Lockdown gives animals rare break from noise pollution

While a drop in transportation during the coronavirus lockdowns has led to lower pollution levels across the world, the slowdown in traffic has also lowered another big polluter: noise.

According to the World Health Organization (WHO), noise pollution affects over 100 million people across Europe and, in Western Europe alone, road traffic accounts for premature deaths equivalent

to the loss of roughly “1.6 million healthy years of life.”

Take the disturbance to human health out of the equation, and noise remains a big source of pollution for the other inhabitants of the planet as well, namely, animals. But how much have animals in countries on lockdown really benefited from the drop in noise levels? Turns out, that’s a very difficult question to answer.

Birds — by far the most visible animals found in cities, and also the most vocal — stand to be among the biggest beneficiaries of quieter streets and parks. The signals birds send each other through song is a means of survival. Without the ability to sing, hear and be heard, birds would have a difficult time finding a mate or defending their territory from predators. The rise of human-made noise, also known as anthropogenic noise, over the past century has made this harder for birds.

Just like humans who have to speak up in a loud setting, birds, too, have to sing louder to communicate properly in today’s noisy world, according to ornithologist Henrik Brumm, who heads the research group for the communication and social behavior of birds at the Max Planck Institute for Ornithology near Munich. “This happens really fast,” Brumm told DW. “We found out that it takes roughly 300 milliseconds, so less than 1 second, for birds to readjust when the level of noise rises. So, when their surroundings become louder, they sing louder, too.”

Birds are already known to sing more quietly in the early morning hours of the weekends, says Brumm. The reason: there’s less traffic to compete with. With Europe on lockdown, Germany for its part, has seen passenger air travel slashed by over 90%. Moreover, car traffic has dropped by more than 50% and trains are running at less 25% their usual rates.

A recent study from the Max Planck Institute also suggests that chronic traffic noise can have a negative effect on embryo mortality and growth in zebra finches. This, in turn, could mean that the current lockdowns coinciding with mating season could lead to not only more, but also healthier hatchlings. That is, as long as their parents choose a spot that’s still safe from humans after the lockdown ends.

While research on noise pollution and marine life, just like with ornithology, is in its early stages, a landmark study conducted in the days after 9/11 found that less shipping traffic seemed to make whales calmer.

Examining the faeces of right whales — a species of baleen whale that can reach 15 meters in length and weigh up to 70 tons — researchers found that fewer ships in the waters along the US-Canadian coast correlated with lower stress hormones.

The noise levels from shipping traffic, whose 20–200 Hz hum disturbs sea life despite being a low frequency, decreased by 6 decibels, with a significant reduction below 150Hz . Just like ornithologists, marine life researchers have also found correlations between noise and interruptions in behaviours like foraging and mating.