How Traffic Noise Impacts Pennsylvania’s Ecosystems

Have you ever walked a forest trail? You see the typical sights, rustling leaves, birds, deer, and a creek. Imagine that same forest with the constant drone of cars nearby. You might still see nature, but the sound and experience of that walk through the woods would be different.

Sound is more than background noise for birds, bats, frogs, owls, and countless other animals. They use it to find mates, locate danger, hunt prey, or avoid predators. As road noise spreads, the vital communication animals rely on is being drowned out. The consequences are more serious than most people realize.¹

Unlike air or water pollution, noise pollution doesn’t leave a visible mark. Studies show that as background sound levels rise, the acoustic “listening area” available to animals shrinks dramatically, and in some cases by more than half.² A predator that once heard prey from far away now has a much smaller range in which it can detect the rustle of an insect or the call of a frog.

In a unique experiment, researchers created a “phantom road”, which consists of a series of speakers in a previously quiet area that simulated traffic noise without any vehicles. They found that nearly one-third of the bird community avoided the noisy area entirely. The species that remained often suffered reduced body condition and poorer ability to gain weight, which is a critical factor for migrating birds and survival.³

Pennsylvania’s forests are already facing multiple environmental pressures, from invasive insects to tree diseases. Species like the emerald ash borer, spongy moth, and hemlock woolly adelgid have already caused widespread tree mortality in our state.⁴

Under normal conditions, birds serve as natural pest control. Woodpeckers consume massive numbers of emerald ash borers; orioles, cuckoos, and chickadees eat spongy moth caterpillars and eggs. When traffic noise interferes with their ability to communicate or forage, their effectiveness in keeping pest populations in check declines.⁵ Nocturnal predators like owls depend on acute hearing to detect the faint rustle of prey. Data shows that traffic noise reduces owls’ foraging efficiency, diminishing their ability to hunt effectively near roads.⁶

When acoustic predators lose their natural senses, the balance of ecosystems shifts. Small rodents and insects can thrive unchecked. That affects vegetation, seed dispersal, and the entire web of life that depends on natural checks and balances.

Noise travels deep into adjacent habitats, effectively reducing usable space for wildlife, even where forest or meadow still stands.⁷ We see this in the swaths of dead trees along the turnpike, or the insects terrorizing our forests, parks, and gardens. 

For animals that rely on sound to navigate their world, roads aren’t just a barrier; they are a zone of acoustic habitat destruction. Two forests with identical tree cover might be very different biologically if one is beside a highway and the other is quiet.

Humans aren’t immune to the effects of noise either. Chronic exposure to traffic noise has been linked to sleep disruption, cardiovascular stress, and decreased quality of life in people. When we talk about environmental justice, noise pollution often overlaps with communities most impacted by other environmental burdens. Noise doesn’t just hurt people. It undermines the natural systems that support clean air, healthy forests, pest control, and biodiversity. 

Traffic noise has real consequences for tree health, forest resilience, and the very landscapes we cherish; and all of this in turn, impacts public health. If insect populations are left unchecked by their natural predators being impacted, we could see a rise in insect-borne illnesses in Pennsylvania, such as lyme disease and west nile virus, due to higher populations of ticks, mosquitos, spiders and more. Couple this with the changing climate, and we have a recipe for a changing landscape.

Addressing noise pollution does not require banning cars, but it does require thoughtful policy and technology that reduces unnecessary noise and protects both human and wildlife health.

Legislation like HB 2069, which would allow communities to enforce vehicle noise standards using automated systems, represents one piece of a broader effort to rebalance our soundscape. By reducing excessive noise at its source, we protect the acoustic integrity of habitats. Despite the benefits, we must be cognizant not to introduce these measures in a non-equitable way. We cannot use them to further target already-impacted communities, but must use these policies in ways that are rooted in science, data, and empathy.

References

1. National Park Service, “Effects of Noise on Wildlife,” NPS Natural Sounds and Night Skies Division, https://www.nps.gov/subjects/sound/effects_wildlife.htm

2. National Park Service, “Decibels and Listening Areas,” NPS Natural Sounds, https://www.nps.gov/subjects/sound/mapfaq.htm

3. R. M. Barber et al., “A Phantom Road Experiment Reveals Traffic Noise as an Invisible Source of Habitat Degradation,” PNAS, https://www.pnas.org/doi/10.1073/pnas.1504710112

4. Pennsylvania DCNR, “Insects and Diseases,” https://www.pa.gov/agencies/dcnr/conservation/forests-and-tree/insects-and-diseases/

5. Traffic noise impacts on birds’ alarm calls and foraging, All About Birds, https://www.allaboutbirds.org/news/traffic-noise-reduces-birds-response-to-alarm-calls/

6. “Varying Behavioral Responses of Wildlife to Motorcycle and Traffic Noise,” scholarly data, https://www.sciencedirect.com/science/article/pii/S2589004223007277

7. National Academies Press, Assessing and Managing the Ecological Impacts of Paved Roads, https://nap.nationalacademies.org/read/18336/chapter/3