|Image Credit: Thing Three.|
The noisiest place I ever lived was an apartment at the corner of Sixth Avenue and 15th Street in Manhattan. It was the nexus of several bustling neighborhoods and a hub of public transportation, with subway stops mere blocks in each cardinal direction and even a New Jersey PATH train station within easy walking distance. New York City’s endless stream of vehicles gushed down the avenue day and night, and an array of 24-hour fast food establishments and markets ensured a steady flow of both gregarious revelers and ranting vagrants. On weekends, street festivals awoke us with their blaring music and electric generators. On rainy nights, the din of hydroplaning taxis made watching a DVD with the windows open impossible. It was effing loud.
As a species, humans excel at making noise. Not content to stick with the howling and growling of other animals, we’ve created machines to augment our collective clamor. And, thanks to our ever-increasing transformation of the planet’s landscape, we’re sharing that noise with other organisms. Everywhere we go, we bring sirens and jets and jackhammers. How is the rest of nature faring with this parade of sound? Sometimes not too well. And a pair of recent studies, each published in the Proceedings of the Royal Society B, highlights how the effects of our auditory intrusions are not limited to land-dwelling animals, or even animals.
Right place, right time
In the weeks following the September 11th, 2001 World Trade Center attacks, many New Yorkers were on edge. They jumped at the sound of car alarms, fretted over riding the subway, and had anxiety dreams filled with airplanes. Meanwhile, North Atlantic right whales (Eubalaena glacialis) were finally able to relax a bit. Why? Because for once they could hear each other without yelling. Ship traffic in the Bay of Fundy, Canada, where whale studies were underway, dropped following the attacks, and with it so did underwater noise levels. Ships produce low frequency sounds that interfere with right whales’ communication vocalizations. So while life on land was newly terrifying and chaotic, underwater an invisible wave of tranquility was sweeping through.
As you can imagine, the exact course of the research wasn’t planned. In the weeks prior September 11th, scientists were plodding along measuring underwater noise levels and also collecting samples of whale crap, unaware of the tragedy-borne opportunity lurking on the horizon. The audio data were collected from August to September of 2001, but the fecal sample study would continue through 2005, from the months of late July to early October (the whales aren’t in town year round).*
Consistent with the scientists’ empirical observations, underwater recordings made after September 11th showed a decrease in noise. But perhaps most interestingly, analysis of the fecal samples found that the post-911 poo had lower levels of glucocorticoid metabolites. Glucocorticoids are secreted in response to various kinds of stress, so the lower levels suggest that quieter waters resulted in calmer whales. Depressingly this might also indicate that, under normal, non-catastrophic circumstances, whales in the region are chronically stressed.
Soothing sounds of the forest
While I myself have never attended a grade school science fair (my childhood was sparse on extracurricular activities) I’m told that a popular experiment for such things is testing whether plants grow better in the presence of soothing classical music versus abrasive rock ’n’ roll. If you’ve read this far hoping to learn about laboratory scientists subjecting potted ferns to daily doses of death metal, I’m sorry to disappoint you. The study at hand dealt with the indirect effects of noise on plant pollination and seed dispersal. Both of these services are sometimes provided by animals, so while the plants themselves may be indifferent to manmade noise, animal reactions to it can influence the plants’ reproductive success.
The authors conducted their research in New Mexico in the Bureau of Land Management's Rattlesnake Canyon Wildlife Area, which houses not just wildlife, but also natural gas wells and the noise-making compressors used for extraction and transportation of the resource. This provided an ideal setting for the study, as the location had both quiet control areas (without compressors) and loud experimental areas (with compressors) and yet none of the confounding variables typically found in noisy spots (i.e., the various urban indignities discussed back in the opening paragraph).
To examine the effect of noise on seed dispersal, the scientists focused on the piñon pine (Pinus edulis), tracking the volume of seeds taken by different animals from both the loud and quiet spots. While some animals seemed to prefer snatching seeds in the noisy areas, the one most likely to help the seeds take root, the western scrub-jay (Aphelocoma californica), carried away more seeds in quieter locales. † This suggests that pines residing in noise-polluted districts may have less luck producing offspring.
Yet the effects of increased noise weren’t always negative. The pollination experiment looked at the auditory preferences of the black-chinned hummingbird (Archilochus alexandri). Unlike the scrub-jays, these birds visited flowers in the noisy sites more often, potentially conferring a reproductive advantage to hummingbird-pollinated plants in loud regions. However, the authors note that the cause of this was probably not the hummingbirds’ fondness for generator sounds, but their aversion to predators that stake out the quieter areas. Like humans choosing an inferior restaurant because it’s easier to get a table, hummingbirds likely hang out in less desirable neighborhoods to avoid the hassles of more popular ones.
So while the exact effect may be difficult to predict, noise pollution – like other more publicized forms of pollution – does have an impact on both flora and fauna, on land and in water. Repercussions of the increasing cacophony of daily life on our own species might also merit examination. Anecdotally, I can tell you that I felt less stressed out after vacating the Manhattan apartment. Though perhaps the toxic fumes emitted by the Cheesesteak Factory (yes, such an establishment exists) were the bigger problem.
* If you’re wondering how one goes about finding whale droppings, as with drugs and bombs, it’s done with the help of trained dogs.
† The scrub-jay stores some of the seeds it swipes, and not all these are eaten later. Thus the unconsumed seeds have a shot at becoming new trees.