The rustle of pine needles, the call of songbirds and the bugle of elk are as much part of Rocky Mountain National Park as the mountain vistas — and researchers say that in some protected areas across the United States, those sounds are at risk of being eclipsed by human-created noise.

A coalition of Colorado State University and National Park Service researchers created a model to understand how noise pollution contributes to the din in protected areas across the country.

In about one in five natural areas, they found noise pollution led to a 90 percent reduction in “listening area.”

Translation: Where once you could hear a bird’s song from 100 feet away, noise pollution may have reduced that distance to just 10 feet.

“We found fairly alarming levels of noise pollution in large portions of protected areas,” CSU postdoctoral research fellow Rachel Buxton said. “We’re starting to realize more and more what a problem noise pollution is. Until now, we didn’t realize really at what scale that problem was happening.”

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