One of the great environmental issues of today is deforestation, with millions of hectares of forest lost across the planet in the past 30 years. This deforestation affects not only people living in the nearby areas but also threatens endangered species and contributes to global warming. And forests are complex ecosystems, so the loss of trees can have wide-reaching implications for biodiversity — a topic that is now being studied using sound.

Researchers working in the Amazon rainforest collected acoustic data from beneath the forest canopy to build up a sound picture of the forest, which they say can help indicate its health. “I’ve been working with tropical forests all my professional life,” said researcher Danielle Rappaport in a statement. “I’ve never quite been to a forest that was this devastated. It’s something that you can smell, you can hear, it’s everywhere.”

Rappaport and her colleagues used a network theory approach to analyze data from multiple recorders around the forest, by listening to the overall soundscape rather than identifying the sounds of each individual species of birds, insects, primates, and more.

“It’s one more step towards understanding the sound community without needing to know which individual species are there because we’re starting to listen for them in ways that help us connect the coordinated production of sound, even if we don’t know who’s making the noise,” said another of the researchers, Doug Morton.

This acoustic data was combined with data from NASA Landsat satellites about areas of logging or fires. The Landsat data stretches back over 30 years, so it helps give a timeline of activity in the Amazon as it is affected by human behavior. It was supplemented by lidar data showing a three-dimensional map of the rainforest canopy. Taken together, the soundscape can reveal surprising information about biodiversity in forests.

The research showed that although forests do have some ability to recover from logging, biodiversity in forests that have been repeatedly logged is worse than in those which have only been logged once.

“Sound data add a new dimension to our understanding of the Amazon,” Morton said. “I’m fascinated by what we still have to learn.”