Traffic blaring on the ground, planes roaring through the sky, ships bellowing through the oceans—where humans go, they often make a lot of noise. Excess noise is known to have adverse health effects for humans, and according to a wide-ranging study published in Biology Letters, man-made noise should be considered a “major global pollutant” for animals, too.
Previous research has shown how noise pollution impacts specific creatures. Seals, for instance, may be deafened by the underwater rumble of shipping traffic, while stressful noise levels seem to cut short the life expectancy of zebra finches. But the new study, co-authored by Hansjoerg P. Kunc and Rouven Schmidt of Queen's University Belfast, is a meta-analysis, combining data from multiple studies to take a broad look at how noise pollution impacts a variety of species.
The analysis covered 108 studies of 109 species, which were divided into seven groups: amphibians, anthropods, birds, mammals, fish, reptiles and molluscs. Both terrestrial and aquatic animals were included in the analysis. According to the Guardian’s Nicola Davis, the researchers looked at studies that measured changes in species’ behavior or other traits, like hormone levels, both before and after exposure to noise. “The size of any shift from pre-noise behaviour was then calculated on a scale,” Davis explains. “The latest research took all of these calculations and put them together.”
All seven groups were impacted by anthropogenic noise, the researchers found, as were a wide range of species—from tiny insects to large marine mammals. In other words, Kunc and Schmidt tell Agence France-Presse, the issue should be viewed as the “majority of species responding to noise rather than a few species being particularly sensitive to noise.”
The study was too large-scale to delve into the ramifications of noise pollution; it assessed whether noise affects animals, but did not explore whether that impact is positive or negative. The answer is likely to change depending on context. Traffic noise, for instance, reduces the hunting efficiency of bats, which rely on acoustic cues to find prey. That’s bad news for the predators, but not such bad news for the critters they hunt.
Yet the researchers stress that noise pollution poses threats that could impact the survival of many species. Amphibians, birds, insects and mammals all rely on sound to convey essential information, like mating and warning signals. Fish larvae find their homes by following the sounds of coral reefs. Owls, like bats, use acoustic signals to locate prey. All of these fundamental behaviors are at risk if animals can’t hear properly over booming anthropogenic noise.
Changes caused by noise pollution do not occur in a bubble. Some birds, for instance, will steer clear of excessively noisy areas during migration, the researchers found. And this in turn reduces species richness—something that is vital to the health of the planet.
The researchers say that their study provides “the first comprehensive quantitative empirical evidence that noise affects many aquatic and terrestrial species.” And that is crucial from a conservation standpoint, because “it shows that noise affects not only a few species that we need to pay attention to but many species that inhabit very different ecosystems.”