Albert McKeon

Apr 22nd 2019

Bioacoustics Can Reveal the Unknowns of Rain Forests


Seeking a complete perspective on biodiversity in tropical forests that are under threat from deforestation and other forces, some conservationists want to combine sound and sight to learn what’s really going on under the trees.

Heralding the value of bioacoustics — the study of the sounds living organisms make — the conservationists believe on-the-ground recordings of the life in forests, coupled with the sights from imaging technology, will finally give scientists and conservationists the complete toolbox they need to protect nature.

Satellite imagery on its own has limitations. Combining it with sound monitoring enables more accurate capture of events and trends, enhancing conservation efforts and academic research.

A Call to Closely Monitor Rain Forests

Contrary to popular belief that logging and other human activities are decreasing the number of trees on Earth, several research organizations last year contended that new forests are actually increasing global tree cover, as reported.

Still, deforestation poses risks to biodiversity by drastically changing environments and decreasing forests’ ability to capture carbon dioxide, which leads to global warming. Last year, the independent monitoring group Global Forest Watch said 113,000 square miles of tree cover, equal to the size of Italy, were lost in 2017 as part of clearing efforts for farming, as Reuters reported.

That’s why a trio of conservationists are excited about the power of the microphone, according an article they published in the journal Science earlier this year. Scientists are already recording in areas like the rain forest of Papua New Guinea’s Adelbert Mountain, but the conservationists hope that the scientific community and private landowners can place recorders throughout almost every tropical forest to record entire landscapes. The sounds and data the recordings produce could enable researchers to accurately assess how birds and bugs react to deforestation, and how environmental protection efforts are faring.

In their article, the conservationists point to the difficulty of evaluating conservation efforts without knowing what happens at ground level. Satellite images can verify whether deforestation has occurred on conservation land, but even when seen from above with quality imaging technology, scientists can’t fully detect the degradation of biodiversity from fires, invasions by exotic species or hunting, the conservationists wrote. Human observation on the ground also has limits: It’s time-consuming and expensive, and some experts might have biases.

Bioacoustics add levels of detail that other technologies can’t capture, one of the Science authors, conservationist Rhett Butler, told Reuters. Using inexpensive audio equipment, scientists can listen for small changes to a landscape, or hear unauthorized vehicles and chainsaws or even gunshots, he said.

By having “ears” on the ground, companies that promise to not cause deforestation can get help with this difficult undertaking — and be held accountable if they fail to provide proper stewardship of the land, according to Butler and his fellow authors. The analyzed data from the recordings can set an accurate baseline on how well wildlife and their environments are being preserved or harmed.

Technology Built for Sight and Sound

Bioacoustics date as far back as the early 20th century, when scientists started studying insect sounds. Scientists have studied the sound-detecting capacities of whales, dolphins and porpoises to better understand how acoustics work underwater, according to Mongabay.

Sound also teaches lessons about space. The Chandra X-ray Observatory — which recently made news for its role in the first-ever image capture of a black holemeasured massive sound waves that were formed by the pressure of gas from a black hole.

But as the conservationists who espoused bioacoustics in the Science article contend, sound is only one measurement of biodiversity. To that end, ecologists have also benefited from advancements in imaging technology. For example, to help distinguish colors and plant species, Northrop Grumman invented the Hyperspectral Airborne Terrestrial Imager. It can see more than 700 spectral bands and accurately show the solar spectrum ranges of any environment.

Seeing is believing, until hearing is required. By combining the sights of image technology with the sounds of bioacoustics equipment, scientists should have their most intimate understanding of how wildlife adapts to the ever-changing world around them.