More than just having lush landscapes, the Amazon Rainforest is also able to "speak". The sounds emitted by the animals – or the lack thereof – can report the damage to the environment around them.

Scientists at NASA's Goddard SpaceFlight Center and the University of Maryland, both in the United States, analyzed the acoustics of the Amazon and found that the soundscape can be a great indicator of the biome's health.

The study is led by Danielle Rappaport, a Doctoral student at the University of Maryland. She and her team combined acoustic data collected from different methods: under the forest canopy, tree height measurements through aircraft flights, logging observations, fire outbreaks, and satellite data.

The results indicate that the Amazon Forest ecosystem suffers from human activities. "I have been working with tropical forests all my professional life. I've never been to such a devastated forest. It's something you can smell, you can hear, it's everywhere," Rappaport said in a statement.

According to the study, in areas that were burned several times, recordings of animal noises were quieter than in intact forest sites. With this, the sound landscape was incomplete, indicating that the species that were present before had disappeared.

Analyzing the sounds

To reach these findings, Rappaport and his team installed degraded area recorders to bring together a more complete and comprehensive sound repertoire. According to experts, the place was extremely punished. The undergrowth of the forest was thick and difficult to navigate, and insects surrounded them.

When analyzed together, these recordings revealed unique ecological fingerprints, or "soundscapes". Species of frogs, insects, birds and primates occupy a sound space in different ways. "You can think of the animal soundscape as an orchestra. The flutes occupy a different time of the day and a frequency band different from the oboes", exemplifies the doctoral doctor.

With this, the researchers were able to quantify the health of the forest by analyzing the sounds with a network theory approach. Through the noises captured it was possible to verify and understand the relationship between the level of impact and the community of species, without requiring them to be identified.

In addition, they also found that repeatedly burned forests had less biodiversity than those were felled only once.With each additional forest fire, the soundscape becomes quieter. But when knocked down once, the forest's soundscape demonstrates the ability to recover animal diversity.

Dataset

To find out where to place the recorders and how to interpret the diversity of soundscapes, measurements provided by Light Detection and Ranging (Lidar) made between 2013 and 2016 were required, and the last 33 years of Landsat satellite records.

With this, scientists have created a timeline of amazon forest cover over the past three decades and used the history of forest degradation to determine where to place the recorders.

Rappaport and his team hope the work will open a new understanding of the threats to Amazonian biodiversity. "I'm fascinated by what we still have to learn," says Doug Morton, an Earth scientist at NASA's Goddard Center and Rappaport's phD advisor.

Source: Um só Planeta