Scientists record the sound of intact forest

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  • Composition and saturation of sounds in forests can reveal its health
  • Pristine sites show greater sound saturation than those with less cover
  • Soundscape data can serve as baseline to compare against future changes

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[KUALA LUMPUR] By analysing the composition of sounds in a forest — called a soundscape — scientists can make cost-effective and reliable assessment of the forest, according to a new study conducted in Papua New Guinea (PNG). 

A soundscape’s saturation refers to the variety of pitches and frequencies found in the sounds. The study, published in Conservation Biology on 14 June, confirmed that land-use zones with intact forest cover have significantly higher soundscape saturation.

Autonomous recorders set up at 34 locations in the Adelbert Mountains of PNG covered sites ranging from pristine forests to small cacao farms. Led by Zuzana Burivalova, tropical forest ecologist at Princeton University in the United States, the study recorded almost 1,300 hours of sounds in July 2015.

Burivalova and his team found that soundscape saturation peaked at dawn and dusk, likely because most birds and amphibians vocalise in those periods. Sites with less forest cover due to human activity, such as farming, have less saturated soundscapes versus those with high forest cover, such as conservation and hunting zones.

“Soundscape ecology will be a huge tool for future documentation and evaluation of human impact.”

Jessica Deichmann

“This study is a proof-of-concept that shows we can acquire a lot of high-quality acoustic data in tropical rainforests and that soundscape saturation is a relatively simple measurement that tells us a lot about the environment,” Burivalova tells SciDev.Net.

Sound recorders make great tools for environmental assessment because they can be deployed in remote places and work autonomously for long periods, according to Burivalova. He adds that the ease of collecting data in many locations at the same time would allow scientists to study human impact on tropical forests over large spatial scales.

Furthermore, soundscape data is a permanent record of a specific place and time, so the recorded soundscape can serve as a baseline to compare against future environmental changes.  

But soundscape analysis of terrestrial ecosystems is still an emerging field. Analysis remains the biggest challenge. “In the last five years there has been an explosion of different ways to measure and analyse soundscape data,” says Burivalova, describing the situation as typical of any new field.

Soundscape studies are biased towards animals that vocalise, but biases are inherent in every environmental survey method, says Jessica Deichmann, a biologist at the Smithsonian Conservation Biology Institute who has analysed soundscapes of Peruvian rainforests to document the impact of gas mining.

“Soundscape ecology will be a huge tool for future documentation and evaluation of human impact,” says Deichmann. “This study is a great example of how you can use sound to do that.”
This piece was produced by SciDev.Net’s Asia & Pacific desk.