Listening to forests reveals signs of recovery beyond tree cover
Listening to forests reveals signs of recovery beyond tree cover
Abhishyant Kidangoor
16 Apr 2026<br>Central America
Comments<br>Share article
Share this article
If you liked this story, share it with other people.
Threads
Page link
Scientists have deployed acoustic monitoring techniques to measure the success of a forest protection mechanism in Costa Rica.<br>Using more than 16,000 hours of audio data, scientists found that the payments for ecosystem services (PES) initiative in Costa Rica has helped recover biodiversity in naturally regenerated forests.<br>On comparing the soundscapes, scientists found that naturally regenerated forests sound more similar to protected forests than to pastures.
See All Key Ideas
Can listening to forests help us understand if the life inside them is thriving? Apparently, yes.
Giacomo Delgado likens it to a doctor examining heart health.
“A doctor has listened to many people’s hearts, and knows what healthy hearts sound like,” Delgado, a doctoral researcher in the Department of Environmental Systems Science at ETH Zürich, told Mongabay in a video interview. “She then starts to compare your heart to other heart sounds to see if you have a healthy heart.”
A team of researchers, led by Delgado, has used the same logic to assess the success of a forest protection and restoration mechanism in Costa Rica. Using more than 16,000 hours of audio recordings of the forest, they found that biodiversity was restored in naturally regenerated forests. These forests were also found to sound similar to forests that have been protected for years.
In 1950, half of Costa Rica was forested; by 1995, forest cover had been reduced to 25%, driven in part by cattle ranching and agriculture expansion in the 1970s and 1980s. Since then, however, Costa Rica became something of a pioneer in the payment for ecosystem services (PES) system, a mechanism where landowners and local communities are financially compensated for protecting and preserving forests. The country’s PES initiative, launched in 1997, is one of the first national-level programs of its kind in the world, and to date has covered more than 1.3 million hectares (3.2 million acres).
“Costa Rica’s PES program is notable not only for its longevity and scale, but also for the institutional framework built around it,” Laura Villalobos, assistant professor of economics and environmental studies at Salisbury University in the U.S., told Mongabay in an email interview. “The program has progressively incorporated scientific evidence to prioritize areas facing higher risks of deforestation,” said Villalobos, who wasn’t involved in Delgado’s study.
Satellite data is usually used to gauge the success of forest regeneration. But it’s often a challenge to assess if life is thriving in those forests. Image by Rhett Butler/Mongabay.<br>While satellite data have shown an increase in forest cover, it’s been more challenging to assess whether the recovered forests have life thriving within them. More often than not, forest cover regeneration is considered the key metric of success in PES programs. Biodiversity assessments, however, are more difficult and expensive to implement over large areas. As a result, “biodiversity restoration is still measured predominantly through changes in forest cover, often used as a proxy for biodiversity outcomes,” Villalobos said. “This doesn’t capture the quality of biodiversity, species diversity and ecosystem functioning.”
Enter bioacoustics. For years, scientists have used this noninvasive technology — essentially placing microphones throughout the forest to record animal sounds — to conduct large-scale biodiversity assessments over wide swaths of forests. It’s also used to understand the behavior and communication patterns of animals.
To determine if regenerated forests are functioning as viable habitats, Delgado sought answers to a wide range of questions. When are the big bursts of sounds happening? What species are making these choruses of sounds, and at what times? Is there a high diversity of sounds? Is the sound distributed through all sorts of pitches?
“We have listened to healthy forests and made designations on sound profiles of healthy forests,” Delgado said. “We used those to see how close recovering forests sound to the healthy baseline.”
Delgado and his team captured close to 16,658 hours of audio data from 119 sites across the Nicoya Peninsula in northwestern Costa Rica. They placed their audio recorders in protected areas, forests recovering under the PES program, monoculture plantations, and pastures, and retrieved them a week later. The sites that were sampled include 50 forests that were allowed to regrow naturally without any human intervention. These forests have been recovering after being abandoned for cattle ranching and farming for anywhere between 25 and 42 years.
After analyzing...