When Eddie Game straps the first wallet-sized recording device around a tree trunk in Papua New Guinea, he’s so deep in the Adelbert Mountains it’s a three-day hike from the closest road. A second device is secured on a neighboring tree. One will capture ultrasonic sounds imperceptible to human ears, the other, audible sounds. Local rangers swipe bush knives through the underbrush, guiding Game and his team of conservation scientists through this rugged, largely untouched forest. Their shoes remain perpetually soggy. They’ll arrange devices in four more areas today and set them all to record for 24 hours. Hopefully, rats and possums won’t chew up the microphones or straps.
“What we’re interested in is overall soundscapes, how rich they are,” says Game, lead scientist for The Nature Conservancy’s Asia Pacific region and senior fellow at the University of Queensland, Australia. The more complex and dense the sounds, the healthier the habitat. Game is in Papua New Guinea to measure whether or not the conservation zones The Nature Conservancy helped set up 15 years ago are truly benefiting wildlife.
Bioacoustic technology has long been used to identify and count specific species. Game and his team, however, use holistic soundscape recordings to monitor overall animal biodiversity in tropical forests. They recently published the results of their work in the journal Conservation Biology, discovering that the dawn and dusk choruses were the most impacted by human activity. In Science, the team stressed the incredible potential of this research method, noting their random forest sound models “can predict species richness with very high accuracy.”
Though tropical rainforests cover a mere 2% of the Earth’s surface, they are home to more than half of all plant and animal species. During peak noise-making hours, these forests practically vibrate with sound: Birds call, insects whirr, monkeys howl, frogs chirp, wildcats growl, bats click, rodents squeak, and snakes hiss. The soundscape changes dramatically, however, when biodiversity decreases.
“There’s a very clear signal when an environment gets degraded — it gets quieter,” says Game…