollution, whose toxic legacy often lingers in the environment for years, noise pollution only exists as long as people or machines are making the noise. Instead of cleaning up another mess, in this case all we have to do is quiet down.