While noise pollution has a detrimental effect on our wellbeing, with exposure causing physical and emotional health issues, research has shown that it affects wildlife too.
Noise pollution (or sound pollution) is any noise which has a harmful impact on human or animal life. The main sources of outdoor noise worldwide are transport and machinery.
Excessive noise causes the birds and the bees to alter their behaviour in many significant ways: it interrupts mating, reduces the number of birds and insects in the vicinity, causes them to stop moving (a “shock” reaction), and prevents birds from hearing fellow birdsong that’s important to their day-to-day life.
A number of scientific studies have been completed in recent years to find out more about how noise pollution affects insects and small animals. There have been some fascinating findings that show how excessive noise is as upsetting for the animal kingdom as it is for human beings.
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A study by researchers from the University of Alberta, in Canada, has found that noise pollution can prevent birds from mating – a problem which may have a negative impact on bird populations in future. Birds communicate by singing and by making other sounds.
The habits of the oven bird, a small species found in the Canadian forests, were studied by scientists to ascertain whether those living in quiet and isolated areas behaved differently from those living near compressor stations – the stations generate pressure in pipelines, keeping oil and natural gas flowing from wells. They produce a constant noise level of up to 90 decibels, which is similar to the noise produced by a lawnmower.
The study concluded that the louder environment interfered with the birds’ ability to hear each other sing. A male bird’s song is very important in the mating ritual to attract a female. If the external noise factors drown out or distort the male’s song, he may not attract a partner.
Research found that birds living near loud noises had only a 77% pairing rate, compared with the 92% success rate of birds living in quieter areas of the forest. The researchers said that as noise pollution grew, there would be fewer quiet spots for the birds’ habitat and this could lead to a decline in their population.
The report concluded that if humans took measures to reduce noise pollution, the situation could be alleviated. In the case of the compressor stations, technology should be used to reduce the noise levels by increasing the insulation of the equipment, using sound baffles and silencers.
A study by Boise State University in Idaho looked at the effects of noise pollution on birds living near roads, where numbers were in decline. The 2013 study was the first of its kind to distinguish between the consequences of noise on wildlife from the effects of traffic collisions, visual disturbances and chemical pollution.
While carrying out daily bird surveys, researchers put speakers in trees near Idaho Bird Observatory to create a mock road, playing traffic sounds at intervals. During noisy periods, the bird population declined by around 25% and some species avoided the area altogether.
The research suggested that the noise of traffic was the main cause of the change in the birds’ behaviour. The survey was aimed at understanding the effects of noise to assist wildlife managers in their conservation efforts and future management of the birds’ habitat.
Studies reported by the US Department of Transportation’s environment department labelled the migration of birds away from noisy roads the “highway effect”. A study of 43 species of woodland birds found that 60% of them reduced in numbers nearer the road.
Noise was the “only significant factor” that also influenced the number of breeding pairs in the vicinity. There were no breeding pairs within 400 metres of the road.
As the road network grows, scientists fear that the subsequent noise will further reduce the birds’ natural habitat, leaving them with fewer places to breed and ultimately reducing their population.
Noise pollution has also been found to affect insect behaviour. Studies have indicated that some species of insect are sensitive to noise, particularly low-frequency vibrations.
An American study of insects in the vicinity of loud gas compressors found that sites near the compressors had 95% fewer crickets, 52% fewer froghoppers and 24% fewer grasshoppers, compared with nearby sites where there were no compressors.
A 2016 study, carried out by researchers at Vassar College in New York, concluded that the noise of traffic interfered with the mating calls of tree crickets. It could distort the call to such a degree that it could trigger a different behavioural response. The male crickets’ calls (made by using their wings) are aimed at attracting females.
research found that the duration of the mating calls was reduced significantly in areas where there was loud noise from traffic. Scientists suggested that when the crickets sensed their own songs were unlikely to be heard, they reduced the energy put into the mating calls by shortening the length of the song and inserting more pauses, making the calls less likely to attract a female.
The bee is also affected by noise pollution, which has an unusual effect on its natural behaviour. When encountering noises of around 300Hz and 1kHz, at an intensity of between 107 and 120 dB, honeybees will stop moving altogether for around 20 minutes – as if the noise has put them into shock. They then appear to “recover” and resume their normal behaviour.
Professor Jesse Barber, senior author of the study, Anthropogenic Noise Changes Arthropod Abundances, described noise as “sensory pollution”. He said that insects were vital to the ecosystem, so it was “critical” to understand how noise caused by humans was changing their behaviour and distribution.
Studies are continuing to determine the effects of noise pollution on our wildlife and the ecosystem. They describe how the expansion of human infrastructure is creating “sensory pollution” that is seriously affecting other species.
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