Alva Review-Courier -

COLORADO SPRINGS, Colo. (AP) — The Holzwarth Historic Site in the Kawuneeche Valley on the west side of Rocky Mountain National Park is unusually quiet for a mid-August night. At the height of summer tourist season, the park attracts hordes of visitors — more than 4 million in 2017. But the only noises are the flutter of the wind passing through the leaves of the aspens, the crunch of the gravel under deliberate footsteps and the occasional muted murmur of a park employee's radio.

Silence was what landscape ecologist Hanem Abouelezz needed as she peered through a stand of aspens at a 4-year-ol...