The Quiet Crisis – How Sound Pollution Affects Our Wildlife
Animals are like us in many ways, most especially in the sense of hearing. They rely on their hearing to detect prey and elude predators, and it’s also critical for communication within their species and environment. That said, anthropogenic noise—the noise made by us—is beginning to take hold of wildlife, even in their own homes.
In this blog, we’ll explore the different ways that animals are being affected by anthropogenic noise and what we can do to help.
Why is hearing important for animals?
As previously mentioned, animals use sound for things like communication, but what else do they use sound for and why is it so important for them to keep their hearing?
Mating
For many species, animals, such as birds or frogs, rely on particular calls to attract mates. Most are low-pitched, however, recently, some animals have been making their voices higher in order to compete with the low-frequency sounds of things such as car engines. This can make it more difficult for them to find mates, as these changed frequencies come off as less attractive. Plus, in noisy environments, the breeding pool becomes much smaller as the range is far less, affecting population sizes and diversity.
Foraging
In louder environments, some animals with more complex ears cannot help them detect prey. One study found that in every 1dB increase in noise in an area, owls in that area were 8% less likely to be successful in catching prey. Even in herbivory, noise is often seen to deter many species of seed-eating birds, which also decreases the spread of seed—this might affect a habitat’s plant community in the future.
Navigation
Human-generated noises, such as sonar or traffic, can disorient animals that use calls at a certain frequency to spot obstacles and prey in the area (such as bats and other nocturnal animals). These anthropogenic noises can ultimately damage their hearing altogether, or cause them to adjust the pitch of their calls in ways that are not useful to them.
Anthropogenic Affects
As far as human health goes, anthropogenic noise has been known to be harmful to us; causing high blood pressure, heart disease, sleep disturbances, stress, and more. Since the Industrial Revolution, the noise that we put out that significantly alters the acoustic environment has steadily increased. This is due to population growth, infrastructure development, mechanization, and overall demand for resources. In the United States alone, 63% of protected areas experience sound that is double that of the ambient level.
Noise can lead to both temporary and permanent avoidance behaviors in multiple species, especially migrating birds and insects. Some birds will avoid stopping over noisy areas, while insects have been shown to disappear entirely from an area.
Additionally, animals in noisy environments sometimes show altered levels of stress hormones, which are linked to increased stress responsiveness. For example, loud noises can cause a caterpillar’s dorsal vessels (which is their heart) to beat faster. This can then lead to a poorer body condition and also a reduced reproductive rate (lower hatching success or poorer growth and development in offspring). Noise may result in the activation of the hypothalamic-pituitary-adrenocortical (HPA) axis. So, if an animal is unable to leave the source of stress, this HPA system remains activated, and the physiological and behavioral changes that help stabilize stress and assist in survival may become detrimental. Extensive exposure to stress affects hair growth, accelerates aging, depletes energy, and negatively impacts cognitive function—this damage from stress is no different from animals than from us.
Further, indirectly, changes in a species’ local presence can also have consequences across trophic lines—most especially if those relocating due to noise are parasites or predators. Noise and relocation can alter the predator-prey relationship as predators may have to be forced to switch to uncommonly eaten prey or prey they have never hunted before. More, if seed dispersers are impacted, they can also impact the tree and flower communities, which are a massive foundation for most terrestrial ecosystems.
The aftermath of a noisy environment has various outcomes. For some, many communities of wildlife and ecosystems do not leave long-term traces in the environment once the noise is removed. A study on white-crowned sparrows shows that they reverted back to their original low-frequency songs. However, juniper and pinyon seedling recruitment did not recover after the removal of noise.
Chronic Noise Pollution Affects Graphic. Image Source.
What can we do?
In any soundscape, properly sited vegetation can assist with noise control. A combination of good vegetation near the noise source can provide year-round soundproofing.
Additionally, insulating buildings with noise-absorbing materials can drastically reduce and help the noise pollution. Having proper urban planning in cities can help reduce noise pollution before it increases any more.
Whenever possible, turn off appliances when not in use. Alternative ways of transportation that aren’t noisy cars or planes. Be aware of the machinery you use and use low-noise models.
Be aware of the protected areas and ensure noise levels there remain at the recommended level.
Ultimately, anthropogenic noise is everywhere. But the more we spread awareness to the root of the issue and begin making changes to even the smallest of our own behavioral patterns, it can make an impact on the wildlife that has been here long before we have.
Sources:
How Chronic Anthropogenic Noise Can Affect Wildlife by Frontiers, 2023
Noise Pollution by National Geographic
4 Ways Noise Pollution Impacts Wildlife by the Wildlife Habitat Council